Potassium Permanganate and Sodium Silicate Co-modified Bamboo Charcoal for Efficient Treatment of Ammonia Nitrogen Pollution in Rare Earth Mines: Performance and Mechanism

The ammonia nitrogen (AN) pollution caused by the mining of weathered crust elution-deposited rare earth ore (WCED-REO) poses a huge threat to the environment. Therefore, developing an economical and efficient treatment for AN pollution is extremely necessary. Jiangxi province has abundant bamboo resources. In this work, the cheap and easily available bamboo charcoal (BC) was used as the raw material of the adsorbent, and potassium permanganate (KMnO 4 ) and sodium silicate (Na 2 SiO 3 ) co-modified bamboo charcoal (KSBC) was fabricated. The results showed that KSBC contained rich microporous structure with abundant functional groups. When the initial pH of the solution was 7.0, the initial AN concentration was 100 mg/L, and the solid-to-liquid ratio was 10 g/L, the maximum adsorption capacity of NH 4 + -N by KSBC was 7.2 mg/g, which was 4 times larger than that of BC. We also carried out interference experiments with representative ions in WCED-REO areas, and KSBC showed a good performance in the presence of some interferents. Density functional theory (DFT) calculation was also used to further elucidate the reason of reducing participation from interferents. The adsorption mechanism mainly includes electrostatic interaction, surface complexation, and ion exchange interaction. The results of desorption experiments showed that the contribution of electrostatic interaction and ion exchange to the removal of AN was 86.29% of the adsorption efficiency, implying a good regeneration potential. These results could provide theoretical support and guidance for development and application of BC-based biochar adsorption material in the treatment of nitrogen-contaminated water in WCED-REO areas. Graphical Abstract