串级萃取理论的发展历程及最新进展

20世纪70年代,徐光宪教授创建了串级萃取理论,建立了稀土串级萃取工艺的最优化参数计算方法。结合计算机技术,又建立了串级萃取工艺的静态参数设计和动态仿真计算技术,实现了工艺设计参数到工业规模生产应用的"一步放大"。近40年来,串级萃取理论及其计算方法始终引领和支撑着中国稀土分离技术的持续发展,同时,萃取工艺技术和装备的进步也不断地促进了该理论的丰富与完善。理论的适用范围由早期的恒定混合萃取比体系发展到非恒定混合萃取比体系,分离流程由两出口发展到三出口、多出口体系,并进一步发展为多入口、多出口的联动萃取工艺;串级萃取工艺的最优化参数计算方法也由两组份体系拓展至多组分分离体系,从单一工艺优化拓展到稀土全分离流程的整体优化。本文简要综述了串级萃取理论发展中的重要工作与应用情况,深入介绍了联动萃取工艺计算及流程优化等方面的最新进展及应用前景。     

联动萃取分离流程设计理论的建立及其运用

稀土是对于现代工业发展至关重要的一组元素,全球对稀土产品的需求量仍在持续增长。然而,稀土的萃取分离生产过程始终伴随环境污染问题,降低酸碱消耗始终是稀土萃取分离理论与技术研究的追求目标。在串级萃取理论的指导下,稀土萃取分离工艺流程的运行经济性不断提升。尤其是2000年后联动萃取分离工艺的出现,使得稀土萃取分离流程的酸碱消耗水平显著降低。联动萃取工艺在逐步成为中国稀土分离工业基本技术的同时,也极大促进了串级萃取理论的发展。近年,以邻级杂质比概念的提出和分析为基础建立了联动萃取分离流程设计理论,其中推导得到的系列理论公式可用于设计具有理论最小萃取量和最小洗涤量的多组份联动萃取全分离流程,无需通过动态模拟和静态计算即可实现。该理论方法也可用于非联动萃取流程优化工艺参数的计算。另外,理论公式推导和运用的同时也增进了对稀土萃取分离过程物料运行规律的理解。     

三元稀土萃取分离工艺中有效分离系数的研究

本文通过计算机模拟计算,对恒定混合萃取比的三元稀土萃取分离工艺中有效分离系数的变化规律进行了研究,并在串级萃取理论的基础上提出了一种采用有效分离系数确定三元稀土萃取分离工艺参数的方法。     

串级萃取理论之联动萃取分离工艺设计:Ⅰ、串级萃取分离过程的邻级杂质比

具有显著流程优化优势的联动萃取分离技术已成为中国稀土分离企业的主流技术,其工艺参数设计理论研究对促进技术进步具有十分重要的指导意义。近年来作者发展了串级萃取理论,给出了联动萃取流程最小萃取量和最小洗涤量理论下限的计算方法,解决了联动萃取分离流程优化过程中的基础理论问题。相关工作拟连载发表。首先引入邻级杂质比的概念,推导得到了邻级杂质比公式,分析了邻级杂质比的工艺意义,为后续联动萃取分离单元最小萃取量和最小洗涤量等公式的推导奠定基础。     

多组份稀土体系串级萃取分离理论(Ⅰ)多组份稀土体系串级萃取分离的静态平衡出口级组成的计算

对多组份稀土体系串级萃取分离的静态平衡出口级组成计算进行了研究, 并给出了多组份稀土体系串级萃取分离的静态平衡出口级组成的计算公式, 利用本文给出的计算公式可以比较精确, 比较方便地计算出多组份稀土体系分离时出口级中各组份数的组成.     

多组份多出口稀土串级萃取静态优化设计研究(Ⅱ)静态程序设计及动态仿真验证

基于多组分多出口稀土串级萃取优化参数的静态设计算法, 设计了相应的计算程序, 采用该程序针对某稀土分离实例进行了静态参数计算, 并对最优化工艺参数进行了动态仿真验证. 结果表明, 采用该静态设计算法的软件在参数计算中运行快速、结果准确, 完全可满足萃取分离工艺的参数设计要求.     

稀土萃取分离过程自动控制研究现状及发展趋势

在简要描述稀土萃取分离生产过程的基础上,综述了目前国内外稀土萃取分离过程中稀土元素成分在线检测的方法、装置及其应用现状;稀土串级萃取分离生产过程的计算机流程模拟以及稀土萃取生产过程的自动控制方法、技术及其应用现状.指出了稀土元素组分含量的软测量方法,以综合生产指标为目标的稀土萃取分离生产过程优化控制方法以及由生产过程管理系统和过程控制系统两层结构组成的稀土萃取分离生产过程综合自动化系统已成为稀土萃取分离生产过程自动化未来发展的方向.     

串级萃取理论Ⅷ——两组分串级萃取体系回流过程的研究

本文提出了恒定混合萃取比体系串级萃取分离的回流启动模式。对全回流和单回流启动方式的动态过程作了定量的模拟计算。对分离系数小、产品纯度要求高、原料中组成比相差大的串级萃取体系,采用回流启动可以有效地缩短体系达到稳态的时间,并可基本上避免在常规启动中所产生的不合格产品。本理论已在稀土分离工业实践中得到了验证和应用。     

串级萃取量优化理论和精确计算优化萃取比新方程

稀土;串级萃取量优化理论和精确计算优化萃取比新方程     

任意组分两出口体系串级萃取静态优化设计研究

提出了任意组分体系溶剂萃取串级分离工艺的精确算法。并推导了溶剂萃取串级分离萃取平衡和物料平衡关系,给出了两端出口组分组成的最简通用计算公式,解决了静态算法设计的关键问题。利用萃取平衡和物料平衡关系进行静态递推,实现了任意组分体系静态精确设计。这一方法可以解决目前任意组分体系两出口串级分离的理论优化设计问题。     

对氨基酚络合萃取机理的探讨

对氨基酚络合萃取机理的探讨;对氨基酚; 络合萃取; 萃取机理; 萃取反应热     

超声辅助液液萃取法提取烟用香精成分的研究

采用超声辅助液液萃取法(ULLE)提取某品牌烟用香精成分,GC-MS对其进行分析,研究了不同萃取剂、萃取时间和萃取温度对分析结果的影响,初步确定了最佳条件为:以二氯甲烷为萃取剂,饱和NaCl溶液作水相,室温下超声萃取5 min.又分别与同时蒸馏萃取法(SDE)和传统的液液萃取法(LLE)作以比较,对ULLE法和SDE法鉴定出的化学成分、重现性和定量值进行了对比.结果表明:超声辅助液液萃取具有操作简便、快速、节能、萃取效率高、重现性好等特点,适合于烟用香精成分的提取.     

杂粮中总黄酮的提取及含量测定的实验设计

通过学生分组，采用溶剂提取法，超声提取法和微波提取法等提取方法，测定了小米、糜子、青稞、荞麦和高梁等杂粮中黄酮含量，结果表明5种杂粮中，青稞中总黄酮的含量最高。该综合实验能够锻炼大学生运用所学实验技术解决实际问题的能力，适合作为高年级本科综合实验项目开设。     

Comparison of alternative and conventional extraction techniques for the determination of zearalenone in corn

Naturally contaminated corn samples of different origin were extracted using two conventional techniques (blending and shaking) and three alternative approaches (ultrasonic extraction, accelerated solvent extraction, and microwave-assisted extraction). Use of the same extraction mixture for all trials enabled the efficiency of the various extraction techniques to be compared. Extracts were filtered and directly analyzed by LC–ESI–MS, without further clean-up. The yield from the alternative extraction techniques showed efficiency to be higher than for conventional techniques. In particular, microwave-assisted extraction was slightly superior to other techniques.     

Focused microwave aqueous extraction of chlorophenols from solid matrices and their analysis by chromatographic techniques

Open-vessel focused microwave (FMW) extraction with a purely aqueous carbonate solution was used for the extraction of chlorophenols from various solid matrices. After SPE on C18-bonded silica, the analytes were determined as such by LC-UV or, as their acetyl derivatives, by GC-ECD. The FMW aqueous extraction is efficient and rapid and no organic solvents are used. PCP was detected in several solid samples, with recoveries of 101-115% (RSD, 2-4%) relative to Soxhlet extraction. Similar recoveries were obtained for the other chlorophenols for spiked samples.     

Improved extraction and clean-up of imidazolinone herbicides from soil solutions using different solid-phase sorbents

Extraction and quantification of herbicide residues from soil are important in understanding the behaviour of persistent herbicides. This research investigated extraction and clean-up methods for imidazolinone herbicides from soil and soil amended with organic material. A series of solvent mixes, pH conditions and sorbents was tested. Across three imidazolinone herbicides: imazapyr, imazethapyr and imazaquin, 0.5 M NaOH extraction gave greater than 90% recovery from soil samples; however, 0.5 M NaOH:MeOH (80:20) resulted in higher recovery for imazaquin, but not for the other two herbicides. Of the sorbents tested, the use of chromatographic mode sequencing using C₁₈ and SCX sorbents provided consistent high (>85%) recovery of all three herbicides from soil and separation of the herbicides from other soil components by high performance liquid chromatography (HPLC). These two methods will allow high recovery of these imidazolinone herbicides from soil and have the ability to detect these herbicides without interference from other soil components.     

Comparative study of optimised BCR sequential extraction scheme and acid leaching of elements in the certified reference material NIST 2711

The optimised BCR sequential extraction procedure and a 4 h 1 mol L⁻¹ HCl partial extraction have been performed on the NIST 2711 reference material for a suite of 12 elements (Cd, Sb, Pb, Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, As) using magnetic sector ICP-MS. A pseudo-total aqua regia digest of NIST 2711 has also been undertaken for quality assurance purposes, and comparison of the sum of the four BCR fractions, which included an aqua regia digest on the residue, with the pseudo-total aqua regia digest has been used to assess the accuracy of the BCR partitioning approach. As a result of this work, discrepancies between previous studies about BCR partitioning of elements in NIST 2711 have been discussed and an increase in confidence about the use of BCR partitioning scheme on seven elements (Cd, Pb, Al, Mn, Fe, Cu, Zn) in this standard material has been obtained. On the other hand, BCR partitioning for Sb, Cr, Co, Ni and As has been provided for the first time. Partial extraction results are also reported for the same 12 elements analysed by the optimised BCR procedure, with the partial extraction results exhibiting a strong correlation with the sum of the three labile steps of the BCR procedure.     

Comparison of different extraction techniques for the determination of chlorinated pesticides in animal feed

The performances of Soxhlet extraction, dive-in Soxhlet extraction, microwave-assisted extraction (MAE), accelerated solvent extraction (ASE), fluidized-bed extraction (FBE), and ultrasonic extraction (UE) for the analysis of organochlorine pesticides in animal feed have been investigated. ASE and MAE provided significantly better extraction efficiency than Soxhlet extraction. The concentrations were 126.7 and 114.8%, respectively, of the values obtained by classical Soxhlet extraction, whereas the results from FBE and dive-in Soxhlet were comparable with those from the standard Soxhlet procedure. The reproducibility of FBE was the best, with RSDs ranging from 0.3 to 3.9%. Under the investigated operation conditions UE was not efficient, with the recoveries of target compounds being about 50% less than Soxhlet. Additionally, the performances of Soxhlet, dive-in Soxhlet, MAE, ASE and FBE were validated by determination of the certified reference material BCR-115. The results from the extraction techniques were in good agreement with the certified values.     

Optimization of Microwave-Assisted Extraction for the Determination of Organic Flame Retardants in Acrylonitrile Butadiene Styrene

The efficiency of microwave-assisted extraction was evaluated for the determination of flame retardants in acrylonitrile butadiene styrene by optimization of the temperature, time, and solvent. A quality control sample containing 500 milligrams per kilogram Dechlorane Plus, 1000 milligrams per kilogram tetrabromobisphenol A, and 1000 milligrams per kilogram triphenyl phosphate was employed. The flame retardant concentrations obtained by microwave-assisted extraction at 120 degrees Celsius for ten minutes in tetrahydrofuran were in agreement with those for the quality control sample. The efficiency of microwave-assisted extraction was comparable to ultrasonic and Soxhlet extraction used as reference techniques. In addition, the repeatabilities of the analyses, represented as relative standard deviations, were comparable: 0.8–3.4 percent for microwave-assisted extraction, 0.3–3.3 percent for ultrasonic extraction, and 0.2–8.5 percent for Soxhlet extraction. These results suggest that microwave-assisted extraction is suitable for the determination of Dechlorane Plus, tetrabromobisphenol A, and triphenyl phosphate in acrylonitrile butadiene styrene.     

A Critical Review on Pulsed Electric Field: A Novel Technology for the Extraction of Phytoconstituents

Different parts of a plant (seeds, fruits, flower, leaves, stem, and roots) contain numerous biologically active compounds called “phytoconstituents” that consist of phenolics, minerals, amino acids, and vitamins. The conventional techniques applied to extract these phytoconstituents have several drawbacks including poor performance, low yields, more solvent use, long processing time, and thermally degrading by-products. In contrast, modern and advanced extraction nonthermal technologies such as pulsed electric field (PEF) assist in easier and efficient identification, characterization, and analysis of bioactive ingredients. Other advantages of PEF include cost-efficacy, less time, and solvent consumption with improved yields. This review covers the applications of PEF to obtain bioactive components, essential oils, proteins, pectin, and other important materials from various parts of the plant. Numerous studies compiled in the current evaluation concluded PEF as the best solution to extract phytoconstituents used in the food and pharmaceutical industries. PEF-assisted extraction leads to a higher yield, utilizes less solvents and energy, and it saves a lot of time compared to traditional extraction methods. PEF extraction design should be safe and efficient enough to prevent the degradation of phytoconstituents and oils.