Application of Zero-Valent Iron Nanoparticles in Advanced Wastewater Treatment

APPLICATION OF ZERO-VALENT IRON NANOPARTICLES IN

ADVANCED WASTEWATER TREATMENT

Asya Drenkova-Tuhtan, Carsten Meyer, Heidrun Steinmetz

Institute for Sanitary Engineering, Water Quality and Solid Waste Management (ISWA),

University of Stuttgart; Bandtäle 2, 70569 Stuttgart, Germany

E-mail address: [email protected]; Tel.: +49 711 685-63720

Introduction Dealing with matter at the nanoscale (1-100 nm) involves many challenges, but at the same time provides new opportunities for engineering applications which may improve, supplement or even replace some of the conventional environmental protection and treatment technologies. Nanoscale zero-valent iron (nZVI) has been used for a long time in the electronic and chemical industries due to its magnetic and catalytic properties [1]. Recently, nZVI gets an increasing attention in environmental engineering as well and is becoming a popular method for pilot and large-scale in-situ applications in groundwater remediation and treatment of contaminated soil, hazardous and toxic wastes [2]. Numerous studies have demonstrated that nanoscale iron particles are effective for the transformation of a wide array of common environmental contaminants such as chlorinated methanes, ethanes, ethenes and benzenes, organochlorine pesticides, chlorinated phenols, PCBs, organic dyes, various inorganic compounds [3], metal cations [4] and removal of arsenic from natural surface- or groundwater used as a drinking water source [5-6]. Despite its significant contaminants removal capability, the possible applications of nZVI in the field of wastewater treatment have been poorly investigated so far. The goal of this research work was to study the potential to use zero-valent iron nanoparticles in the field of advanced wastewater treatment. Lab-scale batch experiments were performed to test and compare the efficiency of 3 different nZVI commercial products as an alternative method for elimination of phosphate phosphorus, as well as simultaneous removal of some common recalcitrant organic micropollutants and sequestration of heavy metals from a spiked municipal wastewater effluent. Research of the reaction kinetics and the most important reaction parameters, such as nZVI loading, pH, reaction time, mixing method, was carried out until optimal conditions and high elimination rates were achieved.

Materials and Methods Zero-valent iron nanoparticles typically have a core-shell structure with the core being zero-valent iron (Fe0) and the shell – iron oxides or hydroxides formed from oxidation of the iron as illustrated in Figure 1 (left). This structure gives the nZVI a large surface and redox potential. Thus, iron nanoparticles exhibit dual characteristics

of both iron oxides (as a sorbent) and metallic iron (as a reductant), which combined with their high surface area due to the nano-dimensions, results in unique properties for removal and transformation of contaminants [7].

Figure 1: Conceptual model of the nZVI core-shell structure [7] (left) and experimental setup (right)

Three commercial nZVI products (Table 1) from two different manufacturers were tested and compared in a series of experiments carried out in a 1 L batch-reactor. Table 1: Chemical composition and physical properties of the applied commercial ZVI products [8-9]

Product name RNIP-10E NANOFER 25 NANOFER 25S

Manufacturer TODA KOGYO Corp. NANOIRON s.r.o. (Czeh Republic)

Composition

of the slurry

Fe0 5-16% Fe0 14-18% same as

NANOFER 25 +

stabilizer (sodium

polyacrylate acid

surfactant)

Fe3O4 12-1% Fe3O4 6-2%

Polymer 3% Carbon 0-1%

H2O 80% H2O 80%

Particle size [nm] < 70 < 50

BET surface area [m2/g] > 30 > 25

Specific weigh [g/cm3] 1.2 1.2

pH 11 - 12 11 - 12

All grab wastewater samples were fetched from the effluent of the municipal wastewater treatment plant for education and research of the Institute for Sanitary Engineering (ISWA) at the University of Stuttgart and spiked with H3PO4 to a concentration of 5-6 mg/L [PO4]-P, which would have been the actual effluent concentration if no chemical precipitation in the biological treatment took place. pH was maintained with HCl or NaOH during the reaction. [PO4]-P concentrations were measured photometrically in duplicate. The analysis of organic micropollutants with GC-MS required addition of 300 µL internal standards (PAK, AHTN-d3 and Caffeine-13C3) to each sample and pre-concentration of the organics via liquid-liquid extraction with dichloromethane (CH2Cl2). The heavy metals were analyzed with ICP-OES. All chemicals were purchased from Merck KGaA, Germany.

Wastewater spiked with 5mg/L [PO4]-PnZVI (1.3 – 5.2 g/L) HCl for pH regulation

Results and Discussion The most efficient phosphate elimination was achieved with RNIP-10E and NANOFER 25 (Figure 2), while NANOFER 25S resulted in an unexpected increase of PO4-P concentration and was classified as not suitable for wastewater treatment.

Figure 2: Elimination efficiency of [PO4]-P as a function of pH (left) and nZVI concentration (right)

The elimination mechanism is mainly attributed to the adsorption of phosphate ligands on the magnetite surface through donation of the ligand's lone electron pairs and formation of coordination complexes [10]. The result was an impressive 95% elimination efficiency only after 30 min of reaction with 5.2 g/L nZVI at pH=4.5.

Figure 3: Removal of selected organic micropollutants with 5g/L nZVI at different pH ranges

The removal of the organic micropollutants performed best when the reaction pH was maintained in the range 4.5 to 5.0 without spiking with the inhibiting H3PO4. Table 2: Sequestration of heavy metals from wastewater after treatment with 5g/L nZVI at pH=8

Heavy metal Initial C0 (mg/L) Final C (mg/L) Removal rate (%) Removal mechanism [4]

Copper (Cu2+)

Zinc (Zn2+)

9,77 ± 0.3

10,05 ± 0.2

0,020 ± 0.01

0,765 ± 0.12

99,8 %

92,4 %

Chemical reduction

Adsorption

Conclusions This work presented several of the diverse applications of nanoscale zero-valent iron and its unique properties to transform, inactivate or completely eliminate a multitude of contaminants occurring in municipal wastewater based on its core-shell structure. It was demonstrated that nZVI can be an efficient alternative for phosphate-phosphorus elimination (>95% after 30 min reaction at pH=4.5). At the same time, based on the optimal conditions for phosphate elimination, an analysis for simultaneous removal of recalcitrant organic micropollutants was carried out. Most of these polar trace compounds were efficiently sorbed on the nanoparticles surface, which resulted in high removal rates, especially for Triclosan, MTBT, the polycyclic musks (>90%) and Carbamazepine (~70%). This makes nZVI a suitable alternative or provides a potential to be applied in combination with the currently known advanced treatment methods for elimination of micropollutants such as ozonation, activated carbon adsorption, AOP, membrane filtration, ion exchange [11]. In addition, nZVI performed excellent with almost complete uptake of Cu2+ and Zn2+ via respectively reduction and adsorption in an alkaline pH range. The achieved results provide substantial arguments to propose the application of zero-valent iron nanoparticles as a novel approach for purifying wastewater. It is evident that nZVI has a significant potential to be utilized as a universal, wide-spectrum agent for advanced wastewater treatment. References [1] Martin, J., Herzing, A., Yan, W., Li, X., Koel, B., Kiely, C. and Zhang, W. 2008. Determination of

the oxide layer thickness in core-shell zerovalent iron nanoparticles. Langmuir 24 : 4329 - 4334.

[2] Zhang, W.-X. 2003. Nanoscale iron particles for environmental remediation: An overview. Journal of Nanoparticle Research 5: 323–332.

[3] Sun, Y., Li, X., Cao, J., Zhang, W. and Wang, H.P. 2006. Characterization of zero-valent iron nanoparticles. Advances in Colloid and Interface Science 120 : 47 - 56.

[4] Li, X. and Zhang, W. 2007: Sequestration of metal cations with zerovalent iron nanoparticles – a study with high resolution X-ray photoelectron spectroscopy (HR-XPS). Journal of Physical Chemistry C 111 : 6939 - 6946.

[5] Mohan, D. and Pittman Jr., C.U. 2007. Arsenic removal from water/wastewater using adsorbents - A critical review. Journal of Hazardous Materials 142 : 1–53.

[6] Su, C. and Puls, R.W. 2001. Arsenate and arsenite removal by Zerovalent iron: Effect of phosphate, silicate, carbonate, borate, sulphate, chromate, molybdate, and nitrate, relative to chloride. Environmental Science & Technology 35 : 4562 - 4568.

[7] Li, X. und Zhang, W. 2006. Iron nanoparticles: the core-shell structure and unique properties for Ni(II) sequestration. Langmuir 22 : 4638 - 4642.

[8] BMS Inc., Crown Point, IN, USA. 2011. Nanoscale Iron Technology. www.bioxtech.com/nanoscaletech. Link browsed on 31.05.2012.

[9] NANO IRON, s.r.o., Rajhrad, Czech Republic. 2010: NANOIRON – Future Technology. www.nanoiron.cz/en. Link browsed on 31.05.2012.

[10] Daou, T.J., Begin-Colin, S., Greneche, J.M., Thomas, F., Derory, A., Bernhardt, P., Legare, P., und Pourroy, G. 2007. Phosphate adsorption properties of magnetite-based nanoparticles. Chemistry of Materials 19: 4494 - 4505.

[11] Hunziker Betatech AG. 2008: Massnahmen in ARA zur weitergehenden Elimination von Mikroverunreinigungen - Kostenstudie. Winterthur. Bundesamt für Umwelt BAFU

Universität StuttgartUniversität Stuttgart


Application ofZero Valent Iron NanoparticlesZero‐Valent Iron Nanoparticles

in Advanced Wastewater Treatment

Young Water Talents Symposiumg y pSingapore International Water Week 2012

Dipl Ing Asya Drenkova Tuhtan M ScDipl.‐Ing. Asya Drenkova‐Tuhtan, M.Sc.

Institute for Sanitary Engineering, Water Quality and Solid Waste Management (ISWA)University of Stuttgart, Germany



Research ObjectivesResearch Objectives

11Bench‐scale experiments for [PO4]‐P adsorption on iron nanoparticles

22Test nano‐iron potential to remove recalcitrant organic micropollutants

33Investigate nZVI efficiency for sequestration of heavy metals

44Analyse possible separation methods for iron nanoparticles

55Outlook on other nZVI potential applications in wastewater treatment



Properties of the nZVI Core Shell Structure

Characterization of Zero‐Valent Iron Nanoparticles

Properties of the nZVI Core‐Shell Structure

oten

tial [

mV] Before

phosphatation

Fe3O

4Sh

ell Z

eta

Po

Afterphosphatation

pH

D l ti d ti ti

Source: Li & Zhang [2006]; Langmuir (22), 4638-4642Source: J. Martin et al. [2008]; Langmuir (24), 4329‐4334 Source: Daou [2007]; Chem. Mater. (19), 4494-4505

F

Dual properties: reduction + sorption

Fe0 core delivers e‐ for reduction and precipitation of cations (e.g. metals)

Fe3O4 shell offers surface coordination and sorption as a function of pH

High specific BET surface area (> 30 m2/g) → enhanced sorp on proper es



nZVI Commercial Products used in the Project

Characterization of Zero‐Valent Iron Nanoparticles

nZVI Commercial Products used in the Project

ProductName Manufacturer Composition Particle

SizeBET Surface

Area pH SpecificWeight

RNIP‐10 E TODA KOGYOCorp.

Fe0Fe3O4PolymerH2O

11% (5‐16)6% (12‐1)3 %80 %

d < 70 nm > 30 m2/g 11 ‐ 12 1.2 g/cm3

H2O 80 %

NANOFER 25 NANO IRONs.r.o.

Fe0Fe3O4Carbon

15% (14‐18)5% (6‐2)0‐1 % d < 50 nm > 25 m2/g 11 ‐ 12 1.2 g/cm3

H2O 80 %

NANOFER 25S NANO IRONs.r.o. NANOFER 25 + stabilizer (sodium polyacrylate acid surfactant)



Phosphorus Concentrations at LFKW (10 000 PE) in 2011

Phosphate‐Phosphorus Elimination (1)

Phosphorus Concentrations at LFKW (10 000 PE) in 2011

Source: LFKW [2011]; www.iswa.uni‐stuttgart.de/lfkw/fliesschema



Phosphate elimination pH nZVI dosage product type

Phosphate‐Phosphorus Elimination (2)

Phosphate elimination – pH, nZVI dosage, product type

Adsorption phosphate ligands bind metal(Fe) atoms via donation of lone e‐ pairs

> 95% [PO4]‐P uptake at optimum conditions:[ 4] p p pH = 4.5 Fe0 concentration = 5.2 g/L

TODA KOGYO performed the best: 95%pelimination after 30 min reaction (0.26 mg/L)



Selected Organic Micropollutants in the LFKW Effluent

Organic Micropollutants Removal (1)

Selected Organic Micropollutants in the LFKW EffluentName Chemical structure Description

HHCBHHCB‐lactone

AHTN

Polycyclic musks ‐ fragrances in perfumes, washing powders, shampoos, etc.Lipophilic, polar. Bioaccumulation in fish.

MTBT 2‐methylthiobenzothiazoleFungicide or stabilizer in the rubber production. Polar, biologically active compound, toxic to fish.

Antimicrobial agent in toothpaste soapTriclosan

Antimicrobial agent in toothpaste, soap, medical care products. Toxic to fish and algae. May form dioxins at high temp.

Carbamazepine Pharmaceutical ‐ anticonvulsant drug for Carbamazepine(CBZ)

epilepsy, mood stabilizer, anti‐stress.Lipophilic, < 10% removal in WWTP.

N N‐diethyl‐Active ingredient in insect repellents.

DEET N,N diethylm‐toluamide Lipophilic. Moderate pesticide, slightly

toxic to birds, fish, aquatic invertebrates

TCPP Tris (1‐chlor‐2‐propyl) Chlorinated organophosphate esters. l d l h f

TCPPTCEP

Tris (2‐chloroethyl)phosphates

Flame retardants in polyurethane foam, plasticisers.Bioaccumulation,cancirogenic



Organic Micropollutants Removal with 5 g/L nZVI



BEFORE

AFTER



Sequestration of Heavy Metals with 5 g/L nZVI

Sequestration of Heavy Metal Cations

Sequestration of Heavy Metals with 5 g/L nZVI

Much higher metal removing capacity than conventional sorbents (e.g. AC) Removal based on standard oxidation‐reduction potentials of metal ions E0Fe < E0Me for thermodynamically favorable e‐ transfer through the oxide shell R l ffi i 99 8 % f C 2+ d 92 4 % f Z 2+ Removal efficiency: 99,8 % for Cu2+ and 92,4 % for Zn2+

Electrode Half‐Reaction E0 [V]

Barium (Ba) Ba2+ + 2 e‐ ↔ Ba ‐2.90

Zinc (Zn) Zn2+ + 2 e‐ ↔ Zn ‐0.76

Iron (Fe) Fe2+ + 2 e‐ ↔ Fe ‐0.41

Cadmium (Cd) Cd2+ + 2 e‐ ↔ Cd ‐0.40

Nickel (Ni) Ni2+ + 2 e‐ ↔ Ni ‐0.24

Lead (Pb) Pb2+ + 2 e‐ ↔ Pb ‐0.13

Source: Li and Zhang [2007]; J. Phys. Chem. 111, 6939‐6946

Lead (Pb) Pb + 2 e ↔ Pb 0.13

Copper (Cu) Cu2+ + 2 e‐ ↔ Cu +0.34

Mercury (Hg) Hg2+ + 2 e‐ ↔ Hg +0.86

C O 2 14H+ 6Chromium (Cr) Cr2O72‐ + 14H+ + 6e‐

↔ 2 Cr3+ + 2 H2O+1.36

Source: W. Stumm [1996]



Magnetic Separation of Iron Nanoparticles

Separation Methods for nZVI Nanoparticles

Magnetic Separation of Iron Nanoparticles

Alternative to conventional methods for solid‐liquid separation (sedim., filtration) nZVI ferromagnetic properties; Fe3O4 is the most magnetic of all natural minerals Possible recovery and reuse of the oxidized nanoparticles

Magnetic field (1 Tesla)column separator

Stainless steelwool

packed columnpacked column

Source: J.T. Mayo [2007]

Source: M. Franzreb, FZK [2003]



Integration of nZVI Treatment Step and Conclusion

Separation Methods for nZVI Nanoparticles

Integration of nZVI Treatment Step and Conclusion

> 95% [PO4]‐P uptake at optimum conditions: pH≈5.0, Fe0 loading 5.2 g/L

Significant removal of organic trace elements at pH≈5 0 with 5 g/L nZVI Significant removal of organic trace elements at pH≈5.0 with 5 g/L nZVI

Almost complete elimination of Cu2+ and Zn2+ at pH≥7 with 5 g/L nZVI

nZVI: universal wide spectrum agent for advanced wastewater treatment? nZVI: universal, wide spectrum agent for advanced wastewater treatment?



Thank you for your attention!y y

Application of Zero-Valent Iron Nanoparticles in Advanced Wastewater Treatment

Documents

Transcript of Application of Zero-Valent Iron Nanoparticles in Advanced Wastewater Treatment