A process disclosed herein is related to the isolation and purification of substantially pure chemicals, including silica gel, sodium silicate, aluminum silicate, iron oxide, and rare earth elements (or rare earth metals, REEs), from massive industrial waste coal ash. In one embodiment, the process includes a plurality of caustic extractions of coal ash at an elevated temperature, followed by an acidic treatment to dissolve aluminum silicate and REEs. The dissolved aluminum silicate is precipitated out by pH adjustment as a solid product while REEs remain in the solution. REEs are captured and enriched using an ion exchange column. Alternatively, the solution containing aluminum silicate and REEs is heated to produce silica gel, which is easily separated from the enriched REEs solution. REEs are then isolated and purified from the enriched solution to afford substantially pure individual REE by a ligand-assisted chromatography. Additionally, a simplified process using one caustic extraction and one acidic extraction with an ion exchange process was also investigated and optimized to afford a comparable efficiency.

A reusable best-by date indicator incudes a main body, which is made of a transparent material, having a plurality of storages, the main body having a first air vent at one end through which outside air can be drawn in and a second air vents between the storages; a plurality of silica gels, each of which is stored in the storages, respectively, the gels changing their color depending on the degree of moisture absorption; a slidable cover that is placed near the first air vent of the body and can exposes the first air vent by slide; and a double-sided tape attached bonded to the back surface of the body.

A reusable best-by date indicator incudes a main body, which is made of a transparent material, having a plurality of storages, the main body having a first air vent at one end through which outside air can be drawn in and a second air vents between the storages; a plurality of silica gels, each of which is stored in the storages, respectively, the gels changing their color depending on the degree of moisture absorption; a slidable cover that is placed near the first air vent of the body and can exposes the first air vent by slide; and a double-sided tape attached bonded to the back surface of the body.

An inorganic porous carrier having pore distribution where a pore diameter is 0.04 μm or more, and including a linker of formula (1) [where a bond * represents a bond to an oxygen atom of a silanol group in an inorganic porous substance. R.sup.1 and R.sup.2 represent each independently an alkyl group containing 3 to 10 carbon atoms, or a phenyl group. L represents a single bond; an alkylene group containing 1 to 20 carbon atoms; or an alkylene group containing 2 to 20 carbon atoms containing —CH.sub.2-Q-CH.sub.2— group wherein any group Q selected from a group consisting of —O—, —NH—, —NH—CO—, and —NH—CO—NH— is inserted into at least one of —CH.sub.2—CH.sub.2— group constituting the alkylene group. A carbon atom of the methylene group bound to the group Q does not bond to another group Q at the same time.]; and a method for preparing nucleic acids using the same.

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An inorganic porous carrier having pore distribution where a pore diameter is 0.04 μm or more, and including a linker of formula (1) [where a bond * represents a bond to an oxygen atom of a silanol group in an inorganic porous substance. R.sup.1 and R.sup.2 represent each independently an alkyl group containing 3 to 10 carbon atoms, or a phenyl group. L represents a single bond; an alkylene group containing 1 to 20 carbon atoms; or an alkylene group containing 2 to 20 carbon atoms containing —CH.sub.2-Q-CH.sub.2— group wherein any group Q selected from a group consisting of —O—, —NH—, —NH—CO—, and —NH—CO—NH— is inserted into at least one of —CH.sub.2—CH.sub.2— group constituting the alkylene group. A carbon atom of the methylene group bound to the group Q does not bond to another group Q at the same time.]; and a method for preparing nucleic acids using the same.

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The present invention refers to a stable sodium and iron silicate solution that has a weight ratio of SiO.sub.2 to Na.sub.2O from 1.5 to 2.5 and a total percentage of solids, expressed by the sum of SiO.sub.2 and Na.sub.2O, from 20% to 55%. Said solution also has a soluble iron content, expressed by Fe, from 0.1% to 7%, and a water content from 38% to 79.9%. The present invention also refers to the process for preparing said stable solution of sodium and iron silicate, which comprises the steps of: (a) providing a siliceous material containing iron; (b) submitting said siliceous material containing iron to a hydrothermal treatment with caustic soda under high temperature and controlled pressure; and (c) filtering said reacted solution to separate the reacted portion of the hydrothermal treatment from the unreacted portion. Additionally, the present invention refers to the uses of said stable sodium and iron silicate solution.

The present invention refers to a stable sodium and iron silicate solution that has a weight ratio of SiO.sub.2 to Na.sub.2O from 1.5 to 2.5 and a total percentage of solids, expressed by the sum of SiO.sub.2 and Na.sub.2O, from 20% to 55%. Said solution also has a soluble iron content, expressed by Fe, from 0.1% to 7%, and a water content from 38% to 79.9%. The present invention also refers to the process for preparing said stable solution of sodium and iron silicate, which comprises the steps of: (a) providing a siliceous material containing iron; (b) submitting said siliceous material containing iron to a hydrothermal treatment with caustic soda under high temperature and controlled pressure; and (c) filtering said reacted solution to separate the reacted portion of the hydrothermal treatment from the unreacted portion. Additionally, the present invention refers to the uses of said stable sodium and iron silicate solution.

Provided is a loss circulation material that may consist essentially of an acidic nanosilica dispersion and an activator. The acidic nanosilica dispersion may consist of acidic silica nanoparticles, stabilizer, and water, and may have a pH in a range of 3 to 6. The activator may be one or more from the group consisting of sodium bicarbonate, sodium chloride, or an amine salt. A method is provided for controlling lost circulation in a lost circulation zone in a wellbore comprising introducing the loss circulation material and forming a gelled solid from the loss circulation material in the lost circulation zone.

Provided is a loss circulation material that may consist essentially of an acidic nanosilica dispersion and an activator. The acidic nanosilica dispersion may consist of acidic silica nanoparticles, stabilizer, and water, and may have a pH in a range of 3 to 6. The activator may be one or more from the group consisting of sodium bicarbonate, sodium chloride, or an amine salt. A method is provided for controlling lost circulation in a lost circulation zone in a wellbore comprising introducing the loss circulation material and forming a gelled solid from the loss circulation material in the lost circulation zone.

The present invention provides a means capable of suppressing the formation of fine particles in a method for producing a silica sol. The present invention relates to a method for producing a silica sol, including synthesizing a silica sol by, in a reaction liquid containing an alkoxysilane or a condensate thereof, water, and an alkali catalyst, allowing the alkoxysilane or condensate thereof to react with the water in the presence of the alkali catalyst, wherein the alkali catalyst is not additionally supplied after the start of the synthesis until the finish time of the synthesis, and during 90% or more of the time between when 5 minutes have elapsed from the time point when the electrical conductivity of the reaction liquid reaches a local maximum for the first time and the finish time of the synthesis, the proportion of the value of the electrical conductivity of the reaction liquid is more than 90% relative to the value of the electrical conductivity at the time when 5 minutes have elapsed from the time point when the local maximum is reached.