Biosorption characteristics of cadmium and lead onto eco-friendly dried cactus (Opuntia ficus indica) cladodes

The biosorption of cadmium (II) and lead (II) ions onto a natural, plentiful and low-cost biosorbent developed from cactus cladodes was investigated in batch mode. Experiments were carried out as a function of average biosorbent particle size, pH, biosorbent mass, contact time, initial metal concentration and temperature. The experimental results indicate that, the percentage of biosorption increases with an increase in the biosorbent dosage and the decrease of particle size. The equilibrium uptake was increased with an increase in the initial metal concentration in solution. The maximum biosorption occurred at pH of 5.8 and 3.5, respectively for cadmium (II) and lead (II) ions. Biosorption kinetic data were properly fitted with the pseudo-second-order kinetic model. The equilibrium data fitted very well to the Langmuir model with a maximum monolayer biosorption capacity of 30.42 and 98.62 mg/g, respectively for cadmium (II) and lead (II) ions. The biosorption yield decreases with an increase in solution temperature. The FTIR analysis of unloaded and metal loaded biosorbent indicated the involvement of CO, OC and COC groups in metal binding.