TiO2纳滤膜对重金属离子的截留性能

采用孔径为1.5 nm的TiO2纳滤膜,在压力0.4～0.8 MPa,pH值3～7的条件下,考察了膜对浓度范围为50～500 mg/L的Cu(NO3)2、Ni(NO3)2、ZnC12和CdC12四种单组份重金属溶液的截留性能.结果表明:除Cd2+外,膜对重金属离子的截留率随溶液浓度的增大先增大,当浓度达到200 mg/L后趋于稳定;升高压力膜的离子截留率会略有增加;当pH=6时,膜对Ni2+和Cd2+的截留率最低,而对Cu2+和Zn2+的截留率在pH=5～6时达到最高.TiO2膜对Cu2+、Ni2+、Zn2+和Cd2+的最高截留率分别可以达到96.9％、95.9％、92.5％和83.2％.     

Porous CS monoliths and their adsorption ability for heavy metal ions

Highly porous chitosan (CS) monoliths were prepared by a unidirectional freeze-drying method and the adsorption performance of the monoliths for metal ions in aqueous solution was evaluated. The porous CS monoliths have excellent adsorption for a range of metal ions. The effect of the amount of porous CS monoliths, the pH, the adsorption time, the amount of the cross-linking agent, and the amount of disodium ethylenediamine tetraacetate (EDTA) on the saturated adsorption efficiency (Ade) were determined. The pH had the greatest influence on the adsorption behavior. Under optimal conditions (C(CU2?) = 800 mg/L, pH 6, and cross-linking agent = 0.15%) for the CS monoliths, the Ade for Cu(2+) exceeded 99%, and the saturated adsorption capacity (Q(s)) reached a value of 141.8 mg/g (2.23 mmol/g) in 4h. Moreover, the addition of EDTA can both increase the Q(s) and shorten the time that achieved the level. If EDTA was added, this level was achieved in 2h. The porous CS monoliths can be regenerated by soaking them in acid and their Ade is maintained.     

Evaluation of iron-based hybrid materials for heavy metal ions removal

The article presents in detail the results of the sorption of heavy metal ions such as Cu(II), Zn(II), Cd(II), and Zn(II) in the presence of ethylenediamine-N,N′-disuccinic acid as well as chromium(VI) on Purolite Arsen X^np and Lewatit FO36. Factors affecting the sorption equilibrium (sorbent dose, contact time, temperature, pH, and the presence of interfering ions) were studied. To compare the surface morphologies of the studied ion exchangers, scans using atomic force microscope were also recorded, and attenuated total reflectance infrared spectroscopy was applied to establish the adsorption mechanism. The main parameters affecting sorption are initial concentration of the solution, pH, and phase contact time. Temperature has only a slight influence. The kinetic data were fitted using the pseudo-first-order and pseudo-second-order models. In the case of Cr(VI) adsorption, the equilibriums on Purolite Arsen X^np and Lewatit FO36 were established within 60 min, in the case of Cu(II) and Zn(II) within 30–40 min and for Cd(II) and Pb(II) even less than 30 min. Moreover, it was found that the effectiveness of adsorption in the case of Cr(VI), Cu(II), Zn(II), Cd(II), and Pb(II) on Purolite ArsenX^np was higher than that on Lewatit FO36.     

丝素-壳聚糖共混膜的制备及其金属离子渗透行为的研究

采用壳聚糖(CS)对天然高分子丝素(SB)进行改性,制备了丝素-壳聚糖(SB-CS)共混膜.FTIR、TGA、SEM的分析表明,该共混膜中SB和CS具有良好的相容性,壳聚糖改善了丝素膜的吸水性和机械性能.通过渗透实验发现不同的金属离子在共混膜中的渗透速率有很大的差异,一些常见的金属离子渗透速率的大小顺序为:K+>Ca2+>Cd2+>Pb2+>Cu2+>Ni2+.     

Polyrhodanine modified anodic aluminum oxide membrane for heavy metal ions removal

Polyrhodanine was immobilized onto the inner surface of anodic aluminum oxide (AAO) membrane via vapor deposition polymerization method. The polyrhodanine modified membrane was applied to remove heavy metal ions from aqueous solution because polyrhodanine could be coordinated with specific metal ions. Several parameters such as initial metal concentration, contact time and metal species were evaluated systematically for uptake efficiencies of the fabricated membrane under continuous flow condition. Adsorption isotherms of Hg(II) ion on the AAO-polyrhodanine membrane were analyzed with Langmuir and Freundlich isotherm models. The adsorption rate of Hg(II) ion on the membrane was obeyed by a pseudo-second order equation, indicating the chemical adsorption. The maximum removal capacity of Hg(II) ion onto the fabricated membrane was measured to be 4.2 mmol/g polymer. The AAO-polyrhodanine membrane had also remarkable uptake performance toward Ag(I) and Pb(II) ions. Furthermore, the polyrhodanine modified membrane could be recycled after recovery process. These results demonstrated that the polyrhodanine modified AAO membrane provided potential applications for removing the hazardous heavy metal ions from wastewater.     

SoI--gel modification of pH electrode glass membranes for sensing anions and metal ions

To obtain glass membrane electrodes selective for anions and metal ions, pH electrode glass membranes were modified by a sol-gel method using a quaternary ammonium salt and a bis(crown ether). A chloride ion-sensing glass membrane was designed, in which a pH electrode glass membrane was modified chemically by an alkoxysilyl quaternary ammonium chloride. X-ray photoelectron spectroscopy confirmed the chemical bonding of the quaternary ammonium moiety to the starting glass surface, which afforded the first example of glass-based "anion"-sensing membranes. A neutral carrier-type sodium ion-selective glass membrane was also fabricated which encapsulates a bis(12-crown-4) derivative in its sol-gel-derived surface. Both sol-gel-modified anion and metal ion-selective glass electrodes exhibited high sensitivity to their ion activity changes. The present sol-gel modification paves the way for designing glass-based ion sensors with tailor-made ion selectivities toward anions as well as cations.     

Surface engineered magnetic nanoparticles for removal of toxic metal ions and bacterial pathogens

Surface engineered magnetic nanoparticles (Fe₃O₄) were synthesized by facile soft-chemical approaches. XRD and TEM analyses reveal the formation of single-phase Fe₃O₄ inverse spinel nanostructures. The functionalization of Fe₃O₄ nanoparticles with carboxyl (succinic acid), amine (ethylenediamine) and thiol (2,3-dimercaptosuccinic acid) were evident from FTIR spectra, elemental analysis and zeta-potential measurements. From TEM micrographs, it has been observed that nanoparticles of average sizes about 10 and 6 nm are formed in carboxyl and thiol functionalized Fe₃O₄, respectively. However, each amine functionalized Fe₃O₄ is of size ∼40 nm comprising numerous nanoparticles of average diameter 6 nm. These nanoparticles show superparamagnetic behavior at room temperature with strong field dependent magnetic responsivity. We have explored the efficiency of these nanoparticles for removal of toxic metal ions (Cr³⁺, Co²⁺, Ni²⁺, Cu²⁺, Cd²⁺, Pb²⁺ and As³⁺) and bacterial pathogens (Escherichia coli) from water. Depending upon the surface functionality (COOH, NH₂ or SH), magnetic nanoadsorbents capture metal ions either by forming chelate complexes or ion exchange process or electrostatic interaction. It has been observed that the capture efficiency of bacteria is strongly dependent on the concentration of nanoadsorbents and their inoculation time. Furthermore, these nanoadsorbents can be used as highly efficient separable and reusable materials for removal of toxic metal ions.     

Removal of radionuclides,macrocomponent metal ions,and organic compounds from solutions by nanofiltration

Removal of Mg²⁺, Сa²⁺, Cu²⁺, Ni²⁺, Zn²⁺, Fe³⁺, and Pr³⁺ ions, tracer amounts of ¹³⁷Cs, ⁸⁵Sr, and ⁶⁰Co radionuclides, and oxalate and ethylenediaminetetraacetate ions from solutions using a polymeric nanofiltration (NF) membrane produced by RM Nanotekh (Russia) was studied. The selectivity (S) of the NF membrane to multicharged metal cations is considerably higher than to single-charged cations. The NF membrane exhibits the highest selectivity (S = 94–97%) to triple-charged Fe³⁺ and Pr³⁺ ions and double-charged Cu²⁺ ions. The selectivity to double-charged Mg²⁺ and Zn²⁺ ions is somewhat lower (90–94% on the average). Among doublecharged cations, the NF membrane exhibits the lowest selectivity (80–88%) to Ni²⁺ and Cа²⁺ ions. The NF membrane shows high performance in retention of tracer amounts of Sr (S = 95%) and Co (S > 99%) radionuclides, and also of oxalate (S = 94.5%) and ethylenediaminetetraacetate (S = 97.5%) ions. Examples of using the nanofiltration method for removing ⁶⁰Co from a model solution simulating NPP bottom residue and for removing transition metal impurities from a LiCl solution are presented.     

Sulfonated polyethersulfone-based membranes for metal ion removal via a hybrid process

Membranes are being increasingly used as an economic alternative for wastewater treatment compared to conventional methods. Ultrafiltration membranes are widely used in metal ions’ rejection. Sulfonated Polyethersulfone (SPES)/polysulfone (PSf) blend flat sheet membranes are prepared using polar solvent N-methyl-2-pyrrolidone (NMP) by the dry–wet phase inversion technique. Polyethylene glycol (PEG-200) is used as a non-solvent additive in the casting solution. The effect of PSf/SPES blend ratio on the morphology, hydrophilicity, water content, porosity, hydraulic resistance, pure water flux, compaction, and molecular weight cut-off (MWCO) of the prepared membranes was studied and found to be improved significantly by the incorporation of SPES in the dope solution. Scanning electron microscopy (SEM) studies revealed that the membranes formed had an asymmetric structure with a thin skin layer and porous sublayer. The prepared membranes were used for rejection of Cu(II) and Zn(II) which are complexed with water-soluble chelating polymer polyethyleneimine. The results show that the order of rejection is Cu(II) ion > Zn(II) ion. Thus, it is worth mentioning that the PSf/SPES blend ultrafiltration membranes prepared in this study would offer immense potential in removal of toxic metal ion from industrial effluents.     

支撑液膜技术对金属离子的分离回收

当前国民经济的突飞猛进备受世人瞩目,但在工业生产过程中产生的汞、铬、铜、铅、锌、铀、镍、镉等废液,释放到环境中将会导致水体污染和生态破坏.因此,有毒金属废液的治理迫在眉睫.支撑液膜作为分离领域回收金属离子的一项技术,本文对其构成及分离原理进行了概述,分析了导致支撑液膜不稳定的原因,并基于膜稳定性对衍生出的支撑液膜的类型进行论述.此外,概述了不同类型的支撑液膜技术在金属离子分离回收领域的应用,最后对支撑液膜的工业化应用前景进行了展望.     

纳滤膜分离技术及其研究进展

概述了纳滤膜的特点及影响其分离性能的各种因素,介绍了纳滤膜的分离机理和目前应用开发情况。     

Roles of metal ion complexation and membrane permeability in the metal flux through lipophilic membranes. Labile complexes at permeation liquid membranes

The various physicochemical factors that influence the flux of carrier-transported metal ions through permeation liquid membranes (PLM) are studied systematically. Understanding PLM behavior is important (i) to optimize the application of PLM as metal speciation sensors in environmental media and (ii) because PLM may serve as bioanalogical devices that help to elucidate the environmental physicochemical processes occurring at the surface of biological membranes. Diffusion of free and complexed metal ions in solution, as well as diffusion of the metal carrier complex in the membrane, is considered. The respective roles of diffusion layer thickness, ligand concentration, complex stability, carrier concentration, and membrane thickness are studied experimentally in detail and compared with theory, using various labile complexes, namely, Pb(II)-diglycolate, Cu(II)-diglycolate, and Cu(II)-N-(2-carboxyphenyl)glycine. Conditions where either membrane diffusion or solution diffusion is rate limiting are clearly discriminated. It is shown in particular, that, by tuning the carrier concentration or membrane thickness, either the free metal ion concentration or the total labile metal species are measured. PLM can thus be used to determine whether models based on the free ion activity in solution (such as BLM or FIAM models) are applicable to metal uptake by microorganisms in a real natural medium.     

Preparation of aminated-polyacrylonitrile nanofiber membranes for the adsorption of metal ions: comparison with microfibers

Polyacrylonitrile nanofibers (PAN-nFs) were produced using the electrospinning method. Subsequently, the electrospun fibers were modified by diethylenetriamine to produce aminated polyacrylonitrile (APAN) nanofibers. Finally, the adsorbability of copper ions on the surface of the nanofibers was examined in an aqueous solution. Attenuated total internal reflection (ATIR) analysis confirmed the surface amination of the produced PAN-nFs. The grafting yield was calculated by the gravimetric method. The optimum condition was determined to yield the maximum grafting of amine groups to PAN with no losses in sample flexibility. Atomic absorption spectroscopy (AAS) was used to measure the copper ion concentration in the solution. Results indicate that the adsorption process in nanofibers is three times faster in comparison with microfibers. Moreover, the pH effect was studied based on the adsorption behavior of copper ions on the APAN nanofibers. In addition, thermodynamic parameters were calculated, revealing that the process was endothermic and demonstrating that randomness increased at the solid-solution interface during the process. The obtained enthalpy value indicates that the chelation of copper ions among the aminated polyacrylonitrile can be regarded as a chemical adsorption process. The adsorption data fit well with the Langmuir isotherm. The saturation adsorption capacity obtained from the Langmuir model for Cu(II) ions was 116.522 mg/g which is five times more than the reported value for APAN microfibers [S. Deng, R. Bai, J.P. Chen, Aminated polyacrylonitrile fibers for lead and copper removal, Langmuir,19 (2003)5058-5064]. Analysis using atomic force microscopy (AFM) showed that the surface roughness increased upon adsorption of the metal ion. Scanning electron microscopy (SEM) examination demonstrated that there were no cracks or sign of degradation on the surface after amination.     

An evaluation of hydroxyapatite-based filters for removal of heavy metal ions from aqueous solutions

Three hydroxyapatite(HA)-based materials have been investigated with respect to their potential for removing heavy metal ions from aqueous solutions. The materials have been evaluated as both loose powders and in the form of ceramic foams. The results have shown that all three grades of HA were found to be capable of removing a number of different ionic species although the more impure grades generally yielded the best performance. It is believed that the increased impurity levels resulted in increased numbers of lattice defects which were ideal adsorption/exchange sites. 100% removal could be achieved for some ions under the correct experimental conditions. For the ceramic foam filters, the optimum filtration parameters were found to be a high surface area, long filtration times, a low pH and a high filtrate temperature. Ion adsorption was positively detected as a mechanism of ion removal. Ion exchange was not observed but could not be completely ruled out.     

Fabrication and characterization of a boehmite nanoparticle impregnated electrospun fiber membrane for removal of metal ions

The fabrication of a composite electrospun fiber membrane with sorptive characteristics intended for removal of heavy metals was investigated. The electrospun fiber membrane was impregnated with nano-boehmite particles. The latter had been selected to increase surface area of the active component. Cd (II) was chosen as the challenge bivalent cation. The sorption capacity of the nano-boehmite was studied as a function of pH and time. Electrospinning was used to prepare the composite submicron fiber membrane impregnated with boehmite nanoparticles. The later was blended with the polymer to produce a homogenous mixture before electrospinning. Two polymers, the hydrophobic/PCL/and hydrophilic/Nylon-6/, were chosen to serve as the support for the boehmite. The nanoparticles and resulting composite membranes were characterized using SEM, TEM, and XRD techniques. XRD data confirmed the presence of nano-boehmite particles in the nanofibers membrane. The membranes so prepared were challenged with aqueous solutions of Cd in batch isotherm tests. Atomic absorption spectroscopy results show sorption of Cd (II) by boehmite impregnated electospun membrane was possible and a capacity of 0.20 mg/g was achieved.     

Comparison of synthesis of chelating resin silica-gel-supported diethylenetriamine and its removal properties for transition metal ions

Four kinds of silica-gel (SG)-supported diethylenetriamine (DETA) chelating resins SG-DETA-1, SG-DETA-2, SG-DETA-3, and SG-DETA-4 were prepared by functionalization of silica-gel via so-called "heterogeneous-direct-amination" (hetero-DA), "homogeneous-direct-amination" (homo-DA), "heterogeneous end-group protection" (hetero-EGP), and "homogeneous end-group protection" (homo-EGP) routes, respectively. These functionalized reactions on silica-gel were confirmed through elemental analysis, infrared spectroscopy, X-ray diffractometry, porous analysis, and thermogravimetry. Element analysis revealed that the direct-amination routes and homogeneous condition were more beneficial than the corresponding end-group protection routes and heterogeneous condition to the syntheses of chelating resins with high N content. Several metal ions, such as Ag(+), Cu(2+), Ni(2+), Hg(2+), Zn(2+) and Pb(2+), were chosen as representatives to investigate the relationship between adsorption capacities and N content of ligands onto the surface of silica-gel. The experiments results showed that all resins, SG-DETA-1, SG-DETA-2, SG-DETA-3 and SG-DETA-4, had a better adsorption for Hg(2+) and Cu(2+) than others. One conclusion should be drawn from the above compared experiments, that is, higher N content of silica-gel resins does not ensure a higher utilization ratio of N.     

反渗透、纳滤膜技术脱除小分子有机物的研究进展

对反渗透(RO)和纳滤(NF)技术分离难解离型小分子有机物和解离型小分子有机物水溶液的机理、研究进展和应用现状进行综述,在此基础上,对RO和NF分离小分子有机物水溶液的研究方向和应用前景进行分析和展望.