Study Of Defoliation As Biosorbent For Cu(Ⅱ) And Cd(Ⅱ) Removal From Simulated Wastewater

The defoliation was investigated as a novel biosorbent of heavy metal taking Cu(Ⅱ) and Cd(Ⅱ) from simulated wastewater as a model system. Different environmental effect factors such as initial concentration, biosorbent dose, solution temperature and solution pH were studied.Modification of defoliation was compared by adsorption capacity.The adsorption behavior of heavy metals onto raw and modificated defoliation, kinetic and Infrared Spectroscopy were all studied. In the end, competitive adsorption was considered.The result shows that:(1)The adsorption equilibrium of Cu(Ⅱ) and Cd(Ⅱ) onto defoliation were reached in 250 mins. The adsorption behavior was effected by initial concentration of heavy metals and solution temperature.Optimal solution pH of the adsorption of Cu(Ⅱ) and Cd(Ⅱ) onto defoliation were 7.00 and 6.00, respectively. Langmuir and Freundlich isotherm were proved to fit the adsorption of Cu(Ⅱ) and Cd(Ⅱ) onto defoliation well, respectively. Pseudo-second order equation provided the greatest accuracy for the kinetic data, and the adsorption was dominated by external mass transfer and inter-diffusion.(2)Equlibrium adsorption capacity of Cu(Ⅱ) and Cd(Ⅱ) onto NaOH-treated defoliation increased 32% and 15% compared by raw defolition,respectively. Kinetic data of Cu(Ⅱ) and Cd(Ⅱ) onto NaOH-treated defoliation fit Pseudo-second order well. FTIR demonstrated that carboxyl and hydroxyl groups were involved in the biosorption of the heavy metal ions. (3) In the competitive system of Cu(Ⅱ)-Cd(Ⅱ),the heavy metal sorption followed the order: Cu(Ⅱ)>Cd(Ⅱ). Pseudo-second order and Freundlich isotherm were proved to fit the competitive adsorption well.(4) Gibbs free energy and Enthalpy of sorption have also been evaluated to be negative, which confirms the sorption process was spontaneous and radiative.