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1.
土壤中流失的磷进入水体容易引起富营养化污染。目前对于铁矿物胶体结合态磷在土壤孔隙介质中的稳定性和迁移能力的认识还存在不足。本研究采用吸附试验,考察水铁矿对磷的吸附特征以及pH、离子强度和胡敏酸对磷在液相、水铁矿胶体和水铁矿固体上分布的影响;通过DLVO理论,预测水铁矿胶体结合态磷的稳定性和迁移能力。结果表明,假二级动力学模型(R~2=0.964)更适合用于描述磷在水铁矿上的吸附过程,磷在水铁矿上的吸附受液膜扩散、内部扩散和化学吸附等过程控制。Freundlich模型(R2=0.970)对等温吸附的拟合效果好,说明水铁矿对磷的吸附为多层吸附过程。从Langmuir模型参数可知,水铁矿对磷的最大理论吸附量为22.55mg·g~(-1)。水铁矿对磷的吸附能力随pH的升高而降低,随离子强度的升高而升高。然而,低离子强度和高pH有利于反应体系中水铁矿胶体的释放。无论胡敏酸是否存在,在碱性且离子强度不高(1～10mmol·L~(-1))的条件下,有约5%～20%的磷会与水铁矿胶体结合,且这些磷-水铁矿胶体之间的静电斥力较大。根据DLVO理论计算可知,这些带负电荷的胶体之间稳定性较好,在土壤中有一定迁移能力。在实际农业活动中,磷肥的过量施用可能会使大量的磷酸根离子吸附在铁矿物上,促进土壤孔隙水中形成稳定的、带负电的铁矿物胶体,这种磷-铁矿物复合胶体的迁移很可能成为磷迁移的另一种形式。本研究结果可为胶体促进下磷淋失风险评估提供理论和数据支撑。 相似文献
2.
有机酸对高岭石, 针铁矿和水铝英石吸附镉的影响 总被引：12，自引：0，他引：12
Effects of organic acids （oxalic, acetic, and citric） on adsorption characteristics of Cadmium （Cd） on soil clay minerals （kaolinite, goethite, and bayerite） were studied under different concentrations and different pH values. Although the types of organic acids and minerals were different, the effects of the organic acids on the adsorption of Cd on the minerals were similar, i.e., the amount of adsorbed Cd with an initial solution pH of 5.0 and initial Cd concentration of 35 mg L^-1 increased with increasing concentration of the organic acid in solution at lower concentrations, and decreased at higher concentrations. The percentage of Cd adsorbed on the minerals in the presence of the organic acids increased considerably with increasing pH of the solution. Meanwhile, different Cd adsorption in the presence of the organic acids, due to different properties on both organic acids and clay minerals, on kaolinite, goethite, or bayerite for different pHs or organic acid concentrations was found. 相似文献
3.
土壤矿物与溶解性有机质（DOM）的相互作用会引起DOM在矿物/水界面的结构分馏,进而影响DOM在土壤中的长期保存及其环境行为。水铁矿在环境中广泛存在,可通过两种不同方式（表面吸附或共沉淀）与DOM结合。目前,鲜有研究从分子尺度上揭示共沉淀反应诱发的DOM在水铁矿/水界面的结构分馏特性。针对此,通过共沉淀方式在C/Fe不同的溶液中制备水铁矿-DOM复合体,将传统光谱手段（如,紫外（UV）-可见光光谱、Fe K边X射线吸收光谱（XAS）等）和近年来兴起的电喷雾-傅立叶变换-离子回旋共振质谱（ESI-FT-ICR-MS）相结合,从分子水平解析共沉淀过程中DOM在水铁矿/水界面的结构分馏行为。结果显示：水铁矿-DOM复合体中Fe主要以水铁矿的形式存在,所占比例与C/Fe值有关,介于68.0%~95.9%之间。UV和ESI-FT-ICR-MS分析共同表明在共沉淀过程中,水铁矿优先固定DOM中具有高分子量的富含氧的芳香性组分（主要燃烧过程中产生的致密多环芳香类物质和维管植物来源的多酚类物质）,该分子分馏特性与前人报道的因表面吸附引发的DOM在水铁矿/水界面的分馏现象基本一致,表明无论表面吸附还是共沉淀,水铁矿均倾向于固定芳香性强的高分子量组分。此外,本研究率先发现水铁矿对DOM的结构选择性随反应时间呈一定动态变化,表现为：燃烧过程中产生的致密多环芳香类组分优先被固定在复合体中,随着反应推进,维管植物来源的多酚类组分被固定。本研究结果有助于深入理解水铁矿形成过程中,通过共沉淀作用影响DOM环境地球化学行为的分子分馏机制。 相似文献
4.
铁矿生产中要揭露地表,排弃岩石、尾矿,必然要损毁植被,破坏水土保持设施,造成人为水土流失。通过分析铁矿生产过程中产生水土流失的主要环节,提出铁矿生产中大量废石、尾矿排弃的水土保持问题,并有针对性地提出了防治措施。 相似文献
5.
还原条件下土壤中Fe(Ⅱ)催化水铁矿转化在调控营养元素和污染物的生物地球化学过程中具有重要作用。然而,作为土壤中Fe(Ⅱ)存在的主要形态之一,蒙脱石结构中Fe(Ⅱ)催化水铁矿转化的特性及其影响因素目前尚不清楚。以化学还原的蒙脱石为研究对象,探究还原态蒙脱石(rSWy-2)结构中Fe(Ⅱ)催化水铁矿转化的特性及其影响因素。结果表明,贫铁的蒙脱石结构中Fe(Ⅱ)可催化水铁矿向纤铁矿转化,反应96 h后水铁矿转化量达到83.3%。X射线衍射(XRD)、高分辨透射(HRTEM)、球差电镜(STEM)和表面吸附态Fe(Ⅱ)含量分析表明,rSWy-2结构Fe(Ⅱ)催化水铁矿转化主要经历矿物间固相吸附、电子传递和水铁矿转化三个阶段,形成的纤铁矿呈板状纳米片,尺寸大小为100～200 nm。溶液中Na+和Cl–离子对rSWy-2催化水铁矿转化影响较弱,而Ca2+、SO42-、有机质和As(Ⅲ)均对水铁矿转化具有明显的抑制作用。 相似文献
6.
水稻土氧化还原状态的变化与N_2O的释放有密切关系。为揭示水稻土中Fe对N_2O释放及反硝化功能微生物的影响,本研究选取第四纪红壤发育的水稻土,设置3个水铁矿添加水平(Fe 0,10,40μmol g~(-1)土)和两个土壤质量含水量(50%,80%)进行土壤培养试验,利用实时荧光定量PCR(real time flourescent quantification polymerase chain reaction,q PCR)和末端限制性片段长度多态性(terminal-restricted fragment length polymorphism,T-RFLP)分析技术开展研究。结果表明,N_2O排放速率升至高峰期的过程中,外源铁处理尤其是添加高量铁(40μmol g~(-1))处理导致硝态氮含量显著高于对照,而N_2O排放速率却明显低于对照;然而,高峰期后添加高量铁处理却维持了较对照显著高的N_2O排放速率;与此同时,添加水铁矿对硝酸还原酶基因(narG)和氧化亚氮还原酶基因(nosZ)丰度的影响表现出与N_2O排放相同的趋势,即N_2O排放速率升至高峰期的过程中,外源铁处理明显抑制了反硝化微生物的生长与繁殖,而高峰期后外源铁对反硝化微生物的抑制作用不明显。因此,水稻土中添加Fe(Ⅲ)对N_2O释放影响的主要原因可能是前期抑制了反硝化功能微生物的种群数量,从而减少了硝酸根的还原和N_2O的产生,而后期由于反硝化微生物数量的恢复和NO_3~-等含氮化合物的残留,使得外源铁处理的N_2O释放量明显高于对照。 相似文献
8.
研究了针铁矿和针铁矿—胡敏酸复合体对Se(Ⅳ)的吸附机制。结果表明:针铁矿和复合体对Se(Ⅳ)的最大吸附容量分别为0.202 mmol g-1和0.159 mmol g-1。针铁矿的等温吸附数据适合用Langmuir模型拟合,而Freundlich模型更适合描述复合体的等温吸附过程。针铁矿的等电点(IEP)在7.0附近,复合体的IEP3.0;当p H=4.0时,它们的表面电位分别为46.6 m V和-40.5 m V。X—射线光电子能谱(XPS)分析显示,针铁矿和复合体表面Fe2p3/2的电子结合能(B.E.)分别为711.4e V和711.5 e V,复合体表面C1s的B.E.值为284.8 e V。初始p H=4.0时,样品与Se(Ⅳ)相互作用后的主要变化体现在:(1)针铁矿和复合体的悬浮液p H分别升高至4.4和4.2,表面电位分别降低了39.08 m V和升高了1.8 m V;(2)针铁矿表面Fe(Ⅲ)的B.E.值降低了0.4 e V,但吸附态Se(Ⅳ)的B.E.值无明显变化;(3)复合体表面Fe(Ⅲ)的B.E.值降低了0.3 e V,表面C-O中C的B.E.值由285.7 e V升高至286.5e V,吸附态Se(Ⅳ)的B.E.值升高了0.6 e V。针铁矿和复合体吸附Se(Ⅳ)的主要机制包括表面配合反应(复合体表面铁羟基与HSe O3-之间存在双齿配位)、静电引力、氢键等作用。此外,复合体表面吸附态Se(Ⅳ)同时与针铁矿和胡敏酸发生了作用,形成了针铁矿—Se(Ⅳ)—胡敏酸三元体。 相似文献
9.
大西沟铁矿生态环境模糊综合评价研究 总被引：1，自引：0，他引：1
着眼于大西沟矿区的实际情况,提出一套完善的、规范化且能反映矿山生态特性的矿山生态环境质量综合定量的评价模式,实现矿山生态环境质量定量化,克服以前定性评价的模糊性和概念化,基于自然、环境和人文三方面建立一套具有代表性、可操作性的指标体系。对影响露天矿生态环境质量的因素进行分析,选取地貌、气候、植被、大气、土壤、地下水、人口、采矿8个要素及相关20个指标,构建了露天矿生态环境质量评价体系。运用层次分析法(AHP)和模糊数学综合评判法对露天矿生态环境质量进行综合评价。研究结果表明:大西沟铁矿矿山生态环境质量较好,固体废置物堆置率对矿区生态环境质量影响大,与实地调查相符,该方法对矿区生态环境质量评价是有效的,对今后矿区生态环境质量的快速评价具有现实意义。 相似文献
10.
采用批平衡试验法,比较研究了重金属镉在针铁矿和针铁矿-腐植酸复合胶体中的吸附热力学和动力学行为。结果表明,在试验浓度范围内,两种吸附剂对Cd2＋的等温吸附特征均可用Langmuir、Freundlich和Linear方程加以描述。其中以Langmuir方程的拟合效果最佳,线性相关系数为：0.991、0.999,由此推导出的最大吸附量分别为41.667和45.455mg·g^-1,表明腐植酸与针铁矿复合胶体较单一针铁矿的吸附力有所提高,且所吸附的镉均难以解吸,平均解吸率分别为5.871%和1.068%。胶体对Cd^2＋的吸附是一个快速反应过程,4h达到吸附平衡。Elovich方程是拟合吸附动力学过程的最优方程（相关系数分别为0.987和0.997）。通过计算镉在针铁矿和针铁矿-腐植酸复合胶体中的吸附自由能变化量（ΔG的绝对值均〈40kJ·mol^-1）,推测镉在两种胶体中的吸附为物理吸附过程,其吸附机理可能有氢键、偶极作用力和范德华力等作用,而不存在化学键合作用。 相似文献
11.
铁氧化物-胡敏酸复合物对磷的吸附吸附 总被引：1，自引：0，他引：1
本试验通过设置不同磷酸根浓度、 pH和不同电解质及电解质强度梯度,研究磷酸根在针铁矿-胡敏酸（HA）复合物和赤铁矿-胡敏酸（HA）复合物表面的吸附特性。X射线衍射（XRD）、 扫描电镜（SEM）和红外光谱（FTIR）图谱显示: 铁氧化物包覆胡敏酸后其内部结构特性保持不变; 氧化铁与胡敏酸通过氢键形成粒径大、 表面光滑的铁氧化物-HA复合微粒,且复合物比表面减小; 形成的氧化铁-胡敏酸复合物对磷的吸附能力增强,且针铁矿复合物的吸附能力大于赤铁矿复合物,均为多层吸附过程; pH增高抑制铁氧化物复合物对磷的吸附,同时电解质浓度增加促进复合体对磷的吸附,且反应后体系pH随之降低。 相似文献
12.
Hui Wang Jun Zhu Qingling Fu Can Hong Hongqing Hu Antonio Violante 《Journal of Soils and Sediments》2016,16(7):1911-1920
Purpose
The phosphate adsorption on natural adsorbents is of particular importance in regulating the transport and bioavailability of phosphates in environmental system. In soils, oxides are often associated with organic matter and form mineral-organic complexes. The aim of the present paper was to investigate the mechanisms of phosphate adsorption on these complexes.Materials and methods
Phosphate adsorption on uncoated and humic acid (HA)-coated iron oxide complexes was investigated at different ionic strengths and pH by isotherm experiments and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy.Results and discussion
Results showed that HA-coated iron oxide complexes caused a decrease in the specific surface area (SSA) and the isoelectric point (IEP) of oxides. Phosphate adsorption on iron oxides was insensitive to changes of ionic strength, while it increased on the complexes with increasing ionic strength. The presence of HA decreased the maximum adsorption and the affinity of phosphate on the complexes. The zeta potential of phosphate-bound iron oxides linearly reduced with the increment of phosphate surface coverage, while the zeta potential of complexes with adsorbed phosphate kept at the same level. ATR-FTIR analysis suggested the formation of phosphate-metal complexation. The presence of HA promotes the formation of the monodentate phosphate complexes at pH 4.5 and significantly influenced phosphate species at pH 8.5.Conclusions
The amount of phosphate adsorbed was reduced, and the phosphate speciation was also influenced when phosphate was adsorbed on HA-coated iron oxide complexes compared with phosphate adsorption on pure goethite and hematite.13.
支持电解质浓度对磷酸根在可变电荷土壤表面吸附和解吸的影响 总被引：2，自引：0，他引：2
研究了离子强度对2种可变电荷土壤中磷酸根吸附和解吸的影响。结果表明,当pH分别大于3.7和4.0时,红壤和砖红壤对磷酸根的吸附量随离子强度的增加而增加;当pH分别小于3.7和4.0时,红壤和砖红壤对磷酸根的吸附量随离子强度呈相反的变化趋势。电解质主要通过改变离子专性吸附面上的电位来影响磷酸根的吸附。Zeta电位的测定结果表明,当pH大于土壤胶体的等电点(IEP)时,吸附面上电位为负值,且随离子强度增加数值减小,对磷酸根的排斥力减小,土壤表面对磷酸根的吸附量增加;当pH小于IEP时,吸附面上的电位为正值,它随离子强度增加而减小,不利于磷酸根的吸附。解吸实验的结果表明,吸附于可变电荷土壤表面的磷酸根在去离子水中的解吸量高于0.1 mol L-1NaNO3体系中的解吸量。这同样由于电解质浓度对土壤表面吸附面上的电位的影响所致。 相似文献
14.
Ionic strength effects on surface charge and adsorption of phosphate and sulphate by soils 总被引：5，自引：0，他引：5
Two surface soils (Patua and Tokomaru) of contrasting mineralogy were incubated with several levels of either CaCO3 or HC1. The effects of ionic strength on pH, on surface charge, and on the adsorption of phosphate and sulphate were measured in three concentrations of NaCl. The pH at which the net surface charge was zero (point of net zero charge—PZC) was 1.8 for the Tokomaru soil and 4.6 for the Patua soil: differences that can be related to mineralogical composition. There was an analogous point of zero salt effect (PZSE) that occurred at pH 2.8 for the Tokomaru soil and at 4.6 for the Patua soil. The presence of permanent negative charge in the Tokomaru soil resulted in an increase in PZSE over PZC. The effect of ionic strength on adsorption varied greatly between phosphate and sulphate. For phosphate, there was a characteristic pH above which increasing ionic strength increased adsorption and below which the reverse occurred. This pH (PZSE for adsorption) was higher than the PZC of the soil and was 4.1 for the Tokomaru soil and 5.3 for the Patua soil. In contrast, increasing ionic strength always decreased sulphate adsorption and the adsorption curves obtained in solutions of different ionic strengths converged above pH 7.0. If increasing ionic strength decreases adsorption, the potential in the plane of adsorption must be positive. Also, if increasing ionic strength increases adsorption, the potential must be negative. This suggests that, depending upon pH, phosphate is adsorbed when the potential in the plane of adsorption is either positive or negative, whereas sulphate is absorbed only when the potential is positive. 相似文献
15.
16.
离子强度和pH对可变电荷土壤与铜离子相互作用的影响 总被引：22，自引：3，他引：22
研究了离子强度和pH对可变电荷土壤表面电荷与铜离子吸附的影响。作为对照 ,也研究了它们对恒电荷土壤黄棕壤的有关性质的影响。结果表明 ,随pH升高 ,土壤的表面负电荷增加 ,正电荷减少。对于可变电荷土壤 ,可出现电荷零点 (pH0 )。随pH升高 ,土壤对Cu2 的吸附量增大。随着离子强度增大 ,恒电荷土壤对Cu2 的吸附百分率明显降低 ,可变电荷土壤对Cu2 离子的吸附百分率也降低 ,但降低的幅度比恒电荷土壤者小得多。土壤中氧化铁的含量越高 ,降低的幅度越小。对于含 2 1 %左右游离氧化铁的铁质砖红壤 ,即使支持电解质NaNO3的浓度高达 1molL- 1,对Cu2 的吸附仍然几乎没有影响。从离子强度和pH与土壤表面电荷和铜离子吸附的关系 ,可以推测在土壤对铜离子的吸附中 ,既存在电性吸附 ,又存在专性吸附。在可变电荷土壤对铜离子的吸附中 ,专性吸附较为重要 相似文献
17.
The sorption of metal ions (Pb2+, Zn2+ and Cu2+) and soil humic acids (HA) from aqueous solutions onto mineral particles (sand, calcite and clay) was investigated using a batch equilibrium system. The sorption reactions in two- component systems (heavy metals-mineral particles and humic acids- mineral particles), as well as interactions in three-component system (heavy metals-humic acids-mineral particles) were examined. Results showed that the presence of humic acids, dissolved or bound onto mineral surfaces, considerably influenced the fixation of heavy metals. The various effects, depending on mineral type, humic concentration and specific metal-ion, were observed in three- component system. Sorption of Cu2+-ions on all minerals studied rapidly increased as the concentration of dissolved HA increased. The amount of Pb2+-ions sorbed on sand slightly decreased, while on kaolin increased between 15 and 20%. Sorption of Zn2+-ions on all minerals studied decreased at pH 4. At pH 5.5 the sorption of Zn2+-ions onto calcite decreased, while on kaolin and sand increased as a function of the humic acid concentration giving the curve with maximum at c(HA) = 2.5 mmol C L-1. At pH 6.5 sorption onto kaolin and sand increased. This effect occurs as a result of the conditional stability constant of Zn-HA complexes increasing at higher pH which in turn promotes the chelation of Zn2+-ions to mineral- bound humic substances. The enhanced sorption of metal ions from the aqueous phase in three-component systems is not only the result of mineral sorption of free metals but also the result of chelation with HA sorbed on the mineral surface. 相似文献
18.
几种吸附剂对阿特拉津的吸附及其 Zeta 电位特性研究 总被引：1，自引：0，他引：1
通过振荡吸附平衡试验,研究了蒙脱石、凹凸棒石、竹炭、木炭对阿特拉津的吸附行为,讨论了pH值、离子强度对吸附的影响,并考察了吸附剂表面的Zeta电位变化。结果表明,几种吸附剂对阿特拉津的吸附均符合Freundlich方程;竹炭、木炭的吸附能力明显高于蒙脱石和凹凸棒石。吸附剂对阿特拉津的吸附量随着悬液离子强度的增加而增加,在悬液pH一定(pH=6),离子强度为10-3mol/L NaNO3时,蒙脱石、凹凸棒石对阿特拉津的吸附量分别为538.30、609.68 mg/kg,当离子强度增加为10-2mol/L时,吸附量分别增至611.26、731.63 mg/kg;当离子强度由10-3增至10-1mol/L NaNO3时,竹炭、木炭对阿特拉津的吸附量有较多增加。当悬液pH在3~8范围时,几种吸附剂表面均带负电荷,其Zeta电位值随着pH的增加而增加,随离子强度的增加而减小。悬液离子强度一定时,随着pH的增加,吸附阿特拉津后吸附剂表面Zeta电位变化不显著。研究结果有助于从机理上解析吸附剂对有机污染物的吸附行为。 相似文献
19.
暗棕壤吸附铜离子特征及其影响因素研究 总被引：1，自引：0，他引：1
应用平衡吸附法,研究了不同pH、离子强度、温度、Cu~(2 )浓度和接触时间条件下,暗棕壤对Cu~(2 )的吸附作用,并利用热力学和动力学方程对实验结果进行了拟合。结果表明:(1)随pH提高,Cu~(2 )的吸附率增加,pH 8时的吸附率约为91%。(2)随体系离子强度增加,Cu~(2 )的吸附量先下降后增加。(3)随溶液中Cu~(2 )浓度增加,Cu~(2 )在暗棕壤上的吸附量也增加,并且在低浓度时增加比较迅速。吸附等温线可用Frendlich,Langmiur和Temkin方程很好的描述,其中又以Langmiur方程拟合程度最好。根据Langmiur方程中平衡常数(k_L)得到的热力学参数指出,反应是自发的、吸热的,但增温却没有改变Cu~(2 )在暗棕壤表面的混乱度。(4)随接触时间延长,暗棕壤对Cu~(2 )的吸附量也增大,具体表现为吸附开始的快速反应阶段和经过一段时间后的慢速反应阶段。双常数能更好地拟合暗棕壤对Cu~(2 )的吸附动力学曲线,根据一级动力学方程的反应速率常数(k_D),计算出了Cu~(2 )吸附的活化能和活化热力学参数,指出温度升高有利于提高反应的速率。 相似文献
20.
Ferricyanide, [FeIII(CN)6]3–, is an anthropogenic and potentially toxic contaminant in soil. Its adsorption on goethite has been previously studied, but not evaluated with a surface complexation model (SCM) considering the effects of pH and ionic strength. Therefore, we carried out batch experiments with ferricyanide and goethite suspensions with different ferricyanide concentrations (0.075 mM and 0.15 mM), ionic strengths (0.01 and 0.1 M), and pH (ranging from 4 to 7.4). Adsorption data were then interpreted with the 1‐pK Stern and the charge distribution model assuming monodentate inner‐sphere ferricyanide surface complexes on goethite (lg K = 10.6), which are known from infrared spectroscopy. Furthermore, we applied the SCM to ferricyanide adsorption in previous studies on ferricyanide adsorption in the presence of sulfate and on the solubility of Fe‐cyanide complexes in a suspension of a loess loam. The SCM correctly reflected ferricyanide adsorption in the batch experiments as well as the effects of pH and ionic strength. The SCM also described ferricyanide adsorption in the presence of sulfate, because the ferricyanide adsorption measured and that modeled were significantly correlated (R2 = 0.80). Furthermore, we applied the SCM to a study on the solubility of Fe‐cyanide complexes in soil under varying redox conditions so that ferricyanide adsorption on goethite and precipitation of Fe‐cyanide complexes were considered. The actual ferricyanide concentrations were rather reflected when applying the SCM compared to those modeled in an approach in which exclusively precipitation was taken into account. We conclude that ferricyanide adsorption on goethite should be included into geochemical modeling approaches on the mobility of Fe‐cyanide complexes in subsoils. 相似文献