Biosorption of Cadmium and Copper From Aqueous Samples by Brachyura Carapace

Abstract

Studies indicate that copper and cadmium discarded by electroplating, tanning, alloy and storage battery industries can be harmful to aquatic organisms, then they must be removed from the effluents to protect water resources. Adsorption-based techniques has shown to be efficient in the treatment of such effluents. Besides activated charcoal, other adsorbents have potential in the removal of metals such as from by-products of agricultural, industrial and fishing activities. Brachyurans are considered a by-catch in shrimp trawl fisheries, and thus their carapace usage may decrease the environmental impact associated to its disposal. The objective of this study was to characterize the material and elucidate its adsorptive properties to remove metal ions from aqueous medium. By Fourier Transform in Infrared Region (FTIR) spectroscopy and 13C Nuclear Magnetic Resonance analyses (13C NMR), it was possible to identify important functional groups to act as metals adsorption sites. Point of Zero Charge (PZC) was verified at a pH of 10.14. The optimal pH was obtained around 2.0. Furthermore, the equilibrium adsorption of Cu(II) and Cd(II) was both achieved after 10 min of reaction, fitting both adsorption isotherms into pseudo-second order kinetic model. The maximum adsorption capacities were 0.70 mmol g-1 (or 44.48 mg g-1) for copper and 0.43 mmol g-1 (or 48.33 mg g-1) for cadmium. The experimental data were evaluated in terms of the Langmuir and Freundlich models, and the first model better described the adsorptive behaviour towards both metal species. According to these results, this potential biosorbent can be applied in Solid Phase Extraction.