Emery R J, Papadaki M, Mantzavinos D
Department of Chemical Engineering, University of Leeds, Clarendon Road, Leeds LS2 9JT, United Kingdom.
Environ Technol. 2003 Dec;24(12):1491-500. doi: 10.1080/09593330309385694.
The sonochemical degradation of phenol, 2-chlorophenol and 3,4-dichlorophenol in aqueous solutions as a function of several operating conditions has been investigated. Experiments were performed at initial substrate concentrations of 0.1, 0.5 and 1 g l(-1), liquid phase volumes of 0.05, 0.07 and 0.08 l, electric power outputs of 125, 187.5 and 250 W, liquid bulk temperatures of 20, 35, 50 and 70 degrees C and an ultrasound frequency of 20 kHz. Substrate concentration was determined as a function of time by means of high performance liquid chromatography. At the conditions under consideration, the rate of degradation follows first order kinetics with respect to the substrate concentration and increases with increasing electric power and decreasing liquid volume. The relative reactivity appears to decrease in the order: 2-chlorophenol > 3,4-dichlorophenol > phenol. Measurements of liquid phase total organic carbon content showed that degradation by-products are more recalcitrant than the original substrate. The rate of 2-chlorophenol degradation was also found to decrease with decreasing liquid bulk temperature and increasing initial concentration. Addition of t-butanol as a hydroxyl radical scavenger only partially inhibited degradation, thus implying that degradation is likely to proceed via both radical-induced and thermal reactions. Addition of Fe2+ ions at concentrations as low as about 0.2 x 10(3) g l(-1) resulted in increased degradation rates; this is attributed to iron being capable of readily decomposing hydrogen peroxide (generated by water sonolysis) in a Fenton-like process to form hydroxyl radicals as well as being an effective oxidation catalyst. The implications of the use of ultrasound in wastewater treatment are also discussed.
研究了水溶液中苯酚、2-氯苯酚和3,4-二氯苯酚的声化学降解与几种操作条件的关系。实验在初始底物浓度为0.1、0.5和1 g l⁻¹、液相体积为0.05、0.07和0.08 l、电功率输出为125、187.5和250 W、液体本体温度为20、35、50和70℃以及超声频率为20 kHz的条件下进行。通过高效液相色谱法测定底物浓度随时间的变化。在所考虑的条件下，降解速率相对于底物浓度遵循一级动力学，并且随着电功率的增加和液体体积的减小而增加。相对反应活性似乎按以下顺序降低：2-氯苯酚＞3,4-二氯苯酚＞苯酚。液相总有机碳含量的测量表明，降解副产物比原始底物更难降解。还发现2-氯苯酚的降解速率随着液体本体温度的降低和初始浓度的增加而降低。添加叔丁醇作为羟基自由基清除剂仅部分抑制降解，因此意味着降解可能通过自由基诱导反应和热反应进行。添加低至约0.2×10³ g l⁻¹浓度的Fe²⁺离子会导致降解速率增加；这归因于铁能够在类芬顿过程中轻易分解（由水的声解产生的）过氧化氢以形成羟基自由基，并且铁还是一种有效的氧化催化剂。还讨论了超声在废水处理中的应用意义。
