Zinc adsorption kinetics by phosphogypsum — A preliminary study

Materials and Methods PG, obtained from TÜGSA^ Fertilizer Plant in Samsun, Turkey, was sieved (particle size, 65 mesh) and then preconditioned with lime milk. Physical and chemical characteristics of raw and lime-preconditioned PG have been published. Aqueous solutions (100 ml) containing Zn ions (50 mg/l) were taken in Erlenmeyer flasks (250 ml) containing lime-preconditioned PG (1 g). These flasks were agitated (200 rpm) at room temperature (Clifton NE5 28D Model Shaking Water Bath). Initial pH (9.5) of adsorbate solution was adjusted using NaOH and HNO 3 before contact of adsorbent with metal ion solution. At the end of predetermined time intervals, content of flasks were separated by centrifugation and supernatant was analyzed for Zn using atomic adsorption spectrophotometer (ATI UNICAM 929 Model Flame AAS). Amount (mg/g) of Zn adsorbed on lime-preconditioned PG was calculated as