壳聚糖-Fe(Ⅲ)复合凝胶球去除磷酸根的影响因素与吸附机理

为改善当前环境水体中的磷污染现状,利用溶胶-滴定-真空冷冻干燥法制备了壳聚糖-铁(CS-Fe)复合凝胶球去除水中磷酸根.对CS-Fe凝胶球的形貌结构进行了表征,研究了材料对磷酸根的吸附影响因素,并探索了反应机理.结果表明,CS-Fe对磷酸根的吸附为自发、吸热、熵增过程;吸附过程符合拟一级动力学方程,吸附平衡时间为50 ...     

一种磷酸根-羧甲基葡甘聚糖锆凝胶球的吸附性能

用氧氯化锆溶液交联羧甲基葡甘聚糖制得新型吸附材料—羧甲基葡甘聚糖锆凝胶球。探究了凝胶球对磷酸根的吸附性能,考察了羧甲基葡甘聚糖浓度、氧氯化锆浓度、吸附时间、pH值、温度和磷酸根浓度对吸附的影响。结果表明:298K时,凝胶球对磷酸根的吸附9h达平衡,当CMKGM和氧氯化锆浓度均为2.0%,磷酸根初始浓度为600mg·L-1,pH为2.5时,吸附量为186.65mg/g。利用Langmuir方程拟合实验数据,发现该方程适合于所研究的吸附体系。该体系为吸热体系,升温有利于吸附。     

改性高粱秸秆对磷酸根的吸附性能研究

将改性高粱秸秆用于磷酸根的吸附,研究了时间、酸度、温度以及改性高粱秸秆用量等因素对其吸附性能的影响。结果表明,在常温下,改性高粱秸秆对磷酸根具有良好的吸附性能,吸附时间快。改性高粱秸秆对磷酸根的吸附符合Langmuir和Freundli-ch吸附等温方程及准二级动力学方程,吸附过程以单分子层物理吸附为主。     

羧甲基纤维素-壳聚糖水凝胶球的制备及性能

采用物理交联法制备了羧甲基纤维素(CMC)-壳聚糖(CS)共混水凝胶球;研究了共混球的耐酸碱性、溶胀性及对亚甲基蓝的吸附性能.结果表明,水凝胶球在弱酸和弱碱中具有一定的稳定性;随着羧甲基纤维素与壳聚糖质量比的增大,水凝胶的吸水溶胀率增加.在CMC与CS质量比为1∶4时制备的水凝胶呈规则球状.     

壳聚糖水凝胶微球的制备与溶胀性能

采用三聚磷酸钠(TPP)和六偏磷酸钠(SHMP)为复合交联剂,制备了离子交联网络结构的壳聚糖水凝胶微球。分析讨论了交联剂质量配比、pH以及离子强度等对壳聚糖微球溶胀性能的影响。结果表明:使用复合交联剂制备的微球的溶胀度比单独使用TPP或SHMP的分别低62.4%和41.3%,交联效率得到明显提高;当m(TPP)∶m(SHMP)=3∶5,交联剂pH=5时,制备的微球交联程度最好,结构最密实;在pH=1.2的缓冲溶液中,溶胀度可达到357%,而且凝胶没有任何破碎。微球具有较好的离子强度和pH敏感性,在酸性介质中有较高的溶胀度。     

磁性壳聚糖微球的制备及对Cr(Ⅵ)的吸附性能研究

用壳聚糖包埋磁流体,用戊二醛交联制成磁性壳聚糖微球,并用红外光谱表征其结构。用制备的磁性壳聚糖微球吸附Cr(Ⅵ)离子,考察了其对Cr(Ⅵ)离子的吸附性能;探讨了吸附时间、溶液pH值、吸附剂用量、温度、Cr(Ⅵ)起始浓度以及其他离子存在对Cr(Ⅵ)离子去除率的影响。实验结果表明,磁性壳聚糖微球吸附Cr(Ⅵ)离子的最佳条件为:吸附平衡时间40 min,最佳吸附pH值6左右,磁性壳聚糖微球用量10 mg,温度升高有利于提高磁性壳聚糖微球的吸附效率,Cr(Ⅵ)离子起始质量浓度为12μg/mL,无机盐的存在引起磁性壳聚糖微球的吸附性能降低。并且考察了吸附剂的再生性能,实验结果表明磁性壳聚糖微球具有良好的重复使用性。     

磁性壳聚糖硅胶复合微球的制备及其吸附Cu~(2+)的性能研究

以壳聚糖与正硅酸四乙酯为原料,采用溶胶-凝胶法,用戊二醛辅助交联合成了磁性壳聚糖硅胶复合微球。通过红外光谱、扫描电镜、X-射线衍射等方法对磁性壳聚糖硅胶复合微球的形态和组成特性进行分析,制备的磁性复合微球中壳聚糖与硅胶材料复合均匀,材料粒径均一,机械强度较高。考察了制备的磁性壳聚糖硅胶复合微球对Cu~(2+)的吸附性能,结果表明微球对Cu~(2+)具有较好的吸附性能,吸附容量达到98.7mg/g。     

壳聚糖-叶酸复合凝胶的制备及Pb2+吸附性能研究

叶酸(FA)通过离子交联壳聚糖构筑了壳聚糖-叶酸水凝胶(CS-FA-HG),利用红外光谱、紫外-可见光谱、电子扫描显微镜等对其结构进行表征,并考察了CS-FA-HG对Pb²⁺的吸附性能。实验结果表明,FA、壳聚糖醋酸盐(CS-Ac)浓度均为35 mg/mL,Na₂CO₃溶液的质量分数为5.0%时,FA钠盐通过静电作用离子交联CS-Ac,形成CS-FA-HG,微观呈枝状纤维结构;在pH 5.0,吸附温度30℃的条件下,80 mg干CS-FA-HG在50 mL初始浓度15 mg/L的Pb²⁺溶液中,对Pb²⁺的吸附量为8.14 mg/g;吸附符合二级动力学方程和Langmuir吸附等温式。CS-FA-HG制备方法简单,绿色环保,无二次污染,在重金属离子吸附方面有潜在应用。     

锐钛矿光催化降解苯酚:氟离子吸附的影响大于磷酸根

已知氟离子和磷酸根能加快锐钛矿和P25TiO2光催化降解苯酚等有机物,但作用机理仍存在争议.合成了不含无机阴离子的锐钛矿,并在其表面沉积0.52wt%Pt(Pt/TiO2).在初始pH5.2的水溶液中,99%的氟离子和磷酸根分别为F^-和H2PO4^-.加入0.1~30mmol/L阴离子,苯酚的光催化降解速率常数(kobs)都增大,证实了氟离子和磷酸根均具有正效应.有趣的是,kobs增加倍数均与阴离子吸附量呈线性关系,其中氟离子的斜率大于磷酸根,而Pt/TiO2的斜率大于TiO2.这表明阴离子的正效应源于吸附于固体表面的阴离子,并且氟离子的活性大于磷酸根.(光)电化学测试表明,氟离子和磷酸根分别抑制和促进O2还原,但它们都促进苯酚氧化.此外,氟离子和磷酸根分别使TiO2平带电位移动-159mV和89mV.前者有利于TiO2价带与苯酚发生轨道重叠,后者有利于TiO2导带分别与O2发生轨道重叠,进而加快界面电荷转移.由于阴离子广泛存在,该结果将有助于半导体光催化的机理研究及其环境应用.     

壳聚糖共混微球的制备及吸附性能测试

壳聚糖（CS）分子中含有游离态的氨基和羟基,是一种高效的离子吸附剂,而且氨基可质子化形成阳离子,使得壳聚糖对阴离子及两性化合物都具有较强的吸附能力.壳聚糖引入羧甲基后水溶性和反应活性大大增强.实验中以乳化-化学交联法制备壳聚糖/羧甲基壳聚糖（CMC）四种共混微球,通过对比,发现当CS与CMC的质量比为4∶1、2∶3时,成球硬度好,形状明显,大小均匀.随着CMC含量的增加,所成微球对牛血清白蛋白（BSA）的吸附能力逐渐增强.因此,当CS与CMC质量比为2∶3时共混微球自身的物理形态与吸附性能均达到良好状态,是共混高效离子吸附剂的最佳比例选择.     

Adsorption of Chromium on Composite Microspheres of Chitosan and Nano Iron Oxide

The batch removal of Cr(VI) ions from aqueous solution using binary composite microspheres of chitosan and nanoparticles of iron oxide under different conditions has been investigated in this study. The influences of initial chromium concentration, contact time, pH, temperature, and solid-liquid ratio have been reported. The adsorption data was fitted well in the Langmuir and Freundlich models and various static parameters were calculated. The mechanism of adsorption was studied by Fourier Transform Infrared spectroscopy (FTIR).     

Examination of the Higuchi Model for the Release of Vitamin B2 from Multilayered Calcium Alginate/Chitosan Beads in Varying pH Medium

The release of model drug vitamin B₂ from calcium alginate/chitosan multi‐layered beads has been studied in the media of varying pH (3 h in the medium of pH 1.0 and for the remaining time in pH 7.4) at 37°C. The quantitative deviation of experimental data from the Higuchi model has been interpretated by using a newly developed ‘curve area measurement’ (CAM) approach. The higher deviation in the initial phase has been explained on the basis of porous structure of beads due to the use of low molecular weight polymers in the preparation of beads.     

Adsorption of anionic dye by anionic surfactant modified chitosan beads: Influence of hydrophobic tail and ionic head-group

In this paper, how chitosan hydrogel beads were modified by anionic surfactants (SDS, SDOS, SDBS, AOT, and DTM-12) and then used for the adsorption and removal of an anionic dye (congo red) from aqueous solutions were described. The effect of surfactant concentration, surfactant ionic head-group, and surfactant hydrophobic tail were investigated in detail. The result revealed the modified CS beads all had the obviously higher adsorption capacity than CS beads. Compared to the ionic head-group, the hydrophobic tail of the surfactant plays more important role in the adsorption, and a high adsorption capacity was observed for CS/AOT beads and CS/DTM-12 beads (both with two hydrophobic tails). The Sips isotherm model showed a good fit with the equilibrium experimental data, and the values of the heterogeneity factor (n) indicated heterogeneous adsorption. The adsorption kinetics analysis indicated that the pseudo-second-order rate model could better describe the adsorption process than the pseudo-first-order rate model.     

Synthesis and characterization of chitosan‐modified polymethyl methacrylate latex particles

Stable chitosan‐modified polymethyl methacrylate (PMMA) latex particles were prepared by using 2,2′‐azobis(2‐amidinopropane) dihydrochloride (V‐50) as the cationic initiator. The polymerization rate (R_p) is controlled by the V‐50 concentration ([V‐50]) and R_p is less sensitive to the chitosan concentration ([C]) used in the synthesis work. The reaction system follows Smith–Ewart Case III kinetics due to the relatively large particles produced. The zeta potential data show that the isoelectric point (pI) of the latex particles is 10.7. The amounts of V‐50 (C_V‐50) and chitosan (C_c) ultimately incorporated into the particles correlate reasonably well with [V‐50] and [C], respectively. At pH 7, the quantity of the negatively charged bovine serum albumin (BSA, pI = 4.8) adsorbed on the positively charged chitosan‐free particles (Q) via the electrostatic interaction increases with increasing C_V‐50. However, Q is relatively insensitive to changes in C_c. This result implies that only the outermost region of the hairy chitosan‐modified particles is available for adsorption of the relatively large protein species. Colloidal stability shows a significant influence on the BSA adsorption process. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1489–1499, 1999     

Removal of Congo red dye by gemini surfactant C12-4-C12 · 2Br-modified chitosan hydrogel beads

In this paper, chitosan hydrogel beads were modified with gemini surfactant C₁₂-4-C₁₂ · 2Br and then used for the adsorption and removal of Congo red dye. The effects of pH, inorganic salt, temperature, shaking rate, and surfactant concentration were investigated in detail. The gemini surfactant concentration was the main factor, and the maximum adsorption amount was observed at 0.5% C₁₂-4-C₁₂ · 2Br. The Sips isotherm model fit well with the equilibrium experimental data, and the values of the heterogeneity factor (n) indicated heterogeneous adsorption. The adsorption kinetics was found to follow the pseudo-second-order rate model better than the pseudo-first-order rate model.     

Biomimetic Ion Nanochannels as a Highly Selective Sequential Sensor for Zinc Ions Followed by Phosphate Anions

A novel biomimetic ion‐responsive multi‐nanochannel system is constructed by covalently immobilizing a metal‐chelating ligand, 2,2′‐dipicolylamine (DPA), in polyporous nanochannels prepared in a polymeric membrane. The DPA‐modified multi‐nanochannels show specific recognition of zinc ions over other common metal ions, and the zinc‐ion‐chelated nanochannels can be used as secondary sensors for HPO₄^2? anions. The immobilized DPA molecules act as specific‐receptor binding sites for zinc ions, which leads to the highly selective zinc‐ion response through monitoring of ionic current signatures. The chelated zinc ions can be used as secondary recognition elements for the capture of HPO₄^2? anions, thereby fabricating a sensing nanodevice for HPO₄^2? anions. The success of the DPA immobilization and ion‐responsive events is confirmed by measurement of the X‐ray photoelectron spectroscopy (XPS), contact angle (CA), and current–voltage (I–V) characteristics of the systems. The proposed nanochannel sensing devices display remarkable specificity, high sensitivity, and wide dynamic range. In addition, control experiments performed in complex matrices suggest that this sensing system has great potential applications in chemical sensing, biotechnology, and many other fields.     

Desorption Potentials of Alkyl Alcohols and Specific Adsorption of Anions

Abstract

The potentials of desorption of various alkyl alcohols have been studied as a function of concentration of alcohol and of the nature and concentration of various electrolytes. Specific adsorption of the electrolyte ions is reflected in shifts of the desorption peaks of the alcohols. At anodic potentials, the order of specific adsorption appears to be chloride > sulfate >perchlorate > fluoride, and at cathodic potentials (vs. S. C. E.), chloride > perchlorate > sulfate > fluoride.     

Effect of pH on Competitive Adsorption of Cu(II), Ni(II), and Zn(II) from Water onto Chitosan Beads

The amounts of adsorption of Cu²⁺, Ni²⁺, and Zn²⁺ from single, binary, and tertiary nitrate solutions onto glutaraldehyde cross-linked chitosan beads were measured. The beads had an average particle size and pore volume of 2 mm and 0.06 cm³/g, respectively, and had a BET surface area of 60 m²/g. All experiments were performed at 298 K as a function of initial pH (2.0–5.0), total metal concentration (0.77–17.0 mol/m³), and molar concentration ratio (0.25–4) in the aqueous phase. It was shown that the amount of metal adsorption generally increased with increasing solution pH. Competitive adsorption was significant in binary and tertiary systems when Cu²⁺ was present. The selectivity factor reached maximum in an equilibrium pH range of 5.1–5.3 and 4.5–4.9 for the Cu-Ni and Cu-Zn binary systems, respectively. This adsorbent provided a possibility for selective separation of Cu²⁺ from such multi-component solutions.     

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 preparedusing maleic anhydride (MAH) modified chitosan beads as matrix, acrylamide (AM) as functionalmonomer, N,N-methylenebisacrylamide (MBA) as cross-linker and potassiumpersulfate (KPS) /sodium hydrogen sulfite (NaHSO3) as initiators. Langmuir analysis showed that an equal class ofadsorption was formed in the molecular imprinting polymer (MIP), and the MIP has highadsorption capacity and selectivity for the imprinted molecule. The MIP can be reused and therecovery was approximately 100% at low concentration.