钾化蒙脱石对硝基苯的强化吸附机理研究

测定分析蒙脱石的孔隙结构及化学组成,采用批量平衡实验研究了改性后蒙脱石对硝基苯(NB)的吸附特性,并从动力学及热力学角度探讨了NB的强化吸附作用机理。研究结果表明,吸附过程符合伪二级动力学方程,反应经过快速吸附、减速吸附和平衡吸附3个阶段,12 h达到吸附平衡。K+-蒙脱石对NB的吸附符合Henry方程,吸附过程主要由分配作用所致,随着改性的K+浓度越高,离子强度增强,EDA作用效果显著。另外,K+-蒙脱石对NB的吸附是一个放热过程,在303～323 K范围内,反应的吉布斯自由能变小,吸附反应为自发过程。     

蒙脱石与滑石矿物对菲吸附-解吸行为的对比研究

采用批量处理平衡实验,考察蒙脱石与滑石矿物对菲的吸附解吸行为。采用Henry和Freundlich方程对其吸附等温线进行分析比较,并着重考察软阳离子K+对上述两种矿物吸附菲的影响机制。研究结果表明:蒙脱石对菲的吸附等温线表现出明显的非线性,吸附/解吸有滞后现象,Freundlich方程最符合其吸附/解吸曲线;滑石吸附菲的能力较之蒙脱石的强,且吸附呈线性,其吸附曲线与Henry方程吻合程度最好。此外,随着溶液中K+离子浓度增加,蒙脱石吸附菲的能力增强,而滑石吸附菲的能力减弱,说明软阳离子K+对蒙脱石吸附菲有明显的强化作用,而对滑石吸附菲却有抑制作用。说明黏土矿物内部结构与表面理化性质控制着污染物的吸附-解吸环境行为,从而影响着PAHs等污染物的迁移转化。     

TDTMA+-柱撑蒙脱石吸附硝基苯的实验研究

以阳离子表面活性剂(十四烷基三甲基溴化铵,TDTMBA)为柱撑剂,在不同浓度条件下(0.2 CEC～2.5 CEC)制备了一系列柱撑蒙脱石,并通过XRD对有机蒙脱石进行表征,研究季铵盐离子在层间的排列结构.同时针对TDTMA -柱撑蒙脱石对硝基苯的吸附进行研究.实验结果表明,吸附去除率受硝基苯的初始浓度、反应时间等因素的影响,而与pH值没有太大的关系.经过柱撑改性后,粘土对硝基苯的吸附能力较原土有了明显的提高.随着层间柱撑浓度的增大,柱撑蒙脱石对硝基苯的吸附量也增大.另外钙基蒙脱石和平卧双层,倾斜单层以及倾斜双层的结构的TDTMA -柱撑蒙脱石对硝基苯的吸附等温线符Freundlich和Langmuir等温方程,假三层结构的TDTMA -柱撑蒙脱石对硝基苯的吸附等温线符合Linear等温方程,这表明前者是以表面吸附为主,后者是以分配作用为主.     

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。     

聚合羟基铁铝蒙脱石复合体对磷的吸附行为及其动力学

在一定条件下利用钠基化蒙脱石合成了聚合羟基铝-蒙脱石复合体(HyA1-Mt)、2个不同铁含量的聚合羟基铁-蒙脱石复合体(HyFe-Mt)和3个不同Fe:Al摩尔比的聚合羟基铁铝-蒙脱石复合体(HyFeAl-Mt),研究了酸性和弱酸性条件下(pH=3.0～6.5)以上蒙脱石复合体对磷的吸附行为和动力学特征。结果表明,HyFeAl-Mt对磷的吸附容量大于HyA1-Mt和HyFe-Mt复合体,且随着Fe:Al摩尔比的增大,对磷的吸附容量依次增加。随pH升高,蒙脱石复合体对磷的吸附量容量变小。但随Fe:Al摩尔比增大,HyFeAl-Mt复合体零电荷点(pHZPC)升高,pH对磷的吸附的影响越来越小,HyFe-Mt对磷的吸附几乎不受pH的影响。随Fe:A1摩尔比的增大,HyFeAl-Mt对磷的吸附能力增强,铁含量是磷吸附量的重要控制因素。磷在各蒙脱石复合体上的吸附实验数据可很好地用Langmuir吸附等温方程拟合。磷在各蒙脱石复合体上的吸附动力学过程可分为快速和慢速两个过程,快速过程中的动力学受铁含量影响明显。动力学数据可同时用准二级动力学方程和Elovich方程拟合。     

载铜蒙脱石吸附亚甲基蓝的试验研究

采用离子交换法制得载铜蒙脱石,研究蒙脱石和载铜蒙脱石对亚甲基蓝（MB）的吸附性能,结果表明载铜蒙脱石的吸附能力低于蒙脱石。温度、介质pH值和离子强度对吸附剂的吸附性能有不同程度的影响;蒙脱石和载铜蒙脱石吸附MB等温线较好地符合BET和Langmuir等温方程,其吸附过程均为热力学自发过程。     

蒙脱石及其热改性产物对间二硝基苯的吸附性能对比

在不同的温度条件下,制备了几种热处理蒙脱石样品,并对这些材料进行了结构与表面性质的表征,采用批吸附实验方法开展蒙脱石及其热活化产物样品对间二硝基苯(m-DNB)的吸附性能对比研究。结果表明,随着热处理温度的升高,蒙脱石层间距(d_(001))因层间结合水甚至结构水脱去而减小至0.98 nm,接近理论值,热处理温度在650℃以下时,同时吸附效果也呈现逐渐增强。适宜的K~+浓度条件下,EDA(电子供体-受体)和K~+-NO_2(阳离子-极性)两种作用效应均能够得到强化。650℃以上时,吸附效果没有得到增强,反而更差。Langmuir较之Freundlich模型能更好的拟合上述吸附过程。而且,蒙脱石及其热改性产物对m-DNB的吸附是一个放热反应,吸附反应为自发过程。     

钙基蒙脱石对抗肿瘤新药卡莫氟的吸附及其缓释性能研究

采用恒温振荡法和透析法进行蒙脱石对抗肿瘤新药卡莫氟(简称HCFU)的吸附和体外释放研究,并采用两种体外释放模型对HCFU在3种不同pH值释放液中的释放实验数据进行拟合,考察两种不同性质蒙脱石对HCFU的吸附性能对比,探讨其吸附和释放行为,以及蒙脱石作为HCFU缓释载体的可行性。结果表明:蒙脱石对HCFU的吸附能力与其晶体结构性质及其纯度密切相关,阳离子交换容量较大、蒙脱石含量较高的MMT-2对HCFU的吸附率、载药量均大于MMT-1,其相应的吸附率和载药量分别达到17.60%和2.28%;蒙脱石对HCFU具有较好的缓释作用,是一种性能优异的药物缓释载体,其释放能力受释放溶液的pH值影响显著,在pH1.2的释放介质中HCFU的释放浓度和累积释放量最大,其次为pH7.4,pH5.0的最小;一级动力学模型能较好地拟合和描述HCFU/MMT复合物在pH7.4和pH1.2释放溶液中的体外释放度随时间的变化,而在pH5.0的释放溶液中,HCFU的释放过程更符合Korsmeyer-Peppas模型。拟合结果表明HCFU从HCFU/MMT复合物中释放的过程随着释放介质的pH值不同而改变,是物理扩散、离子交换作用和药物溶解等多种形式同时存在的释放行为。     

聚羟基铝柱撑蒙脱石吸附重金属离子实验研究

利用keggin离子对蒙脱石进行柱撑制得聚羟基铝柱撑蒙脱石,研究柱撑蒙脱石对Cu^2＋,Cd^2＋,Cr^3＋3种重金属离子的吸附。结果表明：未经焙烧的柱撑蒙脱石对Cu^2＋,Cr^3＋离子的吸附性要比原矿好,而经400℃下焙烧的柱撑蒙脱石对Cd^2＋则有更好的吸附性。用腐殖酸对柱撑蒙脱石改性能提高柱撑蒙脱石对3种重金属离子的吸附性能,柱撑蒙脱石对3种重金属离子的吸附量都随pH值的升高而增加。另外还对柱撑蒙脱石对3种重金属离子的吸附动力学进行了研究．发现其动力学吸附过程可用Elovicb方程和一级动力学方程进行较好的拟合。     

蒙脱石/胡敏酸复合体对重金属离子吸附实验研究

主要研究了蒙脱石吸附胡敏酸后形成的复合体对Cu2 、Cd2 、Cr3 3种重金属离子的吸附.实验结果表明:用胡敏酸对蒙脱石改性后能提高其对3种重金属离子的吸附性能,胡敏酸浓度越大,吸附性能提高程度越大,3种重金属离子的Langmuir吸附等温线线性相关都能达到0.99以上.蒙脱石/胡敏酸复合体对3种重金属离子的吸附量都随pH值的升高而增加,随离子强度的增加而减小.另外还对其吸附动力学进行了研究,发现可用Elovicb方程和双常数方程对吸附过程进行较好地拟合.     

不同形态洛美沙星在高岭土上的吸附特性

本研究采用批实验方法探究了不同形态洛美沙星(LOM)在高岭土上的吸附特性。LOM吸附动力学结果符合准二级反应动力学方程,吸附等温数据可用Langmuir方程很好地拟合。随着溶液pH值增大,洛美沙星吸附量先增大后减小,且pH值在洛美沙星pKa1与pKa2间吸附量达到最大。不同形态LOM在高岭土上的吸附量排序为LOM^±>LOM^+>LOM^-。溶液离子强度和无机阳离子种类对LOM^+在高岭土上的吸附影响十分微弱,但均明显抑制了LOM^±的吸附,且离子强度越大,抑制作用越明显。不同无机阳离子抑制程度排序为Mg^2+>Ca^2+>K^+>Na^+。LOM^+在高岭土上的吸附机理主要是内层络合和阳离子交换;LOM^±在高岭土上的吸附机理主要是阳离子交换、氢键作用和静电引力作用;LOM^-与高岭土表面存在较大静电斥力,导致吸附量很小,可能是外层表面络合引起少量的吸附。     

污灌土壤对铅的吸附和解吸特性

为了解污灌土壤对铅的吸附-解吸机制,进行不同条件下的吸附-解吸试验。结果表明：污灌土壤对铅的吸附量随铅初始浓度的增大,呈现先强烈吸附再缓和的过程。Langmuir模式对污灌土壤等温吸附铅的拟合效果最好,其饱和吸附量为7.84 mg/g。亚砷酸盐的存在会阻碍污灌土壤对Pb²⁺的吸附,亚砷酸盐加入前后污灌土壤对铅的吸附率从99.9％～100％下降到97.8％～99.0％。加亚砷酸盐条件下污灌土壤对铅的等温吸附模式以Freundlich模式的拟合效果最好。污灌土壤对吸附态铅的解吸量随解吸振荡时间的延长而不断增加,且解吸率随时间增加总体趋于降低。Elovich方程和幂函数方程均能很好地拟合污灌土壤对铅的解吸动力学过程,尤其是Elovich方程的拟合效果最为显著。     

Sorption of Zr~(4+) and Hf~(4+) onto Hydrous Ferric Oxide and Their Fractionation Behaviors:An experimental Study

1 Introduction Coherent element pairs (Y3+-Ho3+, Zr4+-Hf4+, Nb5+-Ta5+ and Sr2+-Eu2+) have the same valences and very similar ionic radii. They are seldom fractionated during silicate mineral/melt interaction systems because the partitioning of these element pairs between melts and minerals is tightly controlled by charge valence and crystal structure (lattice site size) or ionic radius. The concentration ratios of these pairs in igneous rocks are close to the chondritic values (Y/Ho=28, Zr…     

Sorption of selenium(VI) onto anatase: Macroscopic and microscopic characterization

The sorption of selenium(VI) onto pure anatase, a polymorph of titanium dioxide, was investigated. At the macroscopic level, batch experiments and electrophoretic mobility measurements were performed. Selenium(VI) retention was found to be pH-dependent, i.e. sorption of selenium(VI) decreases with increasing pH (pH range 3.5-11). Selenium(VI) sorption dependence on the ionic strength was also evidenced, i.e. sorption increases while the ionic strength decreases. Electrophoretic mobility measurements showed that selenium(VI) sorption had no effect on the isoelectric point of anatase. At the microscopic level, XPS (X-ray Photoelectron Spectroscopy) measurements evidenced the absence of reduction of selenium(VI) during the sorption process. Furthermore, the nature of the sorbed surface species at the anatase/liquid interface was elucidated using Attenuated Total Reflection Fourier-Transform Infrared (ATR FT-IR) spectroscopy. The spectroscopic results strongly suggested the formation of outer-sphere complexes on the whole pH range, in agreement with batch sorption experiments and electrophoretic mobility findings.     

Adsorption of Fe~(3+) Ions from Aqueous Solution by Natural and Synthetic Apatites: Kinetic,Equilibrium and Thermodynamic Study

In this study, the adsorption kinetics, equilibrium and thermodynamics of Fe3+ ions on natural (NAP) and synthetic (HAP) apaties were examined. The adsorption efficiency of Fe3+ onto the NAP and HAP was increased with increasing temperature. The kinetics of adsorption of Fe3+ ions was discussed using three kinetic models, the pseudo-first-order, the pseudo-second-order and the intra-particle diffusion model. The experimental data fitted very well the pseudo-second-order kinetic model. The initial sorption rate and the activation energy were also calculated. The activation energy of the sorption was calculated as 37.15 and 49.84 kJ·mol 1 for NAP and HAP, respectively. Experimental results were also analysed by the Langmuir, Freundlich and Dubinin–Redushkevich (D–R) isotherm equations at different temperatures. RL separation factor for Langmuir and the n value for Freundlich isotherm show that Fe3+ ions are favorably adsorbed by NAP and HAP. Various thermodynamic parameters such as enthalpy (ΔH), Gibbs free energy (ΔG) and entropy (ΔS) changes were computed and the results showed that the adsorption of Fe3+ ions onto NAP and HAP were spontaneous and endothermic in nature.     

The influence of hydrous Mn–Zn oxides on diel cycling of Zn in an alkaline stream draining abandoned mine lands

Many mining-impacted streams in western Montana with pH near or above neutrality display large (up to 500%) diel cycles in dissolved Zn concentrations. The streams in question typically contain boulders coated with a thin biofilm, as well as black mineral crusts composed of hydrous Mn–Zn oxides. Laboratory mesocosm experiments simulating diel behavior in High Ore Creek (one of the Montana streams with particularly high Zn concentrations) show that the Zn cycles are not caused by 24-h changes in streamflow or hyporheic exchange, but rather to reversible in-stream processes that are driven by the solar cycle and its attendant influence on pH and water temperature (T). Laboratory experiments using natural Mn–Zn precipitates from the creek show that the mobilities of Zn and Mn increase nearly an order of magnitude for each unit decrease in pH, and decrease 2.4-fold for an increase in T from 5 to 20 °C. The response of dissolved metal concentration to small changes in either pH or T was rapid and reversible, and dissolved Zn concentrations were roughly an order of magnitude higher than Mn. These observations are best explained by sorption of Zn²⁺ and Mn²⁺ onto the secondary Mn–Zn oxide surfaces. From the T-dependence of residual metal concentrations in solution, approximate adsorption enthalpies of +50 kJ/mol (Zn) and +46 kJ/mol (Mn) were obtained, which are within the range of enthalpy values reported in the literature for sorption of divalent metal cations onto hydrous metal oxides. Using the derived pH- and T-dependencies from the experiments, good agreement is shown between predicted and observed diel Zn cycles for several historical data sets collected from High Ore Creek.     

Sorption of Cu and Pb to kaolinite-fulvic acid colloids: Assessment of sorbent interactions

The sorption of Cu(II) and Pb(II) to kaolinite-fulvic acid colloids was investigated by potentiometric titrations. To assess the possible interactions between kaolinite and fulvic acid during metal sorption, experimental sorption isotherms were compared with predictions based on a linear additivity model (LAM). Suspensions of 5 g L⁻¹ kaolinite and 0.03 g L⁻¹ fulvic acid in 0.01 M NaNO₃ were titrated with Cu and Pb solutions, respectively. The suspension pH was kept constant at pH 4, 6, or 8. The free ion activities of Cu²⁺ and Pb²⁺ were monitored in the titration vessel using ion selective electrodes. Total dissolved concentrations of metals (by ICP-MS) and fulvic acid (by UV-absorption) were determined in samples taken after each titration step. The amounts of metals sorbed to the solid phase, comprised of kaolinite plus surface-bound fulvic acid, were calculated by difference. Compared to pure kaolinite, addition of fulvic acid to the clay strongly increased metal sorption to the solid phase. This effect was more pronounced at pH 4 and 6 than at pH 8, because more fulvic acid was sorbed to the kaolinite surface under acidic conditions. Addition of Pb enhanced the sorption of fulvic acid onto kaolinite at pH 6 and 8, but not at pH 4. Addition of Cu had no effect on the sorption of fulvic acid onto kaolinite. In the LAM, metal sorption to the kaolinite surface was predicted by a two-site, 1-pK basic Stern model and metal sorption to the fulvic acid was calculated with the NICA-Donnan model, respectively. The LAM provided good predictions of Cu sorption to the kaolinite-fulvic acid colloids over the entire range in pH and free Cu²⁺ ion activity (10⁻¹² to 10⁻⁵). The sorption of Pb was slightly underestimated by the LAM under most conditions. A fractionation of the fulvic acid during sorption to kaolinite was observed, but this could not explain the observed deviations of the LAM predictions from the experimental Pb sorption isotherms.     

Competitive sorption of intermixed heavy metals in water repellent soil in Southern Australia

In water repellent soil, Cr, Pb and Cu showed higher adsorption intensities than Zn, Cd and Ni did. Soil water repellency is much more widespread than formerly thought. In order to promote fertility and productivity, the irrigation of recycled water onto water repellent soil may be an applied technology to be used in some areas of Southern Australia. Therefore, heavy metals in recycled water potentially enter into the soil. The competitive sorption and retention capacity of heavy metals in soil are important to be determined, especially considering the special geochemical origin of water repellent soil that was caused by waxes on or between the soil particles. Batch equilibrium sorption experiments on Cd, Cr, Cu, Ni, Pb and Zn in their typical proportion in recycled water were conducted in water repellent soil. The sorption intensity, sorption isotherm in the experiments together showed that Cr, Pb and Cu have higher sorption intensity than those of Zn, Ni and Cd in the competitive system. The risk assessment for the application of recycled water onto water repellent soil is definitely necessary, especially for the metal cations with relatively weak sorption.     

Sorption and desorption of dissolved organic phosphorus onto iron (oxyhydr)oxides in seawater

Sorption of phosphorus (P) onto particulate surfaces significantly influences dissolved P concentrations in aquatic environments. We present results of a study contrasting the sorption behavior of several dissolved organic phosphorus (DOP) compounds and phosphate onto three commonly occurring iron (oxyhydr)oxides (Fe_ox): ferrihydrite, goethite, and hematite. The DOP compounds were chosen to represent a range of molecular weights and structures, and include: adenosine triphosphate (ATP), adenosine monophosphate (AMP), glucose-6-phosphate (G6P), and aminoethylphosphonic acid (AEP).All P compounds displayed decreasing sorption as a function of crystallinity of the Fe_ox substrate, with ferrihydrite adsorbing the most, hematite the least. In general, maximum sorption density decreased with increasing molecular weight of P compound; sorption of G6P onto goethite and hematite excepted. P compound size and structure, and the nature of the Fe_ox substrate all appear to play a role dictating relative sorption capacity. Failure of a simple, 1-step sorption-desorption model to describe the data suggests that P sorption cannot be explained by a simple balance between sorption and desorption. Instead, the data are consistent with a 2-step sorption model consisting of an initial rapid surface sorption, followed by a slow, solid-state diffusion of P from surface sites into particle interiors. Desorption experiments provide additional support for the 2-step sorption model.Without exception, DOP compounds showed less efficient sorption than did orthophosphate. This suggests that in aquatic systems enriched in reactive Fe_ox, whether as suspended particulates in the water column or in benthic sediments, DOP bioavailability may exceed that of orthophosphate. Since biological uptake of P from DOP requires enzymatic cleavage of orthophosphate, a system enriched in DOP relative to orthophosphate may impact ecosystem community structure.