纳米TiO2催化下表层土壤中BaP的紫外光降解

采用光解试验，研究了紫外照射与纳米TiO2联合作用下，土壤表层中苯并a]芘（BaP）的降解动力学；同时考察了催化剂的浓度、土壤pH、腐植酸和光质对BaP的光催化降解的影响。结果表明，土壤中BaP的光催化降解表现为准一级动力学。催化剂TiO2可以明显地促进土壤中BaP的光降解，较少量的催化剂（0．5％）使光解的半衰期从363．22h减少到103．26h。H^＋和OH^-离子对BaP的催化光解起促进作用，在酸性和碱性土壤中BaP光催化降解高于中性土壤，酸性土壤中的降解速率最快。腐殖质吸收紫外光照射时，产生的活性氧中间产物能够攻击BaP，添加腐植酸能增加土壤表层中BaP的光催化降解。BaP的光解半衰期从无外加腐植酸的89．34h，减少到添加浓度分别为5、10、20和40mg·kg^-1的29．37、32．69、35．73和38．51h。BaP的催化降解随波长的增加而降低，在波长254、310和365nm下，BaP降解的一级动力学常数分别为0．0078h^-1、0．0061h。和0．005h^-1。

Photodegradation of BaP on Soil Surfaces in the Presence of Nano-TiOz Under UV-light Irradiation

The dynamics of benzoa]pyrene （BaP） photodegradation on soil surfaces in the presence of nano-TiO2 under UV-light irradiation were investigated. The effects of catalyst loads, soil pH, humic acid, and irradiation wavelength on BaP photocatalytic degradation were studied respectively. The results showed that photocatalytic degradation of BaP followed the pseudo-first-order kinetics. Catalyst TiO2 accelerated the photodegradation of BaP. At low loads（0.5% wt. ） of TiO2 reduced the half-live of BaP photodegradation from 363.22 h to 103.26 h. H^＋ or OH^- ions could increase the photocatalytic reactions of BaP. The photocatalytic degradation rate of BaP was the highest in acidic soil followed by in base soil, and was the lowest in neutral soil. Supplementary humic acid（ HA ） significantly enhanced the photocatalytic degradation of BaP on soil surfaces under UV-light. Humic substances could absorb UV irradiation, the reactive oxygen intermediates were then formed and, therefore, might attack BaP in the soil and initiated its degradation. BaP photocatalytic degradation decreased with UV-wavelength increasing. The pseudo-first-order constants were 0.007 8 h^-1, 0.006 1 h^-1, and 0.005 h^-1 corresponding to the wavelength of 254 nm, 310 nm, and 365 nm, respectively.