The wastewater problem is a worldwide problem that is experienced by every single country. In total, 80% of wastewater enters our environment without being treated, filtered or reused. Wastewater, which contains organic pollutants, inorganic pollutants, textile dyes, pharmaceuticals, faeces, heavy metals and microorganisms, spoils our drinking water and affects our health. Efficient wastewater treatment is a critical requirement for the removal of contaminants in order to maintain a better and safe environment. In this chapter, the use of photocatalysis in previous studies, using various photocatalyst nanocomposites and UV-light and visible light for the removal of numerous pollutants, is reviewed. It is hoped that the use of photocatalytic nanocomposites for environmental remediation will provide the potential to minimize these environmental issue in the future.

Bisphenol A (BPA) is amongst the endocrine disrupting compounds (EDCs) that cause illness to humans and in this work was removed using copper (I) oxide (Cu2O) visible light photocatalyst which has a narrow bandgap of 2.2 eV. This was done by embedding Cu2O into polyvinylidene fluoride (PVDF) membranes to generate a Cu2O/PVDF dual layer hollow fiber (DLHF) membrane using a co-extrusion technique. The initial ratio of 0.25 Cu2O/PVDF was used to study variation of the outer dope extrusion flowrate for 3 mL/min, 6 mL/min and 9 mL/min. Subsequently, the best flowrate was used to vary Cu2O/PVDF for 0.25, 0.50 and 0.75 with fixed outer dope extrusion flowrate. Under visible light irradiation, 10 mg/L of BPA was used to assess the membranes performance. The results show that the outer and inner layers of the membrane have finger-like structures, whereas the intermediate section of the membrane has a sponge-like structure. With high porosity up to 63.13%, the membrane is hydrophilic and exhibited high flux up to 13,891 L/m2h. The optimum photocatalytic membrane configuration is 0.50 Cu2O/PVDF DLHF membrane with 6 mL/min outer dope flowrate, which was able to remove 75% of 10 ppm BPA under visible light irradiation without copper leaching into the water sample.

Bisphenol A (BPA) is an endocrine-disrupting chemical (EDC) that can cause adverse effects on human health. The incorporation of materials as visible light photocatalysts and its energy storage capability allow for the photodegradation of BPA, especially in the absence of a light source. To date, there have been no significant studies regarding energy storage in membrane technology, with only a focus on the suspension form. Hence, this study was conducted to degrade the pollutant through a co-extrusion process using a mixture of copper (II) oxide and tungsten oxide as the photocatalyst and energy storage materials, respectively. Both materials were embedded into polyvinylidene (PVDF) membranes to produce a Cu2O/WO3/PVDF dual-layer hollow fiber (DLHF) membrane. The outer dope extrusion flow rate was set at 3 mL/min, 6 mL/min, and 9 mL/min with photocatalyst:polymer ratios of 0.3, 0.50, and 0.7 Cu2O/WO3/PVDF, respectively. The performance of the membranes for each ratio was evaluated using 2 ppm of BPA with visible light irradiation. The results showed that each membrane’s outer and inner layers featured finger-like void structures, while the intermediate part had a sponge-like structure. The membrane with the photocatalyst:polymer ratio of 0.5 was hydrophilic and had a high porosity of 54.97%, resulting in a high flow of 510 L/m2h. Under visible light irradiation, a 0.5 Cu2O/PVDF DLHF membrane with a 6-mL/min outer dope flow rate was able to remove 97.82% of 2-ppm BPA without copper leaching into the water sample. Under dark conditions, the DLHF sample showed the capability of energy storage performance and could drive certain degradation after lighting off up to 70.73% of 2-ppm BPA. The photocatalytic DLHF membrane with the ratio of 0.5 was the most optimal due to its potential morphology and ability to degrade a large amount of BPA. It is important to emphasize that usage of materials with the capability for energy storage can provide a significant contribution toward more practical membranes, so photodegradation can occur even in dark conditions.

Visible light photocatalysis is now a subject of interest for researchers to explore further in the treatment of wastewater as it can save costs and be environmentally friendly. Cadmium sulphide (CdS) is one of the photocatalysts of visible light that has excellent properties and a low band gap. The toxicity and carcinogenicity of textile industry effluent containing predominantly textile dyes disturbs the environment. In this study, the removal of reactive black 5 (RB5), the most used dyes with CdS as visible light photocatalyst, was tested. Using X-ray diffraction (XRD), scanning electron microscope (SEM), ultraviolet-visible-near infrared (UV-Vis-NIR) spectrophotometers and photocatalytic tests under visible light, the physical and chemical properties of CdS were characterised. CdS has an irregular shape and this can be demonstrated through SEM. The band gap obtained was 2.12 eV and this was associated with the degradation efficiency of CdS under visible light as it can degrade RB5 after 360 minutes of exposure by up to 80 percent. This study proves that CdS is a strong photocatalyst of visible light that has a small band gap and crystalline particles.