ZVI Particles Research Articles

Red mud-derived iron carbon catalyst for the removal of organic pollutants in wastewater

In order to reduce the environmental hazards of red mud (RM) and realize its resource utilization, in this study, RM-based iron-carbon micro-electrolysis material (RM-MEM) were prepared by a carbothermal reduction process using RM as raw material. The influence of the preparation conditions on the phase transformation and structural characteristics of the RM-MEM were investigated during the reduction process. The ability of RM-MEM to remove organic pollutants from wastewater was evaluated. The results showed that RM-MEM prepared at a reduction temperature of 1100 °C, a reduction time of 50 min and a coal dosage of 50% had the best removal effect for the degradation of methylene blue (MB). When the initial MB concentration was 20 mg L−1, the amount of RM-MEM material was 4 g L−1, the initial pH was 7, and the degradation efficiency reached 99.75% after 60 min. When RM-MEM is split into carbon free and iron free parts for use, the degradation effect becomes worse. Compared to other materials, RM-MEM has lower cost and better degradation. X-ray diffraction (XRD) analysis showed that hematite was transformed to zero-valent iron with the increase in the roasting temperature. Scanning electron microscopy (SEM) and energy spectroscopy (EDS) analysis showed that micron-sized ZVI particles were formed in the RM-MEM, and increasing the carbon thermal reduction temperature was beneficial to the growth of zero-valent iron particles.

Understanding the positive effects of dissolved Fe2+ and limited aeration on selenate removal from water by nano zero-valent iron supported on biochar

ABSTRACT Batch test was conducted to investigate Se(VI) removal by nano zero-valent iron supported on biochar (BC@nZVI) prepared by a one-step carbothermal synthesis in the presence of ferrous ions and limited aeration. The presence of ZVI and biochar was confirmed in the synthesised material by X-ray diffraction and Raman spectroscopy. TEM analysis revealed that nZVI with a diameter of about 50 nm was dispersed well on the biochar. The Effects of BC@nZVI dosage, initial solution pH, Fe2+ concentration, limited aeration, and coexisting anions on Se(Ⅵ) removal were investigated. The role of Fe2+ on Se(VI) removal have been examined by sequential Fe2+ and Se(VI) dosing tests. More than 98% of Se(VI) (10 mg/L) was removed with BC@nZVI dosage of 1.0 g/L at pH 4.0. The removal percentage of Se(VI) decreased with an increasing in pH from 4.0 to 9.0. The strong electrostatic attraction between Se(VI) and nZVI and the high nZVI activity at low pH are responsible for the significant selenium removal. The removal efficiency of Se(VI) increased with increasing Fe2+ concentration from 0 to 0.5 mmol/L. Fe2+ promotes a shift in the passive layer on nZVI surface towards a medium that favours electron transfer. Se(VI) reduction by ZVI is thought to be accelerated under limited aeration. The positive effect of O2 on selenate reduction can be attributed either to mechanical removal of the oxide layer on the ZVI particles, or to a difference in electron transfer rates, or to a reactive Fe(II)-bearing solid formed when ZVI was oxidised by O2. Cl−, NO3 −, SO4 2− and HA can inhibit the removal of Se(VI) on BC@nZVI in different degrees. The results of XRD, Raman, and XPS characterisation showed that the removal mechanism of Se(VI) include the adsorption and reduction ed of Se(VI) on BC@nZVI. Fe2+ and limited aeration would play a critical role in Se(VI) removal by BC@nZVI.

Synthesis of zero-valent iron supported with graphite and plastic based carbon from recycling spent lithium ion batteries and its reaction mechanism with 4-chlorophenol in water

Graphite and plastic recycled from spent lithium ion batteries were used to synthesize zero-valent iron/graphite (ZVI/G), zero-valent iron/plastic-based carbon (ZVI/P), and zero-valent iron/graphite and plastic-based carbon (ZVI/GP) with iron oxide through carbothermic reduction. The aim of preparing these catalysts is to improve the performance of ZVI in the removal of 4-chlorophenol (4-CP) in water through heterogeneous Fenton reactions. The structural and textural properties of materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 adsorption/desorption, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The synthesis procedure successfully disperses ZVI particles on the synthesized materials. The combination of graphite and plastic-based carbon in ZVI/GP resulted in the best 4-CP removal performance. The degradation data fitted pseudo-first-order kinetic well. The Increase in the ZVI/GP dosage and the hydrogen peroxide concentration enhanced the 4-CP removal due to the increase in the amount of Fe2+ ions and reactive sites. Acidic pH increased the 4-CP removal percentage due to the high H+ concentration. The increase in the temperature favored the •OH formation and facilitated the 4-CP removal. The reaction energy of ZVI/GP reaches 53.54 kJ mol−1, which is competitive among the iron catalysts reported in literatures, and showing the 4-CP removal is reaction-controlled process. This study shows a promising way of recycling graphite and plastic in spent LIBs to prepare ZVI materials for wastewater treatment with the advantages of improved conductivity by graphite and added functional groups by plastic based carbon.

Upgrading the peroxi-coagulation treatment of complex water matrices using a magnetically assembled mZVI/DSA anode: Insights into the importance of ClO radical.

The electrochemical technologies for water treatment have flourished over the last decades. However, it is still challenging to treat the actual complex water effluents by a single electrochemical process, often requiring coupling of technologies. In this study, an upgraded peroxi-coagulation (PC) process with a magnetically assembled mZVI/DSA anode has been devised for the first time. COD, NH3-N and total phosphorous were simultaneously and effectively removed from livestock wastewater. The advantages, influence of key parameters and evolution of electrogenerated species were systematically investigated to fully understand this novel PC process. The fluorescent substances in livestock wastewater could also be almost removed under optimal conditions (300mA, 0.2g ZVI particles and pH 6.8). The interaction between OH and active chlorine yielded ClO with a high steady-state concentration of 6.85×10-13M, which did not cause COD removal but accelerated the oxidation of NH3-N. The Mulliken population suggested that OH and NH3-N had similar electron-donor behavior, whereas ClO acted as an electron-withdrawing species. Besides, although the energy barrier for the reaction between OH and NH3-N (17.0kcal/mol) was lower than that with ClO (18.8kcal/mol), considering the tunneling in the H abstraction reaction, the Skodje-Truhlar method adopted for calculations evidenced a 17-fold faster NH3-N oxidation rate with ClO. In summary, this work describes an advantageous single electrochemical process for the effective treatment of a complex water matrix.

Effects of magnetic field on selenite removal by sulfidated zero valent iron under aerobic conditions

A novel strategy of sulfide modified zero valent iron (S-ZVI) coupled with the magnetic field (MF) is developed for selenite (Se(IV)) removal. The original ZVI particle size (30 μm), S/Fe ratio (1:80), solution pH (5), S-ZVI loading (0.75 g L−1), and MF intensity (20 mT) can exhibit the optimal enhancement effects of MF on Se(IV) removal by S-ZVI. Common corrosion promoters (Cl−, PO43−, SO42−, Mg2+, and Ca2+) and inhibitors (NO3−, SiO32−, and CO32−) show positive and negative effects on Se(IV) removal by S-ZVI, respectively. But MF can alleviate promoting or inhibiting effects of coexisting ions on Se(IV) removal by S-ZVI, and well preserve the reactivity of S-ZVI from background ions in water. Furthermore, MF can also enhance the reactivity of S-ZVI towards Se(IV) during consecutive experiments, the promotion factor (the ratio of kobs with MF to kobs without MF) increased from 2.57 to 5.83 with the increase of cycles. MF can not only improve the reactivity of ZVI covered with iron oxide or iron hydroxide but also effectively enhance the ability of ZVI covered with iron sulfide. S-ZVI exhibited good stability and recyclability in the presence of MF. XANES analysis of selenium species reveals that the reductive product of Se(IV) with or without MF is primarily Se(0), and Se(IV) removal by S-ZVI can be ascribed to adsorption and reduction. This work indicates that MF may widen the application of S-ZVI for pollutants removal in environmental remediation.

Efficiency and Kinetic Rate of Nanoscale and Microscale of Zero Valent Iron and Zinc Oxide particles for Chromium, Cadmium, and Lead Removal from Pak Thong Chai Silk Dyeing Effluent, Thailand

This present study involved the application and comparison of nanoscale particles in remediation for contaminated heavy metal effluent discharge. It aimed to investigate the removal efficiency and kinetic removal rate of the heavy metals including lead, chromium, and cadmium in silk dyeing effluent discharge by using nano and microscale of ZVI and ZnO particles. The contaminated samples were collected and later treated by one of the particles in the laboratory at 25 oC. The mixtures were incubated for the required period before the heavy metal concentrations were measured. The overall results showed that the optimum dosage of all four particle types for heavy metal treatments was 60 mg/L with an optimal time of 60 minutes. The experiments with nZVI demonstrated the highest removal efficiency for all heavy metal types followed by that of nZnO, ZVI, and ZnO, respectively. The removal efficiency rate by all four type particles for Cr was higher than that of Cd and Pb, respectively. In addition to this, the kinetic removal rate of nZVI was also faster than that of nZnO, ZVI, and ZnO, respectively..

Preparation of highly stable and easily regenerated sulfuretted nZVI via one-pot fast pyrolysis method for the removal of diclofenac

Sulfide-modified nanoscale zero-valent iron (S-nZVI) is a commonly used reductive agent in pollutant removal. However, the aggregation of S-nZVI can lower its reduction capacity in the water, and its regeneration remains challenging. To overcome these limitations, one-pot fast pyrolysis of FeSO4-loaded lignocellulosic biomass was proposed to obtain highly stable biochar-supported S-nZVI (S-nZVI/BC) nanoparticles. During this process, Fe2+ were reduced and sulfuretted in situ to form S-nZVI and subsequently covered by the freshly formed carbon film. A series of S-nZVI/BCs pyrolyzed at different temperatures (500–1000 °C) were prepared, among which S-nZVI/BC pyrolyzed at 800 °C (S-nZVI/BC-800) exhibited a fast and stable removal of diclofenac (DCF) via adsorption and reduction. The DCF removal efficiency of S-nZVI/BC-800 reached 80.1% within 4 h, with a particle dosage of 0.5 g/L and Fe dosage of 1 mmol/g. The adsorption and reduction efficiencies of DCF by S-nZVI/BC-800 were 43.2% and 36.9%, respectively. The improved reactivity of S-nZVI/BC-800 can be attributed to the formation of iron sulfides (i.e., FeS and Fe1−xS) in ZVI particles, which increased the electrical conductivity and improved the material selectivity for the reduction of DCF in the water. S-nZVI/BC-800 could be easily regenerated through pyrolysis, during which the carbon film could act as the electron donor. This study provides a facile and skillful method to prepare a highly stable and refreshable S-nZVI, which could be a promising permeable reactive bed material for the remediation of halogenated organic pollutants in contaminated water.

Combination of immobilized TiO2 and zero valent iron for efficient arsenic removal in aqueous solutions

The photocatalytic removal of arsenic from aqueous solutions was investigated using titania (TiO2) immobilized on a glass support, both bare and combined with synthesized metallic iron nanoparticles (nZVI) or commercial microscale iron (ZVI). Three procedures, namely dip-coating, rotational coating, and sponge coating, were tested for achieving the immobilization of TiO2. The photocatalytic activity of the semiconductor films under UV-irradiation after cumulative coatings was evaluated for 10 mg L−1 aqueous As(III), which was entirely oxidized to As(V) with all settings within 90 and 180 min. Titania immobilized by dip-coating was found to be the most effective as it showed the faster kinetics. The reuse of immobilized TiO2 was also investigated, detecting no changes in the photocatalytic activity after five consecutive reactions. The addition of commercial ZVI particles to the immobilized TiO2 system did not bring about significant changes in the kinetics for As(III) oxidation at the three pH values investigated, i.e., 5, 7, and 9. By contrast, the addition of nZVI not only led to a faster depletion of As(III) compared to bare titania but also the removal of As(V) from the solution to concentrations below 10 μg L−1, the upper limit recommended by the World Health Organization for human consumption.The role of iron species in the arsenic removal process with both [ZVI + immobilized-TiO2] and [nZVI + immobilized-TiO2] systems was further investigated by performing adsorption and irradiation experiments without titania. It was inferred that within the pH range evaluated, the minor corrosion of the ZVI surface, even under UV irradiation, restricts the production of reactive oxidizing species and the generation of sites for arsenic species adsorption. By contrast, adsorption should be the main process responsible for the overall diminution of As(III) and As(V) species in solution attained upon nZVI addition, promoted by the increase of the external oxides/hydroxides layer on iron nanoparticles. Nevertheless, it might be also considered a certain contribution of UV-generated oxidant species formed in nZVI to the photocatalytic oxidation performance of titania.

Effects of humic acid on enhanced removal of lead ions by polystyrene-supported nano-Fe (0) nanocomposite

Polymer-supported nanozero-valent iron composites (D001-nZVI) were fabricated for the removal of lead ions from aqueous solutions by embedding nZVI into the porous polystyrene anion exchanger D001. Humic acid (HA) was selected as a model species because of its ubiquitous existence to gain insight into the influencing factors in the actual application process. The iron contents of the composites were approximately 11.2%, and the smallest ZVI particle size was ~ 5 nm. The experimental results showed that the effect of HA on the reduction of lead ions by D001-nZVI was a concentration-dependent process. At low HA concentrations, the surface-competitive adsorption of HA and Pb2+ dominated; therefore, the removal efficiency of Pb2+ by D001-nZVI decreased from 97.5 to 90.2% with an increasing HA concentration. When the HA concentration increased to 30 mg/L or more, the lead ions removal remained constant with the following possible cooperation mechanism: the competitive adsorption of HA and Pb2+ on the nZVI surface and the well-dispersed particles were caused by electrostatic interactions between the HA coating and the nZVI surface. In addition, the adsorption complexation between HA and Pb2+ also had a positive effect on the removal of Pb2+ at higher concentrations of HA.

Green one-spot synthesis of hydrochar supported zero-valent iron for heterogeneous Fenton-like discoloration of dyes at neutral pH

Heterogeneous Fenton-like process is highly effective for treatment of dye wastewater, but it is notably limited by developing cheap, efficient and eco-friendly catalysts. Green one-pot synthesis of hydorchar supported zero-valent iron (HCZVI) was conducted using tea leaves as biomass feedstocks. The properties of HCZVI are characterized by Fourier transform infrared spectra, Raman spectra, X-ray diffraction analysis, scanning electron microscopy and electron probe microanalyzer. Micro and nano ZVI particles are well distributed on hydrochar surface. Fenton-like discoloration of methylene blue (MB) depends on HCZVI dosage, H2O2, pH, MB concentration and temperature. Effective MB discoloration can be obtained under broad pH region. MB removal reaches 97.77% within 60 min under conditions of 0.4 g/L HCZVI, 99.70 mM H2O2, pH 6.4 and 10 mg/L MB. Kinetic analysis of Fenton-like MB discoloration was conducted using the first-order kinetic model, and the calculated activation energy is 74 kJ/mol. MB discoloration dominated by chromophore groups cleavage is attributed to attack of hydroxyl radical generated from HCZVI activation of H2O2. The catalytic system is also effective for discoloration of rhodamine B and acid orange 7. HCZVI is a promising catalyst for Fenton-like discoloration of dye wastewater due to facile fabrication, low cost, and environmental friendliness.

Preparation of porous silicate supported micro-nano zero-valent iron from copper slag and used as persulfate activator for removing organic contaminants

Porous silicate supported micro-nano zero-valent iron (PSi@ZVI) was prepared from copper slag (CS) through carbothermal reduction technology, and used as a persulfate (PS) activator for removing organic contaminants. Results showed that the properties of the activator were greatly affected by the preparation conditions. Calcination for 20 min at 1100 °C with 20% anthracite was considered the optimum preparation condition for degradation of orange G (OG). The removal rate of OG was improved by increasing the dosages of PSi@ZVI or PS and raising the reaction temperature. Moreover, PSi@ZVI exhibited excellent PS activator ability in a wide range of initial pH, good degradation capability for eosin Y, methyl orange, acid fuchsine, and methylene blue. The reusability and safety of PSi@ZVI were verified. Electron paramagnetic resonance and radical quenching tests indicated that sulfate radical (SO4−) was the main active species in the PSi@ZVI/PS system. The X-ray diffraction results indicated that a high calcination temperature (1100 °C) was beneficial to the reduction of iron-bearing minerals to ZVI. Scanning electron microscopy and energy-dispersive spectroscopy results revealed that the formation of porous structure of PSi@ZVI and the generation of nano to micro-sized ZVI particles on the surface of the silicate holes. The X-ray photoelectron spectra showed that ZVI was first convert into Fe(II), which mainly activated PS and generated Fe(III) in the PSi@ZVI/PS system. Furthermore, the intermediates of OG were detected using gas chromatography–mass spectrometry, and the possible degradation pathway of OG was proposed. This study provides a novel approach for reuse of CS as a heterogeneous activator to effectively activate PS.

Mechanistic role of nitrate anion in TCE dechlorination by ball milled ZVI and sulfidated ZVI: Experimental investigation and theoretical analysis

Mechanistic role of NO3− in trichloroethylene (TCE) dechlorination by ball milled, micro-scale sulfidated and unsulfidated ZVI (e.g., S-mZVIbm and mZVIbm) was explored through experiments and density functional theory (DFT) calculations. Sulfidation inhibited NO3− reduction by mZVIbm as S weakened its interaction with NO3−. mZVIbm reduced NO3− within 2 h. This just resulted in a short-term electron competition during the dechlorination process by mZVIbm and hardly affected its sluggish dechlorination kinetics (complete TCE dechlorination in 11 d). On the contrary, NO3− suppressed TCE dechlorination by S-mZVIbm. This was attributed to that inhibited NO3− reduction by S-mZVIbm (40 % reduction in 6 h) induced continuous electron competition with TCE during the time span of its dechlorination by S-mZVIbm. NO3− reduction was also observed to facilitate formation/crystallization of Fe3O4 on both ZVI particles, promoting dechlorination by mZVIbm after 4 d while not taking effect to the S-mZVIbm/TCE system, as its dechlorination time was too short for the surface of S-mZVIbm to transform. This observation has important implication on groundwater remediation by ZVI or sulfidated ZVI PRBs under a scenario of upgradient anthropogenic release of NO3−.

Optimization and mechanism insights into the sulfamethazine degradation by bimetallic ZVI/Cu nanoparticles coupled with H2O2

Zero-valent iron has been recognized as a promising catalyst for the degradation of micropollutants via Fenton-like reactions, however, the enhancement of its performance is insufficiently studied. In this feature, we investigate the activity of bimetallic copper/zero-valent iron nanoparticles (ZVI/Cu) as a heterogeneous catalyst for the degradation of sulfamethazine (SMZ), and intensively elucidate the reaction mechanism. The characterization of the catalyst by XRD, TEM, and EDS confirmed the growth of Cu° on the surface of the ZVI particles. Response surface methodology (RSM) coupled with a central composite design (CCD) optimized operating parameters such as pH, catalyst loading, H2O2 dose, and initial SMZ concentration. Under the optimum conditions (pH = 3.0, H2O2 concentration =2.0 g/L, ZVI/Cu loading =0.8 g/L), SMZ fell below the detection limit (0.036 mg/L) after 30 min of the reaction. The degradation mechanism revealed that hydroxyl radicals were the dominant oxidant species. However, the accumulated iron oxides on the shell of ZVI contributed to SMZ removal by adsorption. We propose a potential pathway for SMZ degradation based on the detected transformation products. This includes an early cleavage of the mediated sulfonamide group, which suggests an efficacious degradation into tentatively single-ring transformation compounds.

Interaction of zero-valent iron and carbonaceous materials for reduction of DDT

Dechlorination of dichlorodiphenyltrichloroethane (DDT) as a model compound was performed with zero-valent iron (micro-ZVI and nano-ZVI) as reductant and carbonaceous adsorbents as sink and catalyst in water. DDT is rapidly converted to dichlorodiphenyldichloroethane (DDD) in direct contact with ZVI. However, up to 90% of the DDD is transformed into non-identified, most likely oligomeric products. There is no indication of dechlorination at the aromatic rings. DDT is still rapidly dechlorinated when it is adsorbed on carbonaceous adsorbents, even though ZVI particles have no direct access to the adsorbed DDT. The carbonaceous materials function as adsorbent and catalyst for the dechlorination reaction at once. From electrochemical experiments, we deduced that direct physical contact between ZVI particles and the adsorbent is essential for enabling a chemical reaction. Electron conduction alone does not effect any dechlorination reaction. We hypothesize hydrogen species (H∗) which spill from the ZVI surface to the carbon surface and initiate reductive transformations there. The role of carbonaceous adsorbents is different for different degradation pathways: in contrast to hydrodechlorination (reduction), adsorption protects DDT from dehydrochlorination (hydrolysis).

Effects of non-reducible dissolved solutes on reductive dechlorination of trichloroethylene by ball milled zero valent irons

Non-reducible solution anions have been well recognized to affect reactivity of ZVI in dechlorinating chlorinated hydrocarbons. However, their effects and corresponding functional mechanisms on electron efficiency (εe) of ZVI remain unclear. In this study, mechanochemically modified microscale sulfidated and unsulfidated ZVI particles (i.e., S-mZVIbm and mZVIbm) and trichloroethylene (TCE) were used as model particles and contaminant to explore such effects. PO43− as a corrosion promoter enhanced initial dechlorination rate by both particles. However, its passivating role as a surface complex agent became significant at the later stage of dechlorination by mZVIbm, while sulfidation alleviated this effect without inhibition of dechlorination. Compared with enhancing dechlorination, PO43− promoted hydrogen evolution reaction (HER) to a higher extent, decreasing εe for both particles by 17–73 %. HCO3− negligibly affected dechlorination by both particles, while elevated HER. Thus, HCO3− [5 mM] decreased εe for S-mZVIbm and mZVIbm by 1.9 % and 22 %. Different from PO43− and HCO3−, Cl− and SO42− showed no significant effects on dechlorination, HER, and therefore εe for both particles. These results imply that even though some co-existing anions (i.e., PO43− and HCO3−) acting as corrosion promoters could improve the dechlorination by ZVIs, they would lead to decreased εe and shortened particle reactive lifetime.

Chemical removal and selectivity reduction of nitrate from water by (nano) zero-valent iron/activated carbon micro-electrolysis

The processes of (n)ZVI/AC（（nano）zero valent iron/activated carbon）micro-electrolysis were applied for nitrate removal from groundwater, aiming to reduce nitrate to N2, an environmentally friendly end product. (n)ZVI was utilized and combined with selected commercial AC to form the micro-electrolysis. Effect of different operational parameters, including reductant dosage, (n)ZVI/AC ratios, and reaction pH, on nitrate and TN removal were cleared. The results showed that nZVI presents higher reaction activities than ZVI in micro-electrolysis. With the increase of the (n)ZVI/AC mass ration from 1:2 to 2:1, the TN removal increased from 16.8% to 38.9%, then declined with the further increase of the ratio. The nitrate removal was negatively correlated with the initial pH of the solution. Compared to ZVI particles, even with a lower dosage, nZVI presented 100% nitrate removal at acidic and neutral pH conditions, and TN removal could maintain higher than 35% with pH lower than 9.0. A kinetic model was also established to explain the pathways of nitrate removal, and the results indicated that AC not only enriched nitrate as an adsorbent but also present highly potential in catalytic converting nitrate to N2. The technique presented great potentials in removing nitrate from water and a promising application prospect.

Comparison of nanoscale zero-valent iron, fenton, and photo-fenton processes for degradation of pesticide 2,4-dichlorophenoxyacetic acid in aqueous solution

Nanoscale zero-valent iron (nZVI) products are highly applicable in groundwater, industrial water, and wastewater treatment due to the high reduction properties, the small size of particles in the range of nanometers, large surface area, and high reactivity on most toxic contaminants. The ultimate aim of this study is to evaluate the removal performance of 2,4-dichlorophenoxyacetic acid (2,4-D) by nanoscaled ZVI particles. Synthesized nanoscale iron particles were characterized by X-ray diffraction and scanning electron microscopy (SEM). According to SEM images of nZVI, the particle size was under 100 nm in diameter. The specific surface area was measured by the N2/BET method and determined as 44.7 ± 0.4 m2/g. The influences of nZVI dosage, initial pH and effects of different processes were examined by batch experiments. Results were compared with Fenton and photo-Fenton processes and they showed that under optimized conditions, degradation by nZVI is more effective than Fenton and photo-Fenton reactions and a promising candidate for 2,4-D remediation.

Preparation and application of Zero Valent Iron immobilized in Activated Carbon for removal of hexavalent Chromium from synthetic effluent

Unlike organic contaminants, heavy metals are not biodegradable and tend to accumulate in living organisms; they are also recognized for being toxic or carcinogenic. The use of nanoparticles of zero-valent iron (nZVI) is reported as an alternative technique with high potential for in situ and ex situ remediation of contaminated matrices with this metal, mainly due to its large active surface area and significant adsorption capacity to consolidate into a simple and efficient method of treatment. In this study, ZVI particles were synthesized by the chemical reduction method using hydrated ferrous sulfate (FeSO4.7H2O) and sodium borohydride (NaBH4) with subsequent aggregation to powdered activated carbon (PAC), forming the adsorbent PAC-ZVI, which was characterized by the techniques of XRD and SEM, which revealed the integration of the catalyst to the activated carbon matrix. Finally, developed kinetic studies revealed that the adsorption kinetics was better adapted to a pseudo second order model, the isotherms were better represented by the Freundlich model and the thermodynamic results showed that the adsorption reaction occurred through a spontaneous process with endothermic interaction between Cr (VI) and PAC-ZVI with increase in the randomness of the system.

Testing different strategies for the remediation of soils polluted with lindane

This work attempts to clarify the remediation processes involved in the treatment of soil spiked with non-soluble species like lindane. To achieve this goal, the remediation of spiked soil is evaluated coupling electro-kinetic soil flushing (EKSF) with three types of permeable reactive barriers (PRB) which consist of soil merged with nanoparticles of ZVI (n-ZVI), granular particles of ZVI (m-ZVI) or granular activated carbon (GAC). Likewise, the effect of reverse polarity in EKSF will be assessed. Results show that, for a given electric field applied, the intensity reached depends on the size and materials of the reactive particles contained in the PRB and decreases in the sequence EKAB-EKmZVIB-EKnZVIB. Additionally, water content and pH and conductivity profiles between rows of electrodes are also affected by the presence of PRB, mainly because ZVI particles can behave as bipolar electrodes and, thus amend current lines and water flux. In terms of lindane mobilization, the differences are even more remarkable since iron particles promote lindane dehalogenation and activated carbon shows a very good adsorption capacity for lindane. After 720 h of operation, the percentage of lindane extracted is below 2% in all EK-strategies while the percentage retained in soil depends on the strategy used: REKSF seems to prevent lindane removal while EKSF and EKAB lead to higher removal. Results are significant for the design of full-scale applications for the remediation of soils polluted with non-soluble species.

Stabilization of zero valent iron (Fe0) on plasma/dendrimer functionalized polyester fabrics for Fenton-like removal of hazardous water pollutants

This study reports the synthesis, immobilization and stabilization of multiscale zero valent iron (Fe0 = ZVI) particles on fibrous polyester (PET) nonwoven membrane for heterogeneous Fenton-like removal of hazardous pollutants in water. Activation of PET fiber surface by air atmospheric plasma with or without a consecutive grafting of hyperbranched poly-(ethylene glycol)-pseudo generation 5 dendrimer having hydroxyl (-OH) end group functionality created polar reactive functional groups allowing immobilization and stabilization of ZVI particles. Synthesis of ZVI was carried out through chemical reduction of ferric ions, either through a single step in-situ, or a two-step ex-situ reduction-immobilization method. The nonwovens were characterized using wettability, Fourier transform infrared spectroscopy (FTIR), optical microscopy, scanning electron microscopy (SEM), X-ray energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD) and thermo-gravimetric analysis (TGA). Results confirmed the formation and immobilization of nano to sub-micronic multi-scale ZVI particles. The particle size, distribution and stability of ZVI were found to be influenced by the methods of ZVI synthesis and PET surface activation used. The ZVI particles initially formed, quasi-instantaneously turned to yellowish brown indicating the formation of oxide layer, except in the case of dendrimer grafted PET, where higher content (22.30%) and stability of ZVI was detected. All ZVI immobilized nonwovens exhibited high effectiveness towards Fenton-like degradation of malachite green dye (20 ppm), with fastest color removal (98% in 20 min) achieved by dendrimer/ex-situ nonwoven. This nonwoven could be used up to eight repeated cycles providing low TDS (52 ppm) and high COD reduction (66.23%). Combined use of eco-friendly plasma and dendrimer grafting, provides efficient fibrous textile base heterogeneous catalysis.