In Situ Steam-Assisted Synthesis of CTAB-Modified Geopolymer-Based Hectorite for Enhanced Adsorption of Congo Red

Abstract

For deep purification of wastewater containing anionic dyes. In this study, cetyltrimethylammonium bromide (CTAB)-modified geopolymer-based hectorite was synthesized via a steam-assisted method using depolymerized illite-based geopolymer as the silicon source and CTAB as the modifier, enhancing its adsorption performance for anionic dyes. The product was characterized by methods such as X-ray diffraction, and the effects of parameters such as adsorbent dosage and pH on the adsorption process were investigated. Adsorption experiments revealed that when the CTAB addition was 20%, the adsorption performance for Congo red was optimal (99.79%, 997.92 mg·g−1), far superior to that of hectorite without CTAB (66.64%, 666.40 mg·g−1). The adsorption process followed pseudo-second-order kinetics and the Langmuir isotherm model. Further comparison of changes before and after adsorption indicated that the adsorption mechanism primarily involved the combined effects of electrostatic interaction and hydrophobic effects. Additionally, after five adsorption–desorption cycles, the material maintained over 92% removal efficiency. By using different geopolymers as silicon sources to prepare CTAB-modified geopolymer-based hectorite, the high universality of this synthesis strategy was confirmed. This study provides a universal, green, and sustainable route for preparing efficient anionic dye adsorption materials and expands the high-value utilization of clay resources.