kaolinite and ferric-sulfate

The purpose of the present in vivo study was to measure the efficacy of different gingival displacement materials in achieving gingival tissue displacement and to compare the efficacy of Expasyl displacement paste (Pierre Rolland, France) and gingival displacement cord for gingival displacement.. Sixteen subjects were included in the study. Premolars were prepared to receive full veneer crown, gingival displacement was carried using gingival retraction cord and gingival displacement paste. Impression of the gingival sulcus was made. Sulcus width after displacement was measured under magnification.. The mean displacement value of sulcus width was 0.21 ± 0.01 mm for the gingival retraction cord and 0.26 ± 0.02 mm for the gingival displacement paste. 'F' test was used for statistical analysis. Difference among the two test agents was statistically significant (p < 0.01).. Gingival displacement paste showed better response in achieving horizontal displacement of the gingival sulcus than gingival retraction cord.. Gingival displacement helps in recording the unprepared tooth surface adjacent to the finish line in the impression being made, thereby helping a better marginal adaptation and emergence profile in the extracoronal restoration.

Topics: Aluminum Chloride; Aluminum Compounds; Astringents; Bicuspid; Chlorides; Crowns; Dental Impression Materials; Dental Impression Technique; Dental Veneers; Ferric Compounds; Gingiva; Gingival Retraction Techniques; Hemostatics; Humans; Kaolin; Ointments; Polyvinyls; Siloxanes; Tooth Preparation, Prosthodontic

PO4(3-) and SiO3(2-) are often used as modifier to improve stability and aggregating ability of the iron-base coagulants, however, there are few reports about their detailed comparison between the coagulation performance and mechanisms. In this study, three coagulants--polyferric phosphoric sulfate (PFPS), polysilicon ferric sulfate (PFSS), and polyferric sulfate (PFS) were synthesized; their structure and morphology were characterized by Fourier transformed infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and Scanning electron microscope (SEM). Alkali titration and Ferron species analysis were employed to investigate the hydrolysis performance and species distribution. Jar test was conducted to measure their coagulation behaviors at different dosage, pH, and temperatures in which the flocs properties were measured. The results showed that a number of new compounds were formed due to the presence of PO4(3-) and SiO3(2-). Moreover, PFPS and PFSS had similar level in Fea as well as Feb. Among them, PFPS produced more multi-core iron atoms polymer and content of Feb, and the formed flocs were larger and denser. It exhibited superior coagulation performance in terms of turbidity reduction, UV254 removal and residual ferric concentration. Jar test and floc breakage/regrowth experiments indicated other than charge neutrality, the dominated mechanism involved in PFSS was the adsorption between polysilicic acid and solution particle, while PFPS was sweeping, entrapment/adsorption resulting from larger polymer colloid of Fe-P chemistry bond.

Topics: Adsorption; Coagulants; Ferric Compounds; Flocculation; Fresh Water; Humic Substances; Hydrogen-Ion Concentration; Kaolin; Nephelometry and Turbidimetry; Silicon Compounds; Suspensions; Water Purification

Methods for monitoring particle aggregation are briefly reviewed. Most of the techniques are based on some form of light scattering and may be greatly dependent on the optical properties of aggregates, which are not generally known. As fractal aggregates grow larger their density can become very low and this has important practical consequences for light scattering. For instance, the scattering coefficient may be much less than for solid objects, which means that the aggregates can appear much smaller than their actual size by a light transmission method. Also, for low-density objects, a high proportion of the scattered light energy is within a small angle of the incident beam, which may also be relevant for measurements with aggregates. Using the "turbidity fluctuation" technique as an example, it is shown how the apparent size of hydroxide flocs depends mainly on the included impurity particles, rather than the hydroxide precipitate itself. Results using clay suspensions with hydrolyzing coagulants and polymeric flocculants under different string conditions are discussed.

Topics: Alum Compounds; Aluminum Silicates; Clay; Ferric Compounds; Flocculation; Fractals; Hydroxides; Kaolin; Light; Nephelometry and Turbidimetry; Particle Size; Scattering, Radiation; Water

A kind of Fe-polysilicate polymer, poly-silicic-ferric (PSF) coagulant was prepared by co-polymerization (hydroxylation of mixture of Fe3+ and fresh polysilicic acid (PS)), in which PSF0.5, PSF1 or PSF3 denotes Si/Fe molar ratio of 0.5, 1 or 3, respectively. The effects of Si/Fe ratio and reaction time (co-polymerization time or aging time) on the reaction mode between Si and Fe were studies, and the optimal species of PSF was evaluated by pH change during the preparation of PSF and coagulation tests. The results showed that the characteristics of PSF are largely affected by both reaction time and Si/Fe ratio. PSF is found to be a essential complex of Si, Fe, and many other ions. The reaction mode between Si and Fe differs with various Si/Fe ratios. The pH of PSF0.5, PSF1 or PSF3 tended to be stable when reaction time is 10, 25 or 55 min, respectively, which is almost consistent with the time reaching the relative stable morphology that is just the optimal species of higher coagulation efficiency. The optimal reaction time reaching optimal species can be evaluated by measuring the pH change during the polymerization process.

Topics: Ferric Compounds; Flocculation; Humic Substances; Iron; Kaolin; Polymers; Silicon; Silicon Dioxide; Sulfuric Acids; Water Pollutants, Chemical; Water Purification

Temperature is known to affect flocculation and filter performance. Jar tests have been conducted in the laboratory, using a photometric dispersion analyser (PDA) to assess the effects of temperature on floc formation, breakage and reformation. Alum, ferric sulphate and three polyaluminium chloride (PACI) coagulants have been investigated for temperatures ranging between 6 and 29 degrees C for a suspension of kaolin clay in London tap water. Results confirm that floc formation is slower at lower temperatures for all coagulants. A commercial PACl product, PAX XL 19, produces the largest flocs for all temperatures; and alum the smallest. Increasing the shear rate results in floc breakage in all cases and the flocs never reform to their original size. This effect is most notable for temperatures around 15 degrees C. Breakage, in terms of floc size reduction, is greater for higher temperatures, suggesting a weaker floc. Recovery after increased shear is greater at lower temperatures implying that floc break-up is more reversible for lower temperatures.

Topics: Alum Compounds; Aluminum Chloride; Aluminum Compounds; Aluminum Silicates; Chlorides; Clay; Coagulants; Ferric Compounds; Flocculation; Kaolin; Polymers; Temperature; Waste Disposal, Fluid

Arsenic removal from household drinking water has been receiving considerable attention in the field of water supply engineering. To develop the optimal coagulation protocol, the effectiveness of several operation options such as coagulants, coagulant aids and additives, as well as flocs separation systems were investigated in this study through the use of orthogonal array experiment based on Taguchi method. Arsenic removal mechanism during household coagulation (via manual mixing) was also discussed. The results showed that the addition of kaoline and powder activated carbon (PAC) did not enhance arsenic removal efficiency of ferric sulfate or aluminum sulfate. Similarly, mixture of ferric sulfate and aluminum sulfate (MFA) as well as polymeric ferric silicate sulfate (PFSiS) was also unable to improve the overall arsenic removal efficiency. The mechanism of arsenic removal during coagulation was somewhat different from those experienced in conventional processes. Coprecipitation appeared to be the crucial mechanism for arsenic removal. It is noted from this study that arsenic adsorption isotherm under household operation condition could be described by Langmuir equation. An efficient flocs separation system subsequent to coagulation was essential to achieve the effectiveness of overall arsenic removal. The results obtained from field experiment demonstrated that the method of ferric sulfate coagulation/sand filtration for arsenic removal from household drinking water was acceptable and affordable.

Topics: Alum Compounds; Arsenic; Carbon; Chemical Precipitation; Ferric Compounds; Flocculation; Housing; Humans; Kaolin; Water Movements; Water Pollutants; Water Purification

Aluminum is suspected to play a role in several neurological disorders. Reactive oxygen species (ROS) lead to oxidative stress, which is thought to be a possible mechanism for neurological damage. Interactions between aluminum and iron, a known promoter of prooxidant events, were studied in cerebral tissues using a fluorescent probe to measure rates of generation of ROS. Al2(SO4)3 alone failed to stimulate ROS production over a wide range of concentrations (50-1000 microM). The aluminum-deferrioxamine chelate in the absence of iron could also not potentiate ROS formation. However, Al2(SO4)3 potentiated FeSO4-induced ROS, with a maximal effect at 10 microM Fe and 500 microM Al. Kaolin, a hydrated aluminum silicate, did not potentiate iron-induced ROS formation. Ferritin had a minor stimulatory effect on ROS generation, but this was not potentiated by the concurrent presence of Al2(SO4)3. Transferrin had no effect on basal rates of ROS generation, but when Al2(SO4)3 was also present, ROS production was enhanced. It is concluded that: 1. There is a potentiation of iron-induced ROS by aluminum salts; 2. Free or complexed aluminum alone is not a key producer of ROS; and 3. High rates of ROS production are unlikely to be owing to the displacement by aluminum iron from its biologically sequestered locations.

Topics: Alum Compounds; Animals; Drug Synergism; Ferric Compounds; Ferritins; Fluoresceins; Kaolin; Male; Nerve Tissue; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Siderophores; Transferrin