Introduction of 5,10,15,20-tetrakis(4-hydroxyphenyl)-porphine iron(III) into humic acid via formaldehyde polycondensation

To stabilize an iron(III)-porphyrin catalyst in the presence of peroxide such as KHSO5, 5,10,15,20-tetrakis(4-hydroxyphenyl)-porphine iron(III) (FeTPP(OH)4) was introduced into a humic acid (HA) via formaldehyde polycondensation to produce a “resol” catalyst. FeTPP(OH)4 can have four phenolic hydroxyl groups for HA-binding. The self-degradation kinetics for prepared resol catalysts using FeTPP(OH)4 were compared with those synthesized prepared from 5-(p-hydroxyphenyl)-5,10,15,20-tetrasulfonatophenylporphine iron(III) (FeTPPSOH) that has one site for HA-binding. In the presence of KHSO5, half-lives of the self-degradation was much larger in resol catalysts using FeTPP(OH)4 (3.4–3.5 s), compared to those using FeTPPSOH (0.08 s). These results show that use of FeTPP(OH)4 for the synthesis of resol catalysts is useful for stabilization of iron(III)-porphyrin catalyst and retardation of the self-degradation. In addition, the catalytic activity of prepared resol catalysts was evaluated by 2,4,6-trichlorophenol (TrCP) oxidation. In particular, mineralization to CO2 was significantly greater for the resol catalysts (17–18%) than for FeTPP(OH)4 alone (4%). These results indicate that resol catalysts effectively enhance oxidative degradation of TrCP due to retardation of catalyst self-degradation.

5,10,15,20-Tetrakis(4-hydroxyphenyl)-porphine iron(III), having four phenolic hydroxyl groups, was covalently introduced into humic acid via formaldehyde polycondensation. The synthesized catalysts retarded their inactivation via the self-degradation and had higher catalytic activity to the oxidative degradation of 2,4,6-trichlorophenol. Figure optionsDownload as PowerPoint slide