Sorption of Alizarin Red S and Methylene Blue on Halloysite from Single and Mixed Solutions

The extensive use of synthetic materials in modern society presents a great challenge to environmental and water quality. As such, numerous studies were dedicated to the removal of emerging contaminants from water using novel materials as sorbents or catalysts. With large reserves and low material costs, Earth material has also attracted great attention for contaminant removal. Halloysite is a 1:1 layered clay mineral with moderate cation exchange capacity that can be used for the removal of cationic contaminants. On the other hand, as it may bear positive charges on the aluminum hydroxyl sheets, it could be used to remove anionic contaminants. In this study, the removal of a cationic dye, methylene blue (MB), and an anionic dye, alizarin red S (ARS), from the water was evaluated from single and mixed solutions. The results suggested that from single solutions, MB removal was via cation exchange while ARS removal could have originated from anion exchange. From mixed solutions, their removal was mutually increased, which may be due to a synergistic effect in the presence of a type of charged dyes serving as counterions to enhance the sorption of dyes of opposite charges. This finding suggests that halloysite may serve as a sorbent for the removal of organic contaminants of different charges at the same time, which is a new perspective that needs further evaluation and expansion.

Automated summary

The extensive use of synthetic materials in modern society poses a significant challenge to environmental and water quality. This has led to numerous studies focused on the use of novel materials as sorbents or catalysts for the removal of emerging contaminants from water. Halloysite, a 1:1 layered clay mineral, has shown potential for removing both cationic and anionic contaminants due to its moderate cation exchange capacity and positive charges on the aluminum hydroxyl sheets. The findings of this study suggest that halloysite can serve as a sorbent for the simultaneous removal of organic contaminants with different charges, presenting a new perspective that requires further evaluation and expansion.