反应时间对镁铝水滑石结构的影响

以NaAlO_2和MgCl_2·6H_2O为主要原料,Na_2CO_3和NaOH为沉淀剂和pH值调节剂,采用共沉淀法,在不同反应时间和反应温度下制备了镁铝水滑石,并利用X射线衍射(XRD)、热重分析(TG)、傅里叶红外光谱(FT-IR)和扫描电子显微镜(SEM)对镁铝水滑石进行表征。结果表明,制备的水滑石的衍射峰强且尖锐,对称性较高,具有良好的结晶度,反应时间增加使水滑石晶面的层间距增加,而且有利于水滑石的结晶与生长;反应时间增加,能延缓水滑石向金属氧化物转化的过程,提高水滑石的热稳定性,水滑石由片状结晶逐步向小尺寸晶型转变,且水滑石晶粒越来越规整;随着温度的升高,水滑石的晶粒结晶性更好但尺寸有增大趋势。     

不同水滑石对水体中砷(As5+)的吸附去除

采用共沉淀法制备了镁铝水滑石(Mg-Al LDHs)、镁铁水滑石(Mg-Fe LDHs)和镁锰水滑石(Mg-Mn LDHs)3种水滑石,利用X射线衍射(XRD)仪和傅里叶红外光谱(FTIR)仪表征了3种水滑石的基本性质,通过等温吸附试验和吸附动力学试验研究了不同水滑石材料对水体中砷(As⁵⁺)的去除性能。结果表明,3种水滑石对水中As⁵⁺的吸附过程均符合Langmuir吸附模型及准二级动力学模型,拟合结果显示,Mg-Fe LDHs对As⁵⁺的吸附量最大,为202.429 mg/g;Mg-Mn LDHs对As⁵⁺的吸附速率最快,为0.007 150 mg/(g·min)。通过吸附前后FTIR表征试验,结合水滑石特殊的结构性质,推断水滑石对As⁵⁺的吸附机理为砷酸根扩散至水滑石层状孔隙后,水滑石层板阳离子与砷酸根发生表面络合。     

金属离子对滑石浮选行为的影响及机理研究

滑石常存在于硫化矿中影响硫化矿浮选精矿的质量。为了解金属离子对滑石浮选行为的影响和作用机制,考察了Ca²⁺、Mg²⁺、Cu²⁺、Fe³⁺对滑石纯矿物浮选、滑石表面ζ电位及滑石与气泡之间诱导时间的影响。结果表明：Ca²⁺、Mg²⁺、Cu²⁺、Fe³⁺均可在滑石表面形成吸附;Ca²⁺对滑石可浮性影响不大;添加Mg²⁺后,当pH＞10时,滑石可浮性降低;添加Cu²⁺后,滑石在pH=4~10范围被抑制,并且在pH值为6左右时Cu²⁺对滑石抑制作用最强;Fe³⁺在pH=3~9的范围内能够抑制滑石,并且在pH值为7左右时对滑石抑制作用最强。溶液化学计算结果表明,溶液中的金属络合离子可以改变滑石的表面电位,而氢氧化物沉淀吸附在滑石表面会降低滑石的可浮性。静电作用能计算结果表明：当pH值低于氢氧化物的零电点时,金属离子形成的氢氧化物沉淀会特定地吸附于滑石表面,产生多相凝聚,导致滑石表面亲水性增强,可浮性降低;当pH值大于氢氧化物的零电点时,凝聚现象减弱,滑石表面疏水性增强,可浮性提高。试验结果对含滑石硫化矿中滑石的抑制和分离有一定的指导作用。     

铝灰渣为原料的水滑石合成及其吸附性能研究

铝灰渣为铝工业生产中伴生的危险固废物,其产量巨大且含有大量的铝资源,合理利用铝灰渣有非常重要的意义。以铝灰渣为原料合成锌铝水滑石,分别用氢氧化钠和盐酸提取得到铝灰渣的提取液,再使用热水法成功合成锌铝水滑石,并探究合成时间、合成温度,以及使用两种不同提取液对合成的锌铝水滑石结晶度的影响。结果表明：延长反应时间和提高反应温度有利于晶体的生长,但过高反应温度会破坏锌铝水滑石晶体而变为其他产物;使用碱提取液合成的锌铝水滑石,其结晶度较好;同时,探究了不同条件下合成的样品对F-的吸附量,当使用碱提取液合成的锌铝水滑石在合成时间为6 h、合成温度为130℃条件下,F-的吸附量最大为18.3 mg·g^-1;XRD和SEM结果显示,使用氢氧化钠提取液合成的锌铝水滑石的结晶度和晶粒尺寸均较好。     

钙镁离子对细粒赤铁矿絮凝行为的影响

为了了解Ca²⁺、Mg²⁺对细粒赤铁矿絮凝行为的影响,以巴西某细粒赤铁矿石为研究对象,分别考察了用Na_2CO_3和Na OH调节矿浆pH的情况下,Ca²⁺、Mg²⁺对细粒赤铁矿絮凝行为的影响。结果表明:矿浆中Ca²⁺、Mg²⁺均能促进细粒赤铁矿的絮凝,随着Ca²⁺、Mg²⁺浓度的增大,促进效果增强。pH调整剂为Na_2CO_3时,随着矿浆pH升高,未达硬水浓度的Ca²⁺对细粒赤铁矿絮凝行为的促进效果均增强,而Mg²⁺对细粒赤铁矿絮凝行为的促进作用先增强后减弱;pH调整剂为Na OH时,随着矿浆pH升高,Ca²⁺、Mg²⁺对细粒赤铁矿絮凝行为的促进作用逐渐增强。矿浆中添加Ca²⁺与添加Mg²⁺相比,同等水硬度下,Ca²⁺对细粒赤铁矿絮凝行为的促进作用优于Mg²⁺。相同试验条件下,使用Na OH作pH调整剂时的细粒赤铁矿絮凝效果强于使用Na_2CO_3作pH调整剂时。     

Mg2+对油酸钠捕收石英的活化机理研究

石英矿物中常伴生有Mg²⁺,为了解Mg²⁺对油酸钠浮选石英的影响,进行了石英纯矿物浮选试验,并采用Zeta电位测试、溶液化学计算和红外光谱分析方法对Mg²⁺活化石英的机理进行了研究。结果表明：①在没有Mg²⁺存在的情况下,油酸钠对石英没有捕收能力;当矿浆pH=10.5,Mg²⁺浓度为3.75×10^-4 mol/L,油酸钠浓度为6.25×10^-4 mol/L时,石英的浮选回收率可达92.40％。②Zeta电位分析表明,吸附在石英表面的Mg2+是油酸钠吸附的活性位点,因而Mg²⁺对油酸钠浮选石英有活化作用。③溶液化学分析表明,Mg²⁺活化石英的有效成分为MgOH⁺。④红外光谱分析表明,有Mg²⁺存在的情况下,油酸钠才能吸附到石英颗粒表面。     

Mg2+对油酸钠捕收石英的活化机理研究

石英矿物中常伴生有Mg²⁺，为了解Mg²⁺对油酸钠浮选石英的影响，进行了石英纯矿物浮选试验，并采用Zeta电位测试、溶液化学计算和红外光谱分析方法对Mg²⁺活化石英的机理进行了研究。结果表明：①在没有Mg²⁺存在的情况下，油酸钠对石英没有捕收能力；当矿浆pH=10.5，Mg²⁺浓度为3.75×10^-4 mol/L，油酸钠浓度为6.25×10^-4 mol/L时，石英的浮选回收率可达92.40％。②Zeta电位分析表明，吸附在石英表面的Mg2+是油酸钠吸附的活性位点，因而Mg²⁺对油酸钠浮选石英有活化作用。③溶液化学分析表明，Mg²⁺活化石英的有效成分为MgOH⁺。④红外光谱分析表明，有Mg²⁺存在的情况下，油酸钠才能吸附到石英颗粒表面。     

不同碱源对合成MgAl-LDHs的结构及除氯性能的影响

为了获得除氯性能较好的镁铝类水滑石,研究了碱源对合成镁铝类水滑石的结构及除氯性能的影响。采用水热合成法,分别以尿素和氢氧化钠为碱源,硝酸根金属盐溶液为前驱体合成了LDHs-A和LDHs-B,采用XRD、SEM、BET、FTIR测试分析了不同碱源对镁铝类水滑石微观形貌的影响,通过氯离子吸附试验比较了2种类水滑石的除氯性能及除氯机理。结果表明,LDHs-A和LDHs-B均具有类水滑石结构的XRD特征峰,呈片层状结构,晶粒尺寸分别为1 000～2 000 nm、200～400 nm,比表面积分别为40.804 m²/g、62.609 m²/g,饱和吸附量分别为45.41 mg/g和78.69 mg/g。LDHs-A为碳酸根插层镁铝类水滑石,LDHs-B为硝酸根插层镁铝类水滑石。LDHs-A符合准一级动力学模型和Langmuir吸附等温模型,除氯机理主要为单层物理吸附;LDHs-B符合准二级动力学模型和Langmuir吸附等温模型,除氯机理主要为单层化学吸附。     

聚丙烯/插层改性水滑石纳米复合材料结构与性能研究

采用离子交换法制备了十二烷基磺酸钠和衣康酸共同改性水滑石(LDHs2),FTIR、XRD分析表明,十二烷基磺酸钠和衣康酸能够同时进入水滑石片层之间,层间距有很大提高。利用改性水滑石,通过马来酸酐—苯乙烯共接枝改性聚丙烯相容剂的熔融共混和聚丙烯与水滑石溶液共混制备母粒,然后与聚丙烯分别熔融共混两种方法制备聚丙烯/水滑石纳米复合材料。TEM分析表明,马来酸酐—苯乙烯共接枝改性聚丙烯作相容剂可以使水滑石在聚丙烯基体中达到更好分散。DSC、XRD分析表明,水滑石、相容剂以及聚丙烯对聚丙烯晶型没有影响,但对其结晶速率、结晶度以及晶粒大小有所影响,复合材料中聚丙烯的起始结晶温度、结晶峰温度、结晶速率、结晶度均比纯聚丙烯高,晶粒粒径分布也更均匀。     

累托石对钾离子的吸附/解吸动力学研究

以KCl为钾源,研究了湖北钟祥累托石对钾离子的吸附和解吸动力学行为。结果表明：累托石对K⁺的吸附速度很快,吸附动力学过程符合ExpAssoc模型,吸附平衡时间约为30 min;累托石对K⁺的等温吸附过程符合Langmuir等温吸附模式,饱和吸附量为14.588 mg/g;pH=5的HCl溶液对K+的解吸量最小,Ca²⁺+Mg²⁺混合溶液对K⁺的解吸量随着Ca²⁺+Mg²⁺浓度的提高而提高,Elovich模型和指数模型（双常数模型）可较好地描述 K⁺的解吸过程;累托石是较好的钾元素缓释载体,环境中Ca²⁺+Mg²⁺浓度越低,缓释效果越好。     

Preparation of iron oxide nanoparticles by mechanical milling

Hematite powder (Fe₂O₃) was ground in a planetary mill and the milling time and mill rotational speed were varied at three levels. The ground products were then characterized, to investigate size reduction and the mechanochemical effect, by X-ray diffraction (XRD) line broadening, specific surface area (SSA) and particle size and morphology analysis. The line broadening technique was used to determine the degree of crystallinity, crystallite size and lattice strain. The milled hematite particles revealed particle sizes in the nanometer range with a specific surface area of 14.96 m²/g. All milled samples exhibited the mechanochemical effect, where the degree of crystallinity ranged from 9.37 to 49.8%. The minimum crystallite size obtained was 17.1 nm with a degree of crystallinity of 9.37% when hematite was ground at 600 rpm for 10 h.     

The effect of particle size on acid mine drainage generation: Kinetic column tests

The rate of acid mine drainage (AMD) generation is directly proportional to the surface area and so to the particle size distribution of acid-forming minerals exposed to oxidation. Materials in various particle sizes are subject to weathering processes at field condition; however, the particle size dependent oxidation rate has not been investigated for understanding entire geochemical behavior at a mining site. Therefore, a comprehensive research program was aimed to investigate the effect of particle size on pH variation and acid mine drainage generation using kinetic column tests, and then to find convenient methodologies for upscaling laboratory-based results to the field condition. For this purpose, ore samples collected from Murgul Damar open-pit mining were grinded in three different particle size distributions that are coarse (minus 22.5 mm), medium (minus 3.35 mm) and fine (minus 0.625 mm) sizes, 34 columns were designed in different dimensions for kinetic column tests. It was found that the cumulative concentration of the many constituents measured from medium particles (minus 3.35 mm) are higher than coarser samples due to decreasing specific surface area with increasing particle size. Similarly, because of decreasing of hydraulic conductivity with increasing the fine content, the cumulative concentration of constituents measured from medium particles (minus 3.35 mm) are also higher than finer particles (minus 0.625 mm). Based on statistical and analytical analyses of the results of kinetic column tests, the time required to initiate acid formation at field condition varied between 489 and 1002 days depending on particle size distribution. In addition, considering the effect of particle size and the results of related statistical analysis, main oxidation (SO₄²⁻) and neutralization (Ca²⁺, Mg²⁺, Mn²⁺ etc.) products were also successfully upscaled to the field condition.     

Hydrotalcite Formation for Contaminant Removal from Ranger Mine Process Water

Process water from the Ranger Uranium Mine requires treatment to meet stringent environmental water quality criteria. The acidic water contains substantial SO₄, metals, and U. One novel treatment method under consideration is the use of Na-aluminate to both neutralise the process water and precipitate hydrotalcites. Hydrotalcites are a class of Mg–Al layered double hydroxide minerals with a typical endmember chemical composition: Mg₆Al₂(A)(OH)₁₆·n(H₂O), where A = CO₃ ²⁻, SO₄ ²⁻, etc. Many acidic wastewaters contain Mg and/or Al in sufficient abundance for hydrotalcite formation upon addition of alkali to achieve solution pH > 5, and Mg and/or Al to attain a Mg:Al ratio of 2 to 3:1. The utility of hydrotalcites lies in their ability to incorporate a range of cationic (Cu²⁺, UO₂ ²⁺), metalloid (AsO₄ ³⁻), and (oxy)anionic contaminants (CrO₄ ²⁻). The broad spectrum removal of contaminants, including U, also indicates that hydrotalcites and their derivatives could potentially be used as a containment material in nuclear waste repositories. In this study, Ranger process water derived from extraction of U from chloritic schist was treated with Na-aluminate sourced from Bayer process liquor, in combination with NaOH or Ca(OH)₂. Hydrotalcites formed as the primary mineral during process water neutralisation with the ability to simultaneously remove a suite of contaminants from solution.     

A new flowsheet for processing chromite fines by column flotation and the collector adsorption mechanism

Tailings produced from Üçköprü Chromite Concentrator are composed of fines mostly below 1 mm of which 52.3 wt. % is below 0.1 mm. A new flow sheet involving shaking table for processing −1 + 0.1 mm size fraction, and High Intensity Wet Magnetic Separator (HIWMS) and column flotation for treating -0.1 mm size fraction was put forward. According to the new ffowsheet, the Üçköprü Concentrator tailings assaying 13.99 wt. % Cr₂O₃ was upgraded to 47.4 percent Cr₂₃ at a recovery of 66.4 wt. % using shaking table followed by a combination of magnetic separation and column flotation with a mixture of anionic collectors at pH 11. The success of such high pH with anionic surfactants is indeed intriguing. Electrokinetic methods were used to elucidate the mechanism of collector adsorption and correlate the findings with the optimum flotation conditions. Multivalent constituent ions such as Cr³⁺, Al³⁺, Fe^e+ and Mg²⁺ were found to adsorb on chromite surface and shift the iep of chromite in the direction of oxide form of the mineral. The anionic collectors also imparted a negative charge to chromite in the entire pH region. The positive sites on the chromite surface, onto which anionic collectors adsorb, are generated through the formation of significant amounts of hydroxy complexes of magnesium ion at pH 11. Complementary infrared data reveals the absence of a shift in the spectra indicating the possibility of physical adsorption in the system.     

水滑石的合成及其在PVC中的应用研究进展

水滑石是一种层状双羟基复合金属氧化物,因其特殊的晶体化学性质,故有良好的热稳定性、吸附性和离子交换性,广泛应用于化工、材料、环保和医药等领域。本文重点介绍了水滑石的合成方法及其优缺点,水滑石在PVC中的应用进展,以及水滑石作为PVC热稳定剂的优异性能,并指出了今后的发展方向。     

离子液体[C16mim][NTf2]萃取H2SO4-NaClO3溶液体系中的Au(Ⅲ)

为了解咪唑型离子液体--1-十六烷基-3-甲基咪唑双三氟甲磺酰亚胺（［C16mim］［NTf₂］）-正戊醇体系对Au（Ⅲ）的萃取效果,研究了不同pH值、不同萃取剂浓度（［C16mim］［NTf₂］与正戊醇的质量体积比,g/L）、不同相比（离子液体相与浸金液相体积比VIL/Vaq,下同）对Au（Ⅲ）的萃取效果,并研究了［C16mim］［NTf₂］对Au（Ⅲ）的选择性萃取效果。结果表明：［C16mim］［NTf₂］对Au（Ⅲ）的萃取率随着pH值和相比的增大呈上升趋势;pH＜1.6时,Au（Ⅲ）的萃取率随萃取剂浓度的增加而增大;［C16mim］［NTf₂］对Au（Ⅲ）有明显的选择性萃取效果,在浸金液Au3+浓度为0.05 g/L,相比为1∶3,浸金液pH=1.6～2.0,［C16mim］［NTf₂］浓度为5 g/L,常温萃取时间为2 min情况下,Au（Ⅲ）萃取率可达90%以上, Au对于Al、Cu、Fe、Zn的选择性系数β分别为466、780、1 118和1 404。     

Effects of sodium tripolyphosphate and sodium carbonate on the selective flocculation of diasporic-bauxite in the presence of calcium and magnesium ions

In this study, sedimentation tests for individual minerals and artificially mixed minerals and bauxite ores were carried out to understand the effects of sodium tripolyphosphate (STPP) on the selective flocculation of diasporic-bauxite in the presence of Ca²⁺ and Mg²⁺ ions. It was found that STPP can mitigate the detrimental effects of Ca²⁺ and Mg²⁺ ions on the dispersion of diaspore and kaolinite. When separating bauxite from the mixtures of minerals and in the presence of Ca²⁺ ions, STPP can serve as better dispersant than sodium carbonate. By jointly using STPP as a dispersant and PAAS as a flocculant, a flocculation concentrate with the mass ratio of Al₂O₃/SiO₂ (Al/Si) of 7.14 and Al₂O₃ recovery of 89.97% was produced from the feed (Al₂O₃/SiO₂ = 5.64) in the presence of Ca²⁺ ions. In contrast, with using sodium carbonate as the dispersant and PAAS as the flocculant, selectivity of the flocculation separation of diasporic-bauxite was deteriorated. These experimental data were satisfactorily interpreted by some chemical reactions occurring in the pulp, which were deduced from measured zeta potentials of the reaction resultant products and residual Ca²⁺ concentrations of the pulp.     

TBP-NX混合萃取体系从盐湖卤水提锂试验研究

本文主要采用30%TBP+20%NX混合萃取体系对青海某盐湖卤水提锂过程涉及的萃取、洗涤、反萃等过程进行了详细研究。萃取过程：运用正交试验法对萃取相比、铁锂摩尔比及水相酸度进行显著性分析,得出相比对30%TBP+20%NX混合萃取体系影响显著,水相pH影响不明显;在O/A=1.5、n(Fe³⁺/Li⁺)=2和水相酸度 0.05 mol/L的最佳条件下,Li⁺、Mg²⁺萃取率分别为89.19%和1.69%;采用饱和容量法测量30%TBP+20%NX混合萃取体系单位负载锂量为2284 mg/L,所需分相时间为15 min。洗涤过程：在c(H⁺)=0.25 mol/L和O/A=20:1的最佳条件下,Li⁺、Mg²⁺的洗涤率分别为5.12%、89.46%。反萃过程：在c(H⁺)=3 mol/L和O/A=15:1的最佳条件下,Li⁺、Mg²⁺反萃率分别为80.08%、67.56%。TBP-NX混合萃取体系Li⁺负载量及反萃性能较好,但分相性能相对较弱。     

Effect of cyanobacteria Synechococcus PCC 7942 on carbonation kinetics of olivine at 20 °C

By accelerating the naturally-occurring carbonation of magnesian silicates, it would be possible to sequester some of the anthropogenic excess of CO₂ in more geologically-stable solid magnesium carbonates. Reaction rates can be accelerated by decreasing the particle size, raising the reaction temperature, increasing the pressure, using a catalyst, and hypothetically, by bacterial addition. We aimed here at assessing quantitatively the added value of photosynthetic microbial activity on the efficiency of Mg-silicates carbonation processes. Synechococcus PCC 7942 (freshwater cyanobacteria) was selected for this study. Two magnesian silicate minerals (substrates) were chosen: a synthetic forsterite with nanometer-sized grains and an industrial ultramafic slag (scoria). All tests were performed at 20 ± 1 °C in closed and sterile 1L Schott® glass bottle reactors. With the aim to elucidate the interaction between mineral phases and bacteria, we used pH and concentration measurements, scanning and transmission electron microscopy along with Raman spectroscopy. The results show that, at ambient temperature, cyanobacteria Synechococcus can accelerate silicate dissolution (i.e. Mg²⁺ release) and then magnesium carbonate nucleation and precipitation by adsorption on the produced exopolymeric substances and local pH increase during photosynthesis, respectively.     

较低温度下细菌浸出黄铜矿工艺影响因素研究

以黄铜矿为研究对象，在温度较低的浸出条件下（15℃）采用正交试验的方法考察了矿石粒度、矿浆浓度、酸度、接种量以及起始Fe²⁺浓度对氧化亚铁硫杆菌（T.f菌）摇瓶浸出黄铜矿浸出过程的影响。试验结果表明：初始Fe²⁺浓度对细菌浸铜工艺影响最为显著；在15℃下的最佳浸出工艺条件为初始Fe²⁺浓度为6g/L，酸度控制在pH=2.0，接种量保持在15%，矿浆浓度为15%，矿石粒度为-200目。