Enhanced degradation of carbon tetrachloride by surfactant-modified zero-valent iron

Sorption of carbon tetrachloride （CT） by zero-valent iron （ZVI） is the rate-limiting step in the degradation of CT, so the sorption capacity of ZVl is of great importance. This experiment was aimed at enhancing the sorption of CT by ZVI and the degradation rate of CT by modification of surfactants. This study showed that ZVI modified by cationic surfactants has favorable synergistic effect on the degradation of CT. The CT degradation rate of ZVI modified by cetyl pyridinium bromide （CPB） was higher than that of the unmodified ZVI by 130%, and the CT degradation rate of ZVI modified by cetyl trimethyl ammonium bromide （CTAB） was higher than that of the unmodified ZVI by 81%. This study also showed that the best degradation effect is obtained at the near critical micelle concentrations （CMC） and that high loaded cationic surfactant does not have good synergistic effect on the degradation due to its hydrophilicity and the block in surface reduction sites. Furthermore degradation of CT by ZVI modified by nonionic surfactant has not positive effect on the degradation as the ionic surfactant and the ZVI modified by anionic surfactant has hardly any obvious effects on the degradation.     

零价铁渗透反应格栅中电活化技术对铁表面化学成分的影响

本文通过批-柱实验研究低压直流电流对已被NO3-钝化零价铁渗透中零价铁（ZVI）的催化活化,研究发现：加载12V低压直流电流后,阴极附近TCE的去除速率常数比钝化后ZVI的去除效率高出约4倍,低压直流电流可以催化ZVI去除TCE,去除效果的增加和电压成正相关关系;同时,低压直流电流阴极可以活化已经钝化的ZVI,活化后不加载电流时ZVI对TCE的去除效率仍是钝化后ZVI的去除效率的约3倍。经过NO3-钝化后ZVI表面的氧化膜组成以Fe3O4为主;但在加载低压直流电流后,ZVI表面同时会有理α-/β—FeOOH生成,说明低压直流电可能会使Fe3O4溶解还原。