Removal of MCPA (4-chloro-2-methylphenoxy-acetic acid) from aqueous solutions using adsorbent produced from elutrilithe

Elutrilithe is a mixed alumina-silicate/carbon material and a solid waste of coal mines. In this study we tried to produce a new adsorbent from elutrilithe. The elutrilithe was treated with zinc chloride in an N-2 medium. The adsorption capacity of the new adsorbent was measured with MCPA (4-chloro-2-methylphenoxy-acetic acid), which is a pesticide. The adsorption experiments were carried out as a function of time, initial concentration, agitation rates, and temperature. The Langmuir model was used to fit the equilibrium data. Satisfactorily fitting the data and consistency in parameter values indicated this isotherm could be used for the system. The adsorption kinetic results were interpreted by second-order rate equation, and rate constants were calculated for different agitation rates. The intraparticle rate diffusion constants were calculated for different agitation rates. Thermodynamic parameters were calculated. The negative values of enthalpy change indicated the exothermic nature of the adsorption process, and the negative values of DeltaG(0) were indicative of the spontaneity of the adsorption process.