水溶性改性细菌纤维素的制备及表征

将细菌纤维素再生后溶于NaOH/尿素/硫脲溶液,在碱性条件下与丙烯酰胺合成水溶液的改性细菌纤维素。红外光谱、元素分析和核磁共振谱图证实了改性细菌纤维素的存在。研究表明：当葡萄糖与丙烯酰胺摩尔比大于1：4.6时,反应产物是水溶性的;当葡萄糖与丙烯酰胺摩尔比为1：8时,产物的羟基总取代度约为0.412-0.502.     

Preparation of dialdehyde cellulose hydrazone derivatives andevaluating their efficiency for sewage wastewater treatment

The cellulose hydrazone derivative is a novel product prepared from dialdehyde cellulose with 2-hydrazino-3,5,6,7tetrahydrocyclopentanethieno[2,3-d]-pyrimidin-4(4H)-one under suitably selected conditions. It was found that the reaction of dialdehyde cellulose with the 2-hydrazino derivative decreased progressively in the series cellulose powder, viscose wood pulp and cotton linter. The principal objective of this research was to evaluate the effectiveness of dialdehyde cellulose hydrazone derivatives on sewage wastewater settling, percentage of total suspended solids (TSS), carbon oxygen demand (COD), and iron and chromium removal. About 30-50% of chlorine was removed after treatment using dialdehyde cellulose hydrazone derivatives, thus indicating their good efficiency for halogen removal. Cellulose hydrazone derivatives were recommended as good coagulants and removed Fe and Cr by 73.9% and 66.7%, respectively. Jar tests revealed that the wastewater was best treated with the addition of chemical coagulants such as FeCl₃ or Al₂(SO₄)₃ combined with cellulose hydrazone derivatives at optimum doses. The optimum conditions produced better cleaning-up and improved removal of COD and TSS up to 77% and 97%, respectively.     

氢氧化钠/尿素/硫脲溶剂体系对纤维素溶解性能研究

通过设计正交实验,研究不同组成的氢氧化钠/尿素/硫脲溶剂体系对纤维素的溶解性能,确定了该溶剂体系中各组分的最佳含量,并通过X-射线衍射分析、红外光谱分析、热重分析等手段,表征了该溶剂体系获得的再生纤维素膜的结构和性能。结果表明:该溶剂体系对纤维素有良好的溶解性能,且溶解的纤维素再生后为纤维素Ⅱ,但其热稳定性低于原纤维素。     

Heavy metal ion scavengers from cyanuric chloride

Cyanuric chloride was reacted with polyamines and thiourea, and subsequent hydrolysis of the isothiouronium salt yielded amine polymers with divalent sulfur. The polymers scavenge cupric, cadmium, lead, and mercuric ions from considerably concentrated hydrogen chloride solutions, and they were compared with polystyrene—sulfonic acid resin. Zinc, cobaltous, and nickel ions are adsorbed only at relatively high pH (4.8–6.8). Removal of cupric, cadmium, and mercuric ions is not affected by the addition of sodium chloride.     

硫脲型螯合纤维素对铜吸附性能的研究

将自制合成的三种新型硫脲型螫合纤维素——硫晚棉纤维（CC－TU），氨基硫脲棉纤维（CC－TSC）和二苯硫脲棉纤维（CC－DPTU）应用于钢的吸附性能的研究，采用火焰原子吸收法测定选择了吸附和解吸的最佳条件。在所选择条件下，这些螫合纤维素对钢具有吸附速度快、吸附完全，吸附能力强，解吸容易和洗脱体积小等特点。     

Solubility of cellulose III in sodium hydroxide solution

Studies on cellulose III solubility have been conducted in 8.5% NaOH solution with and without the presence of added substances, such as acrylamide, acrylic acid, acrylonitrile, and thiourea. The highest value of cellulose III solubility was obtained as a result of the introduction thiourea and acrylamide in a 5% ratio of NaOH into NaOH solution. Moreover, dissolving conditions proved to be of great importance. Cellulose III introduced into NaOH solution and repeatedly frozen and unfrozen three times dissolved 50% (dissolving with 5% thiourea). The soluble cellulose fraction showed significantly lower molecular mass in comparison with its insoluble fraction. Comparative studies on cellulose crystallinity using the CP / MAS ¹³C-NMR method showed a satisfactory compatibility of results with determinations obtained from the X-ray method. © 1993 John Wiley & Sons, Inc.     

X-ray studies of regenerated cellulose fibers wet spun from cotton linter pulp in NaOH/thiourea aqueous solutions

Regenerated cellulose fibers were fabricated by dissolution of cotton linter pulp in NaOH (9.5 wt%) and thiourea (4.5 wt%) aqueous solution followed by wet-spinning and multi-roller drawing. The multi-roller drawing process involved three stages: coagulation (I), coagulation (II) and post-treatment (III). The crystalline structure and morphology of regenerated cellulose fiber was investigated by synchrotron wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) techniques. Results indicated that only the cellulose II crystal structure was found in regenerated cellulose fibers, proving that the cellulose crystals were completely transformed from cellulose I to II structure during spinning from NaOH/thiourea aqueous solution. The crystallinity, orientation and crystal size at each stage were determined from the WAXD analysis. Drawing of cellulose fibers in the coagulation (II) bath (H₂SO₄/H₂O) was found to generate higher orientation and crystallinity than drawing in the post-treatment (III). Although the post-treatment process also increased crystal orientation, it led to a decrease in crystallinity with notable reduction in the anisotropic fraction. Compared with commercial rayon fibers fabricated by the viscose process, the regenerated cellulose fibers exhibited higher crystallinity but lower crystal orientation. SAXS results revealed a clear scattering maximum along the meridian direction in all regenerated cellulose fibers, indicating the formation of lamellar structure during spinning.     

纤维素在NaOH/硫脲/尿素水溶液中的流变性能研究

采用新型碱复合溶剂NaOH/硫脲/尿素水溶液作为溶剂溶解纤维素,对纤维素溶液的流变性能进行探索,从而为纤维素/NaOH/硫脲/尿素溶液纺丝提供理论依据。研究结果表明,纤维素溶液表现出非牛顿流体的性质,溶液的粘流活化能随纤维素质量分数以及剪切速率的不同而有所差异,纤维素溶液的结构黏度指数随着温度的升高、纤维素质量分数的增大而增大。5~25℃是所测的纤维素溶液纺丝的适宜温度范围,随着温度的升高,凝胶点开始出现,且凝胶点随着温度的升高向高频率的方向移动。随着纤维素质量分数的增大,纤维素溶液凝胶温度降低。     

Development of a fixed‐bed column with cellulose/chitin beads to remove heavy‐metal ions

Environmental friendly cellulose/chitin beads, having relatively high mechanical properties, were successfully prepared from a blend of cellulose and chitin in 6 wt % NaOH/5 wt % thiourea aqueous solution by coagulating with 5% H₂SO₄ aqueous solution. The ability of the beads to adsorb Pb²⁺ in an aqueous solution was measured with a fixed‐bed column. The effects of important parameters, to design an adsorption column of the cellulose/chitin beads for fixed‐bed columns, were investigated. The breakthrough curves for the adsorption behavior indicated that the column performance was improved with decreasing initial lead concentration, ionic strength, flow velocity or bead size, as well as increasing pH dependence and bed height. Column studies showed that constants, calculated from the experimental data, and the Bed Depth Service Time (BDST) model had a good correlation. The columns were easily regenerated by treating with 0.1 mol/L HCl aqueous solution after the adsorption of metals, providing a simple and economical method for removal and recovery of heavy metals. After four adsorption–desorption cycles, the efficiency of column for the removal of lead was not significantly reduced (not more than 5%). It is shown that heavy‐metal biosorption processes in fixed‐bed columns could give a broad range of potential industrial applications. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 684–691, 2004     

Rapid and highly efficient synthesis of thioureas in biocompatible basic choline hydroxide

A straightforward and convenient synthesis of symmetrical thiourea derivatives by the reaction of primary amines and carbon disulfide in biocompatible basic choline hydroxide is presented. A variety of biologically important thiourea derivatives can be obtained in good to excellent yields without a tedious work-up under mild reaction conditions. A series of primary aliphatic and aromatic amines with different substituted functional groups have been converted to thiourea derivatives under milder reaction conditions and short reaction times.     

Structural changes of regenerated cellulose dissolved in FeTNa,NaOH/thiourea,and NMMO systems

Regenerated cellulose was prepared from microcrystalline cellulose (MCC) via dissolution in three well‐known nonderivatizing systems: ferric chloride/sodium tartarate/sodium hydroxide (FeTNa), sodium hydroxide/thiourea (NaOH/thiourea), and N‐methylmorpholine‐N‐oxide (NMMO) systems. The effect of regeneration using the different systems on the supramolecular structure of the regenerated celluloses was studied using X‐ray diffraction and Fourier transform infrared (FTIR). The effect of regeneration on supermolecular structure, morphology, and thermal stability of regenerated celluloses were studied using scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The effect of regeneration systems used on the chemical reactivity of cellulose toward carboxymethylation, acetylation, and cyanoethylation reactions was briefly studied. The results showed dependence of all the aforementioned properties on the dissolution reagent used in spite of that all studied reagents cause the same change in cellulose crystalline structure (from cellulose I to cellulose II). The degree of polymerization, crystallinity, and thermal stability of the regenerated cellulose (RC) samples were in the following order: NaOH/thiourea RC > FeTNa RC > NMMO RC. SEM micrograph showed unique surface for the NMMO RC sample. The reactivity of the different regenerated cellulose samples toward carboxymethylation, cyanoethylation, and acetylation depended mainly on the reaction system and conditions used rather than on crystallinity of regenerated cellulose. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

All-cellulose composites prepared by partially dissolving cellulose using NaOH/thiourea aqueous solution

All-cellulose composites (ACCs) were prepared by partially dissolving cellulose in the filter paper using NaOH/thiourea aqueous solution. The effects of dissolution time, thiourea ratio, and temperature on the properties of ACCs were investigated. ACCs were characterized by scanning electron microscope, attenuated total reflectance Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, and tensile tests. The results revealed that the fibers in ACCs were tightly intertwined. The crystalline form of cellulose in ACCs was transformed from type I to type I/II mixture, and the crystallinity decreased from 77.32 to 51.40%. The tensile strength of ACCs was remarkably improved to 23.16 MPa. The results confirmed ACCs had a high potential for practical applications in the packaging field.     

手性硫脲对映选择性催化Henry反应研究

手性硫脲是不对称催化反应中一类典型的双功能有机小分子催化剂。文章合成了6种新型手性硫脲衍生物,以FT-IR和1H NMR进行了表征。同时以HPLC检测了手性硫脲催化剂在对映选择性催化Henry反应中的催化活性和对映选择性并获得了较高的产率和ee。实验证明,硫脲衍生物中氯元素取代基能够促进底物的活化,酰基硫脲的分子内氢键对催化剂的对映选择性催化具有较大的影响作用。     

棉浆粕在NaOH/硫脲/尿素溶剂体系中的溶解及流变性能

研究了棉浆粕在NaOH/硫脲/尿素溶剂体系中的溶解特性,并对溶解得到的棉浆粕溶液的流变性能进行了研究。结果表明:当溶解温度为-10℃,混合溶剂中NaOH、硫脲、尿素、水的质量比为7∶9∶9∶75,溶解时间为30 min时,棉浆粕的溶解程度较大;该种溶液为假塑性流体,溶液的黏度随剪切速率的增大而降低。     

Graft copolymerization of vinyl monomers onto modified cotton. IX. Hydrogen peroxide–thiourea dioxide redox system induced grafting of 2-methyl-5-vinylpyridine onto oxidized celluloses

Cotton cellulose was independently oxidized with potassium periodate, potassium dichromate-sulfuric acid, and potassium dichromate–oxalic acid, and the resulting oxidized celluloses were further modified by treatment with chlorous acid or sodium borohydride. The various modified celluloses so obtained were grafted with 2-methyl-5-vinylpyridine using a thiourea–dioxide–H₂O₂ redox system. It was found that the initiation characteristics of the cellulose samples vary widely with the oxidizing agent used. Further modification of the oxidized celluloses by treating them with chlorous acid enhances considerably their susceptibility toward grafting. The opposite holds true when these oxidized celluloses were modified by sodium borohydride treatment. Excluding thiourea dioxide from the polymerization system offsets grafting onto cotton cellulose while considerable grafting takes place on the various oxidized celluloses and their further modified samples. The work was also extended to study the factors which affect the graft uptake, homopolymer formation, and total conversion. In addition, the reactions involved in initiation of grafting were elucidated.     

Fabrication of a model cellulose surface from straw with an aqueous sodium hydroxide/thiourea solution

Model cellulose surfaces were prepared with both microcrystalline cellulose and cellulose isolated from wheat straw with different molecular weights. A sodium hydroxide/thiourea aqueous solution, instead of any organic solvents, worked as the solvent for dissolving cellulose, and model cellulose films were prepared by a two‐step method: first, the cellulose solution was deposited onto the surface of the substrate with the spin‐coating method, and second, the as‐prepared film was washed with deionized water to remove the impurities and was formed with a flattened surface. Atomic force microscopy was used to measure the morphology, surface roughness, and thickness of the cellulose thin films. X‐ray photoelectron spectroscopy and energy‐dispersive X‐ray spectrometry were used to characterize the surface chemical information of the films. The results revealed that model cellulose surfaces could form from both kinds of cellulose. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

NaOH/硫脲/尿素预处理对棉纤维TEMPO选择性氧化的影响

采用NaOH/硫脲/尿素体系对棉纤维进行预处理,再进行选择性氧化,可以有效提高氧化棉纤维的羧基生成量。对比研究预处理棉纤维与普通棉纤维经2,2,6,6-四甲基哌啶氮氧自由基(TEMPO)选择性氧化后的羧基含量、纤维形态以及黏度。结果表明,经NaOH/硫脲/尿素体系预处理能够加快氧化反应速率,增加羧基生成量,但对纤维有一定的损伤。其中,羧基生成量随着纤维质量分数的增加呈先增加后减少的趋势,当纤维素质量分数为6%时,羧基生成量最大,棉纤维的可及度和反应性提高。纤维形态分析表明,经NaOH/硫脲/尿素体系预处理的棉纤维润胀溶解程度要大于未预处理的氧化棉纤维;在TEMPO的氧化条件下,氧化棉纤维的相对黏度随着纤维素质量分数增加而增加;当纤维素质量分数较高时,氧化过程中氧化棉纤维的羧基生成量和降解程度都近似于原纤维。     

对称和非对称取代硫脲的合成

针对不同活性的取代硫脲,采用脂肪胺或取代苯胺与二硫化碳或不同种类的异硫氰酸酯反应,合成了4种对称的和12种非对称的硫脲衍生物。给出了简便的合成方法。列举了所有合成化合物的mp或bp。     

[2.2]Paracyclophane-Derived Planar-Chiral Hydrogen-Bond Receptors

The development of planar-chiral hydrogen-bond donors based on the [2.2]paracyclophane scaffold is discussed. General strategies to access functionalized enantiopure [2.2]paracyclophane derivatives are briefly reviewed, with the focus on suitable precursors for the synthesis of planar-chiral thiourea derivatives. The synthesis of fourteen hydrogen-bond donors is described. The interaction of four thiourea derivatives with hydrogen-bond acceptors (DMSO and tetramethylammonium chloride) was investigated by ¹H NMR spectroscopy and X-ray crystallography. A selection of enantiomerically pure planar-chiral derivatives was applied in asymmetric hydrogen-bond catalysis.     

The adsorption of mercuric ions by chitosan

The adsorption of mercuric ions by chitosan was investigated. The study of the adsorption kinetics shows that the rate of adsorption of mercuric ions on chitosan can be interpreted in terms of intraparticle diffusion as the rate-limiting step. The experimental data of adsorption equilibrium from mercuric chloride solutions correlate well with the Langmuir isotherm equation, although at high-solute concentrations, a multilayer type of adsorption with the subsequent increase in the uptake is observed. Column experiment confirms the ability of chitosan for the removal of mercuric ions from solutions in the absence of a high concentration of chlorides.