Recent advances in nano-adsorbents for the sequestration of copper from water

Abstract

Adsorption using different adsorbents is seen as the most effective method of treating wastewater contaminated by heavy metal ions such as copper ions. In particular, nano-adsorbents have emerged as the state-of-the-art materials for heavy metal removal because of their unique physicochemical properties. The aim of this study was to review the progress made in the last decade (2011−2021) on the removal of copper ions from aqueous environment. Relevant works were sourced and carefully analysed. The findings revealed that various classes of nano-adsorbents have been employed in the copper ion removal, among which magnetic nanoparticles (MNPs) (43.4%) was the most frequently used class, while aerogels (1.2%) are the least frequently used class of nano-adsorbents. Best results were obtained by the modification/functionalization of the nano-adsorbents with other materials, which resulted in an increase in their specific surface area. The majority of the nano-adsorbents showed high removal efficiencies (>90%), while the highest adsorption capacity (1937.5 mg/g) was obtained experimentally with the aerogel class. The adsorption isotherm fitted well with the Langmuir and Freundlich models, while the kinetic data provided the best correlation with the pseudo-second order kinetic model for most of the nano-adsorbents. The MNPs, in particular, showed high reusability, with most of them maintaining high efficiencies even after 3–5 rounds of regeneration. Effective treatment of copper-contaminated wastewater can therefore, be achieved with the use of nano-adsorbents as a novel, non-toxic, and cost-effective technique of adsorption.