Nickel(Ⅱ) removal from water using silica-based hybrid adsorbents:Fabrication and adsorption kinetics

A series of novel silica-based hybrid adsorbents were prepared by the crosslinking reaction of N-[3- （trimethoxysilyl）propyl] ethylene diamine （TMSPEDA） with epichlorohydrin （ECH） via a sol-gel process. Fourier transform infrared （FTIR） spectra confirmed that the reaction occurred. TGA curves showed that the thermal stability of these hybrid adsorbents reached as high as 180 ℃. As a typical example, the adsorption performance of nickel（U） ions onto an adsorbent （the volume ratio of TMSPEDA and ECH was 4：1 ） was explored. It was found that the adsorption of nickel（Ⅱ） ions onto this adsorbent followed the Lagergren pseudo-second-order kinetic model. The investigation of the adsorption mechanism demonstrated that nickel（Ⅱ） adsorption was chiefly controlled by diffusion-chemisorption, suggesting that more diffusion processes were involved in the adsorption of nickel（Ⅱ） ions onto this type of adsorbents. Desorption experiment indicates that these hybrid adsorbents can be regenerated. These findings reveal that this type of silica-based hybrid adsorbent is promising in the separation and recovery of nickel（Ⅱ） ions from Ni-containing wastewater or contaminated water.

Sorption Kinetics, Isotherm and Thermodynamic Modeling of Defluoridation of Ground Water Using Natural Adsorbents

The aim of study is to investigate the removal ability of some natural adsorbents for fluoride ion from aqueous solution. The batch dynamic adsorption method was carried out at neutral pH as the functions of contact time, adsorbent dose, adsorbate concentration, temperature and effect of co-anions, which are commonly present in water. The sorption kinetics and equilibrium adsorption isotherms of fluoride on natural adsorbing materials had been investigated at afore-mentioned optimized. Equilibrium adsorption isotherms, viz., Freundlich and Langmuir isotherms were investigated. Lagergren and Morris-Weber kinetic equations were employed to find the rate constants. The negative enthalpy ΔH = -46.54 KJ·mol-1 and Gibbs free energy calculated was ΔG288-333—(2.07785, 3.08966, 4.1064, 4.90716 and 5.38036 KJ·mol-1) respectively, envisage exothermic and spontaneous nature of sorption.

Boosting kinetic separation of ethylene and ethane on microporous materials via crystal size control

The adsorptive separation of C_(2)H_(4)and C_(2)H_(6),as an alternative to distillation units consuming high energy,is a promising yet challenging research.The great similarity in the molecular size of C_(2)H_(4)and C_(2)H_(6)brings challenges to the regulation of adsorbents to realize efficient dynamic separation.Herein,we reported the enhancement of the kinetic separation of C_(2)H_(4)/C_(2)H_(6)by controlling the crystal size of ZnAtzPO_(4)(Atz=3-amino-1,2,4-triazole)to amplify the diffusion difference of C_(2)H_(4)and C_(2)H_(6).Through adjusting the synthesis temperature,reactant concentration,and ligands/metal ions molar ratio,ZnAtzPO4 crystals with different sizes were obtained.Both single-component kinetic adsorption tests and binary-component dynamic breakthrough experiments confirmed the enhancement of the dynamic separation of C_(2)H_(4)/C_(2)H_(6)with the increase in the crystal size of ZnAtzPO_(4).The separation selectivity of C_(2)H_(4)/C_(2)H_(6)increased from 1.3 to 98.5 with the increase in the crystal size of ZnAtzPO_(4).This work demonstrated the role of morphology and size control of adsorbent crystals in the improvement of the C_(2)H_(4)/C_(2)H_(6)kinetic separation performance.

Adsorption thermodynamics and kinetic investigation of aromatic amphoteric compounds onto different polymeric adsorbents

The adsorption behavior ofp-aminobenzoic acid and o-aminobenzoic acid onto the different polymeric adsorbents was systematically investigated as a function of the solution concentration and temperature. Experimental results indicated that the equilibrium adsorption data of the four polymeric adsorbents fitted well in the Freundlich isotherm. The adsorption capacity of multi-functional polymeric adsorbent NJ-99 was the highest, which might be attributed to the strong hydrogen-bonding interaction between the amino groups on the resin and the carboxyl group of aminobenzoic acid. The adsorption capacity of o-aminobenzoic acid onto any adsorbent was higher than p-aminobenzoic acid. Thermodynamic studies suggested the exothermic, spontaneous physical adsorption process. Adsorption kinetics results showed that the adsorption followed the pseudo-second-order kinetics model and the intraparticle mass transfer process was the rate-controlling step.

Implications from protein uptake kinetics onto dextran-grafted Sepharose FF coupled with ion exchange and affinity ligands

Our previous studies have reported the presence of "chain delivery" effects of protein adsorption onto ion exchangers with polymer-grafted ion-exchange groups, such as dextran-grafted and poly(ethylenimine)-modified Sepharose gels. However, it is unclear if the "chain delivery" occurs on affinity adsorption with specific interactions. This work is designed to address this issue. A dextran-grafted Sepharose gel was prepared, and then the matrix was modified using diethylaminoethyl, a typical ion-exchange group, or octapeptide(FYCHWQDE), an affinity ligand for human immunoglobulin G(h Ig G) to prepare ion-exchange or affinity adsorbents, respectively.Results of h Ig G adsorption showed that the uptake rate represented by the effective diffusivity of h Ig G onto the dextran-grafted ion exchangers was obviously enhanced by the dextran grafting, indicating the presence of"chain delivery" of the bound proteins on the charged groups on the dextran chains. By contrast, the effective diffusivity of h Ig G changed little as ligand density increased on the dextran-grafted FYCHWQDE adsorbents.Their adsorption capacities decreased and effective diffusivities were not accelerated by the dextran grafting.Thus, this work clarified that grafted dextran could not accelerate h Ig G uptake rate on the affinity resins, or in other words, chain delivery did not occur on the specific interaction-based affinity adsorption.

Kinetic and Thermodynamic Studies of Acid Scarlet 3R Adsorption onto Low-cost Adsorbent Developed from Sludge and Straw

A low-cost adsorbent was prepared from sludge and straw by pyrolysis in a dried state with the surface area of the adsorbent of 829.49 ma. g-l, micropore volume of 0.176 cm2·g-1 and average pore radius of 5.0 nm. The kinetic, equilibrium isotherm and thermodynamic characteristics of trisodium 1-（1-naphthylazo）-2-hydroxynaphthalene- 4＇,6,8-trisulphonate （acid scarlet 3R） onto the adsorbent from sludge and straw were investigated. The results indicated that the pseudo second order adsorption was the predominant adsorption mechanism of acid scarlet 3R. Thus, the adsorption phenomenon was suggested as a chemical process. The adsorption data were fitted better with Langmuir model than Freundlich model, indicating that the adsorption of acid scarlet 3R belonged to the monolayer adsorption and mainly occurred in micropores.

Removal of strontium ions from aqueous solution using hybrid membranes: Kinetics and thermodynamics

The removal of radionuclide from radioactive wastewater has captured much attention.Strontium-90 is one of the major radionuclides.To develop a new type of adsorbents to remove strontium ions from the radioactive wastewater,in this study,novel hybrid membranes were prepared and characterized.The adsorption kinetics,thermodynamic parameters of AG,AH and AS,as well as surface SEM and EDS images were used to investigate the removal of strontium ions from stimulated radioactive wastewater using the previously prepared hybrid membranes as efficient adsorbents.The study of kinetic model confirmed that the adsorption of strontium ions on these hybrid membranes followed the Lagergren pseudo-second order model.Moreover,it was proved that the adsorption of strontium ions on these samples was solely controlled by intraparticle diffusion.The negative values of AG and the positive values of AH indicated that the adsorption of strontium ions on samples A-D is a spontaneous and endothermic process in nature.Furthermore,surface SEM and DES images give significant evidence to confirm the existence of strontium ions on the surface of the adsorbed samples.These findings demonstrate that these hybrid membranes are promising adsorbents for the removal of strontium ions from aqueous solution and can be potentially applied in the adsorptive separation of radionuclides from the radioactive wastewater.

Retention Profile of Zn²⁺and Ni²⁺Ions from Wastewater onto Coffee Husk: Kinetics and Thermodynamic Study

In this work, Coffee husk (CH) was used as a solid phase extractor (SPE) for removal and/or minimization of Zn2+ and Ni2+ ions in aqueous media. XRD, FESEM and FTIR analysis of the SPE were performed for surface morphology and function groups characterisation. Batch mode adsorption studies were performed by varying the operational parameters such as adsorbent dose, solution pH, initial analyte concentration and contact time. The equilibrium data of both analytes was found a better fit with the Langmuir and Freundlich isotherm models. The qm of Langmuir for Zn2+ and Ni2+ ions were 12.987 and 11.11 mg/g, respectively. The adsorption capacities of the CH adsorbent towards Zn2+ and Ni2+ resulted of 12.53 and 10.33 mg/g, respectively. In addition, the kinetic data of Zn2+ and Ni2+ ions uptake revealed that the present system fitted well with pseudo-second-order kinetic model (R2 > 0.99). Thermodynamic studies showed that the retention step was exothermic, and spontaneous in nature. The results indicated that the coffee husk provides an effective and economical approach in highly reducing or almost eradication of both metals Zn2+ and Ni2+ from the aqueous solution.

Synthesis of Li^+ adsorbent(H_2TiO_3) and its adsorption properties

H2TiO3 was obtained from the acid-modified adsorbent precursor Li2TiO3,which was synthesized by a solid-phase reaction between TiO2 and Li2CO3.The extraction ratio of Li＋ from Li2TiO3 was 98.86%,almost with no Ti4＋ extracted.The effects of lithium titanium ratio,calcining temperature and time were investigated on the synthesis of Li2TiO3.Li2TiO3,H2TiO3 and the adsorbed Li＋ adsorbent were characterized by XRD and SEM.The lithium adsorption properties were investigated by the adsorption kinetics and adsorption isotherm.The results indicate that H2TiO3 has an excellent adsorptive capacity for Li＋.Two simplified kinetic models including the pseudo-first-order and pseudo-second-order equations were selected to follow the adsorption processes.The rate constants of adsorption for these kinetic models were calculated.The results show that the adsorption process can be described by the pseudo-second-order equation,and the process is proved to be a chemical adsorption.The adsorption process that H2TiO3 adsorbs Li＋ in LiCl solution well fits the Langmuir equation with monolayer adsorption.

含膦多孔有机聚合物负载氧化镁的制备及其CO_(2)吸附性能

MgO吸附剂因其成本低廉、来源广泛、再生能耗低等优势在CO_(2)吸附领域应用广泛,但比表面积低限制了其吸附性能。以高表面积、多级孔结构的含膦多孔有机聚合物POL-PPH_(3)为载体,采用浸渍煅烧法和超声煅烧法制备得到POL-PPH_(3)负载的MgO吸附剂(MgO/POL-PPH_(3)),用于CO_(2)捕集。探究制备方法、煅烧温度、煅烧时间等制备条件对MgO/POL-PPH_(3)吸附剂上CO_(2)吸附性能的影响。研究发现,浸渍煅烧法优于超声煅烧法,且随着煅烧温度和煅烧时间增加,MgO/POL-PPH_(3)样品上CO_(2)吸附容量逐渐降低。采用浸渍煅烧法,煅烧温度300℃,煅烧时间1 h时,MgO/POL-PPH_(3)-300-1吸附剂上获得最优CO_(2)吸附量,达0.55 mmol/g。在组成为12%CO_(2),其余为氮气的模拟烟道气中,MgO/POL-PPH_(3)-300-1吸附剂上CO_(2)吸附容量达0.02 mmol/g,200℃吸附60 min,370℃脱附15 min条件下,该吸附剂稳定循环使用5次后,CO_(2)吸附容量仍保持不变。结合N 2物理吸附、热重、FT-IR、XRD、SEM-EDX等表征手段,阐明MgO/POL-PPH_(3)吸附剂上吸附CO_(2)的构效关系。动力学模型分析表明采用浸渍煅烧法不同煅烧温度下获得的3种吸附剂上CO_(2)吸附以物理吸附为主,而不同煅烧时间下获得的3种吸附剂包括MgO/POL-PPH_(3)-300-1吸附剂上CO_(2)吸附行为以化学吸附为主。高比表面积及多级孔道结构有利于暴露更多的活性位点及CO_(2)传输与扩散,进而增大MgO/POL-PPH_(3)吸附剂的CO_(2)吸附容量。MgO在载体上高度分散也有利于增强与CO_(2)的接触,以加快CO_(2)吸附速率。

PEI@SA微球制备及其对甲基蓝的吸附研究

以海藻酸钠(SA)为基材,通过交联法制备聚乙烯亚胺(PEI)改性吸附剂PEI@SA,研究其对甲基蓝(MB)的吸附性能。采用SEM和FTIR对吸附剂表面形貌和化学结构进行表征。考察pH值、初始染料浓度、吸附时间对吸附性能的影响,然后对吸附过程进行等温线模型和动力学模型拟合。结果表明:PEI@SA对MB的吸附符合Langmuir吸附模型和准二级动力学模型,吸附过程为单分子层吸附,以化学吸附为主。25°C时对MB最大吸附量为88.34 mg/g,是未改性SA的10倍。

钙改性水葫芦基生物炭吸附水中敌草隆的效能与机理

以水葫芦为原料、CaCl_(2)为改性剂,通过一步热解法制备了钙改性水葫芦基生物炭(CWHBC),基于表征技术分析了其表面形貌、比表面积、孔径分布、官能团组成等物化性能,并探究了其吸附去除水中敌草隆的效能与机理。结果表明,CWHBC比未改性生物炭(WHBC)具有更大的比表面积、更丰富的孔隙结构、更多的含氧官能团、更强的亲水性,这些物化性能的改变增强了生物炭的吸附能力。CWHBC对水中敌草隆的吸附符合准二级吸附动力学模型和Langmuir吸附等温线模型,表明该吸附以单层化学吸附为主,主要吸附机理为氢键作用、π-π作用和表面络合。单因素试验结果表明,CWHBC在各种条件下均具有良好的吸附性能,采用0.2mol/LHCl对其进行5次吸附/解吸循环后的吸附容量仍高达初次吸附容量的94.62%。因此,使用一步热解法制备的CWHBC可有效去除水中敌草隆,且具有较好的环境适应能力和重复使用性能。该研究提供了一种低成本、高效的吸附材料,能有效实现水葫芦的资源化利用,具有良好的工程应用前景与潜力。

新催化体系硫代硫酸盐法提金

为构建浸金效果好、硫代硫酸盐消耗低且浸出液中的金能被高效回收的新型浸金体系,比较了不同金属离子与有机配体组合催化硫代硫酸盐浸金的效果,并采用树脂吸附法回收浸出液中的金。结果表明,Ni2+-甘氨酸-硫代硫酸盐体系的Au浸出效果好,Au浸出率和硫代硫酸盐消耗分别为89.72%和15.28 kg/t。该体系浸金过程中,甘氨酸催化Au^(+)与S_(2)O_(3)^(2-)配位以及在碱性条件下稳定Ni^(2+),Ni(C_(2)H_(4)NO_(2))_(2)^(0)催化O_(2)的还原。采用树脂吸附法回收金时,浸出液中Ni离子几乎不会在树脂上吸附,不与Au离子产生竞争吸附,Au吸附率达98.13%;载金树脂解吸时只需采用简单的一段工艺,即可直接解吸Au。

三种废渣吸附剂对稀土氨氮废水的吸附动力学研究

以改性的粉煤灰、煤矸石、水淬渣作为材料,研究了三种废渣稀土氨氮废水中氨氮的吸附性能及其吸附动力学行为,讨论了吸附平衡时间、反应级数、吸附速率控制步骤,并将三种废渣的吸附性能进行比较。实验结果表明:粉煤灰与水淬渣较先达到吸附平衡,煤矸石与准二级动力学拟合直线的相关性最好为0.997 8,化学反应是改性粉煤灰、改性水淬渣吸附氨氮的主要控制步骤,液膜扩散、颗粒扩散是改性煤矸石吸附氨氮的主要控制步骤。

季铵基吸附剂CO_(2)变湿捕集-释放机制及相关材料研究进展

变湿吸附作为一种新型的CO_(2)捕集技术,具有受水分变化驱动捕集-释放CO_(2)的特点,可有效降低CO_(2)捕集能耗和运行成本。阐述了季铵基吸附剂的变湿吸附技术机理,以及热力学、动力学角度的作用机制;介绍了影响吸附剂性能的因素;归纳了近年来吸附剂合成改性方法及研究进展;最后总结了该领域当前面临的挑战并指出了发展趋势。季铵基吸附剂吸附CO_(2)的过程通过水蒸发驱动并受水分波动影响。当吸附剂负载二价及三价酸根阴离子,亲水/疏水层间距和阳离子间距均较小时,CO_(2)吸附性能较强。可通过定向调控孔隙结构制备更小粒径、更丰富孔隙度和更高比表面积的吸附剂材料。此外,可通过强化季铵化或双季铵化等手段将季铵基官能团进行化学嫁接,以提高活性位点的密度并高效利用。目前变湿吸附技术处于发展阶段,在保持吸附剂较高比表面积和官能团利用率的基础上,改善吸附容量和循环速率是面向实际应用的必然需求;其规模化应用、捕集能耗的降低、环境耐受性的提高,以及捕集后CO_(2)的处理也是亟待研究的重要方向。

黄芪废渣磁性碳化吸附剂制备及其对水中四环素的吸附动力学研究

以黄芪废渣和氯化铁混合物为原料,采用限氧热解法在700℃焙烧,制备黄芪废渣磁性碳化吸附剂(HC),研究其对四环素的吸附性能,考察的实验条件主要有四环素浓度、溶液pH、吸附剂用量、震荡时间。得出实验结论:在四环素溶液浓度140.0 mg/L、溶液pH5.6、黄芪废渣磁性碳化吸附剂的添加量2.5 g/L、震荡搅拌时间50 min时,吸附率最高可达94.1%,吸附量为52.696 mg/g。动力学分析实验结果表明黄芪废渣磁性碳化吸附剂(HC)对水中四环素的吸附过程与伪二级动力学模型更为一致。

High adsorption selectivity of activated carbon and carbon molecular sieve boosting CO_(2)/N_(2) and CH_(4)/N_(2) separation

Flue gas and coal bed methane are two important sources of greenhouse gases.Pressure swing adsorption process has a wide range of application in the field of gas separation,and the selection of adsorbent is crucial.In this regard,in order to assess the better adsorbent for separating CO_(2) from flue gas and CH_(4) from coal bed methane,adsorption isotherms of CO_(2),CH_(4) and N_(2) on activated carbon and carbon molecular sieve are measured at 303.15,318.15 and 333.15 K,and up to 250 kPa.The experimental data fit better with Langmuir 2 compared to Langmuir 3 and Langmuir-Freundlich models,and Clausius-Clapeyron equation was used to calculate the isosteric heat.Both the order of the adsorbed amount and the adsorption heat on the two adsorbents are CO_(2)>CH_(4)>N_(2).The adsorption kinetics are calculated by the pseudo-first kinetic model,and the order of adsorption rates on activated carbon is N_(2)-CH_(4)>CO_(2),while on carbon molecular sieve,it is CO_(2)-N_(2)>CH_(4).It is shown that relative molecular mass and adsorption heat are the primary effect on kinetics for activated carbon,while kinetic diameter is the main resistance factor for carbon molecular sieve.Moreover,the adsorption selectivity of CH_(4)/N_(2) and CO_(2)/N_(2) were estimated with the ideal adsorption solution theory,and carbon molecular sieve performed best at 318.15 K for both CO_(2) and CH_(4) separation.The study suggested that activated carbon is a better choice for separating flue gas and carbon molecular sieve can be a strong candidate for separating coal bed methane.

颗粒状碳酸氧镧去除水体中氟的性能

针对传统吸附剂对氟吸附能力不高的问题,采用氧化镧(La_(2)O_(3))活化制备颗粒状碳酸氧镧(La_(2)O_(2)CO_(3))材料。La_(2)O_(2)CO_(3)对氟离子具有很强的吸附性能,在一个较宽的pH值区间(3.0~10.0)内,具有较好的除氟性能,氟离子去除率在94.5%~98.0%。吸附结果表明,La_(2)O_(2)CO_(3)对氟离子的吸附行为遵循Langmuir模型,是吸热过程。25℃时,其饱和吸附容量达到了22.47 mg/g,相较于传统La_(2)O_(3)材料吸附容量提升约5倍。吸附动力学遵循准二级动力学模型,主要为化学吸附。通过NaOH水溶液对La_(2)O_(2)CO_(3)实现了再生,当NaOH浓度为1.0 mol/L时,脱附率可以达到90.3%,实现了吸附剂的重复利用。

活性生物炭材料对水中Cr(Ⅵ)的吸附特性

以棉花秸秆和玉米秸秆为原料、水蒸气为活化剂,制备不同的活性生物炭材料,探讨不同的活化时间对生物炭材料吸附性能的影响。利用氮气吸附-脱附全自动比表面积和孔隙度分析仪(BET)、扫描电镜(SEM)对活性生物炭材料的孔道和表面结构进行了分析和表征。结果表明:当炭化温度500℃、炭化时间1 h,每克炭化料的水蒸气流量0.04 g·min^(-1)、活化温度800℃、棉花秸秆活化时间30 min、玉米秸秆活化时间45 min,制备的活性生物炭材料吸附性能较好。将最优条件下制得的活性生物炭材料应用于含铬水溶液的处理,研究结果表明,随着溶液Cr(Ⅵ)离子浓度的提高,吸附时间越长,吸附效果越好。

MIL-53(Fe)在土壤Sb(Ⅲ)污染修复中的应用研究

采用溶剂热法制备了金属有机框架材料MIL-53(Fe),并将其应用于吸附土壤中的锑(Sb)。以MIL-53(Fe)为吸附剂,吸附水溶液中Sb(Ⅲ),探讨了溶液温度、pH值、吸附剂用量、Sb(Ⅲ)初始浓度、腐殖酸含量对吸附性能的影响,分析了吸附等温线和吸附动力学。结果表明,吸附剂用量3%,修复15 d后的土壤毒性浸出试验可浸出的Sb(Ⅲ)浓度降低了94.2%。溶液pH值和腐殖酸含量对吸附性能基本没有影响。对于25 mL浓度10μg/mL的Sb(Ⅲ)溶液,加入20 mg MIL-53(Fe)即可达到良好的吸附效果。Sb(Ⅲ)初始浓度对MIL-53(Fe)吸附Sb(Ⅲ)的影响较大,吸附平衡条件下吸附剂最大吸附容量为102.9 mg/g。该吸附过程的吸附等温线与Freundlich模型拟合相匹配,吸附动力学符合伪二级动力学模型。