负载硼的针铁矿结构表征研究

人工合成了针铁矿（Goethite）及其负载硼的氧化物（硼吸附态针铁矿Ad—B—Goethite，硼包被态针铁矿Oc—B—Goethite），用IR、X射线衍射、TEM对其进行表征，测定了它的比表面积及其对锰离子的吸附性能。IR分析表明，负载硼的针铁矿较之普通针铁矿在888cm。处的Fe—OH—Fe表面羟基弯曲振动、1000cm^-1处的表面Fe—OH弯曲振动及3100cm^-1处的游离羟基峰均减弱；硼吸附态针铁矿在458．5cm^-1处，硼包被态针铁矿在527．2cm^-1和476．5cm^-1处出现了与BO3和B（O，OH）4的弯曲振动有关的吸收峰。X射线衍射分析表明硼吸附态针铁矿的晶形与普通针铁矿相似，而硼包被态针铁矿的衍射吸收峰的位置、个数和相对强度都发生了变化。从TEM图上可看出硼包被态针铁矿的晶体明显要小些。实验测得3种矿物的比表面积分别是：普通针铁矿108．4m^2g^-1，吸附态针铁矿88．69m^2g^-1，包被态针铁矿120．5m^2g^-1。对锰离子的吸附量为硼包被态针铁矿明显大于硼吸附态针铁矿大于普通针铁矿。结果表明：硼包被态针铁矿（Oc—B—goethite）中B进入了针铁矿的品格，影响晶体的生长，使晶体的结晶性较差，晶体较小、比表面积增大，对锰离子的净吸附能力强。这也说明，土壤中的硼不仅起到植物营养的作用，其在形成负载硼的铁氧化物后有利于减轻土壤锰的毒害。     

Fe(Ⅱ)存在条件下氧化铁-高岭石复合物的形成与转化

氧化铁-高岭石复合物是我国南方土壤的重要组分,也是影响这些土壤理化性质的主要因子。本文以Fe(Ⅱ)为添加剂,研究了晶质氧化铁-高岭石复合物的形成与转化过程及其影响因素。结果表明,Fe(Ⅱ)可加速晶质氧化铁-高岭石复合物的形成,在一定程度上克服了高岭石对晶质氧化铁形成的抑制作用。当Fe(Ⅱ)/Fe(Ⅲ)摩尔比(R)在0.04~0.06时,Fe(Ⅱ)可加速纤铁矿、针铁矿、赤铁矿-高岭石复合物的形成;当R≥0.1时,可快速形成磁铁矿-高岭石复合物。在温度50~60℃、pH5~6条件下,Fe(Ⅱ)可加速纤铁矿、针铁矿-高岭石复合物的形成;温度80℃及中性附近时,可加速赤铁矿-高岭石复合物的形成;pH9时,则形成了磁铁矿-高岭石复合物。高岭石的存在减弱了Fe(Ⅱ)对晶质氧化铁形成的催化效果,也可影响产物类型和结晶形貌。上述结果可为自然环境中氧化铁以及氧化铁-高岭石复合物的形成转化过程提供重要参考。     

磷和柠檬酸共存对高岭石和针铁矿吸附铅的影响

通过平衡吸附试验及矿物电动电位(Zeta电位)的变化分析,研究了磷(P)和柠檬酸(CA)共存对针铁矿和高岭石吸附铅的影响。结果表明:(1)针铁矿和高岭石对铅的吸附量随柠檬酸浓度的升高呈现"峰形"曲线变化,铅吸附量达到峰值的柠檬酸浓度均为0.5 mmol L~(-1),不同浓度磷存在下柠檬酸对矿物吸附Pb2+量有不同程度增加。(2)随着磷添加浓度的增加,两种矿物对铅吸附量均呈增加趋势,磷添加浓度分别为1 mmol L~(-1)和0.6 mmol L~(-1)时,针铁矿和高岭石吸附铅量达到平衡;当处理中添加不同浓度柠檬酸,两种矿物均表现为对铅的吸附量增加,且随着柠檬酸浓度增加促进铅吸附的作用增强,说明在磷及试验浓度柠檬酸存在下促进了矿物对铅的吸附。(3)高岭石体系中,加入磷或(和)柠檬酸后,Zeta电位-pH曲线向负值方向位移,降低程度大小顺序为1.0 mmol L~(-1) P+0.5mmol L~(-1) CA0.5 mmol L~(-1) CA1.0 mmol L~(-1) P,说明高岭石表面增加的负电荷也部分增加了其对铅的电性吸附;添加磷和柠檬酸处理针铁矿的Zeta电位显著降低,且随着体系pH的升高其Zeta电位没有明显变化,表明磷和柠檬酸均主要是通过吸附到针铁矿表面而增加对铅的专性吸附。     

高岭石在醋酸-醋酸铵缓冲体系中的溶解特征

室温下(25℃±1℃)采用间歇法(batchmethod)模拟研究高岭石在pH5.5、pH4.5和pH3.5的HAC/NH4AC缓冲液中的溶解。实验结果表明:质子能够促进高岭石Al和Si的释放,且Al、Si的释放能力随反应液酸度的增加而增强,Al、Si溶解的一致性与酸度有关。pH5.5时,可能因Al的沉积而导致整个实验期间Al、Si释放表观不一致;pH4.5和pH3.5时,反应前期Al优先释放,而在反应后期Al、Si趋于一致。pH5.5、pH4.5和pH3.5的HAC/NH4AC缓冲液中高岭石溶解速率分别为:3.09×10-14mol/(m2·s)、6.31×10-14mol/(m2·s)和1.13×10-13mol/(m2·s)。HAC/NH4AC缓冲液中质子作用下高岭石溶解反应级数和速率常数分别为0.28和1.12×10-12。     

铁氧化物-胡敏酸复合物对磷的吸附吸附

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。     

柠檬酸对高岭石的溶解作用

采用间歇法(batch method)研究柠檬酸对高岭石溶解的影响。结果表明:低浓度(0.02mmolL-1)柠檬酸可促进高岭石中Ca2+、Mg2+、Na+少量的释放。当柠檬酸浓度分别为1.0mmolL-1和8mmolL-1时,Ca2+,Mg2+,K+,Na+,Si,Al3+阳离子的释放量也相应地增加。释放的Ca2+、Mg2+主要来自高岭石表面的吸附,而Na+、K+则来自高岭石的溶解。     

铁铝氧化物–层状硅酸盐矿物互作对Cr (Ⅵ)和As (Ⅴ)吸附的影响

以高岭石、蒙脱土、针铁矿和三水铝石四种单一典型土壤矿物以及针铁矿-蒙脱石和三水铝石-蒙脱石（质量比为1:1）两种代表性土壤矿物复合体为吸附材料，采用吸附平衡实验、能谱分析（(EDS）、红外光谱、扫描电镜、酸碱滴定和zeta电位测定等方法，研究了铁铝氧化物与层状硅酸盐矿物之间的相互作用对Cr(Ⅵ)和As(Ⅴ)吸附的影响及其机制。吸附平衡实验和EDS实验结果表明，两种复合体对Cr(Ⅵ)和As(Ⅴ)的吸附容量均小于其两种组成矿物单一体系吸附量的平均值，即铁铝氧化物与蒙脱石的互作降低了这些氧化物对Cr(Ⅵ)和As(Ⅴ)的吸附能力。表面性质表征结果表明，与蒙脱石复合后，针铁矿与三水铝石表面的正电荷均被完全中和，电荷符号发生反转。与理论值相比，三水铝石-蒙脱石复合体的表面位点总浓度无明显变化，比表面积减小。针铁矿-蒙脱石复合体的比表面积与理论值无明显差异，但矿物表面位点浓度减小，表面羟基红外吸收峰强度减弱。氧化物与层状硅酸盐矿物互作改变了矿物表面性质，这可能是导致氧化物对Cr(Ⅵ)和As(Ⅴ)的吸附能力降低的主要原因。当评估污染元素在土壤中有效性时应当考虑土壤固相组分间的互作对离子吸附的影响。     

土壤中水合氧化物型表面的化学区分——Ⅱ.电荷零点

本文研究了氧化物对红壤、高岭土和合成无定形铝硅酸盐的电荷零点的影响,并讨论了土壤中水合氧化物型表面的区分。结果表明,水合氧化物型表面可进一步区分为电荷性质完全不同的两类亚表面。在所研究的土壤和粘土样本中,有高ZPC的氧化铁(Fe-OH)和氧化铝(Al-OH)表面,是带可变正电荷的亚表面,使样本的ZPC趋于上升;而有低ZPC的氧化硅(Si-OH)表面,是带可变负电荷的亚表面,使样本的ZPC趋于下降。合成无定形铝硅酸盐的电荷零点与样本的Al₂O₃/Si₂,摩尔比呈显著的正相关。     

磷酸盐对土壤胶体和矿物表面吸附酸性磷酸酶的影响

研究了系列浓度磷酸盐体系中 ,酸性磷酸酶在黄棕壤、砖红壤胶体和高岭石、针铁矿及δ MnO2 表面的吸附特点。结果表明 :随着磷酸盐浓度升高 ,磷酸酶在土壤胶体和矿物上的等温吸附曲线类型逐渐由L型向C型转化 ,等温吸附方程由Langmuir方程向线性方程转化 ,这种转化可能与磷酸和酶在胶体矿物表面对不同点位的利用及其能量特点有关。随着体系中磷酸盐浓度的增加 ,酶吸附量呈现先急剧下降后逐渐稳定的趋势。磷酸盐对土壤胶体和矿物上酶吸附的影响决定于矿物表面的类型特别是羟基的数量、体系中磷酸盐浓度及酶的加入量。针铁矿及含铁铝氧化物较多的砖红壤胶体对酶的吸附受磷酸盐的抑制作用最为显著。     

硫酸根离子添加顺序对可变电荷土壤吸附铜离子的影响

研究了SO2-4添加顺序对三种可变电荷土壤(昆明铁质砖红壤、徐闻砖红壤和江西红壤)吸附Cu2+的影响,作为对照,也研究了其对恒电荷土壤(黄棕壤、棕壤)以及两种不同矿物(高岭石与针铁矿)吸附铜离子的影响。实验结果表明,在同等条件下,SO2-4添加顺序对两类表面性质不同的土壤吸附Cu2+有着不同的影响。对于恒电荷土壤,SO2-4添加顺序对土壤吸附Cu2+几乎没有影响。同等pH条件下,对可变电荷表面而言,加入CuSO4者具有最高的Cu2+吸附率;对昆明砖红壤、徐闻砖红壤以及针铁矿和高岭石而言,先加入Cu2+者相对先加入SO2-4者Cu2+吸附率更高;对江西红壤而言,上述这个次序则刚好相反。SO2-4浓度和有机质去除对同等pH条件下铜离子吸附率高低的排序并无实质性影响。     

高岭石,蒙脱石和针铁矿对泥炭腐殖酸的吸附和分离

Sorption of humic acid (HA) on mineral surfaces has a profound interest regarding the fate of hydrophobic organic contaminants (HOCs) and carbon sequestration in soils. The objective of our study is to determine the fractionation behavior of HA upon sorption on mineral surfaces with varying surface properties. HA was coated sequentially on kaolinite (1:1 clay), montmorillonite (2:1 clay), and goethite (iron oxide) for four times. The unadsorbed HA fractions were characterized by elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), and solid state ¹³C nuclear magnetic resonance spectroscopy (NMR). The mineral-HA complexes were characterized by DRIFT. Polarity index [(N+O)/C] revealed higher polarity of the unadsorbed HA fractions after coating on kaolinite, reflecting that relatively higher polarity fractions of HA remain unadsorbed. Sorption of aliphatic alcohol fraction along with carbohydrate was prominent on kaolinite surface. DRIFT results of the unadsorbed HA fractions indicated more sorption of aliphatic moieties on both kaolinite and montmorillonite. DRIFT results of the unadsorbed HA fractions after sorption on kaolinite and goethite showed the sorption of the proteinaceous fractions of HA. The HA fractions obtained after coating on goethite showed significant sorption of carboxylic moieties. The results mentioned above comply reasonably well with the DRIFT spectra of the mineral-HA complexes. ¹³C NMR results showed higher sorption of anomeric C on kaolinite surface. Higher sorption of paraffinic fraction was observed on montmorillonite. NMR data inferred the sorption of carboxylic moieties on goethite surface. Overall, this study showed that aliphatic moieties of HA preferentially sorbed on kaolinite and montmorillonite, while carboxylic functional groups play a significant role in sorption of HA on goethite. The sorbed fractions of HA may modify the mineral surface properties, and thus, the interaction with organic contaminants.     

Adsorption Kineties of Pb(2+) and Cu(2+) on Variable Charge Soils andMinerals V .Effects of Temperature and Ionic Strength

The study results of the effects of temperature and ionic strength on the adsorption kinetics of Pb2+ and Cu2+ by latosol, red soil and kaolinite coated with Mn oxide showed that Pbr" and Cur" adsorption by all samples, as a whole, increased with raising temperature. Temperature also increased both values of Xm (the amount of ion adsorbed at equilibrium) and k (kinetics constant) of Pb2+ and Cu2+ The activation energies of Pb2+ adsorption were kaolin-Mn>red soil>goethite and those of Cu2+ were latosol>red soil>kaolin-Mn>goethite. For a given single sample the activation energy of Cu2+ was greater than that of Pb2+. Raising ionic strength decreased the adsorption of Pb2+ and Cu2+ by latosol, red soil and kaolinite coated with Mn oxide but increased Pb2+ and Cu2+ adsorption by goethite. The contrary results could be explained by the different changes in ion forms of Pb2+ or Cu2+ and in surface charge characteristics of latosol, red soil, kaolin-Mn and goethite. Increasiclg supporting electrolyte concentration in-creased Xm and k in goethite systems but decreased and k in kaolin-Mn systems. All the timedependent data fitted the surface secondorder equation very well.]     

Munsell Colors of Soils Simulated by Mixtures of Goethite and Hematite with Kaolinite

The colors and color patterns of soils are widely used to infer other soil properties. It is desirable to understand, at least semiquantitatively, the effect various pigments have on soil color. The purpose of this study was to determine how hematite and goethite pigments influence soil color. We prepared simulated soil mixtures consisting of kaolinite and 2.5, 5, 10, 20, 40, 80, 160, 320, 640, and 1000 g kg^?1 of pigment (either a synthetic goethite, one of two synthetic hematites, or a mixture of goethite and hematite). We determined the reflectance spectra of the samples, and calculated their colors in the Munsell system. For hematite and goethite pigments mixed with kaolinite, more than half of the change in hue occurred as the Hm/(Hm+Gt) ratio increased from 0 to 0.25, and hue changed relatively little as the Hm/(Hm+Gt) ratio increased from 0.50 to 1.00. Most of the change in color occurred as pigment content increased from 2.5 to 160 g kg^?1. Doubling of pigment content from 160 to 320 g kg^?1 had very little impact on the colors of the mixtures, while further increases in pigment content between 320 and 1000 g kg^?1 caused some changes in color, but less than for the 2.5 to 160 g kg^?1 range. A one unit increase in chroma corresponded approximately to a doubling of pigment content in the series 2.5, 5, 10, 20, 40, 80, 160 g kg^?1 for the goethite as well as the hematite pigments studied. For one hematite, hues became progressively redder and changed by more than 5 units of hue as pigment content increased from 0.25 to 160 g kg^?1.     

AN ANALYSIS OF PORE SIZE IN ILLITE-KAOLINITE MIXTURES

When API-9 kaolinite and Willalooka illite clays were mixed in various proportions, the pore-size distributions obtained using nitrogen sorption and mercury injection techniques were found to be characteristic of neither of the components but showed a progressive reduction in the pore size as the concentration of illite was increased. The plate separation of the mixtures showed a marked decrease with initial added illite, approaching that of the illite when the mixture contained approximately 40 per cent illite. This is indicative of a homogeneous mixture in which the fine illite particles fill in the pores bounded by the relatively coarse kaolinite particles. The relationship between particle dimensions (derived from crystallographic parameters and specific surface area) and pore size of single clays and clay mixtures is consistent with a model in which slit-shaped pores result from the parallel interleaving of clay crystals for the single clays. Some deviations occur for the mixtures.     

Hydrolysis of cellobiose by β-glucosidase in the presence of soil minerals - Interactions at solid-liquid interfaces and effects on enzyme activity levels

Extracellular enzymatic activities in soils are essential for the cycling of organic matter. These activities take place in multiphase environments where solid phases profoundly affect biocatalytic activities. Aspergillus niger is ubiquitous in soils; its β-glucosidase plays an important role in the degradation of cellulose, and therefore in the global carbon cycle and in the turnover of soil organic matter. However, the information on the interactions of this protein with soil minerals is very limited, and even less is known about their consequences for the hydrolysis of the natural substrate cellobiose. We therefore characterised the sorptive interactions of this enzyme with the soil minerals montmorillonite, kaolinite and goethite and quantified the resulting changes in the hydrolysis rate of cellobiose. Fractions of adsorbed protein, and the resulting catalytic activity loss, were lower for montmorillonite than for kaolinite and goethite at given experimental conditions; adsorption was 9.7 ± 7.3% for montmorillonite, 70.3 ± 3.1% for kaolinite and 71.4 ± 1.8% for goethite, respectively. Adsorption of the protein to the minerals caused a total decrease in the catalytic activity of 18.8 ± 3.4% for kaolinite and 17.9 ± 4.7% for goethite whereas it was not significant for montmorillonite. The average catalytic activity lost by the pool of adsorbed molecules was 26.8% for kaolinite and 25.0% for goethite. Both the amount of adsorbed protein and the resulting loss of catalytic activity were found to be independent of the specific surface areas yet were influenced by the electrical properties of the mineral surfaces. Under the experimental conditions, montmorillonite and kaolinite are negatively charged whereas goethite is positively charged. However, because of the adsorption of phosphate anions from the buffer, a charge reversal took place at the surface of goethite. This was confirmed by zeta (ζ)-potential measurements in phosphate buffer, revealing negative values for all the tested minerals. Indeed goethite interacted with the enzyme as a negatively charged surface: the amount of adsorbed protein and the resulting catalytic activity loss were very similar to those of kaolinite. Our results show that, even if an important fraction of β-glucosidase is adsorbed to the minerals, the catalytic activity is largely retained. We suggest that this strong activity retention in presence of soil minerals results from a selective pressure on A. niger, which benefits from the activity of the adsorbed, and thus stabilized, enzyme pool.     

铁铝氧化物和高岭石对转化酶的吸附及活性的影响

Experiments were conducted to study the influences of synthetic bayerite, non-crystalline aluminum oxide (N-AlOH), goethite, non-crystalline iron oxide (N-FeOH) and kaolinite on the adsorption, activity, kinetics and thermal stability of invertase. Adsorption of invertase on iron, aluminum oxides fitted Langmuir equation. The amount of invertase held on the minerals followed the sequence kaolinite > goethite > N-AlOH > bayerite > N-FeOH. No correlation was found between enzyme adsorption and the specific surface area of minerals examined. The differences in the surface structure of minerals and the arrangement of enzymatic molecules on mineral surfaces led to the different capacities of minerals for enzyme adsorption. The adsorption of invertase on bayerite, N-AlOH, goethite, N-FeOH and kaolinite was differently affected by pH. The order for the activity of invertase adsorbed on minerals was N-FeOH > N-AlOH > bayerite > reak goethite > kaolinite. The inhibition effect of minerals on enzyme activity was kaolinite > crystalline oxides > non-crystalline oxides. The pH optimum of iron oxide- and aluminum oxide-invertase complexes was similar to that of free enzyme (pH 4.0), whereas the pH optimum of kaolinite-invertase complex was one pH unit higher than that of free enzyme. The affinity to substrate and the maximum reaction velocity as well as the thermal stability of combined invertase were lower than those of the free enzyme.     

Adsorption Kinetics of Pb2+ and Cu2+ on Variable Charge Soils and Minerals: Ⅲ. Adsorption Kinetics of Pb2+ Within 30 Minutes

The adsorption kinetics of Pb2+ on different soils and minerals with variable charges was studied by the two ion-selective electrode technique at different pH and concentrations. The results showed that more than 95% of adsorption on all the samples occurred during the first 5 minutes. All adsorption time-dependent data could fit the surface second-order equation very well. The values of Xm were goethite > kaolinite, and latosol > red soil at the same initial reaction concentration. The values of k were kaolinite > > goethite, and latosol > red soil at the same reaction pH and initial concentration.     

Sb(V)在三种矿物表面的吸附行为

用研究了蒙脱土、高岭土和针铁矿在不同的pH与离子强度的介质条件下对Sb(V)的吸附及解吸行为。3种矿物对Sb(V)的吸附能力差别较大,蒙脱土的吸附量远大于针铁矿和高岭土,针铁矿与高岭土的吸附能力相近。pH对Sb(V)在3种矿物表面的吸附行为影响显著。随pH的升高,Sb(V)的吸附均减弱。吸附在高岭土表面的Sb(V)易解吸,而针铁矿和蒙脱土表面的Sb(V)不易解吸。随离子强度升高,高岭土对Sb(V)的吸附减弱;离子强度对Sb(V)在针铁矿和蒙脱土表面吸附的影响较小。     

Transformation of haematite and Al-poor goethite to Al-rich goethite and associated yellowing in a ferralitic clay soil profile of the middle Amazon Basin (Manaus, Brazil)

The red and yellow colours of ferralitic soils in the tropics have for long intrigued pedologists. We have investigated the upward yellowing in a 10-m thick profile representative of the Ferralsols of the plateaux of the Manaus region of Brazil. We determined changes in the nature and crystal chemistry of their Fe oxides by optical and Mössbauer spectroscopy as well as Rietveld refinement of X-ray diffraction patterns. We attribute the upward yellowing of the soil to a progressive transformation of the Fe oxides at nearly invariant iron contents. Aluminium in contrast is strongly mobilized in the uppermost clay-depleted topsoil where there is preferential dissolution of kaolinite and crystallization of gibbsite. Haematite decreases from 35 to 10% of the Fe oxides from the bottom to the top of the profile and the particles become smaller (75–10 nm). Its Al for Fe-substitution remains almost unchanged (10–15 mol %). The average Al-substitution rate of goethite increases from 25 to 33 mol %, and its mean crystal diameter remains in the range 20–40 nm. The proportion of Al-rich goethite (33 mol %) increases at the expense of less Al-substituted Fe oxides (haematite and goethite). This conversion with restricted transfer of iron means that the amount of Al stored in Fe oxides gradually increases. Kaolinite, haematite and Al-poor goethite are thus witnesses of earlier stages of ferralitization of the soil. In contrast, Al-rich goethite and gibbsite initiate the alitization (or bauxitization) of the soil. They correspond to the last generation of soil minerals, which most likely reflects the present-day weathering conditions. The progressive replacement of kaolinite, haematite and Al-poor goethite by new generations of Al-rich goethite and gibbsite attests to greater activities of water and aluminium and smaller activity of aqueous silica in the topsoil than in the subsoil. We interpret this as a consequence of longer periods of wetting in the topsoil that could result from soil aging, more humid climate or both.