Boron nitride nanosheets incorporated polyvinylidene fluoride mixed matrix membranes for removal of methylene blue from aqueous stream

Abstract

This study aims to synthesize boron nitride nanosheets (BNNS) incorporated polyvinylidene fluoride (PVDF)-based membranes using phase inversion method for removal of methylene blue (MB) from water. We start with density functional theory (DFT) calculations to get a first order estimate of absorption capacity of PVDF and BNNS-PVDF for MB, which reveal the probability of attaining higher adsorption capacity of MB for BNNS-PVDF than PVDF. Experimentally, the loading of the BNNS has been optimized by varying it from 0.5 to 2.0 wt%. The morphological characterization shows higher roughness with increased loading and highest void density for PVDF + 1 wt% BNNS. The corresponding SBET obtained is 28 m2/g. Further, the highest pure water flux (1160 l m-2 h-1), porosity (87.68%) and mechanical strength (1.8 MPa) also confirm that the membrane loaded with 1.0 wt% BNNS is optimum. The maximum adsorption capacity of the optimized BNNS-PVDF membrane has been found to be (142.86 mg g-1) that is 2.2 times higher than the PVDF membrane (65.36 mg g-1) and is largely in line with our DFT simulations. Moreover, the thermodynamic studies reveal that the adsorption is favorable at high temperatures and the reaction is endothermic in nature. The membrane exhibits good separation and regeneration behavior. Additionally, the optimized membrane shows excellent continuous flow adsorption of simulated MB contaminated aqueous stream and 100% removal of 10 ppm MB solution is achieved. These results reveal that the synthesized membrane loaded with 1.0 wt%. BNNS is a potential candidate for MB remediation from the aqueous stream.