过氧化氢驱动亚铁氧化对施氏矿形成及其吸附As(V)行为的影响研究

Effect of hydrogen peroxide-driven ferrous oxidation on the formation and As(Ⅴ) adsorption behaviors of schwertmannite

酸性矿山废水(Acid mine drainage,AMD)污染区域因pH较低、硫酸盐浓度较高易形成施氏矿,所形成的施氏矿拥有较大的比表面积和丰富的活性位点,是AMD中As的重要沉积库.施氏矿形成过程通常会因亚铁氧化速率变化呈现出不同的微观形貌和理化性质,影响As的迁移和形态转化.通过调控过氧化氢(H_(2)O_(2))滴加方式(一次性添加、0.2 h·mL^(-1)和1 h·mL^(-1))调控Fe(Ⅱ)氧化速率,形成不同的施氏矿Sch1、Sch2和Sch3,在此基础上探究合成施氏矿结构特性及对As(V)的吸附行为.结果表明:随着H_(2)O_(2)滴加速率降低,Fe(Ⅱ)氧化速率降低,所形成施氏矿的微观形貌从光滑转变为毛刺状晶须表面球形,颗粒粒径增大,比表面积大小顺序为Sch1<Sch3<Sch2;Sch2对As(Ⅴ)的吸附能力(139.2 mg·g^(-1))高于Sch1(118.9 mg·g^(-1))和Sch3(130.3 mg·g^(-1));Sch3对As(V)的吸附速率最快,结合FTIR和[SO_(4)^(2-)][/As(Ⅴ)]交换系数分析可知这与慢速形成施氏矿表面丰富的≡Fe-OH/OH2位点和As(V)交换作用贡献较大有关,进一步说明亚铁氧化速率差异导致形成不同的施氏矿,具备不同理化性质进而影响其对As(Ⅴ)的吸附行为.

Acid mine drainage(AMD)contaminated areas are prone to the formation of schwertmannite due to its low pH and high sulfate concentration.Considering its large specific surface area and abundant active sites,Schwertmannite enjoys the pivotal position on As reservoir in AMD.Notably,the variations of ferrous oxidation rate typically contribute to different microscopic morphology and physicochemical properties during the formation processes of schwertmannite,affecting the migration and morphological transformation of As.Therefore,our study regulated the oxidation of Fe(Ⅱ)to establish different schwertmannites(Sch1,Sch2 and Sch3)by modulating dropwise addition of hydrogen peroxide(H_(2)O_(2))(one-time addition,0.2 h·mL^(-1)and 1 h·mL^(-1)),on this basis of which the structural properties of synthetic schwertmannites and their adsorption behaviors of As(Ⅴ)were further explored.Data showed that as H2O2droplet acceleration rate decreased,the oxidation rate of Fe(Ⅱ)was found diminished and the micromorphology of schwertmannite changed from smooth to spherical burr whisker surface,followed by increasing particle size of schwertmannite and diverse specific surface area as Sch1-1)for As(V)was obviously strengthened compared to that of Sch1(118.9 mg·g^(-1))and Sch3(130.3 mg·g^(-1))whereas adsorption kinetics demonstrated the fastest As(V)adsorption rate of Sch3.Then,the analysis of FTIR and[SO_(4)^(2-)]/[As(V)]exchange coefficient suggested that the prominent adsorption rate was associated with the exchange between the ample≡Fe-OH/OH_(2)site on the surface of slow-forming schwertmannites and As(V).These results further indicated that the differences in ferrous oxidation rates engaged in developing schwertmannites with distinct physical and chemical properties,which in turn posted a substantial effect on their adsorption behaviors on As(V).