碳纳米管吸附水溶液中双酚A的热力学

双酚A;固相吸附;HPLC;碳纳米管;热力学     

亚胺基二乙酸树脂对镧(Ⅲ)的吸附及其机制

研究了亚胺基二乙酸树脂(DAAR)对镧离子的吸附行为及机制,pH=5.73的HAc NaAc体系为最佳吸附条件。静态饱和吸附容量为188mg·g-1·R;表观吸附速率常数k298=2.00×10-5s-1,表观吸附活化能Ea=9.57kJ·mol-1;等温吸附服从Freundlich经验式;吸附热力学函数ΔH=10.2kJ·mol-1;ΔS=45.0J·mol-1·K-1;ΔG298=-3.17kJ·mol-1;用0.5mol·L-1HCl作解吸剂,解吸率接近100%;树脂功能基与镧离子的配位摩尔比为3∶1;化学分析及红外光谱表明树脂功能基上的O与La3+发生配位键合。     

二甲基胺取代-烃基膦酸树脂对钆(Ⅲ)的吸附性能

用二甲基胺取代 烃基膦酸树脂对钆的吸附行为进行研究,试验结果表明,在pH4.90时,树脂对钆的静态饱和吸附容量为219mg·g-1(树脂);用2mol·L-1HCl可以定量洗脱;表观吸附速率常数k298=1.81×10-4s-1,测得吸附热力学参数分别为:ΔH=77.46kJ·mol-1,ΔG=-32.417kJ·mol-1,ΔS=368.69J·mol-1·K-1;等温吸附服从Frenndlich曲线;树脂功能基与Gd(Ⅲ)的配位比为2∶1;并用红外光谱探讨了树脂与钆的成键情况。     

邻-氨基酚修饰吸附树脂对2-氨基吡啶的静态吸附热力学及动力学特征

合成了两种邻-氨基酚修饰超高交联吸附树脂(MOAR-1、MOAR-2),并用该树脂对水溶液中2-氨基吡啶的静态吸附热力学和动力学特征进行研究。热力学研究结果表明,Freundlich吸附等温方程能够对静态吸附等温线进行很好地拟合。吸附焓变ΔH<0,其绝对值小于60kJ/mol,表明以物理吸附为主以及该吸附剂容易脱附的特征;ΔG<0,说明吸附是自发行为;ΔS<0,表明吸附质分子在树脂表面上的运动受到了限制。两种树脂对2-氨基吡啶的吸附量随着温度的升高而降低,适当降低温度有利于吸附。动力学研究的结果表明:吸附符合一级动力学方程,吸附速率随温度升高而增大。表观活化能Ea<4.0kJ/mol,说明吸附较容易进行。     

三类引发剂引发苯乙烯聚合特性的比较研究和理论分析

用膨胀计法分别测定了氮 氮键引发剂偶氮二异丁腈 (AIBN)、氧 氧键引发剂过氧化二苯甲酰 (BPO)、碳 碳键引发剂 2 ,3 二氰基 2 ,3 二苯基丁二酸二乙酯的内消旋体 (I)和外消旋体 (II)在苯乙烯中的分解动力学参数 ,分解活化能分别为 :Ed(AIBN) =1 40 0 6kJ·mol-1,Ed(BPO) =1 2 0 3 3kJ·mol-1,Ed(I) =1 0 4 5 2kJ·mol-1,Ed(II) =89 5 6kJ·mol-1;分解活化熵分别为 :ΔS≠(AIBN) =76 3 2J·mol-1·K-1,ΔS≠(BPO) =1 2 76J·mol-1·K-1,ΔS≠(I) =-3 5 2 3J·mol-1·K-1,ΔS≠(II) =-80 84J·mol-1·K-1,并且II的极限转化率α∞ 表现出随温度升高而升高 ,I的α∞ 随温度升高先减小而后趋于平稳的趋势 ,这与AIBN和BPO引发苯乙烯聚合的极限转化率α∞ 随温度的升高而降低的规律有明显不同。对此用动力学链长综合常数k对T的微分结果并结合过渡态理论进行了分析。     

苯酚及取代酚在碳纳米管上的吸附研究

本文研究了水溶液中碳纳米管(CNTs)吸附苯酚、对甲酚和对甲氧基苯酚的热力学特性,测定了不同温度下的吸附等温线,并探讨了其可能的吸附机理。结果表明:在稀溶液中碳纳米管对三种酚类物质的吸附均符合Freund lich和Langmu ir方程,吸附均为放热、熵增的自发过程,并且都具有物理吸附特征;碳纳米管与三种酚类物质分子之间的л—л共轭作用的强弱决定了碳纳米管对三种酚类物质的吸附能力,顺序依次为:对甲氧基苯酚>对甲酚>苯酚。     

磁性多壁碳纳米管吸附水中双氯芬酸的热力学与动力学

研究了磁化多壁碳纳米管(MWCNTs)对于水中非甾体抗炎药双氯芬酸的吸附过程.结果表明,双氯芬酸的吸附量随磁性MWCNTs投加量的增加而增大,而且吸附剂量增加到一定阶段后,双氯芬酸的吸附量达到平衡.在磁性MWCNTs的量为0.7g·L-1时,水溶液中双氯芬酸被磁性MWCNTs吸附的量达到最大,为33.37mg·g-1,对应的双氯芬酸去除率为98.1%.双氯芬酸的去除率随溶液pH的增加先增大后下降,随温度的升高而下降.用准一级、准二级模型进行了动力学分析.回归结果表明,准二级模型更准确地反映了吸附动力学.通过实验确定了Langmuir和Freundlich等温线的线性相关系数与标准偏差,结果揭示出Langmuir等温线与实验数据有很好的拟合度.对热力学参数的计算表明,ΔG00,意味着磁性MWCNTs对双氯芬酸的吸附是自发的;ΔH00,指明吸附是一个放热的物理吸附过程,温度低对吸附有利;ΔS00,代表该吸附是熵增过程.     

羧基化多壁碳纳米管固相萃取-液相色谱-串联质谱法测定环境水体中四溴双酚A和双酚A

建立了羧基化碳纳米管固相萃取-液相色谱-串联质谱联用检测环境水体中四溴双酚A和双酚A的方法。比较了多壁碳纳米管、C60和羧基化多壁碳纳米管作为固相吸附剂对水体中四溴双酚A和双酚A的吸附效率。固相萃取浓缩后的样品经Thermo Scientific Hypersil C18色谱柱（150 mm×4.6 mm,3 μm）分离,采用串联质谱负离子模式进行检测。结果表明,四溴双酚A和双酚A在0.02~1.0 mg/L范围内具有良好的线性关系（r²≥0.99）,空白样品中的检出限（S/N=3）分别为0.04 μg/L和0.2 μg/L。将所建立的方法应用于实际环境水体中四溴双酚A和双酚A的检测,添加回收率在82%~99%之间,精密度小于5.0%,该方法可用于复杂环境样品中痕量四溴双酚A和双酚A的检测。     

磁性镍基氮掺杂多壁碳纳米管对双酚A的吸附性能及机理研究

通过简单的高温煅烧法制备了具有较大比表面积的磁性镍基氮掺杂多壁碳纳米管材料(Ni-NMCNTs),将该材料用于双酚A(BPA)的吸附研究,对材料吸附前后的形貌和结构变化进行表征,探究其吸附机理。结果表明:具有中空管状结构的磁性Ni-NMCNTs对BPA具有良好的吸附能力和重复利用性,材料中吡啶氮的存在提供了吸附缺陷位且增强了π-π共轭作用,为提高吸附性能奠定了基础。实验发现酸性条件下更有利于Ni-NMCNTs对BPA的吸附,在室温25℃,投加量20 mg,pH 6.0条件下,最大吸附容量可达83.64 mg/g,15 min内BPA的吸附率可达86.8%。吸附过程符合准二级动力学方程和Freundlich吸附等温线模型,热力学参数表明整个过程自发进行。     

疏水/亲水性大孔聚二乙烯基苯/聚丙烯酰乙二胺互贯网络的合成及对水溶液中双酚A的吸附研究

采用分步悬浮聚合法制备了由大孔聚二乙烯基苯和聚丙烯酸甲酯组成的聚合物互贯网络(Interpenetrating polymer networks IPN),经过乙二胺氨解,得到由疏水性的大孔聚二乙烯基苯和亲水性的聚丙烯酰乙二胺组成的聚合物互贯网络(polydivinylbenzene/polyacrylethylenediamine IPN即PDVB/PAEM IPN),测定了合成的IPN的物理和化学结构,研究了PDVB/PAEM IPN对pH 6.5的水溶液中双酚A (Bisphenol A即BPA)的吸附性能.结果表明,合成的PDVB/PAEM IPN是含有氨基和酰胺基的多孔性IPN;树脂对水溶液申双酚A的等量吸附焓在20kJ/mol～50kJ/mol之间;动态吸附及脱附实验表明,湿态PDVB/PAEM IPN树脂对水溶液中双酚A的饱和吸附量达到约30mg/mL.树脂可以通过乙醇再生.     

水溶液中六价铬在碳纳米管上的吸附

针对用碳纳米管对水溶液中六价铬的吸附净化进行了研究, 考察了溶液浓度、溶液pH值、共存的三价铬离子等因素对吸附行为的影响. 实验结果表明, 碳纳米管在室温下对于六价铬的吸附量随着平衡浓度的增大而升高, 在铬浓度为493.557 mg•L−1时碳纳米管吸附量达到最大值为532.215 mg•g−1; 六价铬的浓度在300~700 mg•L−1的范围内, 碳纳米管对铬的吸附量变化不大；大于700 mg•L−1时, 随着铬的平衡浓度的升高碳纳米管对铬的吸附量降低, 铬浓度为961.074 mg•L−1时, 碳纳米管吸附量降至194.631 mg•g−1. 在pH值为2~7的范围内, 碳纳米管对六价铬的吸附量随着溶液pH值的减小而增大; 而在碱性条件下, pH值对碳纳米管吸附六价铬的影响不大. 溶液中存在三价铬时, 碳纳米管对六价铬的吸附量明显降低, 表明三价铬与六价铬有竞争吸附. 此外, 活性炭的对比吸附实验表明, 在低浓度时, 譬如在六价铬浓度为190 mg•L−1吸附时, 碳纳米管对铬的吸附量约为活性炭的6倍；而在高浓度下, 譬如六价铬浓度为493 mg•L−1时, 碳纳米管对铬的吸附量约为活性炭的2倍.     

Water-insoluble cyclodextrin polymer crosslinked with citric acid for paraquat removal from water

The anionic water-insoluble cyclodextrin polymer (polyCTR-β-CD) was crosslinked between β-cyclodextrin (β-CD) and citric acid (CTR) at 180?°C during 30?minutes to eliminate paraquat (PQ) from water. The reaction yield was equal to 70.2%, the ionic exchange capacity corresponded to 3.29?mmol·g^?1 and the β-CD content was 0.29?mmol·g^?1. Then, samples were characterized by SEM, ATR-FTIR, TGA, BET and stereoscopic microscope. Adsorption experiments were investigated with different factors such as pH of the solution, contact time, initial concentration of paraquat and adsorption temperature. The relevant pH was equal to 6.5 and the optimal contact time was 120?minutes to attain adsorption equilibrium. At 30?°C, the adsorption capacity was increased (9.4, 17.4 and 20.8?mg·g^?1) when the initial concentration of paraquat was raised (25, 50 and 200?mg·L^?1 respectively). Adsorption kinetics was appropriated to the pseudo-second-order model and adsorption isotherm was fitted to the Langmuir model. For thermochemistry parameters at different temperatures, the negative ΔG° showed a spontaneous adsorption process, the negative ΔH° indicated an exothermic process and the positive ΔS° exhibited an increase disorder. Finally, the reusability of the insoluble polymer was reached 78.3% after four regeneration cycles in methanol.     

聚碳酸酯在亚临界水中解聚的研究

采用间歇式高压反应装置研究聚碳酸酯(PC)在亚临界水中的解聚.在温度260～340℃、压力4.8～14.8 MPa、反应时间5～60min的反应条件下,考察了反应温度及反应时间对PC解聚率及主产物双酚A(BPA)和苯酚(PhOH)回收率的影响.产物分别采用傅里叶红外光谱(FTIR)、扫描电子显微镜(SEM)、气质联谱(...     

Biosorption behaviors of uranium (VI) from aqueous solution by sunflower straw and insights of binding mechanism

Uranium (VI)-containing water has been recognized as a potential longer-term radiological health hazard. In this work, the sorptive potential of sunflower straw for U (VI) from aqueous solution was investigated in detail, including the effect of initial solution pH, adsorbent dosage, temperature, contact time and initial U (VI) concentration. A dose of 2.0 g L^?1 of sunflower straw in an initial U (VI) concentration of 20 mg L^?1 with an initial pH of 5.0 and a contact time of 10 h resulted in the maximum U (VI) uptake (about 6.96 mg g^?1) at 298 K. The isotherm adsorption data was modeled best by the nonlinear Langmuir–Freundlich equation. The equilibrium sorption capacity of sunflower straw was observed to be approximately seven times higher than that of coconut-shell activated carbon as 251.52 and 32.37 mg g^?1 under optimal conditions, respectively. The positive enthalpy and negative free energy suggested the endothermic and spontaneous nature of sorption, respectively. The kinetic data conformed successfully to the pseudo-second-order equation. Furthermore, energy dispersive X-ray, fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy demonstrated that U (VI) adsorption onto sunflower straw was predominantly controlled by ion exchange as well as complexation mechanism. The study revealed that sunflower straw could be exploited for uranium remediation of aqueous streams as a promising adsorbent.     

活性氧化铝及其再生氧化铝对水中氟离子的吸附

Fluoride contamination of water is a problem worldwide and has caused great concern. Our study focused on the removal of fluorides from aqueous solutions using newly prepared and regenerated activated alumina. To obtain a suitable adsorbent, industrial boehmite was calcined from 573 K to 1473 K and the sample was characterized. The X-ray diffraction patterns showed that the sample was transformed to γ-alumina (activated alumina) at temperatures from 773 K to 1173 K, and the BET dates showed that the specific surface area of the sample decreased gradually from the temperature of 773 K to 1173 K. In our study, the activated alumina calcined from 773 K to 973 K was selected as the defluoridation adsorbent, and dynamic adsorption was employed for the removal of fluorides from aqueous solutions. The breakthrough curves demonstrated that the adsorption capacity of the adsorbent decreased with increasing calcination temperature. To investigate the effect of initial fluoride concentration on the adsorption capacity, 15 mg·L^-1, 20 mg·L^-1, and 25 mg·L^-1 fluoride solutions were selected as the initial aqueous fluoride solution. As a result, the capacity of the adsorbent increased gradually with the increase in the initial fluoride concentration. In order to improve the capacity, we also studied the regeneration process in our experiment. When the activated alumina was saturated by the fluorides, it was regenerated with a NaOH solution (pH = 13.0, 13.3, 13.5) and activated with a HCl solution (0.1 mol·L^-1). By a comparison of the five desorption and Al³⁺ dissolution rates during the regeneration process, it was determined that the NaOH solution with pH 13.0 was the most suitable desorption agent. An analysis of the nitrogen adsorption-desorption isotherm showed that its sharpness was almost unchanged after regeneration, which indicated that the pore structure of the adsorbent was not destroyed during this process. The change in the specific surface area and isoelectric point for the five-times regenerated adsorbent were important impact factors for fluoride adsorption. The specific surface area of the regenerated adsorbent increased, and the study of the zeta potential demonstrated that the isoelectric point also increased after regeneration. To observe the adsorption effect of regenerated activated alumina, we performed an adsorption experiment after each regeneration. The breakthrough curves demonstrated that the regenerated activated alumina exhibited faster saturation and increased adsorption capacity compared to fresh activated alumina. To elucidate the adsorption mechanism, IR spectroscopy was employed to characterize the O―H band of the adsorbent. The change in the Al―O―H content of the activated alumina during regeneration was the main factor impacting the fluoride adsorption capacity of the activated alumina.     

氧化石墨烯对水中内分泌干扰物双酚A的吸附性能

以氧化石墨烯(GO)为吸附剂, 内分泌干扰物双酚A (BPA)为目标污染物, 考察了GO对水中BPA的吸附性能. 结果表明: GO对BPA的最大吸附量(q_m)约为87.80 mg·g^-1 (25℃), 30 min左右即可达到吸附平衡, 远快于活性碳; 吸附动力学和等温线数据分别符合准二级动力学模型和Langmuir 吸附模型; 在溶液接近中性和低温的条件下有利于吸附的进行, 在溶液中存在电解质的条件下不利于吸附的进行. GO具有优异的循环吸附性能, 经过多次循环使用后依然可以保持良好的吸附能力. GO对BPA的吸附机理主要是由于GO本身的片状结构以及表面的含氧极性基团, 会与BPA之间产生π-π色散作用和氢键作用. 虽然GO对BPA的吸附能力不如石墨烯, 但是相比于石墨烯, GO表面含有大量极性基团, 具有良好的亲水性, 且GO合成方法相对简单, 可批量生产用于工业污水处理. 因此, 在水处理领域, GO有能力成为新型高效的吸附剂.     

Synthesis, characterization, thermodynamic and kinetic investigations on uranium (VI) adsorption using organic-inorganic composites: Zirconyl-molybdopyrophosphate-tributyl phosphate

Zirconyl-molybdopyrophosphate-tributyl phosphate (ZMPP-TBP) was a novel organic-inorganic composite adsorbent prepared by co-precipitation method and used in the adsorption of uranium from aqueous solution in batch adsorption experiments. The as-obtained product was characterized using SEM, energy dispersive X-ray spectroscopy (EDX), XRD and BET-N₂ adsorption measurements. The study had been conducted to investigate the effects of solution pH, temperature, contact time, initial concentration and coexisting ions. A maximum removal of 99.31% was observed for an initial concentration 5 mg/L, at pH 6.0 and an adsorbent dose of 1.0 g/L. The isothermal data were fitted with both Langmuir and Freundlich equations, but the data fitted the former better than the latter. According to the evaluation using the Langmuir equation, the maximum adsorption capacity of uranium (VI) was 196.08 mg/g at 293 K and pH 6.0. The pseudo-first-order kinetic model and pseudo-second-order kinetic model were used to describe the kinetic data, and the pseudo-second-order kinetic model was better. The thermodynamic parameter ΔG was calculated, the negative ΔG values of uranium (VI) at different temperature showed that the adsorption process was spontaneous. The good reusability of ZMPP-TBP also indicated that the ZMPP-TBP was a very promising adsorbent for uranium adsorption from aqueous solution.     

Removal of uranium(VI) from aqueous solutions using nanoporous ZnO prepared with microwave-assisted combustion synthesis

The adsorption of the uranyl ions from aqueous solutions on the nanoporous ZnO powders has been investigated under different experimental conditions. The adsorption of uranyl on nanoporous ZnO powders were examined as a function of the contact times, pH of the solution, concentration of uranium(VI) and temperature. The ability of this material to remove U(VI) from aqueous solution was followed by a series of Langmuir and Freunlinch adsorption isotherms. The adsorption percent and distribution coefficient for nanoporous ZnO powders were 98.65 % ± 1.05 and 7,304 mL g^?1, respectively. The optimum conditions were found as at pH 5.0, contact time 1 h, at 1/5 Zn²⁺/urea ratio, 50 ppm U(VI) concentration and 303 K. The monomolecular adsorption capacity of nanoporous ZnO powders for U(VI) was found to be 1,111 mg g^?1 at 303 K. Using the thermodynamic equilibrium constants obtained at different temperatures, various thermodynamic parameters, such as ΔG°, ΔH° and ΔS°, have been calculated. Thermodynamic parameters (ΔH° = 28.1 kJ mol ^?1, ΔS° = 160.30 J mol^?1 K^?1, ΔG° = ?48.54 kJ mol^?1) showed the endothermic and spontaneous of the process. The results suggested that nanoporous ZnO powders was suitable as sorbent material for recovery and adsorption of U(VI) ions from aqueous solutions.     

Polyvinyl alcohol fibers with functional phosphonic acid group: synthesis and adsorption of uranyl (VI) ions in aqueous solutions

PVA functionalized with vinylphosphonic acid was prepared as a new adsorbent for uranyl (VI) adsorption from aqueous solutions. The vinylphosphonic acid was cografted onto PVA fibers by preirradiation grafting technique. The adsorbent were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The adsorbent was observed to possess a fibrous structure and was bonded with phosphonic acid groups successfully. The adsorbent was used for the adsorption of low levels uranyl (VI) ions from aqueous solutions. The influence of analytical parameters including pH, adsorption time, amount of adsorbent, metal ion concentration, and temperature were investigated on the recovery of uranyl (VI) ion in aqueous solution. The maximum adsorption capacity (32.1 mg g^?1) and fast equilibrium time (30 min) were achieved at pH of 4.5 at room temperature. Thermodynamic parameters (ΔH° = 2.695 kJ mol^?1; ΔS° = 31.15 J mol^?1 K^?1; ΔG° = ?6.748 kJ mol^?1) show the adsorption of an exothermic process and spontaneous nature, respectively. The possible coordination mechanism was illustrated. Adsorption and desorption coexist in aqueous solutions and then the system becomes equilibrium.     

Highly selective stir bar coated with dummy molecularly imprinted polymers for trace analysis of bisphenol A in milk

A water compatible molecularly imprinted polymers (MIPs) coated stir bar for bisphenol A(BPA) was prepared with 3,3',5,5'-tetrabromobisphenol A as the dummy template molecule in this study. The dummy molecularly imprinted polymers coated stir bar (DMIPs-SB) showed better selectivity than the bars coated with polydimethylsiloxane or non-imprinted polymers when used to extract BPA and its three analogues. The saturated adsorption amount of the DMIPs coating was 3.0 times over that of the non-imprinted polymers coating. To achieve the optimum extraction performance, several parameters, including extraction and desorption time, pH value, adsorption temperature and stirring speed were investigated. The high-performance liquid chromatography combined with the DMIPs-SB was employed in the analysis of BPA in aqueous solution. The linear range of BPA concentration in aqueous medium was 0.0228-2.28 ng/mL with correlation coefficient of 0.9994 and the detection limit was about 6.84 × 10(-3) ng/mL based on three times ratio of signal to noise. This method was directly applied to the determination of trace BPA in milk with satisfactory results.