Preparation, characterization and utilization of polyacrylic acid–kaolin composite in the removal of heavy metals from water

A series of composites were prepared from polyacrylic acid and kaolinite clay mineral at various weight ratios (10–50%) and characterized for their mechanical properties. The composite at the 1:1 ratio showed acceptable mechanical properties like Shore A hardness (87.575), tensile strength 2.94 N mm⁻² and workability. The powdered material was evaluated as a sorbent for nickel ions in aqueous solution under batch-wise conditions. Experimental design was employed to carry out the adsorption experiments and to study the effects of three operating parameters: sorbent quantity (2.5–12.5 g L⁻¹), time (20–180 min.) and pH of the solution (3.5–8.5), on the sorption efficiency. In addition, the sorption capacity was also studied. The optimum conditions for the best sorption efficiency were: pH, 7.0; sorbent amount 10.0 g L⁻¹; and 100 min contact time. At the optimum conditions, the best sorption capacity was 14,503 μg Ni g⁻¹.