过氧化氢氧化Cr(Ⅲ)_(x)Fe(Ⅲ)_(1-x)(OH)_(3)产生六价铬的规律与机制  

Cr(Ⅲ)_(x)Fe(Ⅲ)_(1-x)(OH)_(3) Oxidation by H_(2)O_(2) with Cr(Ⅵ) Production

作　　者：胡珊琼 钱傲 袁松虎[1,2] HU Shanqiong;QIAN Ao;YUAN Songhu(State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences(Wuhan),Wuhan 430078,China;Hubei Key Laboratory of Yangze Catchment Environmental Aquatic Science,China University of Geosciences(Wuhan),Wuhan 430078,China)

机构地区：[1]中国地质大学(武汉)生物地质与环境地质国家重点实验室,湖北武汉430078 [2]中国地质大学(武汉)长江流域环境水科学湖北省重点实验室,湖北武汉430078

出　　处：《安全与环境工程》2022年第5期164-174,共11页Safety and Environmental Engineering

基　　金：国家杰出青年科学基金项目(42025703)。

摘　　要：在自然过程和工程修复中,Fe(Ⅱ)还原Cr(Ⅵ)主要生成铬铁氢氧化物[Cr(Ⅲ)_(x)Fe(Ⅲ)_(1-x)(OH)_(3)],但其中Cr(Ⅲ)的复氧化会极大影响用水安全以及铬污染修复治理效果。探究了过氧化氢(H_(2)O_(2))氧化Cr(Ⅲ)_(x)Fe(Ⅲ)_(1-x)(OH)_(3)产生Cr(Ⅵ)的规律与机制,主要关注的影响因素包括H_(2)O_(2)浓度、pH值和Cr(Ⅲ)含量,并选用甲醇作为活性氧化物种[HO~·、Fe(Ⅳ)]的淬灭剂,考察淬灭剂的加入对H_(2)O_(2)氧化Cr(Ⅲ)_(x)Fe(Ⅲ)_(1-x)(OH)_(3)产生Cr(Ⅵ)的影响。试验结果表明:(1)H_(2)O_(2)氧化Cr(Ⅲ)_(0.20)Fe(Ⅲ)_(0.80)(OH)_(3)产生Cr(Ⅵ)的速率与效率随着H_(2)O_(2)浓度、pH值的增加而增大,且Cr(Ⅵ)的产生效率还会受到Cr(Ⅲ)含量(x)的影响,即在pH=5.0条件下Cr(Ⅵ)的产生效率随x的降低而增加,在pH=9.0条件下Cr(Ⅵ)的产生效率随x的降低而降低;(2)甲醇淬灭试验证明,在pH=5.0~8.0范围内,H_(2)O_(2)是引起Cr(Ⅲ)氧化的主要氧化剂,同时Fe(Ⅲ)和Cr(Ⅲ)与H_(2)O_(2)发生(类)芬顿反应产生的活性氧化物种(HO~·)还可能进一步促进Cr(Ⅲ)氧化为Cr(Ⅵ),而在pH=9.0条件下,H_(2)O_(2)是引起Cr(Ⅲ)氧化的唯一氧化剂;(3)不同pH条件下,Cr(Fe)含量可以通过影响H_(2)O_(2)的消耗、活性氧化物种的产生、矿物表面的更新、Cr(Ⅵ)的释放而影响总Cr(Ⅵ)的产生速率和效率;(4)虽然Cr(Ⅲ)_(x)Fe(Ⅲ)_(1-x)(OH)_(3)被认为能更加稳定地保存还原产生的Cr(Ⅲ),但环境中的H_(2)O_(2)在特定条件下仍有可能将Cr(Ⅲ)氧化为Cr(Ⅵ),这是因为在偏酸性条件下共存的Fe(Ⅲ)可以提供更多的Cr(Ⅵ)吸附位点,将有利于H_(2)O_(2)和HO~·等氧化Cr(Ⅲ),在偏碱性条件下共存的Fe(Ⅲ)可以竞争消耗H_(2)O_(2)而抑制其对Cr(Ⅲ)的氧化。Cr(Ⅲ)-Fe(Ⅲ) hydroxide [Cr(Ⅲ)_(x)Fe(Ⅲ)_(1-x)(OH)_(3)] is a common product of Cr(Ⅵ) reduction by Fe(Ⅱ) during natural and remediation processes.However,reoxidation of this immobilized Cr(Ⅲ) could significantly impair water quality and potentially undermine remediation efforts.Here,we study Cr(Ⅲ) oxidation from reaction of Cr(Ⅲ)_(x)Fe(Ⅲ)_(1-x)(OH)_(3) with H_(2)O_(2).The main influencing factors included H_(2)O_(2) concentration,pH and Cr(Ⅲ) content.Methanol was selected as the quencher of the active oxidizing species(HO^(·),Fe(Ⅳ)),and the effect of the quencher on the production of Cr(Ⅵ) by H_(2)O_(2) oxidation of Cr(Ⅲ)_(x)Fe_(1-x)(OH)_(3) was investigated.The resluts are as follows:(1)The rate and efficiency of Cr(Ⅵ) production increase with the increase in H_(2)O_(2) concentration and pH value.The efficiencies of Cr(Ⅵ) production are also related to the contents(x) of Cr(Ⅲ) in Cr(Ⅲ)_(x)Fe(Ⅲ)_(1-x)(OH)_(3).With the decrease in Cr(Ⅲ) content,the efficiency of Cr(Ⅵ) production increases at pH 5.0,while it decreases at pH 9.0.(2)With the addition of methanol as the quencher of reactive oxidizing species,it is suggested that H_(2)O_(2) is the main oxidant and the produced reactive oxidizing species(HO^(·)) from the Fenton-like reaction also contribute to Cr(Ⅵ) production at pH 5.0-8.0.At pH 9.0,H_(2)O_(2) is the only oxidant for Cr(Ⅵ) production.(3)Different pH value and Cr(Fe) content could affect the rate and efficiency of Cr(Ⅵ) production through influencing the consumption of H_(2)O_(2),production of reactive oxidizing species,solid surface renewal and release of oxidized Cr(Ⅵ).(4)Although Cr(Ⅲ) is considered to be stable in the form of Cr(Ⅲ)_(x)Fe(Ⅲ)_(1-x)(OH)_(3) with the co-existing Fe(Ⅲ),our study proves that Cr(Ⅲ) could still be oxidized by H_(2)O_(2) with the potential risk of Cr(Ⅵ) release.Under acidic condition,the co-existing Fe(Ⅲ) could provide more surface sites for Cr(Ⅵ) adsorption which is conducive to Cr(Ⅲ) oxidation by H_(2)O_(2)

关 键 词：六价铬 铬铁氢氧化物 三价铬 过氧化氢 活性氧化物种 铬污染修复 

分 类 号：X505[环境科学与工程—环境工程]