Adsorption of Zn (II) ions from refinery wastewater by sulfuric acid-modified bentonite: Kinetic and isotherm studies

A local bentonite clay from Maghnia (Algeria) was activated with chemical method characterized and tested for its ability to adsorb Zinc (II) from refinery wastewater. Batch experiments were conducted to study the effects of the main parameters such as contact time, initial metal concentration and agitation speed on the adsorption of Zn (II) by local bentonite clay. Experiences have led to the following results: an adsorption rate of the order of 98 % with operating conditions of pH = 4.5, agitation speed of 400 rpm and temperature of 25 ºC. Pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to analyze the kinetic data obtained at different concentrations. The pseudo-second-order kinetic model agrees very well with the experimental results. In order to determine the best-fit isotherm, in the studied concentration range of Zn(II) at 25 ºC, the experimental equilibrium data were analyzed using tow adsorption isotherm models: Langmuir and Freundlich models, these two models give a good fit.