Interaction of Hydrogen Peroxide with Nanoporous Material Prepared by Alkaline Activation of the Brown Coal

The work analyzes applications of carbon adsorbents in catalytic wet peroxide oxidation (CWPO) being a variant of Advanced Oxidation Processes (AOPs). Under CWPO condition (concentration [Н2О2] ≤ 30 %, 20±2 °C) we have studied the activity of nanoporous adsorbent АC-К prepared by КОН-activation (800 °C, 1 h) of brown coal. We have compared АC-К with solid product of thermolysis (SPT) of brown coal formed under the same conditions without КОН. АC-К, which has a high adsorbtion activity, catalyzes decomposition of Н2О2 to form ОН-radicals. This allows to combine two environmentally important processes: concentration of organic pollutants on the surface of adsorbent and their further decomposition by ОН-radicals. Decomposition of Н2О2 in presence of АC-К or SPT is described by kinetic first-order equation and runs 20-30 times faster in contact with АC-К. Rate constants vary within the range of 0.053-0.28 min-1 (АC-К) and 0.002-0.012 min-1 (SPT) and grow under [Н2О2] increasing. Oxidative modification of АC-К and SPT surfaces under CWPO conditions has been studied. The dependence between content of ОН groups in modified АC-К (24 h) samples and [Н2О2] is described as a curve with a maximum at [Н2О2] = 10 %, where the maximum modifying effect and the highest increse in ОН-groups content (from 1.00 to 1.55 mmole/g) are observed. Modification level is negligible; only 1 % of oxidant reacts to form functional groups.