Additive-free hydrothermal leaching method with low environmental burden for screening of strontium in soil.

In this work, hydrothermal leaching was applied to simulated soils (clay minerals vermiculite, montmorillonite, and kaolinite) and actual soils (Terunuma, Japan) to generate organic acids with the objective to develop an additive-free screening method for determination of Sr in soil. Stable strontium (SrCl2) was adsorbed onto soils for the study, and ten organic acids (citric, L(+)-tartaric, succinic, oxalic, pyruvic, formic, glycolic, lactic, acetic, and propionic) were evaluated for leaching Sr from simulated soils under hydrothermal conditions (120 °C to 200 °C) at concentrations up to 0.3 M. For strontium-adsorbed vermiculite (Sr-V), 0.1 M citric acid was found to be effective for leaching Sr at 150 °C and 1 h treatment time. Based on these results, the formation of organic acids from organic matter in Terunuma soil was studied. Hydrothermal treatment of Terunuma soil produced a maximum amount of organic acids at 200 °C and 0.5 h reaction time. To confirm the possibility for leaching of Sr from Terunuma soil, strontium-adsorbed Terunuma soil (Sr-S) was studied. For Sr-S, hydrothermal treatment at 200 °C for 0.5 h reaction time allowed 40% of the Sr to be leached at room temperature, thus demonstrating an additive-free method for screening of Sr in soil. The additive-free hydrothermal leaching method avoids calcination of solids in the first step of chemical analysis and has application to both routine monitoring of metals in soils and to emergency situations.

Supercritical water pretreatment method for analysis of strontium and uranium in soil (Andosols).

Hydrothermal pretreatment of soils (Andosols) from Ibaraki prefecture (Japan) was used to improve methods for monitoring radioactive Sr and U. Calcined samples were pretreated with subcritical or supercritical water (SCW) followed by extraction with 0.5 M HNO3 solutions. With SCW pretreatment, recoveries of Sr and U were 70% and 40%, respectively. Experimental recoveries obtained can be described by a linear relationship in water density. The proposed method is robust and can lower environmental burden of routine analytical protocols.

Characterization and pharmacokinetic evaluation of microcomposite particles of alpha lipoic acid/hydrogenated colza oil obtained in supercritical carbon dioxide.

The work reported here is an extension of our previous findings in which supercritical composite particles (SCP) of alpha lipoic acid (ALA) masked with hydrogenated colza oil (HCO) named as ALA/HCO/SCP were obtained by the modified particles from gas-saturated solutions (PGSS) process in supercritical carbon dioxide in order to obscure the unpleasant taste and odor of ALA. The masking effect on ALA/HCO/SCP was compared with the widely used mechano-chemically masked formulation of ALA and HCO named as MC-50F. In the present study, ALA/HCO/SCP particles were found to have a significant improvement in regard to bitterness, numbness, and smell compared to ALA bulk powders suggesting they were well coated. The pharmacokinetic parameters for ALA/HCO/SCP and ALA bulk powder gave similar values but were significantly different from those of MC-50F. The amount of ALA absorbed into the body, in the administered ALA/HCO/SCP, was comparable to that absorbed by ALA bulk powder, whereas about half portion of ALA of the MC-50F was not absorbed, because the ALA/HCO/SCP particles were small enough and the particles of MC-50F were relatively large and had smaller specific surface area. Therefore, this study suggested a newly masked candidate may offer functional particles with maintained efficacy.

Nutrient recycle from defatted microalgae (Aurantiochytrium) with hydrothermal treatment for microalgae cultivation.

Defatted heterotrophic microalgae (Aurantiochytrium limacinum SR21) was treated with high temperature water (175-350°C, 10-90min) to obtain nitrogen and phosphorous nutrients as a water soluble fraction (WS). Yields of nitrogen and phosphorous recovered in WS varied from 38 to 100% and from 57 to 99%, respectively. Maximum yields of nitrogen containing compounds in WS were proteins (43%), amino acids (12%) and ammonia (60%) at treatment temperatures of 175, 250 and 350°C, respectively. Maximum yield of phosphorous in WS was 99% at a treatment temperature of 250°C. Cultivation experiments of microalgae (A. limacinum SR21) using WS obtained at 200 and 250°C showed positive growth. Water soluble fractions from hydrothermal treatment of defatted microalgae are effective nitrogen and phosphorous nutrient sources for microalgae cultivation.

Dissolution of mechanically milled chitin in high temperature water.

Chitin is high in crystallinity in its natural form and does not dissolve into high temperature water (HTW), which often leads to decomposition reactions such as hydrolysis, deacetylation and dehydration when hydrothermally processed. In this work, we investigated the reactions of mechanically milled chitin in HTW. Mechanical milling pretreatment combined with HTW treatment improved the liquefaction of chitin giving a maximum water soluble fraction of 80%, where the untreated chitin was 55%. The reaction mechanism of the milled and raw chitin in HTW was shown to be different. For milled chitin, the dissolution of chitin occurred during the heating period to supercritical water conditions (400°C) at short reaction times (1 min). Extended reaction time (10 min) led to decomposition products and aromatic char formation. For raw chitin, the dissolution of chitin in HTW did not occur, due to its high crystallinity, so that liquefaction proceeded via decomposition reactions.

Dissolution and recovery of cellulose from 1-butyl-3-methylimidazolium chloride in presence of water.

The dissolution and recovery of microcrystalline cellulose from 1-butyl-3-methylimidazolium chloride, [bmIm][Cl], were studied. At 90 °C and 5 h dissolution time, the regenerated cellulose could be recovered above 80 wt% with a less than 10% decrease in the value of the viscosity-average degree of polymerization, DP(v), regardless of water content. Recovery ratio and DP(v) of regenerated cellulose at 120 °C decreased with time regardless of water content. The regenerated cellulose after dissolution at 120 °C for 10 h regardless of water content had cellulose II structure. Regenerated cellulose at short dissolution times or low temperature had high amorphous content. Both [bmIm][Cl] and [bmIm][Cl] with water act as a non-derivatizing solvent for microcrystalline cellulose at 90 °C, and as a derivatizing solvent at 120 °C. The main effect of added water on the dissolution of cellulose at high temperature was the promotion of cello-oligosaccharide and levoglucosan formation.