磁性珠状纤维素制备工艺研究

本文较系统地研究了在采用反相悬浮包埋技术制备磁性珠状纤维素的过程中，纤维素的分子量、分散介质的性质、搅拌速度和O／W值等诸因素对磁性纤维素珠体的粒径、粒径分布和磁性材料包封率的影响。得到平均粒径在300微米以下，粒径分布指数小于1．4的磁性珠状纤维素，收率可达90％以上，且磁性材料（γ－Fe2O3）包封率较高。     

磁性交联壳聚糖微球对Cu2+的吸附性能研究

以Fe_3O_4为磁核,环氧氯丙烷为交联剂,制备磁性交联壳聚糖微球(MCB)。采用FTIR、XRD及SEM对MCB进行表征分析,结果表明壳聚糖发生了交联反应,且Fe_3O_4被壳聚糖包埋。通过正交试验L_9(3~4),得到MCB的最优制备工艺条件为:环氧氯丙烷用量为3.0 mL,反应温度为45℃,反应时间为3.0 h,MCB对Cu~(2+)的吸附率可达63.70%。同时在单组分体系中研究了MCB对Cu~(2+)的吸附行为,结果表明:MCB对Cu~(2+)的最佳吸附pH值为5.0,MCB对Cu~(2+)的吸附遵循Langmuir等温吸附模型;动力学研究表明,MCB对Cu~(2+)的吸附过程符合拟二级吸附动力学方程。     

纤维素基磁性离子交换树脂

将含有Ｆｅ３Ｏ４或ｒ－Ｆｅ２Ｏ３粉末的黄原酸纤维素钠（粘胶）分散于高速搅拌下的油中，在８０～１００℃脱水成形，可得粒径＜１５０μｍ的磁性树脂。研究并论述了磁粉、油类、表面活性剂和搅拌速度等因素对树脂粒径及其分布的影响。     

磁性珠状纤维素亲和吸附剂的制备与应用

采用反相悬浮包埋技术制备了粒径小于300um、粒径分布窄和湿态孔度高(85%～90%)的高顺磁性珠状纤维素,经高碘酸钠活化后,与具有生物活性的绒毛膜促性腺激素偶联,得磁性亲和吸附剂(每克磁性珠状纤维素上固载300～400IU绒毛膜促性腺激素).     

纤维素基磁性聚偕胺肟树脂的研究——溴在树脂上的氧化还原反应

用羟胺作模拟物与溴反应，测定了吸溴前后的酸式纤维素基磁性聚偕胺肟树脂的红外光谱，结合Ｆｒｅｕｎｄｌｉｃｈ及Ｌａｎｇｍｕｉｒ等温吸附方程的分析和吸溴前后树脂重量变化的测定，证明纤维素基磁性聚偕胺肟树脂吸溴后随即发生氧化还原反应，偕胺肟基被氧化为羧基，溴则被还原为溴离子，在溴浓度较高时，纤维素葡萄糖单元上的羟基被溴代或被氧化成羰酸，若葡萄糖苷键氧化断裂，将导致大分子降解。     

发给素基磁性聚偕胺肟树脂的研究：溴在树脂上的吸附动力学

研究了酸式和碱式纤维基磁性聚偕胺肟树脂对溴的吸附行为。结果表明，吸附速度不但受控于粒内扩散，也受质量作用的影响。ＢＭＡＯ吸溴量溴浓度有关，符合Ｆｒｅｕｎｄｌｉｃｈ和Ｌａｎｇｍｕｉｒ等温吸附方程。     

纤维素基磁性聚偕胺肟树脂吸附锂

研究了氯化锂浓度、树脂含量和溶液的ＰＨ对碱式纤维素基磁性聚偕胺肟树脂吸附Ｌｉ＾＋离子能力的影响。在适当条件下，每个偕胺肟基可吸附两个Ｌｉ＾＋离子。     

纤维素基磁性聚偕肟树脂的研究：—（NH4）2IrCl6在树脂上的咐吸

碱式纤维系基磁性聚偕胺肟树脂（ＢＭＡＯ）吸附（ＮＨ４）ＩｒＣｌ６是快速过程，属超当量吸附。吸附结果生成ＡＯ－Ｉｒ和ＡＯ２－Ｉｒ３络合物，随后Ｉｒ（Ⅳ）被偕胺肟基还原为Ｉｒ（０），聚集成球状晶簇随着在树脂表面。     

球形纤维素基磁性阳离子的化学转化制备及机理研究

通过正交设计实验确定了用化学转化法制备球形纤维素基磁性阳离子交换树脂的最佳条件,即:将树脂在室温下浸渍于摩尔比为1∶2的Fe3 与Fe2 混合铁盐溶液中90min,然后,加入2mol/L的NaOH溶液,在搅拌下转化20min,Fe3 、Fe2 将转化为FeFe2O4并将均匀的分布在树脂的表面及大孔结构中,从而获取磁性树脂.并初步探讨了阳离子交换树脂磁化的机理.     

葡聚糖磁性毫微粒的制备

用共沉淀法制备出具有超顺磁性的葡聚糖磁性毫微粒，通过凝胶色谱法和调整离心法分离出葡聚糖磁性毫微粒，研究了制备过程中葡聚糖浓度、铁盐用量、氨水浓度、Ｆｅ＾３＿＋／Ｇｅ＾２＋摩尔比和二价钴对磁性葡聚糖毫微粒磁化离的影响。     

Molecular cluster batteries of nano-hybrid materials between Keggin POMs and SWNTs

Nano-hybrid materials of single-walled carbon nanotubes (SWNTs) and polyoxometalates (POMs) with three counter cations were prepared and used as cathode-active materials of molecular cluster batteries (MCBs). The charging/discharging performances and thus battery capacity of the MCBs with hybrid materials were significantly better than those of the microcrystal-POM MCBs.     

Reaction of Methylenecyclobutanes with NXS-H2O System

Reactions of methylenecyclobutanes (MCBs) with NXS-H₂O system were investigated. The results were quite different from that of methylenecyclopropanes (MCPs), and an interesting aryl-transfer reaction happened to give substituted cyclobutyl ketones as products when disubstituted MCBs were employed. When monosubstituted MCBs were employed, the direct halohydroxylation gave the cyclobutyl ring untouched adducts. All of these analogs have potential application value in organic synthesis.

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Aluminum chloride-mediated acylation of methylenecyclobutanes. A facile synthetic protocol for the construction of substituted cyclopentenes

Reactions of methylenecyclobutanes (MCBs) with acyl chlorides produce the corresponding substituted cyclopentene derivatives in moderate to high yields via ring enlargement in the presence of aluminum chloride under mild conditions. A plausible mechanism has been proposed on the basis of control and deuterium labeling experiments.     

Capacitance Effects Superimposed on Redox Processes in Molecular‐Cluster Batteries: A Synergic Route to High‐Capacity Energy Storage

Rechargeable molecular‐cluster batteries (MCBs) based on the manganese cluster complex [Mn₁₂O₁₂(CH₃CH₂C(CH₃)₂COO)₁₆(H₂O)₄] ([Mn12]) that exhibited a capacity of approximately 200 A h kg^?1 in the battery voltage range of 4.0 to 2.0 V were developed. In these batteries, the capacity of approximately 100 A h kg^?1 in the range of 4.0–3.0 V is caused by a chemical reduction from [Mn12]⁰ to [Mn12]^8?, whereas the other half in the range of 3.0–2.0 V cannot be explained by a redox change of the Mn ions. We performed the cyclic voltammetry (CV) and ⁷Li solid‐state NMR measurements on the Mn12‐MCBs to investigate the origin of the capacity below 3.0 V. Pseudo‐rectangular‐shaped CV curves in the range of 3.0–2.0 V demonstrate the presence of an electrical double‐layer (EDL) capacitance in Mn12‐MCBs, which corresponds to approximately 100 A h kg^?1. ⁷Li NMR studies suggest that Li ions form an EDL with electrons in carbon black electrodes in the capacitance voltage range. The capacitance effects are not formed by the single‐carbon electrodes alone, but appear only in the mixture of Mn12 and the carbon black electrodes. This type of coexistence of capacitance effects and redox reaction in one electrochemical cell is quite unusual and can serve as a new working principle for high‐performance energy‐storage devices.     

In‐situ XAFS Studies of Mn12 Molecular‐Cluster Batteries: Super‐Reduced Mn12 Clusters in Solid‐State Electrochemistry

In situ X‐ray absorption fine structure (XAFS) analyses were performed on rechargeable molecular cluster batteries (MCBs), which were formed by a lithium anode and cathode‐active material, [Mn₁₂O₁₂(CH₃CH₂C(CH₃)₂COO)₁₆(H₂O)₄] with tert‐pentyl carboxylate ligand (abbreviated as Mn12tPe), and with eight Mn³⁺ and four Mn⁴⁺ centers. This mixed valence cluster compound is used in an effort to develop a reusable in situ battery cell that is suitable for such long‐term performance tests. The Mn12tPe MCBs exhibit a large capacity of approximately 210 Ah kg⁻¹ in the voltage range V=4.0–2.0 V. The X‐ray absorption near‐edge structure (XANES) spectra exhibit a systematic change during the charging/discharging with an isosbestic point at 6555 eV, which strongly suggests that only either the Mn³⁺ or Mn⁴⁺ ions in the Mn12 skeleton are involved in this battery reaction. The averaged manganese valence, determined from the absorption‐edge energy, decreased monotonically from 3.3 to 2.5 in the first half of the discharging (4.0>V>2.8 V), but changed little in the second half (2.8>V>2.0 V). The former valence change indicates a reduction of the initial [Mn12]⁰ state by approximately ten electrons, which corresponds well with the half value of the observed capacity. Therefore, the large capacity of the Mn12 MCBs can be understood as being due to a combination of the redox change of the manganese ions and presumably a capacitance effect. The extended X‐ray absorption fine structure (EXAFS) indicates a gradual increase of the Mn²⁺ sites in the first half of the discharging, which is consistent with the XANES spectra. It can be concluded that the Mn12tPe MCBs would include a solid‐state electrochemical reaction, mainly between the neutral state [Mn12]⁰ and the super‐reduced state [Mn12]⁸⁻ that is obtained by a local reduction of the eight Mn³⁺ ions in Mn12 toward Mn²⁺ ions.     

A Simple Method to Prepare Magnetic Modified Corncobs and its Application for Congo Red Adsorption

The purpose of this research is to use a simple method to prepare magnetic modified corncobs (MCBs) with good adsorption performances for Congo Red (CR). The adsorption was analyzed by Fourier transform infrared spectroscopy and x-ray diffraction. The maximal adsorption capacity of the MCB for CR was 198.2 mg/g and about 5.5-fold for unmodified corncob. Potassium ion was more positive effect onto adsorption than sodium ion. The dye uptake process obeyed the pseudo-second-order kinetic expression. The best-fitted data were obtained with the Langmuir model. The as-prepared magnetic modified sorbent had a potential in the dyeing industry wastewater treatment.     

Permo-Triassic Magnetostratigraphy in Wulong Area, Sichuan, China

The Permo-Triassic boundary in Wulong area, Sichuan Province, South China lies in a continuous marine carbonate succession with abundant fossil records. Two well-exposed sections were sampled for magnetostratigraphic studies. The experimental results of rock magnetism reveal that the samples from the Triassic limestones contain only magnetites among which 70% are multi-domain. The ChRM direction is carried by remaining 30% of single-domain magnetite. The Permian limestone samples are dominated by single-domain to superparamagnetic magnetites with little ChRM direction due to their fine-grained texture. Nevertheless, the polarity determination is still possible based on the NRM vector changes during thermal demagnetization. A Permo-Triassic polarity profile in Wulong area is established in the paper, and a tentative correlation with other known profiles is pursued. The authors suggest that the Illawarra reversal starts at the upper part of Wujiapingian, while some normal polarity events may exist in the     

Mössbauer and X-ray study of natural magnetite sands

Black sands originating from north, west and south seaside strips of the Bay of Burgas, Black Sea, were investigated. It was found that these sands are martitized magnetites. Their composition involves mixtures of nonstoichiometric magnetite and maghemite or stoichiometric magnetite and hematite.     

Influence of Surface Coating on Fluoride Removal by Magnetite

Al(OH)₃- and ZrO(OH)₂-coated magnetites were prepared and used for fluoride removal from aqueous samples. The influence of pH, sorbent mass, and ions such as chloride, sulfate, and phosphate on the removal of fluoride was characterized. The sorption process was highly pH dependent, and the optimal sorption was obtained from pH 4 to 5 for ZrO(OH)₂- and pH 4 to 7 for Al(OH)₃-coated magnetites. The sorption isotherm was well described by the Langmuir equation for the sorbents. The maximum adsorption capacity of ZrO(OH)₂-coated magnetite (57.47?mg-F?g^?1-sorbent) was higher than for Al(OH)₃-coated magnetite (23.87?mg-F?g^?1-sorbent). The ion-exchange reaction occurred in 5?min and more than 99% of fluoride was removed from solution. When the ZrO(OH)₂-coated magnetite was used, the presence of foreign ions negatively affected the fluoride removal. The prepared sorbents showed an excellent performance for the removal of fluoride in water samples.