Optimization of cu and pb biosorption by aphanizomenon ovalisporum using taguchi approach: Kinetics and equilibrium modeling

Abstract

In this study, the cyanobacterium Aphanizomenon ovalisporum collected from the Litany River in Lebanon was used as an efficient biosorbent for the removal of copper and lead metal ions from aqueous solutions. Scanning electron microscopy (SEM) revealed the change of the surface morphology due to sorption of lead and copper metal ions on algal surface sites. In addition, the elemental composition of native algal biomass showed mainly the presence of carbon, nitrogen and oxygen as 66.15%, 14.58% and 16.79% respectively. The percentage composition of C decreases while the percentages of N and O increase after biosorption of Cu and Pb, which indicates the interaction of metal ions with nitrogen and oxy functional groups on algal cell surface. Fourier transform infrared spectroscopy (FTIR) has proved the presence of the amine, phosphate, carboxyl and carbonyl groups as binding surface sites for metal ions. The optimum conditions were determined using Taguchi statistical approach. The maximum removal efficiency values (87.59% Pb; 69.65% Cu) were obtained at pH 7.5 in 75 min with 0.7 g L–1 of algal biomass and initial metal concentration of 200 mg L–1 for Pb and 100 mg L–1 for Cu. The most influential factor on biosorption is pH with a percentage contribution of 40.8% and 31.5% for Cu and Pb, respectively. The kinetic biosorption followed the pseudo-second-order model for Cu and the pseudo-first-order model for Pb. Biosorption equilibrium was well described by Langmuir adsorption isotherm for both metals