催化剂预加载Fenton氧化法微纤化纤维素的制备

以溶解浆为原料,采用催化剂预加载Fenton氧化协同高压均质法制备微纤化纤维素(MFC)。探讨了过氧化氢用量、催化剂七水硫酸亚铁用量、反应温度和反应时间对氧化效率的影响,并对氧化后纤维的微观形貌、化学结构变化及MFC微观结构、结晶度、热稳定性进行了表征。结果表明,催化剂预加载Fenton氧化法可显著提高氧化纤维中的羧基和醛基含量,降低纤维素聚合度和Zeta电位,增大纤维之间的静电斥力,利于后续的均质处理。在浆浓25%、过氧化氢用量0.15 g/g浆、七水硫酸亚铁用量1.5 g、pH值3、反应温度45℃、反应时间120 min条件下,氧化纤维中羧基和醛基含量分别为85.43μmol/g和57.32μmol/g,聚合度为154,Zeta电位为?34.72 mV。傅里叶变换红外光谱(FT-IR)表明Fenton氧化纤维成功制备,扫描电子显微镜(SEM)、X射线衍射(XRD)、热重分析(TG)表明MFC尺寸分布比较均匀,直径在200nm左右,结晶度为81.3%,热稳定性有所降低。     

氧化纤维素的体外及酶促体外降解行为研究

用TEMPO碱性氧化体系制备氧化纤维素,在模拟体液环境下,通过对氧化纤维素质量损失(Mms)和聚合度(DP)的变化,研究羧基含量和降解时间对氧化纤维素体外降解行为的影响;并采用在体液中添加纤维素酶的方式,对氧化纤维素的酶促体外降解进行研究。结果表明:在模拟体液环境下,随着羧基含量和降解时间的增加,氧化纤维素的体外降解和酶促体外降解的Mms均呈增长趋势,DP呈下降趋势;当羧基含量为1.56mmol/g,降解时间为3周时,氧化纤维素体外降解的质量损失为11.11%,聚合度下降50.42%;酶促体外降解质量损失提高至15.35%,聚合度下降64.44%。因此提高羧基含量,结合酶促降解,可提高纤维素的降解程度。该研究为氧化纤维素在生物医学领域的应用提供了理论依据。     

均相Fenton氧化降解对木素模型物对羟基苯丙酸去除效果的研究

以木素类模型物对羟基苯丙酸（HL）为研究对象,研究了均相Fenton试剂对HL的降解,探讨了体系pH值、H₂O₂用量、Fe²⁺用量、HL溶液初始质量浓度、反应时间、紫外光照射等因素对HL降解的影响。结果表明,在室温条件下,当体系原始pH值4.0时,加入2倍理论用量的H₂O₂,Fe²⁺与H₂O₂摩尔比为1∶100,反应60 min后,初始质量浓度为60 mg/L的HL溶液,其去除率可达79.2%;体系在紫外光照射下可形成协同效应,降解速度显著加快,同样条件下反应20 min,溶液中HL和TOC去除率分别可达到98.3%和79.6%。     

Ca2+交联羧基化麦草秸秆化机浆的制备及性能研究

本研究采用TEMPO氧化体系,转化麦草秸秆化机浆（SP）纤维素C6位上的羟基为羧基,制备羧基化麦草秸秆化机浆（CSP）;对CSP进行Ca²⁺交联,制备Ca²⁺交联羧基化麦草秸秆化机浆（CSP@Ca²⁺）,探究其纸浆的物理强度性能。基于FT-IR、XPS等手段可以明显检测CSP 纤维的羰基/羧基官能团：羧基化1 h麦草秸秆化机浆纤维（CSP1）的羧酸含量为0.27 mmol/g,其Zeta电位从SP的-21.7 mV变化为-29.2 mV,这为Ca²⁺的交联提供作用位点。纸张物理强度结果表明,CSP1@Ca²⁺0.5的抗张指数、耐破指数和撕裂指数分别较SP提高154.4%、170.8%和12.9%。最终,CSP1@Ca²⁺0.5与SP配抄纸张（配抄比例为50∶50）的抗张指数、耐破指数和撕裂指数分别达27.1 N·m/g、2.28 kPa·m²/g和3.68 mN·m²/g,较SP分别提高83.4%、115.1%和8.3%。     

光催化复合纤维及光催化纸的研制

以尿素为N源对TiO₂进行掺杂改性制备N掺杂TiO₂光催化剂（N-TiO₂）,将N-TiO₂与纤维素溶液混合,然后经静电纺丝制备光催化复合纤维,最后将光催化复合纤维与纸浆纤维配抄,制备光催化纸,用于降解甲醛。结果表明,所制备光催化剂N-TiO₂颗粒小、分散均匀,易与纤维素溶液纺丝成光催化复合纤维;所抄造光催化纸对甲醛的降解率达53.8%,抗张指数大于41.9 N·m/g,耐破指数大于2.03 kPa·m²/g,具有良好的强度性能。     

Al2O3负载ZnO催化臭氧氧化处理造纸废水的研究

将ZnO负载在Al₂O₃上,制备用于催化臭氧降解造纸废水中有机物的催化剂（Al₂O₃@ZnO）;采用场发射扫描电子显微镜（SEM）和X射线衍射仪（XRD）对Al₂O₃@ZnO催化剂进行物相分析;研究了造纸废水的初始pH值、反应时间和催化剂用量对Al₂O₃@ZnO催化臭氧氧化处理造纸废水效果的影响;并进行了自由基捕集剂叔丁醇实验,以探讨降解造纸废水中有机物的主要因素。结果表明,本研究成功制备了具有良好催化性能的Al₂O₃@ZnO催化剂;在造纸废水初始pH值为11、催化剂用量为2.0 g/L、反应时间为60 min的条件下,Al₂O₃@ZnO催化剂对造纸废水中COD_Cr的去除率可达到84.6％,与单独使用臭氧氧化方法相比,COD_Cr去除率明显提高,且COD_Cr的动力学降解反应遵循准一级动力学方程;叔丁醇的实验结果表明,在Al₂O₃@ZnO催化臭氧氧化处理造纸废水有机物的过程中,羟基自由基是降解废水有机物的主要因素。     

利用高碘酸钠选择性氧化阔叶木浆

高碘酸钠(NaIO4)选择性氧化纤维素得到双醛基纤维,提供了活性反应部位,可引入其他带电基团,增加纤维的润胀能力和分散特性,有利于制备微纤化纤维素(MFC)时机械处理过程中纤维的分丝帚化。采用正交实验分析了反应时间、反应温度、氧化剂用量和浆浓对NaIO4选择性氧化阔叶木浆的影响,通过测定醛基含量和聚合度分析主要影响因素,优化反应条件,同时探讨了打浆预处理以及体系的pH值对氧化反应的影响。结果表明,浆料的醛基含量随着氧化过程温度的升高、时间的延长、氧化剂用量和浆浓的增加而增加,聚合度则呈现下降的趋势。NaIO4用量对氧化阔叶木浆纤维的醛基含量和聚合度的影响最为显著,浆料的打浆预处理对NaIO4的氧化反应影响不明显,反应体系pH值的影响较为明显。NaIO4氧化阔叶木浆的优化条件为:反应温度45℃,反应时间2~3 h,NaIO4用量50%,浆浓2%~3%,pH值5~6。     

电Fenton技术深度处理造纸废水

采用电Fenton技术深度处理二级生化后的造纸废水,以色度去除率和COD去除率为主要考察指标,研究不同因素对造纸废水深度处理效果的影响。反应的最佳条件为：反应时间120 min、初始pH值=3、电压12 V、Fe²⁺浓度0.8 mmol/L、H₂O₂浓度0.8 mmol/L、极板间距10 cm、电解质Na₂SO₄浓度6 g/L。最佳反应条件下,电Fenton法对造纸废水的色度去除率和COD_Cr去除率分别达到89.5%和68.4%。动力学分析表明,电Fenton技术对造纸废水COD的降解符合一级反应动力学规律,一级反应速率常数为k=0.2072 min^-1。     

美藤果及美藤果油的理化性质和油脂的脂肪酸组成分析

对美藤果及美藤果油的理化性质和油脂的脂肪酸组成进行了分析。结果表明：美藤果粗蛋白质、粗纤维素、总糖及淀粉含量分别为28.87%、24.92%、6.33%和4.15%;美藤果油相对密度(d²⁰₂₀)为0.928 6,折光指数(n²⁰_d)为1.482 2,酸值(KOH)为0.46 mg/g,皂化值(KOH)为191.4 mg/g,碘值(I)为191 g/100 g,过氧化值为2.45 mmol/kg;美藤果油中共检出7种脂肪酸,主要为棕榈酸(3.83%)、硬脂酸(3.09%)、油酸(8.39%)、亚油酸(38.11%)、亚麻酸(45.62%),其中不饱和脂肪酸含量高达92.46%。     

高级氧化集成技术深度处理造纸废水工艺研究

本课题介绍一种活性炭吸附+芬顿氧化+臭氧催化氧化的高级氧化集成技术,并将其应用于造纸废水处理。结果表明,最佳处理条件为：活性炭添加量为0.5 g/L,吸附时间30 min,COD_Cr去除率达60%;芬顿氧化工艺处理活性炭吸附出水时,H₂O₂添加量为0.25 g/L,n(Fe²⁺):n(H₂O₂)=1:4、反应时间为1 h,COD_Cr去除率最高可达到32%;臭氧催化氧化处理芬顿氧化出水时,臭氧浓度为10%,H₂O₂加入量为0.1 g/L,气液比为2:1,反应时间为1.0 h,去除效果最佳。该高级氧化集成技术可将废水COD_Cr从180 mg/L降至25 mg/L,去除率为86.1%;达到地表水准Ⅳ类,综合运行成本为8.9元/t。     

High Carbonyl Content Oxidized Starch Prepared by Hydrogen Peroxide and Its Thermoplastic Application

Hydrogen peroxide was used to oxidize gelatinized starch to oxidized starch (OS) with degree of oxidation (DO) ranging from 0.096 to 0.554 depending on the H₂O₂/starch molar ratios used. Then glycerol was added to OS to produce thermoplastic oxidized starches (TPOS). Titrimetric determination of carboxyl and carbonyl groups, FT‐IR, ¹H‐NMR and ¹³C‐NMR confirmed that at H₂O₂/starch molar ratios < 0.7, oxidized starch contained much more aldehyde than carboxyl groups, while at molar ratios up to 2.0, peroxide oxidation produced mainly carboxyl groups. Scanning electron microscopy (SEM) revealed that the oxidized starch particles (at DO 0.385) obtained a porous structure. The effect of DO on the structure and properties of OS, as well as mechanical properties and moisture resistance of TPOS was studied, respectively. With an increase in DO, the crystallinity, intrinsic viscosity and thermal stability of OS decreased markedly, the ability of OS to take up water decreased at low DO and increased at higher DO. These observations show that hydrogen peroxide can be used to oxidize starch in a controlled way. TPOS with DO 0.385 showed the best mechanical properties, its tensile strength was 6.1 MPa after placing in 100% relative humidity for 15 days.     

Optimization of the Strength Properties of Waste Oil Palm (Elaeis Guineensis) Fronds Fiber

In this study, Box-Behnken design (BBD) and response surface methodology (RSM) was applied to study the effects of alkaline peroxide treatment variables (cooking time, sodium hydroxide concentrations, and hydrogen peroxide concentrations) on the pulp and paper strength properties (screened pulp yield, kappa number, tensile index, tear index, burst index), which are considered dependent variables or response variable of the extracted cellulose from oil palm (Elaeisguineensis) fronds (OPF) vascular bundle fibers. The results indicated that at the optimum operating conditions of 2.35% NaOH, 5.00% H₂O₂ and a 53.41 min cooking time, resulting maximum strength properties (tensile index, burst index, tear index,) gave 9.92 Nm/g, 6.55 KPam²/g, 6.22 mNm²/g, respectively. The study revealed that alkaline peroxide pulped fibers of oil palm frond vascular bundles could be considered a suitable alternative for paper qualities with moderate strength requirements.     

Molecular characteristics of tara galactomannans: Effect of degradation with hydrogen peroxide

Tara gum (M_w = 1519 × 10³ g/mol) was degraded by hydrogen peroxide in the presence/absence of ascorbic acid, and properties of the products were investigated using gel permeation chromatography, Fourier transform infrared spectroscopy, atomic force microscope, and rheometer methods. Results showed that molecular weight of tara gum decreased with increasing concentration of hydrogen peroxide. The addition of ascorbic acid could sharply increase the degradation rate and degree of tara gum by hydrogen peroxide, which is also confirmed by atomic force microscope. The degradation products kept the structure characteristics of galactomannan. However, they performed different rheological properties. At 1% (w/v) of concentration, DP1 (941 × 10³ g/mol) and DP2 (335 × 10³ g/mol) prepared by H₂O₂ exhibited non-Newtonian behavior, while DP3 (35.1 × 10³ g/mol) and DP4 (14.2 × 10³ g/mol) obtained by hydrogen peroxide plus ascorbic acid displayed Newtonian property. These results may promote the application of tara gum in diverse fields.     

纳米银/纳米二醛纤维素气凝胶的制备及表征

使用漂白硫酸盐针叶木浆为原料,以经高碘酸钠氧化后制备出的二醛纤维素为基材负载纳米银颗粒,后经高压均质法得到载银量为24.78%的纳米银/纳米二醛纤维素气凝胶。探讨高碘酸钠氧化反应时间对构成漂白硫酸盐针叶木浆的纤维素大分子以及针叶木纤维的影响。通过傅里叶变换红外光谱仪、X射线衍射仪、紫外可见分光光度计、扫描电子显微镜、透射电子显微镜和比表面积和孔径分析仪对样品进行表征。结果表明,随着氧化时间的增加,纤维素的醛基含量持续上升,当反应4 h时增至330 μmol/g,纤维的聚合度由1447大幅下降至525,同时零距抗张强度和长度也呈现下降趋势。制备出的载银气凝胶上负载的纳米银颗粒为球形,气凝胶的比表面积为35.40 m~2/g,平均孔径为19.62 nm。     

紫外线照射对漂白桉木硫酸盐浆热稳定性的影响

研究了植物纤维在波长360nm的紫外线下分别照射24h和48h后的变化。所用浆样为经ECF漂白的桉木硫酸盐浆,漂白流程为O/OD(EP)DP。经紫外线照射后,分析植物纤维聚合度的变化,抽提物和聚戊糖的含量,纤维中水溶出物紫外和可见光谱的变化以及热学分析(热重分析/差热分析)。紫外处理对纤维素的聚合程度没有影响。紫外处理后,羰基和羧基组分的吸收信号逐渐增加,可见纤维的水抽出物中含有纤维素的氧化物,这些氧化物影响纤维的热稳定性。     

漆酶对不同漂段纸浆催化氧化木素的效果研究

以未漂硫酸盐桉木浆(Sp浆)、氧脱木素桉木浆(O浆)、H_2O_2漂白桉木浆(P浆)作为不同漂段原料,探讨漆酶-谷氨酸体系对不同漂段纸浆的催化效果。结果表明,漆酶催化总体上可使纸浆的卡伯值增大,纸浆的白度随之下降;漆酶协同谷氨酸可催化氧化纤维表面木素与相邻纤维上的木素发生自由基偶合反应,同时使纤维表面的微细纤维暴露出来,两者共同作用使相邻纤维形成更好的结合力,使纸浆的强度性能大幅度提升;谷氨酸可通过漆酶催化氧化作用连接到木素上,增加纤维原料中的羧基含量,Sp浆、O浆、P浆羧基含量分别较未处理纸浆提高20%、50%、43%。     

Inactivation ofEscherichia coliO157:H7 by combinations of GRAS chemicals and temperature

Reported outbreaks of foodborne illness involvingEscherichia coliO157:H7 have increased in the United States during the last decade, with a variety of food products being implicated as vehicles of infection. Studies were carried out to determine the efficacy of combinations of various GRAS chemicals and moderate temperatures to killE. coliO157:H7. A five-strain mixture ofE. coliO157:H7 of approximately 10⁸cfu ml⁻¹was inoculated into 0·1% peptone solutions containing 1·0 or 1·5% lactic acid plus 0·1% hydrogen peroxide, 0·1% sodium benzoate or 0·005% glycerol monolaurate. The solutions were incubated at 8°C for 0, 15 and 30 min; at 22°C for 0, 10 and 20 min; or at 40°C for 0, 10 and 15 min; populations ofE. coliO157:H7 were determined at each sampling time. At 40°C, the pathogen was inactivated to undetectable levels within 10 min of incubation in the presence of 1·0 or 1·5% lactic acid plus hydrogen peroxide, and within 15 min of incubation in the presence of 1·5% lactic acid plus sodium benzoate or glycerol monolaurate. At 22°C, complete inactivation ofE. coliO157:H7 was observed after 20 min of exposure to 1·5% lactic acid plus 0·1% hydrogen peroxide, whereas a reduction of 5 log₁₀cfu ml⁻¹was observed with a treatment of 1·5% lactic acid plus glycerol monolaurate. None of the treatments resulted in total inactivation of the pathogen at 8°C. The aforementioned treatments could potentially be used to inactivate or reduceE. coliO157:H7 populations on raw produce.     

Environmental friendly polysaccharide modification – microwave‐assisted oxidation of starch

A “green” method for oxidized starch preparation was presented. Hydrogen peroxide (H₂O₂) was used as the starch oxidant. Two main types of experiments were investigated: catalytic (by means of sodium tungstate – Na₂WO₄, the hydrogen peroxide activator) and non‐catalytic processes. The research covers low microwave level synthesis. Ninety and one hundred and ninety watts of microwave power were applied for the samples. All the microwave‐assisted reactions were compared to conventional ones carried out at 80 and 90°C, respectively. Reaction was monitored using manganometric determination of H₂O₂ consumption during the reaction progress. Obtained reaction products were tested by means of carbonyl and carboxyl group content. Additionally, molecular mass changes were investigated and a preliminary rheological study was done. The observed significant differences in the degree of oxidation (monitored by means of carboxyl and carbonyl group content) as well as the changes in molecular mass of polysaccharide comparing to those found at conventional conditions were showed and discussed.     

不同纤维原料对羧乙基微纤化纤维素膜性能的影响

采用6种不同的纤维原料（漂白硫酸盐阔叶木浆、漂白硫酸盐竹浆、漂白硫酸盐针叶木浆、棉短绒浆、漂白针叶木化学机械浆和玉米芯纤维素）经羧乙基化预处理和机械研磨制备了微纤化纤维素（Microfibrillarized cellulose,MFC）,并通过涂布法制备了MFC膜。探讨了原料羧基含量、研磨程度和原料种类对MFC及其膜性能的影响。结果表明,随着预处理后漂白硫酸盐阔叶木浆羧基含量的增加,MFC的保水值由98%增加到538%,MFC膜的孔隙率由37%下降至19%。当羧基含量为0.8 mmol/g时,MFC膜的抗张强度最高,达53 MPa。另外,随着研磨程度（次数）的增加,所得MFC纤丝化程度提高,MFC膜的强度先升高后降低,最高值为75 MPa。在最优的羧乙基化预处理条件和研磨程度下,由6种不同纤维原料制备的MFC膜中,漂白硫酸盐竹浆所得MFC膜的强度最高,为84 MPa,其孔隙率为25%。