Review of in-depth knowledge on the application of oxides nanoparticles and nanocomposites of Al, Si and Ca as photocatalyst and antimicrobial agents in the treatment of contaminants in water

Several documents are available in the literature concerning the various water treatment technologies, including adsorption, filtration, photocatalysis, oxidation, ion exchange and others. However, most of these options have some common challenges, especially in the management of wastes generated at the end of the treatments. Photocatalysis has a unique capacity to degrade organic contaminants and convert them to harmless forms. It is on this note that the present review seeks to assess the potential of aluminium, calcium and silicon nanoparticles and their composites as photocatalysts for the degradation of several classes of organic contaminants. The review takes an overview of the variables that enhance effective photocatalysed degradation (especially band gap) and assesses the capability of the listed nanomaterials in this regard. Published literature studies on the applications of nanoparticles and nanocomposites of Al2O3, SiO2 and CaO in the degradation of several classes of organic contaminants have been reviewed. The analysis reveals that most investigations on the use of these materials as photocatalysts are dominated by dyes with little records on other contaminants such as pharmaceutical residues, toxic chemicals, etc. Cases of 100% degradation efficiency were observed for some contaminants, but the average behaviour of the selected nanomaterials is significantly high. The review also covers methods of synthesis and characterization of the investigated nanomaterials as well as the general mechanism of photocatalysis. Antimicrobial properties of the photocatalysts have been reviewed, and the expected roles of computational chemistry in the investigation of the mechanism of photocatalysis, mode of adsorption (and hence degradation) and quantitative structure-activity prediction of unknown results have also been highlighted. The review is concluded by the assessment of performance indices of the investigated photocatalysts with detailed considerations of the challenges and the way forward. Recommendations have been highlighted concerning future research needs. [GRAPHICS] .