Modification and Evaluation of Non‐Polar Sorbents for Solid‐Phase Extraction

Abstract

Modification of packings for solid‐phase extraction through high‐frequency low‐temperature plasma treatment is a new method to obtain a wide variety of sorbents. This method is still in the process of investigation and application. In this study, several commercial sorbents have been modified in high‐frequency low‐temperature plasma with the mixed hydrogen/benzene system. The solvation parameter model is used to characterize the sorption properties of commercially available and plasma treated sorbents for solid‐phase extraction. Chromatographic test mixtures from the literature were used to probe hydrophobicity, free silanol interactions and shape selectivity of the sorbents. The physical and retention properties of the plasma treated sorbents indicate their suitability to be used in solid‐phase extraction. Some suggestions concerning the possible practical application of the newly obtained sorbents have been made.     

高温煤气脱硫剂的研究进展

高温煤气净化脱硫技术可使发电效率提高,成本降低,流程简化,是许多国家非常重视的研发工作。可再生金属氧化物与硫化氢或其他硫化物的作用机理及其行为是高温煤气脱硫研究中的关键所在。在已有文献工作的基础上,对国内外高温煤气脱硫剂的研究进行了系统总结,着重介绍了含钙、锌、铁、铜和锰等金属氧化物脱硫剂的研究现状,认为研究重点应从性能单一的金属氧化物转向可耐高温的多功能复合金属氧化物,同时具有再生硫回收的特性。     

可循环再生吸附剂脱汞技术现状及发展趋势

总结了当前燃煤烟气脱汞常用的协同脱汞技术和贵金属、金属氧化物基可再生吸附剂技术发展现状,分析了各方法的优势与存在的问题,对未来磁性可回收吸附剂的发展方向和趋势进行了展望。针对现有脱汞技术效率低、易造成二次污染等缺陷,提出了使用飞灰磁珠制备廉价可回收脱汞吸附剂的新思路。通过大量试验开发了负载Co_3O_4或CuCl_2的磁珠改性方法以增强脱汞能力和抗烟气组分干扰能力,从而能够适用于低氯复杂烟气气氛。设计了改性磁珠吸附剂喷射脱汞工艺流程,可兼顾高效脱汞与低廉的运行成本,并通过磁珠回收再利用彻底避免汞进入环境造成污染。     

Adsorption properties of modified peat toward organic compounds and heavy metals

The adsorption properties of peat modified by mechanical activation in the presence of iron oxide hydroxide were studied. Based on the results of the determination of adsorption activity and microcalorimetric studies, it was established that physical absorption processes predominate on the interaction of the modified peat sorbents with a model organic substance and the aqueous solutions of metal salts. It was demonstrated that new types of sorbents with high sorption properties can be obtained based on peat mechanically activated in the presence of water treatment wastes     

CaO/FA吸收剂高温吸收CO2及穿透特性

利用完全煅烧后的CaO和粉煤灰（Fly Ash）为材料制备了CaO/FA吸收剂。在350~650℃温度范围内对其碳酸化反应特性进行了研究。考察了不同质量比的CaO/FA吸收剂吸收CO2的性能。利用XRD、N2吸附等表征手段对吸收剂反应前后产物进行了表征。结果表明：通过水合反应过程,吸收剂比表面积增大,孔径在5~40nm范围内属于中孔,有利于减小CO2向颗粒内部的扩散阻力。CaO/FA吸收剂CO2吸收量随温度的升高而增加。当CaO与粉煤灰的质量比为3:1时制备的吸收剂具有最好的CO2吸收能力,在650℃时其最大CO2吸收量达到了227.13mg/g。通过多次循环试验后,吸附剂仍保持较高的CO2吸收量与稳定吸收性能。失活模型可以很好地预测CaO/FA吸收剂吸收CO2的过程,并得到了理想的吸收速率常数和失活速率常数。     

新型复合吸附剂的制备及其对雌酚酮的选择性分离

以雌酚酮为模板剂 ,以丙烯酰胺和对乙烯基苯甲酸为单体合成出用于分离雌酚酮的新型复合吸附剂。对制备该吸附剂的最佳工艺条件进行了筛选。实验结果表明 :该吸附剂具有三维网状结构 ;对雌酚酮的最大静态吸附容量为 14 .6mg/ g ;最大比表面积为 2 6 4m2 /g ;最大孔径分布为 12nm左右 ;达到吸附平衡的时间为 8h ;符合Langmiur等温吸附规律。因此对雌酚酮具有较好的记忆选择性能、较高的吸附容量和吸附速率 ,适合用于雌酚酮的选择性分离     

Poly(ethyleneimine) infused and functionalized Torlon-silica hollow fiber sorbents for post-combustion CO2 capture

Organic–inorganic hybrid materials functionalized with amine-containing reagents are emerging as an important class of materials for capturing carbon dioxide from flue gas. Polymeric silica hollow fiber sorbents are fabricated through the proven dry-jet/wet-quench spinning process. In our study, a new technique for functionalizing polymeric silica hollow fiber sorbents with poly(ethyleneimine), followed by a post-spinning infusion step was studied. This two step process introduces a sufficient amount of poly(ethyleneimine) to the polymeric silica hybrid material support to improve the CO₂ sorption capacity due to the added amine groups. The poly(ethyleneimine) infused and functionalized hollow fiber sorbents are also characterized by a thermal gravimetric analyzer (TGA) to assess their CO₂ sorption capacities.     

Investigation on sulfation of modified Ca-based sorbent

When applied for desulfurization in coal combustion process, common Ca-based sorbents have very low Ca conversion and some additives were found can improve the sulfation effect of sorbents greatly. The sulfation characteristics and pore structure of Ca-based sorbent modified by some inorganic compound were investigated in this paper. Although the sulfur capture capability of M-CaO (calcined from modified limestone) greatly exceeds that of N-CaO (calcined from original limestone), the M-CaO sulfation phenomena cannot be explained well based only on pore structure, as has been suggested by some investigators. To find the sulfation mechanism, the crystal structure of M-CaO was measured. Based on experiments and solid-state ions diffusion theory, a new sulfation mechanism is proposed: lattice defects in M-CaO lead to higher calcium conversion. Based on this conclusion, a rule that estimates whether or not a compound can act as a Ca-based sorbent additive is suggested.     

Properties and reactivity of reactivated calcium-based sorbents

Calcium-based sorbents used in the process of high temperature desulfurisation of flue gases are partly regenerable by hydration with steam; the best results are obtained for treatment temperatures of approximately 300 °C. The regeneration process, and the consequent increase in the sorbent consumption can be correlated to the surface characteristics (BET surface area, porosity and pore size distribution) of the sorbents themselves. In particular, the presence of suitable pore structure, also having pores large enough to let molecules easily penetrate the inner part of the sorbent particles, is very important.     

负载型K2CO3/Al2O3吸收剂吸收CO2反应机理

利用热重分析仪、扫描电镜和氮吸附仪对不同粒径的K₂CO₃颗粒和负载型K₂CO₃/Al₂O₃二氧化碳吸收剂的碳酸化特性进行研究。负载后的吸收剂比表面积和孔隙结构得到较大改善,使得碳酸化反应速率和转化率均提高,吸收剂碳酸化特性得到改善。纯K₂CO₃颗粒吸收剂的反应速率和转化率随着粒径的增加而减小,负载型吸收剂的反应速率和转化率随着粒径的增加略增大。研究了不同粒径和反应时间对K₂CO₃/Al₂O₃颗粒微观结构的影响,结果表明K₂CO₃/Al₂O₃颗粒具有较稳定的微观结构。采用负载型粒子模型对K₂CO₃/Al₂O₃吸收剂吸收CO₂碳酸化过程进行研究,所建立的粒子模型计算结果与试验值吻合较好。利用建立的模型对不同CO₂浓度下K₂CO₃/Al₂O₃吸收剂碳酸化反应特性进行模拟计算,模拟结果具备一定的合理性和准确性,为开展进一步研究提供了基础。     

New nanostructured sorbents for desulfurization of natural gas

Desulfurization of natural gas is achieved commercially by absorption with liquid amine solutions. Adsorption technology could potentially replace the solvent extraction process, particularly for the emerging shale gas wells with production rates that are generally lower than that from the large conventional reservoirs, if a superior adsorbent (sorbent) is developed. In this review, we focus our discussion on three types of sorbents: metal-oxide based sorbents, Cu/Ag-based and other commercial sorbents, and amine-grafted silicas. The advantages and disadvantages of each type are analyzed. Possible approaches for future developments to further improve these sorbents are suggested, particularly for the most promising amine-grafted silicas.     

Recovery of pyruvic acid with weakly basic polymeric sorbents

BACKGROUND: Carboxylic acids are among the most important substances that can be manufactured from biomass. However, the recovery of carboxylic acids from fermentation broths presents a challenging separation problem. To avoid the production of waste salts and net consumption of chemicals in the calcium carboxylate salt process, the use of reversible chemical complexation with polymeric sorbents and extractants is attractive for carboxylic acid recovery. Pyruvic acid is widely used in the manufacture of medicines, pesticides and foodstuffs and can be produced by fermentation. Since the acidity of pyruvic acid (pK_a = 2.49) is stronger than that of normal carboxylic acids, and as few reports on the recovery of pyruvic acid are available, the sorption of pyruvic acid from aqueous solution on two types of weakly basic polymeric sorbent, tertiary amine D301R and primary amine D392, was investigated over a wide pH range and at various salt (MgSO₄) concentrations. RESULTS: Overloading adsorption of pyruvic acid on both weakly basic polymeric sorbents occurred, with the overloading of D392 being greater than that of D301R. The adsorption of pyruvic acid on both sorbents was greatly affected by the solution pH and the salt concentration in the aqueous phase. An overloading model was able to predict the experimental uptake data very well. CONCLUSION: Solution pH is one of the most important operating conditions, and both polymeric sorbents D392 and D301R can be used to recover pyruvic acid from dilute aqueous solution with high efficiency at a solution pH around 2. The uptake by D392 is greater than that by D301R owing to steric hindrance of the tertiary amine. Copyright © 2008 Society of Chemical Industry     

电场强化纤维素酶超滤过程研究

将电场强化膜技术应用于纤维素酶超滤过程,在截留相对分子质量为10 000的聚醚砜(PES)超滤膜上分别考察了电场对粗酶粉配制的纤维素酶模拟溶液以及秸秆酶解液的超滤过程的影响.实验结果表明,在2种情况下,电场均可以有效提高超滤过程的渗透通量.当电流强度为150 mA时,相对于无电场(0 mA)的条件下,纤维素酶模拟溶液通...     

Mine water purification with the use of humic preparations

Six carbon-containing sorbents prepared from brown coals were used to purify mine water from the Kizelovskii basin. The main physicochemical characteristics and process regimes of the purification of acidic mine water were determined under laboratory conditions. The initial coals and spent carbon-containing sorbents were characterized. It was found that this purification process resulted in a decrease in the total hardness and sulfate content by 15–27% and to the almost complete removal of harmful metal cations from mine water. The results of the analysis of spent carbon-containing sorbents demonstrate that they can be utilized by thermal oxidation.     

Nontraditional method for the preparation of carbon sorbents from composites based on phenol-formaldehyde resins

A technology for the preparation of high-strength carbon sorbents based on phenol-formaldehyde resins with the use of microwave energy at the stages of the carbonization of starting raw materials, the activation of carbonization products, and the regeneration of spent sorbents was developed. These sorbents were effective in a pulp countercurrent process for the recovery of noble metals. The physicomechanical, structural, and adsorption characteristics of the resulting sorbents were tested.     

Carbon sorbents from waste crumb tires

The applicability of wastes from the chemical utilization of automobile tires as a raw material for the manufacture of carbon sorbents was studied. The thermogravimetric analysis of the thermal degradation of this raw material was performed; the proximate and ultimate analyses were carried out, and a process for the manufacture of crushed and granulated sorbents was developed. The formation of the structural and adsorptive properties of carbon sorbents based on waste crumb tires was studied. It was found that the sorbents were characterized by low and high sorption capacities for substances from aqueous solutions and saturated vapors, respectively. This phenomenon can be explained by the pore structure peculiarities of sorbents from waste crumb tires, which contained supermesopores that turned into capillaries; they are responsible for an entirely different mechanism of absorption: the capillary condensation of vapors.     

Effect of particle agglomeration on heavy metals adsorption by Al- and Ca-based sorbents during fluidized bed incineration

Al- and Ca-based materials can serve as metal sorbents or agglomeration inhibitors in fluidized beds. Although particle agglomeration could affect the adsorption efficiency of metal sorbents, Al- and Ca-based materials have been found to inhibit the particle agglomeration phenomenon during the incineration process. Accordingly, this study emphasizes the effect of particle agglomeration on heavy metal adsorption by Al- and Ca-based sorbents in a fluidized bed. The results show that Al- and Ca-based sorbents inhibit the tendency of particle agglomeration caused by Na. Thus, high concentrations of heavy metals exist mainly in fine particles compared to those present in the large particles when Na is added to the system. However, the addition of Na apparently increased the adsorption efficiency and followed the sequence of Cr > Cd > Pb with an increase in the operating temperature. A comparison of sorbents and Na additive for the relative enrichment factor showed that Na plays an important role in capturing Cr with Al- and Ca-based sorbents. Also, both sorbent adsorption and Na agglomeration are the dominant mechanisms for capturing Cd. The results of adding Na and an Al-based sorbent presented positive effects for Pb adsorption; however, a negative effect was observed with the addition of Na and a Ca-based sorbent at low temperatures.     

Screening Supported Amine Sorbents in the Context of Post-combustion Carbon Capture by Vacuum Swing Adsorption

The aim of this work was to evaluate the performance of three different supported amine sorbents in a 6-step vacuum swing adsorption (VSA) cycle through process simulation and optimization for a representative post-combustion CO₂ capture system. Detailed process optimization revealed that all the adsorbents were able to achieve the desired purity-recovery targets. The best performing adsorbent in terms of productivity was Lewatit with a productivity of 0.48 mol m⁻³ ads s⁻¹. All the adsorbents exhibited similar minimum specific energy value of around 1 MJ kg⁻¹ on an electric basis.     

污水处理厂污泥制备吸附剂对燃煤烟气中汞的吸附性能研究

以城市污染处理厂的活性污泥作为原料,采用不同的活化方式处理制备出环境友好的吸附剂,可供燃煤电厂烟气中除汞.污泥活化后收率在40%～55%之间,物理活化后收率随活化温度的升高而降低,比表面积、孔隙量和吸汞量随活化温度的升高而逐渐增大,但吸汞量随温度升高而急剧下降,说明物理活化的吸附剂主要以物理吸附的方式除汞;经化学活化处理的吸附剂性能好、收率高,比表面积、空隙率和吸汞量显著增加,且除汞效率受温度影响较小,除汞效率高.淋滤实验结果验证了活化处理后的吸附剂对汞具有较高的吸附稳定性,没有二次污染.     

不同钙基吸附剂捕集CO2后的硫酸化反应特性研究

钙基吸附剂进行多次CO₂捕集后,碳酸化效率会大幅衰减,此时的吸附剂能否高效脱硫利用是值得重点关注的问题。鉴于此,筛选了高性能合成钙基吸附剂和天然石灰石吸附剂,通过热重分析仪分析对比其在多循环CO₂捕集后的碳酸化和硫酸化反应性能,采用微粒模型研究其硫酸化反应动力学特征。结果发现,高性能合成钙基吸附剂的碳酸化反应速率和CO₂吸附能力明显高于石灰石吸附剂。在长达500循环的CO₂捕集试验后,高性能合成钙基吸附剂的CO₂吸附能力比石灰石高10倍以上,其SO₂吸附能力相较于石灰石提升约40%。经历多次CO₂捕集反应循环后,2种吸附剂的硫酸化能力均有提升:其中,石灰石吸附剂的提升幅度更大,硫酸化转化率从26%提升到35%,而高性能合成钙基吸附剂的硫酸化转化率则从38%提升到43%。通过微粒模型计算发现,2种吸附剂的硫酸化反应均是与SO₂浓度相关的一级反应,多循环捕集CO₂反应后,石灰石吸附剂的硫酸化反应活化能下降接近30%,而高性能合成钙基吸附剂的硫酸化反应活化能只下降了5%。研究结果说明2种不同钙基吸附剂在进行循环CO₂捕集后,脱硫能力得到了不同程度的提高,且均可以较好地应用于SO₂的脱除。