Evaluation of macroalgal biomass for removal of heavy metal Arsenic (As) from aqueous solution

ABSTRACT Biosorption capacity of three common marine macroalgae viz., Ulva fasciata (green alga), Sargassum wightii (brown alga) and Gracilaria corticata (red alga) was evaluated with respect to the removal of the heavy metal, Arsenic (As) from aqueous solution. The influence of various parameters such as pH (2 to 10), biomass weight (0.5 to 3.0 g/L), initial metal ion concentration (2 to10 ppm/L) and contact time (30 to 150 minutes) on biosorption efficiencies were determined. Results indicated that the optimum pH was 6 for the removal of Arsenic by U. fasciata and S. wighti, while it was greater than 6 for G. corticata. The maximum removal of arsenic was 90.2% at biomass weight of 2g/100ml for S. wightii and G. corticata. The optimum arsenic (As) adsorption percentage was obtained at 90 minutes of contact time for initial metal ion concentration in all the three macroalgae biomass. The biosorption isotherms studies indicated that the biosorption of Arsenic follows the Langmuir and Freundlich models. The maximum biosorption capacity, q max, was 2.21mmol/g in G. corticata. The Freundlich Arsenic adsorption capacity was in the order of U. fasciata < S. wightii < G. corticata, which also suggested about the coexistence of the monolayer adsorption as well as heterogeneous surface conditions. The FTIR analysis for surface functional groups of unloaded algal biomass and arsenic loaded biomass revealed that the existence of amino, carboxyl, hydroxyl and carbonyl groups on the surface of biomass cells and the possible interaction between metal and functional groups. SEM micrograph of pretreated and Arsenic sorbed algal biomass showed morphological changes due to the exposure of heavy metal to the algae. These results led to refer that the macroalgal biomass could form a potential, eco-friendly, cost effective and safe alternative biosorbent for fine tuning of waste water treatment.