Evaluation of methylene blue-removal by adsorbents recovered from industrial activity

The study evaluated the application capacity of materials recovered from mining activities (nano hematite recovered from acid mine drainage and basaltic remineralizer (BR) (rock powder) discarded from quarries) as adsorbents in removing methylene blue dye. The adsorbent materials were characterized and had their zero-charge point determined, with pHPCZ 6.5 for rock powder and 5.5 for hematite. The results showed that the basaltic remineralizer contains 51.1% silicon dioxide, 15.2% hematite, and 13.2% alumina. The analysis also indicated that the levels of heavy metals in the rock powder were within the limits established by CONAMA resolution 420/2008, suggesting safety in its application in the environment. The adsorption tests were performed in batches, using 0.5 g of adsorbent in 100 mL of 10 mg. L-1 methylene blue solution. The experiments were performed in triplicate in the pH range of 2 to 6. The dye removal capacity was satisfactory, with hematite removing an average of 1.73 mg. g-1 and basaltic rock powder 2.08 mg. g-1. The greater efficiency of basaltic rock powder, even with a smaller amount of hematite (approximately 0.08 g), can be attributed to the concomitant presence of alumina, offering more active sites for dye adsorption. This study suggests new possibilities for removing textile dyes from effluents and adds commercial value to basaltic rock powder, a byproduct of the mining industry, and nanoparticles recovered from industrial activity.