基于电感耦合等离子技术测定高纯氧化镁产品中酸溶硅含量

高纯氧化镁产品纯度达到99.9%,杂质硅含量是评价高纯氧化镁产品等级的重要指标之一,对其进行准确测定显得尤为重要。常规的标准曲线法无法克服镁的基体效应,国内同行常规使用基体匹配法来克服基体效应,但是难以找到含杂元素与高纯氧化镁产品相近且纯度更高的金属镁。采用标准加入法作为技术手段,优点是非常适合高镁基体浓度中(超)痕量元素的分析,准确度高。本研究以盐酸溶解样品,以标准加入法为技术手段,采用电感耦合等离子体发射光谱技术,建立了一种简单、快速、准确的测定方法。该方法在分析谱线251.611 nm处,有良好的线性关系,方法的检出限为0.0183μg/mL,测定下限为0.0610μg/mL。在实际高纯氧化镁产品测试中,加标回收率在97.86%~103.80%之间,适合高纯氧化镁产品中酸溶硅的测定,为解决盐湖化工企业氧化镁产品中酸溶硅含量的测定提供了技术支撑。

ICP-OES测定钢铁及合金钢中酸溶硅

建立了电感耦合等离子体发射光谱法(ICP-OES)测定钢铁及合金中酸溶硅的分析方法。采用稀硫酸溶解钢铁及合金钢试样、低浓度的高锰酸钾溶液氧化难溶物和低温慢溶的方式使样品溶解更加完全,减少了多离子对仪器的干扰;通过基体匹配保证了标准溶液和样品介质的一致性。硅的方法检出限为0.03mg/L,该方法所用试剂少,减少了样品处理的复杂性,实现了钢铁及合金钢中硅的准确测定。

还原型硅钼酸盐光度法测定不锈钢中硅含量的试验研究

钢铁及合金中酸溶硅的含量测定，对应于国家标准GB223．5—2008（钢铁及合金化学分析方法还原型硅钼酸盐光度法测定酸溶硅含量》，本标准适用于铁、碳钢、低合金钢中0．030％（m／m）～1．00％（m／m）酸溶硅含量的测定，实验方法简单、快速、分析准确，广泛用于基本的化学成分分析试验，也被用做仲裁实验；本文参照此方法对不锈钢进行分析测定。材料研究所将国家标准GB223．5—2008（（钢铁及合金化学分析方法还原型硅钼酸盐光度法测定酸溶硅含量》的适用范围进行扩大，在此国家标准的基础上改进，形成一个应用范围更广的非标准实验方法，以便适应我公司目前的理化检验现状。

还原型钼蓝酸盐光度法测定钢铁及合金中酸溶Si含量的不确定度评估

对钼蓝光度法测定钢铁中Si含量的不确定度的产生原因进行分析,并分析了一个钢样中硅含量测定结果进行了不确定度的评定。

Effect of inorganic salt impurities on seeded precipitation of silica hydrate from sodium silicate solution

To clarify the precipitation of silica hydrate from the real desilication solutions of aluminosilicate solid wastes by adding seeds and improve integrated waste utilization,the seeded precipitation was studied using synthesized sodium silicate solution containing different inorganic salt impurities.The results show that sodium chloride,sodium sulfate,sodium carbonate,or calcium chloride can change the siloxy group structure.The number of high-polymeric siloxy groups decreases with increasing sodium chloride or sodium sulfate concentration,which is detrimental to seeded precipitation.Calcium chloride favors the polymerization of silicate ions,and even the chain groups precipitate with the precipitation of high-polymeric sheet and cage-like siloxy groups.The introduced sodium cations in sodium carbonate render a more open network structure of high-polymeric siloxy groups,although the carbonate ions favor the polymerization of siloxy groups.No matter how the four impurities affect the siloxy group structure,the precipitates are always amorphous opal-A silica hydrate.

Adsorption of sodium polyacrylate at interface of dicalcium silicate-sodium aluminate solution

The adsorption isotherm of sodium polyacrylate on dicalcium silicate（2CaO-SiO2） in sodium aluminate solution at 80 ℃ was studied.The type of surface adsorption of sodium polyacrylate is saturated adsorption,and the adsorption behavior belongs to L-type,according with the monolayer adsorption model of Langmuir equation.The surface coverage of sodium polyacrylate is 1.06 mol/μm2.The relation curve between the surface pressure and the molecular area of adsorption film was obtained by Gibbs formula.The variation of interfacial energy caused by adsorption as well as the relationship between the relation curve and the type of adsorption was discussed.

Solubility of hemimorphite in ammonium sulfate solution at 25 °C

The solubility of natural hemimorphite in ammonium sulfate solution was measured by isothermal solution method at 25 °C and the dissolved residue of hemimorphite was investigated by X-ray powder diffraction （XRD）, scanning electron microscopy （SEM） and Fourier transform infrared spectroscopy （FTIR） methods. The results show that zinc and silica in hemimorphite simultaneously dissolve in ammonium sulfate solution. The solubility of zinc in solution increases rapidly from 4.5381 mmol/kg in 0.5469 mol/kg ammonium sulfate solution to 11.5083 mmol/kg in 3.7038 mol/kg ammonium sulfate solution. The solubility of silica in solution increases slowly from 2.5509 mmol/kg in 0.5469 mol/kg ammonium sulfate solution to 7.2891 mmol/kg in 3.7038 mol/kg ammonium sulfate solution. The dissolved residue is the characteristic of hemimorphite Zn4Si2O7（OH）2·H2O based on the results of the XRD, SEM and FTIR. Thus, no phase transition occurs in the dissolution process of hemimorphite in ammonium sulfate solution.

Variation of soda content in fine alumina trihydrate by seeded precipitation

High soda content in fine alumina trihydrate（ATH） limits its application and increases the soda consumption. The variation of soda content in the fine ATH by seeded precipitation was determined by detection of electric conductivity of solution, soda content in ATH, measurement of particle size distribution and microscopic analysis. The results show that high concentration of sodium aluminate solution, ground circulative seed, low temperature or fast initial precipitation rate increases the soda content in ATH. Soda mainly exists in lattice soda and less soda in desilication product （DSP） exists in the fine ATH precipitated from sodium aluminate solution with concentration of Al2O3 （ρAl2O3） more than 160 g/L and mass ratio of alumina to silica （μSiO2） of 400, and lattice soda decreases with increasing initial precipitation temperature, aging seed, and low precipitation rate and precipitation time. Results also imply that -＋ 4）Na Al（OH ion-pair influences lattice soda content in ATH on the basis of electric conductivity variation.

Influence of silicate anions structure on desilication in silicate-bearing sodium aluminate solution

The structural changes of silicate anions in the desilication process with the addition of calcium hydrate alumino-carbonate were studied by measuring Raman spectra, infrared spectra and corresponding second derivative spectra. The results show that the desilication ratio in the solution prepared by the addition of sodium silicate(solution-SS) is much greater than that in the solution by the addition of green liquor(solution-GL), and low alumina concentration in the sodium aluminate solutions facilitates the desilication process. It is also shown that alumino-silicate anions in the solution-GL, and Q^3 polymeric silicate anions in solution-SS are predominant, respectively. In addition, increasing the concentration of silica favors respectively the formation of the alumino-silicate or the Q^3 silicate anions in the solution-GL or the solution-SS. Therefore, it can be inferred that the low desilication ratio in the silicate-bearing aluminate solution is mainly attributed to the existence of alumino-silicate anions.

Mineral transition of desilication products precipitated in synthetic sodium aluminate solution under atmospheric pressure

The liquor concentration, mineral proportion, crystal parameters and micro morphology of various desilication products（DSPs） precipitated in silica-supersaturated sodium aluminate solution at 95 ℃ under different reaction conditions were systematically researched. The DSPs formed under atmospheric pressure comprise amorphous phase, zeolite A, zeolite and sodalite, and the DSPs concentration and crystallinity increase with the increase of initial silica concentration, initial molar ratio of caustic Na2O to Al2O3（αK） and desilication duration. Decreasing the initial silica concentration, initial αK and increasing the desilication duration can reduce the proportion of zeolite A. The zeolite and sodalite are the stable DSPs, while the precipitation of zeolite A occurs at a high silica-supersaturated state in sodium aluminate solution. The DSPs are precipitated in the form of agglomerates, but the morphologies of various DSPs are quite different. Both the molar ratios of Na2O to Al2O3 and SiO-2 to Al2O3 in DSPs increase with the increasing desilication duration, resulting in the increase of the cell volumes of various DSPs. The precipitation sequence of DSPs under atmospheric pressure is： amorphous phase→zeolite A→zeolite→sodalite.

Properties of low-modulus sodium silicate solution in alkali system

The properties of low-modulus(m≤1)sodium silicate and pre-desilication solutions in alkali systems were studied by measuring their electrical conductivity,viscosity,and surface tension.The results show that the property of high concentration pre-desilication solution is similar to that of sodium silicate solution.The electrical conductivity of sodium silicate solution increases with increasing the temperature and silica concentration but decreases with increasing the modulus.Further,the viscosity of the solution increases with increasing the silica concentration and linearly decreases with increasing the temperature,whereas its surface tension gradually decreases with increasing silica concentration and temperature,indicating that the sodium silicate solution is an oligomer with strong surface activity.At room temperature,the electrical conductivity and surface tension of sodium silicate solution are higher than those of pre-desilication solution,whereas its viscosity is smaller than that of pre-desilication solution.A turning point exists at a silica concentration of 44.7 g/L.When the silica concentration is less than 44.7 g/L,the ionic structure of the solution is dominated by monomeric silicate ions.In contrast,when the silica concentration changes from 44.7 to 50 g/L,the migration number of silicate anions significantly decreases.

Feasibility of Using Trichloroacetic Acid Soluble Siliconas a Diagnostic Index of Silicon Deficiency in Rice

Pot experiments and field trials were conducted to investigate the changes in trichloroacetic acid (TCA) soluble silicon (Si) in the leaves of rice (Oryza sativa L.) and to examine the feasibility of using TCA-soluble Si content as an index for diagnosing Si deficiency. The TCA-soluble Si content was significantly higher in the leaves of both Si-treated and -untreated rice at the elongation stage compared with that at tillering stage. It was also higher in the Si-treated plants than in the controls throughout the whole growth period.However, whether dressed at elongation or booting stage, silicon fertilizer resulted in a significant increase in TCA-soluble Si one week to ten days after application. The same was true for the total Si accumulation in the plants. A close positive correlation was found between TCA-soluble Si and total it in plants grown on pot soils (r=0.669, P<0.01, n=26). The results obtained in the field trials revealed that the available Si extracted by sodium acetate (pH 4.0) could not predict the response of rice to added Si in the calcareous soils satisfactorily. No significant correlation was found between soil available Si content and rice yield, but TCA-soluble Si in the leaf blades of rice was significantly correlated both with rice yield (r=0.57, P<0.01,n=30) and with total plant Si (r=0.89, P<0.01, n=30). It is recommended that, with 95 per cent confidence,the critical value of TCA-soluble Si in the leaves of rice should be 52-57 mg Si kg-1, above which no positive response of rice to added Si would be expected.

Effects of Colloidal Silica Binder on Catalytic Activity and Adhesion of HZSM-5 Coatings for Structured Reactors

HZSM-5 coating using three colloidal silica binders, acidic colloidal silica （ACS）, neutral colloidal silica （NCS） and basic colloidal silica （BCS）, was prepared to study the effect of hinders on their adhesion and catalytic activity. Scanning electron microscopy characterization indicated that the zeolite coating using BCS shows the smoothest surface with higher homogeneity and adherence strength. The specific surface area, relative crystallization and acid site strength of zeolites are also dependent on the binder used. Catalytic cracking of supercritical n- dodecane over the series of zeolite coating with various binders indicated that HZSM-5 coating with BCS exhibits the highest and the most stable catalytic activity compared with other kinds of binders, and also exhibits a stable catalytic activity ascribed to its proper acid property and microstructure.

Distributions of Inorganic Nutrients in the Bohai Sea of China

To study the contents and distribution of inorganic nutrients in the Bohai Sea of China, two cruise surveys were undertaken in August (summer) 2000 and January (winter) 2001, respectively. A total of 595 water samples were collected from 91 stations and five nutrients, i.e., nitrate, nitrite, ammonia, phosphate and silicate, were analyzed for each sample. The results show that the average concentration of dissolved inorganic nitrogen (DIN) in the Bohai Sea in winter (6.529 μmol L -1) is significantly higher than that in summer (3.717 μmol L -1). The phosphorus concentration in winter (0.660 μmol L -1) is also significantly higher than that in summer (0.329 μmol L -1). Mean silicate concentration in winter (7.858 μmol L -1) is, however, not significantly different from that in summer (7.200 μmol L -1). Nutrients also vary considerably in different areas in Bohai Sea. DIN concentration in the Laizhou Bay (4.444 μmol L -1), for example, is significantly higher than those in the Bohai Bay (2.270 μmol L -1) and Bohai Strait (2.431 μmol L -1), which is caused by the discharge of large amounts of nitrogen into Laizhou Bay via Yellow River. The nutrients show different vertical distribution patterns. In summer, nutrients in bottom layer are generally richer than those in surface and middle layers. In winter, however, nutrients are not significantly different in different layers. Compared with historic data, DIN contents have increased continually since the early 1980 s. Based on atomic ratios of different nutrients, nitrogen is still the limiting factor for algal growth in the Bohai Sea.

Thermodynamic analysis on reaction behaviors of silicates in (NH_4)_2WO_4-(NH_4)_2CO_3-NH_3-H_2O system

The reaction behaviors of silicate species in （NH4）2WO4-（NH4）2CO3-NH3-H2O system are crucial to developing a greenmanufacture technique for ammonium paratungstate. In order to efficiently remove silicon from the system, the reaction behaviors ofsilicate species were systematically investigated by thermodynamic analysis. The thermodynamic analysis shows that silicate in thetungstate clinker partly decomposes in the leaching process, with 150-160 mg/L silicon thermodynamically at 25 ℃. The dissolvedsilicon can be removed by magnesium salts via forming insoluble MgSiO3. The low carbonate and high ammonia concentrations inthe system are beneficial to the removal of silicon, with silicon concentration reaching 8-10 mg/L thermodynamically, whereasMgSiO3 precipitation is hardly formed when the concentration of total carbonate is more than 1.5 mol/L. The reaction behaviors ofcalcium and magnesium were also studied in the system. The results in the verification experiments consist with the theoreticalcalculation.

Cleaning the Ion Exchange Resin Sorption of Uranium from Silicic Acid Solution ＂Ayanat＂

The authors discovered a new way to clean the ion exchange resin sorption of uranium from silicic acid used solution ＂Ayanat＂. The method reduces the costs of regeneration of ion exchange resin and its reuse in the sorption of uranium.

Preparation and Characterization of Hybrid Aqueous Dispersions Composed of Silica Sol and Poly(styrene-co-acrylate)

A stable silica sol with 3-5 nm in diameter, which can form homogeneous film without crack, was prepared and characterized. Then, the inorganic-organic hybrid aqueous dispersion composed of such a silica sol and an emulsion of styrene （St） and acrylate （Ac） copolymer was prepared and the hybrid effect between the silica sol and poly（St-co-Ac） was observed by Fourier transform infra-red （FT-IR） spectroscope. The toughness of the film prepared by this kind of hybrid aqueous dispersion was excellent, as it was enhanced appreciably by commixing with a small amount of poly（St-co-Ac） emulsion. Some amino-polysiloxane modified hybrid aqueous dispersions were also prepared and the properties of the modified dispersions and their films were investigated. The experimental results showed that the film prepared with such an amino-polysiloxane modified hybrid dispersion exhibited excellent hydrophobicity and low surface energy after heat treatment for 1.5 h, during which the formation of the graft copolymer was observed. The surface energy of this film decreases as a result of the enrichment of siloxane segments on the film surface.

SOL-GEL SYNTHESIS AND LUMINESCENCE OF GREEN LIGHT EMITTING PHOSPHORS ZN_2SIO4/MN^(2+)

Mn^2＋ doped Zn2SiO4 phosphors were synthesized by sol-gel method, and the influence of zinc source, Mn^2＋ dopant concentration and annealing temperature were investigated. Results show that zinc nitrate based precursor with strong green emission intensities is better than zinc acetate based precursor. The intensity of green light emission reaches a peak at 254 nm when the Mn^2＋ dopant concentration is about 5%（ molar percentage）. Structural details of the phosphors were examined through X-ray diffractometry, thermogravimetric and differential thermal analysis. The result indicates that they are both rhombohedral structures, which remain amorphous below 700 ℃ and crystallize completely around 1000 ℃. The luminescent properties of Zn2SiO4/Mn^2＋ phosphors were characterized by excitation and emission spectra.

Effects of Characteristics of Fly Ash on the Properties of Geopolymer

The properties of two types of fly ash geopolymers made from class F fly ashes produced in wet bottom and dry bottom boilers were investigated in the present study. The source material used in the geopolymer concrete was activated with sodium hydroxide and sodium silicate solution. The results revealed that the geopolymer produced with wet bottom boiler fly ash(CZ-FA)hardened quickly, and had higher early-age strength and lower shrinkage than the geopolymer produced with dry bottom boiler fly ash(SX-FA). The compressive strength of the two geopolymers made from CZ-FA and SX-FA was 45 MPa and 15 MPa respectively when cured at 60 ℃ and delayed for 14 d. However, after 90 days' delay, the compressive strength of both the samples is almost the same, up to 80 MPa. Nearly 20% volume shrinkage of the samples made from SX-FA was much higher than that made from CZ-FA, which was almost zero. XRD, SEM/EDS and FT-IR were used to analyze the main reason of the differences.

Recovery of Gold from Aqueous Solution Containing Au（Ⅲ） by Silicon Organic Polymer

The silicon organic polymer containing PSOT-3 （dioxothiocarbamide groups） has been synthesized and characterized, and the adsorption of Au（III） on PSOT-3 was investigated. The results showed that PSOT-3 had good adsorption capacity for Au（III）, and the adsorption of Au（III） was found to be the most effective in 0.1-0.3 mol/dm^3 hydrochloric acid solution. The adsorption is physical and the process is endothermic, and Freundlich isotherm fits the data better than the Langmuir isotherm. The adsorption can be generally described by electrostatic interaction （Coulomb＇s force） between the adsorbent and the adsorbate. The high adsorption capacity of this sorbent has significant potential for gold recovery from aqueous solutions.