Retention Of Fine Particles Research Articles

Polyelectrolyte titrations of synthetic mineral microparticle suspensions to evaluate charge characteristics

Colloidal charge properties were determined for a system of synthetic mineral microparticles (SMM), which have been developed to promote drainage of water and retention of fine particles during papermaking. Prior research, as well as our own preliminary research showed that the SMM system can have advantages in both of drainage and retention, compared with montmorillonite (bentonite), which is one of the most popular materials presently used in this kind of application. Streaming current titrations employing highly charged polyelectrolytes and were used to evaluate the charge properties of SMM suspensions and to understand the interactions among SMM particles, fibers, fiber fines, and cationic polyacrylamide (cPAM). Polyelectrolyte titrations were carried out under different conditions of pH to predict the charge properties of SMM under conditions that reflect paper manufacturing practices. It was found that pH variation, caused by the change of Al/Si ratio and partial neutralization of aluminum's acidity, profoundly affected the charge properties of SMM, due to the variation of Al-ions and the influence ionizable groups on the Si-containing particle surface.

A bio-engineered soft-bottom environment: The impact of Lanice conchilega on the benthic species-specific densities and community structure

This paper evaluates the effect of the tube-building, habitat structuring polychaete Lanice conchilega on the macrobenthic community and sediment characteristics of its habitat. To investigate which factors make species occur in a well-known bio-engineered habitat, macrofaunal and sedimentological data, gathered over a period of 10 years in a shallow, fine sediment bottom of the Belgian Part of the North Sea, were submitted to analyses. Both sediment composition and community structure of the associated macrofaunal matrix were affected by the presence of L. conchilega. The effect of the protruding tubes on hydrodynamics clearly resulted in the retention of fine sediment particles, while the increased coarse fraction was assumed to reflect a dynamic population build-up. This study confirmed that tube aggregations of L. conchilega expand the realized niche of several species without forming their own association. A species rank list was created according to each species' association with L. conchilega. This species rank list is extensively discussed based on all ecological knowledge available. Species are favoured by the habitat modifying ability of the polychaete tubes, which create and regulate refuge for species, alter the interactions between local species and change the physical factors of the environment. This descriptive and correlative data study examines the ecological importance of the bio-engineer L. conchilega on species level.

Approximate Analysis of Fine-Particle Retention in the Cake Filtration of Suspensions

The migration and retention of fine particles through the cake adversely affects the filtration of suspensions containing particles of different sizes. We propose a new model for describing the effect of fines retention during cake filtration under constant pressure. Cake filtration is treated as a “diffusion-like” process, while fine-particle migration and retention through the cake is described as a depth-filtration process. Fine-particle deposition results in a change in the permeability and pressure drop characteristics of the filter cake although the actual Lagrangian rate of fines deposition from the suspension is quite small. The net effect of fine particles in cake filtration can be modeled as viscoelasticity of the cake where its compressibility and resistance characteristics change with time.

Modeling simultaneous biological clogging and physical plugging in trickle-bed bioreactors for wastewater treatment

A major drawback limiting the use of trickle-bed bioreactors for biological wastewater treatment is ascribed to the concomitant biological clogging and physical plugging phenomena induced, respectively, by the formation of an excessive amount of biomass and the retention of inert suspended fine particles advected in the liquid influent stream. Biomass growth and fine particles deposition permanently reshape the bed pore structure and narrow the free interstitial space left to the fluids flow thus occasioning progressive bed obstruction often accompanied with pressure drop build-up for the cocurrent gas–liquid flows taking place in trickle-bed biofilters. In these circumstances, for maintaining acceptable operating cycles, the unit must be backwashed and/or shutdown regularly for removing the excess biomass and for cleaning from the specific solid deposit. A predictive two-dimensional dynamic model linking the two-phase flow hydrodynamics to the space-time distribution of bioclogging/biokinetics and of inert fine particles deposition via deep-bed filtration in trickle-bed bioreactors for wastewater treatment was developed. The model was based on the volume-average mass and momentum balance equations for the gas and liquid phases and continuity equation for the solid phase, the volume-average species balance for the fine particles, simultaneous transport and consumption of substrate (pollutant) and oxygen within the biofilm and collecting solid particle, and the volume-average species balance equations in the liquid and gas phases. Phenol biodegradation by Pseudomonas putida as the predominant species immobilized on activated carbon was chosen as a case study to illustrate the incidence of biomass accumulation on trickle-bed bioreactor hydrodynamics.

Effects of terracing afforestation with Pinus sylvestris L. on the physical soil properties in the Iberian Range of Soria

The methodology previously used to study the afforestations by terraces with Pinus sylvestris L. in Castilla y León is extended in this paper to study in more detail the impact on physical soil properties of the afforestations by terraces with Scots pine in the northern area of the Iberian Range of Soria. The values of soil parameters are obtained from 5 profile types: non-afforested, next to the cutting, next to the embankment, between terraces and in Scots pine mature stands, located in seven plot series, and then compared. The soil parameters are evaluated as follows: fine earth, sand, silt and clay, both in the whole profile and in the upper layer of the profile, permeability, equivalent moisture and water holding capacity of the soil profile, and erodibility. After 16-17 years, no significant changes have occurred in the physical properties that define the soil habitat of the Pinus sylvestris in Spain. Significant fine particle retention, nonoutstanding decrease of permeability, considerable improvement of water holding capacity, no increase of erodibility and progress toward ecological conditions similar to the soils with mature stands are detected, with values within those of the present central habitat of the species in Spain. Regarding to the changes in the soil physical properties, this method result appropriate for afforesting with Pinus sylvestris the above-mentioned region.

Testing procedures to assess the viability of dewatering with geotextile tubes

Geotextile tubes are finding increasing market acceptance for dewatering high water content materials. The success of this application depends on the filtration compatibility between the high water content materials and the geotextiles used to make the tubes. In this paper, 26 pressure filtration tests using four woven geotextiles of various materials were conducted to study soil retention and permeability of the sludge/geotextile system and the possible controlling factors. Based on the test results, the filter cake is not only the major contributor to the retention of fine particles, but also causes a decrease in permeability. Controlling the formation of the filter cake on the inside of the geotextiles tube and thus achieving a balance between soil retention and permeability is vital to a successful project. Surprisingly, initial water content may have a significant effect on the dewatering efficiency and dewatering rate. More testing is recommended to gain a deeper understanding into this relationship.

Deposition and retention of fine and ultrafine particles in the pulmonary region of human lungs. Normal and pathological cases

Deposition and retention of fine and ultrafine particles in the pulmonary region of human lungs. Normal and pathological cases

Suspended Particulate Organic Matter Concentration and Export in Streams

Suspended Particulate Organic Matter Concentration and Export in Streams

Analysis of cake growth in cake filtration: Effect of fine particle retention

AbstractEquations were derived that describe the dynamics of cake growth in cake filtration, and methods for their solutions were developed. In deriving the equations, the moving boundary nature of the cake formation process and the effect of fine particle retention were considered. It was shown that fine particle retention may contribute significantly to the decrease of cake permeability and thus alters the performance of cake filtration even if the amount of fine particles involved is small. Through numerical examples, it was also demonstrated that fine particle retention in filter cakes may cause serious errors in determining the constitutive relationships from filter test data.

クラウンの保持力に関する研究 合着用グラスアイオノマーセメントの粉末粒度の微細化がクラウンの保持力に及ぼす影響について

When cementing a crown, the amount of final seating is affected by the film thickness of the dental cement. To decrease the film thickness of glass ionomer cement (GIC), a GIC powder (Shofu Hybond Glass ionomer CX) was milled and three experimental fine particle powders were produced. The purpose of this study was to investigate the physical properties of fine particle GICs (ISO-9917, compressive strength, setting time, film thickness) and retention force of the crown cemented. The powder was milled with Centrifugal Fluidized Milling Machine (CF-160 Ube Kousan Co.) to produce the particle size (CX-01: maximum particle size:∅6μm, CX-02: 8μm, CX-03: 12μm). The results were as follows: In specimen containing a large amount of fine particles (CX-01), the best seating of a crown was accomplished (total film thickness: 8.0μm), though both compressive strength and film thickness was reduced to some extent. On the other hand, there was no significant difference between the retention force of normal GIC and fine particle cement (CX-01, 02, 03). The setting time of CX-01, 02, 03 was slightly longer than that of normal GIC.

Magnetic cage filters

A new class of magnetic filters-magnetic cage filters (MCFs)-was designed and constructed. These filters were studied theoretically and experimentally as far as the capture and retention of fine particles of crud is concerned. High values of capture efficiency and retention capacity were obtained, making the MCFs well suited as passive magnetic filters for power station applications. >

Morphology and Function of the Digestive-Tract in New Guinean Possums

The digestive tracts of preserved specimens of six species of New Guinean pseudocheirid (ringtail) possums (body mass 148-1250 g) and four species of New Guinean phalangerids (cuscuses) (730-2400 g) were compared. A preliminary study on Australian common ringtail possums (Pseudocheirus peregrinus) suggested that, within certain limits, data from preserved material were applicable to fresh specimens. The New Guinean ringtails were primarily folivorous, but the diet of the two smallest species contained more non-leaf material and was of higher quality, on the basis of higher (P<0.05) nitrogen levels in their gastric contents. Like P. peregrinus, New Guinean ringtail possums selectively retain fine feed particles and bacteria in their caecum, and may also be caecotrophic. The New Guinean phalangerids are less specialised in their diets, taking a wide range of leaves, bark and fruits. There was no evidence for caecotrophy or selective retention of bacteria in their caecum, but there was evidence for selective retention of fine feed particles. In the latter characteristic they differ from the Australian phalangerid Trichosurus vulpecula (the common brushtail possum).

Pulmonary retention of ultrafine and fine particles in rats.

In aerosol research, particle size has been mainly considered in the context of the role it plays in particle deposition along the respiratory tract. The possibility that the primary particle size may affect the fate of particles after they are deposited was explored in this study. Rats were exposed for 12 wk to aerosolized ultrafine (integral of 21 nm diameter) or fine (integral of 250 nm diameter) titanium dioxide (TiO2) particles. Other rats were exposed to TiO2 particles of various sizes (12, 21, 230, and 250 nm) by intratracheal instillation. After the rat lungs were extensively lavaged, analysis of particle content in the lavaged lungs, lavage fluid, and of lymphatic nodes was performed. Electron and light microscopy was also performed using unlavaged lungs. Both acute instillation and subchronic inhalation studies showed that ultrafine particles (integral of 20 nm) at equivalent masses access the pulmonary interstitium to a larger extent than fine particles (integral of 250 nm). An increasing dose in terms of particle numbers and a decreasing particle size promoted particle access into the interstitium. The translocation of particles into the interstitium appeared to be a function of the number of particles, and the process appeared to be related to the particle size, the delivered dose, and the delivered dose rate. A net effect of the preferential translocation of the smaller particles into the interstitium was a prolongation in their lung retention. After the 12-wk inhalation exposure, pulmonary clearance of ultrafine particles was slower (t1/2 = 501 days) than of larger particles (t1/2 = 174 days).(ABSTRACT TRUNCATED AT 250 WORDS)

Digesta retention and fibre digestion in brushtail possums, ringtail possums and rabbits

1. 1. Mean retention times (MRTs) of fluid (marked with Co-EDTA), fine particles (mordanted with Yb) and large particles (mordanted with Cr) were measured in brushtail possums ( Trichosurus vulpecula), ringtail possums ( Pseudocheirus peregrinus) and laboratory rabbits fed semipurified diets. 2. 2. In brushtail possums there were no significant differences in MRT among the three digesta markers. 3. 3. In ringtail possums MRTs of the fluid and fine particle markers were approximately twice that of the large particle marker, indicative of selective retention of both fluid and fine particles in the caecum. 4. 4. In the rabbit MRT of fine particles was also greater than that of large particles, again indicative of selective retention of fine particles in the caecum. 5. 5. Fibre digestibility was greater in the rabbits than in the ringtail possums, and greater for neutral-detergent fibre (including agar) but less for acid-detergent fibre in the rabbits than in the brushtails. Differences in fibre digestibility between brushtails and rabbits were explained by differences in patterns of digesta flow. However, the higher digestibilities of fibre in the rabbits than in the ringtail possums could not be explained on a similar basis.

Lung Clearance of Inhaled Insoluble and Soluble Particles

Lung Clearance of Inhaled Insoluble and Soluble Particles

Nitrogen Requirements and Urea Metabolism in Two Arboreal Marsupials, the Greater Glider (Petauroides volans) and the Brushtail Possum (Trichosurus vulpecula), Fed Eucalyptus Foliage

Maintenance nitrogen requirements (MNRs) were determined in greater gliders fed Eucalyptus radiata foliage and in brushtail possums fed E. melliodora foliage. Both species had high nitrogen requirements compared with most other marsupial species; the greater glider required 0.56 g truly digestible nitrogen · kg−75 · day−1 and the brushtail possum 0.42 g · kg−0.75 · day−1 to remain in zero nitrogen balance. The loss of nitrogen as ammonia in the urine was the major reason for the high nitrogen requirement of the greater glider. In contrast, excretion of fecal nitrogen, especially nondietary fecal nitrogen (NDFN), was responsible for the higher MNR of the brushtail possum, compared with previous estimates. This high NDFN excretion was partly attributable to the lack of selective retention of fine particles, including microbial cells, in the hindgut. Both species recycled large proportions of endogenously synthesized urea to the gut, but urea-synthesis rates were low compared with those found in other herbivores fed low-protein diets.

Koala (Phascolarctos cinereus) dentition and nutrition. II. Implications of tooth wear in nutrition

The Koala has a greatly expanded caecum and colon where some fermentation appears to take place and where selective retention of fine particles and solutes takes place. Nutrient availability in the small intestine and rate of fermentation is affected by particle size, which in turn is dependent on mastication. The efficiency of mastication over the life of the animal is affected by tooth wear. When expressed as a function of a composite tooth wear class of a tooth row, the length of the occluding enamel edges increases to a peak then declines with extreme wear. The morphology of the teeth and the pattern of dentine exposure are important factors in the maintenance of effective occlusal morphology. Animals with very worn teeth have much larger particles and a greater proportion of these present in the stomach than animals with unworn teeth. However, the increased proportion of large particles in the stomach of older animals is accompanied by only a slight increase in the percentage of the largest size class within the caecum. Thus old animals still maintain some selective retention of fine particles as distinct from large particles in the hind gut, even though the dentition produces a lower proportion of these. This is probably achieved by an increased intake and gut passage rate.

Enzymes immobilized on a magnetic support: Preliminary study of a fluidized bed enzyme reactor

Enzymes were immobilized on a magnetic support by a cocross-linking method with an inactive protein. Active porous particles obtained were used in a fluidized bed reactor. Outlet product concentration was measured as a function of a flow rate and inlet substrate concentration. No enzyme leakage was observed and a circular magnet surrounding the column was shown to be an efficient device for the retention of fine particles.