Isolation and Characterization of Cellulosic Pulp Fines and Their Interactions with Cationic Polyacrylamides

Four different types of cellulosic fines were isolated from refiner mechanical and kraft pulp samples to characterize their chemical and physical properties. The pulp fines were flocculated using four different types of cationically modified polyacrylamides. The extent of flocculation was observed with multiple light scattering apparatus. The maximum adsorption of the polyelectrolytes on the pulp fines was determined by polyelectrolyte titration. It was concluded that it is the combination of the molar mass and the charge density of a polyelectrolyte, as well as the origins and characteristics of the fines which define the adsorption and flocculation behavior. None of these properties alone could fully describe these phenomena, but the molar mass of the polyelectrolyte was the predominant factor. The most important fines characteristics were the charge properties and the microstructure.     

熔融X射线荧光光谱法测定高炉返粉组份

建立了X射线荧光光谱法测定高炉返粉中化学成分的方法,采用高温熔融法将试样制成玻璃状体,消除了基体干扰;通过对熔样条件、干扰元素、仪器参数、工作曲线拟合方式等方面进行实验研究,确定了最佳分析条件,实现了高炉返粉中主要成分SiO2等8种成分的同时测定,方法具有准确度高、同时测定多元素、分析速度快等特点。     

Stochastic and upscaled analytical modeling of fines migration in porous media induced by low-salinity water injection

Fines migration induced by injection of low-salinity water(LSW) into porous media can lead to severe pore plugging and consequent permeability reduction. The deepbed filtration(DBF) theory is used to model the aforementioned phenomenon, which allows us to predict the effluent concentration history and the distribution profile of entrapped particles. However, the previous models fail to consider the movement of the waterflood front. In this study, we derive a stochastic model for fines migration ...     

Properties and treatments of pulps from recycled paper. Part II. Surface properties and crystallinity of fibers and fines

Surface properties of bleached kraft pulps were evaluated before and after recycling, and after a series of chemical treatments designed to improve and/or modify the pulp characteristics. The surface free energy characteristics of the pulps were determined using the Wilhelmy technique, and ESCA and ATR-FTIR methods were used to evaluate the chemical composition of the surfaces of the pulp fibers. In general rather small changes were noted at the fiber surfaces with recycling and chemical treatment. Recycling tended to increase the acid component and decrease the base component of the surface free energy of the pulps. This could result from exposure of carboxyl groups from hemicelluloses and/or from oxidized layers from the bleaching process. ESCA analyses also indicated increased carboxyl concentration at the surfaces of the recycled fibers. Although treatment with aqueous bases and organic solvents tended to increase the hydroxyl content on the surface of recycled pulps, the chemical treatments were not beneficial to pulp quality. AFM and SEM of fiber and fine surfaces of kraft pulps revealed that the fines fraction was altered to a much greater extent with recycling. Although recycled fibers appeared to have improved wettability, these small changes in the surface characteristics do not appear to play the dominant role in the characteristics of recycled pulps. Recycling did not change the crystallinity of whole pulps, but it increased the crystallinity of the fines fraction. The increase in the crystallinity of the fines fraction and the reduction in the water retention value (WRV) and the bulk carboxyl content (xylan) of the recycled pulps, as noted in Part I of this paper, appear to play the predominant role in determining the characteristics of recycled pulps. It appears that the loss of the hemicelluloses in the bulk of the fiber with recycling is much more important for internal fibrillation than the apparent small increase of hemicelluloses at the surface of recycled fibers.     

Bioconversion of secondary fiber fines to ethanol using counter-current enzymatic saccharification and Co-fermentation

This research examined several enzymatic and microbial process for the conversion of waste cellulosic fibers into ethanol. The first was a one-stage process in which pulp fines were contacted with commercial enzyme solutions. The second process used sequential, multistage saccharification. The third used sequential enzyme addition in a countercurrent mode. Experiments compared the results with various feed stocks, different commercial enzymes, supplementation with β-glucosidase, and saccharification combined with fermentation. The highest saccharification (65%) from a 4% consistency pulp and the highest sugar concentration (5.4%) from an 8% consistency pulp were attained when 5 FPU/g plus 10 IU/g of β-glucosidase were used. Sequential addition of enzyme to the pulp in small aliquots produced a higher overall sugar yield/U enzyme than the addition of the same total amount of enzyme in a singledose. In the saccharification and fermentation experiments, we produced 2.12% ethanol from a 5.4% sugar solution. This represents 78% of the theoretical maximum. This yield could probably be increased through optimization of the fermentation step. Even when little saccharification occurred, the enzyme facilitated separation of water, fiber, and ash, so cellulase treatment could be an effective means for dewatering pulp sludges.     

ON AVOIDANCE ACTIVITIES IN FISHERY ENFORCEMENT MODELS

Compliance and enforcement in fisheries are important issues from an economic point of view since management measures are useless without a certain level of enforcement. These conclusions come from the well‐established theoretical literature on compliance and enforcement problems within fisheries and a common result is that, it is efficient to set fines as high as possible and monitoring as low as possible, when fines are costless and offenders are risk neutral. However, this result is sensitive to the assumption that fishermen cannot engage in avoidance activities, e.g., activities to reduce the likelihood of being detected when noncomplying. The paper presents a model of fisheries that allows the fishermen to engage in avoidance activities. The conclusions from the model are that, under certain circumstances, fines are costly transfers to society since they not only have a direct positive effect on the level of deterrence, but also an indirect negative effect in the form of increased avoidance activities to reduce the probability of detection. The paper contributes to the literature on avoidance activities by introducing the externality from the illegal behavior as an endogenous effect on other offenders. For an externality, that has an exogenous effect on other actors, Malik shows that fines are only costly transfers for conditional deterrence (when one actor is deterred while another actor is not). For fisheries, we show that fines are also costly transfers under no deterrence (when no agents are deterred).     

Effect of Nanofluid Treatment on Water Sensitive Formation to Investigate Water Shock Phenomenon,An Experimental Study

Permeability reduction in porous media as a result of frail and tenuous fine particles migration would decrease the productivity index in the subterranean reservoirs. During reservoir stimulation by injecting fluids into the reservoir, as the salinity condition of the formation brine changes, fine particles initiate the triggering process. In this study, MgO-based nanofluid as a fines fixation agent was stably prepared based on the particle size distribution and characterized through transmission electron microscopy analysis. Afterward, several core flooding tests were performed using Berea sandstone cores to study the effect of nanofluid injection on fines fixation in the water shock phenomenon. Permeability reduction occurred up to 95% of inchoate permeability for no treatment case, which was also confirmed by scanning electron microscopy analysis. Finally, MgO nanofluid with 0.03 wt% concentration and 120 minutes soaking time in the core mitigated the fine particles release and fixed them on the pore walls' surfaces critically reducing the formation damage. The analysis shows that outweighing the attraction potentials compared to repulsions was the main mechanism after nanofluids treatment.     

Removal of Small Particles from a Porous Material by Ultrasonic Irradiation

A study has been made of the removal of small particles from a porous material by means of ultrasonic irradiation. To that purpose a microscopic theoretical model has been developed to calculate the force of a traveling acoustic wave on a spherical particle attached to the wall of a smooth, cylindrical pore inside the porous material. This force was compared with the adhesion force between a small particle and a pore wall. From the comparison between the two forces the conditions were found, at which particles are detached from pore walls and removed from the porous material. The transformation of the results gained from the microscopic model to macroscopic property (permeability) of the porous material was made by means of the Kozeny relation. The aim is to be able to understand and predict qualitatively the influence of relevant parameters on the ultrasonic cleaning process. Predictions made with the theoretical model were compared with data from experiments carried out with ultrasound to remove particles from Berea sandstone. The agreement is reasonable.     

Multiferroic RMnO3 thin films

Multiferroic materials have received an astonishing attention in the last decades due to expectations that potential coupling between distinct ferroic orders could inspire new applications and new device concepts. As a result, a new knowledge on coupling mechanisms and materials science has dramatically emerged. Multiferroic RMnO₃ perovskites are central to this progress, providing a suitable platform to tailor spin–spin and spin–lattice interactions.With views towards applications, the development of thin films of multiferroic materials have also progressed enormously and nowadays thin-film manganites are available, with properties mimicking those of bulk compounds. Here we review achievements on the growth of hexagonal and orthorhombic RMnO₃ epitaxial thin films and the characterization of their magnetic and ferroelectric properties, we discuss some challenging issues, and we suggest some guidelines for future research and developments.