2,4-DNT removal in intimately coupled photobiocatalysis: the roles of adsorption, photolysis, photocatalysis, and biotransformation.

The removal of 2,4-dinitrotoluene (2,4-DNT) by simultaneous UV-photo(cata)lysis and biodegradation was explored using intimately coupled photolysis/photocatalysis and biodegradation (ICPB) with two novel porous carriers. First, a porous ceramic carrier was used to attach the photocatalyst (TiO₂) on its exterior and accumulate biomass in its interior. UV irradiation alone decomposed 71% of the 2,4-DNT in 60 h, and TiO₂ catalyst improved the photolysis to 77%. Second, a macroporous sponge carrier was used to strongly adsorb 2,4-DNT and protect microorganisms from 2,4-DNT inhibition and UV irradiation. The main photolytic reactions were reduction of the nitryl to amino and hydrolysis of the amino to release NH₄⁺. The main biodegradation reactions were oxidative release of NO₃⁻ and accelerated reductive release of NH₄⁺. ICPB more thoroughly released inorganic N, with nearly equal amounts being oxidized to nitrate and reduced to ammonium. The genera Burkholderia and Bacillus were found inside the sponge carriers, and they are associated with biodegradation of DNT and its photolysis intermediates. Therefore, using an adsorbent and macroporous biofilm carrier enabled the effective removal of 2,4-DNT by ICPB.