硫酸水解对再生纤维素纤维葡萄糖转化率的影响

用浓硫酸水解竹浆、棉浆、木浆三种再生纤维素纤维,通过改变反应温度和时间,找出再生纤维素纤维水解葡萄糖得率最优的反应条件,并对不同种类的纤维素纤维水解液进行高效液相色谱分析。结果表明:当反应温度为50℃、反应时间为120 min时,竹浆再生纤维素纤维的葡萄糖转化率可达75%;在高效液相色谱中,竹浆再生纤维素纤维在7 min的位置有较明显的出峰,在12.5～14.5 min的位置有一个双峰,有别于木浆、棉浆再生纤维素纤维。     

All-cellulose films with excellent strength and toughness via a facile approach of dissolution–regeneration

This study describes a green method for preparing all-cellulose nanocomposites through a dissolution and regeneration process. Cotton linter pulp was dissolved in 7 wt % NaOH/12 wt % urea aqueous solution precooled to −12°C. Self-assembly of cellulose molecules into nanostructured cellulose fiber is achieved by using water addition and controlling the temperature to regenerate cellulose. By changing the microenvironment of the cellulose solution, the morphology of the nanostructured cellulose fibers and the mechanical properties of the regenerated cellulose films can be tuned. Then, a series of regenerated cellulose films have been prepared and characterized from various aspects. Compared with other all-cellulose films in the literature, the regenerated all-cellulose nanocomposite films prepared in this work exhibited good optical transparency, thermal stability, and excellent tensile strength (up to 135 MPa) when the regeneration temperature was adjusted to 50°C. This work provided a green and promising approach to prepare high-performance and environmentally friendly all-cellulose nanocomposites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46925.     

竹纤维素在NMMO中溶解再生前后的结构研究

以竹浆粕为原料、N-甲基吗啉-N-氧化物(NMMO)为溶剂,利用傅里叶红外光谱、X射线衍射、热重分析等着重研究了竹纤维素在NMMO中溶解前后结构的变化。研究发现:NMMO溶解纤维素过程属于物理过程,未发生衍生化反应,竹纤维素溶解后聚合度较溶解前有所降低,晶型由纤维素Ⅰ变成了纤维素Ⅱ;热重分析表明纤维素再生前后都具有较好的热稳定性。     

The dissolution of cellulose in anhydrous chloral/aprotic solvents

Two new approaches toward the chemical modification and rapid dissolution of cellulose pulp in aprotic solvents containing chloral are presented. In the first method, cellulose pulp is water activated and then solvent exchanged prior to the addition of chloral. In the second method, cellulose pulp is heated in refluxing solvent and then cooled to ambient temperature before the addition of chloral. The methods do not entail the use of catalysts but require the preactivation of the pulp prior to treatment with chloral. Clear solutions obtained by the water activation–solvent exchange method were cast into films, and after washing with water the product was soluble in a variety of organic solvents including acetone. IR and NMR (¹H and ¹³C) analyses as well as chemical analyses led to the conclusion that a cellulose chloral hemiacetal with a DS of 2.2 is initially formed which then slowly decomposes upon standing at 23°C to a relatively stable hemiacetal of DS 0.4. Complete regeneration to cellulose results upon standing for an extended period or treatment with 1 N acetic acid at 80°C, 1 N HCl at 50°C, 0.5% NH₄OH or 0.1 N NaOH at 23°C. When solutions, obtained by the hot solvent activation method, were coagulated in water at ambient temperature, regenerated cellulose was obtained. In both methods, little or no degradation of the regenerated cellulose resulted.     

缓冲溶液对TEMPO/NaClO/NaBr选择性氧化纤维素的影响

TEMPO/NaClO/NaBr氧化体系被广泛应用于选择性氧化糖类C6位伯醇羟基,使其成为羧酸盐物质,从而获得更好的水溶性或其他特定功能。但在氧化反应过程中,pH随反应的进行下降,并且存在pH值持续控制繁琐等问题。实验比较分析TEMPO/NaClO/NaBr氧化纤维素在碳酸钠―碳酸氢钠缓冲溶液、硼砂―氢氧化钠缓冲溶液中的适用性,并以滴加的方式向体系中加入氧化剂NaClO溶液,探索两种缓冲体系中各自适宜的NaClO滴加速度。实验结果表明,碳酸钠―碳酸氢钠缓冲溶液和硼砂―氢氧化钠缓冲溶液都适用于TEMPO/NaClO/NaBr氧化体系。与传统方法相比,氧化纤维素的羧基含量可以提高20%～25%。使用缓冲溶液较单一氢氧化钠溶液对稳定pH值有更好的效果,并且方法简便。另外,硼砂―氢氧化钠缓冲溶液对NaClO滴加速度敏感,控制滴加速度可以有效地提高反应活性。     

Polymer-Enhanced Crossflow Filtration for Removal of Fe(III), Cu(II), and Cd(II) Ions from Dilute Aqueous Solutions

Abstract

The removal of Fe(III), Cu(II), and Cd(II) ions from aqueous solutions was studied by polymer-enhanced crossflow filtration technique. Alginic acid polymer was used as complexing agents to enhance the retention. Alginic acid/cellulose composite membranes were used in the filtration. In the filtration of metal ion solutions the effects of alginic acid content of the membranes and pH on the percent retention and the permeate flux were examined. The maximum percent retention was found as 98% for 1 × 10^?4 M Fe(III) solution at the flow velocity of 100 mL/min, pH of 3.0, pressure of 60 kPa in the presence of alginic acid as complexing agent by using 0.25 (w/v)% alginic acid/cellulose composite membranes. For 1 × 10^?4 M Cu(II) and Cd(II) solutions the maximum percent retentions were found as 71% and 80% respectively using 0.50 (w/v)% Alginic acid/cellulose composite membranes when the filtration was carried out in the presence of alginic acid at pressure of 10 kPa, flow velocity of 100 mL/min and pH of 7.0.     

Regeneration of 4-Chlorophenol Exhausted GAC with a Microwave Assisted Wet Peroxide Oxidation Process

To improve the performance of wet oxidation for the regeneration of GAC, a microwave assisted wet peroxide oxidation process has been applied for the regeneration of 4-chlorophenol exhausted GAC. The effects of various factors including reaction temperature, H₂O₂ dosage, reaction time, and addition of catalyst have been studied. The regeneration improves with the increase in reaction temperature, H₂O₂ dosage, and reaction time. The addition of Cu²⁺ further promotes the regeneration process. Under the conditions of temperature 150°C, H₂O₂ dosage 15 mmol, reaction time 20 min, Cu²⁺ concentration 20 mg/L, the regenerated GAC recovers 93.5% of its adsorption capacity. A nearly complete degradation of 4-chlorophenol in the aqueous phase is observed based on UV-vis and high-performance liquid chromatography spectra studies.     

ZnCl2水溶液制备纤维素膜的研究

以针叶浆为原料,ZnCl2水溶液为溶解溶剂,制备再生纤维素膜。利用单因数实验分析了纤维素膜制各过程中浆浓、反应温度、溶解时间对纤维素膜强度的影响,确定了最佳工艺条件为浆浓3％、反应温度90℃、溶解时间为2h。并通过X-射线衍射（XRD）、傅里叶变换红外光谱（FT-IR）、扫描电镜（SEM）分析,比较经ZnCl2水溶液处理前后纤维的结构和性能变化,发现ZnCl2水溶液是纤维素的非衍生化溶剂,经ZnCl2水溶液处理后的纤维素已由纤维素I转换为纤维素II,制备的再生纤维素膜具有一定的强度,且具有多孔性的特征。     

Regenerated cellulose membrane prepared with ionic liquid 1‐butyl‐3‐methylimidazolium chloride as solvent using wheat straw

BACKGROUND: Currently, cellulose membranes are prepared by cellulose acetate hydrolysis or chemical derivatization dissolution and regeneration using cotton pulp or wood pulp. In this study, the concept ‘lignocelluloses biorefinery’ was used, and good quality long fiber was fractionated from wheat straw using clean technologies. The objective of this study is to develop wheat straw cellulose to prepare regenerated cellulose membrane with ionic liquid 1‐butyl‐3‐methylimidazolium chloride ([BMIM]Cl) as solvent. RESULTS: Wheat straw cellulose (WSC) fractionated from wheat straw contained 93.6% α‐cellulose and the degree of polymerization (DP) was 580. WSC was dissolved directly without derivatization in [BMIM]Cl. With increase in dissolving temperature, the DP of the regenerated cellulose dropped, which resulted in a decrease in the intensity of regenerated cellulose membrane. After regeneration in [BMIM]Cl, the WSC transformed from cellulose I to cellulose II, and the crystallinity of the regenerated cellulose was lower than the original cellulose. The regenerated WSC membrane had good mechanical performance and permeability, the tensile strength and breaking elongation were 170 MPa and 6.4%, respectively, the pure water flux was 238.9 L m^?2 h^?1 at 0.3 MPa pressure, and the rejection of BSA was stabilized at about 97%. CONCLUSION: Wheat straw cellulose fractionated from wheat straw satisfied the requirement to prepare regenerated cellulose membrane using ionic liquid [BMIM]Cl as solvent. Copyright © 2012 Society of Chemical Industry     

Studies in Accelerated Oxidation of Cellulose. I—Hypochlorite Oxidation of Cellulose in Presence of Manganous Hydroxide

The oxidation of cellulose by treatment with sodium hypochlorite in the presence of different amounts of manganous hydroxide at different pH values (4·5–9·0) for a short time (10 min) has been investigated. Treatments with chlorous acid and sodium borohydride have been utilised to determine the different types of reducing and acidic groups formed in cellulose during accelerated oxidation. Manganous hydroxide has been shown to be a milder accelerant of the hypochlorite oxidation of cellulose than either leuco vat dyes or ferrous hydroxide under similar conditions.     

Periodate oxidation of cellulose by homogeneous reaction

Homogeneous periodate oxidation of cellulose was achieved through methylol cellulose. The dissolution of methylol cellulose into aqueous periodate solution was followed by the gradual decomposition of methylol groups at random sites along the methylol cellulose chain. The recovery of glycol hydroxyl groups at the C₂ and C₃ positions on the glucopyranose ring during the above decomposition process caused uniform cleavage of C₂? C₃ bonds by the periodate ion. The oxidation level reached nearly 100% in 10 h. The reduced product of the resulting dialdehyde cellulose, i.e., dialcohol cellulose, resulted in mechanical properties quite different from those of conventional dialcohol cellulose. Examination of the thermal deformation and tensile properties revealed that no notable cellulose degradation occurred during the reaction. Our dialcohol cellulose gave a clear and transparent film with a flexible nature.     

Surfactant‐Enhanced Regeneration of Polymeric Resin in a Vapor‐Phase Application

Abstract

Surfactant enhanced carbon regeneration (SECR) was employed to regenerate a polymeric resin saturated with trichloroethylene (TCE), using an aqueous solution of the anionic surfactant sodium dodecyl sulfate (SDS). More than 95% of the sorbed TCE was removed in the desorption operation with a 0.1 M SDS solution at a superficial flow rate of 1 cm/min. The desorption rate of TCE from pores of the resin is limited by the concentration of SDS in the regenerant and its flow rate. From the breakthrough curve of the subsequent adsorption cycle without a flushing step following the desorption, only 40% of the effective adsorption capacity of the virgin resin is observed for the regenerated resin. With a water flushing step following the surfactant regeneration step, the effective adsorption capacity is significantly improved to about 60% of that of the virgin resin. Thermal gravimetric analysis indicates that the reduction in the effective adsorption capacity of regenerated resin resulted from the residual SDS remaining in the pores of the resin. The regeneration step is equilibrium limited whereas the water flushing step is rate limited under the studied conditions. Despite the loss of subsequent cycle adsorption capacity, SECR may still be economical as an in‐situ, low temperature regeneration method.     

Surfactant‐Enhanced Carbon Regeneration in a Vapor‐Phase Application

Abstract

Coal‐based granular activated carbon (GAC) is saturated with trichloroethylene (TCE) by passing air through a fix bed adsorber. In surfactant‐enhanced carbon regeneration, an aqueous solution of anionic surfactant, sodium dodecyl sulfate (SDS), is passed through the bed to induce desorption of TCE. More than 95% of the sorbed TCE was removed in the desorption operation with a 0.1 M SDS solution at a superficial flow rate of 1 cm/min. The desorption rate of TCE from pores of GAC is limited by pore diffusion and not significantly affected by either the concentration of SDS in the regenerant (when well above the critical micelle concentration) or its flow rate. From the breakthrough curve of a subsequent adsorption cycle without a flushing step following the desorption, only 7% of the virgin carbon effective adsorption capacity is observed for the regenerated carbon. With a water flushing step following the regeneration step, the effective adsorption capacity is significantly improved to about 15% of that of virgin carbon. Increased temperature of the flushing water also enhances the effective adsorption capacity of the regenerated GAC. Separate batch adsorption‐desorption isotherms of SDS on GAC support the enhanced desorption of SDS at elevated temperatures. The drastic reduction in the effective adsorption capacity of regenerated GAC results from the residual SDS remaining in the pores of GAC as confirmed by thermal gravimetric analysis. Both the regeneration and water flush steps are rate limited under conditionsused here.     

High‐strength regenerated cellulose fibers spun from 1‐butyl‐3‐methylimidazolium chloride solutions

High‐performance regenerated cellulose fibers were prepared from cellulose/1‐butyl‐3‐methylimidazolium chloride (BMIMCl) solutions via dry‐jet wet spinning. The spinnability of the solution was initially evaluated using the maximum winding speed of the solution spinning line under various ambient temperatures and relative humidities in the air gap. The subsequent spinning trials were conducted under various air gap conditions in a water coagulation bath. It was found that low temperature and low relative humidity in the air gap were important to obtain fibers with high tensile strength at a high draw ratio. From a 10 wt % cellulose/BMIMCl solution, regenerated fibers with tensile strength up to 886 MPa were prepared below 22 °C and relative humidity of 50%. High strengthening was also strongly linked with the fixation effect on fibers during washing and drying processes. Furthermore, an effective attempt to prepare higher performance fibers was conducted from a higher polymer concentration solution using a high molecular weight dissolving pulp. Eventually, fibers with a tensile strength of ～1 GPa and Young's modulus over 35 GPa were prepared. These tensile properties were ranked at the highest level for regenerated cellulose fibers prepared by an ionic liquid–based process. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45551.     

Preparation and properties of chemical cellulose from ascidian tunic and their regenerated cellulose fibers

Chemical cellulose (dissolving pulp) was prepared from ascidian tunic by modified paper‐pulp process (prehydrolysis with acidic aqueous solution of H₂SO₄, digestion with alkali aqueous solution of NaOH/Na₂S, bleaching with aqueous NaOCl solution, and washing with acetone/water). The α‐ cellulose content and the degree of polymerization (DPw) of the chemical cellulose was about 98 wt % and 918, respectively. The Japanese Industrial Standard (JIS) whiteness of the chemical cellulose was about 98%. From the X‐ray diffraction patterns and ¹³C‐NMR spectrum, it was found that the chemical cellulose obtained here has cellulose Iβ crystal structure. A new regenerated cellulose fiber was prepared from the chemical cellulose by dry–wet spinning using N‐methylmorpholine‐ N‐oxide (NMMO)/water (87/13 wt %) as solvent. The new regenerated cellulose fiber prepared in this study has a higher ratio of wet‐to‐dry strength (<0.97) than commercially regenerated cellulose fibers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1634–1643, 2002.     

A novel carbon aerogel prepared for adsorption of copper(II) ion in water

A novel carbon aerogel with network pore and surface group of hydroxyl was prepared from cellulose colloid, through sol-gel reaction, freeze-drying and carbonization. Surfactant like isooctyl alcohol ether phosphate was taken as structure inducer in sol-gel reaction, for construction of porous network in the prepared samples. Characteristic of a specific area about 725.12 m²/g and total pore volume about 0.64 cm³/g, the prepared cellulose-based carbon aerogel of CCA₂, has a maximum capacity about 55.25 mg/g for Cu²⁺ in neutral aqueous solution. Its adsorption equilibrium can be reached within 10 min in an aqueous solution of pH7.0 at 25?°C, while desorption of Cu²⁺ need about 1 h eluted by HCl or HNO₃ solution of 0.01 M. And regeneration of the carbon aerogel in adsorption of Cu²⁺ can be repeated for five times, remaining 96% adsorption capacity. It is also found in adsorption process the kinetics nicely follows pseudo-second-order rate expression, and the isotherm fits Langmuir model.     

乙酸钠法选择性脱除CO2中的SO2

考察了用乙酸钠溶液选择性吸收二氧化碳中的二氧化硫,用碳酸钙再生使乙酸钠循环使用,并得到副产物石膏。该方法与已有的柠檬酸钠法相比,成本低,再生副反应少。实验主要分为吸收、氧化、再生三个步骤,静态分别考察不同因素对吸收率,氧化率以及再生过程的影响。结果表明：吸收过程中乙酸钠溶液的浓度为0.08 mol/L时,对SO2的吸收效果较好,且低温更有利于吸收。氧化过程最佳条件为：催化剂硫酸锰浓度为0.03 mol/L,温度90 ℃,转速400 r/min,空气流量150 mL/min,pH=4.0。再生时控制碳酸钙加入量在0.7 g左右,且反应在90 ℃进行,有利于生成硫酸钙;再生5次,再生液吸收的穿透时间基本不变,饱和吸收量略有减小。     

TCF BLEACHED PULPS FROM MISCANTHUS SINENSIS BY THE IMPREGNATION RAPID STEAM PULPING (IRSP) PROCESS

ABSTRACT

The production of bleached cellulose pulps from elephant grass (Miscanthus sinensis) via a two-stage soda pulping process and a TCF bleaching sequence is evaluated in this work. The impregnation rapid steam pulping process (IRSP) involves impregnating of the lignocellulosic material with the pulping liquor, withdrawing the excess liquor and rapidly steaming the impregnated material at 180–200°C for a short time. In this paper the process variables and their effect on the kappa number, yield and viscosity of the unbleached pulps are discussed. Bleaching by an ozone-based TCF sequence was tested, and the papermaking properties of the bleached pulp were determined. A kappa number of 19 was obtained by impregnating at an alkali charge of 30 + 0.1% anthraquinone carboxylic acid (AQCA) and pulping at 180°C for only 15 min. Kappa was reduced to 16 by extending pulping time to 26 min. The alkali consumption during impregnation and pulping was 10.2 g NaOH/100 g of dry Miscanthus. Screened pulp yield, viscosity and brightness for this pulp were 54.6%, 913 mL/g and 37.3%, respectively. After bleaching, the pulp had an ISO brightness of 87.4% and a viscosity of 700 mL/g. Refining in a PFI mill provided optimal strength properties of the bleached pulp at 4500 revolutions (71°SR): breaking length 7.2 km, tensile index 72 N m/g, and burst index 4.3 kN/g. Tear index was 7.9 mN m²/g at this degree of refining.     

Electrochemical Regeneration of Zn-Saturated Granular Activated Carbon from Electroplating Wastewater Plant

An electrically assisted regeneration (EAR) process was used to assess the effectiveness of regenerating exhausted granular activated carbon (GAC) preloaded with electroplating wastewater containing hyper Zn concentration at a concentration of 950.5 mg L ^?1  (1.45 × 10 ^?2  mol L ^?1 ). The electrochemical rege-neration process supplied with direct current was controlled at a constant voltage of 5.0 V. Two regeneration methods were tested and compared: first, acid washing (pH 1.0) and, second, electrically assisted acid washing. Results showed that the Zn adsorption capacity of GAC regenerated by EAR was significantly higher than that of GAC regenerated by acid washing. The effectiveness of the Zn desorbing efficiency from GAC was enhanced by electric current in the electrochemical regeneration process. Using the EAR method, a regeneration efficiency of 88.3% was observed for GAC, whereas using acid regeneration, the efficiency was only 25.3%. These observations reveal that EAR could be a potential alternative to acid washing for the regeneration of GAC saturated with Zn.     

Chemically modified celluloses. XIII. Periodate oxidation of cellulose dyed with reactive and direct dyes in the presence of electrolytes

Periodate oxidation of cellulose dyed with vinyl sulfone-type reactive dyes at 32°C in the presence of various concentrations of alkaline earth metal chlorides and a cationic dye-fixing agent has been studied. The extent of the oxidation has been assessed in terms of rate constant, time of half reaction, and percent accessibility to periodate ions. Remazol Black B was used in the study. This dye on reduction with sodium hydrosulfite after reaction with the fiber removes the sulfonic acid group containing a portion of the dye, leaving behind a portion reacted with the fiber and not containing a sulfonate group. The study has also been extended to a few direct dyes which, unlike reactive dyes, have been shown not to inhibit the rate of periodate oxidation of cellulose.