Immobilised apple peel bead biosorbent for the simultaneous removal of heavy metals from cocktail solution

Abstract Low cost water purification methods are needed in developing countries. Therefore, we have examined the biosorption potential of apple peel immobilised on sodium alginate beads. This was performed using a solution containing seven toxic ions, namely arsenic, cadmium, chromium, copper, mercury, lead and nickel. The effects of pH, contact time, biosorbent concentration and the presence of co-ions was investigated. Results showed that biosorption of all the ions except As and Cr was pH-dependent. At neutral pH the biosorption order for apple peel beads was Cd > Cu > Pb > Ni > Hg > Cr > As with 90, 80, 73, 72, 70, 10 and 2% biosorption, respectively. Biosorption reached equilibrium for Pb (6 h), Hg (10 h), Cd and Ni (24 h), and Cu (48 h). Kinetic models for film diffusion, pore diffusion, pseudo-first order (PFO), pseudo-second order and Elovich equation were applied and PFO was found to be the best fitting model based on coefficient of determination values. The biosorption of ions by apple peel beads was significantly higher than with empty beads throughout the time course (15 min—72 h). Biosorption increased with increasing biosorbent concentration for all ions except As, Cr and Hg. A significant suppression in biosorption for all ions was observed in the presence of co-ions, except for Cd and Cu. In conclusion, apple peel beads have the ability to remove toxic ions from a cocktail solution that has properties that mimic drinking water.