Energy &Environmental Science

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aDepartment of Chemistry, Shanghai Key

Innovative Materials, Advanced Materials

200433, P. R. China. E-mail: dyzhao@fu

+86-21-51630205bDepartment of Chemical Engineering, M

AustraliacCollege of Environmental Science and Engin

Control and Resource Reuse, Tongji UniversdChemistry Department and The Center of Ex

King Abdulaziz University, P.O. Box 80203,

† Electronic supplementary informa10.1039/c3ee41775a

Cite this: Energy Environ. Sci., 2013, 6,2765

Received 23rd May 2013Accepted 8th July 2013

DOI: 10.1039/c3ee41775a

www.rsc.org/ees

This journal is ª The Royal Society of

Ordered mesoporous carbons and their correspondingcolumn for highly efficient removal of microcystin-LR†

Wei Teng,a Zhangxiong Wu,b Jianwei Fan,ca Hong Chen,a Dan Feng,a Yingying Lv,a

Jinxiu Wang,a Abdullah M. Asirid and Dongyuan Zhao*ab

Highly effective removal of toxic pollutant microcystins from water sources is achieved by employing

ordered mesoporous carbons prepared from the surfactant-templating method as adsorbents. For the

first time, a systematic study into the static and dynamic adsorption behaviours of ordered mesoporous

carbons towards microcystin-LR (MC-LR) is demonstrated. Firstly, by adopting different mesoporous

carbons with various mesostructures, textures and surface chemical properties for batch adsorption,

definite relationships between the adsorption performance of MC-LR and properties of adsorbents are

established. Among all the samples, the mesoporous carbon (MCS/C) obtained from a mesoporous

silica–carbon composite after removing the silica component exhibits an unprecedented adsorption

capacity of �526 mg g�1, due to its unique bimodal mesopores of �2.8 and 5.8 nm, a high surface area

of 1680 m2 g�1, a large pore volume of 1.67 cm3 g�1 and two-dimensional (2D) straight mesopore

channels. A comprehensive understanding of dynamic adsorption behaviour shows that this

mesoporous carbon possesses a 30-fold higher adsorption capacity compared with powdery activated

carbon at a high flux of 120 L m�2 h�1. Finally, two pollutants, Rhodamine B and phenol, are mixed

with MC-LR for competitive adsorption onto the mesoporous carbon MCS/C. It is found that the total

amount of removal pollutants increases sharply to �700 mg g�1. Considering all the advantages, the

ordered mesoporous carbon MCS/C shows a promising potential for practical waste water treatment,

especially for large toxin microcystin removal.

Broader context

Microcystin-LR (MC-LR), produced by cyanobacteria from blue algae, is threatening human health and the environment due to its acute and irreversible damageon liver. However, this large molecular toxin is stable and difficult to remove from water sources by traditional technologies. In this article, mesoporous carbonmaterials are adopted as adsorbents for the effective removal of MCs. A comprehensive study into the static, dynamic and competitive adsorption behaviours of aseries of ordered mesoporous carbon adsorbents toward MC-LR has been delivered for the rst time, with clear relationships between the properties ofadsorbents and the adsorption performance established. Large pore size (5.8 nm), high mesopore surface area (1680 m2 g�1), large pore volume (1.67 cm3 g�1),straight pore channels (p6mm) and hydrophobic surfaces of adsorbents are benecial to remove MC-LR. A highly interconnected bimodal mesoporous carbonadsorbent possessing the above properties exhibits an excellent adsorption performance with a capacity of 526 mg g�1 for MC-LR, which is better than any otherresults in previous reports including powdery activated carbon. Moreover, it shows fast adsorption kinetics, excellent performance for the dynamic removal ofMC-LR under high ux and abruptly increased adsorption capacity in competitive adsorption. The adsorbent can also be reused over three consecutive cycles,retaining an unchanged adsorption capacity.

Laboratory of Molecular Catalysis and

Laboratory, Fudan University, Shanghai

dan.edu.cn; Fax: +86-21-51630307; Tel:

onash University, Clayton, VIC 3800,

eering, State Key Laboratory of Pollution

ity, Shanghai 200092, P. R. China

cellence for Advanced Materials Research,

Jeddah 21589, Saudi Arabia

tion (ESI) available. See DOI:

Chemistry 2013

1 Introduction

The increasing frequency and intensity of cyanobacteria bloomsin eutrophic lakes, rivers and water reservoirs present growingthreats to potable water sources.1–4 Microcystins (MCs)produced from cyanobacteria are monocyclic heptapeptides.There are over 70 types of variants of microcystins due to twovariable amino acids.5 Among them, microcystin-LR (MC-LR)with leucine and arginine residues is the most abundant andcommonly detected toxin (Fig. S1†),6 which is of great concernfor its adverse effects on both acute and chronic liver damage toanimals and humans.7 Therefore, removal of MC-LR from

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polluted water is much required. However, MC-LR is highlystable in the environment and difficult to remove because of itsspecial cyclic structure as well as its molecular size of 1.9 �1.1 � 1.5 nm3.8,9 It is a considerable challenge to develop anefficient method to remove MC-LR from water to solve thecritical water pollution problem associated with microcystins.

Adsorption-based processes, as simple and effective tech-niques for the removal of contaminants, have attractedconsiderable attention in water treatment.10–14 Adsorbents suchas zeolites,15 clays16 and activated carbons17 (ACs) have beenwidely used. Particularly, commercial powdery ACs (PACs) withhuge surface areas are extensively applied due to their highefficiencies for the removal of pollutants.18,19 However, theirsmall micropore sizes (<2 nm) dramatically limit their capa-bilities for the removal of large-sized molecules such as toxicMC-LR. Previous reports demonstrated that most microporesare inaccessible and useless, while only ACs with a highproportion of mesopores showed a large adsorption amounttoward MC-LR.19,20 On the other hand, too large pores such asmacropores are also incapable of adsorption due to decreasedsurface area and adsorption potential induced by pore walls,leading to a low density of adsorption sites and weak adsorptioninteractions. Therefore, a matched size between the pores of anadsorbent and the molecular dimension of a pollutant is crit-ical. Another problem comes from irregular pore channels witha wide pore size distribution.21 Because an accurate adjustmentof pore structure and size is difficult to achieve for traditionaladsorbents, the correlations between material properties, suchas pore structure and size, surface area and chemistry, andadsorption performance towards MC-LR have not been revealedclearly.22,23 Besides, most adsorption tests of MC-LR were con-ducted under static batch conditions, and limited studies haverevealed its dynamic adsorption performance and competitiveadsorption against other adsorbates in waste water. Suchdynamic or competitive adsorption data are critical and essen-tial to develop key adsorbents for possible practical applica-tions.24 Therefore, a prospective adsorbent for the systematicstudy of adsorption behaviour towards MC-LR should beadjusted with well-dened structural and textural propertiesover a wide range for the study of correlations between prop-erties of adsorbents and their adsorption performances,affluent adsorption sites and strong surface affinity for large-sized MC-LR adsorption.

Ordered mesoporous carbons (OMCs) are promising adsor-bents for pollutants with large molecular sizes because of theirunique interconnected mesostructures, uniform and large poresizes (2–50 nm), and high surface areas and pore volumes,showing advantages in high adsorption capacity and improvedkinetics by fast mass transformation.25–28 Recently, variousOMCs with different mesostructures and pore sizes have beendeveloped via a direct self-assembly method, which is simpleand feasible for large-scale production,29,30 such as FDU-15,31

FDU-16,32 andMCS/C,33 which is a mesoporous carbon obtainedfrom carbon–silica composites aer etching the silica compo-nent. Meanwhile, OMCs are very stable in water due to theirsolid carbonaceous frameworks and chemical inertness.Therefore, OMCs are suitable candidates for comprehensive

2766 | Energy Environ. Sci., 2013, 6, 2765–2776

studies into MC-LR adsorption. However, such adsorbents arepowdery. In dynamic adsorption tests, the adsorbent should beformed with high mechanical strength in owing streams.Column ltration based on a powdery adsorbent ller is adesirable and reasonable route due to its easy operation.34 WithOMCs as llers, the inuences of their intrinsic advantages,such as large pore sizes, high surface areas and interconnectedpore channels on dynamic adsorption capacity and the rate ofMC-LR can clearly be revealed. On the other hand, in view of theeffects of external factors on adsorption processes, competitivemolecules are necessary to be introduced to clarify the occu-pancy of adsorbates with various properties in the mesoporechannels or adsorption sites.35 In general, although OMCs havebeen reported to exhibit good adsorption properties forpollutants,4,25,27,39–41 a comprehensive and systemic study intothe inuences of the various physicochemical properties ofmesoporous carbons on the static and dynamic adsorption ofMC-LR has not been revealed before. Furthermore, based onunderstanding such relationships, a reasonable evaluation ofthe potential of a designed adsorbent is greatly required forpractical applications.

Herein, a systemically detailed investigation into the staticand dynamic adsorption performances of a series of orderedmesoporous carbons towards MC-LR has been explored for therst time. Four types of OMCs with various mesostructures,pore sizes/volumes, surface areas and surface properties aresynthesized precisely by using Pluronic F127 as a structure-directing agent and phenolic resin as a carbon precursor.Through static adsorption tests, denite relationships betweenthe properties of adsorbents and adsorption performance areclaried. The sample MCS/C with a high surface area (�1680 m2

g�1), a large pore volume (�1.67 cm3 g�1) and bimodal pores(�2.8 and 5.8 nm) shows an excellent performance of 526 mgg�1 for MC-LR, which is much higher than that of any otheradsorbents reported previously. It is therefore employed for acomprehensive dynamic adsorption study. The column lledwith the mesoporous carbon MCS/C possessed a high adsorp-tion capacity, which is 30 times higher than that of a PAC at ahigh ux of 120 L m�2 h�1. Moreover, the sample MCS/C can beeasily regenerated without performance deterioration over threeconsecutive cycles. Furthermore, competitive adsorption of MC-LR against Rhodamine B (RhB) and phenol on the MCS/Cadsorbent is evaluated to simulate real waste water. It is foundthat a competitive adsorbate with different molecular sizes andchemical properties impacts the adsorption amount of MC-LR,but the total amount of adsorbed/removed pollutants increases.

2 Experimental2.1 Chemicals and carbon materials

Triblock copolymer Pluronic F127 (Mw ¼ 12 600, PEO106PPO70-PEO106) was purchased from Acros Corp. Tetraethoxysilane(TEOS), phenol, formaldehyde solution (37 wt%), hydrochloricacid (HCl), sodium hydroxide (NaOH), ammonium persulfate[(NH4)2S2O8, APS], sulfuric acid (H2SO4) and ethanol werepurchased from Shanghai Chemical Corp. All chemicals wereused as received without any further purication. Microcystin-LR

This journal is ª The Royal Society of Chemistry 2013

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(MC-LR, purity >95%) was purchased from Express TechnologyCo., Ltd. Triuoro-acetic acid (TFA, 99% HPLC grade) andmethanol (HPLC grade) were purchased from Merck Corp.Deionized water with a resistance >18.2 MU cm�1 was obtainedby passing tap water through a Milli-Q system. Commercial PACwas supplied by the Xinzhuang Activated Carbon Company ofShanghai. Its physicochemical properties are listed in Table 1.Three distinct mesoporous carbons, including FDU-15,31 FDU-1632 and MCS/C33 were synthesized by using F127 as a structure-directing agent and phenolic resin as a carbon precursoraccording to previous reports. The detailed synthesis procedureswere provided in the ESI.† The as-made mesoporous carbonFDU-15 was carbonized at three different temperatures, namely,350, 600 and 900 �C, to produce a series of FDU-15-x (x refers toas carbonization temperature) with different properties. Thesurface-oxidized mesoporous carbon MCS/C-APS36 was preparedby treating its parent mesoporous carbon MCS/C under a wetoxidation condition with acidic APS solution.

2.2 Fabrication of carbonaceous column

Carbon adsorbents were grinded and then sieved through 500and 700 mesh screens in sequence to get particles of uniformdiameter. Aer drying overnight, uniform particles of �5.0 mgwere packed tightly to a Teon column with a diameter of4.5 mm and a length of 1.9–2.0 mm. A lter (cellulose acetatemembrane) with a size of �0.22 mm was xed at the end of thewater outlet in the column.

2.3 Batch adsorption

Batch adsorption experiments were conducted to assess theadsorption behaviour under static conditions. Typically, 0.2 mgof carbon adsorbents was dispersed in 20 mL of water withultrasound for 0.5 min to get a homogeneous suspension in a100 mL ask. MC-LR was added to make an initial concentra-tion of 2, 5 or 10 mg L�1. Then the ask was sealed and agitatedat 200 rpm in a thermo-stated rotary shaker at 25 �C. Aer 4 h,0.5 mL of the remaining solution was taken out, ltered througha lter (cellulose acetate membrane) with the size of 0.22 mm toremove the adsorbent, and then the residual MC-LR concen-tration was measured by high performance liquid chromatog-raphy (HPLC). Adsorption kinetic experiments were performedin the same conditions but with double dose as above. The MC-LR concentration was measured at each predetermined timepoint. The adsorption isotherms were obtained by testing theadsorption capacities of the same amount of adsorbent toward

Table 1 Structural, textural parameters and surface charges of various carbon ads

Sample SBET (m2 g�1) SMea (m2 g�1)

MCS/C 1680 1680FDU-15-900 920 380PAC 1990 350

a The mesopore surface areas were calculated by total surface areas minusthe BET method using adsorption data at a relative pressure (p/p0) of 0.method. b Zeta potential was measured at pH 7 in KCl solution.

This journal is ª The Royal Society of Chemistry 2013

MC-LR solutions with a series of initial concentrations aerequilibrium (a contact time of 4 h). In competitive adsorptiontests, an identical molar amount of RhB or phenol to MC-LRwas mixed with an initial MC-LR solution. The adsorption wasallowed to achieve equilibrium, followed by determination ofthe remaining concentrations of RhB (or phenol) and MC-LR.

2.4 Adsorption calculation and model

The adsorbed percentage (P) of MC-LR at time (t) was calculatedusing eqn (1), where C0 and Ct are the initial solution concen-tration and the concentration at time t (mg L�1), respectively.The adsorbed amount was calculated using eqn (2), where Ce isthe equilibrium concentration (mg L�1), W is the mass ofadsorbents (g), V is the volume of the solution (L) and Qe is theequilibrium adsorption capacity (mg g�1). By plotting Qe vs Ce,the adsorption isotherms were obtained. The Langmuir model(eqn (3)) was used to t the non-linear isotherms, where Qmax

represents the saturated adsorption capacity (mg g�1) and KL isthe Langmuir equilibrium constant (L g�1) which is a measureof the adsorption affinity.

P ¼ ðC0 � CtÞC0

� 100% (1)

Qe ¼ ðC0 � CeÞ � V

W(2)

Qe ¼ QmaxKLCe

1þ KLCe

(3)

2.5 Dynamic adsorption

The carbon column ltration unit was washed and equilibratedwith deionized water before the dynamic adsorption experi-ments. A blank experiment was carried out rst to evaluate theadsorption effect of the whole ow path but without packingany adsorbents. There was nearly no obvious change in theconcentration of MC-LR detected at inlet and outlet (Fig. S2†),and thus the whole adsorption could be attributed to theadsorbent lled in the column.

MC-LR feed solution with an initial concentration of 10 mgL�1 was continuously pumped to lter through the column atdifferent constant ow rates (0.25 or 1.0 mL min�1) at roomtemperature. The effluents from the column outlet wereconsecutively collected at intervals of 4 min and the corre-sponding MC-LR concentrations were analysed by HPLC. Forthe column regeneration, aer an adsorption circle with 30 mL

orbents

D (nm) Vt (cm3 g�1) Zeta potential (mV)b

2.8, 5.8 1.67 �284.6 0.68 �26<2 1.03 �35

micropore surface areas, while the total surface areas were obtained by04–0.2 and micropore surface areas were calculated through the t-plot

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MC-LR feed solution (10 mg L�1) at 0.25 mL min�1, 20 mL ofmethanol and then 10 mL of deionized water were sequentiallypassed through the column to elute the MC-LR and then washout methanol residues. The same cycle was repeated in threeconsecutive runs to study the capacity of regeneration.

2.6 Characterization and measurements

Small-angle X-ray scattering (SAXS) measurements were takenon a Nanostar U small-angle X-ray scattering system (Bruker,Germany) with Cu Ka radiation (40 kV, 35 mA). Transmissionelectron microscopy (TEM) images were taken by a JEOLJEM2011F microscope (Japan) operated at 200 kV. The samplesfor TEM measurements were suspended in ethanol and drop-ped onto holey carbon lms supported on a Cu grid. High-resolution scanning electron microscopy (HRSEM) images wereobtained from a Hitachi S-4800 ultrahigh resolution SEMoperating at 1 kV. Nitrogen adsorption/desorption isothermswere measured with a Micromeritics Tristar 3020 analyzer (USA)at �196 �C. Before the measurements, samples were degassedin vacuo at 200 �C for at least 6 h. The BET method was used tocalculate the specic surface areas (SBET) using adsorption dataat p/p0 of 0.04–0.2. The pore size distributions (PSDs) werederived from the adsorption branches of isotherms by using theBJH model. The total pore volume (Vt) was estimated from theadsorbed amount at p/p0 of 0.995. Fourier transform infrared(FTIR) spectra were measured on a Nicolet Fourier spectro-photometer from 4000 to 400 cm�1 using KBr pellets of the solidsamples. The Zeta-potential was recorded by using a ZEN 3600,Malvern Instruments. Different powdery materials weredispersed in 10 mL of deionized water with ultrasound for 0.5min to keep the same concentration of adsorbents as that ofadsorption tests. 0.1 M NaCl was added to maintain a highbackground-electrolyte concentration. Analysis of MC-LR wasperformed onHPLC (LC-10AT, Shimadzu, Tokyo, Japan) with anultraviolet (UV) detector (Model 2478). The detection wascarried out using a symmetry C18 column (Shim-pack VP-ODS,4.6 � 150 mm2, i.d. 5 mm) at 40 �C. The mobile phase was amixture of methanol–water (60 : 40) containing 0.1% of TFA(v/v) with 0.8 mL min�1

ow rate. The injection volume was50 mL with the wavelength of UV detection at 238 nm for thetypical MCs spectra. The concentrations of RhB and phenol inaqueous solution were measured by a Shimadzu UV-3150adsorption spectrometer at 554 and 270 nm.

3 Results and discussion3.1 Characteristics of the adsorbents

A series of mesoporous carbon adsorbents with different porestructures and sizes, porosities, and surface chemical proper-ties were prepared through the surfactant self-assemblingapproach by using triblock copolymer Pluronic F127 as atemplate and preformed phenolic resins as carbon sources. Theordered mesoporous carbonMCS/C was achieved by etching thesilica component from a mesoporous silica–carbon composite,which could be obtained from a tri-constituent co-assemblyprocess of silica oligomer precursors, phenolic resols, and

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Pluronic F127 in the initial ethanolic solution, and thencarbonized at 900 �C.33 Its SAXS pattern (Fig. 1A-a) shows fourwell-resolved scattering peaks that can be indexed to the 10, 11,20 and 21 diffractions of a highly ordered two-dimensional (2D)hexagonal mesostructure. Aer being treated with an acidic APSsolution at 30 �C for 6 h, the SAXS pattern (Fig. S3a†) of themesoporous MCS/C-APS with a high concentration of surfaceoxides becomes a little less-resolved, indicating that the orderedarray of mesopores is deteriorated to some extent and itsframework may be partially etched. The ordered mesoporousFUD-15-x materials, either in a polymer or carbon form, weresynthesized via the same self-assembly method as abovewithout silica sources added.32 They possess the same meso-structure as that of the sample MCS/C, but have much smallercell parameters as illustrated by the right-shied scatteringpeak positions in SAXS patterns (Fig. 1A-b and S3b and c†). Asthe carbonization temperature increases from 350 to 900 �C, thescattering peaks shi to higher q values, implying gradualshrinkage of the carbon frameworks. Completely different fromMCS/C and FDU-15 samples, the mesoporous carbon FDU-16-600, synthesized by using similar method as FDU-15 andcarbonized at 600 �C, has a body-centered cubic mesostructurewith a space group of Im3m symmetry as indicated by its SAXSpattern (Fig. S3d†).

In accordance with the SAXS results, TEM images showhexagonally arranged mesopores in the carbon sample MSC/C(Fig. 1B), stripe-like ordered mesopores in the mesoporouscarbon FDU-15-900 (Fig. 1C), and two characteristic directions,namely, [100] and [110], for the body-centred cubic mesostruc-ture in the carbon sample FDU-16-600 (Fig. S4a and b†).Furthermore, HRSEM images (Fig. S4c–f†) exhibit orderedmesostructures in large domains with fully open pore channelson the surfaces for all the mesoporous carbon materials MCS/C,FDU-15-900 and FDU-16-600.

The textural properties of the mesoporous carbon adsor-bents (FDU-15-350 is a polymer material) were analyzed in detail(Fig. S5,† Table 1 and S1†). The ordered mesoporous carbonMCS/C shows typical type IV isotherms with two condensationsteps in the mesopore range (Fig. S5A-a†). Two uniform meso-pore size distributions centred at �2.8 and 5.8 nm are observed(Fig. S5B-a†). In this carbon material, the secondary mesopores(�2.8 nm) interpenetrate the whole carbon framework andconnect the primary mesopores (�5.8 nm). Because of theunique bimodal mesopores, it has a very high surface area of�1680 m2 g�1 and a large pore volume of �1.67 cm3 g�1.Importantly, 80% of its surface area arises from the secondarymesopores on the basis of the t-plot analysis. However, aer thesurface oxidation of the carbon sample MCS/C, the surface areaand pore volume of the resultant MCS/C-APS sample decline to1290 m2 g�1 and 0.96 cm3 g�1, respectively. The secondary andprimary pore sizes also decrease to 2.3 and 4.9 nm, respectively,which may be attributed to the blockage of the functionalorganic groups and the damage of pores during the treatment.For the orderedmesoporous carbon FDU-15, we take the sampleFDU-15-900 as a representative. It shows similar N2 sorptionisotherms as that of the sample MCS/C, but with only onecondensation step in the mesopore range (Fig. S5A-b†),

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Fig. 1 SAXS patterns (A) of the mesoporous carbon prepared by surfactant-templating approach using Pluronic F127 as a structure-directing agent and phenolic resinas a carbon precursor: (a) mesoporous carbon (MCS/C) derived from the mesoporous silica–carbon composites after etching silica component by using HF solution and(b) 2D hexagonal mesoporous carbon (FDU-15-900); and TEM images of the mesoporous carbon MCS/C viewed along the pore channels (B) and FDU-15-900 viewedperpendicular to the pore channels (C).

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indicative of uniform mesopores. It has a BET surface area of�920 m2 g�1, a pore volume of �0.68 cm3 g�1 and a uniformpore size distribution centred at �4.6 nm (Fig. S5B-b†).Noticeably, 58% of its surface area and 37% of its pore volumecome from the micropores. For the FDU-15-x series, as thecarbonization temperature increases from 350 to 900 �C, thesurface areas and pore volumes increase, due to the generationof more and more micropores since the surface areas from themesopores almost keep constant (Fig. S5C and D, Table S1†).However, the pore sizes decrease from 5.2 to 4.7 nm due tostructural shrinkage. For the carbon sample FDU-16-600 with abody-centered cubic mesostructure, it has a similar texturalproperty as that of FUD-15-600 with a total surface area of�690 m2 g�1, a mesoporous surface area of �290 m2 g�1 and apore diameter of 4.8 nm (Fig. S5C-d, D-d and Table S1†).Distinctly, N2 sorption isotherms of the powdery active carbon(PAC) are quite different from those of the mesoporous carbonsamples, which have a sharply increased adsorption amount at arelative pressure (P/P0) below 0.1, followed by an adsorptionplateau at higher relative pressure values (Fig. S5A-c†), suggest-ing that the porosity of PAC is dominated by micropores (<2 nm)(Fig. S5B-c†). Nevertheless, it possesses a very high surface areaof �1990 cm3 g�1 and a large pore volume of �1.03 cm3 g�1

(Table 1), which is predominantly caused by the nemicropores.The FTIR spectra (Fig. S6A-a and b†) of the mesoporous

carbons FDU-15-900 and MCS/C are similar due to the samecarbon source (phenolic resin) and carbonization temperature(900 �C). The wide band at 3450 cm�1 is mostly contributed tothe O–H stretching vibrations of the adsorbed water molecules.The weak bands at around 1636, 1559 and 1405 cm�1 arecharacteristic for carbonmaterials, and are probably ascribed tothe C]C groups in the surface aromatic structures, and thesmall amounts of quinine C]O and C–H groups conjugated inthe graphene layers.37 There is a difference in the FTIR spectrumof PAC (Fig. S6A-c†). The broad and intense band at 1090 cm�1

is attributed to the C–O vibration of acid anhydride and/or C–Nfrom nitrogen-containing groups or pyridine. Compared to themesoporous carbon FDU-15-900, the FTIR spectrum (Fig. S6B-a†) of FDU-15-350 shows an excess band at 1720 cm�1 caused bythe vibration of tetra-substituted benzene rings, suggesting aframework of highly cross-linked phenolic resins with lower

This journal is ª The Royal Society of Chemistry 2013

carbon content.38 Extra bands at 1228 and 1005 cm�1 can beassigned to the C–O bonds from phenol, indicating the exis-tence of oxygen groups. Therefore, it can be concluded that asthe carbonization temperature increases from 350 to 900 �C, thephenolic frameworks of the mesoporous carbons FDU-15 aretransformed to carbon ones gradually, and with gradual elimi-nation of oxygen-contenting groups, the framework surfacesbecome more hydrophobic. For the surface-oxidised sampleMCS/C-APS (Fig. S6B-c†), two new intense bands at 1721 and1250 cm�1 appear, which are attributed to the C]O of carboxylgroups and C–O bonds, implying that many surface oxides aregenerated.36

Zeta-potential measurement results (Table 1) show that allthe carbon adsorbents MCS/C, FDU-15-900 and PAC haveoverall negative surface charges at a pH value of �7. There arestill tiny differences between them. The zeta-potential values ofthe mesoporous carbon MCS/C and FDU-15-900 are very closedue to their coherent surface properties, but there is a lowervalue for PAC because of its negative charged hydrophilicgroups on the surface, such as oxygen-containing groups, whichis in agreement with the results of FTIR analysis.

3.2 Batch adsorption

First, the effect of mesostructure is exhibited by using meso-porous carbon FDU-15-600 and its counterpart FDU-16-600 asrepresentatives due to their similar textual and surface chemicalproperties except the mesostructure (Table S1 and Fig. S3†). Themesoporous carbon FDU-15-600 with 2D hexagonal straightpore channels shows a signicantly higher adsorption capacity(�23.8 mg g�1) than that (�14.8 mg g�1) of FDU-16-600 with 3Dbody-centered cubic mesopores (Fig. 2a), which is also consis-tent with the results from mesoporous silica materials withdifferent mesostructures as adsorbents.42 Following such aresult, the 2D hexagonal mesostructured FDU-15-x seriesobtained by carbonization from 350 to 900 �C are adopted forfurther comparison with closer mesopore surface areas.Notably, the adsorption capacity increases greatly from 22.1 to57.3 mg g�1, suggesting that the changes of surface propertiesand total surface areas/pore volumes caused by high carbon-ization temperature (900 �C) have more obvious inuences than

Energy Environ. Sci., 2013, 6, 2765–2776 | 2769

Fig. 2 Amount/percentage of MC-LR adsorption from water on (a) the meso-porous carbon adsorbents with different mesostructure FDU-15-600 (2D hexag-onal, space group p6mm) and FDU-16-600 (3D cubic, Fm3m); (b) FDU-15 atdifferent carbonization temperatures of 350, 600 and 900 �C (FDU-15-350, -600and -900) and (c) the mesoporous MCS/C obtained from the mesoporous silica–carbon composites by etching silica component before and after acidic APSsolution treatment (MCS/C-APS). Initial concentration is (a) 2 mg L�1 and (b and c)10 mg L�1.

Fig. 3 The removal percentage of MC-LR versus contact time on the adsorbents:the mesoporous carbon MCS/C prepared from the mesoporous silica–carboncomposite after etching silica component (a), the mesoporous carbon FDU-15-900 (b) and the commercial PAC (c) with an initial concentration of 2 mg L�1 inMilli-Q water.

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pore size at a range of 4.7 to 5.2 nm (Fig. 2b). Finally, the carbonadsorbent MCS/C shows a remarkably high adsorption capacityof 270 mg g�1, much higher than FDU-15-900 with the samemesostructure, which can be attributed to its completelydifferent bimodal mesopores. Moreover, there is a dramaticdecrease of the adsorption amount from 270 to 142 mg g�1

when the mesoporous carbon MCS/C is treated by acidic APSsolution to MCS/C-APS (Fig. 2c).

Based on the above results, the typical mesoporous carbonsamples FDU-15-900 and MCS/C (carbonized at 900 �C without

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any further treatment) are chosen for the further systemic andcomprehensive studies. The adsorption rates of MC-LR on theselectedmesoporous carbonmaterials (MCS/C and FDU-15-900)were evaluated by adsorption kinetic tests (Fig. 3). Thefrequently-used and commercial adsorbent in water treatment,PAC was adopted here for comparison. The results show thatthe removal percentage of MC-LR by all these carbon adsor-bents rockets at the initial period of around 10–15 min, indi-cating very fast adsorption processes. The difference is that theadsorption equilibrium is achieved at about 50 min for themesoporous carbon FUD-15 and the microporous PAC, but forthe carbon sample MCS/C, the amount of adsorption in the rst15 min can reach 58% of the nal capacity, and the adsorptionequilibrium is achieved within 2 h. Meanwhile, it can beobserved obviously that the carbon sample MCS/C possesses thehighest removal percentage (�97%) for MC-LR, while only 40and 35% can be removed by the sample FDU-15-900 and PAC,respectively.

The equilibrium adsorption isotherms of MC-LR ontovarious carbon adsorbents show type I curves (Fig. 4A). Theexperimental data of the samples FDU-15-900 and PAC can bewell tted to the Langmuir adsorption isotherm with high R2

values approaching 1 (Fig. 4B and Table 2). However, the R2

value of the sample MCS/C is only 0.948, the farthest to 1,implying that instead of one layer, multi-layer adsorption couldoccur on its surface. The maximum saturated adsorptioncapacities calculated by the Langmuir adsorption model are�526, 87.0 and 64.5 mg g�1 for the carbon samples MCS/C,FDU-15-900 and PAC, respectively (Table 2). The adsorptioncapacity of the carbon sample MCS/C is extremely large, nearly10 times higher than that of PAC. Such an adsorption perfor-mance for MC-LR is unprecedented, which is much higher thanthose of other adsorbents reported in previous studies (TableS2†). This excellent performance of the ordered mesoporous

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Fig. 4 Adsorption isotherms (A) and the corresponding linear Langmuir modeling curves (B) of the carbon adsorbents: the mesoporous carbon MCS/C obtained fromthe silica–carbon composites after etching the silica component (a), 2D hexagonal mesoporous carbon FDU-15-900 (b), and the commercial PAC (c) toward MC-LR.

Table 2 Langmuir isotherm constants for MC-LR adsorption on various carbonadsorbents

Adsorbents Qm (mg g�1) KL (L g�1) R2

MSC/C 526 0.22 0.9480FDU-15-900 87 2.15 0.9989PAC 64.5 2.67 0.9773

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carbon MCS/C predicts a promising actual application for theremoval of toxic MC-LR.

The elaborate inuences of pore structure, and textual andsurface chemical properties are attributed as being the cause ofthe extremely large adsorption capacity of MC-LR on the mes-oporous carbon MCS/C. For different mesostructures, the 2Dhexagonal straight pore channels are better than the 3D body-centered cubic pores. The reason lies in the following aspects.Firstly, the molecular shape of MC-LR is close to linear, which ismuch better matched to the straight mesochannels of FDU-15-600 as compared to the cubic spherical pore arrays in FDU-16-600 (Fig. S7a†). Therefore, MC-LR molecules can be much moreclosely packed in the mesopores of FDU-15-600 than in those ofFDU-16-600, thus, the adsorption capacity of the former is muchhigher. Secondly, as compared to the spherical cubic mesoporesconnecting with small pore windows in FDU-16-600, the 2Dhexagonal straight mesopores of FDU-15-600 can supply morefacile channels for transferring the large-sized MC-LR mole-cules deep into the inner parts of the mesopores with much lessdiffusion resistance (Fig. S7b†). The curvature of the cubicmesopore walls may bring about resistance for moleculardiffusion. Moreover, the small pore windows of the body-centered cubic mesopores in FDU-16-600 can also limit molec-ular diffusion, and even more, the whole pore cavity may bepartially blocked aer the pore windows are occupied by MC-LRmolecules. Therefore, the utilization of the mesopores tends tobe higher in FDU-15 than that in FDU-16. Analogically, for thesame mesostructured MCS/C, its 2D hexagonal straight andopen channels in primary mesopores are favourable foradsorption of MC-LR.

The inuence of pore size can be illustrated by comparingthe micropore (<2 nm) and mesopore (>2.8 nm) in the samples

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of PAC, FDU-15-900 and MCS/C. Although PAC possesses ahigher surface area than that of MCS/C, the majority of itsporosity is from micropores, which is responsible for the verylow saturated adsorption, because the large MC-LR moleculeshave enormous diffusion resistance into the ne micropores. Italso can be inferred that the micropores in FDU-15-900 aremostly not utilized for its low adsorption capacity and the samerapid single-step adsorption stage as PAC, implying no furtherdiffusion into the micropores (Fig. 3). Consequently, micro-pores are too small to host the large molecule MC-LR, but themesopore is accessible. Thus, bimodal mesopores with largepore sizes (2.8 and 5.8 nm) in the carbon sample MCS/C facil-itate the excellent adsorption performance.

The surface area is another important factor. The decrease ofadsorption amount when the mesoporous carbon sample MCS/C is treated to MCS/C-APS partly contributed to the decline ofsurface area from 1600 to 1290 m2 g�1. Compared with MCS/C,the sample FDU-15-900, with much lower surface area, cannotprovide more accommodations for MC-LR and thus has a loweradsorption amount. However, the carbon PAC has the highestsurface area among all carbon adsorbents and exhibits a rela-tively low adsorption performance. This indicates that thebenecial factor is the proportion of the mesopore surface areabut not the total surface area. Therefore, the extremely highmesopore surface area of the MCS/C supplies an excellentcondition for MC-LR removal.

The surface chemical property also seriously impacts theadsorption ability of MC-LR. For the FDU-15-x series carbonsamples, the adsorption performance becomes better andbetter as the carbonization temperature increases. Because theincrease of total surface areas/pore volumes is mainly generatedfrom micropores, it can be mainly ascribed to the inuence ofsurface chemistry. As the carbonization temperature increases,the oxygen-containing groups of FDU-15 are gradually elimi-nated and aromatic carbon frameworks gradually develop withthe materials becoming more and more hydrophobic. Likewise,MC-LR is more inclined to be hydrophobic because of itshydrophobic leucine units at variable amino acid positions.43

Therefore, the MC-LR molecules tend to accumulate on thehydrophobic surface. Meanwhile, MC-LR is a monocyclic hep-tapeptide with a benzene ring in ADDA amino acid (Fig. S1†),which makes it possible to be captured on the surface of

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adsorbents with aromatic rings by p–p stacking interactions.Therefore, a higher carbonization temperature produces abetter carbon adsorbent for MC-LR (Fig. S8b†). In addition, thehydrophilic surface is a partial reason for the low adsorptioncapacity on MCS/C-APS, judging by only a 20% decrease insurface area but a 47% reduction in the adsorption amount ofMC-LR compared with MCS/C. More oxygen-containing groupfunctionalization makes the surface more hydrophilic, leadingto a lower performance than that of MCS/C carbonized at900 �C. Moreover, the oxidized surface brings more negativecharges to the material, which is another disadvantage for MC-LR adsorption due to repulsion between similar charges(Fig. S8c†). Therefore, the hydrophobic surface of the meso-porous carbon MCS/C, treated at higher temperature (900 �C),accounts for its large adsorption performance and the meso-porous carbon modied with a positive charge around thesurface is a possible orientation for the improvement ofadsorption in our future work.

3.3 Dynamic adsorption of MC-LR

The representative mesoporous carbon sample MCS/C wasfurther used as a kind of ller in a column to test the dynamicadsorption behaviour of MC-LR. The commercial PAC with ahigh surface area was also employed as a ller material forcontrast, keeping the same mass and length of column as llerMCS/C. The scheme and the optical photograph of the columnunit (Fig. 5A and B) show the designed process and theassembled macroscopic device. The breakthrough curve(Fig. 5C-a) of MC-LR solution (10 mg L�1) passing through theMCS/C column at a constant ow rate of 0.25 mL min�1 showsan excellent dynamic adsorption behaviour with a very lowconcentration remaining at the outlet (<0.01 mg L�1, unde-tectable) until a total volume of 50 mL feed solution passedthrough the column. Then, the concentration of MC-LR solu-tion at the outlet gradually increases, implying that the nemesopores deep in the carbon particles of the column llerMCS/C are penetrated and lled with MC-LR molecules gradu-ally towards adsorption saturation. When the outlet concen-tration reaches 10% of the feed value, it is normally regarded asthe breakthrough point of a column in industry. At this point,about 153 mL of MC-LR feed solution has been ltrated throughthe MCS/C column, compared with only 5.2 mL on PAC column(intuitive volume comparison in Fig. 5B inset). Moreover, for thePAC column, there is a direct sharp increase in the outletconcentration at the rst stage without any visible platform of alow outlet concentration (Fig. 5C-b), clearly indicating rapidow through and adsorption on the outer surface and a smallamount of macropores but no utilization of the inner micro-pores. The dynamic adsorption capacity of the MCS/C column isabout 305 mg g�1 at 10% breakthrough point (Fig. 5C-c and d),which is 30 times higher than that (10 mg g�1) of the PACcolumn. Compared with PAC adsorbent, the mesoporouscarbon MCS/C with larger mesopore size/volume and highersurface area offers advantages in dynamic adsorption. There-fore, MCS/C adsorbents retain a higher adsorption amount thanthat of PAC.

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In dynamic conditions, the contact time, namely hydraulicretention time (HRT) is one of important factors. Differentuxes have been studied to estimate the inuence of HRT onthe adsorption ability of the MCS/C column. The breakthroughpoint (Fig. 5D) was reached much earlier (74 vs. 173 mL) and theoutlet concentration increases much faster when the ux raterises from 0.25 to 1mLmin�1, corresponding to 30 to 120 Lm�2

h�1. The adsorption ability of the MCS/C column is about143mg g�1 at 1 mLmin�1, which is lower than that (305mg g�1)at 0.25 mL min�1 but still much higher than that on the PACcolumn at a low ux. This phenomenon suggests that lesscontact time makes it more difficult for the adsorption process.More rapid transfer leads to insufficient diffusion and reducedutilization of the available mesopore channels for MC-LRmolecules, resulting in a lower adsorption performance. Like-wise, it can be inferred that with an increase of the length of thecolumn (prolonging the HRT), the breakthrough point isexpected to occur later or the amount of MC-LR adsorption canbe improved accordingly.

3.4 Regeneration of adsorbents

A continuous adsorption–desorption test for the cyclic stabilityof the column packed with the sample MCS/C was studied. Theadsorption/desorption curves (Fig. 5E) show that aer acomplete adsorption stage of 30 mL of feed with the effluenthaving undetectable MC-LR, the column can be regenerated byeluting with methanol (20 mL) and further washing with water(10 mL). Methanol was used to easily and completely elute theadsorptive MC-LR from the adsorbent MCS/C, and then thedeionized water was passed through the column to wash outthe residual methanol. It is observed that aer three reutiliza-tion and regeneration steps, the mesoporous carbon columncan still keep its original adsorption capacity for MC-LR. Theresults suggest that the mesoporous carbon MCS/C is a stableand efficient adsorbent for reusability.

3.5 Understanding the adsorption processes

The adsorption rate and status are totally different on carbonadsorbents with various properties in static and dynamicadsorption. The unique mesoporous carbon MCS/C adsorbentis composed of bimodal mesopores with the secondary meso-pores interpenetrating carbon walls and connecting primarymesopores. For static tests, it is supposed to undergo twokinetic stages (Scheme 1A-a). First, the open and straightprimary mesopores account for the initial fast adsorption stageof MC-LR with 58% of total MC-LR adsorbed on. Then, throughhydrophobic interactions and capillary forces, MC-LR mole-cules gradually diffuse into the connecting secondary meso-pores, which share 80% of the total surface area, prompting theremoval efficiency to increase from 58 to 97%. Given that bothof the bimodal mesopores are accessible for hosting MC-LRmolecules, an extremely high saturated adsorption capacity of526 mg g�1 for MC-LR has been achieved. Interestingly, about58% of the total adsorbed MC-LR molecules are located in theprimary mesopores which only account for 20% of the totalsurface area. It can be calculated that the surface occupancy rate

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Fig. 5 Illustration (A) and optical photograph (B) of the experimental unit for the dynamic adsorption and intuitive comparison of the treated amount of waste waterby the different carbon adsorbents: the mesoporous carbon MCS/C (left) and the commercial PAC (right). Breakthrough curves (C) for MC-LR solutions through thecarbon adsorbents MCS/C and PAC column, with a flow rate at 0.25 mLmin�1. Breakthrough curves (D) for MC-LR solutions through the mesoporous carbon adsorbentMCS/C column at different flow rates. Plots of the adsorption and desorption with permeation volumes (E) of MC-LR from solution through filtration, flow rate at0.25 mL min�1. All filtration tests were carried out with a feed concentration of 10 mg L�1 in Milli-Q water.

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is 155%, indicating that more than one layer of MC-LR mole-cules is adsorbed on the primary mesopores, which is inaccordance with the result of Langmuir simulation. Only about42% of MC-LR molecules are adsorbed in the secondary mes-opores in spite of their large contribution (80%) to the totalsurface area. This is because the smaller secondary mesopores(�2.8 nm) impose diffusion and/or steric limitation for packingMC-LR molecules so that the utilization of the pore volume isrelatively lower. Nevertheless, these unique bimodal mesoporesendow the carbon sample with a high capability for MC-LRremoval with excellent capacity and kinetic properties. Incontrast, the mesoporous carbon sample FDU-15-900, a typicalrepresentative of unimodal mesopores, has the same primarymesopore structure as that of MCS/C but the pore size is rela-tively smaller (4.6 vs. 5.8 nm) and particularly the secondaryconnecting pores are entirely micropores. As a result, thiscarbon sample gives only one kinetic stage with a very rapidadsorption, due to the existence of large primary mesopores,but the saturated adsorption (87 mg g�1) is much lower as

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compared to that adsorbed on the sample MSC/C due to therelatively smaller pore size, much lower surface area and porevolume. Almost all MC-LR molecules are considered to beadsorbed on the primary mesopores but not the micropores. Bycalculation, the surface occupancy rate is 39%, indicating thatthe adsorbedMC-LRmolecules are mainly regarded as one layeron the pore walls due to smaller diameter/volume of mesoporechannels (Scheme 1A-b). Although the PAC sample possesseshigher surface area than MCS/C and FDU-15-900, the majorityof its porosity is from micropores, which is responsible for thelowest saturated adsorption, because the large MC-LR mole-cules have enormous diffusion resistance into the ne micro-pores (Scheme 1A-c). Therefore, the adsorbed MC-LR moleculesmainly stay in a few macropores or mesopores. This indicatesthat the benecial factor is the proportion of the mesoporoussurface area but not the total surface area.

The MCS/C column exhibits a capacity that is 30 timeshigher than that of PAC for dynamic tests compared with a 10times higher capacity for static adsorption. This phenomenon is

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Scheme 1 Adsorption model illustration of MC-LR molecule status in static adsorption (A) and dynamic adsorption (B); and on various carbon adsorbents: (a) 2Dhexagonal (p6mm) mesoporous MCS/C with large bimodal mesopore structures, (b) the 2D hexagonal (p6mm) mesoporous carbon FDU-15-900 with unimodalmesopores and micropores on the carbon walls and (c) the commercial PAC with disordered small micropores, showing the process at different adsorption stagesbefore the adsorption, adsorption at the first kinetic stage, after static adsorption and dynamic adsorption.

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related to the pore structure and texture of these two llers orthe different contact times of static and dynamic adsorptiontests. In static adsorption, the spontaneous diffusion of MC-LRmolecules into pores is mainly driven by capillary forces step-by-step with continuous stirring. Enough contact time (4 h) causesthe achievement of an adsorption/desorption equilibrium onthe surface of pore channels. In dynamic experiments, becauseof a very short contact time, the status of adsorption equilib-rium is impossible to achieve. Owing to the bimodal mesoporesand their interconnectivity of the sample MCS/C, MC-LRmolecules are driven easier toward the primary mesopores, andthen diffuse into secondary or inner mesopores to keep acontinuous adsorption (Scheme 1B). But for PAC, most poresare too small, with an irregular and poorly interconnectedstructure. When the contact time is reduced, the MC-LR cannotenter or diffuse rapidly because of encountering rival forcesfrom the blockage of disconnected microporous roots, resultingin an inadequate adsorption of MC-LR in the outer pores.

3.6 Competitive adsorption

RhB was selected as a model adsorbate as it consists of posi-tively charged groups and aromatic systems with a similar

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molecular size as MC-LR. Another model molecule phenol isconsidered as a smaller aromatic molecule with a slight acidityat pH 7. These two representatives were mixed with MC-LR inwater solution to evaluate the competitive effect on the meso-porous carbon MCS/C adsorbent (Fig. 6). The equilibriumadsorption isotherms (Fig. 6A) demonstrate that the adsorptioncapacity of MC-LR decreases from 300 to 100 mg g�1 when anidentical amount (mole) of RhB is mixed into the initial solu-tion. Interestingly, the adsorption amount of RhB is as high as600 mg g�1. For the small competitor phenol (Fig. 6B), it showsa certain amount of improvement for MC-LR adsorption (300–400 mg g�1), while the adsorption amount of phenol is also veryhigh (�250 mg g�1).

In general, the results suggest that the aromatic moleculescan be adsorbed largely and easily on the mesoporous carbonMCS/C because of p–p stacking interactions, which may occupya number of effective adsorption sites or adsorption spacesagainst MC-LR molecules. Most importantly, it is worthnoticing that although competitive adsorbates are introduced,the total amount of adsorbed pollutants sharply increases ontothe mesoporous carbon MCS/C (�700 mg g�1). There are twoaspects for explanation. On the one hand, RhB is positivelycharged; this offers a strong force to attract negatively charged

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Fig. 6 Adsorption isotherms (A) of MC-LR in a single component (a) and mixed with RhB (b) and RhB in bi-components (c); adsorption isotherms (B) of MC-LR in asingle component (a) and mixed with phenol (b) and phenol in bi-components (c) on the mesoporous carbon MCS/C obtained from the silica–carbon composite afteretching the silica component.

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adsorbent MCS/C and adsorbate MC-LR, forming multi-layeradsorption. Based on the intermolecular electrostatic attrac-tion, the pore volumes of primary mesopores on MCS/C can beutilized fully, and the outcome is the promotion of totaladsorption capacity (Scheme 2a and b). On the other hand, thephenomenon that the total adsorption amounts increase maybe related to the difference of occupied sites due to variousmolecular sizes. The small ones can diffuse into the voids orspaces between two large MC-LR molecules or into the smallmesopores, even the micropores, for which MC-LR moleculescannot be utilized (Scheme 2a and c). Therefore, the size of themolecule is an important factor to be considered. Meanwhile,the adsorption amount of MC-LR is also changed by the effect ofcompetitive adsorption. Based on both favourable surfacecharges and similar molecule sizes, RhB molecules take upmost effective adsorption sites against MC-LR, leading to adecline of MC-LR adsorption. The completely opposite situationwith increasing MC-LR adsorption when the phenol competitoris added may be contributed to the faint acidity of phenol,because MC-LRmolecules can be adsorbedmore easily in acidicsolution.44 Eventually, the increased adsorption performancessuggest that the various properties of pollutant molecules mayfurther affect the capacity of MCS/C, but it is still a potentialcandidate in practical water treatment.

Scheme 2 Adsorption model illustration of the competitive adsorption process obimodal mesopore structures: saturation adsorption status (a–c) of MC-LR molecule

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4 Conclusions

In summary, a thorough study into the static, dynamic andcompetitive adsorption behaviours of a series of ordered mes-oporous carbon adsorbents toward toxin MC-LR has beendemonstrated for the rst time. A unique mesoporous carbonadsorbent MCS/C exhibits excellent adsorption performancetowards MC-LR with a saturation adsorption capacity of�526 mg g�1, fast adsorption kinetics, and a 30-fold higheradsorption capacity than that of powdery activated carbon (PACwith high surface area 1990 m2 g�1) for dynamic adsorptionunder high ux. The total adsorption capacity is high up to700 mg g�1 in competitive adsorption with RhB or phenol, andthe performance of regeneration is stable. The properties, suchas highly interconnected bimodal mesopores, large pore sizes(2.8 and 5.8 nm), a high mesopore surface area (1680 m2 g�1), alarge pore volume (1.67 cm3 g�1), straight pore channels( p6mm) and hydrophobic surfaces (carbonized at 900 �C), areadvantageous for the removal of large-sized microcystins. Inaddition, positively charged molecules (RhB), small-sized andweakly-acidic competitors (phenol) facilitate the adsorptionperformance of MCS/C. Therefore, mesoporous carbon MCS/Cexhibits a great potential for practical applications for theremoval of MC-LR or other toxins with large molecular size fromwaste water. Meanwhile, the entire approach can offer scientic

n the 2D hexagonal (p6mm) mesoporous carbon MCS/C adsorbents with larges (a), mixed RhB with MC-LR (b) and mixed phenol with MC-LR (c).

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guidance for selecting a suitable adsorbent to remove otherpollutants.

Acknowledgements

This work was supported by the National Key Basic ResearchProgram (2013CB934104 and 2012CB224805), the NSF of China(21210004), the State Key Laboratory of Pollution Control andResource Reuse Foundation (No. PCRRF12001) and the discoveryproject of Australian Research Council (DP120101194), ShanghaiLeading Academic Discipline Project, Project number: B108, andKing Abdulaziz University (KAU), under grant no. (32-3-1432/HiCi).

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