Fast and highly efficient removal of organic dyes from aqueous solution by attapulgite modified with different amino groups

Type of functional groups of the adsorbent is crucial for an adsorption process which significantly affects adsorption rate and adsorption capacity for certain adsorbate. In this study, attapulgite (APT) was modified with different amino groups and the adsorbents obtained were used to remove toxic organic dyes from aqueous solution. Five adsorption kinetic models and three adsorption isotherm models were employed to estimate the adsorption behaviors for organic dyes methylene blue (MB) and Congo red (CR) onto the adsorbents. The results showed that adsorption behaviors of the adsorbents for MB were different from those for CR, and among the four adsorbents, APT exhibited the highest adsorption capacity for MB (307.27 mg/g) while APT modified with hyperbranched polyamide-amine (APT-(3)) had the highest adsorption capacity for CR (1277.33 mg/g) according to adsorption kinetic data, indicating the type of amino groups did have a significant impact on adsorption. It can be concluded that APT-(3) exhibited certain adsorption selectivity for CR. In addition, the adsorption of MB and CR was a fast and highly efficient process. The results indicated that the APT samples used can remove and enrich cationic and anionic dyes and can be potentially used in the wastewater treatment.