Photochemical Degradation Of Procymidone In Aqueous Solution

The effects of different light sources, initial concentrations, pH, nitrate and nitrite, halogen ions, H₂O₂, different organic solvents, organic pigments on the photodegradation of procymidone. The main results were summarized as following:1. The photochemical degradation of procymidone in water followed the first order reaction. The photolytic rate of procymidone under UV lamp was about two times of that under high-pressure mercury lamp: its half-life was43.6min under high-pressure mercury lamp and28.2min under UV lamp. The photolytic rate of procymidone was shortest under sunlight, its half-life was about25h.2. The photodegradation of procymidone in aqueous solution under HPML irradiation was accelerated with the increasing of concentration of procymidone. The half life of photolysis was shortest （36.3min） at2mg/L. The potolytic rate at4mg/L and8mg/L levels were slower than2mg/L.3. Under HPML, the photolysis rates increased with the increase of pH value. The half life of photolysis was:45min （pH=3）、44.4min （pH=5）、42.0min （pH=7）、39.80min （pH=9）.4.Both NO₃^-、 NO₂^-showed photo-quenching effects on procymidone. The photo-quenching efficiency was improved with the increases of NO₃^-、NO₂^-concentration.5. Under HPML, The effects of halogen ions was different on the photolysis of procymidone. For Cl-、 Br-, the photo-quenching rates was lower in low proportion than in high proportion, and the photo-quenching rates was almost no different in middle and high proportions. After100min of illumination，the photo-quenching rates of Cl-were56.25%（1：1）、62.5%（10：1）, the photo-quenching rates of Br-were50%（1：1）. The photo-quenching rates was almost the same in low and middle proportions, but when in high（10:1）, there will be a great inhibition on photolysis of procymidone, After100min of illumination，the photo-quenching rates was87.5%.6. Under HPML, the photolysis rates of procymidone was quickly improved with H₂O₂. In the test, with the increasing concentration from0to20mmol/L, The half life of photolysis was from38.7min to10.4min. But when the concentration of H₂O₂was30mmol/L, the photolysis rates was shorted, the half life of photolysis was13.9min.7. Under HPML, the photolysis rates increased with the increase of temperature. The half life of photolysis was43.6min （25±0.1℃）、39.2min （45±0.1℃）.8．Under HPML, the photolysis half-lives of procymidone were44.7min、55min and 77min in isopropyl alcohol、methanol,and acetonitrile. The photolysis follows the first order kinetics.9.Under UV, methyl orange、r iboflavin and methylene blue showed photo-quenching effects on procymidone. The photo-quenching efficiency was improved with the increases of hotosensitizers concentration. After50min of illumination，the photo-quenching rates was135%（methyl orange）、220%（riboflavin） and270%（methylene blue）.