Membrane technology has become increasingly popular and important for separation processes in industries, as well as for desalination and wastewater treatment. Over the last decade, the merger of nanotechnology and membrane technology in the development of nanocomposite membranes has emerged as a rapidly expanding research area. The key motivation driving the development of nanocomposite membranes is the pursuit of high-performance liquid separation membranes that can address the bottlenecks of conventionally used polymeric membranes. Nanostructured materials in the form of zero to three-dimensions exhibit unique dimension-dependent morphology and topology that have triggered considerable attention in various fields. While the surface hydrophilicity, antibacterial, and photocatalytic properties of TiO2 are particularly attractive for liquid separation membranes, the geometry-dependent properties of the nanocomposite membrane can be further fine-tuned by selecting the nanostructures with the right dimension. This review aims to provide an overview and comments on the state-of-the-art modifications of liquid separation membrane using TiO2 as a classical example of multidimensional nanomaterials. The performances of TiO2-incorporated nanocomposite membranes are discussed with attention placed on the special features rendered by their structures and dimensions. The innovations and breakthroughs made in the synthesis and modifications of structure-controlled TiO2 and its composites have enabled fascinating and advantageous properties for the development of high-performance nanocomposite membranes for liquid separation.

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Modification of Liquid Separation Membranes Using Multidimensional Nanomaterials: Revealing the Roles of Dimension Based on Classical Titanium Dioxide

Phenol red dye removal from wastewater using TiO2-FSM-16 and Ni-FSM-16 photocatalysts

UV–Vis activated CuO/CuS/WO3@PANI heterostructure for photocatalytic removal of pharmaceutical active compounds

Discharge of dye-containing textile wastewater can have significant adverse effects on environmental health. Advanced oxidation processes (AOPs) are effective in removing dyes from wastewater as they can mineralize the dyes into harmless substances. However, AOPs have some disadvantages, including sludge formation, metal toxicity, and high cost. Calcium Peroxide (CaO2) is an eco-friendly and strong oxidant that can be used as an alternative to AOPs for the removal of dyes from textile wastewater. The direct use of CaO2 for the oxidation of dyes does not result in any sludge formation, unlike some AOPs that generate sludge as a byproduct. In this study, the use of CaO2 in the oxidation of Reactive Black 5 (RB5) was investigated without any activator. The effects of various independent parameters on the oxidation process were investigated. These were pH, CaO2 dosage, temperature, and some anions. The weights of the independent parameters on the dye oxidation were evaluated with the Multiple Linear Regression Method (MLR). It was determined that the most effective parameter on RB5 oxidation was CaO2 dosage. The optimum pH for the oxidation of RB5 by CaO2 was determined as 10. It was found that 0.5 g CaO2 was sufficient for the oxidation of 100 mg/L RB5 with approximately 99% efficiency. The study also reveals that the oxidation process is endothermic in nature, and the activation energy (Ea) and the standard enthalpy (ΔH°) for the oxidation of RB5 by CaO2 are determined as 31.135 kJ mol-1 and 110.4 kJ mol-1, respectively. The presence of anions was found to decrease RB5 oxidation, with the order of decreasing effectiveness being PO43->SO42->HCO3->Cl->CO32->NO3-. Overall, the study demonstrates that CaO2 is an effective, easily applicable, eco-friendly, and cost-effective method for RB5 removal from textile wastewater.

Eco-friendly Oxidation of a Reactive Textile Dye by CaO2: Effects of specific independent parameters.

Nowadays, fast-growing industrialization has resulted in the release of enormous amounts of contaminants such as toxic dyes into water bodies and leading to cause health and environmental risks. In this regard, we prepared inorganic nanocomposites for the treatment of toxic dyes. Hence, we synthesized TiO2/PAni/GO nanocomposites and examined them by using XRD, SEM, TEM, UV–Vis spectroscopy, BET analysis, and a photoluminescence investigation. In addition, band gap energies of the nanocomposites were determined, and Total Organic Carbon (TOC) testing was used to determine dye degradation levels. The photocatalytic degradations of Thymol Blue and Rose Bengal dyes were investigated at different dye concentrations, illumination periods, solution pH values, and photocatalyst dosages. By using TiO2/PAni/GO, TiO2/PAni, and TiO2 at neutral pH, a photocatalyst dose of 1600 mg/L, and exposure to visible light, Thymol Blue and Rose Bengal were photodegraded 85–99%, 60–97%, and 10–20%, respectively, at a concentration of 25 ppm (180 min). Reductions in the TOCs confirmed their photodegradation, and a kinetic study revealed photodegradation followed first-order kinetics. This study shows the coating of polyaniline (PAni) and graphene oxide (GO) on TiO2 improved its ability to photodegrade Thymol Blue and Rose Bengal dye. 

Alexandra Panzert

Papers

Synthesis of TiO2, TiO2/PAni, TiO2/PAni/GO nanocomposites and photodegradation of anionic dyes Rose Bengal and thymol blue in visible light