基于浸取pH依赖性的离子吸附型稀土分类及高效浸取方法

研究了稀土及主要杂质离子被硫酸铵浸出的pH依赖性。结果证明稀土和钙镁等离子的浸取率在低酸度范围内随酸度增大有明显提高,继续提高酸度并不会进一步提高浸取率,而铝、铁、钪等易水解金属离子的浸取率随酸度增大而持续增加。据此,基于离子吸附型稀土的定义及浸取所需pH值的范围,将离子吸附型稀土进一步区分为易浸稀土和难浸稀土,其中难浸稀土是需要在弱酸性条件（pH≤4）下才能浸取的被胶体等强吸附剂吸附的稀土离子。由于在不同地区和不同矿层及不同粒级的样品中所含强吸附剂的量以及磨蚀pH（pH_d）和交换pH（pH_t）的不同,这两类离子吸附型稀土的比例不同。对于pH_d和pH_t值较高的矿样,适当提高浸取酸度可以显著提高稀土浸取率。为此,提出了分阶段浸取稀土并增加石灰水护尾工序来保证稀土浸取率和尾矿安全稳定性的原则流程。     

离子吸附型稀土矿中浸出相稀土元素含量的浸取方法研究

将风化壳离子吸附型稀土矿原矿样品加工至0.149 mm,使用35 g/L硫酸铵溶液(pH为4.0)作为浸取剂,提取浸出相稀土元素.考察了提取浸出相稀土元素时,样品粒度、浸取剂浓度及用量、浸取剂酸度、浸取方式、浸取时间等条件的影响,确定最佳试验条件,利用电感耦合等离子体质谱法(ICP-MS)测定样品溶液中浸出相稀土的总量...     

风化壳淋积型稀土矿多级逆流浸取实验研究

风化壳淋积型稀土矿的开采主要通过浸矿剂离子与吸附在黏土矿物表面的稀土离子发生离子交换浸出反应实现。以(NH₄)₂SO₄为浸矿剂,采用多级逆流浸取的方式研究了风化壳淋积型稀土矿的浸矿过程,通过在逐级浸取过程中浸出液组分的变化分析了矿土中稀土离子(RE³⁺)和主要杂质铝离子(Al³⁺)的浸出行为,并基于浸矿剂的消耗规律探讨了浸矿剂离子与RE³⁺和Al³⁺的离子交换反应机制以及原矿土的净吸附量。结果表明,在浸矿液逐级浸取新鲜矿土的过程中,浸出液中的RE³⁺和Al³⁺浓度逐渐增加,铵根离子(NH₄⁺)逐渐消耗,交换进入浸出液中的RE³⁺和Al³⁺逐级减少;同时,浸出液中的硫酸根离子(SO₄^2-)逐级损耗,说明新鲜矿土除因发生离子交换反应消耗NH₄<...     

刚果红和结晶紫在锯末上的吸附性能研究

采用静态吸附法研究了刚果红和结晶紫在锯末上的吸附特性。结果表明,锯末是具有高脱色率的廉价吸附剂,最大脱色率可达96%。在pH4~10范围内,酸度对结晶紫的吸附影响较小,随着pH值增大,脱色率从96.6%缓慢降至91.1%。pH值对刚果红吸附影响较大,pH从4增大到7,脱色率迅速从22.5%增加至96.0%,然后,随pH值升高脱色率缓慢下降至91.4%。两种染料在锯末上的吸附等温线均较好的符合Freundlich方程,吸附动力学可以用拟二级动力学模型描述。计算了相应的吸附等温线参数和吸附动力学参数。     

离子吸附型稀土浸取试剂和富集回收技术的演变——从抑杂浸取到强化浸取及分阶段的选择-强化浸取

硫酸铵浸取离子吸附型稀土，碳酸氢铵沉淀法富集回收工艺在工业上已经使用了30多年。其突出优点是浸取效率高，沉淀富集产品质量好，生产成本低。然而，其对环境的影响只有在确保浸出液不外泄，水和溶液都能循环利用的前提下才能得到控制。近10年来，人们着力于研发用非铵试剂来浸矿，以解决氨氮超标问题。尽管在降低氨氮污染方面取得了很好成绩，但是，在以往甚至当前的原地浸矿方式下，收液率很难超过90%，环保问题无法根本解决。本文基于当前该领域与浸取剂，沉淀剂和萃取剂及稀土浸取富集相关的研究成果，客观地分析了各种试剂和方法的优缺点，讨论了浸取策略从抑杂浸取到强化浸取以及分阶段的选择-强化浸取的变迁，这种变迁需要后续富集回收技术的支撑作用以提高效率和产品质量、降低消耗和成本。而试剂本身存在的一些不足可以通过它们之间的相互耦合和后续富集回收流程的优化来克服。据此，对当前存在的问题和未来发展趋势提出了一些基本观点。     

赣南信丰风化壳淋积型稀土矿的吸附特性

风化壳淋积型稀土矿体吸附特性对于提高原地浸矿稀土浸取率具有重要意义。通过筛分获得不同粒径的风化壳淋积型稀土矿样,测试各粒径矿样的离子相稀土品位、比表面积、表面形貌以及矿物成分等,分析稀土离子在矿体中的吸附特性。研究结果表明:赣南信丰类型的稀土矿体中矿物成分有高岭石、钾长石、石英、电气石、白云母等,这5种主要矿物成分的总质量比重达到90.13%,不同矿物成分的粒度有明显的差异,小粒径矿样中高岭石和白云母的含量增加,矿样的稀土离子吸附量与高岭石等黏土矿物的含量成正相关;基于稀土离子在矿体颗粒表面凹坑的单位面积吸附量与孔径和粒径成对数正态分布,建立了稀土离子吸附量与矿体颗粒表面凹坑孔径之间关系的分析模型,运用该模型计算得到赣南信丰类型的有效吸附孔径为2.0~20.0 nm。     

不同风化程度离子型稀土矿赋存特征及浸出规律研究

创新在于对同一风化壳矿体的全风化层、半风化层、微风化层进行对比分析其赋存特征,并进行全风化层、半风化层中稀土的浸出试验,分析了浸取剂pH值、浓度、流速、液固比对稀土离子及杂质铝浸出的影响,并提出如何提高全风化层、半风化层中稀土的浸出率及降低杂质含量。研究结果表明:半风化层、微风化层中稀土矿粗粒级产率高且仍赋存较高含量的稀土;随风化程度降低,石英、黏土矿物含量减少,长石、云母含量增加,离子相稀土比例减小,胶态相与矿物相增加;随粒级减少,离子相稀土比例增加,矿物相稀土反之,而胶态相稀土平均分布于各粒级;对比两层稀土浸出情况,可通过降低浸取剂pH值、增加浓度、降低流速、增加液固比,来提高半风化层稀土浸出效果。     

改性蔗渣纤维对稀土离子吸附特性研究

为了提高甘蔗渣的吸附量,通过均苯四甲酸二酐(PMDA)改性蔗渣纤维制备PMDA-SCB以提高其吸附回收稀土离子的能力。FTIR和SEM表征分析,蔗渣纤维表面接枝了大量的羧基基团,为吸附目标离子提供大量的活性位点。实验结果表明:pH值对吸附剂吸附效果影响较大,最佳pH值为6。PMDA-SCB对La~(3+),Gd~(3+),Y~(3+)的Langmuir等温吸附量分别为74.85,88.90和43.30 mg·g~(-1),是未改性蔗渣SCB的9.2,9.1和10倍。准二级动力学方程能更好地描述吸附方程,其R2大于0.999。PMDA-SCB经过4次吸附解析循环后,其吸附量降低率比较少,说明PMDA-SCB能有效去除并回收废液中的稀土离子。     

浮石负载壳聚糖吸附去除水中丙溴磷

通过浮石负载壳聚糖制备了吸附剂壳聚糖/浮石复合物,采用扫描电子显微镜(SEM)、热重分析(TGA)、元素分析、傅里叶红外光谱(FT-IR)、X射线衍射(XRD)和X射线荧光光谱(XRF)等技术手段表征了吸附剂性质,考察了吸附剂量、吸附时间、溶液pH值、离子强度和温度对该吸附剂吸附去除水中丙溴磷的影响,研究了再生吸附剂的吸附性能。结果表明,负载在浮石上的壳聚糖占吸附剂总量的8.69%;在p H值3.0~7.0内,壳聚糖/浮石对丙溴磷的吸附率大于90%;这种吸附剂对丙溴磷的吸附受溶液离子强度影响较小,随温度升高而稍微减小。在溶液温度25℃、pH=7.0、丙溴磷浓度40 mg/L、壳聚糖/浮石剂量为0.7 g/L和吸附平衡时间为90 min条件下,此吸附剂对丙溴磷最大吸附率为93.3%(最大吸附量为53.4 mg/g)。壳聚糖/浮石连续经过3次吸附/再生循环,每次循环对丙溴磷的吸附率下降约12%。可见壳聚糖/浮石通过吸附可有效地去除水中的农药丙溴磷。     

风化壳淋积型稀土矿开发的现状及展望

风化壳淋积型稀土矿是中重稀土的主要来源,它的开发一直受到稀土工业的极大关注。评述了风化壳淋积型稀土矿的成矿原因、矿床特征、稀土矿物在矿体垂直剖面中的组成和分布,以及矿石含水的多样性、酸碱缓冲性、吸附离子的稳定性和吸附离子的可交换性等理化性质。阐述了稀土离子在风化体系中的迁移富集规律和所形成的稀土配分特征。介绍了池浸、堆浸和原地浸出三代浸取工艺演化过程的科技进步,探讨了稀土浸出机制及浸出过程的强化,比较了几种浸取剂的浸取效果,简述了前两代工艺留下的采矿区和堆场区的植被恢复与土壤修复。结合原地浸出工艺的生产实际,提出了今后开发风化壳淋积型稀土矿的发展方向。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.