Degradation of 2,4-dichlorophenol contaminated soil by ultrasound-enhanced laccase

In this paper, ultrasound was used to enhance the degradation effect of laccase for 2,4-dichlorophenol (2,4-DCP) in soil. The degradation effect and mechanism of the ultrasound-enhanced laccase were investigated. From the results, the degradation rate of 2,4-DCP can reach as high as 51.7% under the following conditions: reaction period was 21 h, pH = 5.5, ultrasound power was 240 W, duty cycle was 50%, and moisture content was 50%. Using the ultrasound-enhanced laccase, the degradation rate of 2,4-DCP was significantly higher than that using only laccase or only ultrasound. In addition, when ultrasound was used, the optimum pH for the degradation of 2,4-DCP using laccase was increased, making the degradation technology more practical. The analysis results from high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) revealed the degradation pathway of 2,4-DCP in soil: first, 2,4-DCP gradually became phenol through dechlorination, then the small molecular organic matter was generated from the hydroxyl radical or laccase reaction.