Decontamination of radioactive waste solutions using pottery

The sorption of microamounts of Eu spiked with ^152,154Eu on the artificial stone, pottery, was studied at varoius conditions. Three kinds of pottery (red, black, and white), in addition to the raw material (potter’s clay) of the red kind, were tested. The pottery shows high sorption power with respect to the radiotracer depending on the kind of pottery. The uptake percentages gradually increase with the contact time, weight of pottery, or pH of the aqueous solution, attaining saturation at certain values. The amounts of Eu³⁺ required for the saturation are 7.38, 7.00, 5.93, and 1.64 (mmol Eu) (g pottery)⁻¹ for raw, red, black, and white samples, respectively. This sequence is parallel to that of the uptake percentage, which is related to the surface area of each material. The sorption presumably occurs via adsorption and ion exchange. The results were applied to decontamination of low-level liquid radioactive waste by filtration through a pot of red pottery; the effluent was free from the radiotracer. Published in Russian in Radiokhimiya, 2006, Vol. 48, No. 4, pp. 352–356. The text was submitted by the authors in English.     

Recovery of nitric acid from waste etching solution using solvent extraction

As part of our efforts to identify effective ways and means to keep source water safe, the concept of risk assessment and management is introduced in this paper to address the issue of risk assessment and management of arsenic in source water in China. Carcinogenic and non-carcinogenic risk are calculated for different concentrations of arsenic in source water using the corrective equation between potential health risk and concentration of arsenic in source water with purification process taken into consideration. It is justified through analyses that risk assessment and management is suitable for China to control pollution of source water. The permissible content of arsenic in source water should be set at 0.01 mg/L at present in China, and necessary risk management measures include control contaminated sources and improvement of purification efficiency.     

Decontamination of liquid radioactive waste concentrates from 60Co using diethyldithiocarbamates

Oxidized bottom residue (BR) from installations for reprocessing trap waters of the Leningrad NPP were treated to remove ⁶⁰Co by coprecipitation with transition metal diethyldithiocarbamates (DDTC). Coprecipitation of ⁶⁰Co with manganese and cobalt diethyldithiocarbamates was examined in relation to pH of solution, temperature, amount of diethyldithiocarbamates, reagent ratio, and number of coprecipitation steps. The effect of diethyldithiocarbamates on the efficiency and conditions of the solution decontamination from ^134,137Cs on nickel potassium ferrocyanides was studied. Oxidative treatment of liquid radioactive waste concentrates to break down organic complexes is a necessary condition for ⁶⁰Co removal by coprecipitation with transition metal diethyldithiocarbamates. From a solution initially containing 56 kBq dm^{−3 60}Co, ⁶⁰Co can be removed to a residual content of 0.12–0.16 kBq dm⁻³ by two-step coprecipitation with Co(DDTC)₂. The coprecipitation with Co(DDTC)₂ does not affect the efficiency of the subsequent removal of Cs radionuclides on nickel potassium ferrocyanides.     

Decontamination of hazardous substances from solid matrices and liquids using supercritical fluids extraction: a review

Supercritical fluid has been adopted as an extraction media to remove various kinds of substances from distinct types of solid matrices since three decades ago. Compared to conventional extraction mode, supercritical fluid extraction technology is preferred because of the flexibility in adjusting its dissolving power and inherent elimination of organic solvent which means reducing time and money needed for subsequent purification. Utilization of this method as an environmental remedial technology, however, has become a trend only after its accomplishment in analytical chemistry was acknowledged. This review tries to summarize in a comprehensive manner the multitude aspects involved in hazardous compounds removal from miscellaneous class of environmental matrices. The industrial adsorbent regeneration using supercritical fluid technology is also discussed. Although, this technology has been successfully realized for environmental remediation in laboratory and on pilot-plant scale, its commercialization attempts still lack significant technology improvement in order to reach the economic feasibility.     

Quantitative analysis of cosmetics waxes by using supercritical fluid extraction (SFE)/supercritical fluid chromatography (SFC) and multivariate data analysis

Waxes play an indispensable role in the formulation of modern cosmetics. Quantitative measurement of the level of different waxes in cosmetics is essential to the understanding of the performance characteristics of the cosmetics. Conventionally, waxes in cosmetics are extracted by Soxhlet extraction using an organic solvent. This extraction is not quantitative. By using SFE, quantitative extraction of the waxes was easily obtained. Due to the complexity of the natural waxes and the coexistence of several types of waxes in a cosmetics product, the level of different waxes in a mixture is best determined by using SFC and multivariate data analysis. Application of this approach in analysis of waxes in mascaras is reported.     

Effect of salting-out agents on nitric acid distribution between liquid and vapor in the course of evaporation of nitric acid radioactive waste

The database on the influence of concentrations of salting-out agents with different cation valence (Li⁺, Na⁺, K⁺, Cs⁺, NH₄⁺, Mg2+, Ca²⁺, Cu²⁺, Zn²⁺, Al³⁺, Fe³⁺, La³⁺, Pu⁴⁺, UO₂²⁺ nitrates) and of H₂SO₄ on the HNO₃ distribution between liquid and vapor at atmospheric pressure was verified and expanded by performing equilibrium evaporation experiments in an evaporator without reflux with circulation of the bottoms. This equilibrium can be described by the equation \(\log {\kern 1pt} {\alpha _H} = - 2.35 + 2\log \;{X_{\Sigma N{O_3}}}\) (where \({X_{\Sigma N{O_3}}}\) is the total concentration of nitrate ions in aqueous solution), taking into account partial binding of water due to hydration of the salting-out agent and apparent hydrolysis of polyvalent cations, and also incomplete dissociation of sulfuric acid. The suggested model is valid at \({X_{\Sigma N{O_3}}}\) from 3 to 16 M (azeotrope); at \({X_{\Sigma N{O_3}}}{\text{ < }}\;3\), Raoult’s law is observed (α_H = const), which is confirmed by a number of examples. In this model, the additivity of the properties of the salting- out agents, taking into account the concentration of “free” water, is assumed, which allows calculation of the composition of the bottoms and distillate when evaporating waste of any composition from radiochemical plants.     

Biodiesel production using waste cooking oil: a waste to energy conversion strategy

In this study, biodiesel was produced using waste cooking oil that was discarded as a waste in the environment. The properties of the feedstock were determined using standard ASTM methods. The transesterification process was implemented to extract the biodiesel, and this process was optimized and standardized by selecting three different parameters: molar ratio (methanol:oil), catalyst concentration (KOH) and reaction temperature. The physicochemical properties of the biodiesel so produced were tested and analyzed using gas chromatography. Biodiesel and diesel were mixed in different volumetric ratios, and the exhaust emission characteristics of the blends were determined by testing the blends on a variable compression ratio engine. The study concluded that waste cooking oil has a great potential for waste to energy process. The highest yield of 93.8% was obtained by optimizing the process. Emission characteristics of CO for B50 blend showed a downward trend while NO _x emission was found to be greater for blending ratios above 10%. B10 showed the best results pertaining to lower NO _x and CO emissions.     

Analysis of fifteen estrogen metabolites using packed column supercritical fluid chromatography-mass spectrometry

Packed column supercritical fluid chromatography with tandem mass spectrometry was used for the separation of estrone, estradiol, estriol, 16-epiestriol, 17-epiestriol, 16-ketoestradiol, 16alpha-hydroxyestrone, 2-methoxyestrone, 4-methoxyestrone, 2-hydroxyestrone-3-methyl ether, 2-methoxyestradiol, 4-methoxyestradiol, 2-hydroxyestrone, 4-hydroxyestrone, and 2-hydroxyestradiol. A gradient of methanol in carbon dioxide (0-30% methanol in 15 min, 2% change/min) at a flow rate of 2 mL/min and cyanopropyl silica column connected in series with a diol column, both 2.1 mm i.d. x 150 mm long, packed with 5-mum spherical silica-based particles, resulted in the separation and quantification of all 15 estrogens in less than 10 min. The limit of detection (LOD) and limit of quantitation (LOQ) of this pSFC MS/MS method was determined to be 0.5 (S/N = 3), and 5 pg, respectively. Compared with RP-HPLC MS analysis of the same mixture in terms of speed of analysis and sensitivity, pSFC MS is much faster, 10 versus 70 min, with comparable LOD and LOQ.     

Determination of volatile and semivolatile mutagens in air using solid absorbents and supercritical fluid extraction

Volatile toxicants may be present in emissions from mobile and stationary sources as well as in ambient air. Methods for collecting and concentrating volatiles from air samples have been developed. Solid-phase adsorbents were compared in their trapping efficiencies for dichloromethane (DCM), ethylene dibromide (EDB), 4-nitroblphenyl (4-NB), 2-nitrofluorene (2-NF), and fluoranthene (FI). Charcoal and Carbosieve were the most efficient media for retaining DCM, while XAD-4 was the best adsorbent for EDB and the aromatic compounds. Extraction of direct spikes of compounds from adsorbents using supercritical carbon dioxide resulted in greater than 90% recovery of EDB and 60-92% recovery of the aromatics. Integration of trapping and desorption methods with the Salmonella microsuspension bioassay was demonstrated with EDB and 4-NB recoveries from air; chemical analysis and bioassay gave comparable results (within 10%).     

Thermodynamic behavior of supercritical fluid mixtures

The recent surge of interest in supercritical extraction has brought the unusual properties of supercritical mixtures into the focus of attention. We discuss some of the properties of binary mixtures in a range around the gas-liquid critical line from the point of view of supercritical solubility. The general thermodynamic relationships that govern the enhancement of supercritical solubility are readily derived by a mathematical method introduced by Ehrenfest. The enhancement is governed by a strong divergence centered at a critical end point. We give the classical and nonclassical power-law behavior of the solubility along the experimental paths of constant temperature or pressure. The factor multiplying the strong divergence contains the partial molar volume or enthalpy of the solute in the supercritical phase. These partials are quite anomalous, especially if the mole fraction of the solute is small. They diverge at the solvent's critical point. We cite experimental evidence of these divergences, especially the results of recent experiments in dilute near-critical salt solutions. The anomalies found in these salt solutions are common to all dilute near-critical mixtures with a nonvolatile second component. We show that on experimentally convenient paths the solubility in a binary liquid mixture near its consolute points is not strongly enhanced. Finally, we sketch a nonclassical model based on the decorated lattice gas that can be used to describe supercritical solubility enhancement at low solubility, with the pure solvent used as a reference.Invited paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

绿色超临界流体的应用研究

超临界流体具有与气体相似的密度、粘度、扩散系数等特性 ,应用领域日益广泛 ,主要有 :萃取、催化反应、结晶、吸附、材料制备、环境保护、食品工业、医药工业、染色工业、色谱分析、生物工程等。论述了超临界流体在这些领域的最新研究成果 ,重点介绍超临界流体在环境保护、染色工业、吸附过程、陶瓷脱脂、材料制备过程中的应用     

Preparation of budesonide-poly (ethylene oxide) solid dispersions using supercritical fluid technology

The purpose of this study was to investigate the possibility of preparing solid dispersions of the poorly soluble budesonide by supercritical fluid (SCF) technique, using poly (ethylene oxide) (PEO) as a hydrophilic carrier. The budesonide-PEO solid dispersions were prepared, using supercritical carbon dioxide (SC CO₂) as the processing medium, and characterized by scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), solubility test and dissolution test in order to understand the influence of the SCF process on the physical status of the drug. The endothermic peak of budesonide in the SCF-treated mixtures was significantly reduced, indicating that budesonide was in amorphous form inside the carrier system. This was further confirmed by SEM and PXRD studies. The enhanced dissolution rates of budesonide were observed from SCF-treated budesonide-PEO mixtures. The amorphous characteristic of the budesonide, the better mixing of drug and PEO powders in the presence of SC CO₂, together with the improved wettability of the drug in PEO, produced a remarkable enhancement of the in vitro drug dissolution rate. Thus, budesonide-PEO solid dispersions with enhanced dissolution rate can be prepared using organic solvent-free SCF process.     

Processing of novel bioactive polymeric matrixes for tissue engineering using supercritical fluid technology

The aim of this study was to develop a new process for the production of bioactive 3D scaffolds using a clean and environmentally friendly technology. The possibility of preparing composite scaffolds of Bioglass^® and a polymeric blend of starch and poly(l-lactic acid) (SPLA50) was evaluated. Supercritical phase-inversion technique was used to prepare inorganic particles loaded starch-based porous composite matrixes in a one-step process for bone tissue engineering purposes.Due to their osteoconductive properties some glasses and ceramics are interesting materials to be used for bone tissue engineering purposes; however their poor mechanical properties create the need of a polymeric support where the inorganic fraction can be dispersed. Samples impregnated with different concentrations of Bioglass^® (10 and 15% wt/wt polymer) were prepared at 200 bar and 55 °C. The presence of Bioglass^® did not affect the porosity or interconnectivity of the polymeric matrixes. Dynamic mechanical analysis has proven that the modulus of the SPLA50 scaffolds increases when glass particles are impregnated within the matrix.In vitro bioactivity studies were carried out using simulated body fluid and the results show that a calcium-phosphate layer started to be formed after only 1 day of immersion. Chemical analysis of the apatite layer formed on the surface of the scaffold was performed by different techniques, namely EDS and FTIR spectroscopy and X-ray diffraction (XRD). The ion concentration in the simulated body fluid was also carried out by ICP analysis. Results suggest that a bone-like apatite layer was formed.This study reports the feasibility of using supercritical fluid technology to process, in one step, a porous matrix loaded with a bioactive material for tissue engineering purposes.     

Design at the nanometre scale of multifunctional materials using supercritical fluid chemical deposition

Recent developments in multifunctional devices show the interest in combining different materials to obtain specific properties. Through supercritical fluid chemical deposition (SFCD), silica spheres, used as a model support, were coated with copper nanoparticles (5-17?nm) with a tuneable amount of coverage (40-80%). The coating process is based on the reduction of metal precursors with hydrogen in a supercritical CO(2)/isopropanol mixture in a temperature range between 100 and 150?°C at 24?MPa. Several parameters were studied such as temperature, residence time or mass ratio of precursor/silica spheres, allowing control of the size of the copper nanoparticles and of the amount of coverage from metal nanoparticles scattered onto the surface to a metal nanoparticle thin film.     

Influence of pressure (temperature) on the nitric acid distribution between the liquid and vapor in the course of evaporation of nitric acid radioactive waste

Analysis of the published dependences of the HNO₃ distribution coefficient between the liquid and vapor in the system with water shows that these dependences are power functions with the exponent depending on the temperature (pressure) and emerge from the azeotropic point. The exponent is inversely proportional to the temperature, and its logarithm is directly proportional to the logarithm of the pressure. The pattern is preserved when a salting-out agent is present in the system and is described similarly when taking into account the hydration and hydrolysis of the cation and the degree of dissociation of sulfuric acid, as shown previously for atmospheric pressure. The dependences obtained are interpreted within the framework of the law of mass action (without activity coefficients) as dilution of the azeotropic compound HNO₃(H₂O)₂ with water with the formation of an associated ionic liquid.     

超临界流体技术制备5-氟尿嘧啶-吲哚美辛-聚乳酸缓释微球

为了考察药物5-氟尿嘧啶(5-Fu)与吲哚美辛(IDMC)的协同作用, 采用超临界流体强制分散溶液技术(SEDS), 以二氯甲烷/二甲亚砜为共溶剂, 制备了复合5-Fu和IDMC的L-聚乳酸(PLLA)微球。利用单因素法探索了制备复合微球的最佳外部条件, 通过表面形貌、 载药量、 粒径分布、 释放性能的检测和体外细胞实验来表征微球的各项性能。结果表明: 当共溶剂二氯甲烷/二甲亚砜比例为30∶1时, 制备该微球的优化条件为39℃、 14MPa; 微球形貌呈类球形, 粒径分布在0.5~5μm; 复合IDMC后微球具有更优良的缓释效果; 载药微球对A549细胞系增殖有明显的抑制作用, 但与复合IDMC前后微球共培养的2组细胞的相对生长速率(RGR)无显著性差异。      

Physico-chemical properties of biodiesel manufactured from waste frying oil using domestic adsorbents

Abstract

We have evaluated the efficiency of sugar cane bagasse ash (SCBA), date palm seed carbon (DPSC), and rice husk ash (RHA) as natural adsorbents and compared them with the synthetic adsorbent Magnesol XL for improving the quality of waste frying oil (WFO) and for the impact on the physicochemical properties of the obtained biodiesel. We measured moisture content, refractive index (RI), density, acid value (AV), iodine value (IV), peroxide value (PV), and saponification value (SV), as well as fatty acid profile. Purification treatments with various levels of adsorbents caused significant (P ≤ 0.05) decreases in free fatty acids (FFAs), PVs, and IVs. The highest yields (86.45 and 87.80%) were observed for biodiesel samples produced from WFO treated with 2% Magnesol and 3% of RHA, respectively, followed by samples treated with 2 and 3% of DPSC or RHA. Pre-treatments caused a significant decrease in the content of C 18:2 linoleic acids, consistent with a significant increase in the content of monounsaturated and saturated fatty acids (MUFA) in the treated samples. The highest oxidation value (COX) (1.30) was observed for biodiesel samples produced from WFO without purification treatments. However, the lowest values (0.44–0.73) were observed for biodiesel samples produced from WFO treated with different levels of adsorbents. Our results indicate that pre-treatments with different levels of adsorbents regenerated the quality of WFO and improved the quality of the obtained biodiesel.     

超声强化超临界流体萃取技术及其最新进展

文章较系统地介绍了超声强化超临界CO2萃取装置的设计,讨论了超声强化超临界CO2萃取技术的应用、萃取模型及其超声强化机理。超声强化与其他强化方法相比较,具有无污染、强化效率高等优点,超声波加入不仅降低了萃取系统的压力、萃取温度以及夹带剂用量和萃取时间,而且提高了萃取率,同时萃取对象的结构并没有发生变化。文章还提出了以后研究的重点。