Pollutant decontamination by polyethyleneimine-engineered agricultural waste materials: a review

The direct discharge of untreated contaminants into global water systems has jeopardized our water security worldwide. This environmental concern has prompted scientists to develop various methods, systems and agents to remove these pollutants. One such method is adsorption, where adsorbents, such as agricultural waste materials. Compared to commercial carbon, raw agricultural waste material is easily obtained at low cost, but suffers from some drawbacks such as poor adsorptive capability. This can be solved by grafting polyethyleneimine to enhance adsorption. Indeed, polyethyleneimine-functionalized adsorbents have emerged as environmentally safe, cost-effective, and promising adsorbents with high adsorption capabilities in pollutant sequestration. Here we review adsorption using polyethyleneimine-modified agricultural waste materials for pollutant removal. The manuscript outlines the principles of adsorption and proposes methods for the introduction of polyethyleneimine on surface of materials. We present common characterization methods. Kinetics, isotherm and thermodynamic studies are also reviewed. This manuscript also presents the regeneration and reusability potential. Mechanisms involved in adsorption are discussed.