Effect of mineral type, calcination and calcium carbonate addition on the nickel cation adsorption of clays

Various adsorbent materials such as clays, calcium silicates and zeolite have been studied for their ability to remove nickel from industrial wastewater. The current research aims to investigate the thermal decomposition of three types of clay (Taiwan kaolin, Zonuz kaolin and Chah-Taleb Bentonite). Samples of pure clays, calcined clays and containing CaCO3 as additive were examination. The calcination was carried out at 700 and 800 °C for kaolins and bentonite, respectively. The XRD of the calcined samples containing 10 wt.% of CaO and sintered at 900 °C indicates the presence of a amorphous phase together with anorthite and wollastonite phases. To examine the absorption of nickel, one gram of each sample of absorbent materials was put in a solution of 50 mg /l for 24 h. Then, the remaining nickel was determined by Inductively Coupled Plasma (ICP). The results showed that the samples of pure Iranian kaolin, and Taiwan kaolin with 10 wt.% CaCO3 were the best adsorbent materials. However, adding more than 10 wt.% CaO to Iranian kaolins had a negative effect on absorption. The samples of pure bentonite and containing 10 wt.% CaO showed better absorption of nickel than that of calcined bentonite.