Textile wastewater treatment using a new type of BiOBr-derived photocatalytic membrane: A comparison with current state-of-the-art filtration technology

Textile industry has been a large user of water and typically 0.2-0.5 m3 are needed to produce 1 kg of finished fabric product. The textile effluents of the dyeing and finishing processes usually contain 50-5,000 mg/L of chemical oxygen demand (COD), 200-300 mg/L biological oxygen demand (BOD) and 50-500 mg/L suspended solids, etc. During the dyeing process, because 10-15% of the dye is lost into wastewater, and the dye concentration could exceed 300 mg/L in the effluent from textile manufacturing. A number of pressure-drive membrane processes such as microfiltration, nanofiltration, ultrafiltration and reverse osmosis have been extensively studied to treat textile wastewater over the past decades at industrial scale. For example, reverse osmosis membranes are particularly suitable for removing ions and large species from dyebath effluents. The advantage is that the permeate can be made colorless and low in total salinity. Nanofiltration produces permeate with good quality and the water can be reused which usually meet with acceptable criteria. However, most of these methods face a major technical challenge in which they have low rejection rate, high fouling % and require high-pressure operation conditions. An emerging technique called the membrane distillation offers an advantageous combination of producing high quality water at nearly 100% rejection rate and low energy consumption. In this study, a type of BiOBr-derived photocatalytic membrane has been prepared using electrospinning synthesis to treat four common dyes with different surface charges used in textile industry. The BiOBr-derived photocatalytic membrane exhibited good flux recovery and attained good dye rejection rate under visible light exposure. Finally, a comparison of this technology with the current state-of-the-art filtration technology will be performed