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

• UV/acetylacetone was target-selective in the photodegradation of aromatic pollutants. • UV/acetylacetone was more efficient than UV/H 2 O 2 for the degradation of dyes. • OH-substitution was favorable for the dyes to be degraded by UV/acetylacetone. • The protonated enol form of acetylacetone was the key species in photodegradation. • Photo-induced electron transfer between acetylacetone and dye played a key role. 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/H 2 O 2 . The obtained pseudo-first-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/H 2 O 2 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/H 2 O 2 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 dye-contaminated water.