The mutual influence of speciation and combination of Cu and Pb on the photodegradation of dimethyl o-phthalate

• Simulated the photodegradation process of DMP with the existence of heavy metals.
• Investigated the inhibiting mechanism of heavy metals on the photodegradation of DMP from different perspectives.
• It was found that the main metal speciations in water which inhibited the degradation of DMP were Cu(OH)+ and Pb(OH)+.

Specific industrial application of dimethyl o-phthalate (DMP) in ore flotation has led to DMP-heavy metals combined pollution, which causes the abiotic degradation of DMP in the environment more complex. This study focused on the effect of Cu and Pb on photodegradation of DMP. The major mechanism of inhibiting effect of Cu and Pb on degradation of DMP involved their speciation and combination. It was found that the Cu (5 mg/L, I = 95.4%) and Pb (5 mg/L, I = 100%) could inhibit the photodegradation of DMP. The main species that inhibit the DMP degradation were Cu(OH)+ and Pb(OH)+, respectively. The intensity of the UV–Vis absorbance of DMP was obviously related to the concentration of Cu2+ (R2 = 0.8655) or Pb2+ (R2 = 0.9019) ions. Fluorescence quenching effect of Cu2+ (R2 > 0.9946), Pb2+ (R2 > 0.6879) on DMP is strongly correlated with the concentration of ions. And the equilibrium membrane dialysis experiment has also verified the combination of DMP and Cu, Pb. These results are useful to understand the effect mechanism of metal species on the photodegradation of organic chemicals.