CuO nanoparticles (CuO NPs) for water treatment: A review of recent advances

Abstract

Copper oxide nanoparticles (CuO NPs) are regularly investigated and effective adsorbent materials due to their small size, high surface area, natural abundance of starting material for synthesis, low-cost production processing and non-toxic nature. In this study, the adsorption of pollutants by CuO NPs was reviewed. The goal was to synthesise recent research findings, identify knowledge gaps and predict areas for future work. Conventional chemical processes like microwave heating technique and precipitation are the most popularly employed techniques for the synthesis of CuO NPs. The highest reported adsorption capacity for CuO NPs was 3152 mg/g for fluoride showing it can remove more than 3 times its weight fluoride from the aqueous phase. The best-fit kinetics and isotherm models for adsorption using CuO NPs is the pseudo-second order model (R2 > 0.99) and Langmuir model (R2 > 0.99) respectively for dyes and heavy metals. Thermodynamics analysis revealed that the adsorption by CuO NPs process was majorly spontaneous and endothermic. CuO NPs can be reused for as much as 5 cycles with >80 % recovery of pollutants in most cases. Areas for future work include mechanistic investigations by statistical physics, competitive adsorption and column experiments. Due to the negative ecotoxicological effect of the use of CuO NPs, special care must be taken to remove/recover it from wastewater before environmental release. It is surmised that CuO NPs is an effectively used adsorbent for the mitigation of various pollutants from the aqueous environment.