Adsorption of Cu²⁺ and mechanism by natural biofilm

The biofilm culturing device fixed on the slides was vertically placed in the commonly called small Li Lake of Jiangnan University. The adsorption experiment of Cu²⁺ was carried out by mature biofilm. Besides, scanning electron microscope (SEM), polymerase chain reaction and denaturing gradient gel electrophoresis (PCR-DGGE), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy-energy spectrum (SEM-EDX) were used to analysis the effect of Cu²⁺ on the morphological structure of biofilm. The result indicated that when the initial concentration of Cu²⁺ was 5 mg·L^-1, the absorption capacity of Cu²⁺ by unit mass biofilm is the maximum. More extracellular polymeric substances (EPS) were released by biofilm due to the stimulation of Cu²⁺. EPS was beneficial to the adsorption of Cu²⁺ by biofilm. After the adsorption of Cu²⁺, the bacterial diversity index decreased, while there were no significant differences in microbial communities on biofilm. Moreover, the main groups combining Cu²⁺ were the hydroxyl groups and amide groups in S-EPS and B-EPS. Ion exchange is a mechanism of the adsorption of Cu²⁺ by EPS.