Removal of copper contamination from simulated wastewater using chitosan and shrimp waste: Equilibrium analysis

Abstract

This study addressed copper removal from aqueous solution using unprocessed shrimp tail shell waste (STW) with comparison to removal by chitosan derived from shrimp shell. The use of a copper ion selective electrode enabled continuous copper concentration measurement and determination of the STW mass-time relationship needed to achieve the USEPA Maximum Contaminant Level for copper as a function of adsorbent dose. Copper removal using chitosan produced a blue solid without surface morphology changes, consistent with an adsorption or ion exchange mechanism. Calcium carbonate in the STW was essential for copper removal by the formation of a green copper-containing deposit primarily on the exposed edges of the ground shrimp solids and an increase in calcium concentration and pH in the treated solution. The systems reached equilibrium over several days. Equilibrium data were fitted to the Freundlich, Langmuir, Temkin, Sips, and B-E-T isotherms and the Freundlich model fit the data well. Raw STW, cooked STW, and chitosan with particle sizes ranging from 425 to 850 µm gave a maximum copper loading of 184 mg/g, 170 mg/g, and 129 mg/g, respectively. Both raw and cooked STW had higher copper capacities than commercial chitosan and provide a low cost and environmentally friendly adsorbent. Comparison of small particle size (< 425 µm) adsorbents after six hours showed that raw STW had double the copper loading of chitosan. Small STW achieved greater than 97.4% copper removal from a 50 mg/L copper solution and reached the MCL in less than one hour for 1.5 g/L loadings.