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    ABSTRACT: In this study, a novel composite adsorbent (HBC–Fe3O4–MnO2) was synthesized by combining honeycomb briquette cinders (HBC) with Fe3O4 and MnO2 through a co-precipitation process. The purpose was to make the best use of the oxidative property of MnO2 and the adsorptive ability of magnetic Fe3O4 for enhanced As(III) and As(V) removal from aqueous solutions. Experimental results showed that the adsorption capacity of As(III) was observed to be much higher than As(V). The maximum adsorption capacity (2.16 mg/g) was achieved for As(III) by using HBC–Fe3O4–MnO2 (3:2) as compared to HBC–Fe3O4–MnO2 (2:1) and HBC–Fe3O4–MnO2 (1:1). The experimental data of As(V) adsorption fitted well with the Langmuir isotherm model, whereas As(III) data was described perfectly by Freundlich model. The pseudo-second-order kinetic model was fitted well for the entire adsorption process of As(III) and As(V) suggesting that the adsorption is a rate-controlling step. Aqueous solution pH was found to greatly affect the adsorption behavior. Furthermore, co-ions including HCO3− and PO43− exhibited greater influence on arsenic removal efficiency, whereas Cl−, NO3−, SO42− were found to have negligible effects on arsenic removal. Five consecutive adsorption-regeneration cycles confirmed that the adsorbent could be reusable for successive arsenic treatment and can be used in real treatment applications.
    Journal of Hazardous Materials. 04/2015; 286.
  • Fuel 01/2015; 140:136–142. · 3.41 Impact Factor
  • Chemical Engineering Journal 12/2014; 257:1–9. · 4.06 Impact Factor
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    ABSTRACT: The effect of synthesis methods on magnetic biochars performance was reported.•The single step method demonstrated higher Fe3O4 content, thermal stability and ferromagnetic properties in magnetic biochars.•Significant As(III) (2.004 mg g−1) and As(V) (3.132 mg g−1) adsorption efficiencies were achieved.•Maximum As(III, V) desorption was achieved at pH 13.5 using NaOH solution.•Magnetic biochar synthesis method is simple, cost-effective and can be optimized.
    Biomass and Bioenergy 10/2014; · 3.41 Impact Factor
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    ABSTRACT: Silica-coated magnetite (Fe3O4@SiO2) nanoparticles functionalized with amino, imino and sulfonic groups (Fe3O4@SiO2-mPD/SP) were successfully synthesized via a facile chemical oxidative polymerization of m-phenylenediamine (mPD) and m-sulfophenylenediamine-4-sulfonic acid (SP) monomers, and utilized for selective removal of Pb(II) and Cr(VI) from aqueous solutions. It was revealed by the characterizations that the polymers formed on Fe3O4@SiO2 nanoparticles were the true copolymers with a mPD-SP unit, rather than a mixture of mPD and SP homopolymers. Fe3O4@SiO2-mPD/SP nanocomposites could be easily separated from aqueous solutions within 30 s. The maximum adsorption capacity of Pb(II) (83.23 mg g-1) and Cr(VI) (119.06 mg g-1) on Fe3O4@SiO2-mPD/SP nanocomposites were obtained at the mPD/SP molar ratio of 95:5 and 50:50, respectively. Moreover, satisfactory selective removal of Pb(II) and Cr(VI) from their mixtures with Cu(II) and Ni(II) ions were exhibited by the Fe3O4@SiO2-mPD/SP(95:5) and Fe3O4@SiO2-mPD/SP(50:50), respectively. The Pb(II) adsorption equilibrium was reached within 5 min by Fe3O4@SiO2-mPD/SP(95:5). The adsorption data of Pb(II) and Cr(VI) were both fitted well to the Freundlich isotherm and followed the pseudo-second-order kinetic model. The adsorption mechanism of Pb(II) and Cr(VI) on Fe3O4@SiO2-mPD/SP nanocomposites included five processes, namely: ion-exchange, complexation adsorption, reduction reaction, electrostatic attraction and physical adsorption. The enhanced adsorption performance of nanoparticle-based magnetic adsorbents for selective removal of heavy metal ions can be achieved with such a copolymerization strategy.
    RSC Advances 09/2014; · 3.71 Impact Factor
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    ABSTRACT: The potential of Cr(VI) reduction by Escherichia coli in the presence of soluble Fe(III) was investigated to explore the chemo-biologically mediated reduction process under anaerobic condition. The reduction efficiency of Cr(VI) reached 95% within 24 h. The influences of experimental parameters, including initial pH, temperature, Fe(III) dosage, carbon source, and chelating agent, were also investigated. The highest efficiency of reduction was observed when pH was 5.8 and temperature was 32°C. Amendments of culture medium with Fe(III) and citric-3Na enhanced Cr(VI) reduction, while the addition of EDTA-2Na inhibited the process. Analysis showed that soluble Fe(III) enhanced the reduction process by shuttling electrons from bio-reduced Fe(II) to Cr(VI) in a coupled biotic-abiotic cycle and hence, Cr(VI) was reduced to Cr(III) followed by deposition to sludge.
    Desalination and water treatment 07/2014; 52. · 0.99 Impact Factor
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    ABSTRACT: The presence of elevated concentration of arsenic in water sources is considered to be health hazard globally. Calcination process is known to change the surface efficacy of the adsorbent. In current study, five adsorbent composites: uncalcined and calcined Fe3O4-HBC prepared at different temperatures (400°C and 1000°C) and environment (air and nitrogen) were investigated for the adsorptive removal of As(V) and As(III) from aqueous solutions determining the influence of solution's pH, contact time, temperature, arsenic concentration and phosphate anions. Characterizations from FTIR, XRD, HT-XRD, BET and SEM analyses revealed that the Fe3O4-HBC composite at higher calcination temperature under nitrogen formed a new product (fayalite, Fe2SiO4) via phase transformation. In aqueous medium, ligand exchange between arsenic and the effective sorbent site ( = FeOOH) was established from the release of hydroxyl group. Langmuir model suggested data of the five adsorbent composites follow the order: Fe3O4-HBC-1000°C(N2)>Fe3O4-HBC (uncalcined)>Fe3O4-HBC-400°C(N2)>Fe3O4-HBC-400°C(air)>Fe3O4-HBC-1000°C(air) and the maximum As(V) and As(III) adsorption capacities were found to be about 3.35 mg g-1 and 3.07 mg g-1, respectively. The adsorption of As(V) and As(III) remained stable in a wider pH range (4-10) using Fe3O4-HBC-1000°C(N2). Additionally, adsorption data fitted well in pseudo-second-order (R2>0.99) rather than pseudo-first-order kinetics model. The adsorption of As(V) and As(III) onto adsorbent composites increase with increase in temperatures indicating that it is an endothermic process. Phosphate concentration (0.0l mM or higher) strongly inhibited As(V) and As(III) removal through the mechanism of competitive adsorption. This study suggests that the selective calcination process could be useful to improve the adsorbent efficiency for enhanced arsenic removal from contaminated water.
    PLoS ONE 06/2014; 9(6):e100704. · 3.53 Impact Factor
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    ABSTRACT: Elevated arsenic concentrations have been detected in drinking water sources worldwide and it threatens to over 200 million people in both developing and developed countries. Adsorption is a conventional process for arsenic removal from contaminated water. Several classes of adsorbing materials have been tested so far. However, far less attention was paid towards granular-based adsorption and granulation processes. The present work is the first attempt to consider both the granular adsorbent and the granulation process. A particular emphasis was given to cost-efficient adsorbent for small scale arsenic removal. Some of the features of granular adsorbents are summarized in tables and graphs; address necessary outlines for readers to easily overview the adsorbents' characteristics and design sustainable adsorption system. Earlier, cost of arsenic removals from granular adsorbents were not widely affirmed, but in this review few of them are incorporated for comparisons in future studies. Thus, one gram of arsenic removal from water using novel and iron oxide-coated sand adsorbents is approximately ranged US$2.3–5.1 and US$3.3–4.2, respectively. Moreover, methods employed for regeneration of exhausted granular adsorbents are discussed. Field scale arsenic remediation measures and the performance evaluations are additionally reported to identify the feasibility of these approaches for scaling up, awareness raising and promotion.
    CLEAN - Soil Air Water 05/2014; · 2.05 Impact Factor
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  • Shams Ali Baig
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    ABSTRACT: Nanosized titanium nitride (nTiN) doped palladium/nickel (Pd/Ni) foam electrodes were successfully prepared via electroless deposition method. The electrodes were evaluated by different techniques including field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and linear sweep voltammetry (LSV). FE-SEM images demonstrated that two different morphologies existed in the Pd layer after nTiN doping. The nTiN doped Pd/Ni foam electrodes were found to be highly effective for electrochemical reductive dechlorination of 2,4-dichlorophenoxyacetic acid (2,4-D) with excellent activity and stability, as revealed by batch experiments. Under the conditions of nTiN doping content of 2 mg, Pd loading of 0.44 mg cm −2 , the energetic electrode achieved nearly 100% removal of 2,4-D (0.226 mmol L −1 ) within 2 h at a current density of 1.667 mA cm −2 . However, the removal efficiency reached only 57.13% when a normal Pd/Ni foam electrode with identical Pd loading and current density was utilized. A successive 2,4-D reductive dechlorination process was observed. o-Chlorophenoxyacetic acid (o-CPA), p-chlorophenoxyacetic acid (p-CPA) and phenoxyacetic acid (PA) were detected and identified as transformation products. Regression analysis proved that the pseudo-first order kinetic model was not suitable to describe the dechlorination process on nTiN doped Pd/Ni foam electrodes due to the appearance of a plateau in the beginning of the curve. Moreover, an adsorption theory for Pd chemisorption of active hydrogen atom was proposed to better explain the phenomenon. An adsorption equilibrium of hydrogen existed in the Pd lattice between hydrogen in Pd solid solution and hydrogen in metal hydride, which would influence the effective utilization of active hydrogen atom [H] for dechlorination treatment. An indirect reduction mechanism of the 2,4-D dechlorination on the as-prepared electrodes was also elucidated.
    Applied Catalysis B: Environmental 04/2014; 158-159:38-47. · 5.63 Impact Factor
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    ABSTRACT: Flue gas desulfurization system used for SO2 removal has co-beneficial removal of Hg, which has resulted in Hg-laden gypsums. With growing beneficial reuse applications of the FGD gypsum, it has been recognized as a potential source of Hg pollution. In this paper, the fate and mobility of Hg were investigated. The Hg content in four samples varied widely and it showed a significant correlation between Hg and sulfite contents in gypsum. In leachate, Hg concentration varied during the leaching process. The Hg extraction rate generally increased with decreasing pH value, which suggested that the environmental risk of FGD gypsum increased during the multipurpose utilization processes, resulted from severe acid rain. The released Hg from FGD gypsum used in this study exhibited biphasic kinetics. Hg in FGD gypsum samples not only appeared in the leachate but also re-emitted into the air. The Hg reduction kinetics followed the pseudo-first-order kinetic model well. Our results provide the theoretical understanding for the co-removal of highly soluble oxidized Hg in WFGD systems and also in the recycling of the FGD gypsum.
    Fuel Processing Technology 02/2014; 118:28–33. · 3.02 Impact Factor
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    ABSTRACT: In the present study, coupled reduction–sorption of Cr(VI) using three iron containing minerals (magnetite, hematite, and pyrrhotite) in aqueous solutions was investigated as a function of solution pH, contact time, and particle size. Detailed characterizations were performed using Brunauer–Emmett–Teller (BET), environmental scanning electron microscopy, and X-ray diffraction (XRD) techniques. Results demonstrated that over 99% of Cr(VI) removal was achieved just after 1 min of the reaction using pyrrhotite with particle size (100–200 mesh). In comparison, removal efficiency of hematite and magnetite against Cr(VI) was below 40% after 2 h of the reaction. Acidic aqueous medium proved effective for Cr(VI) removal and nearly 100% Cr(VI) removal was achieved at pH 3 using pyrrhotite (30–40 mesh), while the surface efficacy of hematite and magnetite has also improved in acidic solution. In terms of removal efficiency, the three minerals followed the order: pyrrhotite > magnetite > hematite. However, no significant difference in the BET specific surface area was recorded among these minerals, but the mineralogical compositions played an important role for removing Cr(VI) in aqueous solutions. Analysis of XRD pattern revealed that iron contents produce Fe3FeSiO4(OH)5 and FeCr2O4 after the reaction with soluble Cr(VI) and precipitated. This study suggested that high ferrous ions-based minerals can effectively remove Cr(VI) from contaminated water environments.
    CLEAN - Soil Air Water 02/2014; 42(10). · 2.05 Impact Factor
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    ABSTRACT: The adsorptive removal of As(V) from aqueous solutions using iron-coated honeycomb briquette cinder (Fe-HBC) is presented. Low cost mechanical granulation process was integrated with surface amendment technology to prepare iron-oxide modified granular adsorbent for clean water production. Detailed characterizations were performed using FTIR, XRD, EDS and SEM techniques. Operating parameters including initial As(V) concentration, pH, contact time, adsorbent dose, iron leaching and the effects of competing ions on As(V) removal were evaluated. Results demonstrated that high amount of arsenate (961.5 μg g−1) was adsorbed at pH 7.5 in 14 h contact time. Langmuir, Freundlich and Temkin isotherm models were used to analyze the adsorption data, whereas Langmuir model was found to best represent the data with a correlation co-efficient (R2 = 0.999). Thus, As(V) sorption on Fe-HBC surface suggested monolayer adsorption and indicated surface homogeneity. Moreover, the dimensionless parameter (RL) value calculated to be about 0.118 that reiterated the process is favorable and spontaneous. The influences of competing ions on As(V) removal decreased in the following order: PO43->HCO3->F->Cl-. The profound inhibition effects of PO43- revealed a high affinity toward iron(oxy) hydroxide. Life-cycle assessment confirmed that spent HBC is non-hazardous and can be used as a promising sorbent for arsenic removal.
    Arabian Journal of Chemistry 01/2014; 7(1):27–36. · 2.68 Impact Factor
  • Applied Catalysis B: Environmental. 01/2014; s 158–159:38–47.
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    ABSTRACT: The suppressed ion chromatography (IC) and molybdenum blue methods were used to comparatively evaluate phosphorus (P) concentrations. Most of the P was more resistant to hydrolysis in ion chromatography as compared to the molybdenum blue method. However, P analysis by IC is more liable to be interfered than the molybdenum blue method because of the presence of high bivalent and trivalent metal ions. Polyvalent metal ions interfere with organic P hydrolysis or the release of P from colloids during P investigation, which leads to a difference of ortho-phosphate concentrations determined by IC and molybdenum blue methods. During the environmental samples analysis, the ortho-phosphate obtained by the IC method was usually less than that obtained by the molybdenum blue method.
    Communications in Soil Science and Plant Analysis 09/2013; 44(17). · 0.42 Impact Factor
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    Shams Ali Baig
    Ecological Engineering 09/2013; 60:345-353. · 3.04 Impact Factor
  • Shams Ali Baig
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    ABSTRACT: Cr(VI) is a toxic pollutant and its reduction to relatively less toxic Cr(III) can solve this problem to a greater extent. In the present study, coupled reduction–sorption of Cr(VI) in aqueous solutions using limonite was investigated as a function of pH, limonite dose and particle size. Results demonstrated that the smaller limonite particle size and low pH aqueous medium favored high Cr(VI) removal. Significant Cr(VI) removal (> 55 ± 1%) was achieved with 100–200 mesh, whereas only 25 ± 0.7% and 10 ± 0.5% removals were attained using 30–40 mesh and 20–30 mesh, respectively, after 2 h reaction. Acid pH proved beneficial and the complete Cr(VI) removal was observed at pH < 4.0 compared to that of 10 ± 0.5% at pH 9.0. Moreover, above 53 ± 2.5% of Cr(VI) removal rates were maintained in the first three batch experiment runs and then drastically decreased to below 5 ± 0.3% in experiment Run-7. The Brunauer–Emmett–Teller (BET) surface area and sorption capacity of limonite were 35.22 m2 g− 1 and 10.03 mg g− 1, respectively. The reaction mechanism demonstrated that under acidic aqueous medium, the dissolved Fe(II) and S(II) on limonite surface reacted with Cr(VI) and formed Cr3S4 and Cr5Si3 precipitates. But the resultant precipitates on limonite surface hindered further Cr(VI) removal and passivated, affirmed in XRD and ESEM analyses. This study suggested that limonite can be used for the effective removal of Cr(VI) from contaminated water environments.
    Hydrometallurgy 06/2013; 138:33-39. · 2.22 Impact Factor
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    Desalination and water treatment 05/2013; 51(16-18):3454-3462. · 0.99 Impact Factor
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    ABSTRACT: Nanoscale zero valent iron (nZVI) particles, prepared by an in situ chemical reduction method, were employed for 2,4-dichlorophenoxyacetic acid (2,4-D) hydrodechlorination combined with the electrochemical method using a palladium/nickel foam (Pd/Ni foam) electrode. The nZVI particles were characterized by X-ray diffraction and high-resolution transmission electron microscopy. Whereas the chemi-deposited catalytic electrode was further characterized using X-ray diffraction, scanning electron microscopy and Energy dispersive X-ray. More rapid hydrodechlorination rate was observed using synergistic technology and almost all of the 2,4-D were degraded in 4 h, which was 12.5% higher than that obtained in the independent electrochemistry system. Furthermore, the reaction mechanism was discussed in terms of the mutual effect between electrochemistry and nZVI. Both of the removal efficiency and the current efficiency depended on several factors including palladium loading, nZVI dosage and current density. Small amount of nZVI dosage not only effectively improved the efficiencies but also substantially reduced the processing cost. Palladium loading and current density had a greater effect on the efficiencies. Phenoxyacetic (PA), o-chlorophenoxyacetic acid (o-CPA) and p-chlorophenoxyacetic acid (p-CPA) have been identified as transformation products in reactive medium.
    Chemical Engineering Journal 05/2013; 223:192–199. · 4.06 Impact Factor
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    ABSTRACT: The water quality and cyanobacterial variation of rivers surrounding southern Taihu Lake, China were purposively monitored from 2008 to 2010. Trophic level index (TLI) was used to evaluate the trophic levels of southern Taihu Lake. Results showed a considerable decline in the monitored data compared with 2007, and the data showed downward trends year after year. The TLI decreased from 55.6 to 51.3, which implied that southern Taihu Lake was mildly eutrophic. The water quality and cyanobacterial variation indicated a positive response to the adopted control measures in the southern Taihu Lake basin, but the intra- and inter-annual variability was still quite varied. High concentrations of nitrogen and phosphorus typically lead to algae outbreaks, however, the cyanobacteria growth may result in a decline of the concentration of nitrogen and phosphorus. Temperature and other weather conditions are also important factors for algae outbreaks; the risk of blue-green algal blooms still persists.
    Water Environment Research 05/2013; 85(5):397-403. · 1.00 Impact Factor

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