Characteristics of manganese-coated sand using SEM and EDAX analysis

"Manganese-coated sand" is a type of silica medium coated with manganese oxides, formed from the sorption of manganese oxides during long-term filtration via the process of rapid sand filtration, followed by aeration in a water treatment plant. Locally available manganese-coated sand, both for packing and as a byproduct of filtration processes for water treatment plants in Taiwan, was found to be a low-cost and promising adsorbent for removal of Mn(2+) from raw water. This study was conducted to build the basic data for coating hydrated manganese oxide on the sand surface to utilize the adsorbent properties of the coating and the filtration properties of the sand. In this study, gas adsorption porosimetry and scanning electron microscopy analyses were used to investigate the surface properties of the coated layer. An energy dispersive X-ray (EDAX) technique of analysis was used to characterize metal adsorption sites on a manganese-coated sand surface. Results indicated that manganese-coated sand had more micropores and higher specific surface area, owing to attachment of manganese sand. Manganese ions penetrated into the micropores and mesopores of manganese oxide on a sandy surface; regeneration of manganese-coated sand could be achieved by soaking with pH < 2.0 acid solution. Results of EDAX analysis showed that the interfacial layer constructed the interface of manganese-coated sand. Acid and alkali resistance tests interpret a wide application range of pH for manganese-coated sand, and general temperature conditions do not affect the performance of this sand. Manganese-coated sand is potentially suitable for application as a packed bed for treatment of heavy metals from water. The results of this study can also benefit plant operational capacity data for engineering design.