Removal of cadmium from aqueous solution by immobilized Microcystis aeruginosa: Isotherms, kinetics and thermodynamics

WANG Hui(王慧)^{1, 2}, LIU Yun-guo(刘云国)^{1, 2}, HU Xin-jiang(胡新将)^{1, 2}, LI Ting-ting(李婷婷)^{1, 2}, LIAO Ting(廖婷)^{1, 2}, LU Ming(卢明)^{1, 2}

(1. College of Environmental Science and Engineering, Hunan University, Changsha 410082, China;
2. Key Laboratory of Environmental Biology and Pollution Control of Ministry of Education
(Hunan University), Changsha 410082, China)

Abstract:The Microcystis aeruginosa (MA) was immobilized on sodium alginate and used as biosorbent for removal of Cd(II) ions from aqueous solution. The biosorption process is pH dependent, and the optimum biosorption was observed at pH 6.0 with the biosorption capacity of 98.38 mg/g. Among Langmuir, Freundlich and Temkin isotherm models, the Freundlich and the Temkin isotherm ？t well with the experimental data. Cd(II) ions biosorption follows the pseudo-second-order kinetic model. The rate controlling mechanism study reveals that film diffusion is the rate-limiting step and intraparticle diffusion is also involved in biosorption. Thermodynamic parameters, such as Gibbs free energy (ΔG°), the enthalpy (ΔH°) and entropy (ΔS°) were calculated, and revealed that the biosorption process is spontaneous, exothermic and random. Furthermore, the immobilized MA can be regenerated using 0.1 mol/L HCl solutions.

Key words:cadmium; immobilized Microcystis aeruginosa; biosorption; isotherms; kinetics; thermodynamics