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Fly ash was used as raw material to prepare zeolites through silicate gels, assisted by the hydrothermal method. The silicate gels could be effectively formed in a few minutes in a molten alkali environment. The zeolites could be prepared by using these silicate gels through the hydrothermal method, which realizes the transformation from useless materials to highly valuable materials. The obtained zeolites were applied to the removal of ammonium in water, achieving the highvalue utilization of fly ash. The synthesized zeolites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrum (EDS), thermogravimetric (TG), and Fourier transform infrared (FTIR) spectroscopy. The study on the adsorption and removal of ammonium in water shows that the adsorption of ammonium is more in line with pseudo first-order kinetics, and the adsorption mainly occurs in the first 20 min. The adsorption can reach equilibrium in 30 min, and the maximum adsorption capacity can reach 49.1 mg/g. The adsorption capacity of ammonium has the best performance at pH = 5. Furthermore, within a certain range, an increase in temperature is beneficial for the removal of ammonium. [ABSTRACT FROM AUTHOR]

Fly ash was used as raw material to prepare zeolites through silicate gels, assisted by the hydrothermal method. The silicate gels could be effectively formed in a few minutes in a molten alkali environment. The zeolites could be prepared by using these silicate gels through the hydrothermal method, which realizes the transformation from useless materials to highly valuable materials. The obtained zeolites were applied to the removal of ammonium in water, achieving the highvalue utilization of fly ash. The synthesized zeolites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrum (EDS), thermogravimetric (TG), and Fourier transform infrared (FTIR) spectroscopy. The study on the adsorption and removal of ammonium in water shows that the adsorption of ammonium is more in line with pseudo first-order kinetics, and the adsorption mainly occurs in the first 20 min. The adsorption can reach equilibrium in 30 min, and the maximum adsorption capacity can reach 49.1 mg/g. The adsorption capacity of ammonium has the best performance at pH = 5. Furthermore, within a certain range, an increase in temperature is beneficial for the removal of ammonium.

The physicochemical and mass-transfer properties were studied for two gels that can be applied in the fabrication of bioreactors using additive manufacturing. The fundamental difference between these gels lies in the mechanisms of their formation from solutions. The first one is a silicic acid gel, which is formed in a chemical reaction and has an irreversible gelling process. The second one is an agarose gel, which is formed from a water solution of agarose upon cooling and turns back into liquid when heated. Studies were performed by optical methods that include the spectroscopy of gel samples during their formation and the visualization of the diffusion fronts of transferred substances. Being nonintrusive, these methods have no effect on the state of samples and do not distort the dynamics of processes. Characteristic patterns of changes in the spectral parameters during gelling were studied for both gels depending on the dispersed phase concentration, which was relevant to the practical application of the gels. New experimental data were obtained on the structure of the gels and the mechanisms of its change during gel aging. The main laws are determined for changes in the diffusion coefficients in the gels with increasing concentration of the dispersed phase. [ABSTRACT FROM AUTHOR]

As a promising method of carbon emission reduction, carbon capture, utilization and storage (CCUS) is an important technology to achieve carbon neutrality. CO 2 geological storage is an indispensable part of CCUS technology, and it is also the most effective measure for long-term storage of CO 2. However, when the injected high-pressure CO 2 encounters formation water, the pH value of the system will turn down to about 3.0 Wellbore cement degradation would be a problem because the internal structure would become loose under such a strong acid environment for a long period, and can ultimately lead to gas leakage. In addition, the complex temperature and pressure changes caused by the injection of CO 2 in the underground would also lead to micro-annulus between cement-casing and cement-formation rock. Due to the existence of hydrodynamic drive and buoyancy, the escape of CO 2 is inevitable, thus an appropriate sealant is necessary for the remediation of CO 2 leakage pathways. Gel systems are widely used as sealants in the field of oil and gas industry. Polymer gel is a kind of organic gel that can be modified by changing synthesis methods and synthetic ingredient, for instance, CO 2 -responsive gels are prepared by introducing CO 2 -sensitive groups on the macromolecular chain. Inorganic gels such as silicate gels are also an ideal sealants thanks to their advance chemical stability and injectability. This paper mainly reviewed recent advances of three types of gel systems for CO 2 leakage remediation, namely CO 2 responsive gels, silicate gels and polymer gels. Gelation process and characteristic of gel systems were also discussed. Finally, based on current research advances and existing problems, future prospect of gel systems used for CO 2 leakage remediation were proposed. • Gel systems for CO 2 geological storage leakage remediation were reviewed systematically. • Mechanical strength, temperature resistance and injectivity of the gel system were proposed to be enhanced. • The importance of gel application of CO 2 -responsive gel was emphasized. [ABSTRACT FROM AUTHOR]

Ionic conductivities in hydrated sodium silicate gels (water glasses) of SiO2/Na2O 3.41:1 mole ratio have been obtained by impedance spectroscopy at temperatures above and below the thermally determined glass transition temperature. Conductivities at Tg are in the range 10−6 to 10−7 S cm−1, which are similar to those found recently in several kinds of polymer electrolyte. It is suggested that the absence of a mixed alkali effect and a strong dependence on water imply that conductivities are largely protonic in nature and involve strong interactions between protons, water molecules and the silicate framework. [Copyright &y& Elsevier]

New analogs of åkermanite: Sr 2 CuSi 2 O 7 and Sr 2 CdSi 2 O 7 as well as many previously synthesized analogs were obtained by a simple technique consisting of heating in air of precipitated gels of the right composition. X-ray data revealed an anomaly of the Cu 2+ and (to a lesser extent) Fe 2+ åkermanites which is explained by a simple geometric argument in terms of a small (~3°) angular distortion of the oxygen tetrahedron surrounding the smaller divalent cation. This interpretation is consistent with previous theoretical discussions and Mössbauer data on the iron analog prepared for this study. Single crystals of cobalt åkermanites can be grown from a sodium tungstate flux.