Optimization of biosorption of nickel(II) and cadmium(II) by indigenous seaweed Enteromorpha using response surface methodology

In the present paper, the biosorption capacity of an indigenous seaweed Enteromorpha sp. was assessed and compared for nickel(II) and cadmium(II) removal from aqueous solution. Response surface methodology based on Box–Behnken design was employed to achieve the optimum removal conditions as well as investigating the effects of some independent variables on the process performance. It was found that the maximum nickel(II) removal achieved was 87.16% under optimum conditions of pH 4.79, biomass concentration of 1,000 mg/L, contact time 70 min and temperature of 25 °C. For cadmium the optimum conditions were defined as pH 4.88, biomass concentration of 1,000 mg/L, contact time 50 min and temperature fixed at 65 °C which resulted in a maximum 75.16% removal. Equilibrium isotherm studies revealed that Freundlich and Langmuir models were more successful for describing nickel(II) and cadmium(II) biosorption data, respectively. The maximum sorption capacities of biomass, q max, for nickel(II) and cadmium(II) were predicted as 250 and 167 mg/g, respectively, by the Langmuir model. The results suggest Enteromorpha seaweed as an eco-friendly and suitable biosorbent for nickel(II) and cadmium(II) removal from aqueous solutions.