Degradation Of Organic Pharmaceuticals By Synthesised Manganese Oxides

In recent years, the contamination caused by trace-level pharmaceutical and personal care products（PPCPs） in water environment is turning into a new hot spot for relevant study. A variety of organic pharmaceuticals have been detected in municipal waste water, in ground water and even in underground water through the globe. They are posing direct or potential toxicity on aquatic life and human. The pharmaceuticals in water body are diverse in characteristics, vast in distributing regions, and low in concentration, thus leading to the inefficient treating process of common waste water treatment. Thus great amount of pharmaceuticals survived from the treatment and get into natural water body with the effluent and then participate in the water cycling process. Some territory treatment process such as AOPs, membrane are proved to be effective in this kind of contamination controlling. But all of the processes are restricted for extensive appliance because of the running condition, the complex operation, or huge operating cost.Manganese ores are widespread mineral on earth with different form and composition. Manganese dioxideis a kind of mineral which is rich in quantity and high in reductive potential. So MnO₂ can help removing the persistent organic pollutants in mild condition. It is of great importance to mine the performance and mechanism of MnO₂ on the remediation of micro organic pharmaceuticals in water body which can lay s foundation for the future application of manganese ores.In this study, the representative and persistent carbamazepine（CBZ） was selected to be the target pollutant. Two kinds of manganese dioxides were synthesized and tested for their reactive capacity, reactivingconditions and reacting mechanisms. The main results and conclusions achieved in this study were as follows:（1）Both δ-MnO₂ and colloidal-MnO₂ showed great potential in the removal of CBZ, and the removal efficiency is apparently pH relevant. When δ-MnO₂（50mg/L） reacted with CBZ（1305ug/L）, CBZ was almost totally removed within 2 hours under the pH condition of 2.6, while only less than 8.14% removal was achieved under the p H condition of 3.8 or higher. When colloidal-MnO₂（10mg/L） reacted with CBZ（1305ug/L）, CBZ was almost totally removed within 2 hours under the pH condition of 2.6, while 34.28% to 47.93% removal was achieved under the pH value of 3.8 to 6.2.（2）The pH reliance of the reaction between δ-MnO₂ results from the influence of H+concentration on the reaction rate and the reacting mechanism. The co-existing hematite would pose negative effect on the removal of CBZ. This effect mainly comes from the Fe3+ which was released from the mineral through the comparative adsorption onto the reactive site of δ-MnO₂.（3） In the presence of δ-MnO₂, CBZ was degraded into acridine, acrodine and3-aldehyde-acridone. When the initial pH is lower than pHzpc of δ-MnO₂（2.4）, the majority of CBZ molecules transformed into oganic with epoxide ring and terminally yield acridine. On the contrast, when the initial pH is higher than 2.4, the majority of CBZ molecules experienced the break down of olefinic bond and terminally yield acrodine and 3-aldehyde-acridone.（4）In the presence of colloidal-MnO₂, CBZ was degraded into three terminal products and two intermediates. The same as the situation of δ-MnO₂, CBZ could be transformed into organic with epoxide ring or experienced the break down of olefinic bond. It could also be oxidized on C10 and C11 from olefin to alcohol, and then form greater molecules through intermolecular dehydratation.