Controlled removal of textile azo dye Congo red from aqueous system using PEG-ZnO/rGO composite

Water pollution is a pressing global concern due to the uncontrolled discharge of organic pollutants into aquatic environments without adequate treatment. One significant contributor is the release of organic dyes, notably Congo red (CR) dye, from industrial effluents, posing environmental and health risks. In response, a highly effective 2D porous material, the PEG-ZnO/rGO composite, has been developed for the removal of CR dye from water systems. The composite was thoroughly characterized using XRD, FTIR, SEM, AFM and EDX analytical techniques to assess its crystalline nature, functionalities, surface morphology, 3D structure and elemental composition. Under optimized conditions (pH 3, 3 mg adsorbent dose and 0.5 mM CR dye concentration), the PEG-ZnO/rGO composite demonstrated a remarkable 94% removal efficiency of CR dye from aqueous solutions, with an adsorption capacity of 97.462 mg/g. Various isotherm models, including Langmuir, Freundlich, D-R, and Temkin, were applied to determine the adsorption capacity, with the Langmuir model showing the best fit ( R 2 = 0.9809), indicating a homogeneous surface for CR dye adsorption. The practical utility of the composite was validated through testing in both river and synthetic water samples, yielding recovery values within acceptable limits, affirming its potential for commercial-scale application in CR dye removal.