Degradation and mineralization mechanism of phenol by BiPO4 photocatalysis assisted with H2O2

Degradation and mineralization of phenol by BiPO4 photocatalysis assisted with H2O2 were attempted in order to know the effects of H2O2 on BiPO4 photocatalysis and the detailed mechanism. Both conversion and mineralization rate of phenol by BiPO4 photocatalysis could be accelerated obviously by addition of H2O2 above 30 ppm, whereas low concentration of H2O2 could inhibit the mineralization rate of phenol due to the consumption of photogenerated holes (h+) by the adsorbed H2O2 on BiPO4. The enhancement of efficiency by adequate H2O2 resulted from the OH produced by H2O2 photolysis and the increased separation efficiency of e− and h+ by the capture of e− by H2O2. OH was efficient in conversion of phenol to its intermediates but it could not transfer the carboxylic ones without CH bond into CO2 and could induce the formation of dimeric intermediates. Therefore, phenol could not be completely mineralized by H2O2. In contrast to H2O2 photolysis, the main active species of BiPO4 photocatalysis were photogenerated holes, which were efficient in fast ring cleavage and mineralization of carboxylic intermediates. This resulted in the complete mineralization of phenol by BiPO4 in 4 h. Synergy of BiPO4 and adequate H2O2 could raise the removal efficiency of phenol greatly.