Metal oxides incorporated bauxite hollow fibre photocatalytic membrane for bisphenol a removal from aqueous solution

Abstract

The demand for advanced water treatment technologies is increasing for the treatment of high-strength wastewater, including complex water pollutants. Removal of bisphenol A (BPA) from water has presented a major challenge for the water industry. Membrane separation has the advantages of simplicity, high speed, and high efficiency, and has received extensive attention around the world. It is well known that membrane materials and membrane processes are two of the key factors affecting the separation process. The selection of suitable membrane materials is of great significance to produce effective dual-function ceramic membrane which possesses filtration and photocatalysis features in a single unit of membrane. In this study, naturally existing bauxite was selected as a ceramic material because of its availability and the presence of iron (III) oxide (Fe2O3) and titanium dioxide (TiO2) which have potential to be used as photocatalyst. In the first stage of this work, bauxite powder was subjected to thermal treatment at different temperatures. In the second stage of the study, a hydrophilic, asymmetric bauxite hollow fiber membrane (BHFM) was fabricated by phase inversion and sintering method. To study the morphologies of BHFM, the bauxite loading and sintering temperature was varied from 45 to 55 wt% and at temperature ranging from 1250 to 1450 ºC. Then, in the third stage, the yielded membrane was subjected to the surface modification to lift up the photocatalytic properties using titanium dioxide (1wt% of TiO2) and copper oxide (1wt% of CuO) particles via hydrothermal method for the removal of BPA. TiO2 and CuO particles were modified on the surface of 50 wt% BHFM by varying the hydrothermal time of 2.5h, 5.0h and 7.5h. In the fourth stage of the study, the photocatalytic membrane was further evaluated for the photocatalytic efficiency in degradation of BPA, which was present in water. The finding of this study showed that the powder treated at 800 ºC possessed good photocatalytic degradation as it was able to degrade up to 75% of 5 mg/L BPA. 50 wt% BHFM which spun at bore fluid flow rate of 10 mL/min, air gap of 5 cm, and sintering temperature of 1300 °C induced good mechanical strength of 98.2 MPa, stable permeate water flux (PWF) of ~281.4 L/m2h and moderate BPA degradation rate of less than 70%. The pristine BHFM and modified TiO2 and CuO BHFM with hydrothermal time of 5.0h showed promising finding with almost even distribution of modified particles on the membrane surface. The experimental results of photocatalytic activity test showed that the BPA degradation of 96.8% was achieved by CuO BHFM under visible light irradiation, while for UV light irradiation, TiO2 BHFM possessed the degradation rate of 90.3% for 360 minutes. Three intermediate products were determined which were 4-(2-hydroxy-2-propanol)phenol, 4-isopropenylphenol and dihydroxybenzene. All the findings in this study are helpful for understanding the process of photodegradation and to become a promising potential treatment to degrade BPA to provide water safety for living organisms.