Publications

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    ABSTRACT: The electrochemical reductive dechlorination of 2,4-dichlorophenoxyacetic acid (2,4-D) in an aqueous solution was investigated at ambient temperature using a palladium/nickel foam (Pd/Ni foam) electrode in batch mode experiments. The catalytic electrode prepared using the standard chemical deposition method was further characterized using X-ray diffraction and scanning electron microscopy. It was observed that the reaction followed a pseudo-first-order kinetics model, the magnetic agitatorsupported system could achieve 87% removal of 2,4-D within 4 h, which is 16% higher than the efficiency obtained under a nitrogen atmosphere. No organic intermediates other than phenoxyacetic (PA), o-chlorophenoxyacetic acid (o-CPA) and p-chlorophenoxyacetic acid (p-CPA) were observed to be generated during the reaction. The dechlorination efficiency depended on several factors including the current density, the palladium loading and the initial concentrations of the supporting NaCl electrolyte and the 2,4-D. The palladium loading and the NaCl concentration had a greater effect on the dechlorination kinetics of 2,4-D. Furthermore, the efficiencies of dechlorination and PA formation could be improved by optimizing the reaction system by modifying the ventilation conditions.
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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; · 2.05 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 01/2014; 118:28–33. · 2.82 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. · 2.27 Impact Factor
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    Shams Ali Baig
    Ecological Engineering 09/2013; 60:345-353. · 2.96 Impact Factor
  • Shams Ali Baig
    CLEAN - Soil Air Water 07/2013; · 2.05 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. · 2.17 Impact Factor
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    Desalination and water treatment 05/2013; 51(16-18):3454-3462. · 0.85 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. · 1.13 Impact Factor
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    ABSTRACT: Palladium/Iron (Pd/Fe) nanoparticles were prepared by using ultrasound strengthened liquid phase reductive method to enhance dispersion and avoid agglomeration. The dechlorination of 2,4-dichlorophenol (2,4-DCP) by Pd/Fe nanoparticles was investigated to understand its feasibility for an in situ remediation of contaminated groundwater. Results showed that 2,4-DCP was first adsorbed by Pd/Fe nanoparticles, then quickly reduced to o-chlorophenol (o-CP), p-chlorophenol (p-CP), and finally to phenol (P). The induction of ultrasound during the preparation of Pd/Fe nanoparticles further enhanced the removal efficiency of 2,4-DCP, as a result, the phenol production rates increased from 65% (in the absence of ultrasonic irradiation) to 91% (in the presence of ultrasonic irradiation) within 2h. Our data suggested that the dechlorination rate was dependent on various factors including Pd loading percentage over Fe(0), Pd/Fe nanoparticles availability, temperature, mechanical stirring speed, and initial pH values. Up to 99.2% of 2,4-DCP was removed after 300min reaction with these conditions: Pd loading percentage over Fe(0) 0.3wt.%, initial 2,4-DCP concentration 20mgL(-1), Pd/Fe dosage 3gL(-1), initial pH value 3.0, and reaction temperature 25°C. The degradation of 2,4-DCP followed pseudo-first-order kinetics reaction and the apparent pseudo-first-order kinetics constant was 0.0468min(-1).
    Ultrasonics Sonochemistry 12/2012; · 3.52 Impact Factor
  • Jiang Xu, Jie Tang, Shams Ali Baig, Xiaoshu Lv, Xinhua Xu
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    ABSTRACT: The Pd/FeFe(3)O(4) nanocomposites showed higher dechlorination efficiency of 2,4-dichlorophenol (2,4-DCP) rather than bare Pd/Fe nanoparticles in the batch dechlorination experiments. nFe(3)O(4) provided a convenient way to recycle the nanocomposites with an external magnetic field and significantly enhanced 2,4-DCP dechlorination. 2.0gL(-1)nFe(3)O(4) was the optimal dosage in the presence of 3gL(-1) Pd/Fe nanoparticles in our system, removing 76.4% 2,4-DCP within 5h in the aqueous environment. This was much higher than bare Pd/Fe nanoparticles (35.8%), 1.0gL(-1)nFe(3)O(4) (58.0%) and 2.5gL(-1)nFe(3)O(4) (66.3%) employed under the same conditions. However, excessive nFe(3)O(4) (3.0gL(-1)) partially overlapped on Pd/Fe nanoparticles to obstruct their contact with 2,4-DCP, and then 2,4-DCP removal efficiency was dropped to 7.4%. Efficiencies of dechlorination and phenol formations were increased significantly when the amount of Pd increased, whereas the highest 2,4-DCP removal efficiency was observed 98.2% at 0.20wt% Pd loading. Moreover, SO(4)(2-) would also inhibit the dechlorination while Cu(2+), Ni(2+) and Fe(2+) enhanced the dechlorination of 2,4-DCP by Pd/FeFe(3)O(4) nanocomposites. The nanocomposites showed stable catalytic activity, fairly good mechanic stability, and promising to recycle during the process.
    Journal of hazardous materials 11/2012; · 4.14 Impact Factor
  • Zhen Zhang, Sai Hu, Shams Ali Baig, Jie Tang, Xinhua Xu
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    ABSTRACT: Ni/Fe bimetallic nanoparticles were synthesized for treatment of Aroclor 1242, in order to evaluate their applicability for in situ remediation of groundwater and soil contaminated by polychlorinated biphenyls (PCBs). Our experimental results indicate that the total PCB concentration changed during the reduction of 3,5-dichlorobiphenyl (PCB 14), and biphenyl was produced as the final product. Initially, the concentration of 3-chlorobiphenyl (PCB 2) was increased in the prophase reaction and then slowly decreased, suggesting that Aroclor 1242 was first adsorbed by Ni/Fe nanoparticles, and then, the higher chlorinated congeners were converted gradually to the lower chlorinated congeners, and finally to biphenyl. The dechlorination efficiency of Aroclor 1242 reached approximately 80% at 25°C in just 5h, then 95.6% and 95.8% in 10h and 24h, respectively. The study revealed that high Ni/Fe nanoparticle dosage and high Ni content in Ni/Fe nanoparticles favor the catalytic dechlorination reaction. Moreover, a comparison of different types of catalysts on the dechlorination of Aroclor 1242 indicated that Ni/Mg and Mg powders showed a greater reactivity than Ni/Fe and Fe nanoparticles, respectively.
    Journal of Colloid and Interface Science 07/2012; 385(1):160-5. · 3.17 Impact Factor
  • Shams Ali A Baig, Xinhua Xu, Rashid Khan
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    ABSTRACT: In mid-July 2010 flash flooding in Pakistan destroyed the basic water, environmental sanitation and livelihood infrastructures in 82 districts. Two months later, the local press of Swat (northern Pakistan) reported that several residents of Marghazar town became ill and were hospitalized after drinking contaminated water. A non-governmental organization (Oxfam GB) team took action to determine the causes of this incident and analyzed the community drinking water supply. Standard methods were used to analyze six physio-chemical and four microbiological water quality parameters at five selected sampling locations in the water supply system. The samples from sites numbers (SN)02, 03, 04 and 05 were found to be microbiologically unfit for drinking due to the presence of Escherichia coli , Shigella , Salmonella and Staphylococcus aureus (range 18-96 ± 14 cfu/100 mL). However, the pH, conductivity, total dissolved solid, total hardness as calcium carbonate and nitrate as NO<sub>3</sub>-2 of all the samples were within WHO permissible limits. Higher turbidities were recorded at SN04 and 05 of 6 ± 0.23 and 9 ± 1.23, respectively. Quantitative results revealed the presence of pathogenic organisms and water quality risk factors due to the damaged water and environmental sanitation infrastructure. Continued water quality monitoring, the application of household based disinfectants, and healthy domestic hygiene practices are highly recommended in similar circumstances.
    Rural and remote health 07/2012; 12(3):2196. · 0.98 Impact Factor
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    Journal of Applied Sciences in Environmental Sanitation. 07/2012; 7(1):49-54.
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    ABSTRACT: Several heavy metals, including Cu(2+), Ni(2+), Pb(2+), and Zn(2+), were investigated in simulated desulfurization solutions to evaluate their interferences with Hg(2+) during the reaction with dithiocarbamate type chelating resin (DTCR). Appropriate DTCR dosage and the effect of pH were also explored with respect to restoration of high Hg(2+) precipitation efficiency and reduction of mercury concentrations. The experimental results suggested that increasing heavy metal concentration inhibited Hg(2+) precipitation efficiency to a considerable extent and the inhibition order of the four heavy metals was Cu(2+)>Ni(2+)>Pb(2+)>Zn(2+). However, the coordination ability was closely related to the configuration and the orbital hybridization of each metal. In the cases of Cu(2+) and Pb(2+), increased DTCR dosage was beneficial to Hg(2+) precipitation, which could lay the foundation of practical applications of DTCR dosage for industrial wastewater treatment. The enhanced Hg(2+) precipitation performance seen for increasing pH might have come from the deprotonation of sulfur atoms on the DTCR functional groups and the formation of metal hydroxides (M(OH)(2), M=Cu, Pb, Hg).
    Journal of hazardous materials 03/2012; 217-218:224-30. · 4.14 Impact Factor
  • Zhen Zhang, Xiaoshu Lv, Shams Ali Baig, Xinhua Xu
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    ABSTRACT: The catalytic dechlorination of 2,4-dichlorophenol (2,4-DCP) by Ni/Fe bimetallic nanoparticles in the presence of humic acid (HA) was investigated in order to understand their applicability for in situ remediation of groundwater. 2,4-DCP was catalytically dechlorinated to form the final products – phenol (P) via two intermediates, o-chlorophenol (o-CP) and p-chlorophenol (p-CP). It was demonstrated that the carbon mass balances during the dechlorination were between 84% and 92%, and other carbons were adsorbed on the surface of Ni/Fe bimetallic nanoparticles. The experimental results suggest that HA competed for reaction sites on the Ni/Fe bimetallic nanoparticles with 2,4-DCP, and thus reduced the efficiency and rate of the dechlorination of 2,4-DCP. The catalytic degradation slowed down as the increase of HA in solution, and when HA's concentrations were 0, 10, 20 and 30 mg L, the maximum concentrations of o-CP were 0.025, 0.041, 0.039 and 0.034 mM in 10, 30, 30 and 30 min, respectively. High Ni content, low initial pH value, high Ni/Fe nanoparticles’ dosage and high temperature favoured the catalytic dechlorination of 2,4-DCP. The experimental results show that no other intermediates were generated besides Cl, o-CP, p-CP and P during the catalytic dechlorination of 2,4-DCP.
    Journal of Experimental Nanoscience - J EXP NANOSCI. 01/2012;
  • Hongyi Zhou, Jian Han, Shams Ali Baig, Xinhua Xu
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    ABSTRACT: This paper describes the synthesis of sodium carboxymethyl cellulose (CMC)-stabilized Pd/Fe nanoparticles and their applications to the dechlorination of 2,4-dichlorophenoxyacetic acid (2,4-D) under controlled laboratorial conditions. For this purpose batch mode experiments were conducted to understand the effects of CMC on the surface characteristics of Pd/Fe nanoparticles, optimum removal of 2,4-D and other surface interactions mechanism. Our experimental results demonstrated considerable enhancements in particle stability and chemical reactivity with the addition of CMC to Pd/Fe nanoparticles. Transmission electron microscopy (TEM) analysis indicated that CMC-stabilized Pd/Fe nanoparticles were well dispersed, and nanoparticles remained in suspension for days compared to non-stabilized Pd/Fe nanoparticles precipitated within minutes. The isoelectric point (IEP) of the nanoparticles shifted from pH 6.5 to 2.5, suggesting that CMC-stabilized Pd/Fe nanoparticles were negatively charged over a wider pH range. Our batch experiments demonstrated that CMC-stabilized Pd/Fe nanoparticles (0.6 g Fe L(-1)) were able to remove much higher levels of 2,4-D with only one intermediate 2-chlorophenoxyacetic acid (2-CPA) and the final organic product phenoxyacetic acid (PA), than non-stabilized Pd/Fe nanoparticles or microsized Pd/Fe particles. The removal percentage of 2,4-D increased from 10% to nearly 100% as the reaction pH decreased from 11.5 to 2.5. The optimal CMC/Fe mass ratio for the dechlorination of 2,4-D was determined to be 5/1, and the removal of 2,4-D was evidently hindered by an overdose of CMC.
    Journal of hazardous materials 12/2011; 198:7-12. · 4.14 Impact Factor
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    ABSTRACT: The devastating earthquake of 2005 severely damaged over 4000 water and sanitation schemes in northern Pakistan. The present study aimed at testing a low cost household sand filter (HSF) in treating low quality drinking water in disaster-hit areas of northern Pakistan. Two villages were randomly selected for practical demonstration of a low cost drinking water treatment system in earthquake affected areas. The on-site performance of HSF was monitored during the operational period. The data was collected on people perceptions of water quality and handling of the household sand filter (HSF) through in depth focus group discussions, questionnaire and interviews. The results showed that pre-treatment values of drinking water for Escherichia coli, total coliforms and turbidity were 101 cfu/100 ml, 73 cfu/100 ml and turbidity 44 and 16 NTU, respectively. After HSF operation for 10 days, 97% reduction in E. coli, total coliforms and turbidity was evidenced. More than 67% of the respondents perceived turbidity as a prime water quality issue responsible for ill health consequences. It was concluded that the designed HSF was efficient in improving drinking water quality for illiterate communities and its success and dissemination to poor communities were prone to locally available construction materials.Research Highlights► Development of a low-cost sand filter. ► Its practical demonstration in earth quake affected areas. ► Assessment of people perceptions and beliefs regarding water quality, handling and the household sand filter (HSF). ► Water quality results after 10 days operation of HSF showed above 97% of E. coli, total coliforms and turbidity reductions.
    Desalination. 01/2011; 273:316-320.
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    ABSTRACT: The removal of microbial and physico-chemical contaminants was investigated using an innovative biosand filter (BSF) containing three combinations of coniferous pinus bark biomass (CPBB), i.e. 1cm (treatment 2), 2.5cm (treatment 3) and 5cm (treatment 4). The efficiency of BSF was assessed in batch mode experiments and the comparative reductions of contaminants were monitored over the control treatment (1) at temperature range of 1–15°C for 90days. Standard methods were used to analyze 9 operating, physico-chemicals and biological water quality parameters of pre-and post-water filtration samples after 15 days interval. The results showed mean 93±2% and 95±3% reductions of Eischerichia coli and total coliforms, respectively, for BSF containing the highest depth of CPBB (5cm), whereby 100% removal was observed during the treatment time T30 to T45 days. The general affinity sequence for E. coli, total coliforms and turbidity removal in the four treatments was: BSF with 5cm CPBB>BSF with 2.5cm CPBB>BSF with 1cm CPBB>Control. It was concluded that modified BSF with additional adsorbent of locally available CPBB is a very good decentralized treatment option for drinking water.
    Ecological Engineering - ECOL ENG. 01/2011; 37(11):1842-1848.
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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. 223:192–199.

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