Papers by Keyword: Precipitated Silica

Abstract: The silica extraction from palm oil mill fly ash (POMFA) using sodium hydroxide as one of viable processes for obtaining silica from agricultural waste was investigated. The effects of extraction time and temperature were closely examined to study the kinetics of the process. The fixed variables used in the present work were mass of POMFA 468.2 gram; the POMFA mass to NaOH volume ratio 0.2341 g/cm³; the concentration of NaOH 1.4 N and the stirring speed of 1065 RPM. The levels of temperature employed were 348 K, 358 K, 368 K and 378 K for different time durations up to 60 min. The mechanical fragmentation process was applied to obtain precipitated silica from the extracted silica. The precipitation conditions were: stirring speed of 1160 RPM, pH of 8.75, temperature of 303 K and precipitation time of 100 min. The shrinking core model (SCM) with intra-particle diffusion controlled mechanism and the Jander equation can satisfactorily represent the extraction process. The activation energy for silica extraction was 58.20 kJ/mol for the SCM with intra-particle diffusion and 62.22 kJ/mol for the Jander equation respectively. The precipitated silica agglomerate obtained at the time of 100 min has the median-weighed volume particle size distribution of 114.07 μm. The chemical composition and physical characteristic of precipitated silica which were analyzed with LPSA, XRF, XRD, FTIR and SEM are similar to the precipitated silica from the references.

Abstract: Using precipitated silica as the carrier, a kind of composite photocatalyst was prepared through hydrolysisde positing method. The obtained composite material was characterized by XRD, SEM, TEM, FT-IR. Based on the experimental results and analysis of characterization, the preparation mechanism of composite powder material was studied. The photocatalytic degration experiment of Rhodamine-B indicates that the precipitated silica is an ideal carrier of the TiO₂,and the photocatalyst can combine with the silica tightly. The photocatalytic activity of the obtained composite material is stabilize and constant.

Abstract: In is paper precipitated silica is used in coated paper coating. It shows that the effect of different silica on properties of pigment dispersion is different. The dosage of silica influences the properties of pigment dispersion too. The viscosity of coating is higher than the corresponding pigment dispersion. The higher the viscosity of pigment dispersion is, the higher the corresponding viscosity of coating is. The more the dosage of silica is and the littler the particle size of silica is, the larger water retention value of coating is. When the precipitated silica is used in coated paper coating, the viscosity of coating is increasing. If precipitated silica coat paper, the whiteness of coated paper increases by 1%-2%

Abstract: When precipitated silica was prepared from yellow phosphorus slag by the phosphoric acid leaching, the Fe content can not meet the quality requirements of the product. This article indicates the method of purifying precipitated silica with nitric acid solution, which may decrease the Fe content to about 0.02%. The purification optimum technical conditions are: the nitric acid concentration 8%, reaction time 2.0 hours, reaction temperature 343.15K, fluid solid ratio 4:1, stirring speed 300 rpm.

Abstract: Precipitated silica was prepared by the hydrolysis of silicon tetrachloride in a dilute solution of soluble glass. In order to identify the optimal synthesis conditions of preparing silica powder with the good dispersivity and uniformity, technical parameters such as volumes of polyethylene glycol(PEG) and anhydrous ethanol, reaction temperature, final solution pH and the concentration of soluble glass were investigated. Products were characterized by scan electron microscopy(SEM),transmission electron microscopy(TEM), infrared spectroscopy(IR), x-ray diffraction(XRD) and laser nano-particle size analyzer. Under the optimal formation condition, amorphous silica particles with average diameters of 284nm and irregular-shaped morphology were obtained.

Abstract: This paper deals with the control of the adhesion strength in metal-elastomer joints by fillers and the use of rubber blends to produce advanced high performance adhesive systems. The curing behavior of rubber compounds and dynamic mechanical properties of crosslinked rubber composites were considered in this technologically applicable study. The effects of two types of reinforcing filler, used to increase the adhesion strength between steel and rubber matrix based on acrylonitrile-butadiene rubber (NBR) and chlorosulfonated polyethylene rubber (CSM) was investigated. Precipitated silica (with the average size of primary particle 15 nm) and diatomaceous earth (with the average size of primary particle 28 µm) were used for both rubber and its blend (NBR/CSM). The filler loading range was from 0 to 35 phr. The determination of curing characteristics was estimated by Monsanto Rheometer. The crosslink density of the rubber composites was determined by swelling measurement. Dynamic mechanical behavior was measured by mechanical spectroscopy (in a single cantilever bending mode).