天然铁细菌生物矿化针铁矿吸附铬离子的研究

针铁矿,特别是生物成因的针铁矿,具有较大的比表面积和较强的吸附能力,是一种良好的环境修复材料。铬在环境中常以Cr()和Cr()存在,是一种能持久存在具有氧化还原活性的毒性金属离子。本文以水体中铁细菌矿化形成的针铁矿为材料,研究了Cr()和Cr()在该生物矿化针铁矿上的吸附行为,发现其符合Langmuir与Freundlich等温吸附模型。扫描电镜、透射电镜显微成分分析表明铬在该针铁矿上的吸附存在不均匀性,明显受其显微结构影响。显微球团结构的针铁矿比螺旋状针铁矿具有更强的结合铬离子的能力。X射线光电子能谱结果表明吸附在生物矿化针铁矿表…     

几种不同类型的FeOOH吸附水溶液中铬离子研究

采用两种显微结构不同的螺旋状和管状构造的天然铁细菌矿化针铁矿和化学合成的α—FeOOH及两种有机高分子模板矿化结晶的β-FeOOH作为吸附材料，分别在pH=5和6时对含Cr^3 和Cr(Ⅵ)废水进行了吸附实验研究，结果表明，天然生物矿化针铁矿对金属阳离子和阴离子均有明显的吸附作用，其显微结构、大小和形态影响其吸附能力；纯化学合成的针铁矿对铬离子的吸附能力较低；通过有机模板合成的纳米微晶β-FeOOH对Cr^3 和Cr(Ⅵ)均有极高的去除率，这与其表面存在与有机分子络合作用、增大了其表面对金属离子和铬酸根的化学亲合力有关。     

铁(氢)氧化物矿物对有机污染物的光催化氧化作用

对水溶液中(氢)氧化铁的光催化氧化反应的发展与机理研究进行了总结,着重对近十年来应用针铁矿／过氧化氢进行光催化氧化环境中有机物的研究进展及其环境矿物学意义作了概述和探讨。采用天然生物矿化的纳米针铁矿／过氧化氢以偶氮染料甲基橙为光解模型物进行了光催化氧化的初步研究,结果表明铁细菌形成的针铁矿具有降解生物难降解的有机污染物的能力。在甲基橙溶液初始浓度为30mg／L,铁细菌矿化的针铁矿用量2．5g／L,反应体系H2O2的初始浓度97mmol／L,pH值为6．92,15W紫外灯照射2h后,甲基橙浓度可降低33％。     

针铁矿及其热活化产物除Sb(Ⅲ)效果对比

以合成针铁矿为原料,通过煅烧法获得比表面积分别为85.74和22.65 m2/g的多孔纳米赤铁矿和磁赤铁矿,通过静态实验探究了针铁矿和煅烧产物的Sb(Ⅲ)吸附性能.结果 表明,Sb(Ⅲ)吸附效率为赤铁矿＞磁赤铁矿＞针铁矿,其前二者效率显著高于针铁矿.Sb(Ⅲ)在3种矿物表面的吸附均为快速的化学吸附,吸附在2h内即可接近平衡,符合准二级动力学反应和Freundlich等温吸附模型,为自发进行的吸热反应,升高温度有利于反应的进行.在45 ℃、pH=7的条件下,针铁矿、赤铁矿和磁赤铁矿的最大吸附量分别可达16.04、50.44和33.53 mg/g.pH对赤铁矿和磁赤铁矿的Sb(Ⅲ)吸附效率影响不大,但pH升高会导致针铁矿的吸附能力降低.CO32-、SiO44-、PO43-和胡敏酸会与Sb(Ⅲ)竞争吸附位,抑制3种矿物对Sb(Ⅲ)的吸附,但这种抑制作用只在阴离子浓度较高的条件下有效.研究认为磁赤铁矿具有更多的表面活性位和较强的磁回收能力,是优于针铁矿和赤铁矿的含Sb(Ⅲ)废水处理材料.     

不同晶型羟基氧化铁(FeOOH)的形成及其在吸附去除Cr(Ⅵ)上的作用

羟基氧化铁(FeOOH)广泛存在于土壤、水体沉积物和矿山废水等环境介质中,通常以针铁矿、四方纤铁矿和纤铁矿等多种同质多像体形式存在.羟基氧化铁因具有稳定的化学性质、较高的比表面积和细微的颗粒结构,在重金属治理中被日益重视.由于矿物的环境功能与所形成矿物的性质如矿相、颗粒形貌及大小和结构界面特性密切相关,而矿物的这些性质又与其合成方法、条件密不可分,故本文介绍了羟基氧化铁的种类、结构组成、矿相稳定性及转化,重点对羟基氧化铁形成、制备方法或途径(水解沉淀、化学氧化、生物氧化与生物矿化和凝胶网格法等)及反应物和反应条件(铁盐种类、沉淀剂、pH值、温度、阴阳离子调节剂和表面活性剂等)对矿物产物性质的影响进行了综述,同时,对不同晶型羟基氧化铁在吸附去除重金属Cr(Ⅵ)上的作用的相关研究进行了概述.     

针铁矿和蒙脱石对菲的吸附解吸行为与热力学研究

采用批量振荡吸附平衡法设计针铁矿和蒙脱石对菲的吸附解吸试验,对比研究了针铁矿和蒙脱石对菲的吸附解吸行为,并考察了不同K＋浓度的溶液对蒙脱石吸附菲的影响,比较分析了线性吸附模型和Freundlich吸附模型描述矿物吸附等温线的准确性,并从吸附热力学角度探讨了矿物的吸附机理。结果表明：针铁矿和蒙脱石对菲的吸附解吸均表现出明显的非线性和解吸滞后现象;相对于线性吸附模型来说,针铁矿和蒙脱石对菲的吸附解吸更符合Freundiich吸附模型;与蒙脱石相比,针铁矿对菲的吸附更为显著,且具有更好的稳定性;溶液中软阳离子K＋的存在使蒙脱石对菲的吸附能力得到显著提高;菲在蒙脱石和针铁矿上的吸附过程是一个自发放热,同时伴随着熵值减小的过程;随着温度的升高,蒙脱石和针铁矿对菲的吸附能力均减弱。     

酸性环境下生物成因施氏矿物稳定性研究

施氏矿物是酸性矿山废水中广泛存在的次生矿物,其形成和转化受环境pH值、温度和共存离子等条件影响。文中研究了酸性环境中生物成因施氏矿物和吸附了三价砷的生物成因施氏矿物,在不同温度和钾离子浓度条件下的稳定性。结果表明,老化温度的增加促进施氏矿物相的转变:4℃条件下,在15周的老化时间里,无砷及含砷施氏矿物均未发生相转变;而在40℃条件下,经过15周的老化,则无砷和含砷施氏矿物均发生了部分相转变。此外,钾离子浓度变化可以导致施氏矿物老化产物不同:生物成因施氏矿物在0.01mM钾离子条件下老化15周后的转化产物主要为针铁矿,在100mM钾离子条件下老化产物为黄钾铁矾和针铁矿。含As(Ⅲ)施氏矿物在0.01mM钾离子条件下老化15周后没有发生相转变,在100mM钾离子条件下发生了部分相转变,产物为黄钾铁矾。生物成因施氏矿物中的As(Ⅲ)使得矿物在环境中更加稳定。     

酸性矿山废水中生物成因次生高铁矿物的形成及环境工程意义

酸性矿山废水(acid mine drainage,AMD)是一类pH低并含有大量有毒金属元素的废水。AMD及受其影响的环境中次生高铁矿物类型主要包括羟基硫酸高铁矿物(如黄铁矾和施威特曼石等)和一些含水氧化铁矿物(如针铁矿和水铁矿等),而且这些矿物在不同条件下会发生相转变,如施氏矿物向针铁矿或黄铁矾矿物相转化。基于酸性环境中生物成因次生矿物的形成会"自然钝化"或"清除"废水中铁和有毒金属这一现象所获得的启示,提出利用这些矿物作为环境吸附材料去除地下水中砷,不但吸附量大(如施氏矿物对As的吸附可高达120mg/g),而且可直接吸附As(III),还几乎不受地下水中其他元素影响。利用AMD环境中羟基硫酸高铁矿物形成的原理,可将其应用于AMD石灰中和主动处理系统中,构成"强化微生物氧化诱导成矿-石灰中和"的联合主动处理系统,以提高AMD处理效果和降低石灰用量。利用微生物强化氧化与次生矿物晶体不断生长的原理构筑生物渗透性反应墙(PRB)并和石灰石渗透沟渠耦联,形成新型的AMD联合被动处理系统,这将有助于大幅度增加处理系统的寿命和处理效率。此外,文中还探讨了上述生物成因矿物形成在AMD和地下水处理方面应用的优点以及今后需要继续研究的问题。     

铁锰氧化物在碱性条件下对镉的吸附特征研究

实验研究了不同的pH值、初始离子浓度、矿物用量、温度以及时间等因素对针铁矿和软锰矿吸附镉的影响。结果表明:在pH值从酸性到近中性的范围内,两种氧化矿物对镉的吸附量增加较快,然后在碱性条件下吸附量保持着最大值;反应前后两种氧化矿物溶液的pH值均有不同程度的变化,其中针铁矿和软锰矿的临界pH值分别为8和6.5;两种矿物对镉的吸附在6 h左右达到了吸附平衡,吸附等温线都较好地符合Freundlich等温方程式;随着两种氧化物用量的增加,其吸附量也有增加;室温下,针铁矿和软锰矿对镉的吸附效果较好。     

针铁矿/水界面反应性的实验研究

选择针铁矿对Pb2+、Cu2+、Cd2+等3种重金属离子的吸附实验,开展矿物/水界面反应性研究.金属离子(M2+)在矿物-水溶液间分配有多种表面反应机制,这些表面反应发生作用的条件主要取决于吸附质水化学性质和矿物表面荷电性,因此,溶液pH值是影响矿物/水界面反应性的关键因素.在不同pH值条件下, 表面羟基可通过发生质子化或去质子化反应而使得矿物表面产生荷电性并发生改变,而金属离子的水解则可显著加快金属羟基配合物的形成,从而进一步增强了矿物/水界面反应.本实验条件下针铁矿表面对重金属离子的吸着量随pH值升高而升高,在一个较窄的pH值范围内吸附率急剧升高,呈S形分布.针铁矿对3种不同的重金属离子的吸附能力的强弱顺序是Cu2+＞Pb2+＞Cd2+.无论是Langmuir方程还是Freundlich方程,都能较好拟合针铁矿对重金属离子的等温吸附过程.Freundlich方程的n值均在0.1～0.5之间,说明重金属离子在针铁矿表面的吸附并不能简单地归结为单配位或双配位模式,可能存在着多种吸附结合形态.表观吸附常数KM值的变化规律,说明重金属离子与针铁矿表面反应模式及其表面吸附形态发生了变化,具体的吸附形态还有待谱学研究进一步证实.     

A Study of Chromium Adsorption on Natural Goethite Biomineralized with Iron Bacteria

Goethite, especially biogenic goethite, has high specific surface area and great capacity for the adsorption of many contaminants including metal ions and organic chelates. Chromium is a redox actively toxic metal ion that exists as either Cr^Ⅲ or Cr^Ⅵ in nature, and as such it is essential to understand its behavior of adsorption on natural goethite mineralized by iron bacteria, as Gallionella and Leptothrix in water body. The adsorption of Cr^3＋ and Cr^Ⅵ on naturally biomineralized goethite is studied in this paper. The results show that both Langmuir and Freundlich adsorption isothermal models are able to accurately describe the adsorption of these two ions. Investigation of SEM/EDS, TEM/EDS indicates that the two ions do not adsorb homogeneously on goethite owing to the different microstructures of goethite, and that the microspherical goethite has a greater adsorption capacity for chromium ions than the helical one. XPS data show that redox reaction of chromium on the surface of biomineralized goethite takes place in the adsorption of both Cr^3＋ and Cr^Ⅵ. The CrvI adsorbed on biogoethite is much easier to transform into CrIII than the oxidization of Cr^Ⅲ on the bio-goethite.     

Effect of hydroxamate siderophores on Fe release and Pb(II) adsorption by goethite

Hydroxamate siderophores are biologically-synthesized, Fe(III)-specific ligands which are common in soil environments. In this paper, we report an investigation of their adsorption by the iron oxyhydroxide, goethite; their influence on goethite dissolution kinetics; and their ability to affect Pb(II) adsorption by the goethite surface. The siderophores used were desferrioxamine B (DFO-B), a fungal siderophore, and desferrioxamine D₁, an acetyl derivative of DFO-B (DFO-D1). Siderophore adsorption isotherms yielded maximum surface concentrations of 1.5 (DFO-B) or 3.5 (DFO-D1) μmol/g at pH 6.6, whereas adsorption envelopes showed either cation-like (DFO-B) or ligand-like (DFO-D1) behavior. Above pH 8, the adsorbed concentrations of both siderophores were similar. The dissolution rate of goethite in the presence of 240 μM DFO-B or DFO-D1 was 0.02 or 0.17 μmol/g hr, respectively. Comparison of these results with related literature data on the reactions between goethite and acetohydroxamic acid, a monohydroxamate ligand, suggested that the three hydroxamate groups in DFO-D1 coordinate to Fe(III) surface sites relatively independently. The results also demonstrated a significant depleting effect of 240 μM DFO-B or DFO-D1 on Pb(II) adsorption by goethite at pH > 6.5, but there was no effect of adsorbed Pb(II) on the goethite dissolution rate.     

Competitive interaction between soil-derived humic acid and phosphate on goethite

In order to better understand the influence and mechanism of soil-derived humic acid (SHA) on adsorption of P onto particles in soils, the amounts of PO₄ adsorbed by synthetic goethite (α-FeOOH) were determined at different concentrations of SHA, pH, ionic strength and order of addition of adsorbents. Addition of SHA can significantly reduce the amount of PO₄ adsorption as much as 27.8%. Both generated electrostatic field and competition for adsorption sites were responsible for the mechanism by which SHA inhibited adsorption of PO₄ by goethite. This conclusion was supported by measurement of total organic C (TOC), infrared spectral features and Zeta potential. Adsorption of PO₄ onto goethite was inversely proportional to pH. Order of addition of PO₄ and SHA can influence adsorption of PO₄ as follows: prior addition of PO₄ ⩾ simultaneous addition > prior addition of SHA. Iron and SHA apparently form complexes due to prior addition of SHA. Observations made during this study emphasized that PO₄ forms different types of complexes on the surface of goethite at different pH, which dominated the interaction of SHA and PO₄ adsorption on goethite. Based on these observations, the possible modes of SHA inhibition of PO₄ adsorption on goethite were proposed.     

膨润土、高岭石对锌的吸附和解吸

本文研究了膨润土和高岭石对Zn~(2+)的吸附和解吸。结果表明,所得到的吸附Zn~(2+)量的资料适合Freudlich和Langmuir方程,与CEC(阳离子交换量)呈正相关,Mg质粘土矿物略高于Ca质。这是由于阳离子水化度不同所致。从Ca质的膨润土和高岭石解吸Zn~(2+)状况看,粘粒表面解吸下来的Zn~(2+)数量与其吸附量呈正相关。经连续解吸后,高岭石粘粒表面吸持的Zn~(2+)量占解吸量的百分数高于膨润土。表明高岭石与Zn~(2+)亲和力高于膨润土。     

利用13X沸石分子筛净化含Pb~(2+)废水的实验研究

采用静态间歇法 ,实验研究了含Pb2 +废水的 pH值及吸附时间对 13X沸石分子筛吸附Pb2 +性能的影响 ,得出了最佳去除效果的优化条件为 :废水的 pH值接近中性 ,吸附时间 10min。通过吸附实验 ,确定了在Pb2 +初始浓度为 2 0mg/L的条件下 ,13X沸石对Pb2 +的吸附量为 2 1 4 2mg/g ,即每克沸石净化含Pb2 +废水的最大体积量约为 75 0mL。解析实验表明 ,加入沉淀剂 ,浓缩洗脱液中的Pb2 +即以PbS的形式生成沉淀 ,为回收金属铅提供了可能 ;13X沸石在循环使用 5次的条件下 ,对废水中Pb2 +的吸附率仍高达 98% ,重复使用性能良好。经处理后的净化水中Pb2 +的浓度小于 0 4mg/L ,显著低于国家废水排放标准GB8978 88的指标 ( 1 0mg/L)。 13X沸石对Pb2 +的主要吸附形式是离子交换和表面络合反应。     

Structures and stabilities of Cd(II) and Cd(II)-phthalate complexes at the goethite/water interface

The complexation of Cd(II) and Cd(II)-phthalate at the goethite/water interface were investigated by EXAFS and IR spectroscopy, by batch adsorption experiments and by potentiometric titrations at 298.15 K. The EXAFS spectra showed Cd(II) to form only inner-sphere corner-sharing complexes with the goethite surface sites in the presence and absence of phthalate. EXAFS spectra also showed the presence of Cd(II)-chloride complexes in 0.1 mol/L NaCl. IR spectra also showed phthalate to form (1) an inner-sphere complex with adsorbed corner-sharing Cd(II) surface complexes in the pH 3.5 to 9.5 and (2) an outer-sphere complex with the same type of corner-sharing Cd(II) complex however at pH > 6, in addition to the inner- and outer-sphere complexes of phthalate reported in a previous study. The potentiometric titration and the batch adsorption data were used to constrain the formation constants of the different Cd(II)-phthalate surface complexes on the dominant {110} and the {001} planes of the goethite. The models were carried out with the Charge Distribution Multisite Complexation model coupled to the Three Plane Model and can predict the molecular-scale speciation of cadmium and phthalate in the presence of goethite. Cd(II) adsorption models calibrated on a 90 m²/g goethite also could accurately predict experimental data for a 37 m²/g goethite of slightly different basic charging properties.     

Adsorption of copper onto goethite in aqueous systems

The adsorption of copper(II) onto goethite was studied as a function of pH, total dissolved copper concentration, surface area of goethite, and ionic strength. The adsorption of copper was similar to that of other hydrolyzable metals. A tenfold increase in goethite surface area had a significant effect on the adsorption edge, but a tenfold increase in the ionic strength of the medium did not effect the adsorption edge. The distribution coefficients increase sharply with increase in pH and ranged from 10 to 60,000 ml/g over a range of two and half pH units, depending on the goethite surface area and copper concentration. A tenfold decrease in ionic strength as well as a tenfold increase in surface area of goethite did not have any effect on the magnitude of distribution coefficients. Distribution coefficients were used to calculate the number of protons released per mole of copper adsorbed during the adsorption process. The average number of protons released per mole of copper adsorbed was estimated to be 1.40 ± 0.10.Managed by Martin Marietta Energy System, Inc., for the U.S. Department of Energy under contract no. DE-AC05-840R21400.     

铁（氢）氧化物悬液中磷酸盐的吸附-解吸特性研究

铁（氢）氧化物对P的吸持和释放在一定程度上决定着P的生物有效性和水体富营养化。以两种环境中常见晶质铁氧化物（针铁矿和赤铁矿）为对照,采用X射线衍射（XRD）、透射电镜（TEM）、热重分析（TGA）和孔径分析以及动力学和吸附-解吸热力学平衡等技术方法,研究了弱晶质水铁矿对P吸附-解吸特性,并探讨了相关机制。实验表明,三种矿物对P的吸附分为起始的快速反应和随后的慢速反应,它们均符合准一级动力学过程,反应中OH释放明显滞后于P吸附,P吸附经历了从外围到内囤配位、单齿到多齿配位过渡的过程,与晶质氧化铁比,水铁矿吸附容量和OH释放量更大、慢速吸附反应更快、存在缓慢扩散反应阶段,吸附容量依次是：水铁矿（436μmol／m^2）〉针铁矿（262μmol／m^2）〉赤铁矿（228μmol／m^2）,针铁矿和赤铁矿吸附P符合L（Langmuir）模型,而水铁矿更符合F（Fremldlictl）模型。中性盐介质（KCl）中在最大吸附量时P的解吸率依次为：水铁矿（85％）〈针铁矿（10％）〈赤铁矿（125％）,柠檬酸通过配体解吸和诱导溶解两种机制促进P的解吸,最大吸附量时解吸率依次是：针铁矿（25％）〈水铁矿（32％）〈赤铁矿（50％）。     

微塑料对水中甲基橙的吸附特征分析

以甲基橙(MO)为目标污染物,微塑料为载体,通过吸附动力学和等温吸附实验,比较通用塑料聚丙烯(PP)、通用工程塑料尼龙(PA)、聚甲醛(POM)和特种工程塑料聚四氟乙烯(PTFE)4种典型材质吸附MO的能力,并采用扫描电镜(SEM)、比表面积测试(BET)、显微拉曼光谱(Raman)、Zeta电位及傅立叶变换全反射衰减红外光谱(ATR-FTIR)技术手段对吸附前后PA进行表征,考察微塑料材质和PA粒径对MO吸附的影响,从而探究其可能存在的吸附机理。结果表明不同材质微塑料对MO的吸附能力具有明显差异性。其中,PA对MO的吸附量最大,可达7.39 mg/g,PA吸附MO的动力学过程包括起始的快速反应阶段和随后的慢速反应阶段,吸附过程符合二级动力学方程;等温吸附实验结果表明MO在PA上属于非均质化学吸附。静电作用及氢键的形成是造成不同材质微塑料吸附能力差异的主要原因,微塑料粒径大小与其对MO的吸附量呈显著负相关关系(R2=0.995, P<0.05),这与微塑料可提供的有效吸附位点息息相关。本研究可以为科学评价微塑料复杂的环境行为以及作为载体协同迁移污染物的能力提供依据。     

Uranium(VI) adsorption and surface complexation modeling onto vadose sediments from the Savannah River Site

Uranium U(VI) adsorption was measured as function of pH (3–10) on goethite, kaolinite, quartz, two binary mixtures of goethite and kaolinite, and a vadose zone sediment collected on The Department of Energy’s Savannah River Site (SRS), the clay mineral fraction of which is composed largely of kaolinite and goethite. Diffuse-layer surface complexation models were parameterized using the code PEST together with PHREEQC to fit U(VI) sorption data for the pure goethite, kaolinite, and quartz. U(VI) adsorption on kaolinite and goethite was modeled as the formation of two bidentate U(VI) complexes at mineral edge sites on a variable charge site. U(VI) adsorption on quartz was described using a one-site diffuse-layer with the formation of bidentate complex on a variable charge site. These models were used to predict U(VI) adsorption on the binary sorbent mixtures and the SRS sediment using a simple component-additivity approach. In general, the predicted adsorption edges were in good agreement with measured data, with statistically similar goodness of fit compared to that obtained for the pure mineral systems.