壳聚糖镍配合物对尿素吸附性能研究

合成了壳聚糖和金属元素Ni的配合物,通过红外光谱（IR）和紫外吸收光谱做了表征,并研究了壳聚糖-Ni对尿素的吸附性能,探讨了尿素初始质量浓度、反应pH、温度及时间对吸附量的影响。结果发现,壳聚糖-Ni配合物对尿素具有很好的吸附能力,当尿素溶液的初始浓度为3.5mg/mL,反应温度为20℃,pH为6.0,反应时间为10h时,壳聚糖-Ni对尿素的吸附性能最好。      

正交试验优化酵母多糖锌配合物的制备及其对尿素的吸附性能

为酵母多糖应用拓宽范围,以酵母多糖和硫酸锌为原料制备酵母多糖锌配合物,探讨了反应时间、锌的添加量、反应温度、pH值4个因素对配合物制备的影响。通过正交试验,确定制备锌配合物的最优条件。以尿素为吸附对象,研究酵母多糖锌配合物的吸附性能,考察了时间、温度、pH值、尿素质量浓度4个因素对配合物吸附尿素的影响,通过正交试验,确定酵母多糖锌配合物吸附尿素的最优条件。结果表明:酵母多糖锌配合物制备的最佳条件为温度55℃、反应时间2h、0.1mol/L硫酸锌的添加量10%、pH6.5,在该条件下所得到的酵母多糖和锌离子结合率为98.97%。酵母多糖锌配合物对尿素的最佳吸附条件为:温度30℃、pH6.0、时间135min、尿素的初始质量浓度2.25mg/mL,在该条件下对尿素的吸附率为97.27%。此时酵母多糖和锌离子的结合率较高,且该配合物对尿素具有很好的吸附作用。     

不同分子量的壳聚糖亚铁配合物的合成及其对尿素的吸附性能

本文研究了H2O2-HAc控制氧化制备壳寡糖的适宜工艺条件，合成了三种不同聚合度(分子量分别为78万、11万和1万)的壳聚糖，进而优化了与亚铁配位的条件，得到了三种壳聚糖亚铁配合物，同时分别研究了它们对尿素的吸附性能，并与其它不同尿素吸附材料做了比较，结果表明，壳聚糖亚铁配合物对尿素具有较高的吸附容量和较高的选择性，在pH值为5．5、尿素的初始浓度为1．5mg／ml时，其吸附容量为60．90mg／g，明显高于其它材料，略低于乙烯多胺-Cu(Ⅱ)配合物的吸附容量，但鉴于壳聚糖优良的生物活性和医用性能，仍不失为一种高效新型尿素吸附剂材料。     

棉织物的壳聚糖金属配合物/H2O2室温漂白

通过壳聚糖在极稀的溶液中与金属离子Cu2+、Zn2+进行配位,形成2种壳聚糖金属配合物,研究这2种配合物催化H2O2氧化分解的动力学和对棉织物的室温漂白效果。结果表明：壳聚糖金属配合物在室温下能够较好地催化H2O2分解,分解率符合表观一级反应动力学;pH值、配合物初始浓度是影响壳聚糖金属配合物催化性能的重要因素。CTS′- Zn(II)配合物初始质量浓度为3g/L,pH值为11时催化效果最好;CTS′- Cu (II)配合物初始质量浓度为3g/L,pH值为8时催化效果最好。对棉织物的室温漂白效果与传统工艺相近,且强力保留率能达到90%以上。     

壳聚糖对镉铅混合离子吸附作用的研究

研究了壳聚糖对镉铅混合溶液中镉离子和铅离子的吸附情况,探讨了pH、温度、反应时间、壳聚糖添加量和金属离子初始浓度等因素对其吸附性能的影响.结果表明,壳聚糖对混合溶液中Cd2+和Pb2+离子的吸附取决于溶液的pH、反应时间、壳聚糖添加量和金属离子的初始浓度,而温度对吸附的影响较小.壳聚糖对混液中Cd2+、pb2+离子的动...     

改性磁性壳聚糖对胭脂红的吸附性能评价

以纳米Fe₃O₄、壳聚糖为材料,采用反相悬浮交联法,用三乙胺做改性剂制备改性磁性壳聚糖,研究其对胭脂红色素的吸附性能影响,考察时间、pH、温度及胭脂红的初始浓度等四个因素对改性磁性壳聚糖吸附胭脂红溶液吸附效果的影响,并对吸附动力学模型、吸附等温模型、吸附热力学和吸附再生性能进行初步探讨。结果表明,当pH=3,吸附时间为270 min,温度为50℃,初始浓度为100 mg/L时,改性磁性壳聚糖对胭脂红溶液的吸附率达到最高,为96.72%。改性磁性壳聚糖对胭脂红溶液的吸附动力学数据符合准二级动力学模型,吸附等温线数据符合Langmuir模型,热力学数据拟合得出ΔH>0,ΔS>0,ΔG<0,得出此反应是吸热反应。经过三次吸附-解析实验,吸附率和解析率仍在40%以上。     

羟丙基壳聚糖对Cu^2＋的吸附性能研究

本文研究羟丙基壳聚糖对Cu2+的吸附作用,探讨溶液的pH值、反应时间、温度、吸附剂浓度和用量等因素对其吸附性能的影响.实验表明:pH和吸附剂浓度是羟丙基壳聚糖吸附Cu2+的主要影响因素.在pH 5时,对Cu2+初始浓度为100mg/L的溶液,可控制温度在20℃左右吸附2h,吸附剂羟丙基壳聚糖溶液浓度为1%时具有较好的吸附效果;并且发现随着吸附剂浓度的升高吸附量急剧下降.     

壳聚糖-Zn(Ⅱ)配合物对尿素的吸附行为的研究

本文提出了利用高分子聚合物壳聚糖-Zn(Ⅱ)配合物吸附尿素的方法。实验结果表明,最佳吸附条件为:室温下,溶液pH在6～7之间,尿素的起始浓度为2.0mg/ml,反应时间为3.0h,最大吸附量可达83.97mg/g。     

生物吸附剂壳聚糖对刚果红的吸附

为了确定生物吸附剂壳聚糖对刚果红的吸附行为特征,研究了pH值、初始浓度、时间及温度对刚果红在壳聚糖上吸附的影响。结果表明,pH值是影响壳聚糖吸附刚果红的重要因素,最佳pH值范围为4~7;动力学行为符合Lagergren准二级反应动力学模型,随着温度增加,平衡吸附量减少。吸附过程的表观活化能(Ea)为4.941 kJ/mol。壳聚糖对刚果红的吸附过程较好地符合Freundlich吸附等温方程。计算得到吸附过程的热力学参数△Go和△Ho分别为-10.10 kJ/mol(303 K)和-87.36 kJ/mol,表明壳聚糖对刚果红的吸附是一个自发的放热过程。红外光谱分析可知,壳聚糖吸附刚果红的过程中,壳聚糖分子中存在的大量羟基和氨基发挥了主要作用。     

壳聚糖对化学镀前处理中Pd2+的吸附行为

以壳聚糖为涤纶织物表面的载体层,研究了其对活化液中钯离子(Pd2+)的吸附性能.结果表明,活化液初始质量浓度及温度对PET-CS吸附Pd2+有显著影响,在活化液初始质量浓度为40-50 mg/L、温度为60℃时,吸附效果最好.壳聚糖对钯离子的吸附较符合二级吸附动力学方程,室温下,反应速率常数为0.174 3 min-1可推知.此吸附反应是化学吸附,该吸附行为更符合Langmuir吸附等温式,可认为是单分子层吸附.红外图谱分析表明:Pd2+与壳聚糖中-NH2、-OH发生了配位反应.     

苦味酸-氧化羧甲基纤维素酯的制备及其对尿素和肌酐的吸附性能

以羧甲基纤维素钠为原料,高碘酸钠为选择性氧化剂,在酸性条件下制备氧化的羧甲基纤维素。再将氧化的羧甲基纤维素6位的羧基进行酰化,与苦味酸反应制备复合型靶向口服吸附剂苦味酸-氧化羧甲基纤维素酯。通过XRD、FTIR、元素分析及化学官能团测定(碱熔法测醛基含量)等方法对苦味酸-氧化羧甲基纤维素酯的结构进行表征,结果表明苦味酸-氧化羧甲基纤维素酯已生成;在模拟人体生理介质的条件下,测定苦味酸-氧化羧甲基纤维素酯对尿素和肌酐的吸附性能,对尿素和肌酐的吸附平衡时间分别为10h和6h,醛基含量为75.23%。对尿素和肌酐的饱和吸附容量分别为16.08mg/g和2.10mg/g。尿素在氧化CMC-PA上的吸附等温线均符合Freundich方程,说明主要为化学吸附且吸附指数(1/n)小于2,表明吸附为"优惠吸附"。     

New Starch Phosphate Carbamides of High Swelling Ability: Synthesis and Characterization

The paper describes the synthesis of starch phosphate carbamides by reacting starch with phosphoric acid and urea. A solid state technique in vacuum at elevated temperatures is used. The degree of substitution of phosphate (DS_P) and carbamide groups (DS_C) can be adjusted by the molar ratio of starch: phosphoric acid: urea, the reaction temperature, and time. The starch derivatives prepared show remarkable swelling if the DS_P ranges between 0.2 and 0.3. With increasing content of urea in the reaction mixture the water‐holding ability is still significantly improved, which is explained by chemically and especially physically introduced urea into the starch polymer. Furthermore, the ratio of amylose: amylopectin of the starch samples influences both the DS values and the physicochemical properties, e.g., swelling power and multivalent metal ion adsorption of the products. The structure of the new polymers was determined by means of FTIR, ¹³C‐ and ³¹P NMR spectroscopy as well as by gel permeation chromatography (GPC).     

Some Studies on Starch Carbamate

Starch carbamate was prepared by reacting maize starch with urea using solid state technique. The different factors affecting this reaction were studied. These factors include urea concentration, type of starch, reaction and duration. The carbamate extent and carbamation reaction efficiency (%) were traced by estimating the nitrogen content of the reaction product. Solubility, viscosity and total ester content of starch carbamate samples were estimated. The carbamate extent increases by increasing urea concentration as well as reaction temperature and duration. Increasing the reaction temperature and duration has the same effect on carbamation reaction efficiency (%), while increasing urea concentration do the reverse. The solubility (%) of starch carbamate samples depends on urea concentration, reaction temperature and duration as well as the type of starch used. The maximum solubility obtained was 63% and 43% for starch carbamate derived from pregelled and native starch, respectively. Tentative mechanism for the reaction between starch and urea has been proposed.     

Spectral induced polarization signatures of hydroxide adsorption and mineral precipitation in porous media

The spectral induced polarization (SIP) technique is a promising approach for delineating subsurface physical and chemical property changes in a minimally invasive manner. To facilitate the understanding of position and chemical properties of reaction fronts that involve mineral precipitation in porous media, we investigated spatiotemporal variations in complex conductivity during evolution of urea hydrolysis and calcite precipitation reaction fronts within a silica gel column. The real and imaginary parts of complex conductivity were shown to be sensitive to changes in both solution chemistry and calcium carbonate precipitation. Distinct changes in imaginary conductivity coincided with increased hydroxide ion concentration during urea hydrolysis. In a separate experiment focused on the effect of hydroxide concentration on interfacial polarization of silica gel and well-sorted sand, we found a significant dependence of the polarization response on pH changes of the solution. We propose a conceptual model describing hydroxide ion adsorption behavior in silica gel and its control on interfacial polarizability. Our results demonstrate the utility of SIP for noninvasive monitoring of reaction fronts, and indicate its potential for quantifying geochemical processes that control the polarization responses of porous media at larger spatial scales in the natural environment.     

Effects of surface features on sulfur dioxide adsorption on calcined NiAl hydrotalcite-like compounds

The hydrotalcite-based NiAl mixed oxides were synthesized by coprecipitation and urea hydrolysis approaches and employed for SO? removal. The samples were well characterized by inductively coupled plasma (ICP) elemental analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and N? adsorption/desorption isotherm analyses. The acid-base properties were characterized by pyridine chemisorption and CO? temperature-programmed desorption (TPD). The calcined NiAlO from the urea method showed excellent SO? adsorption and its adsorption equilibrium showed a type I isotherm, which significantly improved the adsorption performance for low-concentration SO?. Both the physical structure and the acidic-basic sites were found to play important roles in the SO? adsorption process. In situ Fourier transform infrared spectroscopy (FTIR) investigation revealed that adsorbed SO? molecules formed surface bisulfite, sulfite, and bidentate binuclear sulfate. The mechanisms for SO? adsorption and transformation are discussed in detail.     

玉米交联微孔淀粉制备工艺的研究

研究了制备玉米交联微孔淀粉的工艺条件,以交联微孔淀粉的吸水、吸油率作为考察指标,通过单因素和正交试验,考察温度、时间、酶用量、酶配比、淀粉乳浓度、pH值对交联微孔淀粉吸水、吸油率的影响,结果确定最佳酶解工艺条件为:温度50℃,时间24h,酶量2.3%,淀粉乳浓度18%,pH值5.0,酶配比1:8,所得交联微孔淀粉的吸水、吸油率分别为163.21%、134.20%。     

无机水合氧化物对磷酸根的吸附行为

制备出一种新型的无机水合氧化物吸附剂,并用该氧化物对磷酸根水溶液进行吸附试验.实验分析了pH值、吸附温度和吸附时间对吸附容量的影响,同时也讨论了吸附过程相关的动力学、热力学和扩散速率.结果表明:该吸附过程为吸热吸附,它主要是以离子交换形式进行的.高温吸附与Langmuir等温吸附方程的拟合要优于低温吸附,高温下的吸附速率为一级动力学而低温吸附更趋于抛物扩散方程.     

无机水合氧化物对磷酸根的吸附行为

制备出一种新型的无机水合氧化物吸附荆，并用该氧化物对磷酸根水溶液进行吸附试验。实验分析了pH值、吸附温度和吸附时间对吸附容量的影响，同时也讨论了吸附过程相关的动力学、热力学和扩散速率。结果表明：该吸附过程为吸热吸附，它主要是以离子交换形式进行的。高温吸附与Langmuir等温吸附方程的拟合要优于低温吸附，高温下的吸附速率为一级动力学而低温吸附更趋于抛物扩散方程。     

Application of an Acid Urease to Wine: Determination of Trace Urea in Wine

An improved method of urea detection having a sensitivity to 0.05 ppm, applicable to white wines, was developed by modifying Jansen's procedure. The urea concentration in many commercial bottled wines was found to be around 2 ppm. The method was utilized to the urea degradation by an acid urease which degraded naturally occurring urea of 0.5–2 ppm at the same reaction rate as that for the spiked urea of 30 ppm in the same white wine. Wine treatment with the acid urease also reduced ethyl carbamate formed by heating.