Synergetic effects and flocculation behavior of anionic polyacrylamide and extracellular polymeric substrates extracted from Klebsiella sp. J1 on improving soluble cadmium removal

The performance and flocs properties in removing soluble cadmium of the dual flocculant APAM–MFX (anionic polyacrylamide APAM used in combination with extracellular polymeric substrates extracted from Klebsiella sp. J1 MFX) were studied compared with the performance of using bioflocculant alone. In addition, adsorption isotherms and kinetic process for Cd(II) adsorption onto APAM–MFX were investigated. APAM–MFX synergistically improved the Cd(II) removal percentage by 82.68%. Characteristic flocs formed by APAM–MFX indicated the synergetic effects resulted from additional bridging bonds between APAM and MFX. Adsorption process was best described by the Freundlich isotherm and pseudo-second order kinetic model. The mean free energy E (8.39–8.57 kJ mol−1) and activation energy Ea (45.09 kJ mol−1) were determined. Based on the results, the main mechanism of Cd(II) removal by APAM–MFX could be chemical ion exchange, and the liquid-film diffusion step was the rate-limiting step.