Somak Chatterjee

Adsorptive removal of arsenic from groundwater using a novel high flux polyacrylonitrile (PAN)–laterite mixed matrix ultrafiltration membrane

A flat sheet mixed matrix membrane, made of polyacrylonitrile (PAN) copolymer, impregnated with laterite, was fabricated for the removal of arsenic from water. The permeability and molecular weight cut-off of the selected membrane were 3.4 × 10−11 m s−1 Pa and 48 kDa, respectively. Morphological analysis showed macrovoids constricted by laterite particles. Surface characteristics assessed by atomic force microscopy revealed the increase in roughness with laterite concentration. The presence of different forms of iron oxide (laterite) and nitrile groups (polyacrylonitrile) in membrane M25 was confirmed by X-ray diffraction. Incorporation of arsenic within the membrane matrix was demonstrated by subsequent lowering of transmittance peaks at different wavelengths of FTIR. Maximum adsorption capacity of the selected membrane was 1.4 mg g−1 at 298 K. Under the optimum operating conditions, the pristine mixed matrix membrane resulted in a filtrate with a concentration below 10 μg l−1 for 17 hours in cross flow mode with a 0.01 m2 filtration area. The stability of the membrane was demonstrated for three regeneration cycles. The effect of pH and coexisting anions like phosphate, sulphate, carbonate and bicarbonate on the removal efficiency of arsenic was studied. The performance of the membrane in the presence of arsenic-contaminated groundwater was also tested.

Application of novel, low-cost, laterite-based adsorbent for removal of lead from water: Equilibrium, kinetic and thermodynamic studies.

ABSTRACT Contamination of groundwater by carcinogenic heavy metal, e.g., lead is an important issue and possibility of using a natural rock, laterite, is explored in this work to mitigate this problem. Treated laterite (TL- prepared using hydrochloric acid and sodium hydroxide) was successfully utilized for this purpose. The adsorbent was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX), and Fourier Transform Infrared Spectroscopy (FTIR) to highlight its physical and chemical properties. Optimized equilibrium conditions were 1 g L−1 adsorbent concentration, 0.26 mm size and a pH of 7 ± 0.2. Monolayer adsorption capacity of lead on treated laterite was 15 mg/g, 14.5 and 13 mg g−1 at temperatures of 303 K, 313 K and 323 K, respectively. The adsorption was exothermic and physical in nature. At 303 K, value of effective diffusivity of (De) and mass transfer co-efficient (Kf) of lead onto TL were 6.5 × 10−10 m2/s and 3.3 × 10−4 m/s, respectively (solved from shrinking core model of adsorption kinetics). Magnesium and sulphate show highest interference effect on the adsorption of lead by TL. Efficacy of the adsorbent has been verified using real-life contaminated groundwater. Thus, this work demonstrates performance of a cost-effective media for lead removal.

A socio-economic study along with impact assessment for laterite based technology demonstration for arsenic mitigation

Arsenic contamination mitigation technologies have been adsorption-based, but the most widely-used and traditionally available adsorbents suffered inherent limitations, including cost infeasibility and problems associated with regeneration and disposal of the spent adsorbent. The present technology is based on indigenously developed activated laterite prepared from the naturally and abundantly available material, and can hence easily be scaled up for community usage and large scale implementation. The total arsenic removal capacity is 32.5mg/g, which is the highest among all naturally occurring arsenic adsorbents. A major issue in earlier adsorbents was that during regeneration, the adsorbed arsenic would be released back into the environment (leaching), and would eventually contaminate the groundwater again. But the adsorbent in this filter does not require regeneration during its five-year lifespan and does not leach upon disposal. An attempt is made to test and demonstrate the practical implementation of the technology - its effectiveness and viability in three community (primary schools - one in Malda and two in north 24 Parganas, West Bengal, India) and 20 household filters, catering to over 5000 people in different areas of West Bengal exposed to high arsenic contamination of groundwater (ranging from 0.05 to 0.5mg/l). The work also focuses on the social impact of the real life technological solution on the lives on the affected people in the worst hit arsenic affected communities, perhaps the greatest public health risk emergency of the decade.

Novel carbonized bone meal for defluoridation of groundwater: Batch and column study

ABSTRACT Low cost naturally available bone meal was carbonized and its fluoride adsorption capacity was explored. Carbonized bone meal (CBM) produced at 550°C, 4 h carbonization time and a heating rate of 60°C/min, showed fluoride adsorption capacity of 14 mg g−1. Adsorbent was characterized using scanning electron microscopy, X-ray diffraction, X-ray fluoroscence, thermogravimetric analysis and Fourier transform infrared spectroscopy to highlight its physical and chemical properties. Best fluoride uptake capacity was observed for 0.2 mm particle size, 7 g L−1 adsorbent concentration and at pH 6.5. Fluoride uptake was endothermic and chemisorption in nature. Effective diffusivity and mass transfer coefficient were obtained as 6 × 10−11 m2 s−1 and 9 × 10−5 m s−1 from shrinking core model. Sulphate and carbonate showed the highest interference effect on adsorption of fluoride by CBM. Maximum desorption was observed at basic pH (pH 12). Fixed bed study was performed and effect of different parameters (bed height, inlet flow rate and initial concentration) was investigated. Efficiency of the adsorbent using real life fluoride contaminated groundwater solution was also observed.