Application of nanozeolite technology in the removal of sulfate from the Gamasyab River

Human activities, the presence of salts in riverbeds and runoff, as well as pollutants carried by the air lead to the contamination of rivers as one of the main sources of water supply. In this study, the Gamasayab River was selected and sampling was conducted at 16 designated points for three-time intervals in the most polluted location with the highest pollutant levels compared to other stations after spectrophotometric testing of the samples, in different seasons of the year. The collected samples were transported to the laboratory for measurement and determination of the target pollutant levels. Then, they were simulated using natural and modified zeolite nanoparticles for the purpose of purification. In the following, using the Design Expert model and assuming two factors, pH and absorbent-to-pollutant ratio, the optimal absorption points were determined, and the theoretical absorption values were also obtained. The research results showed that the absorption efficiency for the modified sample with 0.2 M nitric acid and sulfuric acid was estimated at 77%. From the investigation of the interaction between sulfate and three other pollutants including phosphate, nitrate, and iron, which was investigated by simulating the solution and in order to neutralize the effect of other dissolved substances, it was found that phosphate and nitrate ions led to a decrease in sulfate ion absorption by the absorbent, while iron ions increased the absorption of sulfate by the absorbent. The simulation results of the proposed model also indicated that the optimal absorption point for the absorbent was at a pH of 9.6 and a D/C value of 17.01, resulting in an absorption of the pollutant by 5.86%. Finally, the Freundlich isotherm was chosen for this absorbent with a coefficient of determination of 0.92 as the superior isotherm compared to the Langmuir isotherm with a coefficient of determination of 0.79.