Study on the equilibrium, kinetics and isotherm of biosorption of lead ions onto pretreated chemically modified orange peel

In this paper, preparation of a new biosorbent using chemically modified orange peel and its biosorption of lead ion was studied. Effects of alkaline saponification, different concentrations of citric acid and different temperatures on the preparation of biosorbents were investigated. The influences of pH, shaking time, s/l ratio on the biosorption of lead ion by using different biosorbents were also studied. As can be seen from the experimental results that biosorption equilibriums were rapidly established in about one h and the reaction could be explained as pseudo-first-order kinetic processes. The lead adsorption was strictly pH dependent, and maximum uptakes of lead on different biosorbents were observed at pH range of 4.5–6.0. The order of maximum uptake capacity of lead ion on different biosorbents was 0.6SCA8 > 0.6SCA5 > 0.6SCA2 > 0.1SCA8 > 0.1SCA5 > 0.1SCA2 > SOP > 0.1CA > AOP > 0.6CA > OP. The maximum adsorption capacity of lead was obtained as 1.22 mol kg−1.