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.

Synthesis and characterization of a molecularly imprinted silica gel sorbent for the on-line determination of trace sudan I in chilli powder through high-performance liquid chromatography

Abstract: A highly selective imprinted polymer was synthesized by a surface molecular imprinting technique in combination with a sol−gel process. The imprinted polymer was evaluated by FT-IR and static and kinetic adsorption experiments. The results showed that the imprinted sorbent exhibited good recognition and selective ability, offered a faster kinetics for the adsorption and desorption of Sudan I than the non-imprinted sorbent, a saturated binding capacity (Qmax) that reached 33.47 mg g-1. The prepared sorbent was applied for the determination of trace Sudan I through on-line solid-phase coupled with high-performance liquid chromatography (SPE-HPLC). With a loading flow rate of 1.5 mL min-1 for sampling 50 mL, an enrichment factor of 1266 was achieved. The detection limit (S/N = 3) was 1.2 ng L-1, and the peak area precision (RSD) for five replicate detections of 0.01 μg L-1 Sudan I was 3.66%. The Sudan I in the chilli powder from the local market was determined at three levels (0.25, 0.5, and 1.0 ng g-1) with...

Hybrid Silica Gels Containing 1,3-Butadiyne Bridging Units. Thermal and Chemical Reactivity of the Organic Fragment

Abstract: Silica gel containing diyne units have been obtained from molecular organosilicon precursors and the properties associated to the very reactive unsaturated organic moieties have been explored. The sol−gel polymerization of 1,4-bis(trimethoxysilyl)-1,3-butadiyne ((MeO)3SiC⋮CC⋮CSi(OMe)3) quantitatively led to a silsesquioxane network, [O1.5SiC⋮CC⋮CSiO1.5]n, consisting of siloxanes chains with bridging diyne units. The derived xerogels were characterized by IR and 13C and 29Si CP MAS NMR spectroscopies. The major environment of the Si atom corresponded to a T2 CSi(OR)(OSi)2 substructure, and only minor Si−C bond cleavage occurred during the sol−gel condensation. The chemical reactivity of the hybrid organic−inorganic gel was studied and used as a tool for the study of the organization of the solid induced by the organic moieties. Upon heating, in the solid state, the diyne fragments undergo a polyaddition to give an ene−yne structure. The polymerization, observed in the solid state, suggests favorable arrang...

Gas-chromatographic determination of phenols in aqueous samples after solid phase extraction

Abstract: 27 phenols including mono-, di-, tri-, tetra- and pentachlorophenols, mono- and dinitrophenols, mono-and dinitrocresols and dimethylnitrophenols have been extracted from aqueous samples by solid phase extraction using both modified silica gel (C18) and XAD resin-adsorbents and determined by gas chromatography (GC) using capillary columns with specially desactivated weakly polar phases. If a 11 sample of spiked water is used, a considerable breakthrough is observed with phenol itself, while all other phenols are almost quantitatively extracted. The recovery of phenol itself can be improved by employing smaller sample volumes.

Reaction of Hydraulic Calcium Silicates with Carbon Dioxide and Water

Abstract: The carbonation of wetted powders of beta-dicalcium silicate (β·2CaO·SiO2=β-C2S) and tricalcium silicate (3CaO·SiO2= C3S) was studied as a function of reaction conditions. The water/solids ratio is an important parameter and there is an optimum value for each silicate. Relative humidity and the partial pressure of CO2 also strongly affect the reaction. The rate of carbonation can be conveniently represented by plotting the degree of carbonation against the logarithm of time. C-S-H and calcite are the initial reaction products. Subsequently, carbonation of the C-S-H produces silica gel, whereas aragonite may form if the system is allowed to dry out.