Fabrication of eco-friendly adsorbent derived from serpentine tailings for the removal of organic dyes

Organic dye wastewater is one of the serious environmental pollutants in recent years, which threatens the health of many organisms. The present work reported an excellent and economical adsorbent (ST-600), which was obtained from serpentine tailings. After roasting treatment, the removal efficiency of ST-600 for rhodamine B (RhB) and methylene blue (MB) were increased to 92.68% and 97.71%, respectively. The significant enhancement of dyes removal efficiency was attributed to the improvement of layer spacing, polymerization degree of basic unit [SiO4] structure, and pore size of minerals via roasting treatment. The adsorption capacity of ST-600 towards MB was stronger than for RhB, which was demonstrated by density functional theory (DFT) calculation that adsorption energy of MB (-1.58 eV) was lower than that of RhB (-1.46 eV). Meanwhile, adsorption mechanism of RhB and MB on the surface of ST-600 was a complex reaction process involving electrostatic action, hydrogen bonding, ion exchange, and n-pi interaction. ST-600 had exhibited excellent adsorption performance for different dyes, meaning that it could be regarded as a promising adsorbent for dyes in practical applications.