Removal of pollutants from aqueous media using cow dung-based adsorbents

Abstract

An ideal adsorbent must be relatively cheap, abundant, easily undergo modification, and exhibit better removal efficiency. Animal wastes are much better adsorbents in comparison with activated carbon adsorbents with respect to being cost-effective and their zero regeneration process factor. The review aims to report the efficiency of utilized cow-dung based adsorbents for the sequestration of a wide spectrum of pollutants from aqueous media. It discusses the potential of utilizing cow dung as a cheap and effective adsorbent. It was observed that cow dung-based adsorbents were efficient for the removal of dyes, heavy metals, and other pollutants from aqueous solutions. The maximum reported uptake capacity of dyes and heavy metals was 501 ​mg/g and 625.26 ​mg/g for Methylene blue and lead, respectively, which were both for cow dung activated carbon. The Langmuir and Freundlich isotherm models emerged as the best-fit models for almost all studies. Based on the review outcome, a pseudo-second-order model was reported as the kinetic model of best fit in all cases. Other adsorption studies such as adsorption mechanism, thermodynamic modelling, desorption, column adsorption, and competitive adsorption were also included in this study. Finally, the study identified some knowledge gaps that could aid future investigation in this research field. Summarily, it can be deduced that cow dung-based adsorbent has exhibited good potential as an adsorbent for the mitigation of pollutants from water.

Keywords

• Adsorption
• Cow dung
• Dyes
• Equilibrum modelling
• Heavy metals
• Pollutants