Adsorption of Congo red dye using metal oxide nano-adsorbents: Past, present, and future perspective

The latest developments in the adsorption of organic dyes by adsorbents (metal oxides, modified metal oxides) were addressed in this review study. The main goal of this paper is to sort out the dispersion information of adsorbent materials, which are often employed in organic dye adsorption. The review dedicated to the specific dyes adsorption using various adsorbent (metal oxides, modified metal oxides). The review covers the adsorption process including parameters, kinetics, and isotherms. The review gives the brief information of Congo red (CR) adsorption using metal oxide nano-adsorbents which provide readers with massive dye specific collection. For the first time, several metal-doped materials that absorb organic dyes are summarized and addressed. The review includes adsorption of organic dyes using single metal oxide, bimetallic oxide, trimetallic oxide, and modified metal oxide. This study also summarized the effects of critical factors such as pH, initial dye concentration, adsorbent dosage, contact time, and temperature on dye adsorption utilizing metal oxide nano-adsorbents. In addition, the kinetic and applied isotherm models have been discussed. Finally, a few recommendations are made for further research on adsorbent materials.