Key structural features that determine the selectivity of UV/acetylacetone for the degradation of aromatic pollutants when compared to UV/H2O2

Acetylacetone (AA) has proven to be a potent photo-activator for the decolorization of dyes. However, there is very limited information on the quantitative structure-activity relationship (QSAR) and the mechanisms of dye degradation by UV/AA. Herein, the photolysis of 65 aromatic compounds (dyes and dye precursors) was investigated at three pH values (4.0, 6.0, 9.0) by UV/AA and UV/H2O2. The obtained pseudofirst-order photodegradation rate constants (k(1)) were processed using statistical analysis. The correlation between the k(1) values and the number of photons absorbed by AA, together with the observed pH effect, suggested that the protonated enol structure of AA plays a crucial role in the photodecolorization of dyes. According to quantum chemical computation, photo-induced direct electron transfer between the excited state of AA and the dye was the main mechanism in the UV/AA process. QSAR models demonstrated that the molecular size and stability were the key factors that determined the efficiency of UV/H2O2 for dye degradation. Statistically, the UV/AA process was target-selective and suffered less from the inner filter effect, which made it more effective than the UV/H2O2 process for dye degradation. The selectivity of the UV/AA process was mainly embodied in the substituent effects: dyes with hydroxyl groups in conjugated systems decomposed faster than those with nitro-substitution or ortho-substituted sulfonate groups. The results can be used for the selection of appropriate photochemical approaches for the treatment of dyecontaminated water. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This study found that acetylacetone is an effective photo-activator for dye decolorization under UV/AA, with molecular size and stability determining the efficiency of UV/H2O2 for dye degradation. The UV/AA process is more selective and effective than the UV/H2O2 process for dye degradation.