镁铝离子共存硅酸体系的聚合行为

通过对镁铝离子共存硅酸体系中硅酸胶凝时间、单硅酸聚合反应速率以及凝胶热性能的研究,得出:在pH4的微酸性条件下,硅酸体系的胶凝时间随镁铝离子共存浓度的增大而减小,且铝离子在对硅酸体系的促凝过程中起主要作用。镁铝离子共存硅酸体系的单硅酸反应速率常数比不含金属离子硅酸体系的有所增大,计算得出MA0.1+0.1硅酸体系的单硅酸平均速率常数为:0k=7.28×10?4,1k=5.62×10?4。镁铝离子共存硅酸体系凝胶的晶化转变温度与晶型转变温度,相较于不含金属离子硅酸体系的均有所降低,根据热重曲线计算出MA0.1+0.1硅酸体系水合二氧化硅的化学式为:SiO2·0.556 H2O。     

含镁离子对硅酸溶液胶凝行为的影响

向不含金属离子的硅酸溶液中加入金属镁离子,研究了体系pH值、温度、镁离子浓度对硅酸溶液胶凝时间以及镁离子对胶凝产物基团的影响。结果表明,加入镁离子的硅酸溶液体系胶凝曲线最高点出现在pH值=1.5附近;随体系温度和镁离子浓度的升高,含镁离子硅酸溶液的胶凝时间逐渐缩短;镁离子的加入导致凝胶产物部分红外特征吸收峰强度变弱。     

冶金固体废弃物精细化利用过程中中间体的聚合行为

对冶金固体废弃物精细化利用过程中中间体?含镁、铝离子硅酸体系中硅酸胶凝时间、单硅酸聚合速度及溶胶胶粒生长进行了研究. 结果表明,在pH<4的酸性范围内,Mg2+与Al3+离子促进硅酸的聚合反应,在反应初期Al3+已明显促进反应进行. 且Al3+与硅酸负离子、OH-的结合能力均强于Mg2+,其对硅酸的促凝作用较强;Mg2+和Al3+等浓度共存时,促凝效果介于单金属离子之间;Mg2+与Al3+促进了硅酸体系中溶胶胶粒的生长及SiO2粒子的长大,Al3+进入凝胶内部取代硅形成四面体配位;凝胶后所得SiO2为非晶态结构.     

Ca2+,Al3+对不含Na+硅酸体系聚合行为的影响

为排除Na+对硅酸聚合的影响,用酸解水淬硅酸钙制备了不含金属离子的硅酸溶液及含Ca2+, Al3+的硅酸溶液,研究了加入Ca2+, Al3+对体系聚合行为的影响. 结果表明,加入Ca2+后体系pH值略微降低,加入Al3+后体系pH值显著降低. 初始pH≤2时,Al3+对硅酸聚合起促凝作用,初始pH>2时,Al3+起缓凝作用. Ca2+对硅酸聚合影响不大. 硅酸凝胶后,含Al3+硅酸体系中形成Al?O?Si键,阻碍了凝胶结构水脱附;Ca2+则阻碍凝胶的晶化转变过程,且凝胶中的结构水变少. 不含金属离子、含Ca2+、含Al3+体系的化学式分别为SiO2×0.52H2O, SiO2×0.36H2O, SiO2×1.50H2O.     

锌镁替换铝硅酸盐玻璃的玻璃转变和晶化行为探索

作为重要的透明微晶玻璃体系,含镁锌的铝硅酸盐玻璃展现了优异的力学、光学特性。大量研究关注该体系的核化和晶体生长过程,但锌镁替换对铝硅酸盐玻璃玻璃转变和晶化行为影响的物理机理尚不明晰。本研究以xZnO·(11-x)MgO·22Al₂O₃·67SiO₂(x%=0%,2.2%,5.5%,8.8%,11.0%,摩尔分数)玻璃为研究对象,探究锌镁替换对铝硅酸盐玻璃的玻璃转变和晶化行为的调控规律。结果表明:随着锌逐步替换镁,玻璃转变温度慢慢下降,这是由于Zn²⁺较弱的场强和多一个电子层的屏蔽作用,玻璃网络骨架整体键合强度降低;析出晶相从单一的莫来石相转变为莫来石与锌铝尖晶石的混合相,这是由于Zn²⁺具有促进铝硅酸玻璃分相的作用;析晶温度降低,这主要是由于析晶温度附近黏温曲线变得更陡峭和析晶活化能降低。     

6种二氯酚电催化还原脱氯:表观动力学过程比较

采用自制的钯/聚吡咯(十二烷基苯磺酸钠)/钛(Pd/PPy(SDBS)/Ti)电极对二氯酚(DCP)的6种同分异构体进行了电化学还原脱氯研究。探讨了脱氯电流、溶液初始pH和污染物初始浓度对2,5-DCP脱氯过程的影响。在脱氯电流5 mA、溶液初始pH 2.5、温度25℃、污染物初始浓度100 mg·L^-1的条件下对2,3-DCP、2,4-DCP、2,5-DCP、2,6-DCP、3,4-DCP和3,5-DCP的脱氯过程进行了比较。6种DCP的脱氯产物均以苯酚为主,有少量的单氯酚产生,脱氯反应速率常数依次为4.735×10^-2、4.609×10^-2、4.845×10^-2、4.317×10^-2、3.973×10^-2、3.770×10^-2 min^-1。推测DCP的降解速率受pK_a、质子化效应和溶液pH等因素的影响,降解难度由小到大依次为2,4-DCP< 2,3-DCP< 2,5-DCP< 2,6-DCP< 3,4-DCP< 3,5-DCP。     

球形离子筛吸附剂的制备及其锂吸附性能评价

利用琼脂糖溶液的溶胶凝胶性质,通过锐孔凝固浴法,对实验室合成的Li₄Mn₅O₁₂粉体进行成型,制备了粒径2～3 mm的球形颗粒,对球形颗粒进行交联后,用1 mol·L^-1的盐酸对球形颗粒进行酸洗脱锂,最终制得球形锂离子筛吸附剂。考察球形吸附剂制备和交联的影响因素,结果表明：5%的琼脂糖浓度和90 ℃的温度为最佳制备条件,2 ml·g^-1的交联剂用量和6 h的交联时间为最佳交联条件。对球形离子筛吸附剂进行静态评价实验,结果表明锂吸附容量为4.25 mmol·g^-1,吸附速率为1.77×10^-5 s^-1,成型后离子筛吸附量是离子筛粉末的75.6%,吸附速率较粉体（3.29×10^-4 s^-1）下降一个数量级。Li⁺平衡吸附容量随平衡pH值的升高而增加,在pH>12时吸附容量高达5.5 mmol·g^-1。共存离子选择性实验表明,交联球形离子筛吸附剂对Li⁺具有高选择性,成型后离子筛可以用于盐湖卤水或者海水提锂。     

LiF对Na3AlF6-Al2O3熔盐电解阴极过程的影响

电解铝工业中铝在阴极上析出,铝析出反应的机理对电解铝生产具有理论指导意义。在运用循环伏安法研究的基础上,通过理论计算,对Na₃AlF₆-Al₂O₃和Na₃AlF₆-Al₂O₃-LiF体系中金属铝在钨电极上的电化学沉积行为以及铝钨金属间化合物的形成机理进行了研究。结果表明：两体系中铝钨金属间化合物在50 mV·s^-1≤ν≤150 mV·s^-1扫描速率下的形成过程是受扩散控制的准可逆过程。在化合物形成的过程中,两体系中Al³⁺的扩散系数从4.54×10^-9 cm²·s^-1增长到5.71×10^-9 cm²·s^-1,Al³⁺反应的活化能分别为11.14 kJ·mol^-1和10.47 kJ·mol^-1。在Na₃AlF₆-Al₂O₃-LiF体系的还原过程中,Li并没有还原析出,而在氧化过程中Al在金属间化合物中的氧化电流增大;在恒电流电解时,Al-W金属间化合物并不溶于熔盐中,会附着在工作电极表面,LiF的加入会使电极表面的WAl₄量变小,取而代之的是Al₂O₃的增加,说明LiF的加入使电解更加稳定,抑制了电极表面WAl₄的生长。     

Fe3+离子对硅酸体系聚合行为的影响

向不含金属离子的硅酸体系中加入Fe3+离子,研究了体系胶凝时间、溶胶粒径、凝胶比表面积、官能团及热稳定性的变化. 结果表明,加入Fe3+降低了体系pH值;初始pH≤2时,Fe3+起促凝作用,初始pH≥3时,Fe3+起缓凝作用. 初始pH=2时,放置24 h溶胶粒径随Fe3+浓度增加而增大,凝胶比表面积逐渐增大,Fe3+浓度为0.03 mol/L时粒径为444 nm,比表面积为1500 m2/g;初始pH=3时,放置24 h溶胶粒径随Fe3+浓度增加呈先增大后减小的趋势,最大粒径达379 nm,而凝胶比表面积逐渐减小,Fe3+浓度为0.03 mol/L时为81 m2/g. Fe3+引起聚硅酸网络结构变形,导致凝胶部分吸收峰强度减弱和移位及凝胶结合水减少和晶化转变峰变弱.     

离子交换树脂对D-甘油酸的吸附热力学和动力学

D-甘油酸是一种重要的甘油衍生物,具有解酒护肝的功能。关于D-甘油酸生产方法的研究已有不少,但对其分离方法及分离机理的研究却鲜见报道。通过静态吸附实验,研究了D-甘油酸在201×7阴离子交换树脂上的等温热力学和动力学特性。结果表明,D-甘油酸在201×7阴离子交换树脂上的最大平衡吸附容量随pH的增加而降低,其吸附等温线符合Freundlich模型。在293~308 K下,吸附焓变为14.77 kJ·mol^-1,表明该吸附过程为吸热过程。升高温度有利于提高吸附速率,但对最大平衡吸附容量影响不大。同时,采用动边界模型描述D-甘油酸在该树脂上的交换行为,分别考察了料液浓度、树脂粒径和温度对交换过程的影响。交换过程的吸附速率随D-甘油酸浓度和温度的增加而增大,但随树脂粒径的增大而减小。研究表明该离子交换过程的速率控制步骤为颗粒扩散过程,交换过程的反应速率常数k₀为1.22×10^-3,反应级数a为0.631,表观活化能E_a为14.90 kJ·mol^-1,并得到了动力学总方程。     

Investigation of solution chemistry to enable efficient lithium recovery from low-concentration lithium-containing wastewater

In the production of lithium-ion batteries (LIBs) and recycling of spent LIBs, a large amount of low-concentration lithium-containing wastewater (LCW) is generated. The recovery of Li from this medium has attracted significant global attention from both the environmental and economic perspectives. To achieve effective Li recycling, the features of impurity removal and the interactions among different ions must be understood. However, it is generally difficult to ensure highly efficient removal of impurity ions while retaining Li in the solution for further recovery. In this study, the removal of typical impurity ions from LCW and the interactions between these species were systematically investigated from the thermodynamic and kinetics aspects. It was found that the main impurities (e.g., Fe³⁺, Al³⁺, Ca²⁺, and Mg²⁺) could be efficiently removed with high Li recovery by controlling the ionic strength of the solution. The mechanisms of Fe³⁺, Al³⁺, Ca²⁺, and Mg²⁺ removal were investigated to identify the controlling steps and reaction kinetics. It was found that the precipitates are formed by a zero-order reaction, and the activation energies tend to be low with a sequence of fast chemical reactions that reach equilibrium very quickly. Moreover, this study focused on Li loss during removal of the impurities, and the corresponding removal rates of Fe³⁺, Al³⁺, Ca²⁺, and Mg²⁺ were found to be 99.8%, 99.5%, 99%, and 99.7%, respectively. Consequently, high-purity Li₃PO₄ was obtained via one-step precipitation. Thus, this research demonstrates a potential route for the effective recovery of Li from low-concentration LCW and for the appropriate treatment of acidic LCW.     

Kinetics of xylose dehydration into furfural in acetic acid

In this paper kinetics of xylose dehydration into furfural using acetic acid as catalyst was studied comprehensively and systematical y. The reaction order of both furfural and xylose dehydration was determined and the reaction activation energy was obtalned by nonlinear regression. The effect of acetic acid concentration was also investi-gated. Reaction rate constants were galned. Reaction rate constant of xylose dehydration is k1 ? 4:189 . 1010 ?A.0:1676 exp ?108:6.1000RT . ., reaction rate constant of furfural degradation is k2 ? 1:271 . 104?A.0:1375 exp?63:413.1000RT . and reaction rate constant of condensation reaction is k3 ? 3:4051 . 1010?A.0:1676 exp?104:99.1000RT .. Based on this, the kinetics equation of xylose dehydration into furfural in acetic acid was set up according to theory of Dunlop and Furfural generating rate equation is dd?F.t ? k1?X.0e?k1t?k2?F.?k3?X.0e?k1t?F.. ? 2015 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. Al rights reserved.     

锂辉石浸出液提锂除杂规律研究

碳酸锂是一种基础锂盐, 不仅广泛应用于传统化工行业, 也是生产锂电池的重要原料, 近年来锂电产业蓬勃发展, 极大推动了原料碳酸锂的提取与制备研究。为了提取锂辉石中的锂来制备碳酸锂, 利用沉淀溶解-平衡理论分析锂浸出液的除杂规律。对锂辉石进行转型焙烧、酸化焙烧、浸取, 锂辉石中98%左右的锂可进入液相, 得到锂浸出液, 然后根据溶解平衡理论确定3步除杂净化条件：1）中和pH至6.5除大部分Al ³⁺和Fe ³⁺;2）加入氧化剂将Fe ²⁺氧化成Fe ³⁺, 调 pH 至8.0除Fe ³⁺;3）调pH至10.0, 加入理论量碳酸钠（以液相Ca ²⁺计）, 最终Al ³⁺、Fe ³⁺、Mg ²⁺ 等浓度低于10 ^-6 mol/L, Ca ²⁺质量分数约为2×10 ^-5。     

金属离子对水热法制备半水硫酸钙晶须的形貌及粒径的影响

以二水硫酸钙为原料,采用水热法制备了半水硫酸钙晶须。通过单因素实验得出制备半水硫酸钙晶须的较优工艺条件为：反应温度120℃、料浆质量分数2%、反应时间2h、搅拌速度200r/min,此时所得晶须产物平均直径2.4μm,长径比103.9,晶须呈长针状、规则统一,分散性好。探讨了K⁺、Mg²⁺、Cu²⁺、Fe³⁺、Al³⁺对较优工艺条件下制备的半水硫酸钙晶须形貌及粒径的影响,结果表明：金属离子对晶须产物形貌及粒径有显著影响。其中低浓度的Mg²⁺、Cu²⁺有助于获得小直径、高长径比的晶须产物;Al³⁺、Fe³⁺对晶须的生长有较强的抑制作用,特别是低浓度的Al³⁺、Fe³⁺使得晶须的形貌发生明显的变化,导致长径比较低;除K⁺外,金属离子浓度越高,所得晶须产物直径越大,长径比越小,并发生团聚现象,晶须由针状变为短棒状,分散性变差。同时探讨了金属离子的作用机理。     

Evaluation of the microporosity of pillared [Fe(CN)6]–MgAl–LDHs

Layered double hydroxides (LDHs) containing Mg²⁺ and Al³⁺ in the basic layers and NO⁻₃ as an interlayer anion were synthesized by the method of coprecipitation (pH 10). By changing the Mg²⁺/Al³⁺ ratio (1.5–4.5), the charge density on the (NO₃)–MgAl–LDH sheets was varied. After pillaring with Fe(CN)³⁻₆, which was based on an anion exchange process, the interlayer space became accessible. This was reflected in the large created surface areas and micropore volumes. The applied models for the calculation of the micropore size distributions (Maes–Zhu–Vansant and Horvath–Kawazoe) gave matching results, revealing narrow distributions for all the samples, with the majority of the pores smaller than 0.71 nm. A correlation was found between the Mg²⁺/Al³⁺ ratio and the resulting microporosity after pillaring. The optimal ratio was situated around 3.3, resulting in a pillared [Fe(CN)₆]–MgAl–LDH with a Langmuir surface area of 499 m²/g and a micropore volume between 0.158 ml/g (μPV_min) and 0.177 ml/g (μPV_max). As an alternative, direct coprecipitation of the pillared LDHs was evaluated. This one-step mechanism proved to be a method producing similar results. Taking all this into consideration, one can conclude that hexacyanoferrate(III) complexes form ideal anionic pillars for the creation of microporous layered double hydroxides.     

硫代杯[4]冠-4在硝酸体系中对Sr2+的萃取

乏燃料后处理的高放废液分离过程中,发展新型分离材料实现对锶的高效萃取至关重要。合成了1,2交替构象的硫代杯[4]冠-4(TCACE),利用FT-IR、¹H NMR和MS对目标产物进行了表征。研究不同稀释剂对萃取的影响,优化得出CH₂Cl₂为稀释剂,在硝酸浓度为3 mol·L^-1,有机相中硫代杯[4]冠-4浓度为1×10^-3 mol·L^-1,水相中Sr²⁺浓度为5×10^-4 mol·L^-1,萃取温度为25℃,萃取80 min条件下,平均传质系数为1.36×10^{-5 m}·s^-1,Sr²⁺的分配比为0.69。分析了不同条件对硫代杯[4]冠-4对Sr²⁺的萃取影响,研究了萃取计量方程式,实验结果表明萃合物为{Sr(NO₃)₂}·{TCACE}。研究了TCACE对其他金属离子Mo⁶⁺、Ni²⁺、Ag⁺、Sn⁴⁺等的萃取效果,表明对Sr²⁺具有较好的选择性。     

Preparation of novel porous solids from alumina-pillared fluorine micas by acid-treatment

New porous solids from alumina-pillared fluorine micas (APMs), which were obtained from synthetic Na-tetrasilicic fluorine mica [NaMg_2.5Si₄O₁₀F₂], were prepared by sulfuric acid-treatment under mild conditions at 25 °C. The products were investigated by XRD, ICP, SEM, TEM and N₂ adsorption–desorption isotherm at 77 K. XRD measurements indicated that the interlayer pillared structure having a large basal spacing collapsed during the early stages of the acid-treatment. ICP analyses indicated that Al³⁺ and Mg²⁺ ions were leached out from the pillared micas during the acid-treatment. The pore properties of the leached products were found to differ from those of the mother pillared micas: the acid leaching of the pillared micas leads to the formation of mesopores around 3.2 nm in diameter. The correlation between the change in pore properties and cation elution behavior suggests that the mesopore formation results from the leaching of Mg²⁺ ions from the octahedral sheet of the pillared micas. The leached products thus obtained retained the flaky morphology of the mother pillared micas. These results show that the mild acid-treatment using APMs provides a novel route for obtaining unique mesopore solids having the large particle sizes of the mother micas.     

Al3+、Na+和Mg2+对二水硫酸钙结晶的影响

采用CaHPO₄·2H₂O-H₂SO₄-H₃PO₄-H₂O体系模拟湿法磷酸生产过程,以磷矿浆成分为依据,在单因素条件下分别研究Al³⁺、Na⁺和Mg²⁺对结晶和CaSO₄·2H₂O水洗速率的影响。研究发现：添加Al³⁺有利于CaSO₄·2H₂O晶体粒径增加;添加Na⁺使得0.9% Na₂O含量的Na⁺引起CaSO₄·2H₂O晶体团聚,有利于水洗;Mg²⁺增加溶液黏度,严重影响晶体生长和水洗速率。通过X射线衍射、扫描电子显微镜对CaSO₄·2H₂O进行表征,发现其晶体生长符合非完整光滑突变界面模型,杂质离子影响反应速率和晶面生长速度。     

氨水沉淀-胶溶-EISA法合成介孔氧化铝

以廉价且无毒的无机铝盐为铝源,十六烷基三甲基溴化铵(CTAB)为模板剂,结合氨水沉淀-胶溶-溶剂挥发自组装(EISA)方法,合成介孔氧化铝。考察胶溶过程中n(HNO3)∶n(Al~(3+))及n(CTAB)∶n(Al~(3+))对合成介孔氧化铝的孔径、孔容及比表面积等结构的影响。结果表明,加入HNO3胶溶和CTAB模板剂均可以提高合成介孔氧化铝的孔道有序度。当n(HNO_3)∶n(Al~(3+))=0~0.5时,氧化铝的有序度随着n(HNO_3)∶n(Al~(3+))的增加而增加。而有序度随着n(CTAB)∶n(Al~(3+))先增后降,当n(CTAB)∶n(Al~(3+))=0.1时有序度最好。n(CTAB)∶n(Al~(3+))过高,导致孔径分布范围变宽。氧化铝的孔径、孔容和比表面积主要受n(CTAB)∶n(Al~(3+))的影响。     

Structure and properties of forming adsorbents prepared from different particle sizes of coal fly ash

In this paper, different particle sizes of coal fly ash FA-R (D50=15.75μm), FA-A (D50=3.61μm) and FA-B (D50=1.73μm) were treated with NaOH solution to prepare the forming adsorbents FFA-R, FFA-A and FF...