Cellulosic fibers, as the most abundant biopolymer on earth, are attracting more and more interesting to be absorbent for ion removal from aqueous solution due to its biodegradability and ...renewability. In this paper, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride was used as functional agent to modify the cellulosic fibers to be absorbent for Cr (VI) in aqueous solution. Our attention in this work was aimed at the influence of mechanical refining treatment before graft on the modification as well as the absorption capability of modified fibers. The modification was carried out using refined fibers and raw fibers. The modified fibers were verified by IR analysis. The results showed that in isopropyl alcohol solution and under alkaline condition, the functional agent can be grafted onto fibers. The mechanical refining treatment of cellulosic fibers before modification can improve the grafting efficiency. The absorption capability of modified treated-fibers for Cr (VI) from aqueous solution is higher than that of modified untreated-fibers. More hydroxyl groups on the surface of fibers after mechanical refining treatment is the reason for higher absorption capability of modified treated-fibers and higher grafting efficency.
The β-O-4 type model compound guaiacylglycerol-β-guaiacyl ether was treated with a Violuric acid (VIO) mediated electrochemical delignification system. GC-MS analysis were used to investigate the ...changes of chemical structure of β-O-4 type model compound during reaction. Mechanism of this electrochemical delignification was also explored. Results indicated that the electrochemical oxidation by VIO as a mediator had strong oxidation capability on degradation of β-O-4 type model compound. After degradation, a series of aromatic compounds containing single benzene ring, furan compounds and aliphatic compounds with small molecule were produced. From their structures, the following reactions were caused by electrochemical oxidation: ether-bond cleavage, Cα-Cβ cleavage and benzene ring cleavage. Corrsequently, this work provides a comprehensive information on electrochemical oxidation delignification system that could be applied to industrial nonpollution bleaching.
The β-O-4 type model compound guaiacylglycerol-β-guaiacyl ether was treated with a Violuric acid (VIO) mediated electrochemical delignification system. GC-MS analysis were used to investigate the ...changes of chemical structure of β-O-4 type model compound during reaction. Mechanism of this electrochemical delignification was also explored. Results indicated that the electrochemical oxidation by VIO as a mediator had strong oxidation capability on degradation of β-O-4 type model compound. After degradation, a series of aromatic compounds containing single benzene ring, furan compounds and aliphatic compounds with small molecule were produced. From their structures, the following reactions were caused by electrochemical oxidation: ether-bond cleavage, Cα-Cβ cleavage and benzene ring cleavage. Corrsequently, this work provides a comprehensive information on electrochemical oxidation delignification system that could be applied to industrial nonpollution bleaching.
Dry strength additives play an important roll in papermaking process. In this work, we aimed at analyzing the performance of poly vinyl alcohols (PVA) and PVA & cationic starch (CS), as dry strength ...additives, on the properties of high-yield pulp (HYP). Various dosages of PVA were applied on HYP under various conditions and the corresponding pulp properties were evaluated. It was observed that PVA increased the strength properties of the HYP significantly, and the enhanced strength properties can be kept even after refining, which gave a promising application of this method in conventional pulping process. The best conditions of PVA for dosage, pH, pulp consistency and time was 20 mg/g, 6.0, 3% and 10 min, respectively. The application of CS, combined with PVA, can further improve the final physical strength properties of HYP. The results obtained from using PVA & CS were more effective than those obtained from using only PVA.
Alkali hydrolysis was used as a method of decomposing hemicellulose in corn stalk in this paper. The effects of NaOH concentration, hydrolysis time and hydrolysis temperature in the pretreatment on ...the degradation of hemicellulose in corn stalk were investigated. In addition, the yields of reducing-sugar and alkali hydrolysis corn stalk were discussed. The experimental results showed that the process of alkali hydrolysis had positive effect on the removal of hemicellulose in corn stalk and the whole process almost finished in 3h. The maximum reducing-sugar yield was 7.2% by the pretreatment with 20% NaOH for 6 h at 90°C, and 6.6% under the condition of 15% NaOH for 3h at 90°C, which was slightly lower than the maximum reducing-sugar yield, but the alkali charge and hydrolysis time dramatically reduced. So it was clarified that the best pretreatment condition was 15% NaOH for 3h at 90°C, and also this method is easy to applied in the alkaline pulping process.
The violuric acid mediated chemical delignification system has a high delignification efficiency for pulp fibers and high delignification selectivity. The process conditions and effectiveness were ...carried out.The kinetics of electrochemical delignification has been investigated using the violuric acid (VIO) as the mediator. The reaction orders with respect to delignification, concentration of VIO and voltage of electrolytic cell were determined experimentally, which were dependent on the reaction conditions. The kinetic equation of electrochemical delignification and estimation function of kappa number were obtained respectively as follows: - dK/dt = A e-VI1.0312.197K6.25 , E=16.2KJ/mol, K(t)={2.89×10-7+5.25k VI1.0312.197t}-0.19.
The layer-by-layer deposition technique was adopted in this paper to improve the physical strength properties of alkaline peroxide mechanical pulp (APMP). The cationic starch (CS), anionic ...polyacryamide (APAM) and cationic polyacryamide (CPAM) were chosen and used to build-up polyelectrolyte multilayers on surface of APMP fibers. The improvements of physical strength of pulp through adsorption of different polyelectrolyte onto fibers were discussed and compared. The results showed that when the APMP fibers were treated with CPAM, the breaking length and burst index were 53% and 83% respectively, higher than that of untreated pulp. The optimal treatment conditions are 60 mgCPAM/g pulp, 1.5% pulp concentration and 9min treatment time. The pulp deposited by CPAM-APAM polyelectrolyte multilayer gave a highest physical strength compared with pulp with other multilayer deposition such as CS-APAM. At the whole beating degree range investigated in this paper, the CPAM-APAM deposition on fiber surface can improve the physical strength properties significantly, especially when the beating degree is at 40oSR. In addition, the improvement of physical strength can be remained even after pulp refining.
The catalyst in the oxygen electrode is the core component of the aqueous metal-air battery, which plays a vital role in the determination of the open circuit potential, energy density, and cycle ...life of the battery. For rechargeable aqueous metal-air batteries, the catalyst should have both good oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic performance. Compared with precious metal catalysts, non-precious metal materials have more advantages in terms of abundant resource reserves and low prices. Over the past few years, great efforts have been made in the development of non-precious metal bifunctional catalysts. This review selectively evaluates the advantages, disadvantages and development status of recent advanced materials including pure carbon materials, carbon-based metal materials and carbon-free materials as bifunctional oxygen catalysts. Preliminary improvement strategies are formulated to make up for the deficiency of each material. The development prospects and challenges facing bifunctional catalysts in the future are also discussed.
Different types of advanced non-noble materials in bifunctional catalysts for ORR and OER.
The discovery of new halide perovskite-type structures could favor the exploration of optoelectronic materials, as in the case of double perovskites applied in solar cells, light-emitting diodes, and ...X-ray detectors. In this work, we propose a strategy for designing quadruple perovskites by heterovalent cation transmutation from double perovskites. Two stable quadruple perovskite halides, i.e., Cs4CdSb2Cl12 and Cs4CdBi2Cl12, with a vacancy-ordered three-dimensional (3D) crystal structure were predicted through symmetry analysis and density functional theory (DFT) calculations. The title perovskite halides are also electronically 3D with direct forbidden bandgaps. Following the indication provided by the DFT results, Cs4CdSb2Cl12 and Cs4CdBi2Cl12 as unique quadruple perovskites were successfully synthesized by a solvothermal method. The steady-state photoluminescence (PL) shows wide emission, while the transient PL exhibits carrier recombination lifetime on the order of microseconds at low temperature. The quadruple perovskite halides provide an alternative platform for promising optoelectronic material design in addition to simple and double perovskites.
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