Investigation of applicability of clay minerals in wastewater treatment

Clay minerals are natural, colloidal materials which have ion exchange capacity and adsorption properties. In environmental engineering clay minerals are used generally as adsorbance and ion exchanger in order to treat both water and wastewater, and as an impermeable layer in order to prevent groundwater contamination in landfill areas. The aim of this study was to utilize the clay minerals in wastewater treatment. Hence, kaolinite is used as an adsorbent to remove certain metals (i.e. Cu, Fe, Ni, Zn) from aqueous solutions. Synthetic and industrial wastewaters were used in batch adsorption experiments. In the experiments, the effects of the pH, particle size, adsorbent dosage, contact time, and initial concentrations on metal removal were investigated. Experimental results were showed that kaolinite is a very strong adsorbent. Metal uptake was strongly affected from the pH of the metal solution. The maximum Cu, Ni and Zn adsorption were observed at pH 10. Copper concentration was reduced from 1000 ?g/L to 5 ?g/L yielding 99.4% removal efficiency. The maximum efficiency for Ni and Zn ions were 98% and 97% respectively. However, highest iron ion adsorption was obtained at pH 5 yielding 99% efficiency. Although, adsorption efficiency was not significantly affected from the particle size, the smallest particle size, i.e. 0.053 mm was determined as an effective diameter for the kaolinite. Required adsorbent doses were 0.1 g/L for copper and zinc ions. Relatively higher doses were required for nickel and iron adsorption. In addition, metal uptakes were accomplished very quickly. 15 minutes contact time was enough for the effective metal removal. Besides, adsorption kintecis were evaluated. Adsorption data for copper, iron and nickel was fitted to Freudlich equation which exhibits that physical adsorption mechanism is effective in the process. Keywords: Adsorption, clay minerals, heavy metals, kaolinite, wastewater treatment.