Development of new carbonaceous material from grapefruit peel for the adsorption of Cu+2 ions

In this study, new kind of adsorbent was produced from grapefruit peel by low temperature-microwave assisted hydrothermal carbonization technique. Adsorption mechanism of this new material and its Cu+2 ion adsorption capacity were investigated. The obtained material was characterized by FTIR-ATR spectroscopy and SEM analyses and new developed slits, dependently increment in surface area and changes in surface functional groups of material were observed after carbonization. Effects of different conditions on the adsorption capacity (qe, mg/g) were studied. Activation process improved the adsorption capacity of adsorbent as almost twice. Increasing pH, temperature and initial Cu+2 ion concentration caused the increment in adsorption capacity. Kinetic behavior was described by Pseudo second order, Logistic and Elovich models while Langmuir, Freundlich and Dubinin-Radushkevich models were carried out to define isothermal behavior of adsorption. According to both R2 and SSE values, Logistic and Freundlich models were found as the best models to describe the kinetic behavior and equilibrium isotherm, respectively. Maximum adsorption capacity was observed as 48.22 mg/g at 318 K and 60 mg/L Cu+2 concentration. Thermodynamic studies showed that adsorption process was spontaneous and endothermic and mainly controlled by physico-chemical mechanism. As a result, adsorbent produced by economic, fast and eco-friendly HTC technique had a good potential as adsorbent in the adsorption of Cu+2 ion and this material could be improved for other heavy metal adsorption processes.