Advances made in removing paraquat herbicide by adsorption technology: A review

The present review analyzed papers using adsorption that explore the removal of paraquat herbicide from aqueous effluents. Contamination and toxicology aspects of the paraquat are tackled as well. Analysis regarding the effects of process variables and textural proprieties on the paraquat adsorption is presented. The reported works found that the best adsorbent was those of silicate and carbon nature, which presented adsorption capacities above 400 mg g(-1). Unfortunately, most works do not report the paraquat solution's pH or perform adsorption conditions optimization. Regarding the adsorption kinetics, it was found that the pseudo-second -order is the proper model to represent several paraquat systems; however, mass transfer investigations are not presented. Classical isotherm models are the most employed, such as Langmuir and Freundlich. In addition, the paraquat adsorption systems are of any thermic nature (endothermic/exothermic), with the paraquat molecules binding due to physisorption. Last, common mistakes in the reports, knowledge gaps, and future perspectives are discussed, focusing on improving the adsorption works.

Automated summary

This review analyzed papers that use adsorption to remove paraquat herbicide from aqueous effluents, and also discussed the contamination and toxicology aspects of paraquat. It was found that silicate and carbon materials are the best adsorbents, and the most commonly used isotherm models are Langmuir and Freundlich. However, most studies did not report the pH of the solution or optimize the adsorption conditions.