Recent advance in enhanced adsorption of ionic dyes from aqueous solution: A review

Adsorption technology is a hot topic in the field of dye removal, and higher adsorption capacity is one of the eternal themes. Ionic dyes account for more than 90% of the literature on dyes adsorption in recent decade. In this article, various physical and chemical mechanisms of dye adsorption are combed in detail, and electrostatic interaction is the major mechanism of ionic dyes adsorption. The key to improving the adsorption capacity is to increase the electrostatic interaction force/surface charge of adsorbents. Moreover, different modification methods to improve the adsorption of ionic dyes by changing the charge properties of adsorbents were reviewed, including grafting functional groups, composite, and adsorbent structural modulation. The practical prospects of each modification method/substance were highlighted and discussed from the perspectives of performance, preparation processes, cost, and toxicity. This review mainly includes (1) the classification and adsorption mechanisms of dyes; (2) types, performance and application prospects of grafted ligands and substances applied for compositing; (3) the performance and limitations of the structural regulation methods; (4) research progresses of amphoteric adsorbents; (5) the prospect of adsorbents development and industrial-scale application. This review attempts to provide a detailed reference for the modification of adsorbents via electrostatic interaction regulation.