Treatment of wastewater contaminated with cobalt using Saudi activated bentonite

In this study, removal of cobalt from wastewater using Saudi activated clay (bentonite) was investigated. The removal characteristics were investigated under various operating variables such as contact time, solution pH, clay dosage and initial metal concentration. It was found that adsorption of cobalt ions on Saudi activated bentonite was relatively fast and the equilibrium was reached after 30 min. Adsorption was also dependent on solution pH where cobalt removal percentage gradually increased with increasing solution pH up to 99% at pH 8. Moreover, about 100% cobalt removal was observed when solution pH was increased to more than 8. The results showed that increasing the initial cobalt concentration decreased cobalt removal percentage due to saturation of clay with cobalt ions. The adsorption isotherm data were well fitted with both the linearized Langmuir and Freundlich models. Furthermore, the value of the mean free energy determined with the D-R equation showed that adsorption process is chemisorptions. Cobalt adsorption into Saudi activated bentonite was well represented by the pseudo-second-order kinetic model.