مرکز منطقه ای اطلاع رساني علوم و فناوري - Adsorption of Co (II) from aqueous solution by Natural clay mineral Beidellite

Abstract :

In this study, removal of cobalt from wastewater using natural clay (beidellite) was investigated. The adsorption capacity of cobalt was studied at beidellite dosages (0.20-20 g/L), initial Co(II) concentrations (50-1000 mg/L), temperature (293-333 ^0K) and solution pH values (2-7). Maximum adsorption was observed at the pH range of 6-7.With an initial concentration of 50 and 400 mg/L of the adsorbate at pH 7.0 and contact time of 100 min, the percentage adsorptions were found to be 99.5% and 86.8%, respectively. The kinetic data obtained at different initial Co(II) concentrations (50- 1000 mg/L) indicated that adsorption rate was fast and most of the process was completed within 40 min, followed by slow attainment of equilibrium. Pseudo-second order model fitted the data well with very high correlation coefficients (r^2 0.985). Adsorption capacities was calculated from the Langmuir isotherm as 21.13 mg/g at an initial pH of 7 for the 50-1000 mg Co(II)/L solution. Thermodynamic parameters such as enthalpy (∆H^o ), free energy (∆G^o ) and entropy (∆S^o ) were calculated as - 2.01, 7.27-8.31, and 0.031 kJ/mol ^oK between 293-333 ^oK, respectively. These results show that adsorption of Co(II) on beidellite was an endothermic process and the process of adsorption was favoured at high temperatures. The present study revealed that such a natural clay material beidellite could be used as an efficient sorbent for the removal of cobalt from wastewater streams.