Technology of dehydration and transformation of silicic acid

The technology that silicic acid was pressurized under high temperature in order to dehydrate and transform was investigated in the paper. The effects, such as the ratio of liquid to solid, pressure, temperature, and reaction time on the dehydration rate and volume shrinkage rate, were researched. The experimental results show that the dehy- dration rate of silicic acid is up to 41.20 %, accompanying with the volume shrinkage rate of 40.37 % after silicic acid is pressurized under high temperature in the high-pressure kettle. The results of silicic acid tested by SEM indicate that the metasilicate acid molecules and water molecules are closely arranged, and there are almost no gaps before pressure reaction. There are many gaps accompanying with formatting lamellar structure after pressure reaction. The experimental results indicate the effect that silicic acid is dehydrated and transformation is obvious under high temperature and pressure.

Double Acid-Base Extraction of Silicic Acid from Quartz Sand

Silica is becoming more attractive as plant nutrient for non-graminae crops particularly in relation with drought-stress tolerant. Many efforts have been conducted to obtain an efficient technique to produce silica fertilizer worldwide, but the results are varying considerably due to various factors including raw material and extraction technique. This study was carried out to develop an efficient extraction technique for ortho-silicic acid (OSA-H4SiO4) from a Bangka-Belitung quartz sand by employing acid-base dissolution method. A 325-mesh size quartz sand was boiled in HCl solution at various concentrations. The optimum concentration was then used in the following experiment at several different volumes of solution. The sand obtained from optimum concentration and volume of HCl solution was then reacted with different amounts of NaOH (s), and heated until a wet mixture was obtained. As a reference the best extraction conditions were applied to a natural zeolite sample. All OSA analyses were done in triplicates with spectrophotometric method. Supporting evidences were collected from x-ray diffraction and scanning-electron-microscopy analyses of the treated samples. The yield of quartz sand-originated OSA was 183 g·kg-1 and significantly increased linearly with increasing weight of NaOH (R2 = 0.99**), whereas that from zeolite was only 104.2 g·kg-1 at 80 g NaOH. XRD and SEM data confirmed the evidences that the acid-base extraction disrupted the quartz mineral structure and as a consequence releasing more water soluble OSA.

Synthesis and Characterization of Modified Epoxy Resins by Silicic Acid Tetraethyl Ester and Nano-SiO_2

A kind of modified epoxy resins was obtained by condensation of epoxy resin with silicic acid tetraethyl ester（TEOS） and nano-SiO2. The reactions were performed with hydrochloric acid as a catalyst at 63 ℃. The structure, thermal stability and morphological characteristics of the modified epoxy resins were studied through infrared spectra（FT-IR） analysis, thermogravimetric（TG） analysis and scanning electron microscopy respectively. It has been found from the IR and TG study that modified epoxy resins have greater thermal stability than epoxy resins, and its thermal stability has been improved by the formation of inter-crosslinked network structure. The modified epoxy resins exhibit heterogeneous morphology and heterogeneity increases with more TEOS feeding, which in turn confirms the formation of inter-crosslinked network structure in modified epoxy resins.

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.

Effects of Temperature on the Deposition Rate of Supersaturated Silicic Acid on Ca-type Bentonite Tsuyoshi Sasagawa, Taiji Chida and Yuichi Niibori

Na-type bentonite is commonly used as a tunnel backfilling material to prevent groundwater and radionuclide migration during the construction of a geological disposal system for high-level radioactive waste in Japan. However, host rock fractures with strong water flow can develop groundwater paths in the backfilling material. Especially, the alteration to Ca-type bentonite causes degradation of the barrier performance and accelerates the development of groundwater paths. Additionally, using cementitious materials gradually changes pH between 13 and 8. High alkaline groundwater results in high solubility of silicic acid; therefore, silicic acid is eluted from the host rock. Downstream, in the low alkaline area, the groundwater becomes supersaturated in silicic acid. This acid is deposited on Ca-type bentonite, thus leading to the clogging of the groundwater paths. In the present study, we investigate the silicic acid deposition rate on Ca-type bentonite under 288-323 K for depths greater or equal to 500 m. The results indicate that temperature does not affect the silicic acid deposition rate up to 323 K. However, in this temperature range, the deposition of silicic acid on Ca-type bentonite in backfilled tunnels results in clogging of the flow paths.

Pressure leaching of zinc silicate ore in sulfuric acid medium

Zinc silicate ore was characterized mineralogically and the results showed that zinc exists mainly as hemimorphite and smithsonite in the sample.Sulfuric acid pressure leaching of zinc silicate ore was carried out to assess the effect of particle size,sulfuric acid concentration,pressure,reaction time and temperature on the extraction of zinc and the dissolution of silica.Under the optimum conditions employed,up to 99.25% of zinc extraction and 0.20% silica dissolution are obtained.The main minerals in leaching residue are quartz and small amounts of undissolved oxide minerals of iron,lead and aluminum are associated with quartz.

Determination of Iron in Layered Crystal Sodium Disilicate and Sodium Silicate by Flame Atomic Absorption Spectrometry with Boric Acid as a Matrix Modifier

The effects of matrix silicate and experimental conditions on the determination of iron in flame atomic absorption spectrometry （FAAS） were investigated. It was found that boric acid as a matrix modifier obviously eliminated silicate interference. Under the optimum operating conditions, the determination results of iron in layered crystal sodium disilicate and sodium silicate samples by FAAS were satisfactory. The linear range of calibration curve is 0-10.5 μg.mL^-1, the relative standard deviation of method is 1.2%-2.2%, the recovery of added iron is 96.0%- 101%, the sensitivity is 0.19 μg.mL^-l and the detection limit is 77 ng.mL^-1. The effect of the determination of iron of the standard curve method, standard addition calibration and colorimetry method was the same, but the first has the merits of rapid sample preparation, reduced contamination risks and fast analysis.

Highly dispersed metal incorporated hexagonal mesoporous silicates for catalytic cyclohexanone oxidation to adipic acid

Adipic acid is a dicarboxylic acid of great industrial importance,mainly used in the production of nylon-6,6 and polyurethane.The use of nitric acid as an oxidant in the industrial production of adipic acid poses significant carbon footprint to the environment.Clean adipic acid synthesis methods using a heterogeneous catalyst with H2O2 as oxidant and water as solvent have potential advantages of low catalyst cost,easy synthesis and recovery,cleanness and environmental protection.In this work,hexagonal mesoporous silicate materials were synthesized by a sol–gel method and evaluated for cyclohexanol/cyclohexanone oxidation to adipic acid.The physical and chemical properties of Fe-HMS were characterized by XRD,HR-TEM,BET and UV–Vis.The experimental results showed that Fe-HMS materials show pore sizes ranging from 2–3 nm.W-and Mo-based polyoxometalates were also evaluated and compared to the Fe-based HMS catalysts.To improve the adipic acid yield,the influence of the transition metal as well as the effect of metal loading,reaction temperature and catalyst amount on the catalytic performances of Fe-HMS have been investigated in details.When Si/Fe atomic ratio=100,Fe-HMS catalyst shows the highest activity,with a cyclohexanone conversion of 92.3%and adipic acid selectivity of 29.4%.The reaction pathway of cyclohexanone oxidation was further proposed based on experimental data.

Study of Rice Husk Ash as Potential Source of Acid Resistance Calcium Silicate

In present work acid resistant calcium silicate has been synthesized from silica of rice husk and calcium oxide of analytical grade. The silica from rice husk was extracted at 550oC in amorphous form and then allowed to react with calcium oxide in the presence of excess water by Sol-Gel technique to obtain calcium silicate hydrate gels. The molar ratios of Si/Ca were adjusted each time to obtain silica rich calcium silicate hydrates. The gels were dried in oven and calcined in muffle furnace at various temperatures to obtain acid resistant calcium silicate. The products were tested by analytical technique and by FTIR and XRD machines. Studies show that at higher molar ratio of Si/Ca, the heat treatment improves the acid resistivity of calcium silicate whereas at lower molar ratios the heat treatment does not make it acid resistant.

SERUM LIPID-BOUND SIALIC ACID IN LUNG CANCER PATIENTS

Serum lipid-bound sialic acid (LSA) assay was evaluated for differential diagnosis between benign and malignant pulmonary disease.Mean serum LSA for normal controls was 13.7±3.7 mg/dl and the upper limit of the normal value was set at 19.8 mg/dl (95% confidence limit,one side).The specificity was 97.l% (95% confidence interval was 93.8%, 100.0%).The mean for benign pulmonary disease was 1 7.l±5.l mg/dl,the specificity was 89.l% (95% confidence interval was 80.9%,97.3%), and the sensitivity was 10.9%.The mean for malignant pulmonary disease was 27.l±7.9 mg/dl, and the sensitivity was 93.3%(95% confidence interval was 88.5%, 98.1%).The serum LSA levels for different malignant pulmonary diseases were different between small cell carcinoma and adenocarcinoma. The results indicate that serum LSA assay might be used as tumor marker to differentiate lung cancer from normal subjects or benign lung disease.

CO_(2)驱硅酸凝胶封窜体系的制备与性能

开发易注入、可形成有效封堵的裂缝封窜技术,对于二氧化碳驱提高采收率技术具有重要意义。本文对硅酸乙酯进行改性提高其耐温性和不溶性,再乳化形成易注入的O/W乳液。考察了乳化剂类型和乳化剂用量对胶凝过程的影响。明确了pH值、温度和矿化度等因素对凝胶性能的影响,并通过人造岩心评价了该硅酸凝胶体系的封堵性能。结果表明,20%Span-80+80%Tween-80组成的复合乳化剂乳化效果最好,当乳化用量为1%时,乳化稳定性最好,粒径均一,易注入。当环境pH小于7时,可诱导乳液形成凝胶;随着温度的升高,成胶强度增强,但在150℃高温下,成胶强度下降。升高矿化度可加速凝胶的生成,但对凝胶强度影响较小。动力学分析表明,H+浓度是影响凝胶产生的关键因素,因此可在CO_(2)驱替酸性环境中,实现地层封堵。岩心实验结果显示,该凝胶颗粒可显著降低地层渗透率,封堵效果大于80%,可满足二氧化碳驱防气窜要求。

延迟成胶弹性硅酸凝胶堵水剂及其性能研究

针对现有硅酸凝胶堵水剂普遍存在成胶时间短、成胶后脆性大的问题,结合L油田油藏条件,通过考察活化剂类型及用量,弹性改善剂类型及用量,以及水玻璃用量对成胶时间和弹性模量的影响,得出了一种延迟成胶弹性硅酸凝胶堵水剂。其配方为:6%水玻璃+0.85%活化剂三元弱酸一铵GL-1+0.1%弹性改善剂正电胶,该配方在油藏温度65℃下,成胶强度达到E级的时间为72 h,成胶后的弹性模量为589.46 Pa。采用填砂管实验评价了堵水剂的注入性及封堵性,结果表明堵水剂在L油田中具有良好的注入性及封堵性,在渗透率为1168.06×10^(-3)~5061.57×10^(-3)μm^(2)的填砂管中,注入0.8 PV的最高注入压力仅有0.72 MPa,封堵率均>96%。该堵水剂可用于L油田的油井堵水。

碱硅酸反应-冻融循环下掺锂渣混凝土力学性能试验分析

研究了掺锂渣混凝土在碱硅酸反应(ASR)和冻融循环(FTC)耦合作用下的抗折和抗压强度。研究结果表明,碱硅酸反应和冻融循环均会降低混凝土的抗压抗折强度,掺入一定量锂渣的混凝土后进行碱硅酸反应会使混凝土的抗折强度略微提高。混凝土抗压强度随冻融循环次数的增多而降低,且两种反应互相耦合。前期碱硅酸反应会加剧后期冻融破坏的影响,先进行冻融破坏同样会加剧后期碱硅酸反应造成的影响。混凝土的力学性能随锂渣掺量的增加,呈现先变优后变劣的趋势,锂渣掺量为20%时对混凝土力学性能的提升最为显著。

石灰、磷酸盐及硅酸盐对土壤硒有效性及水稻累积硒的影响

华南地区酸性土壤硒有效性低,本研究旨在探讨石灰、磷酸盐及硅酸盐类土壤改良物质对酸性水稻土硒有效性及水稻吸收硒的影响。结果表明,在施0.25 mg/kg硒基础上,石灰、硅酸钠、磷酸氢二钠以及三者配合施用对水稻单株产量影响不大;对大米硒含量提升效果以石灰、硅酸钠及石灰、硅酸钠、磷酸氢二钠三者配合施用的处理较好;酸性土壤中各形态硒的含量高低依次为有机物/硫化物结合态硒、残渣态硒、铁锰氧化物结合态硒、交换态硒和水溶态硒。石灰、磷酸氢二钠处理显著提升易被植物吸收的水溶态硒及交换态硒含量,显著降低难利用残渣态硒含量;石灰、硅酸钠、磷酸氢二钠三者配合施用的处理显著降低了有机物/硫化物结合态硒的含量。施用石灰以及施用磷酸氢二钠均可有效提升土壤硒的有效性,并促进水稻对硒的吸收,施用硅酸盐对土壤硒有效性影响不大,但能促进水稻对硒的累积。

纳米硅溶胶的制备条件对粒径与稳定性的影响

硅溶胶是无固定形态的二氧化硅(mSiO_(2)·H_(2)O)颗粒在水中均匀分散形成的胶体。硅溶胶中二氧化硅颗粒表面含大量的羟基具有很强的活性。本实验以10%的硅酸钠为原料,通过离子交换法和母液增长法制备不同粒径的硅溶胶,考察了反应温度、反应时间、搅拌速度以及原料类型对硅溶胶粒径和分散性的影响。结果表明,制备较小粒径硅溶胶的最佳反应条件为:搅拌强度150 r/min、反应温度75℃、反应时间4 h,NaOH调节pH;制备较大粒径硅溶胶的最佳反应条件为:原料为搅拌强度150r/min、反应温度95℃、反应时间6h、用硅酸钠调pH;在该条件下,经过三次粒径增长,可制得最大粒径为11.69nm的硅溶胶产品,且稳定性与分散度较好,不易凝胶。

Recovery of scandium from silicate minerals by high-pressure leaching in sulfuric acid

This study investigated the leaching of scandium from a Sc-bearing silicate ore.The Sc concentrate obtained by beneficiation pre-enrichment has 1.03×10^(−4) wt%Sc and 14.66 wt%Fe.The main Sc-bearing minerals are limonite,chlorite,sericite,and hornblende,in the form of isomorphism.High-pressure leaching(HPL)with sulfuric acid(98 wt%)and NaF was used to dispose this samples.The Sc leaching efficiency of 91.82%was obtained under the optimum conditions,which are pressure of 5.0×10^(5) Pa,A/O value of 1.1,L/S value of 1.8,NaF dosage of 2 wt%,at 130℃ for 6 h.The X-ray diffraction(XRD)and scanning electron microscopy(SEM)results show that the residue is mainly quartz phase in the multihole shape.Compared with ordinary leaching for silicate,high-pressure leaching has significant advantages in saving acid and energy consumption.

石墨电极粉铺垫混合熔剂助熔测定窑渣中主要成分

本法尝试采用滤纸包裹试样,置于预先用石墨电极粉铺垫好的刚玉坩埚中,于900~950℃的高温炉中熔融10~20 min,至熔融物透明,盐酸浸取,过滤掉少量石墨粉,将滤液加热蒸发至干。在浓盐酸中加动物胶使硅酸凝聚沉淀,经过滤、洗涤、灼烧、称量,计算SiO_(2)的质量分数。所得滤液以氨水沉淀分离,滤液用EDTA标液滴定,计算CaO和MgO的质量分数。氢氧化物沉淀用盐酸溶解,再在氢氧化钠溶液中沉淀分离Al,分取滤液用氟代盐取代EDTA,用铜标液滴定,计算Al_(2)O_(3)的质量分数。

NaOH预处理橡胶颗粒对橡胶混凝土耐久性的影响

为了研究NaOH预处理的橡胶颗粒对橡胶混凝土耐久性的影响,以不含橡胶颗粒的砂浆和混凝土作为对照组,细骨料替代率为15%的未处理橡胶、细骨料替代率为15%和30%的NaOH预处理橡胶制备砂浆和混凝土试件。试验结果表明,混凝土的电阻率随着橡胶含量的增加而降低,NaOH预处理的橡胶混凝土吸水率最低;橡胶颗粒的掺入提高了混凝土的抗冻融性能;NaOH预处理的橡胶颗粒对混凝土的抗冻融性能影响更显著;橡胶颗粒的掺入降低了砂浆的膨胀率,掺入15%的预处理橡胶颗粒,砂浆的膨胀率最低。砂浆中橡胶颗粒含量越高,干燥收缩率越高。

某脉石英矿制备光伏玻璃用硅质原料工艺研究

随着光伏产业的高速发展,光伏玻璃需求量也大幅增加,但是优质的光伏玻璃原料供应不足。因此,有必要对硅质原料的提纯技术进行研究。本试验以福建某地脉石英矿为原料,对其进行工艺矿物学研究,采用“磨矿分级-自磨擦洗-磁选-酸擦”工艺流程,对磨矿细度、自磨细度、磁感应强度、酸擦酸种类、酸擦酸用量、酸擦时间进行条件试验。结果表明,该石英矿中主要的杂质矿物为绢(白)云母、高岭石和褐铁矿,通过磨矿分级、自磨擦洗等方法提纯后,在磁感应强度为1.0 T、草酸用量为7.5%、酸擦时间为40 min、酸擦液固质量比为2∶1、酸擦温度为25℃的情况下,最终得到SiO_(2)含量(质量分数,下同)大于99.5%,杂质Fe_(2)O_(3)、Al_(2)O_(3)、TiO_(2)、Cr2O_(3)含量满足JC/T 2314-2015《光伏玻璃用硅质原料》一级品标准的石英精矿。

Explaining surface interactions for common associated gangues of rare earth minerals in response to the oxalic acid

In the flotation of rare earth minerals(REMs), oxalic acid is reportedly acting both as a depressant and p H modifier. Although results of testing have established the significance of oxalic acid in the flotation process, its specific role in either the recovery or selectivity of REMs over their common gangue minerals is not well understood. Pulp p H reduction trials with alternative acids have not shown the same effect on the REMs recovery or the depression of gangue phases. This work studies the effect of oxalic acid on the surface of common REMs gangue minerals(quartz and carbonates(dolomite and calcite)) in a series of conditioning tests. Gangue surface analyses by time of flight secondary ion mass spectroscopy(TOFSIMS) indicate that oxalic acid inhibits the transfer of secondary ions generated during the conditioning process from one mineral to another. In this regard, the oxalate anion acts to fix ions in solution through chelation, limiting their participation in surface adsorption.