Ag+ ions imprinted cryogels for selective removal of silver ions from aqueous solutions

ABSTRACT

The removal of heavy metal ions from aquatic media or any conditions is crucial. Silver ions turn out to be the important example of this problem on earth when these are released to the environment. In the present study, silver ions (Ag⁺) imprinted poly(hydroxyethyl methacrylate) (PHEMA)-based cryogels were prepared using N-methacryloyl-L-cysteine as functional monomer, to be chelated with Ag⁺ ions. The maximum adsorption capacity of Ag⁺-imprinted polymeric cryogel was found to be 49.27 mg/g from aqueous solutions. To investigate the affinity of Ag⁺-imprinted PHEMAC cryogel column, photographic film material from the natural silver ion source was used. The recovery results were 72.8% for the Ag⁺-imprinted PHEMAC cryogel and 0.62% for the non-imprinted PHEMAC cryogels. These values clearly showed the selectivity of the Ag⁺-imprinted PHEMAC cryogel column. The adsorption–desorption cycle was performed more 10 times with use of the same Ag⁺-imprinted PHEMAC cryogel for the determination of reuse. These molecularly imprinted cryogels were used in adsorption process for a long time with no significant loss.     

Solvent extraction of silver(I) from nitrate media using thiourea derivatives

Liquid–liquid extraction of Ag(I) from nitrate solutions using N‐(N′,N′‐diethyl thiocarbamoyl)‐N″‐phenylbenzamidine (TCBA) and 1‐6,‐diethylcarbamoyl imino‐1,6‐diphenyl‐2,5 dithiahexane (TCTH) dissolved in cumene has been studied. The extraction of Ag(I) from 1 mol dm⁻³ NO₃⁻ solutions by TCTH and TCBA was investigated as a function of several variables: equilibration time, organic phase diluent, pH of aqueous phase, Ag(I) and NO₃⁻ concentration in aqueous phase as well as TCBA and TCTH concentrations. Experimental equilibrium data were analysed numerically using the programs LETAGROP‐DISTR and LETAPL and the results showed that Ag(I) extraction could be explained assuming the formation of AgL and AgNO₃HL with TCBA (HL) and AgNO₃S with TCTH (S). The metal extraction was not influenced significantly by the structures of the thiourea derivatives used as extractants. The back extraction of Ag(I) from loaded organic phase was performed using different strippants and 0.5 mol dm⁻³ NaSCN was found to be efficient for this purpose. © 2000 Society of Chemical Industry     

Cu(II) ions removal from wastewater using starch nanoparticles (SNPs): An eco-sustainable approach

The complex structured starch particles were reduced to the nanoscale size range through hydrolysis utilizing low concentration acid assisted by ultrasound irradiation. The synthesized starch nanoparticles (SNPs) were characterized by transmission electron microscopy (TEM), Fourier-transform infrared (FTIR), and X-ray diffraction (XRD) techniques. The synthesized SNPs possessed surface activated entities, as many cationic functional groups were confirmed through the FTIR spectrum. Also, these SNPs were effectively utilized to separate heavy Cu metal ions from the synthetic ion solution. The SNPs were characterized using field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) analysis for the surface modification after the adsorption process. The weak electrostatic interaction between the SNP surface and Cu ion was confirmed by the XPS spectrum and energy-dispersive X-ray spectroscopy. The maximum efficiency of Cu ions removal was about 93% at an optimal pH 5 and 25 mg/ml dosage. The adsorption equilibrium was obtained in 60 min. The nitrogen isotherm BET analysis of SNPs after adsorption shows a higher specific surface area of 18.552 m²/g, attributed to the interaction and presence of Cu ions on the SNP surface. The process feasibility was validated by the Langmuir isotherm model. The process exhibits pseudo-second-order adsorption kinetics and follows the Langmuir isotherm. The R_L predicted by the Langmuir isotherm mechanism is 0.017, implying favourable adsorption. The process is reproducible and allows for the separation of heavy metal ions from the wastewater through biosorption effectively.     

Ion imprinted polymers for the selective extraction of silver(I) ions in aqueous media: Kinetic modeling and isotherm studies

Ion imprinted polymers (IIPs) for selective extraction of Ag(I) ions from aqueous solution were synthesized by a precipitation polymerization method using two functional monomers, 4-vinyl pyridine (4-VP) and 1-vinyl imidazole (1-VID), and N,N-ethylene bisacrylamide (EBAm) as the cross linker. Batch adsorption experiments were carried out as a function of Ag(I) imprinted polymer amount, agitation time, pH and initial Ag(I) concentration. The kinetic studies indicated that pseudo-second-order kinetic model best describes the adsorption behavior, while the adsorption data correlated well with the Langmuir isotherm. Furthermore the selectivity studies revealed that the ion imprinted polymers had a higher absorption capacity and a higher selectivity, for the Ag(I) ions, than the control polymers.     

Adsorption of silver ions from industrial wastewater using waste coffee grounds

Waste coffee grounds were used as an adsorbent to efficiently adsorb silver ions in actual industrial waste-water. It was found that the functional groups like -COO^? and -OH^? groups in coffee grounds play an important role in the adsorption of silver ions from the FT-IR spectra, and the SEM images and EDX spectra were used to investigate the surface onto waste coffee grounds and confirm the existence of silver ions onto the waste coffee grounds after adsorption of silver ions. The highest adsorption capacity and removal efficiency was achieved as about 46.2mg/g and 92.4% at the initial pH 6 of wastewater. Two adsorption isotherm models, Langmuir and Freundlich, were used to analyze the equilibrium data. The Langmuir isotherm, which provided the best correlation for silver adsorption onto coffee grounds, showed that the maximum adsorption capacity and affinity constant was calculated as 49.543mg/g and 1.134 L/mg, respectively. The adsorption was an exothermic reaction and the most equilibrium was achieved at less than 60min. From these results, the waste coffee grounds have high possibility to be used as effective and economical adsorbent for silver adsorption.     

Electrochemical recovery of silver from waste aqueous Ag(I)/Ag(II) redox mediator solution used in mediated electro oxidation process

The paper presents a process for the electrochemical recovery of silver(Ag) by electro deposition on the electrode surface from the waste solutions of Ag(I)/Ag(II) redox system in nitric acid medium used for the mediated electrochemical process. Electrochemical recovery was carried out in an undivided cell with DSA-O₂ electrodes at room temperature condition. At an optimized current density of 12 A/dm², 99% of Ag recovery efficiency was achieved with high yield and low energy consumption. Experimental runs were made in order to observe the performance of the Ag recovery process. The operating conditions like current density, temperature and Ag(I) concentration of the electrolyte, the acid concentrations, agitation rate and inter-electrode distance were optimized.     

纳米银粒子制备及应用研究进展

综述了制备纳米银粒子的方法,主要包括液相化学还原法,电化学还原法、光化学还原法和分子自组装等,分析比较了这些方法的基本原理、制备过程及优缺点,阐述了纳米银粒子在化学反应,光学领域及抗菌等领域的应用.     

Performance of hollow fiber supported liquid membrane on the extraction of mercury(II) ions

The extraction and recovery or stripping of mercury ions from chloride media using microporous hydrophobic hollow fiber supported liquid membranes (HFSLM) has been studied. Tri-n-octylamine (TOA) dissolved in kerosene was used as an extractant. Sodium hydroxide was used as a stripping solution. The transport system was studied as a function of several variables: the concentration of hydrochloric acid in the feed solution, the concentration of TOA in the liquid membrane, the concentration of sodium hydroxide in the stripping solution, the concentration of mercury ions in the feed solution and the flow rates of both feed and stripping solutions. The results indicated that the maximum percentages of the extraction and recovery of mercury ions of 100% and 97% were achieved at the concentration of hydrochloric acid in the feed solution of 0.1 mol/l, the concentration of TOA at 3% v/v, the concentration of sodium hydroxide at 0.5 mol/l and the flow rates of the feed and stripping solutions of 100 ml/min. However, the concentration of mercury ions from 1–100 ppm in the feed solution had no effect on the percentages of extraction and recovery of mercury ions. Thus, these results have identified that the hollow fiber supported liquid membrane process has high efficiency on both the extraction and recovery of mercury (II) ions. Moreover, the mass transfer coefficients of the aqueous phase (k _i ) and membrane or organic phase (k _m ) were calculated. The mass transfer coefficients of the aqueous phase and organic phase are 0.42 and 1.67 cm/s, respectively. The mass transfer coefficient of the organic phase is higher than that of the aqueous phase. Therefore, the mass transfer controlling step is the diffusion of the mercury ions through the film layer between the feed solution and the liquid membrane.     

Adsorption studies of Cr(VI) and Cu(II) metal ions from aqueous solutions by synthesized Ag and Mg co-doped TiO2 nanoparticles

ABSTRACT

This communication provides the eliminating of heavy metals from water resources using Ag-Mg/TiO₂ nanoparticles. The nanoparticles with a size of 15 nm were prepared using sol-gel technique and used for the removal of Cr(VI) and Cu(II) from waste waters. Batch sorption studies were carried out to investigate the adsorption of the above metal ions for a concentration range of 0.1–10 mg/L. The maximum sorption capacity values were found to be 2.42 mg/g for Cr(VI) and 2.03 mg/g for Cu(II) at a concentration of 0.1 ppm. The mechanism of adsorption was also investigated. The results showed that both Freundlich and Dubinin–Radushkevitch isotherms were found to be the best fit for the adsorption of metals. The results from kinetic data reveal that the pseudo-second-order and Reichenberg film diffusion models were found to be well fit for the experimental data. The value of the thermodynamic parameter ΔH° revealed the endothermic adsorption process and negative value of ΔG° shows the feasibility and spontaneity of material–anion interaction. In addition, the method is considered to be simple and cost-effective, and shows excellent adsorption removal properties on heavy metals for industrial applications.     

Adsorption characteristics of waste crab shells for silver ions in industrial wastewater

Waste crab shells were used as an adsorbent to efficiently adsorb silver ions in actual industrial wastewater. The functional groups like -NHCO or -NO₂ groups in crab shells play an important role in the adsorption of silver ions. The highest removal efficiency was about 96% obtained from the 30 g/L of adsorbent concentration at initial pH 6.0 of waste solution. Langmuir sorption model was chosen to estimate the maximum uptake capacity and affinity constant of waste crab shells for silver ions, and its value was 5.21mg/g-dry mass and 0.411 L/mg, respectively. Entire adsorption process was completed in 60 min, and removal efficiency of crab shells was higher than that of Amberlite IR 120 plus resin. The effect of temperature could be neglected in the range of 15.0–45.0 °C. Also, instrumental analysis such as SEM (scanning electron microscopy) photographs, EDX (energy dispersive X-ray) spectrum, and FT-IR spectrum were applied to investigate the surface condition and functional groups of crab shells.     

Novel Ag(I) complexes with propeller-like structure of tripodal ligand: syntheses and structures of two- and three-coordinate silver (I) complexes

Two mononuclear Ag(I) complexes, [Ag(tbsb)](NO₃)·DMF (1) and [Ag(tbsb)](NO₃)·4.5H₂O (2) {tbsb=1,3,5-tris(2-benzimidazol)sulfanylmethyl)-2,4,6-trimethylbenzene}, have been synthesized by self-assembly reaction of AgNO₃ with tbsb and characterized structurally. The silver atoms of both the complexes are coordinated by the imine nitrogen atoms from a tripodal ligand (tbsb) to form two- and three-coordinate structures, respectively. Complex 1 presents the first example of silver (I) compound of the tripodal ligand possessing propeller-like structure.     

Use of electrodialysis to remove silver ions frommodel solutions and wastewater

The feasibility of the removal of Ag⁺ ions in a model solution and a sample of rinse water provided from an industrial plating plantwas investigated in a batch electrodialysis system. The experiments were carried out using two different types of ion-exchange membranes. The effects of applied potential, pH value and initial silver concentration on the duration of electrodialysis and energy consumption were examined. Full removal of Ag+ ions was achieved from model solutions and the sample of rinse water. The most convenient applied voltage and energy consumption values to remove silver ions are reported. These results will be useful for designing and operating different capacities of electrodialysis plants for recovering Ag⁺ ions.     

Removal of Ag(l), Cu(II) and Zn(ll) ions with a supported liquid membrane containing cryptands as carriers

The interface behaviour in the facilitated co-transport of Ag(I), Cu(II) and Zn(II) ions through supported liquid membranes (SLMs) made of a flat-sheet polypropylene membrane support containing cryptands (2.2.2 or 2.2.1) as carriers was studied. The liquid-liquid extraction tests showed a maximum distribution coefficient when the carrier concentration was greaterthan 10⁻⁴M. In transport experiments the transmembrane flux increased with increasing carrier concentration reaching a limiting value at greater than 10⁻³M concentration. The calculation ofthe diffusion coefficients in membranes showed ahigherdiffusivityof2.2.2-metal complexes with respect to 2.2.1-metal complexes for silver ions. A sequence of diffusivity D(Ag+)>D(Cu²⁺)>D(Zn²⁺) was obtained, but carrier 2.2.1 showed a higher selectivity through copper ions. A sequence of diffusivity D(Cu²⁺)>D(Zn²⁺)>D(Ag⁺) was obtained. The diffusivity was significantly higher when using Celgard 2500 support compared to Celgard 2400 or 2402. Variable metal ion concentrations in the feed phase fluxes almost zero, at less than 10⁻² M concentration, were obtained. In the transient state of the transport through the SLM, different molar flow rates at the feed-membrane and membrane-strip interfaces were observed. The selectivity of the interfaces containing 2.2.2 in the separation binary mixtures of ions showed the following separation factors: SF_AgZn = 2.50, SF_AgCu = 1.64, SF_cuZn = 1.42.     

Microwave-assisted synthesis of BSA-protected small gold nanoclusters and their fluorescence-enhanced sensing of silver(I) ions

A one-step microwave-assisted method is used for the synthesis of small gold nanoclusters, Au(16)NCs@BSA, which are used as a fluorescence enhanced sensor for detection of silver(I) ions with high selectivity and sensitivity.     

离心—光度法测定银

研究了三元配合物离心－光度测定银的新方法,在Ａｇ（Ｉ）－邻菲罗啉－溴邻苯三酚红的乙醇有色型体溶液中,于λｍａｘ＝６０６ｎｍ处测定表观摩尔吸光系数ε为４．０＊１０＾４Ｌ．ｍｏｌ＾－１．ｃｍ＾－１。     

Magnetic polyresorcinol@CoFe2O4@MnS nanoparticles for adsorption of Pb(II), Ag(I), Cr(VI) and bacteria from water solution

Polymer Bulletin - This study devoted to developing an efficient adsorbent with the excellent adsorption performance of heavy metals and bacteria capturing. Polyresorcinol@CoFe2O4 was synthesized...     

硫杂冠醚对Ag(I)和Tl(I)的萃取

基于冠醚的配位化学及软硬酸碱理论,设计并合成了五种硫杂冠醚,系统研究了其对Ag(I)和Tl(I)两种软酸离子的络合能力.模拟计算结果表明,五种冠醚与Ag(I)和Tl(I)络合后构型均发生了转变,且结构优化后的五种冠醚与Ag(I)络合过程的ΔG和ΔU均较负,表现出了一定的配位能力,而与Tl(I)络合过程的ΔG和ΔU均接近...