Investigation of B-N-Fe and Si-N-Fe catalysts ability to remove phenol compounds from water in presence of ozone and UV irradiation

Catalytic oxidation methods involving reactive HO radicals are perspective for dissolved organic matter (DOM) removal from water. Ozonation and catalytic oxidation under UV are common sources of HO radicals if oxygen-containing catalysts are used. Transition metal oxides doped with platinum group metals possess high activity in the oxidation of DOM exposed to UV irradiation. Raff-Fenton systems, ferric-oxalate complexes in presence of hydrogen peroxide both have photo activity in homogeneous catalysis. Iron catalysts are attractive not only from the economic point of view - they are environmentally friendly and are of interest to create a variety of catalytic systems (Fenton, Raff- Fenton, ferric-oxalic, etc.) by combining heterogeneous and homogeneous catalysis. Thus, the iron composition of silicon and boron nitrides studied previously showed high catalytic activity in the processes of oxalic acid and formaldehyde degradation - they are a source of iron for the combined catalysis. In the present study, we investigated the possibility of using such catalysts for water purification of a number of phenolic compounds (phenol, hydroquinone, catechol). For this purpose the following tasks were performed: evaluation of adsorption and catalytic activity of B-N-Fe and Si-N-Fe compositions in the degradation of phenolic compounds in ozone and UV radiation as a function of the phase composition and dispersion of the composites, time of exposure, quantity of oxalic acid added, estimation of phenol end products oxidation, testing the most active catalysts on real objects. It is shown that the catalytic activity of the tested materials is virtually independent of their phase composition, but increases with decreasing dispersion. The highest degree of degradation of pollutants studied (100%) is achieved by ozonation in the presence of B-N-Fe composites. Oxidation of phenolic compounds (90%) under UV is also achieved in the presence of B-N-Fe composites with oxalic acid addition, due to formation of photoactive ferric-oxalate complexes. It is revealed by GC-MS that the end products of phenol degradation in ozonation are p-quinone, hydroquinone (<10 %). Ferric-oxalate system produced 2-hydroxypropanoic and oxalic acid (<10 %), o-benzoquinone and catechol (<10 %). Boron nitride based composites were tested in ozonation for phenol removal from wastewater in Tomsk companies. Residual concentrations of pollutants in water after its catalytic oxidation do not exceed the "statutory limit reset" (0.02 mg/L).

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