Adsorption Efficacy of Polymerized Seed Composite for Remediation of Heavy Metals and Physico Chemical Parameters of Water

Abstract

The excess quantity of heavy metals and elevated level of physico-chemical parameters of water has been indicating the degrading quality of water systems. Unfortunately, the application of conventional techniques used for water remediation is constrained due to their high installation cost, working expenditure, sludge formation, and partial removal of metals. Biosorption has emerged as the most appropriate, economically viable and sustainable technique owing to its facile implement ability, environment benign scalability and utilization of bio-origin matter. The present work is focused on the preparation of seed composite (Moringa oleifera and Leucaena leucocephala) for removing heavy metals [Pb (II), Cd (II), Cr (III), Ni (II), Cr (VI), As (III) and As (V)] and reducing physico-chemical parameters [pH, alkalinity, hardness, TDS, BOD, COD and electrical conductivity] of water. The native biosorbent has been tailored using the graft copolymerization process to enhance efficiency towards the cationic and anionic ions. The modified biosorbents are analyzed by different characterization techniques [SEM, EDX, FTIR, BET, TGA and zeta potential analysis]. Batch experimental conditions were standardized as follows: contact time (30 min), biosorbent dose (0.25 g), initial concentration of metal ions (25 mg L-1), sample volume (500 mL), temperature (298 K) and pH [2.5 for As (V) and Cr (VI), 6.5 for Pb (II), Cd (II), Cr (III) and Ni (II) and 7.5 for As (III)]. IA-g-SC and PEDA-g-SC has been found as most efficient having biosorption performance [Pb (II): 99.72%; Cd (II): 98.89%, Cr (III): 95.97% and Ni (II): 92.85%] and [Cr (VI): 98.75%; As (III): 89.25% and As (V): 96.61%] respectively. Biosorption data has been analyzed by equilibrium isotherm, kinetic models and thermodynamic studies. The data is well fitted with Langmuir isotherm and pseudo second order kinetic model. The intra-particle diffusion study also explains the biosorption process. Thermodynamic study shows the process is feasible and exothermic in nature. The spent biosorbents can be regenerated and reused which makes the process economical. AA-g-SC and IA-g-SC is also effective in reducing the water parameters. Thus, the biosorbents can be used in the pre-treatment of water before large scale chemical treatment particularly for sub-urban and rural area. newline