The Influence of CO_(2) Cured Manganese Slag on the Performance andMechanical Properties of Ultra-High Performance Concrete

The presence of toxic elements in manganese slag(MSG)poses a threat to the environment due to potential pollution.Utilizing CO_(2) curing on MS offers a promising approach to immobilize toxic substances within this material,thereby mitigating their release into the natural surroundings.This study investigates the impact of CO_(2) cured MS on various rheological parameters,including slump flow,plastic viscosity(η),and yield shear stress(τ).Additionally,it assesses flexural and compressive strengths(f_(t) and f_(cu)),drying shrinkage rates(DSR),durability indicators(chloride ion migration coefficient(CMC),carbonization depth(CD)),and the leaching behavior of heavy metal elements.Microscopic examination via scanning electron microscopy(SEM)is employed to elucidate the underlying mechanisms.The results indicate that CO_(2) curing significantly enhances the slump flow of ultra-high performance concrete(UHPC)by up to 51.2%.Moreover,it reduces UHPC’sηandτby rates ranging from 0%to 52.7%and 0%to 40.2%,respectively.The DSR exhibits a linear increase corresponding to the mass ratio of CO_(2) cured MS.Furthermore,CO_(2) curing enhances both f_(t) and f_(cu) of UHPC by up to 28.7%and 17.6%,respectively.The electrical resistance is also improved,showing an increase of up to 53.7%.The relationship between mechanical strengths and electrical resistance follows a cubic relationship.The CO_(2) cured MS demonstrates a notable decrease in the CMC and CD by rates ranging from 0%to 52.6%and 0%to 26.1%,respectively.The reductions of leached chromium(Cr)and manganese(Mn)are up to 576.3%and 1312.7%,respectively.Overall,CO_(2) curing also enhances the compactness of UHPC,thereby demonstrating its potential to improve both mechanical and durability properties.

纳米纤维素催化氧化玉米淀粉基复合膜的制备

以酸水解制备的纳米纤维素作为催化剂制备次氯酸钠氧化淀粉,并将制备的氧化淀粉与不同添加量聚乙烯醇(PVA)/甘油(GL)共混,采用流延成膜法制备复合膜。通过红外光谱分析了复合膜的官能团变化,扫描电镜进行表面形貌分析,热重分析和差示扫描量热法表征复合膜的热稳定性。同时用静态接触角测量仪、近红外紫外分光光度计分别研究了复合膜的疏水性和透明度,用张力测试机检测了复合膜的力学性能。研究发现,复合膜中PVA/GL的添加量对复合膜的透明度、热稳定性、阻水性和力学性能均产生影响,在PVA添加量为15%(GL添加量9.375%)时,复合膜的透明度为0.67,接触角达最高值100°,拉伸应力为12.89 MPa,复合膜的性能较优。

Application of Cellulose Nanofibril as a Wet-end Additive in Papermaking:A Brief Review

Recently,cellulose nanofibril(CNF)has emerged as a promising,sustainable reinforcement with outstanding potential in material science.Owing to the properties of CNF,it has been explored in food,cosmetic,and pharmaceutical applications,as well as in industrial applications such as paints,drill muds,packaging,and papermaking.The application of CNF in papermaking is expected to be implemented in the near future to broaden the commercial market of cellulose.Numerous studies and patents have reported on the manufacturing,properties,and applications of nanocellulose.This present paper focuses on the recent progresses in the application of CNF as a wet-end additive in papermaking.

Influence of Chemical Pretreatment on the Dissolved Organics in Poplar Alkaline Peroxide Mechanical Pulping Effluent

The components of the effluent from the chemical pretreatment of poplar alkaline peroxide mechanical pulp(APMP) were analyzed in this study. The main dissolved organics were low-molecular weight(LMW) lignin, oligosaccharides, and monosaccharides. The lignin and sugar concentrations in the effluent obtained using different chemical pretreatment conditions and chemical dosages were analyzed using ultraviolet(UV) spectroscopy. This analysis provided a theoretical basis for the subsequent treatment and utilization of APMP effluent. The experimental results showed that the dosages of Na OH, H_2O_2, and Na_2 SiO_3 in the chemical pretreatment process affected the lignin and sugar concentrations in the effluent and that different chemicals had differing degrees of influence. The degree of influence exhibited the following order: Na OH>H_2O_2>Na_2SiO_3. More specifically, the dosages of Na OH and H_2O_2 had stronger influences on the lignin and sugar concentrations than that of Na_2 SiO_3. Indeed, the Na_2 SiO_3 dosage hardly affected the lignin and sugar concentrations in the effluent, but Na_2 SiO_3 could stabilize the chemical pretreatment system and improve the reactive efficiency of Na OH and H_2O_2. The pretreatment temperature and time also affected the organic components, and the influence of the temperature was stronger than that of time.

Nanofibrillation of a Bleached Acacia Pulp by Grinding with Carboxymethylation Pretreatment

In this study,carboxymethylation,which introduces carboxyl groups to hydroxyl sites in pulp fibers,was used as a pretreatment before mechanical nanofibrillation.The carboxyl group content of the pulp fibers was greatly affected by the dosage of chloroacetic acid and the reaction temperature.During the following fibrillation process,it was found that pulp fibers with higher carboxyl group content exhibited higher water holding capacities and smaller dimensions.A more homogenous structure with a higher amount of individual fibrils was also observed in FE-SEM images of pulp fibers with high carboxyl group content.This can be explained by a high ionic group content in the fiber wall resulting in lower delamination resistance,making the fibrils easier to separate.Carboxymethylation pretreatment as a facilitator of fibrillation in cellulosic pulps is an efficient way to obtain cellulose nanofibrils and consequently decrease the energy consumption of the process.

Efficient utilization of lignocellulosic resources on the basis of pulp and paper processes

Background Efficient utilization of lignocellulosic resources for producing fuels,materials,and platform chemicals through bioconversion processes has attracted overwhelming attention.Conventional pulp and paper industry consumes a huge amount of lignocellulosic resources,but their values are not fully exploited.Fractionation/bioconversion of the main components of lignocellulose for producing diversified products besides pulp and paper is a promising strategy to efficiently utilize lignocellulosic resources.

Wet oxidation of activated carbon for enhanced adsorptive removal of lignin from the prehydrolysis liquor of kraft-based dissolving pulp production in an integrated forest biorefinery

Prehydrolysis is a key step for the production of kraft-based dissolving pulp.The pre-hydrolysis liquor mainly contains hemicellulosic components.Lignin can also be released into the pre-hydrolysis liquor,which hinders the purification and utilization of these hemicellulosic components.In this work,wet oxidation of activated carbon with nitric acid was employed to enhance the adsorptive removal of lignin from the pre-hydrolysis liquor.Under mild oxidation conditions(2%nitric acid solution),the oxidization of activated carbon resulted in significant enhancement of lignin removal.Adsorption isotherms showed that the specific surface area and the amount of carboxyl groups were affected by the oxidation treatment.The selective removal of lignin fitted well with the pseudo-second order kinetics model.

Enzymatic activation of dissolving pulp with cationic polyacrylamide to enhance cellulase adsorption

Cellulase treatment is a promising technology to improve the properties of dissolving pulp in an environmental friendly way.Increasing the cellulase treatment efficiency is of practical interest.In the present study,the concept of using cationic polyacrylamide(CPAM)to enhance the cellulase treatment efficiency was demonstrated.The hypothesis was that the CPAM would attribute to the increased cellulase adsorption onto cellulose fibers based on the patching/bridging mechanism.Results showed that the viscosity decrease was improved with the addition of 250 ppm of CPAM under the same conditions as those of the control.Degraded cellulose content was increased based on the alkaline solubility analysis,while alpha-cellulose content kept constant.The CPAM-assisted cellulase treatment concept may provide a practical alternative method for upgrading dissolving pulp.