Sorption Of Cu(Ⅱ),Cd(Ⅱ),Pb(Ⅱ) And Zn(Ⅱ) By Cotton Thread Covering Biofilm

Depositing on the surface of the solid in the natural water system, the biofilm is composed of single or mix colony of the bacteria, Cu-oxid, Mn-oxid, and a few of the minerals.Heavy metal adsorption is greatly affected by the method of developing the biofilm. In the experiment, a biofilm was developed in Dongpu reservoir on the surface of cotton threads. The characteristics and thermodynamic of Cu²⁺, Cd²⁺, Pb²⁺and Zn²⁺ adsorption on the biofilm were studied. Some factors influencing the adorption process of the biofilm also were studied, including pH, temperature, the mixed ion system. The main findings are as follows:Statistical analysis of the adsorption data showed that the thermodynamic data for each metal fit the Freundlich(F) and Langmuir(L) isotherms. The order of the maximum adsorption capacity from the greater gradually decreasing is Pb²⁺, Cu²⁺, Cd²⁺and Zn²⁺.The adsorption of Cu , Cd , Pb and Zn reached equilibrium in less than one hour and fit a second-order kinetic equation.By changing the pH, temperature and mixed ions of the solution, the main findings were as following:1. The adsorption of Cu²⁺, Cd²⁺, Pb²⁺ and Zn²⁺ increased with pH up to pH7. The optimum pH scope for Cu²⁺ is during 5 and 6. The optimum pH scope for Cd²⁺ is from 4 to 6. When the pH of the solution is between 5 and 6.5, the adsorption capacity for Pb²⁺ could reach the maximum.2. With temperature increasing from10℃to 30℃, the adsorption capacity of Cu²⁺, Cd²⁺, Pb²⁺ and Zn²⁺ increased. When temperature exceeded 30°C, the removing rate of Cu²⁺, Cd²⁺, Pb²⁺ and Zn²⁺ would decrease at different degree.3. The experiment exposed that the adsorption capacity of Cu²⁺ in the dual mix system including Cu²⁺ and Cd²⁺ was much better than that of Cd²⁺. In the dual mix system including Cu²⁺ and Pb²⁺, the adsorption capacity of Pb²⁺ was much better than that of Cu²⁺. In the dual Cu²⁺-Zn²⁺ mix system, the adsorption capacity of Cu²⁺ much better than that of Zn²⁺. In the dual Cd²⁺-Pb²⁺ mixed system, the adsorption capacity of Pb²⁺is much better than that of Cd²⁺. In the dual Cd²⁺-Zn²⁺ mix system, the adsorption capacity of Cd²⁺ much better than that of Zn²⁺. When Pb²⁺ and Zn²⁺ were mixed in a unitary system, the adsorption capacity of Pb²⁺ was much better than that of Zn .According to all experiment dates and analysis of theory, the cotton thread covering biofilm is indispensable to dispose wastewater and remedy environment. The biofilm has extensive prospect on the treatment of contaminate environment.