Sulfate Adsorption from Polluted Water Using Montmorillonite Nanoclay

Sulfate is an important anion in natural waters, and its excessive concentration can be harmful. Therefore, in this study, the efficiency of sulfate removal using nanoclay montmorillonite (adsorbent) from water was investigated by determining the effect of adsorbent concentration, pH, time, and temperature to determine the optimal conditions. The sulfate adsorption isotherms were also examined. The highest sulfate removal was achieved at a concentration of 1 g/l of nanoclay montmorillonite, resulting in 4.47 mg/g or 23% removal, at pH 3 with 2.87 mg/g or 27% removal, at a time of 90 minutes with 2.15 mg/g or 21% removal, and at a temperature of 25°C with 3.54 mg/g or 35% removal. Thermodynamic constants indicated that sulfate adsorption on the adsorbent surfaces is endothermic and spontaneous. The pseudo-second-order kinetic model provided a better fit to the time data, indicating chemical adsorption of sulfate. Among the isotherm equations, the Langmuir equation showed a better fit compared to Freundlich, indicating monolayer adsorption surfaces. Furthermore, the maximum adsorption capacity of nanoclay montmorillonite for sulfate (SO4˭-S) was found to be 9.7 mg/g. SEM-EDX analysis also revealed surface adsorption of sulfur and changes in the surface. Therefore, this nanoclay was effective in removing sulfate from water.