Abstract:In recent years, lots of research work has been carried out for nickel recovery from the nickeliferous laterite through atmospheric acid leaching. The separation and enrichment of nickel in the leachate from the atmospheric acid leaching of the nickeliferous laterite was preliminarily investigated in laboratory. A new idea that sulfate crystallization can be used to separate and enrich the nickel within nickeliferous laterite is presented in this paper, which is beneficial to the nickel recovery from the nickeliferous laterite. The sulfate crystallization experiments under different conditions indicate that the crystals crystallized from the atmospheric sulfuric acid leachate of nickeliferous laterite are mainly MgSO₄·H₂O. More significantly, the ratio of Fe and Ni is reduced greatly in the solid solution, which is conducive to the further purification and recovery of the nickel, though it is not effective to separate the Fe and Ni in the liquor by the simple sulfate crystallization. The utilization of sulfate crystallization to separate and enrich the nickel of nickeliferous laterite not only reduces the energy consumption but also contributes to the environment. It is thus a simple and economical industrial method. It is feasible to separate and recover the nickel from the atmospheric sulfuric acid leachate of the nickeliferous laterite.

Abstract:A new alkali dissolution method is used to extract aluminum hydroxide from high-alumina fly ash in this study. The first step alkali dissolution is to obtain desiliconized fly ash with relatively high Al₂O₃/SiO₂ ratio. The amorphous silica in the fly ash is partly leached when the fly ash is leached with 8 mol/L sodium hydroxide solution at 95℃. The desiliconized fly ash is then used for the second step alkali dissolution as the material. The desiliconized fly ash mixed with CaO are leached with 18～20 mol/L sodium hydroxide solution at 260～280℃ and the dissolution efficiency of Al₂O₃ reaches 85%. Then reduced causticity ratio, deep desilication and carbonation decomposition are carried out on the basis of acquired sodium aluminate solution. The features of the prepared product of aluminum hydroxide are determined by XRD, SEM and chemical analysis. The results show that the aluminum hydroxide has fine crystal and slight particle aggregate sphere 70～80μm in diameter. The product can satisfy Class 1 of the China National Chemical Standard GB/T4294-1997. Compared with other technologies, this technology can avoid high temperature sintering procedure and realize low energy consumption, and the process is quite consistent with the environment protection idea.

Abstract:The unburned spherical low-density zeolite composite paddings 4～8 mm in particle size with natural zeolite as the main raw material, cement as the binder, spherical particles of polystyrene as the core were prepared through the procedure of compounding, sphere making, screening, and maintenance. Based on testing the void fraction, apparent density, compression strength and other characteristics of materials in the preparation, the authors have concluded the optimal conditions of process combination in the preparation of low density composite paddings as follows. Weight proportion of zeolite∶cement is 75%∶25% and maintenance is 7～10 d under normal conditions. Under such conditions, the void fraction is 47.4%, apparent density is 1.23 g/cm³, compression strength is 61.5 N, and piled density is 0.647 g/cm³. Scanning electron microscopy clearly shows that before the biofilm formation the surface is rough, and the interior has numerous pores, whereas after the biofilm formation, a large number of microbes exist on the surface and in the internal. The number of microbes is twice that of the fly ash biological filter. When the method is applied at the ambient temperature below 15℃ under BAF biofilm, the ammonia and nitrogen removal rate of the unburned spherical low-density zeolite composite paddings even reaches 96%. The high ammonia and nitrogen removal efficiency shows a good prospect of the composite paddings in advanced treatment of wastewater denitrification.

Abstract:Mullite nanocomposites powders were successfully synthesized from high-aluminium coal fly ash, coal gangue, andalusite-sericite phyllite and oil shale slag through the hydrothermal crystallization process after the removal of the residual carbon, deferrization or calcination. The phase constitution and microstructure of the synthesized mullite nanocomposites powders were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and energy-dispersive X-ray (EDX). Moreover, the reaction mechanism was analyzed according to MAS-NMR results. The experimental results show that mullite nanocomposites powders can be prepared from any silicon-aluminium-bearing minerals at 80～90℃ for 3 h with NaOH concentration of 2～4 mol/L and L/S ratio (liquid/solid ratio in mass) of 10 mL/g. Mullite nanocomposites which are synthesized from coal gangue, andalusite-sericite phyllite and oil shale slag are mainly existent as whole puncheon-shaped crystals, whose average lengths are 50 nm, 300 nm and 150 nm, and whose average aspect ratios are 4, 3.5 and 3.75, respectively. Otherwise, when coal fly ash is used as the raw material, mullite nanocomposites are mainly rod-like, acicular and fibroid in shape with the length in the range of 30～80 nm and the diameter in the range of 4.5～30 nm. MAS-NMR analysis indicates that the nano-size mullite grows around the central atoms Al, Si of the [AlSi]O₄ tetrahedron and the growth unit Al[OH]₄^- is existent in this process definitely.

Abstract:In this study, the removal of Cd²⁺ from aqueous solutions by desulfurization products of manganese nodule leached residue was carried out in consideration of the influence of various parameters, such as contact time, solution pH and initial metal concentration, and adsorbent quantity. X-ray diffraction (XRD), scanning electron microscopy(SEM)and X-ray photoelectron spectroscopy(XPS)were used to characterize the materials and products. The adsorption of Cd²⁺ increased with the increase of the adsorbent in solution, and the reduction of the particle size also increased the removal efficiency. The removal of Cd from aqueous solution by desulfurization products of manganese nodule leached residue was based on the ion exchange reaction principle MnS+Cd²⁺→CdS+Mn²⁺.

Abstract:As one of the common manganese oxide minerals in the supergene environment, birnessite affects the migration, transformation and environmental fate of sulfur in soil. In this study, the oxidation process of sodium sulfide by birnessite was investigated. The kinds and concentrations of oxidation products of sulfides in solution were determined by spectrophotometry and ion chromatography, and the crystal structures and micro-morphologies of solid oxidation products of sulfides were analyzed by XRD and SEM. The influence of temperature, pH value of solution and the amount of added birnessite on the oxidation rate of S^2- was studied. It is observed that the main oxidation product of sulfides is elementary substance S, and the S^2- oxidation rate follows a pseudo-first-order reaction. Oxidation rate increases with elevating reaction temperature, decreasing pH value of solution and the increase of the amount of added minerals. During the redox process, birnessite is reduced to Mn(OH)₂, which can be oxidized into Mn₃O₄ by O₂ in air, and Mn₃O₄ is further transformed into MnOOH.

Abstract:Calcifications in the calcified focuses from inflammation and hyperplasia of breast patients were investigated in terms of their composition, structure and morphology by using light microscope (OM), environmental scanning electron microscope (ESEM) and micro area X-ray diffraction (BL15U), and the formation mechanism of the calcifications was discussed. The results show that the calcifications in inflammation focus mainly result from dead adipocytes and repairing collagen of type Ⅲ which occurs at the late stage of the disease. Dilating catheter calcifications in hyperplasia of breast come from collagen of type Ⅳ. At the early stage of thanatosis calcification of hyperplasia, many nano-sized calcified balls are precipitated on the collagen fibers of type Ⅳ due to the adsorption of inorganic ions such as calcium ions onto glucose amino glycan. These balls continue to grow and aggregate, and gradually act as the calcification of the collagen fibers during the development of the disease, which finally turns out to be a large area. The main component of calcifications of both inflammation and hyperplasia of breast is poorly-crystallized carbonate-rich hydroxylapatite.

Abstract:Based on experiments of interactions between Acidithiobacillus ferrooxidans (A. f) and sulfide ores, this paper studied the oxidation of different sulfide minerals in the same ore sample mediated by A. f, and analyzed the reacted mineral surfaces and secondary products. The purpose of this study is to disclose the selectivity of A. f mediated oxidation and the dissolution sequence of different sulfide minerals in the same ore sample. Analytical approaches, such as inductively coupled plasma optical emission spectrometer (ICP-OES), scanning electron microscope_energy dispersive spectrometer (SEM-EDS) and X-ray diffraction (XRD), were employed to investigate changes in the concentrations of specific metal ions in the solution, surface morphology of the original minerals and precipitations during the experimental period. The results indicate remarkable difference between the interaction effects of A. f on different sulfides. The effects on both galena and sphalerite are very evident, while those on pyrite are rarely observed. It is concluded that galvanic reactions occur in the bacteria mediated oxidation of sulfide ore due to the contacts of different sulfides with various crystal structures in the ore samples. Pyrite grains, generally acting as the cathode, are protected, which exhibits a selective interaction of A. f with sulfide minerals in ores. The preferably oxidized sequence of these sulfides in an A. f-mediated ore sample is in order of sphalerite, galena and pyrite.

Abstract:Acid mine drainage (AMD), resulting from the oxidation of iron pyrite (FeS₂) and other sulfide minerals, is a major problem in coal-and metal-mining districts in that such water often has a lower pH and contains high concentrations of heavy metals as well as Fe and SO₄^2-. Preventing the formation or migration of AMD from its source is generally considered to be the preferable option. However, due to the practical operational difficulties in many locations, efforts are directed towards the collection and treatment of the effluent. There are various options available for AMD treatment, and lime neutralization seems to be the most widely-used method in the mining industry. Unlike Fe³⁺, Fe²⁺ is difficult to be precipitated unless pH is elevated to 8.5, thus, from the economic viewpoint, the oxidation of Fe²⁺ to Fe³⁺ prior to neutralization is required during the treatment of the Fe²⁺-rich AMD. Acidithiobacillus ferrooxidans was proved to be efficient for the oxidation of Fe²⁺ under low pH conditions. During the biological iron oxidation, abundant amounts of ferric iron oxyhydrosulfate (mainly jarosite) would precipitate. One of the advantages of the precipitate is the relative easiness of filtra-tion, thereby the problems associated with settling and filtering neutralized iron solutions are avoided. Therefore, the enhancement of the formation of ferric iron oxyhydrosulfate will favor the removal of soluble iron in AMD. Several factors affect the precipitation of ferric iron oxyhydrosulfate, such as temperature, initial pH, retention time, types and concentrations of jarosite-directing cations (K⁺, Na⁺, NH₄⁺, etc.) and the amounts of crystal seed.This paper reported the beneficial role of diatomite, quartz sand and K⁺ in iron oxyhydrosulfate formation in the presence of A. ferrooxidans. It was found that both the rate and extent of the formation of iron oxyhydrosulfate precipitate increased with the increase of the amount of the three materials added to the reaction system. Compared with the control without the addition of diatomite, quartz sand, or K⁺, the treatments with 10 g of diatomite, 10 g of quartz sand and 80 mmol/L of K⁺ increased the removal efficiency of total iron by 8%, 24%, and 20%, respectively, after 72 h of reaction in 160 mmol/L of the initial FeSO₄ biooxidation system. The contents of K and S of the jarosite produced in the K⁺ series increased with the increase of the initial concentration of K⁺ in the liquid media, whereas the content of Fe decreased.

Abstract:Schwertmannite has been proved to be a novel material which acts as a specific adsorbent for removing heavy metals or metalloid in contaminated water. Biogenic schwertmannite has received much attention in recent years due to its relatively strong adsorption capacity. In this study, the effect of initial Fe(Ⅱ) concentration on the formation of biogenic schwertmannite was investigated through the oxidation of FeSO₄ by Acidithiobacillus ferrooxidans. The results showed that the relationship between the initial Fe(Ⅱ) concentration (x, mmol/L) and the resulting mineral weight (y) could be expressed as y(g)=0.036 67+0.008 520x-8.602·10^-6x², or the relationship between initial Fe(Ⅱ) (x, mmol/L) and total iron removal efficiency (y) could be described by the equation y(%)=39.68-0.221 0x+ 6.653·10^-4x² when the concentration of Fe(Ⅱ) in the form of FeSO₄·7H₂O was 20～160 mmol/L, and the bacterial density was approximately 6.0×10⁷ cells/mL in 250 mL solutions. In the process of the reaction, lots of residual Fe³⁺ remained not precipitated although the saturation index is larger than 0. It is presumed that schwertmannite formation resulting from Fe³⁺ hydrolysis was probably caused by the energy obtained through the oxidation of Fe²⁺ by Acidithiobacillus ferrooxidans, which was supported by the fact that the generation of biogenic schwertmannite did not increase any longer after Fe²⁺ in solution was thoroughly oxidized by A. ferrooxidan, although a plenty of Fe³⁺ still existed in the reaction solution.

Abstract:Montmorillonite is a widely distributed clay mineral in the oil and gas basin. When it is encountered with water, its volume can expand by several or tens of times, which can be ascribed to the strong hydrophilic character. Consequently, oil and gas reservoirs might be damaged by its water-sensitive property. In this study, the phase transformation and hydrophilic behaviors of natural Na-smectite were investigated in alkaline solution. The natural smectite was put in solution of 0.1 M KOH, 0.5 M KOH and 1 M KOH at 80℃ for 30 days. The pH values of KOH solution after reaction were measured, and solid products were analyzed by X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), and electron dispersive analysis of X-rays (EDAX). The XRD results indicated that part of montmorillonite was transformed into chabazite and merlinoite after 30 days. The results showed that phase change of montmorillonite was related to the concentration of KOH and reaction temperature. Concomitantly, new crystals in plate-like, fibrous and granular forms were observed by SEM. Accom-panied by the phase transformation, the hydrophilicity and the free swelling volume of minerals were reduced.

Abstract:The MgO concentration in the magnesium-rich palygorskite is 16.23, which is almost twice its concentration in the magnesium-poor palygorskite, whereas the Fe₂O₃ concentration in magnesium-poor palygorskite is almost twice its concentration in magnesium-rich palygorskite. The thermal behaviors vary with the chemical composition of the palygorskite. The results of phase analysis, which was carried out with the purified samples which had been heated and kept at a certain temperature for 2h, show that magnesium-poor palygorskite experienced water depletion and glassy phase. The crystal structure was complete below 300℃, began to folding when the temperature reached 350℃, and was completely destroyed and formed glassy phase above 400℃. Magnesium-rich palygorskite expererienced water depletion, glassy phase and new crystalline phase (enstatite). The crystal structure was complete below 300℃, began to folding when the temperature rose from 350℃ to 500℃, and formed glassy phase from 600℃ to 950℃; enstatite began to form above 950℃. The temperatures for preserving thermal stability of magnesium-rich palygorskite and magnesium-poor palygorskite were about 600℃ and 400℃ respectively. The results of differential thermal analysis and XRD show the same regularity: the magnesium-rich palygorskite has better thermal stability than magnesium-poor palygorskite, which is probably attributed to the different ionic bonds. Mg (Ⅱ) and Fe (Ⅱ, Ⅲ) are the main coordination ions in the palygorskite and can form ionic bonds with the crystal water. Different bond energies in different bonds have an effect on the crystal structures of palygorskite. The content of Mg is low but the content of Fe is high in magnesium -deficient palygorskite, whereas things are just opposite for magnesium-rich palygorskite. With the same anions, the smaller the metal ion, the higher the lattice energy in the formed ionic bond. The ionic radius of Mg (Ⅱ) is between the radii of Fe (Ⅱ) and Fe (Ⅲ). So the lattice energy of the ionic bond formed by Mg (Ⅱ) and crystal water is between the lattice energy of the ionic bond formed by Fe (Ⅱ) and that formed by Fe (Ⅲ). With the combined action of Mg (Ⅱ), Fe (Ⅱ) and Fe (Ⅲ), the magnesium-rich palygorskite is destroyed above 500℃ while magnesium-deficient palygorskite is destroyed at 350℃.

Abstract:In this paper, the preparation technology of palygorskite-based compound material with palygorskite, starch, soluble glass was investigated, and the role of the compound material in the treatment of nitrophenol wastewater was studied. In addition, the effects of reaction time, addition amount of enzyme, H₂O₂ concentration and nitrophenol concentration on the removal of nitrophenol in wastewater by immobilized HRP was analyzed. The results showed that the optimal preparation conditions of palygorskite-based compound material were soluble glass 12%, starch 20%, calcination temperature 550℃ and calcination time 2 h. What is more important, the nitrophenol removal rate with immobilized HRP was higher than the original HRP. The optimal reaction conditions of removal of nitrophenol by immobilized HRP were reaction time 1.5 h, HRP 150 U, H₂O₂ concentration 0.12%, and nitrophenol concentration 100 mg/L. The nitrophenol removal rate was still above 60% when immobilized HRP was used for 7 times.

Abstract:The sorption behaviors of nitrobenzene (NB) onto the soft K⁺ cation modified montmorillonite (K-Mt) under the conditions of adding of K⁺ ion and varying reaction temperatures were investigated in this paper. The sorption kinetic experiments showed that the sorption equilibrium of NB could be reached within 8 h. A comparative analysis of the Henry and Freundlich equations was made to evaluate the sorption isotherms of NB onto the K-Mt, and some thermodynamic experiments were conducted to explore the sorption mechanism. The results show that soft cation of K⁺ can strengthen the sorption of K-Mt for NB. The adsorption isotherms of NB by the K-Mt can be fitted well with Henry and Freundlich equation (R₂>0.96). Moreover, the research results of thermodynamic sorption experiments demonstrate that the sorption of NB onto the K-Mt is a spontaneous exothermic process mainly controlled by both the hydrophobic bonding and n-π electron-donor-acceptor (EDA) interaction between clay mineral surface and nitrobenzene. The presence of K⁺ ion is likely to be a favorable factor due to increasing some sorption sites and improving the accessing condition for sorption, leading to the promotion of sorption for NB onto the K-Mt.

Abstract:The surface adsorption capability of Xianrenwan halloysite from Chenxi in Hunan Province was studied through the nitrogen adsorption-desorption experiment at 77.35 K by using such means as surface potential measurement and transmission electron microscope (TEM). The morphology of halloysite is hollow tubule. The isotherm of nitrogen of the adsorbs-desorption for halloysite is typeⅡisotherm. The pore dimension distribution of halloysite by BJH equation is 2.5～200 nm, and is concentrated in the range of 3～40 nm. The micro-pore dimension distribution of halloysite by HK equation is concentrated in the range of 0.6～1.9 nm. The azure halloysite has abundant pores, which are mainly meso-pores and micro-pores. The white hallosite has relatively less pores, being mainly micro-pores, meso-pores and macro-pores. The surface point of zero charge is close to the pH value of 2. Zeta potential tends to be stable at about-40 mV. The halloysite has large specific areas(35～87 m²/g)and abundant pores(16.20～30.12 nm)so that its capacity for gas adsorption and ion exchange is very strong. Priority should be given to the exploitation of the azure halloysite because it has best adsorption capability.

Abstract:Soil organic matter is the basis of soil fertility, and also controls the balance of CO₂ in the atmosphere and the environmental behavior and biological effectiveness of nutrients, heavy metals and persistent organic pollutants (POPs) in Earth's surface environment. Therefore, it is necessary to pay attention to the process of stability of organic matter. This paper dealt with the mineralogical mechanism of soil organic matter stability by studying the crimson soil profile in Conghua, Guangzhou City. The following processes were carried out: determination of the basic properties of the soil, including pH and mechanical components; determination of total organic matter content and stable organic matter content by potassium dichromate oxidation; determination of the mineral stable organic matter content by TOC analyzer; extraction of free iron oxide with dithionite-sodium citrate; extraction of amorphous iron oxide with ammonium oxalate buffer; determination of iron content by atomic absorption spectrophotometry; XRD semi-quantitative determination of the composition and content of clay minerals; and the correlation analysis between organic matter and mineral. The results indicate that the content of total organic matter, stable organic matter, mineral stable organic matter and recalcitrant organic matter is reduced with the increase of depth. Mineral stable organic matter is mainly existent in the middle layer of soil, while iron oxide minerals mostly occur in the upper soil. The content of kaolinite is dominant (58.7%～84%), the content of smectite is relatively high (8.5%～16.8%); besides, there exists much gibbsite. The content of smectite decreases with the increasing depth, whereas the content of kaolinite and gibbsite increases with the decreasing depth. The correlation between organic matter content and iron oxide mineral is much higher than that between clay mineral and gibbsite. Soil organic matter content and amorphous iron content are much better than the free iron content in the correlation. For instance, there is positive correlation between organic matter and amorphous iron (R²>0.9), there is positive correlation between organic matter and smectite (R²=0.6971),and there is negative correlation between organic matter and kaolinite, gibbsite . Obviously, the amorphous iron plays a vital role in the stabilization of soil organic matter; nevertheless, the specific surface area of amorphous iron will limit the capacity of the soil C sequestration, and the adsorption capacity will gradually become smaller until saturation. So we should pay more attention to the mineralogical mechanism of soil organic matter stability and influencing factors.

Abstract:After long period of interaction, the form of organic and inorganic minerals would change. Batch technique was used to make a comparative study of the sorption for trichloroethylene (TCE). The results showed that the organic and inorganic minerals were existent in the form of organo_mineral complexes. The K_d and K_oc of organic-mineral complexes changed more obviously than organic matters and inorganic minerals. The interaction between humic acid and simulated minerals affected the sorption of trichloroethylene. Based on an analysis of the conformation of the humic acid in the complexes, the authors formulated a model of organo-mineral to explain the results.

Abstract:The sorption of components of crude oil to soils affects their transport and transformation. In this study, batch experiments were carried out to investigate the sorption and competitive sorption of benzene and toluene to soils with different amounts of organic carbon. The results of single-solute solution experiments showed that the sorption of single compound to soils could be described by a linear sorption isotherm, and the sorption capacity was proportional to the soil organic carbon content. In bi-solute solution experiments, competitive sorption of solutes was observed, which caused a decrease of sorption capacity of target compound in comparison with single-solute cases. In addition to partition process, the competitive sorption results indicated that the specific sites probably played an important role in the sorption of organic compounds on the solid surface.

Abstract:The ammonium in the vadose zone has remarkable effect on the degree of groundwater contamination, especially in the vadose zone of a landfill with high concentration of ammonium. Thus laboratory experiments were conducted with the tested soils in the vadose zone of a landfill. This paper deals with the mechanism of ammonium adsorption, with emphasis placed on the process of the adsorption, the contribution of different fractions of soils to the adsorption and the forms of the ammonium in soils. Among these factors, different forms of ammonium adsorbed by the soils seemed to be essential. The following results were obtained by the isothermal adsorption experiment and other experiments: ① In the isothermal adsorption experiment, the ammonium adsorbed by the tested soils was fitted well with Langmuir adsorption isotherm and the adsorption maximum reached 435 mg/kg at the temperature of 298 K. The adsorption capacity of different fractions of soils was in decreasing order of raw soils>fine sands>medium sands. The amount of adsorption for the silty clay increased with the increasing influent ammonium concentration of the solution, so did the ratio of adsorption for the silty clay. It is thus held that the silty clay became the most important composition of the tested soils with the value of contribution ratio growing from 43% at 50 mg/L influent ammonium concentration in the solution to 70% at 400 mg/L NH₄⁺-N. ② The ammonium adsorbed on the tested soils comprised three forms i.e., soluble ammonium, exchangeable ammonium and fixed ammonium. The concentrations of the first two forms of ammonium were obtained by different kinds of extractants, distilled water and 1M KCl correspondingly, with the extraction conditions of solid to liquid ratio 1∶5, extraction temperature 25℃, vibrating rate 175 r/min and extraction time 1.5 h. As for the fixed ammonium, it was not determined by the Silva-Bremner method but calculated with the rest of ammonium adsorption excluding soluble ammonium and exchangeable ammonium. The results indicated that the amount of each form of ammonium increased with the increasing influent ammonium concentration in the solution and the maximum adsorption for the three forms of ammonium reached 112.3 mg/kg, 97.5 mg/kg and 214.0 mg/kg respectively. ③ On the basis of the amount of ammonium extracted by different extractants, the positions occupied by different forms of ammonium in the clay were also different. The diffusion layer on the surface of the clay was firstly occupied by the ammonium mostly made up of soluble ammonium, then the adsorbed layer was occupied by the exchangeable ammonium and at last the inner of the crystal lattice and the interlayer of the mineral were occupied by fixed ammonium. These findings show that the risk of groundwater contamination caused by different forms of ammonium would be different correspondingly. The soluble ammonium would be very prone to filter down to the aquifer and cause the groundwater contamination. The exchangeable ammonium might remain in the aeration zone to some extent and causes less risk of groundwater contamination compared with the soluble ammonium. It is therefore critical to remove the ammonium in the vadose zone of landfills, otherwise the soluble ammonium would filter down to the aquifer with rainfall and leachate. The fixed ammonium is not the major source of groundwater contamination, because it is difficult for this kind of ammonium to filter down to the aquifer.

Abstract:In this experiment, the authors simplified the complexities and heterogeneities of the soil environment in order to study the impact of soil organic matters and minerals on the TCE sorption behaviors in homogeneous soils. The given minerals, which were mixed kaolin clay and silica sand according to the proportion of 3∶7 and served as the soil matrix structure, were added to different amounts of humic substance(f_oc=0.16%～2.29%)to comprise the model soils. The parallel experiments of the TCE sorption were carried out both in minerals and model soils respectively by using the batch experimental method. It is concluded that the sorption of the TCE was characterized by nonlinear isotherm. The linear sorption reaction was enhanced and the contribution rate of the minerals to the sorption was reduced with the increasing amount of the organic matters. The sorption contribution rate of minerals was less than 5% when the organic carbon content was more than 0.82%, and even could be neglected when the organic carbon content was higher than 1%. Also the original concentration of the TCE could affect the capacity of the sorption and the sorption contribution of the organic carbon and minerals in some way. The Freundlich sorption model was used to simulate the TCE isotherm sorption patterns in two segments, with C_e=500 μg/L as the boundary. The fitting exponential of Freundlich (n) decreased with the increasing TCE concentration. Besides, the contribution rate of the organic carbon increased while that of the minerals went down with the increasingly higher TCE concentration. When the TCE concentration varied from 50 to 500 μg/L and f_oc was 0.16%, the sorption contribution rate of minerals fluctuated in the range of 28%～16% and decreased to 3%～1% at f_oc equal to 1%, whereas the TCE concentration almost had nothing to do with their contributions.

Abstract:This paper reports some results of multi-purpose geochemical mapping in Qinghai Province. Soil heavy metal anomalies of such elements as Cd, Pb, Hg and Cr were detected in the narrow valley of Minhe and Haishiwan, along Road 109. The heavy metal anomalies exhibit features of relatively large anomalous area and high thresholds of anomalous elements. The results of correlation analysis show that Cr is significantly associated with soil constant components and negatively related to SiO₂. Cr is slightly concentrated in the top layer of soil in vertical section while urban areas have considerably higher level of Cr along the horizontal section. Cd is evidently associated with organic carbon, but there exists no such obvious correlation between Cd and TFe₂O₃. Beyond the soil depth of 80 cm, the content of Pb in the anomalous area is obviously higher than that in other areas. Pb anomaly basically exists at the surface of the soil. Hg is obviously concentrated at the surface of soil, while in the urban area it exists at the higher level. The results indicate that anthropogenic input is the main factor responsible for the formation of anomalies of Cd, Pb and Hg. The anthropogenic input increases the content of Cr in the high natural background. Therefore, we must control and manage the industrial "three wastes" in the anomalous area to prevent the expansion of the soil heavy metal anomaly.

Abstract:Pyrite is one kind of metal sulfide minerals distributed very widely and in non_uniform form in nature. Once the environmental conditions are changed, pyrite is very prone to be oxidized. Furthermore, human activities would accelerate oxidation of pyrite, reduce the strength of rocks, and trigger a lot of engineering geological problems. If the metal ions such as calcium are present in the geological environment, it is very easy for them to combine with sulfate and form gypsum. When the sulfur in pyrite generates the same moles of gypsum, the mineral volume would increase by more than 5 times in this process, and this would cause damage to the construction project due to non-uniform distribution. Pyrite oxidation and decomposition form water-soluble minerals such as jarosite with the continuous reaction. These weathering minerals are dissolved and often form small cavities, resulting in the formation and transformation of the underground fluid and increasing damages to projects. Despite the fact that the damage of pyrite weathering to projects has aroused some attention, further studies are needed to investigate and interpret geological problems caused by weathering of pyrite on the basis of geochemical theories.

Abstract:In this paper, palygorskite/alumina composite materials were prepared as the adsorbent by using sol-gel technique, and the adsorption properties and mechanisms of complex adsorbing phosphate were investigated, with a discussion on the adsorption kinetics and thermodynamic characteristics. The results demonstrate that the adsorption processes of phosphate on complex surface follow the pseudo-second-order equation most effectively and the rate constant increases with decreasing initial concentration and the rise of temperature. The adsorption isotherms fit Langmuir equation and D-R equation fairly well. The adsorption enthalpy is positive and the adsorption Gibbs free energy changes are in the range of-25～-21 kJ/mol. The adsorption process is endothermic and spontaneous, with the coexistence of physical adsorption and chemical adsorption.