Biosorption of arsenic in drinking water by submerged plant: Hydrilla verticilata

Abstract

To evaluate the biosorption efficacy of submerged aquatic plant Hydrilla verticilata for arsenic uptake from drinking water. H. verticillata, a submerged aquatic plant was utilized successfully for arsenic uptake from aqueous solution. Batch studies with various parameters viz. pH, sorbent dose, contact time, initial metal ion concentration, and temperature were carried out. Data were utilized to plot Lagergren graph along with pseudo-second-order graphs for kinetic studies to estimate the removal efficacy and to determine the nature of reaction. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) have been performed for characterization of metals on biomass. The study showed 96.35 % maximum absorption of arsenic by H. verticilata at initial concentration of 100 ppb with 0.5 g of biomass/100 ml for 5 h contact time at pH 6.0 with 150 rpm agitation rate. Data followed Langmuir isotherm showing sorption to be monolayer on homogeneous surface of biosorbent. The negative values of ΔG° indicated spontaneous nature; whereas ΔH° indicates exothermic nature of system and negative value of ∆S° entropy change correspond to a decrease in the degree of freedom to the adsorbed species followed by pseudo-second-order adsorption kinetics. FTIR and SEM results showed apparent changes in functional group regions after metal chelation and the changes in surface morphology of biosorbent. This is a comparatively more effective, economic, easily available, and environmentally safe source for arsenic uptake from solution due to its high biosorption efficacy than other biosorbents already used.