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Radical-type mechanophores (RMs) can undergo homolytic cleavage of their central C-C bonds upon exposure to mechanical forces, which affords radical species. Understanding the characteristics of these radical species allows designing and developing bespoke mechanoresponsive materials. The thermal stability of the central C-C bonds and the oxygen tolerance of the generated radical species are crucial characteristics that determine the functions and applicability of such RM-containing mechanoresponsive materials. In this paper, we report the synthesis and characterization of two series of arylfluorene-based RM derivatives, i.e., 9,9'-bis(5-methyl-2-pyridyl)-9,9'-bifluorene (BPyF) and 9,9'-bis(4,6-diphenyl-2-triazyl)-9,9'-bifluorene (BTAF). The synthesis of BPyF and BTAF derivatives was accomplished without generating any peroxides initially, albeit that BPyF slowly converted to the corresponding peroxide in solution. DFT calculations revealed the importance of the thermodynamic stability and the values of the a-SOMO levels of the corresponding radical species for their thermal stability and oxygen tolerance. Furthermore, the mechanochromism of BTAF was demonstrated by ball-milling a BTAF-centered polymer, which was synthesized via atom-transfer radical polymerization (ATRP).

The exploration of mechanochemical reactions has brought new opportunities for the design of functional materials. We synthesized the novel organic peroxide mechanophore bis(9-methylphenyl-9-fluorenyl) peroxide (BMPF) and examined its mechanochromic properties. The mechanism behind its mechanofluorescence was clarified and harnessed in polymer networks that can release the small fluorescent molecule 9-fluorenone upon exposure to a mechanical stimulus. Additionally, polymer networks cross-linked with BMPF units are able to tolerate temperatures up to 110 °C without any change in optical properties or mechanical strength. As mechanophores based on organic peroxide have rarely been documented so far, these fascinating results suggest excellent potential for applications of BMPF in stress-responsive materials. The mechanochemical protocol demonstrated here may provide guiding principles to expand the field of mechanochromic peroxides.

Mechanochromic elastomers that exhibit force-induced cross-linking reactions in the bulk state are introduced. The synthesis of segmented polyurethanes (SPUs) that contain difluorenylsuccinonitrile (DFSN) moieties in the main chain and methacryloyl groups in the side chains was carried out. DFSN was selected as the mechanophore because it dissociates under mechanical stimuli to form pink cyanofluorene (CF) radicals, which can also initiate the radical polymerization of methacrylate monomers. The obtained elastomers generated CF radicals and changed color by compression or extension; they also became insoluble due to the mechanically induced cross-linking reactions. Additionally, an SPU containing diphenylmethane units also exhibited highly sensitive mechanofluorescence. To the best of our knowledge, this is the first report to demonstrate damage detection ability and changes in the mechanical properties of bulk elastomers induced by simple compression or extension.

The effects of the combined addition of Mg- and Ca-based adsorbents (MgO, Mg(OH)2, MgCO3, CaO, Ca(OH)2, and CaCO3) were systematically tested for improving arsenic-removal performance and inhibiting the leaching of base material components from the adsorbent. Arsenic-removal tests were conducted with each single type or combination of two types of adsorbents. Results obtained after the combined-addition tests were compared with those obtained from the single-addition test with each adsorbent. The arsenic-removal performance improved in most combined additions but decreased in certain combined additions of MgO or Mg(OH)2 with Ca-based adsorbents. The arsenic-removal performance of the combined addition of MgCO3 and Ca(OH)2 was the highest. The combination of Mg-based adsorbents with CaO or Ca(OH)2 inhibited Mg-leaching, whereas that of CaO or Ca(OH)2 with MgCO3 inhibited Ca-leaching. Improvement in arsenic-removal performance for the combination of MgCO3 with CaO or Ca(OH)2 was caused by the incorporation and co-precipitation with arsenic when Mg(OH)2 and CaCO3 were produced. MgCO3-Ca(OH)2 and MgCO3-CaO are recommended for both arsenic removal and environmental adsorbent stability that can be effectively applied over a wide range of arsenic concentrations.

The spent adsorbents left after treating arsenic-contaminated water contain large amounts of arsenic. These spent adsorbents may come into contact with silicic acid leached from soil or cementitious solidification materials in the disposal environment. Thus, it is important to evaluate the effects of silicic acid on spent adsorbents containing arsenic. In this study, the effects of silicic acid on spent Mg-based adsorbents (magnesium oxide (MgO) and magnesium hydroxide (Mg(OH)2)) containing arsenite were investigated. The arsenic leaching ratios of both spent adsorbents decreased slightly with an increase in the initial silicic acid concentration of the eluent. The arsenic leaching ratio decreased from 1.24% to 0.69% for MgO and from 5.97% to 4.71% for Mg(OH)2 at an initial Si-normalized concentration of 100 mg/L. The primary mechanism behind the inhibition of arsenic leaching by silicic acid was determined to be the difficulty of arsenic desorption due to the coating effect following the adsorption of silicic acid species. The results indicate that the arsenic leaching related to the ion exchange reaction with silicic acid hardly occurred for the spent Mg-based adsorbents. Compared with various spent Mg-based and Ca-based adsorbents, the spent MgO adsorbent exhibited the highest environmental stability and best performance.

Suzuki-Miyaura coupling reaction of BrC6 H4 -X-C6 H4 Br 1 (X=CH2 , CO, N-Bu, O, S, SO, and SO2 ) with arylboronic acid 2 was investigated in the presence of tBu3 PPd precatalyst and CsF/[18]crown-6 as a base to establish whether or not the Pd catalyst can undergo catalyst transfer on these functional groups. In the reaction of 1 (X=CH2 , CO, N-Bu, O, and SO2 ) with 2, aryl-disubstituted product 3 (Ar-C6 H4 -X-C6 H4 -Ar) was exclusively obtained, indicating that the Pd catalyst undergoes catalyst transfer on these functional groups. On the other hand, the reaction of 1 e (X=S) and 1 f (X=SO) with 2 afforded only aryl-monosubstituted product 4 (Ar-C6 H4 -X-C6 H4 -Br) and a mixture of 3 and 4, respectively, indicating that S and SO interfere with intramolecular catalyst transfer. Furthermore, we found that Suzuki-Miyaura polycondensation of 1 (X=CH2 , CO, N-Bu, O, and SO2 ) and phenylenediboronic acid 5 in the presence of tBu3 PPd precatalyst afforded high-molecular-weight polymer even when excess 1 was used. The polymers obtained from 1 (X=CH2 , N-Bu, and O) and 5 turned out to be cyclic.

Suzuki–Miyaura polycondensation of an excess of linearly extended, conjugated dibromo monomer with meta-phenylenediboronate and of an excess of the extensively conjugated, kinked dibromo monomer with para-phenylenediboronate in the presence of tBu3PPd(0) precatalyst, which has a strong propensity for intramolecular π-face transfer, afforded cyclic polymers with Mn 12 400–6400, although unstoichiometric polycondensation generally affords linear polymers.

A non-symmetric radical-type mechanophore (CF/ABF) was synthesized by molecular crossing between two radical-type mechanophores. The thermal stability and mechanoresponsiveness of CF/ABF were found to be tunable by altering the properties of the parent RMs. The CF/ABF-centred polymers showed mixed mechanochromism derived from the simultaneous generation of two radical species.

The stability and dispersion of naturally occurring As have been receiving increasing attention, because As is toxic and its contamination is a widespread problem in many countries. This study investigated As fractionation and speciation in organic sediments collected from different depositional settings to elucidate the existence of stable As in humic substances. Eleven organic sediment samples were collected from marine and terrestrial alluvial regions in Hokkaido prefecture, Japan, and the chemical fraction of As and species of humic substances were identified by sequential extraction. In addition, stable As bound in organic matter was evaluated by FT-IR spectroscopy. The As fraction mainly comprised inorganic substances, especially sulfur, iron, and manganese, and terrestrial sediments (lacustrine and inland deposits) were rich in sulfides and Fe and Al (hydr)oxides. When the residual fraction was excluded, the organic fraction of As was higher in seawater sediments than in terrestrial sediments. Among humic substances, cellulose, humic acid, and hydrophilic fulvic acid were clearly associated with As accumulation, and As speciation showed that the As was of organic origin. Cellulose, an organic compound of plant origin, was abundant in As=S and As (III)=O bonds, and As accumulation was higher in sulfur-rich peat sediments, corresponding with the physiological activities of As in plants. Hydrophilic fulvic acid and humic acid in these sediments, originating from small animals and microorganisms in addition to plants, denote higher As contents and abound in As (III, V)=C and C-H, CH3 bonds even in sulfur-rich sediments. The methylated As bonds reflect the ecological transition of organisms.

The spent adsorbents that remain after being used to purify As-contaminated water constitute waste containing a large amount of As. These spent adsorbents, after being disposed, are likely to come into contact with silicic acid leached from the soil or cementitious solidification materials. Thus, it is crucial the evaluate the effects of silicic acid on spent adsorbents. In this study, the effects of silicic acid on spent Ca-based (CaO and Ca(OH)2) adsorbents with arsenite were investigated. The As leaching ratio for the spent adsorbents decreased with an increase in the initial concentration of silicic acid in the liquid. Under the tested conditions, the As leaching ratio decreased from 8–9% to less than 0.7% in the presence of silicic acid at an initial Si-normalized concentration of 100 mg/L. The primary mechanism behind the inhibition of As leaching by silicic acid was determined to be re-immobilization via the incorporation of arsenite during the formation of calcium silicates. In the presence of silicic acid, spent Ca-based adsorbents with arsenite had a lower As leaching ratio than those with arsenate. Therefore, spent Ca-based adsorbents with arsenite were found to have a higher environmental stability than those with arsenate.

In this study, we report the synthesis of dithieno [2,3-d:2′,3′-d']anthra [1,2-b:5,6-b']dithiophene (DTADT) unit and donor-acceptor (D-A) conjugated copolymers incorporated with the DTADT unit as the repeating unit. The novel oligoheteroacene unit––DTADT––was synthesized through the [2 + 2+2] annulation, which is the key reaction, and its reaction pathway was theoretically revealed using the density functional theory calculation. The D-A conjugated copolymers, synthesized through the transition metal-catalyzed polycondensation, could be applied as a solution-processable thin-film transistor. The our own n-layered integrated molecular orbital and molecular mechanics calculation in conjunction with the second order perturbation theory, analyzed based on the natural bond orbital analysis, unveiled that the steric repulsion among the side chains of DTADT and thiophene spacer kept away from the planarization of polymers; this affected the hole mobility of organic field-effect transistor.

The Suzuki–Miyaura coupling polymerization of p-dibromophenylene and m-phenylenediboronic acid ester, as well as m-dibromophenylene and p-phenylenediboronic acid ester, and the combination of two meta-phenylene monomers in the presence of the t-Bu3PPd(0) catalyst selectively afforded cyclic polyphenylenes with polyphenylene bearing boronate moieties at both ends when excess dibromophenylene was used.

The adsorption equilibrium tests on fluorine and boron were carried out using several soils (Kuroboku, Yellow brown forest, Kanuma and Peat). Then various analysis and considerations were done on the basis of the experimental results.Adsorbed amount of fluorine per unit mass of soil was ranged as Kuroboku ≒ Yellow brown forest > Kanuma > Peat. Adsorbed amount of boron per unit mass of soil was ranged as Yellow brown forest > Kuroboku ≒ Kanuma > Peat. It was clear that there was less correlation between the BET specific surface area of the soils and the adsorbed amount of fluorine or boron. The clear correlation between the content of individual element (such as Ca, Mg, Al, Fe and Si) in soils and the absorbed amount fluorine or boron could not be recognized. The quantitative correlation between total carbon content in the soils and the absorbed amount of fluorine or boron could not be also recognized.The applications of an ion exchange model and a surface complexation model to data obtained in this work were unsuccessful because of lack of measurement item. However, the application of Langmuir's adsorption equation to our data except some data was successful basically and the application of Frendlich's adsorption equation was successful significantly. It was clarified the adsorption isotherms of fluorine and boron on the soils are represented using Freundlich's adsorption equation and are unaffected by the mass ratio of soil to liquid. The adsorption coefficients and indexes of fluorine and boron were obtained by using Freundlich's adsorption equation. The utilization of the adsorption parameters makes it possible to estimate the adsorbed amounts of fluorine and boron on the soils or the dissolved concentrations of them into liquid phase.

The leaching behavior of cathode ray tube (CRT) funnel glass containing 23 mass percent of Pb in 0.001 N HCl, distilled water, and 0.001 N NaOH at 90 °C was investigated using a static method. The weight loss and leached amount of each component was measured and surface changes observed by SEM. The leaching mechanism is discussed. In acid solution, the leached amount of Pb showed t 1/2 dependence, that is, diffusion-controlled dependence, which is common in lead silicate glasses. In water and basic solutions, the leached amount showed saturation after higher initial dissolution than in acid and the deposition of many particles on the surface was observed. The amount leached was less for Pb than other components. The deposited particles formed a protective layer, which suppressed the dissolution of the glass. This dense layer must be formed as a result of a high initial dissolution rate.

It is demanded more convenient survey methods for soil pollution by oils and techniques for toxicity evaluation of petroleum hydrocarbons. The quantitative bioassay using luminous bacteria has not been established. The accumulation of data obtained under scientific condition setting is required.Firstly, methanol, ethanol and n-propanol which are both moderate hydrophilic and oleophilic, were examined whether they are adequate as the extraction solvent for soil polluted by oils. From the results in bioassay test using luminous bacteria, methanol was selected as the most suitable extraction solvent from them.Secondly, the acute toxicity evaluation and the detection limit of gasoline, heating oil, light oil, benzene, toluene, n-hexane and carbon disulfide were experimentally examined. The severity of toxicity on luminous bacteria by each 100 vol% of them (without solvent) except n-hexane was carbon disulfide > toluene > gasoline > benzene > methanol > heating oil > light oil. Although the toxicities of 100 vol% of heating oil, light oil and n-hexane were weaker than that of methanol, the use of methanol as the solvent improved the detection sensitivity for them and was possible to detect the toxicity of them by luminous bacteria. The appropriate reaction time for toxicity evaluation or screening may be 15 to 45 minutes. The severity of toxicity on luminous bacteria evaluated using methanol solvent was gasoline > n-hexane > heating oil > toluene > carbon disulfide > benzene > light oil. Also, this study showed potential for quantitatively evaluating in the ranges of 0.02 to 1 vol% of gasoline and heating oil, 0.1 to 5 vol% of light oil and carbon disulfide, 0.2 to 5 vol% of benzene, 0.1 to 1.0 of toluene and 0.05 to 0.5 vol% of n-hexane in methanol solvent (extractant).

Mineral scales were formed in wells and surface installations during a 2-year circulation test performed at the Hijiori Hot Dry Rock (HDR) site, Yamagata, Japan. Anhydrite deposited in the deeper parts of the production wells, while silica and calcium carbonate precipitated at the surface, downstream of the wellhead, in amounts that depended on the temperature and chemical composition of the produced fluid. In well HDR-2a, closer to the injector, most of the scale was calcium carbonate; in HDR-3, further away from the injection well, there was slight precipitation of amorphous silica. As fluid circulation progressed and temperature decreased, scaling in the flow line of well HDR-2a changed from amorphous silica to calcium carbonate.

In order to examine soil adsorption behavior of fluorescein, adsorption-equilibrium experiments were carried out. The soil samples used in this study are Kuroboku soil, Yellow brown forest soil, Kanuma soil and Peat. The parameters on the experiments were the initial concentration of sodium fluorescein (0.1, 1, 10 mg/l) and the mass ratio of soil to liquid (0.001, 0.01, 0.1). When the mass ratio were 0.001 and 0.1, the quantity of fluorescein adsorbed on soils was Kuroboku ≒ Yellow brown forest > Peat >> Kanuma. However, the adsorbed amount on Kanuma was remarkably small and there was not so different among the adsorbed amounts on the other soils. The particle size of soils did not affect the absorbed amount. The BET specific surface area was ranged as Kanuma > Yellow brown forest > Kuroboku > Peat. The absorbed amount on Kanuma having the largest BET specific surface area was the least. Therefore the number of the pore effectively utilized for the adsorption of fluorescein seems to be dependent on the type of soil. The clear correlation could not be found between absorbed amount of fluorescein and each chemical composition which constitutes the soils. It is found that the soil adsorption behavior of fluorescein can be prescribed in the Freundlich's adsorption equation. The adsorption behaviors on Kuroboku, Yellow brown forest and Peat are independent of the initial concentration of fluorescein and the mass ratio of soil to liquid. Although the adsorption behavior on Kanuma is dependent on the mass ratio of soil to liquid, the behavior could be represented by one Freundlich's adsorption equation if the mass ratio is constant.

Sodium fluorescein (uranine) has been used frequently in tracer tests that carried out in order to monitor recirculating fluids utilized for heat exchange with artificial geothermal reservoir such as hot dry rock geothermal system. It is known that fluorescein decomposes in high temperature condition. In the case which tracer solution contained fluorescein is diluted to around 0.1 mg/l of fluorescein concentration by mixing with existing natural geothermal brine in the underground, fluorescein may be strongly affected by thermal effect. In spite of being relatively short residence time, the recirculating fluid utilized in hot dry rock geothermal system is used under the condition in which the temperature dramatically changes. Therefore it is important to understand the detailed thermal decomposition characteristic of fluorescein.In this study, the experiments for thermal decomposition of fluorescein were carried out using flow-type reactor, and the effects of the initial concentration of fluorescein and temperature on the thermal decomposition behavior of fluorescein were examined experimentally and kinetically. It was found that the proportion of decomposed fluorescein to the starting became higher as the initial fluorescein concentration became lower. The kinetics of the thermal decomposition of fluorescein was approximately regarded as first-order from the results in our experiments. On the other hand, the rate equation for thermal decomposition of fluorescein should contain the term of the dissolved oxygen concentration, because the oxidation reaction is greatly related to the decomposition of fluorescein. Therefore, the effect of the dissolved oxygen concentration on thermal decomposition of fluorescein was introduced as the term of the abundance ratio of dissolved oxygen for fluorescein in the rate equation. That also means that the influence of the initial fluorescein concentration on the thermal decomposition of fluorescein is represented as the initial abundance ratio of fluorescein for dissolved oxygen. Then the new kinetics on thermal decomposition of fluorescein was suggested considering the initial concentrations of fluorescein and dissolved oxygen.

For the purpose of examining the adsorption behavior of fluorine on clay minerals, the adsorption equilibrium experiments on fluorine were carried out using several clay minerals. Then various analysis and considerations, as listed in the followings, were done on the basis of the experimental results.1) The adsorbed amount of fluorine per unit mass of clay mineral was ranged as Kaolinite >Saponite >Pyrophyllite, Dickite >Montmorillonite.2) When the mass ratio of clay mineral to liquid was constant, the ratio of adsorption equilibrium concentration of fluorine to initial one became small, as the initial concentration of fluorine was lower.3) It was clear that there was less correlation between the BET specific surface area of the clay minerals and the adsorbed amount of fluorine, because the BET specific surface area was ranged as Saponite > Montmorillonite(Mikawa) > Kaolinite > Montmorillonite(Tsukinuno)> Dickite > Pyrophyllite. 4) The cations such as the alkali metal (Na, K), alkaline earth metal (Ca, Mg), iron, silicon and aluminum, which are contained in the clay minerals, are major chemical components which may be bonded with fluorine. However the quantitative correlation between those each content in the clay minerals and the absorbed amount fluorine could not be recognized. 5) For each clay mineral, the fluorine adsorption data can be arranged clearly in every conditions for the mass ratio of clay mineral to liquid. It was clarified the adsorption isotherm of fluorine on the clay minerals were represented using Freundlich's adsorption equation. 6) The correlation equations which took the mass ratio of clay mineral to liquid into consideration were proposed on the adsorption coefficient and index in Freundlich's adsorption equation. Using both those equations and the values of adsorption parameters obtained in this study, it becomes possible to estimate the adsorbed amount of fluorine on the clay minerals and fluorine concentration in liquid phase.

A seeding method, using colloidal amorphous silica seed made from geothermal fluid, has been tested as a silica scale prevention method. The effect on silica precipitation of the seed was examined experimentally. The results revealed correlations between the surface area and particle diameter of the seed and the mass of silica precipitated, and indicated that the seed exhibited highly reactive surface properties. The seed was confirmed to be of potential use as a silica removal reagent. Application of the seeding method to geothermal plants will guarantee the self-sufficiency of the latter as regards silica scale removal.

Intramolecular transfer of t-Bu3P-ligated Pd catalyst on a carbon–carbon triple bond (C≡C) and nitrogen–nitrogen double bond (N=N) was investigated and compared with the case of a carbon–carbon double bond (C=C), which is resistant to intramolecular transfer of the Pd catalyst. Suzuki–Miyaura coupling reaction of equimolar 4,4’-dibromotolan (1a) or 4,4’-dibromoazobenzene (1b) with 3-isobutoxyphenylboronic acid (2) was carried out in the presence of t-Bu3P-ligated Pd precatalyst 3 and KOH/18-crown-6 as a base at room temperature. In both cases, the diphenyl-substituted product was selectively obtained, indicating that the Pd catalyst walked from one benzene ring to the other through the C≡C or N=N bond after the first substitution with 2. Taking advantage of this finding, we conducted unstoichiometric Suzuki–Miyaura polycondensation of 1.3 equiv. of 1 and 1.0 equiv. of phenylenediboronic acid (ester) 6 in the presence of 3 and CsF/18-crown-6 as a base, obtaining high-molecular-weight conjugated polymer with a boronic acid (ester) moiety at both ends, contrary to the Flory principle.

A liquid-solid swirl fluidized bed (SFB) using centrifugal force is proposed for the application of a seeding method and the enhancement of heat transfer in processes utilizing geothermal energy, and the corresponding flow and heat transfer characteristics are experimentally examined. In the lower part of the SFB, many particles are carried by swirl flow. When liquid velocity is constant, fluidized bed height is lower in SFB than in the conventional fluidized bed (FB). The fluidized bed height in SFB depends on the initial bed height. The heat transfer coefficient is higher in SFB than in FB, and increases with increasing initial bed height.

In a study on prevention of silica scale formation in geothermal applications, two silica removal methods were examined using actual geothermal brine in the Sumikawa and Onuma geothermal areas: one was the addition of silica gel seeds. The other was the addition of aluminum ions. The results for silica gel seed show that the material precipitates on the seeds withdrawn from Sumikawa and model geothermal brine is only silica. On the other hand, the seeds withdrawn from Onuma brine contain not only silica but a small amount of aluminum. In the case of aluminum ion addition, the deposits withdrawn from Sumikawa geothermal brine contain not only silicon and aluminum, but also sodium, potassium and calcium. The composition of the deposits is similar to that of common silica scale. Also, the distribution ratios of these elements between the deposits and the brine are consistent with their common distribution ratios between silica scale and brine. In each case of silica gel seed and aluminum ion addition, the silica removal performance in the actual geothermal brines is found to agree with that in the model ones. Therefore results obtained in model geothermal brine can be applied to actual geothermal brine.

地熱水処理へのシリカゲルシード添加法の応用を想定して, モデル地熱水からのシリカ除去に及ぼすpHおよび操作条件の影響について実験的に検討した.諸条件におけるシリカ擬安定濃度を求め, シリカ除去率の算出に用いた.初期pHの値は5～9の範囲で変えられた.初期シリカ濃度が0.5kg-SiO2・m-3の場合, シリカ除去率は初期pHに伴い高くなる.一方, 初期シリカ濃度が0.7kg-SiO2・m-3の場合, シリカ除去率は初期pHの増加に対して極大値, 極小値を持ち, 初期シリカ濃度が0.9kg-SiO2・m-3の場合, 極小値を持つ.初期シリカ濃度が低い場合, シリカ除去率はプレシーディング時間に影響されないが, 初期シリカ濃度が高い場合, プレシーディング時間に伴いシリカ除去率は減少する.本研究の結果から, 本シード添加法は多くの地熱水処理に適用可能であると推測される.

In order to apply a seeding method using silica gel to silica removal from geothermal brines, the effects of the seed particle diameter, initial specific surface area and initial pore diameter on silica removal are experimentally examined using a model geothermal brine. The silica in the brine is precipitated on the internal surface area of pore in the silica gel seeds. The specific surface area of the seed decreases with increasing quantity of precipitated silica. The effects of the particle diameter on the quantity of the final precipitated silica and on the final specific surface area are hardly seen. The quantity of precipitated silica per unit surface area increases with increasing initial pore diameter, and the silica precipitation rate coefficient increases with decreasing particle diameter and with increasing initial pore diameter. When the quanttty of precipitated silica is small, the silica precipitation rate coefficient is proportional to the -0.72 power of the particle diameter.

地熱水から金属表面へのシリカスケールの析出挙動を明らかにするために, 水晶振動子微量天秤を用いてシリカ析出質量の経時変化に及ぼす初期シリカモノマー濃度・pHの影響を検討した. 初期シリカモノマー濃度が高いほどシリカ析出量は増加した. シリカ析出挙動はpH=6～7を境にして異なった. シリカモノマーに加えて, 比較的低い分子量を持つシリカ重合体も金属表面に析出したが, 非常に高い分子量を持つシリカ重合体はほとんど析出しないと思われた.

The seeding method using silica gel has been suggested as a way to inhibit silica scale formation. In order to improve the silica removal performance, the effect of coaddition of aluminum ion on the silica removal was experimentally examined. When only aluminum ion solution is added in the supersaturated silica solution, the decrease in silica concentration increases with time. This is because aluminum ion produces aluminosilicate deposits. The decrease in silica concentration becomes larger with increasing aluminum ion concentration or with increasing initial pH. When initial pH is 9, the decrease in silica concentration in the coaddition is larger than three times that in the silica gel addition. The coaddition of aluminum ion is found to improve the performance of silica removal when the initial pH is higher than 8.

In order to apply a seeding method to the removal of silica from geothermal brines, the effects of temperature, initial seed concentration and initial silica concentration on the silica removal were experimentally examined. When silica gel seeds are added to a supersaturated silica solution, amorphous silica is precipitated on the pore surface of the seeds and the silica concentration in the solution decreases. The silica removal ratio, which means the ratio of the removed silica to the excess silica, increases with increasing initial seed concentration and increasing temperature. A high silica removal ratio is obtained for relatively low initial silica concentrations (≤0.7 kg-SiO2·m–3). When the initial silica concentration is higher, the silica removal ratio is expected to be enhanced by increasing initial seed concentration. The seeding method is suggested to be effective for the removal of silica in actual geothermal brines.