Adsorption of Cr(VI) by modified chitosan from heavy-metal polluted water of Xiangjiang River, China

Methacrylic acid was used together with a molecular imprinting technique to modify chitosan. In addition, the adsorption kinetics and adsorption isotherms were recorded and the results were analyzed to investigate reparative adsorption for Cr（VI） from the polluted Xiangjiang River water. A comparative X-ray analysis shows that the degree of crystallization in the imprinted polymer was significantly weakened, the area of the non-crystalline region was larger. There were more adsorption sites in the imprinted polymer, and the adsorption capacity towards Cr（VI） was increased. The adsorption capacity of the imprinted polymer towards Cr（VI） increased with time and reaches saturation after 8 h. The optimal adsorption time was 4-8 h after the adsorption starting and the optimal pH value for the solution was in the range of 4.5-7.5. When the chitosan reaches saturation, the adsorption capacity achieves a state of equilibrium, and the maximum Cr（VI） extraction rate reaches 33.7%. Moreover, the adsorption capacity of the imprinted polymer towards Cr（VI） increases with increasing chitosan concentration. In this situation, the Cr（VI） extraction rate shows little variation, and the maximum removal rate can reach 98.3%. Furthermore, the Cr（VI） extraction rate increases with an increase in the degree of deacetylation in the chatoyant and chitosan, with the best adsorption effect corresponding to 90% deacetylation. Fitting the adsorption data to the quasi first- and second-order kinetic models yields correlation coefficients of 0.9013 and 0.9875, respectively. The corresponding rate constants for the two models are 0.0091 min-1 and 7.129 g/（mg.min）, respectively. Hence, the adsorption using Cr（VI）-imprinted chitosan is more consistent with the second-order kinetics. Comparing the data to Freundlich and Langrnuir adsorption isotherms shows that the latter has a better linear fit and a maximum adsorption capacity of 15.784 mg/g.

Chemically Modified Chitosan Beads as Molecularly Imprinted Polymer Matrix for Adsorptive Separation of Proteins

In a phosphate buffer, a hemoglobin (Hb)-imprinted polymer complex was prepared using maleic anhydride (MAH) modified chitosan beads as matrix, acrylamide (AM) as functional monomer, N,N-methylenebisacrylamide (MBA) as cross-linker and potassiumpersulfate (KPS) / sodium hydrogen sulfite (NaHSO3) as initiators. Langmuir analysis showed that an equal class of adsorption was formed in the molecular imprinting polymer (MIP), and the MIP has high adsorption capacity and selectivity for the imprinted molecule. The MIP can be reused and the recovery was approximately 100% at low concentration.

A Multiwall Carbon Nanotube-chitosan Modified Electrode for Selective Detection of Dopamine in the Presence of Ascorbic Acid

A novel multiwall carbon nanotube-chitosan modified electrode has been prepared.The modified electrode resolves the overlapping voltammetric response of dopamine and ascorbicacid into two well-defined peak by 212 mV. The mechanism of discrimination of dopamine fromascorbic acid is discussed. Dopamine can be determined selectively with the carbonnanotube-chitosan modified electrode. The electrode shows good sensitivity, selectivity andstability.

Adsorption of Anionic Dyes onto Chitosan-modified Diatomite

The purpose of this work is to study the possibility of anionic dyes Reactive Red M-8B（RR） and Direct Green B（DG） adsorbed on chitosan-modified diatomite. The characteristics of adsorbent, adsorption isotherms and the influence of adsorption time, temperature and pH were researched in this work. The results show that the mo- dified diatomite had a much better adsorption capability than the natural diatomite. The adsorption capacities of chitosan-modified diatomite for RR and DG were 94.46 and 137.0 mg/g, respectively. Both adsorption time and adsorption temperature provided a positive effect on the dye adsorption. Within the experimental pH range, the adsorbance was enhanced at lower pH but reduced sharply at high pH. On the basis of the experimental results and discussion, electrostatic attraction is considered as the main mechanism of this chemisorption.

Preparation and Performance of Chitosan/Citric Acid Modified Magnesium Oxychloride Cement

Citric acid(CA)and chitosan(CS)were employed to modify magnesium oxychloride cement(MOC).Multiscale measurements were implemented to study the properties of the modified MOC pastes.Results show that the addition of CA/CS significantly changes the content of each phase and the microstructure of phase 5.The single addition of CA can effectively increase the compressive strength of MOC after 7 d curing,while CS exerts no obvious effect on the compressive strength.As to the simultaneous addition of CA and CS,the compressive strength of MOC gradually decreases with the increasing content of CS.Interestingly,mixing CA and CS significantly enhances the water resistance of MOC and decreases the degradation rate of MOC in phosphate buffered solution,which can be ascribed to the low specific surface area of the plate-like crystals in the modified MOC and the reduction of pores in the structure.

Synthesis and Characterization of Chitosan-based Biomateriais Modified with Different Active Groups and Their Relationship with Cytotoxicity

The cytotoxicity profile of three chitosan derivatives with different affinity to water was evaluated in vitro. The derivatives selected were carboxymethylated-chitosan （CMCH）, linoleic acid modifiedchitosan （LACH） and deoxycholic acid modified-chitosan （DACH）, respectively, and the results of FTIR and NMR confirmed the successful modification. Cytotoxicity of these polymers was investigated via the red blood cell lysis assay and the MTT assay. The red blood cell lysis test showed that CH elicited a certain level of red blood cell toxicity, while CMCH, LACH and DACH all displayed low membrane damaging effects, with the hemolysis rates of 2.385%, 1.560% and 4.404%, respectively, which comes well within permissible limit （5%）. The MTT assay revealed that CH exhibited significant inhibitory effect on fibroblast proliferation at higher concentration, while its three derivatives showed no cytotoxicity. CMCH had stimulatory effects on fetal mouse fibroblast proliferation. Differences in cytotoxicity of CH and its derivatives may result from the specific chemical modifications leading to the alteration of molecular charge density and type of the cationic functionalities, structure and sequence, and conformational flexibility.

A Glassy Carbon Electrode Modified with Cellulose Nanofibrils from Ammophila arenaria for the Sensitive Detection of L-Trytophan

L-tryptophan is an essential amino acid for human health. Nanofibrillated cellulose (NFC) from marram grass (Ammophila arenaria) extracted from plants harvested in the center of Tunisia was used for the first time for the modification of a glassy carbon electrode (GCE), for the sensitive detection of L-tryptophan (Trp). After spectroscopic and morphological characterization of the extracted NFC, the GC electrode modification was monitored through cyclic voltammetry. The NFC-modified electrode exhibited good analytical performance in detecting Trp with a wide linear range between 7.5 × 10−4 mM and 10−2 mM, a detection limit of 0.2 µM, and a high sensitivity of 140.0 µA∙mM−1. Additionally, the NFC/GCE showed a good reproducibility, good selectivity versus other amino acids, uric acid, ascorbic acid, and good applicability to the detection of Trp in urine samples.

MCTS试件的三维有限元计算断裂分析

为了探讨三维复合型断裂问题,采用ANSYS软件对一种带有倾斜裂纹面的修正紧凑拉剪(MCTS)试件进行了三维断裂有限元分析,并应用修正的虚拟裂纹闭合积分方法(MVCCI),对三维裂纹试件的应力强度因子进行了计算.研究结果表明:该MCTS试件在I型I、I型及I+II复合型(加载角为45°)加载条件下均产生了Ⅰ+Ⅱ+Ⅲ复合型断裂,实验结果与有限元分析的结果吻合.

Preparation and Blood Compatibility of Oxidized-chitosan Films

Chitosan membrane was modified by the selective oxidization of chitosan molecules on its surface with NO2 gas. FTIR spectra indicated there were plenty of –COOH and –COO- groups on the modified membrane surface. The SEM study showed the modified membrane surface was rough rather than smooth as chitosan membrane. All antithrombosis test, hemolysis test and blood cell morphology observation with SEM revealed that modified chitosan membranes have superior blood compatibility to chitosan.

Mechanical Properties of Collagen Biomimetic Films Formed in the Presence of Calcium,Silica and Chitosan

Using eucollagen solutions from ox hide, we cast collagen films to assess the influence of calcium and silica on the reconstitution of the fibrous structure of collagen. The tensile strength and the breaking elongation of the reconstituted collagen films were measured and analysed. Significant differences were observed between reconstituted collagen films with and without calcium and silica. The breaking elongation of the films obtained in the presence of silica was significantly greater, and the degradation was lower than other films of reconstituted collagen. Collagen and chitosan do not exist together as blends in nature, but the specific properties of each may be used to produce in biomimetic way man-made blends with biomedical applications, that confer unique structural, mechanical （detail） and in vivo properties.

Direct Electrochemistry with Nitrate Reductase in Chitosan Films

Stable films made from chitosan (CS) on pyrolytic graphite electrode (PGE) gave direct electrochemistry for incorporated enzyme nitrate reductase (NR). Cyclic voltammetry of CS / NR films showed a pair of well-defined and nearly reversible redox peaks at about -0.430 V vs. SCE at pH 7.0 phosphate buffers.

Influence of Cathode Modification by Chitosan and Fe^(3+)on the Electrochemical Performance of Marine Sediment Microbial Fuel Cell

The electrochemical performances of cathode play a key role in the marine sediment microbial fuel cells(MSMFCs)as a long lasting power source to drive instruments,especially when the dissolved oxygen concentration is very low in seawater.A CTS-Fe^(3+)modified cathode is prepared here by grafting chitosan(CTS)on a carbon fiber surface and then chelating Fe^(3+)through the coordination process.The electrochemical performance in seawater and the output power of the assembled MSMFCs are both studied.The results show that the exchange current densities of CTS and the CTS-Fe^(3+)group are 5.5 and 6.2 times higher than that of the blank group,respectively.The potential of the CTS-Fe^(3+)modified cathode increases by 138 mV.The output power of the fuel cell(613.0 mW m^(-2))assembled with CTS-Fe^(3+)is 54 times larger than that of the blank group(11.4 mW m^(-2))and the current output corresponding with the maximum power output also increases by 56 times.Due to the valence conversion between Fe^(3+)and Fe^(2+)on the modified cathode,the kinetic activity of the dissolved oxygen reduction is accelerated and the depolarization capability of the cathode is enhanced,resulting higher cell power.On the basis of this study,the new cathode materials will be encouraged to design with the complex of iron ion in natural seawater as the catalysis for oxygen reduction to improve the cell power in deep sea.

生物基化学纤维的研究、应用及发展方向

生物基化学纤维是指利用生物体内存在的或者代谢产生的一些高分子物质,结合高分子物理化学技术,开发出的性能良好的生物基再生纤维和生物基合成纤维。它们具有原料来源广泛,制品无污染和可降解等特性。概述各种生物基化学纤维的研究、应用及发展方向,总结目前研究较多的聚乳酸纤维、莱赛尔纤维、壳聚糖纤维、海藻纤维以及蛋白改性纤维等的性能特点及应用领域,以期为生物基化学纤维的进一步研发提供参考。

改性鸡肺、牛肺、猪肺明胶/羧甲基壳聚糖复合水凝胶的制备及性能

为提高畜禽养殖效益、实现高附加值的畜禽肺资源化利用,本研究以鸡肺、牛肺、猪肺及与羧甲基壳聚糖为原料,在鸡肺、牛肺、猪肺明胶制备及改性的基础上,将羧甲基壳聚糖分别与改性鸡肺、牛肺、猪肺明胶按1∶1、1∶2和2∶1体积比进行交联反应制备复合水凝胶,并进一步对复合水凝胶的关联度、凝胶强度、红外光谱、溶胀性、热变特征、微观结构及失水率等理化性质进行分析。结果表明,当羧甲基壳聚糖分别与改性鸡肺、牛肺、猪肺明胶按1∶2体积比时,配制得到的复合水凝胶性质最好。其中,羧甲基壳聚糖与改性牛肺明胶按1∶2体积比配制得到的复合水凝胶交联度、凝胶强度、孔隙率和失水率分别为45.4%、5.24 N、64.58%和87.6%,优于羧甲基壳聚糖分别与改性鸡肺明胶、改性猪肺明胶按1∶2体积比配制得到的复合水凝胶。本研究结果为畜禽肺的高附加值资源化利用提供了新思路。

自愈合壳聚糖抗菌水凝胶的制备及其性能研究

水凝胶作为生物医药领域的新型材料,因其具有特殊的性能被人们广泛研究。研究利用丙烯酸对壳聚糖进行修饰得到可溶性N-羧乙基壳聚糖CEC-NA,与本实验室自制的POSS-PEG-CHO在水溶液中通过席夫碱反应制备力学性能好、自愈合的CS-POSS-PEG水凝胶。对CEC-NA及CS-POSS-PEG水凝胶进行结构表征,并对水凝胶内部微观形貌、自愈合性、力学性能、溶胀性能、细胞相容性以及抗菌能力等一系列性质进行研究,结果表明水凝胶具有疏松多孔结构、良好的自愈合性、力学性能、溶胀性能、细胞相容性和抗菌性,在伤口敷料的方面具有潜在的应用前景。

改性壳聚糖对Ni(Ⅱ)的吸附性能研究

为研究改性壳聚糖对水中Ni(Ⅱ)的吸附性能,以三聚磷酸钠为交联剂,对经过乙酸-双氧水体系氧化后的壳聚糖进行一步离子交联,制备改性壳聚糖吸附材料。通过扫描电子显微镜、傅里叶变换红外光谱仪、X射线衍射仪等对材料的微观形貌、分子结构及物相进行表征;采用条件实验探究改性壳聚糖吸附性能的影响因素,并对其吸附热力学进行分析。结果显示:改性后的壳聚糖呈纳米片状结构,成功实现了三聚磷酸钠中P—O与壳聚糖中—NH_(2)之间的交联;在三聚磷酸钠浓度为10 g/L、双氧水用量为5 mL、交联温度为40℃条件下制备的改性壳聚糖表现出较好的吸附性能,当pH为7、吸附时间为120 min、三聚磷酸钠改性壳聚糖投加量为50 mg时,其对Ni(Ⅱ)的去除率达到8371%;改性壳聚糖对Ni(Ⅱ)的吸附行为符合Langmuir等温吸附模型,吸附过程为自发吸热过程。

铬离子污染快速可视化检测方法研究

开发了一种基于壳聚糖的酰基化改性、利用含巯基碳量子点(S,N-CQDs)与点击反应制备的荧光修饰的改性壳聚糖(NMCS-SNCQDs)的简易方法,并对NMCS-SNCQDs进行了表征。结果表明:该方法具有成本低、便捷快速、可视化等特点;NMCS-SNCQDs保留了S,N-CQDs的良好荧光性能,可对Cr^(6+)有选择性地进行荧光淬灭响应,其临界响应浓度为52μmol/L;NMCS-SNCQDs具有很好的成凝胶性,可用于开发荧光试纸/凝胶,实现快速、实时检测水体中的Cr^(6+)污染。

改性壳聚糖基吸附材料的合成与应用

壳聚糖是一种天然高分子生物基材料,其分子链中含有反应性基团-NH_(2)、-OH,能与重金属离子形成配位化合物,表现出良好的吸附性能。本研究以壳聚糖为基础原料,利用氯乙酸和领苯二酚基团为改性试剂,通过两步法操作,合成出改性壳聚糖基吸附材料,同时对改性壳聚糖基吸附材料的溶解性和吸附性能进行详细地研究。结果表明:改性壳聚糖基吸附材料溶解性明显提高,具有更宽的应用范围;在25℃,pH=6,重金属离子初始浓度为50 mg/L,改性壳聚糖基吸附材料用量50 mg,反应时间60 min,改性壳聚糖基吸附材料对重金属离子Cd^(2+)、Cu^(2+)、Pb^(2+)等去除率可达90%以上。

改性壳聚糖/贝壳粉复合物对含重金属废水的吸附作用研究

介绍了重金属的污染危害性,分析了改性壳聚糖/贝壳粉复合物吸附工业废水重金属离子实验,研究了改性壳聚糖/贝壳粉复合物吸附性能,对工业废水处理有一定的参考价值。

壳聚糖的化学改性及其吸附性能的研究

以脱乙酰度90%的壳聚糖(CTS)与硫氰酸铵和氯乙酸反应,合成了一种带有硫脲基和羧基双官能团的水溶性中间产物,再经戊二醛交联,制备了水不溶性的可用于处理含重金属废水的颗粒状树脂.用FTIR,SEM及比表面法对中间产物及颗粒状树脂进行了表征,表明—HN—C(S)—NH—CH2—COOH基团接枝到CTS链上并进行了交联.吸附实验表明,该化合物对Cu2+的吸附量(248mmol·g-1)比Ni2+(135mmol·g-1)高得多,这可能与离子的核电荷数和螯合体的配位相关.在两种金属离子的混合液中,该化合物对Cu2+的初始吸附选择性更强.吸附金属离子的树脂经3次盐酸洗脱再生后,吸附性能几乎没有下降.