Remediation of an aqueous solution contaminated with an anionic diazo dye using natural chabazite

Although anionic azo dyes are frequently used in industry, most of them are poisonous, carcinogenic, and mutagenic. This study focused on the evaluation of chabazite for use in the adsorption of Congo red (CR), an anionic diazo dye, from aqueous solutions. The material used in the study had a 322.8 m2/g BET surface area. Equilibrium was reached after 4 h and the data were in good agreement with the pseudo-second-order kinetic model. The highest sorption efficiency was achieved at pH 7.3, the natural pH of the solution, but the impact was not significant, thus, chabazite can also be used efficiently throughout the range of pH 4.5–9.4. The separation efficiency reduced with increasing temperature, and according to the thermodynamic data, the process was non-spontaneous and exothermic. Adsorption capacity had a maximum value of 26.525 mg/g and was positively affected by chabazite dose but negatively affected by CR concentration. The data were well described (R2 = 0.9947) by Freundlich isotherm model. This study exhibits that chabazite can be used for the adsorption of an anionic diazo dye, i.e. Congo red.