Fouling behavior of negatively charged PVDF membrane in membrane distillation for removal of antibiotics from wastewater

We have reported on the potential use of membrane distillation (MD) to remove emerging pollutants from wastewater as an alternative to other biological and chemical treatments. For every successful application of MD, the fouling and scaling associated with membrane wetting must be reduced to minimize the deterioration in performance. Here, we have hypothesized that the effectiveness of the antibiotic removal from wastewater can be significantly influenced by the interfacial interaction between the antibiotics and the membrane surface. To verify this, we investigated the applicability of the direct contact MD (DCMD) to treat the antibiotics, including positively-charged tobramycin (TOB), negatively-charged cefotaxime (CTX), and neutral ciprofloxacin (CFX). DCMD tests were performed with negatively-charged commercial polyvinylidene fluoride (PVDF) membranes, with the observance of a significant decline in flux and wetting issues during the MD treatment of TOB. The PVDF membrane exhibited a stable flux (CTX: 19.76 LMH and CFX: 19.81 LMH), with almost 100% rejection of the CTX and CFX due to electrostatic repulsion. Optical coherence tomography (OCT) further elucidates the in-situ fouling development for TOB, CTX and CFX.