Groundwater defluoridation and disinfection using carbonized bone meal impregnated polysulfone mixed matrix hollow-fiber membranes

Abstract

Defluoridation and disinfection of groundwater have been attempted in this study, using carbonized bone meal (CBM) impregnated polysulfone based mixed matrix hollow fiber membrane. The membranes were characterized in terms of permeability, hydrophilicity, molecular weight cut off for different CBM concentrations. The membrane permeability was decreased from 5 × 10−10 m/Pa.s (without CBM) to 2.8 × 10-11 m/Pa.s with addition of 15 wt% CBM. Corresponding reduction in molecular weight cut off was from 85 kDa to 23 kDa. Variation of such properties were corroborated by the scanning electron micrographs of the prepared membranes that showed the membrane morphology became dense due to CBM addition in the polymer matrix. However, membrane hydrophilicity became more pronounced. In addition, the surface roughness of the prepared membranes was increased facilitating the adsorptive properties. The maximum fluoride adsorption capacity of the hollow fibers with 15 wt% CBM was observed to be 5 mg/g. Breakthrough studies were conducted for the membranes in cross flow filtration mode that showed a fresh membrane (area: 0.029 m2) can filter fluoride contaminated feed solution successfully for 24 h and 19 h, for the first and second regeneration cycles. For a real-life groundwater feed solution, the breakthrough time was observed to be 18 h. The bacterial concentration in the filtrate samples was found to be 0 CFU/ml, highlighting the antibacterial property of the prepared membranes.