Assessment of toxic copper(II) biosorption from aqueous solution by chemically-treated tomato waste

Abstract

Abstract Agricultural wastes or industrial wastes can be used as biosorbent with quite little processing when they are locally available in large quantities. A great number of studies were done to uptake copper(II) ion from aqueous solutions. The biosorption of copper(II) ion from aqueous solutions by hydrochloric acid treated tomato factory waste was investigated to identify metal ion removal efficiency of biosorbent for the first time in the literature. Proximate analysis of tomato waste was performed; also waste and biosorbent were characterized by applying Fourier transform infrared spectroscopy and elemental analyses. pH, biosorbent dosage, initial metal concentration, temperature and contact time effects were examined to determine optimum conditions of copper(II) uptake. According to the pH effect experiments, the maximum % metal removal was achieved at pH 8 as 92.08%. Optimum biosorbent dosage and initial copper(II) concentration were found as 0.2 g/50 mL solution and 50 ppm, respectively. Langmuir adsorption isotherm was found to best fit the adsorption data; and also reaction kinetics was determined to be appropriate to the pseudo-second order reaction model. Thermodynamic functions, the change of free energy (Δ G °), enthalpy (Δ H °) and entropy (Δ S °) of biosorption were calculated for copper(II) ion. The results showed that the biosorption of copper(II) ion on tomato waste biosorbent was exothermic at 293–313 K. Results of biosorption studies are in line with the literature. A promising outcome based on experiments shows that, tomato waste could be used as an alternative and low-cost biosorbent for removal copper(II) ion from aqueous solutions, when suitable conditions are performed.