Immobilization of nanoscale Fe0 in and on PVA microspheres for nitrobenzene reduction

Enhanced Cr(VI) stabilization in soil by carboxymethyl cellulose-stabilized nanosized Fe0 (CMC-nFe0) and mixed anaerobic microorganisms

A collaborative system of carboxymethyl cellulose stabilized nanosized zero-valent iron (CMC-nFe⁰) and microorganisms was set up to enhance the stabilization of Cr(VI) in soil. In comparison with an aqueous-bound Cr(VI) removal of 18.9% in the nFe⁰ system, a higher Cr(VI) removal of 68.9% was achieved in the nFe⁰ and microorganisms system after 14 d remediation because the microorganisms on the nFe⁰ surface promoted nFe⁰ corrosion and enhanced abiotic and biotic Cr(VI) stabilization by generating highly active minerals such as magnetite, lepidocrocite and green rust on the nFe⁰ surface. As a stabilizing agent for nFe⁰ and an organic substrate for microorganisms, CMC on the nFe⁰ surface not only enhanced the dispersion of nFe⁰, but also boosted the activity of microorganisms, resulting in a promotion of 0.9 and 0.5 times higher aqueous-bound Cr(VI) removal via the improvement of nFe⁰ and microorganisms respectively, thus a total 4 times higher aqueous-bound Cr(VI) removal of 95.3% was achieved in the CMC-nFe⁰ and microorganisms system as compared to the nFe⁰ system. After 14 d remediation, easily available species of Cr(VI) and Cr_total, such as water soluble (WS), exchangeable (EX) and bounded to carbonates (CB), were mainly transformed to less available Fe-Mn oxides-bounded (OX) and residual (RS) species because of the production of ferrochrome precipitates (Cr_xFe_1-xOOH or Cr_xFe_1-x(OH)₃). Besides, the stabilization of Cr(VI) in the CMC-nFe⁰ and microorganisms system was pH-dependent and it increased with CMC-nFe⁰ dosage. Due to excellent Cr(VI) stabilization and Cr immobilization, coupled CMC-nFe⁰ and anaerobic microorganisms process is of great potential in remediating Cr(VI)-containing soil.

How do zinc oxide and zero valent iron nanoparticles impact the occurrence of antibiotic resistance genes in landfill leachate?

ZnO NP exposure accelerated the dissemination of ARGs by dominantly driving changes in bacterial community, and Fe⁰ NP exposure promoted the attenuation of ARGs by mainly decreasing the abundances of MGEs.

Immobilization of powdery calcium silicate hydrate via PVA covalent cross-linking process for phosphorus removal

Calcium silicate hydrate (CSH) is a popular material used for phosphorus removal in recent years. In this work, a novel immobilized material, polyvinyl alcohol-CSH (PVA-CSH), was prepared using a 1:10 weight ratio of CSH powder to 8% PVA solution and then used for phosphorus removal. Samples were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The adsorption mechanism and practical application properties of phosphorus wastewater were studied by sequential batch and continuous flow experiment. The results showed PVA-CSH possessed a porous network structure and an average pore diameter of 24.94 ± 0.11 nm. Furthermore, the CSH functional groups were unaffected by PVA immobilization. Compared with CSH, PVA-CSH did not easily lose CSH after being immobilized by PVA, and the duration of efficient phosphorus removal stage was approximately 20 h longer than that of CSH. In addition, the effluent turbidity of PVA-CSH was 0.11 ± 0.03 NTU during the continuous operation period, which was significantly lower than CSH. In summary, this research study demonstrated the significant potential of PVA-CSH for practical phosphorus removal.

Exploring temple floral refuse for biochar production as a closed loop perspective for environmental management

Religious faith and ritual activities lead to significant floral offerings production and its disposal as waste to the nearby open lands and water bodies. These activities result into various social and environmental nuisances because of their high organic content. Alternatively, it can be used as valuable resources for various biochemical and thermo-chemical processes. Floral refuse has been utilized in natural dye extraction, however, the residual solid refuse is of significant environmental concern due to its nutrient rich nature. This study explores the potential utilization of solid residue of temple floral refuse after natural dye extraction by thermo-chemical decomposition of it. The slow pyrolysis of solid residue was performed at 350 °C and 500 °C, and the biochar yield of 42 and 36% was obtained, respectively. TGA-DTG analysis was performed to observe the thermo-chemical behaviour of floral refuse. The biochar products were further characterized by FTIR, SEM, EDX, BET, XRD, and RAMAN spectroscopy to observe the impact of pyrolysis temperature (PT) on the resulting material, i.e. biochar and its possible application measures. EDX results revealed the presence of various macro-nutrients such as C, N, P, K Ca and Mg in different proportions which showed its soil amelioration potential. Moreover, based on the SEM and BET results, biochar prepared at 500 °C was further explored for adsorption of methylene blue dye at various dose and pH conditions. Based on Langmuir (R² = 0.98) and Freundlich (R² = 0.97) isotherms, it is found as a potential adsorbent material for removal of methylene blue dye. The results revealed that biochar conversion of colour extracted floral refuse can be a vital option for quick and efficient management of it in a closed loop approach.

Current advances and trends in electro-Fenton process using heterogeneous catalysts - A review

Over the last decades, advanced oxidation processes have often been used alone, or combined with other techniques, for remediation of ground and surface water pollutants. The application of heterogeneous catalysis to electrochemical advanced oxidation processes is especially useful due to its efficiency and environmental safety. Among those processes, electro-Fenton stands out as the one in which heterogeneous catalysis has been broadly applied. Thus, this review has introduced an up-to-date collation of the current knowledge of the heterogeneous electro-Fenton process, highlighting recent advances in the use of different catalysts such as iron minerals (pyrite, magnetite or goethite), prepared catalysts by the load of metals in inorganic and organic materials, nanoparticles, and the inclusion of catalysts on the cathode. The effects of physical-chemical parameters as well as the mechanisms involved are critically assessed. Finally, although the utilization of this process to remediation of wastewater overwhelmingly outnumber other utilities, several applications have been described in the context of regeneration of adsorbent or the remediation of soils as clear examples of the feasibility of the electro-Fenton process to solve different environmental problems.

Ultrasonically synthesized organic liquid-filled chitosan microcapsules: part 1: tuning physical & functional properties

This study reports the synthesis of tetradecane-filled chitosan microcapsules in acetic acid aqueous solutions using high intensity ultrasound at 20 kHz. The size, size distribution, and stability of microcapsules were tuned by varying the concentration of acetic acid from 0.2% to 25% v/v. After long-time storage at room temperature (more than 3 months), the microcapsules maintained their shell-core structure where the volume of the microcapsules at 0.2% acetic acid concentration increased by 8.3% due to leaking and coalescence. Microcapsules were consistently spherical and had a smooth shell surface, however, their shell thickness varied with acetic acid concentration. The relaxation behavior of individual microcapsules to an applied constant stress was measured by atomic force microscopy (AFM) to probe the shell strength and extent of crosslinking. The effect of acetic acid on the relative viscosity of chitosan aqueous solutions played a major role in microcapsule size control at low acid concentrations. With constant addition of acetic acid, amino groups in chitosan chains were acetylated partially under ultrasonic irradiation. This reduced the amphiphilicity of the shell material and therefore influenced the size, size distribution, stability and mechanical strength of the microcapsules. Apart from the acetylation effect, the counter-ion effect and the formation of covalent bond crosslinks also made contributions to the formation of stable chitosan microcapsules.

Removal of chlorinated organic solvents from hydraulic fracturing wastewater by bare and entrapped nanoscale zero-valent iron

With the increasing application of hydraulic fracturing, it is urgent to develop an effective and economically feasible method to treat the large volumes of fracturing wastewater. In this study, bare and entrapped nanoscale zero-valent iron (nZVI) were introduced for the removal of carbon tetrachloride (CT) and 1,1,2-trichloroethane (TCA) in model high-salinity fracturing wastewater. With increasing ionic strength (I) from Day-1 (I = 0.35 M) to Day-90 (I = 4.10 M) wastewaters, bare nZVI presented significantly lower removal efficiency of CT (from 53.5% to 38.7%) and 1,1,2-TCA (from 71.1% to 21.7%) and underwent more serious Fe dissolution from 1.31 ± 1.19% in Day-1 to 5.79 ± 0.32% in Day-90 wastewater. Particle aggregation induced by high ionic strength was primarily responsible for the lowered performance of nZVI due to less available reactive sites on nZVI surface. The immobilization of nZVI in alginate with/without polyvinyl alcohol provided resistance to particle aggregation and contributed to the superior performance of entrapped nZVI in Day-90 wastewater for 1,1,2-TCA removal (62.6-72.3%), which also mitigated Fe dissolution (4.00-4.69%). Both adsorption (by polymer matrix) and reduction (by immobilized nZVI) were involved in the 1,1,2-TCA removal by entrapped nZVI. However, after 1-month immersion in synthetic fracturing wastewater, a marked drop in the reactivity of entrapped nZVI for 1,1,2-TCA removal from Day-90 wastewater was observed with significant release of Na and total organic carbon. In summary, bare nZVI was sensitive to the nature of the fracturing wastewater, while the use of environmentally benign entrapped nZVI was more promising for wastewater treatment.

Nitrobenzene reduction using nanoscale zero-valent iron supported by polystyrene microspheres with different surface functional groups

Three polystyrene (PS) resin microspheres supported nanoscale zero-valent iron (nZVI), i.e., nZVI@PS, nZVI@PS-Cl, and nZVI@PS-N, were prepared and characterized by FT-IR, XPS, SEM, EDS, and weighing method. The functional groups on the carriers showed obvious influence on the loading quantity, the micro morphology, and the reduction efficiency of these supported nZVI. The best hybrid reducer was nZVI@PS-N. The load quantity of nZVI was 0.2476 g/g, and some of them were dispersed and the others remained as particles (≤ 50 nm). At optimal reaction conditions, i.e., initial solution pH = 3, 25 °C, 100 r/min stirring, 99% nitrobenzene (NB) in 250 mL 123.1 mg/L NB solution could be totally reduced into AN by 1.31 g fresh nZVI@PS-N within 20 min. The excellent reduction efficiency and fast degradation rate of nZVI@PS-N were mainly attributed to the synergistic effects between the good adsorption property of its carrier and the high reduction activity of nZVI particles. NZVI@PS-N was reproducible and recycled, and 90.6% degradation ratio of NB was till obtained at its seventh recycle. The results showed that nZVI@PS-N had high potential practical application value in the reductive degradation and emergency rescue of nitrobenzene pollutant.

Aging effects on chemical transformation and metal(loid) removal by entrapped nanoscale zero-valent iron for hydraulic fracturing wastewater treatment

In this study, alginate and polyvinyl alcohol (PVA)-alginate entrapped nanoscale zero-valent iron (nZVI) was tested for structural evolution, chemical transformation, and metals/metalloids removal (Cu(II), Cr(VI), Zn(II), and As(V)) after 1-2month passivation in model saline wastewaters from hydraulic fracturing. X-ray diffraction analysis confirmed successful prevention of Fe⁰ corrosion by polymeric entrapment. Increasing ionic strength (I) from 0 to 4.10M (deionized water to Day-90 fracturing wastewater (FWW)) with prolonged aging time induced chemical instability of alginate due to dissociation of carboxyl groups and competition for hydrogen bonding with nZVI, which caused high Na (7.17%) and total organic carbon (24.6%) dissolution from PVA-alginate entrapped nZVI after 2-month immersion in Day-90 FWW. Compared to freshly-made beads, 2-month aging of PVA-alginate entrapped nZVI in Day-90 FWW promoted Cu(II) and Cr(VI) uptake in terms of the highest removal efficiency (84.2% and 70.8%), pseudo-second-order surface area-normalized rate coefficient k_sa (2.09×10^-1Lm^-2h^-1 and 1.84×10^-1Lm^-2h^-1), and Fe dissolution after 8-h reaction (13.9% and 8.45%). However, the same conditions inhibited Zn(II) and As(V) sequestration in terms of the lowest removal efficiency (31.2% and 39.8%) by PVA-alginate nZVI and k_sa (4.74×10^-2Lm^-2h^-1 and 6.15×10^-2Lm^-2h^-1) by alginate nZVI. The X-ray spectroscopic analysis and chemical speciation modelling demonstrated that the difference in metals/metalloids removal by entrapped nZVI after aging was attributed to distinctive removal mechanisms: (i) enhanced Cu(II) and Cr(VI) removal by nZVI reduction with accelerated electron transfer after pronounced dissolution of non-conductive polymeric immobilization matrix; (ii) suppressed Zn(II) and As(V) removal by nZVI adsorption due to restrained mass transfer after blockage of surface-active micropores. Entrapped nZVI was chemically fragile and should be properly stored and regularly replaced for good performance.

Pseudomonas sp. LZ-Q continuously degrades phenanthrene under hypersaline and hyperalkaline condition in a membrane bioreactor system

Graphical Abstract

Abstract

Phenanthrene is one of the most recalcitrant components of crude oil-contaminated wastewater. An efficient phenanthrene-degrading bacterium Pseudomonas sp. strain named LZ-Q was isolated from oil-contaminated soil near the sewage outlet of a petrochemical company. Pseudomonas sp. LZ-Q is able to degrade 1000 mg/L phenanthrene in Bushnell-Hass mineral salt medium. It also degrades other polycyclic aromatic hydrocarbons such as naphthalene, anthracene, pyrene, petrol, and diesel at broad ranges of salinities of 5 g/L to 75 g/L, pHs of 5.0–10.0, and temperatures of 10–42 °C. Therefore, Pseudomonas sp. LZ-Q could be a good candidate for remediation of polycyclic aromatic hydrocarbon (PAH)-contaminated wastewater. A membrane bioreactor (MBR) was applied to investigate the remediation ability of the strain LZ-Q. Wastewater containing phenanthrene with pH of 8, salinity of 35 g/L, and COD of 500 mg/L was continuously added to the system (HRT = 3 h). Results showed that Pseudomonas sp. LZ-Q is capable of degrading 96% of 20 mg/L phenanthrene and 94% of 500 mg/L COD for 60 days in a continuous mode. These results showed that the MBR system with strain LZ-Q might be a good approach for PAHs’ remediation in industrial wastewaters.

Synthesis and surface protection of nano zerovalent iron (NZVI) with 3-aminopropyltrimethoxysilane for water remediation of cobalt and zinc and their radioactive isotopes

A method is described to synthesize a novel magnetic nano-sorbent via surface modification and protection of nano-zerovalent iron (NZVI) with 3-aminopropyl trimethoxysilane for the formation of NZVI-NH₂.

Hydrogen production from the dissolution of nano zero valent iron and its effect on anaerobic digestion

Nano zero valent iron (NZVI) has shown inhibition on methanogenesis in anaerobic digestion due to its reductive decomposition of cell membrane. The inhibition was accompanied by the accumulation of hydrogen gas due to rapid NZVI dissolution. It is not clear whether and how rapid hydrogen release from NZVI dissolution directly affects anaerobic digestion. In this study, the hydrogen release kinetics from NZVI (average size = 55 ± 11 nm) dissolution in deionized water under anaerobic conditions was first evaluated. The first-order NZVI dissolution rate constant was 2.62 ± 0.26 h(-1) with its half-life of 0.26 ± 0.03 h. Two sets of anaerobic digestion experiments (i.e., in the presence of glucose or without any substrate but at different anaerobic sludge concentrations) were performed to study the impact of H2 release from rapid NZVI dissolution, in which H2 was generated in a separate water bottle containing NZVI (i.e., ex situ H2 or externally supplied from NZVI dissolution) before hydrogen gas was introduced to anaerobic digestion. The results showed that the H2 partial pressure in the headspace of the digestion bottle reached as high as 0.27 atm due to rapid NZVI dissolution, resulting in temporary inhibition of methane production. Nevertheless, the 5-d cumulative methane volume in the group with ex situ H2 production due to NZVI dissolution was actually higher than that of control, suggesting NZVI inhibition on methanogenesis is solely due to the reductive decomposition of cell membrane after direct contact with NZVI.

Amphiphilic polyvinyl alcohol adsorbent for the removal of low-density lipoprotein

Spacer can effectively reduce the steric hindrance and synergistic effect of the hydrophilic and hydrophobic ligands immobilized in adsorbents can improve the specific adsorption for low-density lipoprotein (LDL). In this paper, in order to improve the adsorption capacity for the Low-density lipoprotein-cholesterol (LDL-C), specifically, amphiphilic adsorbent based on polyvinyl alcohol (PVA) containing cholesterol ligand and sulfonic dextran ligands was synthesized. All kinds of factors affecting the synthesis yield and adsorption properties were studied in detail. Results showed that the amphiphilic PVA adsorbent has higher adsorption capacity for total cholesterol (TC), (LDL-C), triglyceride (TG), and lower adsorption capacity, and percentage for high-density lipoprotein-cholesterol (HDL-C), while the ligand ratio of cholesterol to sulfonic ligands is 1.57:1, the adsorption percentage and adsorption capacity for TC, LDL-C, TG, and HDL-C were 54.4%, 67.6%, 42.5%, 10.4% and 4.02, 3.612, 2.154, 0.168 mg/g, respectively.

Impact of nano zero valent iron (NZVI) on methanogenic activity and population dynamics in anaerobic digestion

Nano zero valent iron (NZVI), although being increasingly used for environmental remediation, has potential negative impact on methanogenesis in anaerobic digestion. In this study, NZVI (average size = 55 ± 11 nm) showed inhibition of methanogenesis due to its disruption of cell integrity. The inhibition was coincident with the fast hydrogen production and accumulation due to NZVI dissolution under anaerobic conditions. At the concentrations of 1 mM and above, NZVI reduced methane production by more than 20%. At the concentration of 30 mM, NZVI led to a significant increase in soluble COD (an indication of cell disruption) and volatile fatty acids in the mixed liquor along with an accumulation of H2, resulting in a reduction of methane production by 69% (±4% [standard deviation]). By adding a specific methanogenesis inhibitor-sodium 2-bromoethanesulfonate (BES) to the anaerobic sludge containing 30 mM NZVI, the amount of H2 produced was only 79% (±1%) of that with heat-killed sludge, indicating the occurrence of bacterially controlled hydrogen utilization processes. Quantitative PCR data was in accordance with the result of methanogenesis inhibition, as the level of methanogenic population (dominated by Methanosaeta) in the presence of 30 mM NZVI decreased significantly compared to that of the control. On the contrary, ZVI powder (average size <212 μm) at the same concentration (30 mM) increased methane production presumably due to hydrogenotrophic methanogenesis of hydrogen gas that was slowly released from the NZVI powder. While it is a known fact that NZVI disrupts cell membranes, which inhibited methanogenesis described herein, the results suggest that the rapid hydrogen production due to NZVI dissolution also contribute to methanogenesis inhibition and lead to bacterially controlled hydrogenotrophic processes.

Biodegradation of high concentration of nitrobenzene by Pseudomonas corrugata embedded in peat-phosphate esterified polyvinyl alcohol

Efficiency on biodegradation of high concentration of nitrobenzene (NB) by peat-phosphate esterified polyvinyl alcohol-embedded NB-degrading bacteria Pseudomonas corrugata was conducted compared to free bacteria cells. Its biodegradation kinetics, reuse ability, degradation effect in the absence of the essential element needed for the growth of bacteria and degradation efficiency of the raw water from the contaminated site were also invested. Results show that the degradation rate when the concentration of NB was at 600, 750, and 900 mg/L reached 91.02, 83.23, and 55.9 %, which was higher than that observed in free bacteria at the same concentration levels. Biodegradation kinetics of the material could be well described by first- and zero-order kinetics when the concentration of NB was at 300, 450 mg/L and 600, 750, 900 mg/L, respectively. Stable degradation activity (stayed at a level of approximately 70 %) was displayed during the 11th repeat-batch experiment. The affect of absence of phosphorus in the medium can be abated ascribed to the addition of peat, which contributes with organic matter and other elements such as nitrogen and phosphorus necessary to maintain metabolically active the microorganisms. Effective biodegradation of the raw water from the experimental site revealed that the material can be a potential candidate for treating NB-contaminated wastewater in the practical setting.

The impact of zero-valent iron nanoparticles upon soil microbial communities is context dependent

Nanosized zero-valent iron (nZVI) is an effective land remediation tool, but there remains little information regarding its impact upon and interactions with the soil microbial community. nZVI stabilised with sodium carboxymethyl cellulose was applied to soils of three contrasting textures and organic matter contents to determine impacts on soil microbial biomass, phenotypic (phospholipid fatty acid (PLFA)), and functional (multiple substrate-induced respiration (MSIR)) profiles. The nZVI significantly reduced microbial biomass by 29 % but only where soil was amended with 5 % straw. Effects of nZVI on MSIR profiles were only evident in the clay soils and were independent of organic matter content. PLFA profiling indicated that the soil microbial community structure in sandy soils were apparently the most, and clay soils the least, vulnerable to nZVI suggesting a protective effect imparted by clays. Evidence of nZVI bactericidal effects on Gram-negative bacteria and a potential reduction of arbuscular mycorrhizal fungi are presented. Data imply that the impact of nZVI on soil microbial communities is dependent on organic matter content and soil mineral type. Thereby, evaluations of nZVI toxicity on soil microbial communities should consider context. The reduction of AM fungi following nZVI application may have implications for land remediation.

Impact of metallic and metal oxide nanoparticles on wastewater treatment and anaerobic digestion

Metallic and metal oxide nanomaterials have been increasingly used in consumer products (e.g. sunscreen, socks), the medical and electronic industries, and environmental remediation. Many of them ultimately enter wastewater treatment plants (WWTPs) or landfills. This review paper discusses the fate and potential effects of four types of nanoparticles, namely, silver nanoparticles (AgNPs), nano ZnO, nano TiO2, and nano zero valent iron (NZVI), on waste/wastewater treatment and anaerobic digestion. The stabilities and chemical properties of these nanoparticles (NPs) result in significant differences in antimicrobial activities. Analysis of published data of metallic and metal oxide NPs suggests that oxygen is often a prerequisite for the generation of reactive oxygen species (ROS) for AgNPs and NZVI, while illumination is necessary for ROS generation for nano TiO2 and nano ZnO. Furthermore, such nanoparticles are capable of being oxidized or dissolved in water and can release metal ions, leading to metal toxicity. Therefore, AgNPs and nano TiO2 are chemically stable NPs that have no adverse effects on microbes under anaerobic conditions. Although the toxicity of nanomaterials has been studied intensively under aerobic conditions, more research is needed to address their fate in anaerobic waste/wastewater treatment systems and their long-term effects on the environment.

Effect of sulfate on anaerobic reduction of nitrobenzene with acetate or propionate as an electron donor

Sulfate is frequently found in wastewaters that contain nitrobenzene. To reveal the effect of sulfate on the reductive transformation of nitrobenzene to aniline--with acetate or propionate as potential electron donors in anaerobic systems--an acetate series (R1-R5) and a propionate series (R6-R10) were set up. Each of these was comprised of five laboratory-scale sequence batch reactors. The two series were amended with the same amount of nitrobenzene and electron donor electron equivalents, whereas with increasing sulfate concentrations. Results indicated that the presence of sulfate could depress nitrobenzene reduction. Such depression is linked to the inhibition of nitroreductase activity and/or the shift of electron flow. In the acetate series, although sulfate did not strongly compete with nitrobenzene for electron donors, noncompetitive inhibition of specific nitrobenzene reduction rates by sulfate was observed, with an inhibition constant of 0.40 mM. Propionate, which can produce intermediate H₂ as preferred reducing equivalent, is a more effective primary electron donor for nitrobenzene reduction as compared to acetate. In the propionate series, sulfate was found to be a preferential electron acceptor as compared to nitrobenzene, resulting in a quick depletion of propionate and then a likely termination of H₂-releasing under higher sulfate concentrations (R9 and R10). In such a situation, nitrobenzene reduction slowed down, occurring two-stage zero-order kinetics.

Synthesis of nanoscale zero-valent iron/ordered mesoporous carbon for adsorption and synergistic reduction of nitrobenzene

Nanoscale zero-valent iron (NZVI) supported on ordered mesoporous carbon (OMC) was synthesized through liquid phase reduction route. The NZVI/OMC composite was characterized by X-ray diffraction, N(2) adsorption/desorption and transmission electron microscopy. Results reveal that the composite possesses ordered mesostructure with NZVI distributing homogeneously on the surface of OMC support. The removal effects of nitrobenzene (NB) in water with OMC, NZVI/OMC and non-supported NZVI were evaluated. Results indicate that NZVI/OMC shows enhanced removal efficiency, which is attributed to its adsorption and synergistic reduction for NB. The transformation process of NB was further investigated by HPLC. Nitrosobenzene and phenylhydroxylamine were detected as intermediate products and aniline was the final reductive product.

Synthesis of novel inorganic-organic hybrid materials for simultaneous adsorption of metal ions and organic molecules in aqueous solution

In this paper, atom transfer radical polymerization (ATRP) and radical grafting polymerization were combined to synthesize a novel amphiphilic hybrid material, meanwhile, the amphiphilic hybrid material was employed in the absorption of heavy metal and organic pollutants. After the formation of attapulgite (ATP) ATRP initiator, ATRP block copolymers of styrene (St) and divinylbenzene (DVB) were grafted from it as ATP-P(S-b-DVB). Then radical polymerization of acrylonitrile (AN) was carried out with pendent double bonds in the DVD units successfully, finally we got the inorganic-organic hybrid materials ATP-P(S-b-DVB-g-AN). A novel amphiphilic hybrid material ATP-P(S-b-DVB-g-AO) (ASDO) was obtained after transforming acrylonitrile (AN) units into acrylamide oxime (AO) as hydrophilic segment. The adsorption capacity of ASDO for Pb(II) could achieve 131.6 mg/g, and the maximum removal capacity of ASDO towards phenol was found to be 18.18 mg/g in the case of monolayer adsorption at 30°C. The optimum pH was 5 for both lead and phenol adsorption. The adsorption kinetic suited pseudo-second-order equation and the equilibrium fitted the Freundlich model very well under optimal conditions. At the same time FT-IR, TEM and TGA were also used to study its structure and property.

Electrochemical study of nitrobenzene reduction on galvanically replaced nanoscale Fe/Au particles

Nanoscale Fe/Au particles were fabricated on glassy carbon substrates by electrodeposition of Fe and the subsequent galvanic replacement with Au. The particles were characterized by scanning electron microscopy and transmission electron microscopy, and a hollow structure was found. The process and mechanism of electrochemical reduction of nitrobenzene on Fe/Au particles were studied by cyclic voltammetry and constant-potential electrolysis. The results showed that nanoscale Fe/Au particles exhibited higher catalytic activity than bulk gold for nitrobenzene reduction. Nitrobenzene reduction proceeded following different pathways with different electrolyte compositions. The removal rate of nitrobenzene on nanoscale Fe/Au particles was up to 97% with electrolysis within 120 min at -0.35 V in 0.1 M H(2)SO(4) and aniline was found to be the electrolysis product.

Reduction of nitrobenzene in groundwater by iron nanoparticles immobilized in PEG/nylon membrane

The highly reactive iron nanoparticles (NPs) immobilized in nylon membrane were synthesized and characterized, and the reduction of nitrobenzene (NB) in groundwater by the NPs was investigated. Environmental scanning electron microscopy (ESEM) images showed that the NPs distributed homogeneously on the membrane surface without agglomeration. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses revealed that the NPs immobilized in membrane were mainly composed of Fe-oxides rather than zero-valent iron. Thermogravimetric (TG) analysis suggested that the weight percentage of the immobilized NPs and the oxygen introduced to the reacted sample after 80min reaction were about 18.5% and 13%, respectively. Moreover, Fourier transform infrared (FTIR) analysis further demonstrated the changes on the membrane surface after thermal grafting, NPs immobilizing and reacting for 80min. Using the reactive NPs immobilized in nylon membrane, NB in groundwater was rapidly and quantitatively decreased by 68.9% just in the first 20min, the Fe(2+) associated with the iron NPs immobilized in PEG/nylon66 membrane was mainly responsible for this reduction. The reaction appeared to follow pseudo-first-order kinetics and the rate constants increased upon decreasing the pH value. The samples we prepared exhibited good corrosion resistance for humic acid (HA) but had a short-term performance for NB degradation. More so, the groundwater chemistry had a negative influence on the reactivity of membrane immobilized NPs.

Degradation of trinitroglycerin (TNG) using zero-valent iron nanoparticles/nanosilica SBA-15 composite (ZVINs/SBA-15)

Trinitroglycerin (TNG) is an industrial chemical mostly known for its clinical use in treating angina and manufacturing dynamite. The wide manufacture and application of TNG has led to contamination of vast areas of soil and water. The present study describes degradation of TNG with zero-valent iron nanoparticles (ZVINs) in water either present alone or stabilized on nanostructured silica SBA-15 (Santa Barbara Amorphous No. 15). The BET surface areas of ZVINs/SBA-15 (275.1 m2 g(-1)), as determined by nitrogen adsorption-desorption isotherms, was much larger than the non-stabilized ZVINs (82.0 m2 g(-1)). X-ray diffraction (XRD) showed that iron in both ZVINs and ZVINs/SBA-15 was present mostly in the α-Fe0 crystalline form considered responsible for TNG degradation. Transmission Electron Microscopy (TEM) showed that iron nanoparticles were well dispersed on the surface of the nanosilica support. Both ZVINs and ZVINs/SBA-15 degraded TNG (100%) in water to eventually produce glycerol and ammonium. The reaction followed pseudo-first-order kinetics and was faster with ZVINs/SBA-15 (k1 0.83 min(-1)) than with ZVINs (k1 0.228 min(-1)). The corresponding surface-area normalized rate constants, knorm, were 0.36 and 0.33 L h(-1) m(-2) for ZVINs/SBA-15 and ZVINs, respectively. The ZVINs/SBA-15 retained its original degradation efficiency of TNG after repeatedly reacting with fresh nitrate ester for five successive cycles. The rapid and efficient transformation of TNG with ZVINs/SBA-15, combined with excellent sustained reactivity, makes the nanometal an ideal choice for the clean up of water contaminated with TNG.

Selective removal for Pb2+ in aqueous environment by using novel macroreticular PVA beads

Batch sorption experiments were conducted using macroreticular poly(vinyl alcohol) (MR-PVA) beads as a adsorbent to adsorb Pb(II) from both single component system and multi-metal solution in which experimental parameters were studied including solution pH, contact time, adsorbent dose, initial concentration of metal ions and ionic strength. The equilibrium isotherms were determined at pH 6 under constant ionic strength and at different temperatures. The results showed that the maximum adsorption capacity of Pb(II) (213.98 mg g(-1)) with 1 g L(-1) of adsorbent was observed at 300 mg L(-1) at an initial pH value of 6.0 under temperature of 288 K. Removals of about 60% occurred in 30 min, and equilibrium was attained at around 150 min. The equilibrium data for the adsorption of Pb(II) on MR-PVA beads was tested with various adsorption isotherm models among which three models were found to be suitable for the Pb(II) adsorption. In addition, the kinetic adsorption fitted well to the pseudo-second-order model and the corresponding rate constants were obtained. Thermodynamic aspects of the adsorption process were also investigated.

Reduction of hexavalent chromium by carboxymethyl cellulose-stabilized zero-valent iron nanoparticles

The reduction of hexavalent chromium or Cr(VI) by zero-valent iron (Fe(0)) nanoparticles has received increasing attention in recent years. However, Fe(0) nanoparticles prepared using conventional methods suffered several drawbacks due to their high reactivity towards surrounding media, which led to the formation of much larger flocs and significant loss in reactivity. To overcome these problems, we synthesized Fe(0) nanoparticles by applying water-soluble carboxymethyl cellulose (CMC) as a stabilizer. CMC-stabilized Fe(0) nanoparticles displayed much less agglomeration but greater Cr(VI) reduced power than those prepared without a stabilizer. At a dose of 0.15 g L(-)(1), CMC-stabilized Fe(0) nanoparticles were able to reduce 100% of 10 mg L(-)(1) Cr(VI) in minutes. Several factors that may affect the efficiency of Cr(VI) removal were investigated. These included the concentration of CMC, the concentration of Fe(0) nanoparticles, the initial Cr(VI) concentration, the pH value, the reaction temperature and the concentration of the calcium cation in the reaction mixture. Our study suggested that the introduction of an innocuous stabilizer such as CMC could significantly improve the performance of Fe(0) nanoparticles for environmental remediation applications.