Silica gel

About: Silica gel is a research topic. Over the lifetime, 22313 publications have been published within this topic receiving 325516 citations. The topic is also known as: Amorphous silica & Precipitated amorphous silica.

Interaction between Surfaces of Fused Silica in Water. Evidence of Cold Fusion and Effects of Cold Plasma Treatment

Abstract: Silica colloids and silica glass surfaces have often been used as “model” systems to study coagulation, rheology, contact angles, and surface forces. But the silica−water interface is highly changeable and reactive. It has stubbornly refused to conform to theoretical models of an ideal hydrophilic substrate. In this study we show why this is and demonstrate some of the diverse properties of this surface. Surfaces of fused quartz swell under water to form layers of silica gel. We report here on how this well-known effect shows up in surface force measurements. Peculiar effects occur already at normal pH. Over a period of time after the surfaces are immersed in water, identical interaction patterns occur on approach and on separation. The double-layer repulsion extends from large distances down to the contact. Interaction hysteresis develops later. Adhesion and other specific interactions, particularly at short range, develop with time. The evolution that extends for hours and days is variable in its manife...

Silica gel in organic synthesis

Abstract: The data on the use of silica gel in organic synthesis are presented. Some specific features of cyclisation (both intra- and intermolecular) reactions, rearrangements, reduction, oxidation, condensation, formylation, hydration and dehydration, protection of functional groups, etc., in the presence of silica gel, are discussed. The bibliography includes 96 references.

Comparison of sorbents and isotherm models for NH3-gas separation by adsorption

Abstract: Adsorption equilibrium isotherms of ammonia gas were measured at temperatures between 298 and 393 K on 13X zeolite, 4A zeolite, alumina, silica gel, and activated carbon. The applicability of these sorbents to ammonia gas separation was compared based on equilibrium data. In the pressure range of 1 to 100 kPa activated carbon has its highest working capacity (5.5 mmol·g−1) at 298 K, and the working capacity drops rapidly with temperature, reaching its lowest point at 393 K. The two zeolites provide almost the same working capacity, 3.0–3.5 mmol·g−1, over the entire temperature range. Silica gel and alumina showed low working capacities. The experimental equilibrium data were fitted to 16 different isotherm models, with accuracy and reliability statistically evaluated. The Langmuir–Freundlich model with the van't Hoff equation for the equilibrium constant and with a thermal expansion equation for the saturation sorbate concentration provided the most accurate fit for the 13X and 4A zeolites. This model was also very accurate for the alumina and silica gel data, even though the Dubinin–Astakhov model gave slightly higher predictions. The Henry and vacancy solution models provided the best fit for activated carbon.