Regeneration of Phenol-Saturated Activated Carbon by Supercritical Water: Effect of H2O2 and Alkali Metal Catalysts

The aim of this work was to study the supercritical water (SCW) regeneration of phenol-saturated activated carbon (AC) with the H2⁢O2 and alkali metal catalyst (Na2⁢CO3, NaOH, K2⁢CO3, and KOH) addition. The results showed that SCW could effectively regenerate AC in the 385–425°C range without any additives, but large and small amounts of phenol and dibenzofuran were present in the liquid phase, respectively, which would result in secondary pollution. The H2⁢O2 addition enhanced the decomposition of phenol and increased the CO2 yield. With the addition of H2⁢O2 and an alkali metal catalyst, SCW further decreased the phenol and dibenzofuran yields but increased the H2 and CO2 yields. Active component-supported (Cu-Ce-O, Fe-Ce-O, Ni-Zn-Pt, and Ni-Co-Pt) AC adsorbents might have decomposed some of the phenol during the phenol adsorption process, which resulted in relatively small amounts of phenol adsorbed on the AC and a decrease of the liquid (phenol and dibenzofuran) and gaseous (H2 and CO2) yields. SCW regeneration increased the surface area and pore volume of the AC and raised the adsorption capacity. The H2⁢O2 and alkali metal catalyst addition can be used to achieve the rapid, efficient, and harmless regeneration of AC in SCW at a lower temperature (385°C).