Efficient removal of chemical oxygen demand from lye wastewater by APTES-TIO2/GO mixed matrix membrane: Optimization using Box-Behnken Design

Wastewater produced from chemical industries contains high levels of inorganic and organic pollutants. The beneficial reuse of this wastewater requires the application of membrane technology to remove these organic compounds. This work aims to optimize the synthesis of polyvinylidene fluoride (PVDF) composite membranes for the removal of chemical oxygen demand (COD) from lye wastewater. 3-aminopropyl triethoxysilane modified titanium dioxide/graphene oxide (APTES-TiO/GO) was introduced into the PVDF solution to prepare the nanocomposite membranes via immersion precipitation. Box-Behnken Design was used to reduce the number of preparation parameters and optimize the permeate flux and COD reduction. The effects (including interacting and quadratic effects) of PVDF (wt.%), APTES molarity (mM), and APTES-TiO/GO (wt.%) on permeate flux and COD reduction were investigated. Overall, the APTES molarity and the APTES-TiO/GO loading had a significant effect on the permeate flux, while PVDF and APTES-TiO/GO loading presents significant effects on the COD reduction. Under optimized conditions of PVDF (17.22 wt%), APTES (900 mM) and APTES-TiO/GO (0.1 wt%), the permeate flux of 65.545 kg m h and COD reduction of 99.54% was achieved. Meanwhile, the experimental values for permeate flux and COD reduction were 66.79 kg m h and 99.56%, respectively. Furthermore, the optimum membrane presents a higher permeate flux and COD reduction when compared with pure membrane due to improved hydrophilicity and porosity. Additionally, the fouled membrane could be effectively regenerated by self-cleaning. This hybrid membrane offers promising application prospects for the treatment of wastewater, which is in-line with the requirements of sustainable development and thus promotes the development of cleaner production technologies.