Pressure Filtration Technique Research Articles

Fabrication and separation performances of composite membranes containing copper ferrite photocatalysts on graphene oxide nanosheets

An innovative approach thatintegrates photocatalysis, adsorption, and membrane separation processes was presented to degrade pollutants simultaneously during the filtration process. Firstly, a one-pot method was employed to prepare 3D graphene oxide/carbon quantum dot/copper ferrite (G/CFQ) photocatalysts. Then, the M−G/CFQ membrane was fabricated by intercalating 3D G/CFQ photocatalysts between 2D graphene oxide (GO) nanosheets using a negative pressure filtration technique. The time-dependent flux and MB residual rate results revealed that the M−G/CFQ membrane exhibited superior photocatalytic capabilities, particularly in alkaline environments. Furthermore, M−G/CFQ, when used without reaching adsorption saturation and under illumination, displayed outstanding long-term operational catalytic degradation capabilities. For a 5 ppm methylene blue (MB) solution at pH of 7, 10, and 12, the filtrate residue rates were only 8.63 %, 4.44 %, and 1.61 % respectively within 6 h. The versatility, stability, and exceptional properties of M−G/CFQ make it a promising candidate for large-scale water treatment applications, contributing significantly to the conservation of clean water resources and environmental sustainability.

Effect of powder dispersion on sintering behavior and mechanical properties of nanostructured 3YSZ ceramics

The aim of this work was to investigate the feasibility of producing dense nanostructured ceramics from commercial zirconia nanopowder by colloidal processing. Our study has demonstrated the adverse effect of the presence of aggregates in the production of nanostructured components. Two techniques were employed to remove aggregates – centrifugation and high energy milling. The finer powder thus produced by centrifugation and/or high energy milling, with an average size of particles around 60–70nm was consolidated into a green body by a relatively simple low pressure filtration technique (300kPa). It was possible to prepare green bodies of 47% density with relatively fine and uniform size pores from suspensions containing these powders. The green compacts obtained from finer powder could be sintered to fully dense nanostructured products at a significantly lower temperature (1200°C) with a soaking period of 0.5h only with an average grain size of 90nm only in the sintered compact. In contrast the as received aggregated powder could not be sintered at all to full density even at as high temperature as 1600°C. The bulk nanostructured 3mol% yttria stabilized zirconia (3YSZ) compact with an average grain size of 110nm exhibited Vickers hardness of 12.8GPa, which is comparable to the available results in the literature.

Effect of grain refining and Sr modification on Prefil measurement sensitivity in 356 alloys using electron probe microanalysis technique

To obtain the best possible Ai–Si alloy casting, the quality of the molten alloy must be optimised, i.e. the molten metal must be free of inclusions, impurities and dissolved gases during the casting process. The cleanliness of the molten metal can be monitored by means of various filtration techniques such as the Prefil (pressure filtration) technique used in the present study. Two melt treatment processes also generally applied to Al–Si alloys to improve the cast microstructure and alloy properties are grain refining and modification. However, the addition of grain refiners (in the form of Al–Ti–B master alloys) or modifiers (in the form of Al–Sr master alloys) to the melt can affect the behaviour of the inclusion measurement system. The present work was carried out on A356 alloys to study the effect of such additions when using the Prefil technique (additions of Ti, B or Sr can skew the Prefil filtration curve and make it less effective). The Prefil experiments were carried out using two types of ceramic filters: standard permeability (SP) filters with an average filter pore size of ~90 μm, and high permeability (HP) filters with an average filter pore size of ~130 μm. The results show that the Prefil curves obtained from the high permeability filters are more sensitive to the presence of oxides (film or particles) than the standard filters. The filtration rate is greatly affected by the amount of grain refiner added. Best results are obtained for the alloy without grain refiner addition. The filtration rate progressively decreases with increasing amount of grain refiner. When the total amount of boron added to the melt (through the Al–5Ti–1B grain refiner used) reaches 60 ppm, the filtration rate is approximately nil. In the case of strontium modification, a reasonably good correlation between the amount of Sr in the molten metal and the Prefil curve (or 'footprint') has been established. However, more experiments are still needed for a better understanding of the effect. Oxidation of Sr is possible, even for concentrations as low as 30 ppm. The SrO oxide particles (white, round shaped) are always seen to be associated with Al2O3 oxide particles (observed in the form of dark short rods). The curvature of the Prefil footprint is found to be sensitive to the amount of oxides present.

Dewatering properties of dual-polymer-flocculated systems

This work examines the effect of dual-polymer flocculation on the compressive yield stress and hindered settling function of positively charged alumina suspensions as measured by a pressure filtration technique. The primary aggregates were formed using a short-chain poly(acrylic acid) (PAA) under two different shear mixing conditions at pH 5. This resulted in two types of aggregates with different mass fractal dimension and size. These aggregates were further flocculated using either a cationic or an anionic long-chain polymer at the same pH. A filtration study of these dual-polymer-induced aggregates showed that there may exist an optimum dosage for the second polymer, which results in the lowest final cake moisture. Dual-polymer flocculation was found to result in lower compressive yield stresses than that found for the case of single, high-molecular-weight polymer flocculation. This gave rise to lower final cake moistures for the dual-polymer-flocculated systems (28.3% w/w) compared to the case of the single, high-molecular-weight polymer-flocculated system (34.7% w/w). The filtration rate was high for the dual-polymer systems in most cases. In addition, the polymer dosage required to achieve good supernatant clarity was decreased from that of the single-polymer case when dual polymers were used. The use of dual-polymer flocculants of opposite charge was found to give an improvement in final cake moisture over that achieved using dual polymers of like charge. The structural characteristics of the primary aggregates were also found to have a significant influence on the dewatering properties of the dual-polymer-induced aggregates. Under the conditions used, large, open primary aggregates led to final flocs with lower cake moisture and faster filtration rate. It is envisaged that optimisation of industrial dewatering processes in this way can result in considerable savings in transportation and enhanced product value.

Preparation of hydroxyapatite/α-tricalcium phosphate composites by colloidal process

Synthesised hydroxyapatite ,HAp)/a-tricalcium phosphate ,α-TCP) composites were prepared by colloidal process. Mixed slurries composed of 30 vol% HAp/a-TCP powder and 70 vol% aqueous solution containing a small amount of polymer dispersant were produced. HAp/α-TCP powder was blended with 0, 0.2, 0.4 or 1.0 mass fraction of α-TCP. Rheological behaviour of the HAp/α-TCP mixed slurries depended on the quantity of polymer dispersant and pH. Addition of suitable quantity of polymer dispersant at higher pH resulted in an increase in the stability of colloidal state due to electrostatic stabilisation. The optimum quantity of dispersant for the colloidal process was found to be proportional to the mass fraction of α-TCP. In the dehydration process of the slurries, pressure filtration technique was effective in preventing the gravity segregation of α-TCP. Thus, HAp/α-TCP composites with homogeneous microstructure and high relative density could be prepared by optimising the colloidal process.

Assessment of melt cleanliness and analysis of inclusions in Al-Si alloys using the Prefil pressure filtration technique

The aluminium casting alloys A356.2 and A390.1 are two of the most popular Al-Si alloys used in automotive and die casting applications. To obtain premium quality castings, their alloy melts must possess optimum melt cleanliness, i.e., the inclusions present therein, particularly those harmful to the alloy properties, must be minimised. In recent years, melt cleanliness of aluminium alloys has been assessed by means of various filtration techniques. In the present work, the measurement of inclusions was carried out using the recently introduced pressure filtration ‘Prefil’ technique which has the advantage of providing in situ results in the form of flow rate charts. These minimise the need for time-consuming metallographic examinations for inclusion analysis demanded by other pressure filtration techniques such as PoDFA. Experiments carried out using the ‘Prefil’ technique indicate that for obtaining appropriate results, the pressure chamber and filtration crucible of the ‘Prefil’ appratus should be heated to ~300-350°C, to reduce heat loss during transfer of the liquid metal from the melt crucible to the filtration crucible. Also, the filtration temperature should be high enough to avoid possible sedimentation of inclusions in the ladle during the transfer. It was found that the main inclusions in A356.2 alloy are Al4C3, dispersed oxides, MgO and MgAl2O4, while those in A390.1 alloy are bone ash and alkaline compounds. Generation of oxide films (associated with the use of mechanical stirring to dissolve grain refiner/modifier additions to the melt) can be avoided by employing degassing instead.

Pressure Filtration Technique for Complete Characterization of Consolidating Suspensions

The behavior of suspensions in settling and compression is fully defined by two parameters: the compressive yield stress function Py(φ) and the hindered settling function r(φ). The compressive yie...

98/01862 Modified approaches for high pressure filtration of fine clean coal : Yang, J. et al. Proc. Int. Miner. Process. Congr., 19th, 1995, 2, 103–106

Removal of moisture from fine (minus 28 mesh) clean coal to 20% or lower level is difficult using the conventional vacuum dewatering technique. High pressure filtration technique provides an avenue for obtaining low moisture in fine clean coal. This paper describes a couple of novel approaches for dewatering of fine clean coal using pressure filtration which provides much lower moisture in fine clean coal than that obtained using conventional pressure filter. The approaches involve (a) split stream dewatering and (b) addition of paper pulp to the coal slurry. For Pittsburgh No. 8 coal slurry, split stream dewatering at 400 mesh provided filter cake containing 12.9% moisture compared to 24.9% obtained on the feed material. The addition of paper pulp to the slurry provided filter cake containing about 17% moisture.

Preparation of ZrO<sub>2</sub> Powders Doped with SiO<sub>2</sub> by Hydrolysis of Tetraethoxysilane

Three mol% Y2O3-doped tetragonal ZrO2 compacts with a small amount of SiO2 were prepared by the hydrolysis of Si(OC2H5)4 suspended with ZrO2 particles and using a pressure filtration technique. The SiO2 content of the compacts was successfully controlled within the range of about 0.1-1mass% by treating the ZrO2 powder with an aqueous H2SO4 solution prior to the hydrolysis of Si(OC2H5)4. The compacts doped with 0.36 and 1.22mass% SiO2 showed a high relative density of above 98% when sintered at 1300°C for 2h.

Controlling the flaw size and mechanical properties of ZTM/SiC p composites

Ultrafine mullite and zirconia powders were prepared by sol-gel and precipitation processes, then mixed homogeneously with μm-sized silicon carbide particles (SiC p) to obtain composite powder. A dense green body with homogeneous microstructure was prepared by the pressure filtration technique. After being dried carefully, the green body was hotpressed under different conditions to optimize its microstructure. The effect of different hot-pressing conditions on the mechanical properties was investigated and the hot-forging effect was also taken into account. It was found that the strength of the composite was greatly increased, from about 600 MPa reported to 810 MPa at room temperature and 830 MPa at 1000 ° C, under the conditions of moderately low hot-pressing temperature and long holding time, while the fracture toughness of the composite remained almost unchanged. From this it was shown that the control of strength-limiting processing defects was effective. Because of the homogeneous microstructure improved during forming and optimized during sintering and a combination of various strengthening mechanisms, it was possible to enhance the strength of the composite significantly.

Preparation and Sintering of Silica-Doped Zirconia by Colloidal Processing

ABSTRACTSilica-doped (SiO2= 0–1.0 mass%) zirconia (3 mol% Y2O3-doped tetragonal ZrO2) compacts are prepared from hetero-coagulated and well-dispersed suspensions by colloidal processing. The suspensions are consolidated by a pressure filtration technique. The green density of the compacts consolidated from the well-dispersed suspensions is higher than that from the hetero-coagulated suspensions. The lower density of the latter compacts is improved by a subsequent cold isostatic pressing (CIP) at 400 MPa. The sinterability of the compacts at 1200 °C is greatly affected by the amount of doped silica. The densification and grain growth are hindered by silica doping above 0.3 wt% at 1200 °C. All the compacts are densificated to a relative density of above 99% by sintering at 1300 °C for 2 h.

特集 粉末の成形・加工 アルミナ超微粉のプレッシャーフィルトレーション

Pressure filtration technique was applied for the consolidation of alumina small powders (average particle sizes of 20, 10 and 5nm). Suspensions were prepared by adding appropriate amount of polycarboxylic ammonium. Apparent density of the consolidated bodies decreased as the particle size becomes smaller, whereas the density was pressure-insensitive over applied pressure range of 1.5 to 10.0MPa. The kinetics and mechanics of the consolidation of the particles were discussed from the dehydration and consolidating rates of the suspensions. The transportation process of suspensions in consolidated layer was confirmed during all filtration processing as the rate limiting process.

Loss of Anticoagulant Effect of Heparin During Circulation of Human Blood In Vitro

Device-induced thrombogenesis was studied in an in vitro model using human blood circulated through an artificial ventricle. A new constant pressure filtration technique was used to detect circulating microemboli, the activated partial thromboplastin time (APTT) test was used to monitor the blood for the presence of anticoagulant activity of heparin, and hemolysis was quantified by measuring the plasma free hemoglobin level. Circulation of blood through a 20-ml stroke volume pneumatically driven ventricle for 6-9 h resulted in a significant reduction of APTT, indicating the loss of the anticoagulant effect of heparin. Microemboli concentration was minimal until the APTT decreased below 125 s, at which time the microemboli concentration increased rapidly. This was presumed to be due to the formation of thrombi following a decrease in heparin activity. A significant increase in hemolysis was also noted when blood was pumped. None of these changes was noted in the nonpumped control blood. Spontaneous loss of heparin activity in blood circulated by a pneumatically driven pump may have clinical implications and may help understanding of the problems associated with device-induced thrombogenesis.

Dependence of mitochondrial and cytosolic adenine nucleotides on oxygen partial pressure in isolated hepatocytes. Application of a new rapid high pressure filtration technique for fractionation.

By using a new rapid high pressure filtration technique, mitochondrial and cytosolic ATP and ADP contents were determined in isolated hepatocytes at different oxygen partial pressures. At 670 mmHg, subcellular adenine nucleotide contents and ATP/ADP ratios were comparable with values obtained with the digitonin fractionation technique. However at lower oxygen partial pressure ADP appears to be rephosphorylated during digitonin fractionation whereas with high pressure filtration fractionation rephosphorylation of ADP is avoided due to shorter fractionation times. Cytosolic and mitochondrial ATP/ADP ratios decrease if oxygen partial pressure is lowered. However the absolute values of ATP/ADP ratios depend critically on the incubation conditions. Thus incubation of hepatocytes in an oxystat system, where oxygen partial pressure is maintained constant by infusing oxygen-saturated medium and the hepatocyte suspension is continuously stirred, yields much higher subcellular and overall ATP/ADP ratios than incubation in Erlenmeyer flasks gassed with different gas mixtures and shaken in a water bath. This is ascribed to limited diffusion of oxygen from the medium into the cell if the suspension is not mixed thoroughly by stirring. The strong dependence of subcellular ATP/ADP ratios on incubation conditions indicates that oxygen may be one rate-controlling factor for oxidative phosphorylation in the intact cell.

Suspended particulate matter: collection by pressure filtration and elemental analysis by thin-film X-ray fluorescence

Thin-film X-ray fluorescence, using an energy dispersive system, allows for the determination of the major rock-forming elements (Na, Mg, Al, Si, K, Ca, Ti, Mn, Fe) in suspended phases of marine particulate matter. The method is rapid, non-destructive, entails no pre-analysis treatment of the sample, and requires as little as 25 to 50 μg of sample. Particulate samples for this and other analyses are filtered quickly and without post-collection transfer of the water sample by a simple pressure filtration technique employing standard plastic sampling bottles.