A Study on Physical and Chemical Properties of Cellulose Paper Immersed in Various Solvent Mixtures

The cellulose paper treated in proportional mixture systems showed higher liquid absorption compare to only EtOH and MeOH treatments. It was approximately 40–70% and 50–91% higher for EtOH-NaOH and MeOH-NaOH treated papers, respectively. All conditions apparently bring about an effect of decreased strength for papers. The lowest tensile strength of 13.0 N/mm was found with EtOH and NaOH treated samples after 5^th repeating wetting-drying stage. But, some conditions gave approximately 21–59.5% higher stretch than untreated samples. The pore size distributions of papers were evaluated with Simons stain procedure and experimental results usually consisted with sorption data. The less intense CH₂–CH₂- vibrations (1450–1700 cm⁻¹) and C-C and C-O-C peak areas in FTIR spectra indicates lowering H-bonds in solvent treated and dried paper network structure.     

Overcoming the Recalcitrance for the Conversion of Kenaf Pulp to Glucose via Microwave-Assisted Pre-Treatment Processes

This study evaluates the pre-treatment of cellulose from kenaf plant to yield sugar precursors for the production of ethanol or butanol for use as biofuel additives. In order to convert the crystalline cellulosic form to the amorphous form that can undergo enzymatic hydrolysis of the glycosidic bond to yield sugars, kenaf pulp samples were subjected to two different pre-treatment processes. In the acid pre-treatment, the pulp samples were treated with 37.5% hydrochloric acid in the presence of FeCl₃ at 50 °C or 90 °C whereas in the alkaline method, the pulp samples were treated with 25% sodium hydroxide at room temperature and with 2% or 5% sodium hydroxide at 50 °C. Microwave-assisted NaOH-treatment of the cellulose was also investigated and demonstrated to be capable of producing high glucose yield without adverse environmental impact by circumventing the use of large amounts of concentrated acids i.e., 83–85% phosphoric acid employed in most digestion processes. The treated samples were digested with the cellulase enzyme from Trichoderma reesei. The amount of glucose produced was quantified using the Quantichrom^™ glucose bioassay for assessing the efficiency of glucose production for each of the treatment processes. The microwave-assisted alkaline pre-treatment processes conducted at 50 °C were found to be the most effective in the conversion of the crystalline cellulose to the amorphous form based on the significantly higher yields of sugar produced by enzymatic hydrolysis compared to the untreated sample.     

表面活性剂对离子液体预处理纤维素的影响

采用离子液体1-甲基-3乙基咪唑磷酸二甲酯（[MEIM][DMP]）与表面活性剂耦合处理纤维素,考察表面活性剂对于酶解的影响,并用红外光谱、X射线衍射分析其机理。结果表明[MEIM][DMP]/聚乙二醇4000（PEG4000）处理的纤维素酶解率比未处理的纤维素高78.2%,比未加表面活性剂处理的再生纤维素高6.5%。红外光谱显示有PEG4000分子特征峰出现,X射线衍射分析表明PEG4000处理再生的纤维素几乎为无定形区。因此,PEG4000参与的处理有利于进一步提高纤维素酶解率,使结晶度降低,从而酶解率提高。     

基于金属盐溶液的纤维素溶解及其应用研究进展

纤维素是自然界储量最丰富的可再生生物质资源，其绿色高值化利用在实现“双碳”和“循环经济”目标中起到重要作用。纤维素的绿色高效溶解是实现其高值化利用重要途径之一。众多纤维素溶剂体系存在价格昂贵、毒性和环境威胁、溶解工艺复杂、溶解效率低、溶剂回收困难和能耗高等问题。金属盐溶液体系具有稳定性高、价格便宜，同时溶解纤维素速度快、溶解工艺简单等特点，是更具应用前景的低成本绿色溶剂。该文综述了不同金属盐溶液溶解纤维素的溶解机理，总结了影响溶解性能的关键因素，并进一步介绍了基于不同金属盐溶液溶解纤维素在薄膜材料、凝胶材料以及复合材料等领域的应用研究进展，总结并展望了金属盐溶液在纤维素溶解及功能化应用方面的优势、不足及发展方向。     

Cesium salt of a heteropolyacid in nanotubular channels and on the external surface of SBA-15 crystals: preparation and performance as acidic catalysts

The Cs-salt of heteropolyacid with stoichiometry Cs_2.5H_0.5PW₁₂O₄₀ (CsHPW) was deposited selectively at the external surface of the SBA-15 silica microcrystals, inside its mesoporous channels and simultaneously at both location modes. The structure, texture and performance of these CsHPW/SBA-15 composites were compared with that of a reference bulk salt of the same composition. Location of CsHPW salt on the external surface of SBA-15 microcrystals leads to disintegration of its agglomerates increasing acidity of the catalytic phase. A novel preparation strategy consisting of grafting the basic Cs-species at the internal pores surface of SBA-15 stabilized the CsHPW phase inside the channels in form of 5–8 nm nanocrystals at 30–70 wt.% loadings. The catalytic tests demonstrated that insertion of the CsHPW catalytic phase inside the nanotubular channels of SBA-15 in combination with location of an additional amount of this phase at the external surface of SBA-15 microcrystals allows to increase the specific activity of this phase in MTBE synthesis, propionylation of anisole and alkylation of catechol with t-butanol by a factor of 1.5–3. This level of specific activity in combination with high total loading of catalytic phase >60 wt.% permit to get composite catalytic materials with catalytic activity higher by a factor of 1.2–1.5 with respect to the bulk CsHPW catalyst and stabilizing the catalytic phase against colloidization in polar media.     

Effect of corona modification on the mechanical properties of polypropylene/cellulose composites

The effect of various corona treatment conditions on the mechanical properties of cellulose fibers/polypropylene composites was studied. The cellulose fibers and polypropylene were modified using a wide range of corona treatment levels and concentrations of oxygen. The treatment level of the fibers was evaluated using the electrical conductance of their aqueous suspensions. The mechanical properties of composites obtained from different combinations of treated or untreated cellulose fibers and polypropylene were characterized by tensile stress–strain measurements; they improved substantially when either the cellulose fibers alone or both components were treated, although composites made from untreated cellulose fibers and treated polypropylene showed a relatively small improvement. The results obtained indicate that dispersive forces are mostly responsible for the enhanced adhesion. The relationship between the electrical conductance of the fibers, the mechanical properties, and the mechanism of improved adhesion is discussed. © 1994 John Wiley & Sons, Inc.     

Crystallinity in the polypropylene/cellulose system. II. Crystallization kinetics

Nonisothermal differential scanning calorimetry data for neat polypropylene and polypropylene with variously treated cellulose fillers has been used to solve for the Avrami exponent, n. Results show neat polypropylene to have an Avrami exponent value very close to the theoretically excepted value of 4.0. The addition of untreated cellulose fibers to polypropylene, which has been shown to produce a transcrystalline region, results in an exponent value of 2.7–2.9 for the initiation stage, followed by a value of 3.9 for the bulk stage. Treatment of the cellulose with alkyl ketene dimer, alkenyl succinic anhydride, or stearic acid results in intermediate exponent values from 2.7 to 3.9. These results verify the effectiveness of surface treatments in reducing the natural nucleating ability of cellulose. Sample mixing and filler content were also shown to play a role in the crystallization process. © 1994 John Wiley & Sons, Inc.     

Correlation crystallinity and physical properties of heat-treated cellulose triacetate fibres

Previous measurements of crystallinity in fibres of cellulose triacetate have been qualitative or semi-quantitative; in this work quantitative measurements of relative crystallinity have been made on cellulose triacetate yarn heat treated in the range 20–300°C following the x-ray diffraction method of correlation crystallinity index. The onset of crystallization is clearly marked by a transition in the crystallinity index at 172°C, and beyond this annealing temperature tenacity and crystallinity are inversely correlated. Orientation also improves with annealing temperature with a less well defined transition around 120–180°C. Initial Young's modulus increases with temperature whilst other physical properties have optimum values in the range 180–220°C. Cutting and grinding are found to have an adverse effect on the correlation crystallinity index which is in fact a measure of lattice perfection.     

Thermal analysis of cellulose treated with boric acid or ammonium phosphate in varied oxygen atmospheres

Thermal analyses (TG, DTG, and DSC) of cellulose treated with diammonium phosphate or boric acid were conducted in atmospheres of differing oxygen concentration (N₂, and 2.5, 10, 21% O₂ in He). The weight loss process from both untreated and treated cellulose consists of a first, slow stage, a second, rapid stage, and a third, prolonged, char oxidation stage. The first two stages appear to be first-order reactions; their Arrhenius parameters were obtained. Both of the additives accelerate the beginning of the weight loss, increase the char yield, and inhibit the char oxidation. Boric acid inhibits the first stage and ammonium phosphate promotes it. The effects of oxygen are smaller than those of the additives. Oxygen produces three effects: acceleration of the beginning of the weight loss, an increase in the char yield, and oxidative gasification of the char. However, the dominant of these three effects changes depending on the oxygen concentration. The main weight loss and the char yield for untreated and treated cellulose may be explained by a chain reaction consisting of random-scission initiation, depropagation producing levoglucosan, and grafting termination, all describable by Arrhenius kinetics.     

On the low frequency dielectric behavior of carboxymethyl cellulose and its sodium salt

A dielectric dispersion and frequency loss peak within the low frequency range 0.05–1 kc/s and at temperatures of 283–333 K was observed in the case of the sodium salt of carboxymethyl cellulose and absent in the case of its acid form. The critical frequency of the dielectric absorption was independent of molecular weight and of the presence of low moisture content. The results obtained show that the variation with temperature of the dielectric constant is exponential at low frequency only in the case of the sodium salt of carboxymethyl cellulose. The significance of the results is discussed.     

Feasibility study for reclamation of a secondary treated sewage effluent mainly from industrial sources using a dual membrane process

A feasibility study for reclamation of a secondary treated sewage effluent mainly from industrial sources (60%) in Singapore has been conducted using a dual membrane UF-RO process. The pilot system had a treatment capacity of 2 m³/h. The UF unit and RO unit were operated at 70–80% and 40% water recovery, respectively. Six-month run for the pilot was carried out to study the stability and fouling tendency of membranes.

The characteristics of the raw feed indicated that ammonia-N was consistently high at 30–50 mg/L. Very high fluctuations in iron (0.3–3.7 mg/L), turbidity (1–27.1 NTU) and TOC (3.2–56.7 mg/L) were observed. Nitrate was low at <0.2 mg/L. The results of the study showed that dosage of alum in the UF process significantly reduced organic foulants and phosphate scalants. The polymeric RO membrane could tolerate organics from industrial wastewater and performed >96% salt rejection at the end of the study after 6 months. The study concluded the dual membrane process was capable of reclaiming the sewage effluent mainly from industrial sources for industrial use.     

吐温-80及碱预处理对饲用稻草木质素含量和纤维素酶解产糖的影响

探讨了添加1‰吐温-80非离子表面活性剂和不同浓度碱预处理对稻草秸秆木质素及纤维素的影响,并对预处理前后的稻草进行了X射线衍射光谱(XRD)分析,从结晶度的变化综合分析了预处理对纤维素酶解的影响。实验结果表明:在30℃下添加1‰吐温-80非离子表面活性剂时,用4%NaOH预处理稻草秸秆,木质素含量降至6.5%(较未处理稻草下降了41.9%),灰分值仅占6.9%,具有较好的粗饲料价值;在121℃(0.1 MPa)下添加1‰吐温-80非离子表面活性剂时,用4%NaOH预处理稻草秸秆,木质素含量降至2.8%(较未处理稻草下降了74.5%),酶解还原糖达到393.9 mg/g,纤维素糖化率为59.3%(较未处理稻草提高了2.4倍)。XRD分析显示,在较温和的条件下,低浓度碱预处理稻草秸秆,对纤维素结晶区带来的影响相对于无定形区弱,不足以引起纤维素结晶度的降低。     

Aerosol growth studies — IV. Phase transformation of mixed salt aerosols in a moist atmosphere

The phase transformation and subsequent droplet growth of the mixed salt aerosols NaCl—KCl and (NH₄)₂SO₄—H₂SO₄ were investigated in a continuous-flow apparatus at 25 and 30°C as a function of relative humidity. Monodisperse salt aerosols (d = ≈ 0.5 μm, OG = 1.07–1.13) were prepared and mixed with N₂ carrier gas at controlled humidities. The particle-size distribution of the aerosol before and after growth by water vapor condensation was continuously monitored with an optical particle counter. It was found that mixed salt aerosols were characterized by stage-wise growth when the relative humidity in the atmosphere was increased. The onset of growth took place at a specific deliquescence humidity determined by the water activity at the eutonic composition. Thus, mixed NaCl—KCl aerosols deliquesce at 73.8 ± 0.5% r.h. regardless of initial compositions. For sulfate aerosols containing 0.75 to 0.95 mole fraction (NH₄)₂SO₄ (the balance being H₂SO₄), the onset of growth occurs at 69.0 ± 0.5% r.h.. In the composition range of 0.5 to 0.75, a deliquescence humidity of 39.0 ± 0.5% is noted. Below 0.5 mole fraction, however, the mixed-sulfate aerosols are expected to exhibit hygroscopic properties on the basis of thermodynamic considerations.     

The durability of adhesive/carbon–carbon composites joints in salt water

This paper researches the durability of the adhesive/carbon–carbon (C–C) composites joints in salt water with infrared spectroscopy (IR), energy dispersive X-ray spectrosopy (EDX) and shear strength test methods. In salt water, Na⁺ and Cl⁻ ions can accelerate hydrolyzation of the adhesive and increase water ingress ability in the adhesive, although salt water cannot produce ionization potential between adhesive and C–C composites like adhesive/metal joints. The durability of the adhesive/C–C composites joints in salt water aging is lower than that in humidity aging by shear strength tests. EDX and IR spectra of the adhesive indicate that the salt water diffusion speed in the adhesive/C–C composites joints depend on not only temperature but also salt water aging time, i.e. time–temperature equivalence between temperature and salt water aging time. Shear strength tests also indicate that the rate of shear strength of the adhesive/C–C composites joints treated by silane coupling agent is lower than that treated by sand paper burnishing or by chemical oxidation in salt water aging.     

Correlation of 13C‐NMR analysis with fungal decay tests of polymeric structural wood constituents. II. Ground contact tests

Heat treatment at relatively high temperatures (ranging from 150°C to 260°C) appear to be an effective method to improve the durability of wood. This study investigated the reasons for the decay resistance of heat‐treated and untreated wood as composed of polymeric structural constituents by solid‐state CP‐MAS ¹³C‐NMR analysis after fungal exposure in ground contact. An industrially used two‐stage heat treatment method under relatively mild conditions (<200°C) was used to treat the samples. Fungal exposure in ground contact resulted in strong degradation of the carbohydrates (cellulose and hemicellulose) of treated and untreated Scots pine, Radiata pine, and Simaruba. Fungal attack of the carbohydrates appeared to occur mainly at C4, resulting in cleavage and eventually depolymerization of cellulose and hemicellulose. The CP‐MAS ¹³C‐NMR spectra of the heat‐treated wood revealed similarities but also clear differences after fungal exposure in ground contact with the untreated wood. In ground contact fungi appeared to attack the carbohydrates of heat‐treated wood at C1 and possibly at C4 in order to cleave and eventually depolymerize cellulose and hemicellulose. An attack on the out‐of‐the‐ring alcoholic group, ? CH₂OH, of the carbohydrates of the heat‐treated wood was observed (particularly in treated Radiata pine). The fungus possibly tried to cleave the out‐of‐the‐ring CH2? OH group on the main H‐bond fixing sites of the crystalline cellulose structure in order to open the cellulose crystalline structure to an amorphous structure to decrease its water repellency and facilitate enzymatic cellulose degradation; this was also observed, but to a lesser extent, in untreated Radiata pine and untreated Scots pine. The opening of the glucose pyranose ring in heat‐treated Simaruba after fungal exposure, not observed in the untreated wood, was remarkable, and the thermal degradation of alpha‐arabinofuranose during heat treatment indicated more extensive decay. Demethoxylation and ring opening of the aromatic structure of lignin were observed, especially in the heat‐treated Radiata pine, Douglas fir, and Simaruba. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 616–622, 2006     

Extraction and characterization of rice straw cellulose nanofibers by an optimized chemomechanical method

In this study, a chemomechanical method was performed to extract nanofibers from rice straw. This procedure included swelling, acid hydrolysis, alkali treatment, bleaching, and sonication. X‐ray diffractometer was employed to investigate the effect of acid hydrolysis conditions and other chemical treatments on the chemical structure of the extracted cellulose fibers. It was concluded that by increasing the acid concentration and hydrolysis time, the crystallinity of the extracted fibers was increased. The optimum acid hydrolysis conditions were found to be 2M and 2 h for the acid concentration and hydrolysis time, respectively. The chemical compositions of fibers including cellulose, hemicelluloses, lignin, and silica were determined by different examinations. It was noticed that almost all the silica content of fibers was solubilized in the swelling step. Moreover, the achieved results showed that the cellulose content of the alkali treated fibers was increased around 71% compared to the raw materials. ATR‐FTIR was applied out to compare the chemical structure of untreated and bleached fibers. The dimensions and morphology of the chemically and mechanically extracted nanofibers were investigated by scanning electron microscopy, field emission scanning electron microscopy, and transmission electron microscopy. The results of the image analyzer showed that almost 50% of fibers have a diameter within a range of 70–90 nm and length of several micrometers. The thermal gravimetric analyses were performed on the untreated and bleached fibers. It was demonstrated that the degradation temperature was increased around 19% for the purified fibers compared to raw materials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40063.     

The effect of the hydrothermal treatment with aqueous NaOH solution on the photocatalytic and photoelectrochemical properties of visible light-responsive TiO2 thin films

The effect of the hydrothermal treatment with aqueous NaOH solution on the photoelectrochemical and photocatalytic properties of visible light-responsive TiO₂ thin films prepared on Ti foil substrate (Vis-TiO₂/Ti) by a radio-frequency magnetron sputtering (RF-MS) deposition method has been investigated. The hydrothermally treated Vis-TiO₂/Ti electrodes exhibited a significant increase in their photocurrent under UV and visible light irradiation as compared to untreated Vis-TiO₂/Ti electrode. SEM investigations revealed that the surface morphology of Vis-TiO₂/Ti are drastically changed from the assembly of the TiO₂ crystallites to the stacking of nanowires with diameters of 30–50 nm with increasing hydrothermal treatment time (3–24 h), accompanying the increase in their surface area. The separate evolution of H₂ and O₂ from water under solar light irradiation was successfully achieved using the Vis-TiO₂/Ti/Pt which is hydrothermally treated for 5 h, while the H₂ evolution ratio was 15 μmol h⁻¹ in the early initial stage, corresponding to a solar energy conversion efficiency of 0.23%.     

氨碱废液溶采二层盐制备优级液体盐工艺研究

针对内蒙古吉兰泰盐湖补水困难、二层盐硫酸根含量高、氨碱废液排量大后处理困难等技术难题,分别探究了二层盐饱和卤水混配氨碱废液制备液体盐工艺,以及氨碱废液混兑蒸馏水后溶采二层盐制备液体盐工艺。通过在线拉曼实验,测得该反应达到平衡需要1 h以上;探究了机械搅拌速率、化学反应时间、氨碱废液与蒸馏水混配比例等因素对液体盐氯化钠、硫酸根、钙离子含量的影响。结果表明：在硫酸根和钙离子物质的量比为1∶1、25 ℃、300 r/min条件下,氯化钙和硫酸钠的反应过程是二水硫酸钙结晶过程的速率控制步骤;二层盐饱和卤水混配氨碱废液制备液体盐工艺中,在相同条件下,反应120 min后分离可获得优级液体盐;氨碱废液混配蒸馏水后直接溶采二层盐制备液体盐工艺中,氨碱废液与蒸馏水体积混配比例为1∶（5.55~6.36）、25 ℃、300 r/min条件下,反应120 min后分离可获得优级液体盐。     

Chemical-free graphene by unzipping carbon nanotubes using cryo-milling

Current paper reports synthesis of chemical free graphene by unzipping of the carbon nanotubes (CNTs) using high strain rate deformation at 150 K. A specially designed cryomill operating at 150 K was used for the experiments. The mechanism of unzipping was further explored using molecular dynamics (MD) simulations. Both experimental and simulation results reveal two modes of unzipping through radial and shear loading.     

Reverse osmosis applied to the recovery of water from aqueous salt solutions

A cellulose acetate membrane was applied to the study of reverse osmosis on aqueous solutions of LiCl, NaCl, KCl, CaCl₂, SrCl₂ and BaCl₂. This membrane, 71 microns thick and having an effective diameter of 1 1/2 in. was mounted within a specially constructed cell, made of stainless steel and designed to withstand pressures up to 1500 psi. The cell consisted of two chambers, which were separated by the membrane, and a porous plate supporting it. Solutions of 0·05 N, for all of these salts, were used to establish the osmotic pressure of each solution, the water fluxes through the membrane, and the extent of salt rejection. These variables were also determined for NaCl normalities of 0·2 and 0·6. On a single pass basis, the salt rejections ranged from 76% for KCl up to 95% for CaCl₂. The results are discussed in terms of the size of the hydrated cation. The water fluxes for all these solutions were found to be essentially the same and were independent of the type of salt. For solutions of 0·05 N, the water fluxes ranged from zero at the osmotic pressure up to about 44 × 10^?5 g sec^?1cm^?2 (8·8 gal day^?1ft^?2) at 800 psi and 77°F. Also, for the 0·05 N-NaCl solution, the temperature was varied from 77°F to 120°F. The results of this temperature study show that the extent of salt rejection remains essentially fixed, while the water flux at any given pressure at 120°F becomes nearly double that of 77°F.