腐殖质对二氧化锰引起的五氯酚转化反应的影响

研究了在二氧化锰催化引起的五氯酚的转化反应中,腐殖质前身化合物的加入对五氯酚去除率的影响,并以p-coumaricacid为代表研究了体系pH值、反应时间、二氧化锰的质量浓度以及腐殖质前生物的浓度和分子结构对去除率的影响。结果表明,反应的最佳pH值范围是4～4.70,去除率在80%左右。五氯酚在24h内去除速率较快,去除率达到75%左右;反应到168h,去除速率趋于0,去除率达到80%左右。相同条件下,无p-coumaricacid的对照体系中,对应的反应时间内去除率仅分别为20%和25%左右。五氯酚的去除率还随二氧化锰质量浓度和p-coumaricacid浓度的增加而增大。当二氧化锰的质量浓度由0增加到100g·L-1时,去除率由0增大为95%;而当p-coumaricacid的浓度由0增加到1mmol·L-1时,去除率由25%增大到100%左右。此外,不同腐殖质前身物的分子结构和浓度对去除率分别起到了提高、不明显改变和降低的作用。

Effect of humic substances on the transformation of pentachlorophenol in the presence of manganese dioxide

The effect of humic precursors as reactive co-substrates on the transformation of pentachlorophenol mediated by manga-nese dioxide was investigated. Reaction conditions including pH, incubation time, the amount of manganese dioxide, and the con-centration and molecular structure of humic precursors using p-coumaric acid as a representative were also inspected. The results indicated that about 80% of PCP removal was achieved at the optimal pH range of 4~4.70. In the presence of p-coumaric acid, the rate of PCP removal was very fast within 24 hours during incubation, and 75% of PCP was transformed. When the incubation reached 168 hours, the rate of PCP removal was tended to zero, and about 80% of PCP was removed. Without p-coumaric acid, PCP removal was only 20% within 24 hours and 25% within 168 hours respectively under the same reaction condition. PCP removal also increased with the amount of manganese dioxide and the concentration of p-coumaric acid. When the amount of MnO2 ranged from 0 to 100 g/L, the transformation of PCP ranged from 0 to 95%. As the same, when the concentration of p-coumaric acid ranged from 0 to 1 mmol/L, the transformation of PCP ranged from 25% to nearly 100%. In addition, different molecular structure and the concen-tration of humic precursors led to three results that enhance PCP removal; no effect on PCP removal or reduce PCP removal.