R & D Abstracts




2016-2017

 1.Removal of arsenic(III) from water by magnetic binary oxide particles (MBOP): Experimental studies on fixed bed column

     Magnetic binary oxide particles (MBOP) were prepared by template method using chitosan in the laboratory for the removal of As(III) from water. The prepared MBOP has super paramagnetic property which is sufficient for magnetic separation. Column study was performed at two different flow rates of 2.0 ml/min and 5.0 ml/min and comparison was made with regenerated MBOP, commercial activated carbon and commercial activated alumina. It is observed that fresh MBOP has higher breakthrough time and capacity than regenerated MBOP by a factor of 1.25 and 1.37 respectively. In Logit method, the values of K (adsorption rate constant) and N (adsorption capacity coefficient) were obtained as 0.2066 (L/mg h) and 1014 (mg/L) for 5.0 ml/min flow rate. All the drinking water parameters are within the limit of BIS 10500-2012. Toxicity characteristic leaching procedure (TCLP) and semi dynamic tests were performed for the mix ratios of 01:02:01, 01:02:05 and 01:02:10 and were found safe for the disposal.

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 2.Arsenic contamination in agricultural soils of Bengal deltaic region of West Bengal and its higher assimilation in monsoon rice

     In the Bengal deltaic region, the shallow groundwater laced with arsenic is used for irrigation frequently and has elevated the soil arsenic in agricultural soil. However, the areas with seasonal flooding reduce arsenic in top layers of the soils. Study shows arsenic accumulation in the deeper soil layers with time in the contaminated agricultural soil (19.40 ± 0.38 mg/kg in 0–5 cm, 27.17 ± 0.44 mg/kg in 5–10 cm and 41.24 ± 0.48 mg/kg in 10–15 cm) in 2013 whereas depletion in 2014 and its buildup in different parts of monsoon rice plant in Nadia, India. Principal Component Analysis and Cluster Analysis were performed, and Enrichment Factor was calculated to identify the sources of arsenic in the soil. Potential Ecological Risk was also calculated to estimate the extent of risk posed by arsenic in soil, along with the potential risk of dietary arsenic exposure. Remarkably, the concentration of arsenic detected in the rice grain showed average value of 1.4 mg/kg in 2013 which has increased to 1.6 in 2014, both being above the permissible limit (1 mg/kg). These results indicate that monsoon flooding enhances the infiltration of arsenic in the deeper soil layer, which lead to further contamination of shallow groundwater.

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 3.Arsenic(V) removal using an amine-doped acrylic ion exchange fiber: Kinetic, equilibrium, and regeneration studies

     This study investigates As(V) removal from aqueous solutions using a novel amine-doped acrylic ion exchange fiber. The amine doping reaction was confirmed using FT-IR, and the surface of the fiber was characterized using FEG-SEM. The synthesis process was completed within 60 min using an AlCl3·6H2O catalyst at 100 °C, and the resulting in a fiber with an ion exchange capacity of 7.5 meq/g. The removal efficiency of the A-60 fiber was affected by the solution pH, and the efficiency was optimum at pH 3.04. As(V) adsorption on the fiber was rapid in the first 20 min and reached equilibrium in 60 min. As(V) removal followed pseudo-first-order kinetics, and the Redlich-Peterson adsorption isotherm model provided the best fit of the equilibrium data. The fiber has an As(V) adsorption capacity (qe) of 205.32 ± 3.57 mg/g, which is considerably higher than literature values and commercial adsorbents. The removal efficiency of the fiber was above 83% of the initial value after nine regeneration cycles.

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 4.Comparative and competitive adsorption of Pb(II) and Cu(II) using tetraethylenepentamine modified chitosan/CoFe2O4particles

     In this paper, tetraethylenepentamine (TEPA) modified chitosan/CoFe2O4 particles were prepared for comparative and competitive adsorption of Cu(II) and Pb(II) in single and bi-component aqueous solutions. The characteristics results of SEM, FTIR and XRD indicated that the adsorbent was successfully fabricated. The magnetic property results manifested that the particles with saturation magnetization value of 63.83 emu g−1 would have a fast magnetic response. The effects of experimental parameters including contact time, pH value, initial metal ions concentration and coexisting ions on single and bi-component adsorption were investigated. The results revealed that the adsorption kinetic was followed pseudo-second-order kinetic model, indicating that chemical adsorption was the rate-limiting step. Sorption isotherms were also determined in single and bi-component solutions with different mass ratio of Cu(II) to Pb(II) (Cu(II)/Pb(II)) and fitted using Langmuir and Freundlich isotherm models. A better fit for Cu(II) and Pb(II) adsorption were obtained with Langmuir model, with a maximum sorption capacity of 168.067 and 228.311 mg g−1 for Cu(II) and Pb(II) in single component solution, 139.860 and 160.256 mg g−1 in bi-component solution (Cu(II)/Pb(II) = 1:1), respectively. The present results suggest that TEPA modified chitosan/CoFe2O4 particles are feasible and satisfactory adsorbent for efficient removal of Cu(II) and Pb(II) ions.

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 5.Removal of cadmium (II) from aqueous solution: A comparative study of raw attapulgite clay and a reusable waste–struvite/attapulgite obtained from nutrient-rich wastewater

     In this study, raw attapulgite (APT) and a novel adsorbent, struvite/attapulgite (MAP/APT) obtained from nutrient-rich wastewater treated by MgO modified APT, were applied as the absorbent for Cd(II) ion removal from aqueous solution. The two adsorbents were characterized by BET, SEM-EDS, XRD, FT-IR. Raw APT and MAP/APT separately presented the maximum Cd(II) adsorption capacities of 10.38 mg/g and 121.14 mg/g at pH of 5.45. The Cd(II) adsorption on raw APT and MAP/APT could be well fitted by Freundlich isotherm and Langmuir isotherm, respectively. Pseudo-second order equation was able to properly describe the kinetics of Cd(II) adsorption by raw APT and MAP/APT. The calculated thermodynamic parameters indicated that Cd(II) adsorption onto raw APT and MAP/APT were spontaneous and endothermic. An economic evaluation revealed that the treatment costs of the adsorption process by raw APT and MPA/APT were 0.013 $ per 1000 mg Cd and 0.004 $ per 1000 mg Cd, respectively.

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 6.Biosorption of Ag(I) from aqueous solutions by Klebsiella sp. 3S1

     This study investigated the potential ability of Klebsiella sp. 3S1 to remove silver cations from aqueous solutions. The selected strain is a ubiquitous bacterium selected from among several microorganisms that had been isolated from wastewaters. To optimise the operating conditions in the biosorption process, a Rotatable Central Composite Experimental Design was developed establishing pH, temperature and biomass concentration as independent variables. Interaction mechanisms involved were analysed through kinetic and equilibrium studies. The experimental results suit pseudo-second order kinetics with two biosorption stages, being the first almost instantly. The Langmuir equilibrium model predicted a maximum capacity of biosorption (q) of 114.1 mg Ag/g biomass. The study of the mechanisms involved in the biosorption was completed by employing advanced techniques which revealed that both bacterium-surface interactions and intracellular bioaccumulation participate in silver removal from aqueous solutions. The ability of Klebsiella sp. 3S1 to form silver chloride nanoparticles with interesting potential applications was also discussed.

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 7.Chemical removal of nitrate from water by aluminum-iron alloys

     Zero-valent iron has been intensively investigated in chemical reduction of nitrate in water, but the reduction requires acidic or weak acidic pH conditions and the product of the reduction is exclusively ammonium, an even more toxic substance. Zero-valent aluminum is a stronger reductant than iron, but its use for the reduction of aqueous nitrate requires considerably alkaline pH conditions. In this study, aluminum-iron alloys with an iron content of 10%, 20% and 58% (termed Al-Fe10, Al-Fe20 and Al-Fe58, respectively) were investigated for the reduction of aqueous nitrate. Al-Fe alloys were efficient to reduce nitrate in water in an entire pH range of 2–12 and the reduction proceeded in a pseudo-first order at near neutral pH conditions. The observed reaction rate constant (Kobs) of Al-Fe10 was 3 times higher than that of Fe and the Kobs of Al-Fe20 doubled that of Al-Fe10. The nitrogen selectivity of the reduction by Al-Fe10, Al-Fe20 and Al-Fe58 was 17.6%, 23.9% and 40.3%, respectively at pH 7 and the nitrogen selectivity by Al-Fe20 increased from 18.9% at pH 2–60.3% at pH 12. The enhanced selectivity and reactivity of Al-Fe alloys were likely due to the presence of an intermetallic Al-Fe compound (Al13Fe4).

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 8.Removal of mercury from gold mine effluents using Limnocharis flava in constructed wetlands

     Phytoremediation has received increased attention over the recent decades, as an emerging and eco-friendly approach that utilizes the natural properties of plants to remediate contaminated water, soils or sediments. The current study provides information about a pilot–scale experiment designed to evaluate the potential of the anchored aquatic plant Limnocharis flava for phytoremediation of water contaminated with mercury (Hg), in a constructed wetland (CW) with horizontal subsurface flow (HSSF). Mine effluent used in this experiment was collected from a gold mining area located at the Alacran mine in Colombia (Hg: 0.11 ± 0.03 μg mL−1) and spiked with HgNO3 (1.50 ± 0.09 μg mL−1). Over a 30 day test period, the efficiency of the reduction in the heavy metal concentration in the wetlands, and the relative metal sorption by the L. flava, varied according to the exposure time. The continued rate of removal of Hg from the constructed wetland was 9 times higher than the control, demonstrating a better performance and nearly 90% reduction in Hg concentrations in the contaminated water in the presence of L. flava. The results in this present study show the great potential of the aquatic macrophyte L. flava for phytoremediation of Hg from gold mining effluents in constructed wetlands.

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 9.Effective mercury(II) bioremoval from aqueous solution, and its electrochemical determination

     This work proposed mercury elimination using agricultural waste (Allium Cepa L.). The biomass removed 99.4% of mercury, following a pseudo-second order kinetics (r2 = 0.9999). The Langmuir model was adequately fitted to the adsorption isotherm, thereby obtaining the maximum mercury adsorption capacity of 111.1 ± 0.3 mg g−1. The biomass showed high density of strong mercury chelating groups, thus making it economically attractive. Also, the implementation of a mercury-selective electrode for continuous determination in real time is proposed; this electrode replaces techniques like atomic absorption spectroscopy, thus it can be applied to real time studies. This work therefore presents a new perspective for removing mercury(II) from contaminated water for environmental remediation.

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 10.Nitric oxide removal by combined urea and FeIIEDTA reaction systems

     (NH2)2CO as well as FeIIEDTA is an absorbent for simultaneous desulfurization and denitrification. However, they have their own drawbacks, like the oxidation of FeIIEDTA and the low solubility of NO in urea solution. To overcome these defects, A mixed absorbent containing both (NH2)2CO and FeIIEDTA was employed. The effects of various operating parameters (urea and FeIIEDTA concentration, temperature, inlet oxygen concentration, pH value) on NO removal were examined in the packed tower. The results indicated that the NO removal efficiency increased with the decrease of oxygen concentration as well as the increase of FeIIEDTA concentration. The NO removal efficiency had little change with a range of 25–45 °C, and sharply decreased at the temperature of above 55 °C. The NO removal efficiency initially increases up to the maximum value and then decreases with the increase of pH value as well as the raise of urea concentration. In addition, the synergistic mechanism of (NH2)2CO and FeIIEDTA on NO removal was investigated. Results showed that urea could react with FeIIEDTA-NO to produce FeIIEDTA, N2, and CO2, and hinder oxidation of FeIIEDTA. Finally, to evaluate the effect of SO32− on NO removal, a mixed absorbent containing FeIIEDTA, urea, and Na2SO3 was employed to absorb NO. The mixed absorbent could maintain more than 78% for 80 min at 25 °C, pH = 7.0, (NH2)2CO concentration of 5 wt%, FeIIEDTA concentration of 0.02 M, O2 concentration of 7% (v/v), and Na2SO3concentration of 0.2 M.

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 11.Phosphate removal by lead-exhausted bioadsorbents simultaneously achieving lead stabilization

     Low-cost adsorbents have been continuously developed for heavy metal removal, but little information is available concerning the follow-up treatment of the toxic metal-laden adsorbents. In this study, an optional strategy was provided for the further treatment of heavy metal-impregnated low-cost adsorbents through employing them for phosphate retention. The enhancement of phosphate adsorption by the sorbed lead was first validated using several types of raw or modified waste biomass. Tea waste-supported hydrated manganese dioxide (HMO-TW) with the highest Pb sorption capability was then chosen to systematically evaluate phosphate retention. Phosphate adsorption onto lead-laden HMO-TW (HMO-TW(Pb)) was pH-insensitive with only slight decline at pH > 8.5, and was barely affected by competing anions owing to the specific surface precipitation mechanism. Moreover, no signs of lead leakage from HMO-TW(Pb) were observed during phosphate adsorption at a wide pH range (4.2–11.3) and high ion strength (0–250 mg L−1 NaNO3). The lead on HMO-TW(Pb) was greatly stabilized through phosphate retention, which also reduced the environmental risks of their following treatment such as solidification and landfill. Additionally, the phosphate adsorption onto HMO-TW(Pb) was quick (with equilibrium time < 60 min) and barely affected by temperature. Fixed-bed column test further suggested that HMO-TW(Pb) has practical applicability in efficient removal of phosphate from water.

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