Biosorption of Cadmium (II) and Chromium (VI) from Aqueous Solution by Chemically Modified Tithonia Diversyfolia Biomass

Abstract

The search for alternative and innovative treatment technologies for the effective removal of heavy metals from aqueous wastes has been a research of concerted effort due to the inherent limitations exhibited by the conventional methods such as less efficiency, sensitive operating conditions, energy requirements and generation of toxic sludge or other waste products. Biosorption, the passive uptake of heavy metals by biomaterials has been studied recently because of its high efficiency and cost effectiveness. Therefore, the biosorption capacity of Tithonia diversyfolia biomass chemically modified with sodium hydroxide for the removal of cadmium and chromium ions from aqueous solution was investigated. The effects of temperature, contact time, initial concentration of metal ions, adsorbent dosage and pH on the biosorption of Cd2+ and Cr6+ ions were assessed. Thermodynamic parameters such as free energy change (ΔG), enthalpy change (ΔH) and entropy change (ΔS) during the biosorption were evaluated. The results showed that the biosorption process of Cd2+ and Cr6+ by chemically modified Tithonia diversyfolia (CMTD) biomass was feasible and exothermic under the studied conditions. The equilibrium process was well described by the Langmuir isotherm model, with a maximum biosorption capacity of 46.75mg/g and 48.00mg/g for Cadmium and Chromium ions, respectively. Kinetic studies indicated that the biosorption of metal ions followed a pseudo-second order equation.