Kinetic Study of the Removal of Residual Copper(II) on Activated Carbon and Alternative Adsorbents

The objective of this study was to adjust the kinetic data of the adsorption of residual copper(II) to the pseudo-first-order model, pseudo-second-order model, intraparticle diffusion and Elovich. The waste contained copper(II), generated in the analysis of protein determination at Departamento de Ciencia dos Alimentos, of Universidade Federal de Lavras, Brazil. The concentration of copper(II) was 11.39 mg L-1, determined by atomic absorption spectrometry, and the value found for pH was 13. Adsorption was studied employing kaolinite, advanced oxidation process (AOP) sludge and cotton lint as alternative adsorbents. Results of the percentage removal of copper(II) were compared with adsorption onto commercial activated carbon. The adsorption process was conducted at room temperature (25 ± 1°C), using 0.10 g of adsorbent and 10.0 mL of waste. The percentage removal of residual copper(II) obtained for the adsorbents active carbon, kaolinite, AOP sludge and cotton lint was 95.1, 94.5, 77.2 and 82.1%, respectively. The results showed that kaolinite was the most adequate alternative adsorbent. In this case, the final concentration of copper(II) was lower than the allowed by the Brazilian law for effluent discharge, which is 1.0 mg L-1. The adjusted results showed that the model proposed by Elovich was more adequate for removal onto active carbon and cotton lint while, for adsorption onto kaolinite and AOP sludge, the most adequate was the pseudo-second-order model.