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Mesoporous silica was successfully synthesized for the first time using geothermal water from the Onuma Geothermal Power Plant, Akita Prefecture, Japan. Cetyltrimethylammonium bromide (CTAB) was used as an organic template for the synthesis. CTAB with a concentration of 2.4 × 10 -4  mol/L was reacted for 30 min with geothermal water at a temperature of 90 °C, which had a total silicic acid concentration of 475 mg/L (SiO 2 ), at pH 7.0, pH 8.2 (raw water) and pH 9.0. By calcination of the resulting precipitate at 550 °C, mesoporous silica with a pore size of about 2.8 nm and a specific surface area of > 800 m 2 /g was formed. The total silicic acid concentration in the solution after formation of the mesoporous precipitates was reduced to < 280 mg/L, indicating efficient recovery of supersaturated silicic acid from geothermal water. The monosilicic acid in geothermal water plays an important role in the formation of mesoporous silica. Production of mesoporous silica by our method will contribute not only to prevention of silica scale formation in the piping systems of geothermal power plants but also to its use as an industrial resource., (© 2021. The Author(s).)

Surface functionalized mesoporous silicates, MCM-41s, having 3-(2-pyridylmethylideneimino)propyl group (PI-MCM-41) or 3-(2-quinolylmethylideneimino)propyl group (QI-MCM-41) were prepared via Schiff base reaction, and the adsorption behavior of metal ions onto the modified MCM-41s was investigated. The function groups on the modified MCM-41 surface were confirmed by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and elemental analysis. The metal ions examined, Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , Cd 2+ , and Pb 2+ , were quantitatively adsorbed on the PI-MCM-41 and QI-MCM-41, except for Mn 2+ . In the complexation with these metal ions, it was suggested that imine-N and heterocyclic-N atoms act as donor atoms. In addition, it was considered that the hydrophobicity derived from the organo-functional groups modified on MCM-41 contributed to improving the adsorption ability.

Rosette-like layered double hydroxide ( rose LDH) crystals with interlayer CO 3 2- anions were synthesized by the reaction of Mg(NO 3 ) 2 , Al(NO 3 ) 3 , and hexamethylenetetramine (HMT) at 140 °C over 4 days. Crystals as large as 20 μm were produced when using a specific range of HMT concentrations. The substitution of CO 3 2- interlayer ions with ClO 4 - or Cl - anions was achieved by the addition of perchloric acid or hydrochloric acid, respectively, to dispersion of material in methanol. The products were denoted as CO 3 2- rose LDH, ClO 4 - rose LDH, and Cl - rose LDH, respectively. These LDHs were characterized using X-ray diffraction under controlled relative humidity, as well as by Fourier transform infrared spectroscopy and scanning electron microscopy. Adsorption experiment with anions such as phosphate (HPO 4 2- ) and nitrate (NO 3 - ) was conducted by using ClO 4 - rose LDH and Cl - rose LDH. The results indicate that both anions were adsorbed through an ion-exchange mechanism. The maximum HPO 4 2- adsorption capacity at equilibrium on ClO 4 - rose LDH was 1.6 mmol g -1 (49.6 mg P g -1 ), which corresponds to approximately 75% of the total positive layer charge. Cl - rose LDH showed a similar adsorption capability. Commercially available platelike LDH particles were essentially impermeable to water flow due to clogging, while the rose LDH crystals showed excellent permeability, an order of magnitude higher than that exhibited by the platelike LDH synthesized using a homogeneous precipitation method with different growth conditions. Anion adsorption during batch and flow-through test with the ClO 4 - rose LDH (mean particle diameter ∼ 38 μm) in a packed bed showed good uptake of HPO 4 2- and NO 3 - from aqueous solutions. These results demonstrate the potential of rose LDH materials to serve as a column filler adsorbent of the hazardous anions.

Potassium (K(+)) phlogopite was transformed to a vermiculite-like mineral through a topotactic reaction under acidic conditions (pH 2) followed by hydrothermal treatment with Na(+), Mg(2+), Ca(2+), and Al(3+) cations. The resulting Na(+)-, Mg(2+)-, Ca(2+)-, and Al(3+)-altered phlogopites (Phl) denoted as Na-Phl, Mg-Phl, Ca-Phl, and Al-Phl, respectively. Na-Phl, Mg-Phl, and Ca-Phl all exhibited the same high adsorption capacity as natural vermiculite and the absorption of Cs(+) and Sr(2+) ions on these materials followed the Langmuir model. High-angle annular dark-field scanning transmission electron microscopy showed that Cs(+) ions in the Mg-Phl layers were intercalated deep within the crystal structure, along specific interlayer regions. These adsorbed anhydrous Cs(+) ions were firmly fixed at the centers of hexagonal rings positioned simultaneously in the upper and lower tetrahedral silicate sheets, whereas Sr(2+) ions adsorb into the interlayer in the hydrous state. Al-Phl formed a hydroxyl-interlayered vermiculite and demonstrated significant selectivity for Cs(+) at very low concentrations of the isotope. Consequently, the artificially altered phlogopites prepared in this study showed controllable and versatile adsorption capabilities making them significantly more suitable than natural vermiculite for Cs and Sr decontamination.

Geomaterials are materials inspired by geological systems originating from the billion years long history of the Earth. This article reviews three important classes of geomaterials. The first one is smectites-layered silicates with a cation-exchange capacity. Smectites are useful for removing pollutants and as intercalation compounds, catalysts and polymer nanocomposites. The second class is layered double hydroxides (LDHs). They have an anion-exchange capacity and are used as catalysts, catalyst precursors, sorbents and scavengers for halogens. The third class of geomaterials is zeolites-microporous materials with a cation-exchange capacity which are used for removing harmful cations. Zeolite composites with LDHs can absorb ammonium and phosphate ions in rivers and lakes, whereas zeolite/apatite composites can immobilize the radioactive iodine. These geomaterials are essential for environmental remediation.

The amount of radioactive iodine generated from nuclear power plants is expected to increase with the proliferation of nuclear energy production, and long-term immobilization methods for such radioactive elements need to be developed to make nuclear energy sustainable. The standard immobilization method of radioactive elements, vitrification, is not very effective for radioactive iodine-129 because of the low solubility of iodine in silicate melts, its very high volatility at standard vitrification process temperatures, and its instability in the alkaline environment of deep geological layers below 300 m. We have developed a novel three-phase ceramic composite produced by a sintering process. Iodine adsorbed onto Ca-type zeolite A was covered with a hydroxyapatite nanolayer through the exchange reaction of ammonium with calcium. Clusters of iodine of 30 nm within the zeolite structure were found to be thermally stable up to 1253 K because of the partial blockage of the alpha-cage apertures by ammonium ions and the partial change from a crystalline phase to an amorphous phase at 473 K. No gasification of iodine molecules was found to occur during the sintering process. The outer phase was highly crystalline hydroxyfluorapatite in which the hydroxyapatite nanolayer plays an important role for successful sintering. The elution of iodine in low-dioxygen water, similar to that found within the Earth's crust, was investigated and was found to occur only in the surface layer of the sintered body.

Background: Integrins are major adhesion receptors that not only regulate cytoskeletal organization, but also trigger a variety of intracellular signal transduction pathways. We examined the effects of increased extracellular matrix (ECM) accumulation on monocyte chemoattractant protein-1 (MCP-1) expression, which is known to play an important role in the progression of various glomerular diseases., Methods: MCP-1 mRNA and protein expression in cultured rat mesangial cells (MC) attached to ECM proteins were examined by reverse transcription (RT)-polymerase chain reaction (PCR) and Western blotting, respectively. Phosphorylation of focal adhesion kinase (FAK) was measured by Western blotting. Effects of wild-type and dominant-negative FAK on MCP-1 expression were examined by a transient transfection assay., Results: Cell adhesion to fibronectin-induced phosphorylation of FAK and MCP-1 mRNA expression in time- and dose-dependent manners followed by increased MCP-1 protein expression. All integrin-interacting substrates (laminin and types I, III, and IV collagens) also increased levels of FAK phosphorylation and MCP-1 expression, whereas nonspecific adhesive substrates (polylysine and concanavalin A) had no significant effects. Overexpression of wild-type FAK increased phosphorylation of FAK and expression of MCP-1 mRNA and protein, whereas transfection of dominant-negative FAK abolished adhesion-induced MCP-1 expression. Adhesion-induced expression of MCP-1 mRNA was inhibited by genistein and tosyl phenylalanyl chloromethylketone (TPCK), suggesting that tyrosine kinases [e.g., FAK, and nuclear factor kappa B (NF-kappa B)] are necessary in this signaling., Conclusion: Our results indicate that integrin-mediated cell adhesion to the ECM can induce MCP-1 expression through activation of FAK, and suggest a role for altered ECM deposition in the progression of glomerular diseases by affecting gene expression.