Formation and performance of Kaolin/MnO2 bi-layer composite dynamic membrane for oily wastewater treatment: Effect of solution conditions Original Research Article

To develop an efficient dynamic membrane for application in oily wastewater treatment, there is a need to explore an appropriate coating technique and to advance its separation performance. The formation and separation performance of the dynamic membrane from Kaolin and MnO2 were investigated with particular objectives on the choice of an appropriate membrane-coating technique and the discussion of the effect of solution conditions. The microstructures of the dynamic membrane were examined using the scanning electron microscope. The results showed that the deposition of MnO2 particles onto the surface of Kaolin dynamic layer forming a Kaolin/MnO2 bi-layer composite dynamic membrane is an effective coating technique. The optimum concentrations of the Kaolin solution and KMnO4 solution should be 0.4 g L−1 and 0.1 g L−1 respectively. With the rise of oil concentration, the steady permeate flux decreased and oil retention ratio increased. In the low oil concentration range from 0.1 g L−1 to 1.0 g L−1, the variation characteristics were more obvious. In neutral or alkaline environments, the dynamic membrane was stable with high permeate flux and oil retention ratio of over 99%. As the temperature rose from 283 K to 313 K, the steady retention ratio decreased from 99.9% to 98.2% and the steady permeate fluxes increased from 120.1 L m−2 h−1 to 153.2 L m− 2 h−1.