Fabrication and Thermal Dissipation Properties of Carbon Nanofibers Derived from Electrospun Poly(Amic Acid) Carboxylate Salt Nanofibers

Polyimides (PIs) possess excellent mechanical properties, thermal stability, and chemical resistance and can be converted to carbon materials by thermal carbonization. The preparation of carbon nanomaterials by carbonizing PI‐based nanomaterials, however, has been less studied. In this work, the fabrication of PI nanofibers is investigated using electrospinning and their transformation to carbon nanofibers. Poly(amic acid) carboxylate salts (PAASs) solutions are first electrospun to form PAAS nanofibers. After the imidization and carbonization processes, PI and carbon nanofibers can then be obtained, respectively. The Raman spectra reveal that the carbon nanofibers are partially graphitized by the carbonization process. The diameters of the PI nanofibers are observed to be smaller than those of the PAAS nanofibers because of the formation of the more densely packed structures after the imidization processes; the diameters of the carbon nanofibers remain similar to those of the PI nanofibers after the carbonization process. The thermal dissipation behaviors of the PI and carbon nanofibers are also examined. The infrared images indicate that the transfer rates of thermal energy for the carbon nanofibers are higher than those for the PI nanofibers, due to the better thermal conductivity of carbon caused by the covalent sp² bonding between carbon atoms.     

Removal of Chromium (VI) from Aqueous Solution by Cellulose Modified with D-Glucose

Cellulose powder was grafted with the vinyl monomer glycidyl methacrylate using ceric ammonium nitrate as initiator and was further derived with D-Glucose (D-Glu) to build a adsorbent (Cell-g-GMA-D-Glu). Epoxy cellulose, which was made up of Cell-g-GMA and Cell-hydro-g-GMA, was found to contain 5.48 mmol g^?1 epoxy groups. The adsorption process of the adsorbent was described by the Langmuir model of adsorption well and the maximum adsorption capacity of chromium (VI) reached to 54.59 mg g^?1. The adsorption-desorption tests of the Cell-g-GMA-D-Glu exhibited that the reproducibility of the absorbent was well and the adsorbent could be reused six times at least.     

聚季铵盐强化超滤处理铬(VI)

以聚季铵盐-22(PQ22)为络合剂,研究Cr(VI)的强化超滤行为,考察聚电解质/金属质量比、pH值及外加盐对PQ22-Cr(VI)络合体系截留系数和膜通量的影响,并研究了络合体系的浓缩、解络合和洗涤过程. 结果表明,当聚电解质/金属质量比为80及pH=9时,Cr(VI)截留系数大于0.9;外加Cl-, NO3-和SO42-使Cr(VI)截留系数降低,且SO42-比NO3-和Cl-的影响更大;控制聚电解质/金属质量比为80及pH=9,当浓缩因子为20时,Cr(VI)浓度从初始的5 mg/L浓缩至82.6 mg/L;对浓缩液解络合,控制Cl-浓度为0.15 mol/L,解络合率为71.1%,以Cl-溶液对解络合液进行洗涤,Cr(VI)洗脱率可达95.9%. 聚季铵盐-22可循环使用.     

Removal of Cr(VI) From Aqueous Solution by Turkish Vermiculite: Equilibrium,Thermodynamic and Kinetic Studies

Abstract

The adsorption of Cr(VI) from aqueous solution by Turkish vermiculite were investigated in terms of equilibrium, kinetics, and thermodynamics. Experimental parameters affecting the removal process such as pH of solution, adsorbent dosage, contact time, and temperature were studied. Equilibrium adsorption data were evaluated by Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherm models. Langmuir model fitted the equilibrium data better than the Freundlich model. The monolayer adsorption capacity of Turkish vermiculite for Cr(VI) was found to be 87.7 mg/g at pH 1.5, 10 g/L adsorbent dosage and 20°C. The mean free energy of adsorption (5.9 kJ/mol) obtained from the D–R isotherm indicated that the type of sorption was essentially physical. The calculated thermodynamic parameters (ΔG ^o , ΔH ^o and ΔS ^o ) showed that the removal of Cr(VI) ions from aqueous solution by the vermiculite was feasible, spontaneous and exothermic at 20–50°C. Equilibrium data were also tested using the adsorption kinetic models and the results showed that the adsorption processes of Cr(VI) onto Turkish vermiculite followed well pseudo-second order kinetics.     

吸附分离水体中铀的吸附材料研究新进展

铀是最危险的放射性金属之一,广泛存在于核燃料的制备、乏燃料后处理和矿石开采等生产活动所产生的含铀废水中,严重威胁水生生态系统与人类健康。吸附法处理水中的U(Ⅵ)具有便捷高效、经济和选择性好的优势。综述了近3年对水中铀吸附材料的研究新进展,介绍了无机、有机、有机无机复合和生物衍生类吸附材料的制备,结构特点,吸附性能,并对铀吸附材料的研究方向进行了展望。     

Extraction of Uranium(VI) and Plutonium(IV) with Tetra-Alkylcarbamides

ABSTRACT

The use of tetra-alkylcarbamides as novel extractants for the separation of uranium(VI) and plutonium(IV) by solvent extraction from spent nuclear fuels is investigated in this study. Batch extraction experiments show that tetra-alkylcarbamides strongly extract U(VI) with high distribution ratios. Plutonium(IV) can be co-extracted with U(VI) at high nitric acid concentration, while high U(VI)/Pu(IV) selectivities can be reached at lower acidity. Loading capacity experiments with high uranium concentrations show that alkyl chains longer than butyl are necessary to avoid third phase formation. Nevertheless, the viscosity of uranium-loaded solvents gets too high with alkyl chains longer than pentyl. Overall, this study shows that with TPU extractant (with four pentyl chains), an efficient co-extraction of uranium and plutonium can be reached (D_U,Pu > 1) for a concentration of nitric acid higher than 4 mol?L^?1, while the partition between uranium(VI) and plutonium(IV) could be operated even at 2 mol?L^?1 nitric acid without redox chemistry.     

磷酸三丁酯和异丁基十二烷基亚砜萃取铀(VI)的研究

研究了以甲苯作稀释剂时 ,磷酸三丁酯 (TBP)和异丁基十二烷基亚砜 (BDSO)萃取铀 (VI)的机理。考察了硝酸浓度、温度对分配比的影响 ,求得萃取反应的热力学函数。考察了萃取剂浓度对协萃系数的影响 ,发现TBP和BDSO具有协萃效应 ,最大协萃系数在TBP :BDSO =1:1处     

Removal of Cr (VI) from aqueous solution by newspapers

The potential to remove Cr (VI) ions from aqueous solution using newspapers was investigated in the present study. The effects of relevant parameters such as solution pH, adsorbent concentration, and reaction temperature on Cr (VI) adsorption were examined. The adsorption of Cr (VI) ions onto newspapers was found to be highly pH-dependent and the highest uptake occurred at pH 1.0. The sorption equilibrium data were correlated to the Langmuir, Freundlich, Redlich-Peterson and Dubinin-Radushkevich equations. Five different non-linear error functions were examined and the result indicated that the Freundlich and Redlich-Peterson equations better fitted the equilibrium data than Langmuir isotherm. The maximum sorption capacity was found to be 55.06 mg/g at pH 1.0, adsorbent concentration 4 g/L and reaction temperature of 30 °C. Different thermodynamic parameters viz., changes in standard free energy (ΔG⁰), enthalpy (ΔH⁰) and entropy (ΔS⁰) were also evaluated and the results show that the sorption process was spontaneous and endothermic in nature. The kinetic experimental data were well fitted by the pseudo-second order, external film diffusion and diffusion models allowing the corresponding parameters to be evaluated. The sorption capacity increased with the decrease of adsorbent concentration.     

Extraction Properties of P(O)-Modified N-Aryl-Carbamoylmethylphosphine Oxides in Nitric Acid Media

Novel polyfunctional neutral organophosphorus compounds, P(O)-modified N-aryl- carbamoylmethylphosphine oxides, Ph₂P(O)CH₂C(O)NH-(o-C₆H₄)(CH₂)_n-P(O)Ph₂ and Ph₂P(O)CH₂C(O)NH-(m-C₆H₄)(CH₂)_n-P(O)Ph₂ (n = 1,2), were synthesized and studied as extractants for U(VI), Th(IV) and Ln(III) from HNO₃ solutions. The influence of aqueous and organic phases on the extraction efficiency was elucidated and stoichiometry of the complexes extracted was determined. Introduction of an additional phosphoryl group into the phenyl substitutent at the nitrogen atom of diphenyl(N-phenylcarbamoylmethyl)phosphine oxide resulted in an increase of the efficiency of U(VI), Th(IV), Ln(III), and Re(VII) extraction.     

钢渣颗粒对水中Cr(VI)的吸附与还原作用

以钢渣颗粒为水处理剂,分析了其组成和结构,研究了钢渣颗粒直接吸附去除水中Cr(VI)的工艺过程及机理. 结果表明,钢渣颗粒在适当的粒度与用量下,经10 min搅拌处理,水中Cr(VI)浓度由200 mg/L降低到0.5 mg/L,达到《污水综合排放标准》(GB8978-1996)的要求. 钢渣颗粒对水中Cr(VI)的吸附符合Langmuir等温吸附过程,对Cr(VI)的饱和吸附量达6.878 mg/g. 化学分析和XPS分析均表明,钢渣颗粒对水中Cr(VI)具有吸附与还原的联合作用,吸附后钢渣颗粒中Cr(III)含量由0.0985%提高到0.39%,而FeO含量由9.20%下降到8.35%. 吸附后钢渣颗粒表面形成了Cr(OH)3,说明钢渣颗粒中FeO充当了还原剂,将水中Cr(VI)吸附于钢渣颗粒表面并还原成了低毒的Cr(OH)3随钢渣颗粒沉降直接从水中去除.     

Dynamic Melt Rheological Properties of Ionomers Based on Poly(Ethylene-co-Acrylic Acid) and Poly(Ethylene-co-Methacrylic Acid)

The high temperature stability, and the dynamic melt rheological properties of poly(ethylene-co-acrylic acid) (EAA), zinc salt of EAA, and sodium salt of EAA were evaluated in the molten state over broad ranges of shear rates and temperatures using ARES (Rheometrics). The master curves of G′ and G″ as a function of angular frequency (ω) were constructed for each material. The influence of ionic groups on the storage modulus (G′), loss modulus (G″), complex viscosity (η*), and flow activation energy (E_a) were analyzed. The results of EAA based ionomers are discussed with those of the ionomers based on poly(ethylene-co-methacrylic acid) (EMAA). The linear visco-elastic spectra, and flow activation energies of the two series of ionomers show differences.     

Fe2+-modified Vermiculite for the Removal of Chromium (VI) from Aqueous Solution

A novel adsorbent: Fe²⁺-modified vermiculite was prepared in a two-step reaction. Adsorption experiments were carried out as a function of pH, contact time, and concentration of Cr(VI). It was found that Fe²⁺-modified vermiculite was particularly effective for the removal of Cr(VI) at pH 1.0. The adsorption of Cr(VI) reached equilibrium within 60 min, and the pseudo-second-order kinetic model best described the adsorption kinetics. The adsorption data follow the Langmuir model more than the Freundlich model. At pH 1.0, the maximum Cr(VI) sorption capacity (Q _max ) was 87.72 mg · g^?1. Desorption of Cr(VI) from Fe²⁺-modified vermiculite using NaOH treatment exhibited a higher desorption efficiency by more than 80%. The sorption mechanisms including electrostatic interaction and reduction were involved in the Cr (VI) removal. The results showed that Fe²⁺-modified vermiculite can be used as a new adsorbent for Cr(VI) removal which has a higher adsorption capacity and a faster adsorption rate.     

Removal of Cadmium Ions from Aqueous Samples by Synechocystis sp.

Abstract

The biosorption of cadmium ions from aqueous solution by dried, immobilized dried and immobilized live Synechocystis sp. was investigated. Sorption of plain Ca-alginate beads, which were used as substrate for immobilization, was also studied for comparison. Removal efficiency of biosorbents was studied as a function of pH (2-8 Volesky , B. ( 1990 ) Biosorption of Heavy Metals ; CRC Press : Boca Raton , FL . Wase , J. , Forster , C.F. (1997) Biosorbents for Metal Ions ; Taylor & Francis : London. Malkoç , E. ; Nuho?lu , Y. ( 2005 ) Investigations of nickel (II) removal from aqueous solutions using tea factory waste . J. Hazard. Mater. , 127 : 120 – 128 . Lodeiro , P. ; Cordero , B. ; Barriada , J.L. ; Herrero , R. ; Sastre de Vicente , M.E. ( 2005 ) Biosorption of cadmium by biomass of brown marine macroalgae . Bioresource Technol. , 96 : 1796 – 1803 . Shen , J. ; Duvnjak , Z. ( 2005 ) Adsorption isotherms for cupric and cadmium ions on corncob particles . Sep. Sci. Technol. , 40 : 1461 – 1481 . Kat?rc?o?lu , H. ; Asl?m , B. ; Türker , A.R. ; At?c? , T. ; Beyatl? , Y. ( 2008 ) Removal of cadmium(II) ion from aqueous system by dry biomass, immobilized live and heat-dried Oscillatoria sp. H1 isolated from freshwater (Mogan Lake) . Bioresource Technol. , 99 ( 10 ): 4185 – 4191 . Pavasant , P. ; Apiratikul , R. ; Sungkhum , V. ; Suthiparinyanont , P. ; Wattanachira , S. ; Marhaba , T.F. ( 2006 ) Biosorption of Cu²⁺, Cd²⁺, Pb²⁺, and Zn²⁺ using dried marine green macroalga Caulerpa lentillifera. Bioresource Technol. , 97 : 2321 – 2329 . ), temperature (20–40°C), initial cadmium ion concentration (50–300 mg/L), and contact time (0–120 min). The maximum biosorption capacities of the dried, immobilized dried, and immobilized live Synechocystis sp. and plain Ca-alginate beads were found as 75.7, 4.9, 4.3, and 3.9 mg/g, respectively at optimum conditions. Biosorption equilibrium was established in about 15 min. Dried biomass of Synechocystis sp. was found to be more suitable and an efficient biosorbent for the removal of cadmium ion from aqueous solution. Both of the isotherm models (Langmuir and Freundlich) were suitable for describing the biosorption of cadmium by the dried biomass of Synechocystis sp. All the tested cyanobacterial forms could be recovered more than 90% and reused in five biosorption–desorption cycles without any considerable loss in the biosorption capacity.     

Solvent Extraction of Uranium (VI) from Chloride Solutions using Cyphos IL-101

The solvent extraction of uranium (VI) from chloride solutions by Cyphos IL-101 in xylene has been studied. Distribution coefficients were found to increase with aqueous chloride concentration and extractant concentration. The enthalpy of extraction is endothermic with ΔH = +24 ± 2 kJ·mol^?1. Based upon slope analysis, an anion exchange extraction mechanism is proposed, with formation of a UO₂Cl₄ ^2- complex in association with 4 Cyphos IL-101 ligands. The extraction kinetics were fast, with complete equilibration occurring within 30 seconds. An isotherm for uranium extraction from 1.0 mol·L^?1 chloride solution by 0.1 mol·L^?1 Cyphos IL-101 in xylene shows that 45 mmol·L^?1 uranium can be loaded into the organic phase in equilibrium with 2.1 mmol·L^?1 in the aqueous phase. The absorption spectrum of the uranium loaded solvent between 350 and 550 nm is indicative of the UO₂Cl₄ ^2- complex with only chlorides present in the inner coordination sphere, unlike the more strongly hydrogen bonded Alamine 336 extracted uranium complex. Subject to the same experimental conditions, distribution coefficients for Cyphos IL-101 were significantly greater than for Alamine 336 or Aliquat 336.     

哌嗪基单丁酰胺酸钙/锌的合成及对PVC热稳定性研究

以丁二酸酐、哌嗪、氯化钙、氯化锌为原料,通过两步反应制备了哌嗪基单丁酰胺酸钙/锌（PSACa/Zn）热稳定剂。采用元素分析、电感耦合等离子体原子发射光谱仪（ICP?OES）和傅里叶变换红外光谱仪（FTIR）对产品结构进行表征,通过刚果红试纸法、转矩流变仪法、热失重法考察了PSACa/Zn对PVC的热稳定性能,并筛选了PSACa和PSAZn的最佳配比。结果表明,PSACa和PSAZn对PVC的静态热稳定时间分别可达74.5、41.5 min,优于硬脂酸钙（CaSt₂）、硬脂酸锌（ZnSt₂）热稳定剂;PSACa和PSAZn复配使用时,以m_PSACa∶m_PSAZn=1∶1时性能最佳,对PVC静态热稳定时间可达92 min,动态热稳定时间可达905 s;发现PSACa/Zn对PVC的长期热稳定性良好。     

Lead(II) Adsorption from Aqueous Solution by Poly(ethylene terephthalate)-g-Acrylamide Fibers

In this study, a reactive fibrous adsorbent was prepared by graft copolymerization of Acrylamide (AAm) onto poly(ethylene terephthalate) (PET) fibers and the adsorption properties of Pb(II) ion from aqueous solution by the reactive fibers were examined by batch equilibration technique. The effects of graft yield, pH, adsorption time, initial ion concentration and adsorption temperature on the adsorption amount of Pb(II) ion was studied. The results show that the adsorption amounts of Pb(II) ion increased with grafting yield, shaking time, initial ion concentration and adsorption temperature. Adsorption of Pb(II) ion was strongly affected by pH. A Lagergren pseudo-second-order was the model that best described the adsorption mechanism. It was found that the adsorption isotherm of the Pb(II) ion fit Langmuir-type isotherms. From the Langmuir equation the adsorption capacity was found as 39.57 mg/g fiber for Pb(II) ion for the copolymer with a graft yield of 15.7%. Quantitative desorption of Pb(II) from reactive fibers were found to be 96% by 5 M HNO₃. Five adsorption–desorption cycles demonstrated that the reactive fibers were suitable for repeated use without considerable change in adsorption capacity. The results of the thermodynamic study indicated that the adsorption processes was endothermic and spontaneous.     

Liquid-Liquid Extraction of Uranium(VI) from Aqueous Solution using 1-Hydroxyalkylidene-1,1-diphosphonic Acids

The extraction of uranium(VI) from aqueous solutions has been investigated using 1-hydroxyhexadecylidene-1,1-diphosphonic acid (HHDPA) and 1-hydroxydodecylidene-1, 1-diphosphonic acid (HDDPA), which were synthesized and characterized by elemental analysis and by FT-IR, ¹H NMR, ³¹P NMR spectroscopy. In this article, we propose a tentative assignment for the shifts of those two ligands and their specific complexes with uranium(VI). We carried out the extraction of uranium(VI) by HHDPA and HDDPA from [carbon tetrachloride?+?2-octanol (v/v: 90%/10%)] solutions. Various factors such as contact time, pH, organic/aqueous phase ratio, and extractant concentration were considered. The optimum conditions obtained were: contact time?=?20 min, organic/aqueous phase ratio?=?1, pH value?=?3.0, and extractant concentration?=?0.3 M. The extraction yields are more significant in the case of the HHDPA which is equipped with a hydrocarbon chain, longer than that of the HDDPA. Logarithmic plots of the uranium(VI) distribution ratio vs. pH_eq and the extractant concentration showed that the ratio of extractant to extracted uranium(VI) (ligand/metal) is 2:1. The formula of the complex of uranium(VI) with the HHDPA and the DHDPA is UO₂(H₃L)₂ (HHDPA and DHDPA are denoted as H₄L). A spectroscopic analysis showed that coordination of uranium(VI) takes place via oxygen atoms.     

Removal of Cr(VI) from aqueous solution by London plane leaves

The effect of initial metal concentration, contact time and solution temperature on the removal of Cr(VI) from solution by waste London plane leaves, generated by the pruning of street trees, was investigated in batch mode conditions. The removal of Cr(VI) was highly concentration‐dependent and mainly governed by physico‐chemical adsorption under the weak acidic conditions studied. The equilibrium data fit well in the Langmuir isotherm model. The Langmuir constants were calculated at different temperatures and both the adsorption capacity and adsorption intensity increased with rising temperature. The endothermic nature of the Cr(VI) adsorption was confirmed by the thermodynamic parameters. The study has shown that the waste leaves can be used as an effective adsorbent for removal of Cr(VI) from wastewater. Copyright © 2003 Society of Chemical Industry     

Extraction of Gibberellic Acid from Aqueous Solution by Trioctyl Amine (TOA)

Gibberellic acid (GA) extraction from fermentation broth by trioctyl amine (TOA), which is a long chain aliphatic amine was studied. Initial concentration of GA was 0.65 g · L^?1. This was performed using the fungi Gibberella fujikuroi in fermentation. Alcohols (isoamyl alcohol, n-octanol, n-decanol) have been used to dissolve TOA for preparing organic phases. All experiments were studied as batch extraction. Distribution coefficients (K_D), loading factors (Z), and extraction efficiency (E) were calculated. The highest extraction efficiency, distribution coefficient, and loading factor were achived with isoamyl alcohol diluent as value of 80.6, 98.7, and 4.58, respectively. Furthermore, the linear solvation energy relationship (LSER) model including Hansen solubility parameters regressed to experimental results. The LSER model predicts a close resemblance of experimental data.     

Synthesis of Various Calix[4]arene Derivatives with Mercaptoalkyl Chains and Their Application in Removing Cr(VI) from Aqueous Solution

Four different mercaptoalkyl-substituted calixarene derivatives (5,11,17,23-tetra-tert-butyl-25,27-bis(3-mercaptopropoxyl)-26,28-dihydroxycalix[4]arene, 25,27-bis(3-mercaptopropoxyl)-26,28-dihydroxycalix[4]arene, 25,27-bis(5-mercaptopentanoxyl)-26,28-dihydroxycalix[4]arene and 5,17-di-tert-butyl-11,23-di-carboxyl-26,28-bis(3-mercaptopropoxyl)-25,27-di-hydroxycalix[4]arene) were synthesized. Their structures were characterized by Fourier transform infrared spectroscopy (FTIR), ¹H and ¹³C NMR spectroscopy, and elemental analysis techniques. Moreover, their extraction capabilities at different parameters such as pH, shaking speed, and shaking time were examined toward dichromate ions. Results implied that all mercaptoalkyl-substituted calixarene derivatives showed an extraction capability toward dichromate anion while the carboxyl-functionalized calixarene-marcapto-alkyl derivative exhibited the highest extraction capability.