Biosorbents based on pine sawdust and malt sprouts for preconcentration and ICP-OES determination of nonferrous,heavy, and precious metals in the environmental samples

Pine sawdust and malt sprouts modified with orthophosphoric acid and carbamide have been proposed for solid-phase extraction (SPE) of nonferrous, heavy, and precious metals and their subsequent determination in the environmental samples by inductively coupled plasma optical emission spectrometry (ICP-OES). Modified adsorbents were characterized by SEM, TGA, and FT-IR and compared with native matrixes. SPE of some nonferrous and precious metal ions by biosorbents was studied. Depending on the SPE conditions, it was possible to separate nonferrous and heavy metals from alkali and alkaline earth metals. The proposed adsorbents are effective for preconcentration of nonferrous and heavy metals from natural waters and precious metals from solutions after digestion of geological samples.     

苯基键合硅胶萃取黄酮化合物的性能研究

以苯基三氯硅烷和硅胶为原料制得苯基键合硅胶固相萃取材料,采用扫描电镜、元素分析、比表面积/孔径分析、红外光谱等对其进行了结构表征。装填固相萃取小柱,以4个黄酮模型化合物为目标分析物,研究苯基键合硅胶的萃取性能。对上样体积、上样速度、上样pH、洗脱剂类型、洗脱体积、洗脱速度等萃取参数进行了优化,并建立了苯基键合硅胶富集萃取黄酮化合物的高效液相色谱分析检测方法。实验证实该方法具有宽的线性范围(1~200μg/L)、低的检出限(0.25μg/L),并成功应用于2种实际样品中黄酮化合物的富集检测。上述结果说明苯基键合硅胶是一种对黄酮化合物具有良好萃取性能的固相萃取材料。     

Dispersion of phosphovanadates on silica gel chemically modified with silane coupling agents having an amino group and their catalytic activities for methanol oxidation

Phosphotetradecavanadate (PV14) was dispersed on a silica gel chemically modified with a silane coupling agent (AnPS-SiO₂) by an equilibrium adsorption method. The PV14 contents approximately correlated with the V(IV) spin contents by ESR. PV14 dispersed on AnPS-SiO₂ resulted in a quite high selectivity for formaldehyde such as 97% in methanol oxidation.     

An electroanalytical application of 2-aminothiazole-modified silica gel after adsorption and separation of Hg(II) from heavy metals in aqueous solution

2-Aminothiazole covalently attached to a silica gel surface was prepared in order to obtain an adsorbent for Hg(II) ions having the following characteristics: good sorption capacity, chemical stability under conditions of use, and, especially, high selectivity. The accumulation voltammetry of mercury(II) was investigated at a carbon paste electrode chemically modified with silica gel functionalized with 2-aminothiazole (SIAMT-CPE). The repetitive cyclic voltammogram of mercury(II) solution in the potential range −0.2 to +0.6 V versus Ag/AgCl (0.02 mol L⁻¹ KNO₃; v=20 mV s−1) show two peaks one at about 0.1 V and other at 0.205 V. The anodic wave peak at 0.205 V is well defined and does not change during the cycles and it was therefore further investigated for analytical purposes using differential pulse anodic stripping voltammetry in differents supporting electrolytes. The mercury response was evaluated with respect to pH, electrode composition, preconcentration time, mercury concentration, “cleaning” solution, possible interferences and other variables. The precision for six determinations (n = 6) of 0.02 and 0.20 mg L⁻¹ Hg(II) was 4.1 and 3.5% (relative standard deviation), respectively. The detection limit was estimated as 0.10 μg L⁻¹ mercury(II) by means of 3:1 current-to-noise ratio in connection with the optimization of the various parameters involved and using the highest-possible analyser sensitivity.     

硅胶改性壳聚糖膜的制备及其对Cu2+的吸附性能

重金属是水体中十分严重的生态环境污染之一,而壳聚糖具有较强的重金属吸附能力。采用硅胶粒子浸出法制备出大孔壳聚糖膜,并且研究了其对重金属Cu²⁺的吸附性能。发现3.0 g壳聚糖溶于10%（质量分数）的乙酸溶液中,加入3.0 g硅胶再经过戊二醛交联后制备出大孔壳聚糖膜的吸附能力较好。在40 mL、400 mg/L的CuSO₄溶液中,加入0.4 g制备好的壳聚糖膜,经过25 h后,壳聚糖膜呈蓝色,用紫脲酸铵指示反应为紫色,吸附率为93%。说明壳聚糖膜对Cu²⁺具有良好的吸附能力,吸附过后膜很容易从溶液中取出,克服了传统的吸附剂在溶液中固液分离困难的问题。     

Removal, preconcentration and determination of trace heavy metal ions in water samples by AAS via chemically modified silica gel N-(1-carboxy-6-hydroxy) benzylidenepropylamine ion exchanger

The use of chemically modified silica gel N-(1-carboxy-6-hydroxy) benzylidenepropylamine (SiG-CHBPA), ion exchanger for removal and preconcentration of Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb in natural water samples collected from River Nile, Mediterranean Sea and other locations followed by their consecutive AAS determination was described. The effects on the percentage of recovered metal ions including mass change of ion exchanger, stirring time, pH of sample solutions and eluent concentration were studied. The distribution coefficient K_d, ml g^− 1 and the percentage concentration of the studied metal ions on the ion exchanger at equilibrium, C_M,_eqm ,% (Recovery, %) were studied as a function of experimental parameters. The logarithmic values of the distribution coefficients, log K_d are 3-6.3. The interfering effects of some foreign ions on the removal, preconcentration and determination of the investigated metal ions were described. The metal-chelates formed between the ion exchanger and the studied metal ions were characterized by IR (absorption and reflectance), UV spectrometry, potentiometric titration and thermal analysis (TG and DTG). The reliability of the present method was confirmed by the comparison with a standard solvent extraction method. The present method is simple and rapidly applicable for the determination of the studied metal ions, ng ml^− 1 in different natural water samples.     

Extraction and recovery of soft metal ion by porous silica coated by hydrophilic polymer gel with hexavalent nitrogen-donor ligand

A hydrophilic N-isopropylacrylamide (NIPA) gel copolymerized with a hexavalent nitrogen donor ligand, N,N,N’,N’-tetrakis(4-propenyloxy-2-pyridylmethyl)ethylenediamine (TPPEN), adsorbs soft metals selectively from the acidic aqueous phase. We are developing porous silica particles coating the TPPEN-NIPA gel with high TPPEN content thinly on the pore surface of porous silica by a new gel-coating method using surface tension. Half of the pore volume of the silica particles remained by the coating of the TPPEN-NIPA gel with the high TPPEN content of 30 mol%. A large separation factor (SF) of Cd(II)/Eu(III) of 60 was observed at pH 2. The proposed chromatographic agent with the high TPPEN content is applicable for practical use.     

Determination of picomolar silver concentrations by differential pulse anodic stripping voltammetry at a carbon paste electrode modified with phenylthiourea-functionalized high ordered nanoporous silica gel

This study introduces the design of an anodic stripping voltammetric (ASV) method for the silver ion determination at a carbon paste electrode (CPE), chemically modified with phenylthiourea-nanoporous silica gel (Tu-SBA-15-CPE). The electroanalytical pro includes two steps: preconcentration of metal ions at an electrode surface, followed by quantification of the accumulated species by differential pulse anodic stripping voltammetric methods. Factors affecting the performance of the anodic stripping were investigated, including the modifier quantity in the paste, the electrolyte concentrations, the solution pH and the accumulation potential or time. The most sensitive and reliable electrode contained 10% Tu-SBA-15 and 90% carbon paste. The accumulation potential and time were set at, −200 mV and 300 s, respectively, and the scan rate at 50 mV s⁻¹ in the scan range of −200 to 700 mV. The resulting electrode demonstrated a linear response over range of silver ion concentration of 8.0-80 pmol/L with detection limit (S/N = 3) of 5 pmol/L. The prepared electrodes were used for the silver determination in sea and tap water samples and very good recovery results were obtained. The accuracy was assessed through recovery experiments and independent analysis by graphite furnace atomic absorption spectrometry.     

An effective separation and purification of rutin and scoparone from Herba Artemisiae Scopariae by solid-phase extraction cartridges packed with an ionic liquid-based silica

Five types of ionic liquid-based silica were synthesized as solid-phase extraction (SPE) sorbents for separation and purification of bioactive compounds, that is, rutin and scoparone extracted from Herba Artemisiae Scopariae. The SilprBImCl material with the highest adsorption capacity was selected as the sorbent for SPE packing. Ethyl acetate and water were found to be suitable washing and eluting solvents, respectively. SilprBImCl was then applied to multi-phase extraction, and its superiority as a sorbent over the commercial cartridge was proven with high rutin and scoparone recoveries of 90.5% and 83.9%, respectively. This highlights the potential of ionic liquid-based silica materials applied to SPE and MPE.     

Study on adsorption of nonionic and cationic polymers on silica gel by using total organic carbon analysis

The adsorption behaviour of poly(ethylene oxide) and trimethylammonium glycol chitosan iodide from water onto silica gel is reported. A total organic carbon analytical method was employed to determine precisely the small quantity of polymer remaining after the attainment of adsorption equilibrium. The adsorption isotherms and the curves of equilibrium adsorption against pH were obtained and compared with the ionization properties of the silanol groups investigated by potentiometric titration. The results obtained are discussed in terms of the adsorption mechanism for nonionic and cationic polymers.     

Directly silica bonded analytical reagents: synthesis of 2-mercaptobenzothiazole–silica gel and its application as a new sorbent for preconcentration and determination of silver ion using solid-phase extraction method

A new and efficient method is described for the easy synthesis of directly bonded 2-mercaptobenzothiazole–silica gel. This new bonded analytical reagent is used as an effective sorbent for the solid-phase extraction of silver ion from aqueous solutions. Conditions for effective adsorption of trace levels of silver ion concentration are optimized with respect to different experimental parameters in column process. Sodium thiosulfate solution could efficiently elute the adsorbed silver ion from the surface of the sorbent which then was determined by atomic absorption spectroscopy (AAS). Common coexisting ions did not interfere with the separation and determination. The preconcentration factor is 300 (1 ml elution volume) for a 300 ml sample volume. The sorbent exhibited excellent stability and its sorption capacity under optimum conditions has been found to be 343 μg of silver per gram of sorbent. The relative standard deviation under optimum conditions is 2.04% (n=7). Accuracy of the method was estimated by using test samples of natural water spiked with different amounts of silver ion. The method is simple and inexpensive.     

Promethazine determination in plasma samples by using carbon paste electrode modified with molecularly imprinted polymer (MIP): Coupling of extraction, preconcentration and electrochemical determination

A promethazine (PMZ) molecularly imprinted polymer (MIP) and a non-imprinted polymer (NIP) were synthesized by two different formulations of methacrylic acid-ethylene glycol dimethacrylate (MAA-EGDMA) and vinyl benzene-divinyl benzene (VB-DVB). Then, the MIPs were used to modify the carbon paste electrode (CP). The response difference between MIP-CP and NIP-CP electrodes, containing VB-DVB polymer, was higher than that for MIP-CP and NIP-CP modified with polymer of MAA-EGDMA, indicating the lower nonselective surface adsorption property of the VB-DVB based MIP. The MIP, incorporated in the carbon paste electrode, functioned as selectively recognition element and pre-concentrator agent for PMZ determination. The prepared electrode was used for PMZ measurement by the three steps procedure including analyte extraction in the electrode, electrode washing and electrochemical measurement of PMZ. It was shown that the electrode washing, after PMZ extraction, led to enhanced selectivity. Square wave voltammetry (SWV) for PMZ determination by proposed electrode was proved to be better than that of differential pulse voltammetry. Some parameters, effective on the electrode response, were optimized and then a calibration curve was plotted. Two dynamic linear range of 7 × 10⁻⁹ to 4 × 10⁻⁷ and 4 × 10⁻⁷ to 7 × 10⁻⁶ mol L⁻¹ were obtained. The detection limit of the method was calculated equal to 3.2 × 10⁻⁹ mol L⁻¹. This method was used successful for PMZ determination in blood serum sample.     

Separation/Preconcentration of Zn(II), Cu(II), and Cd(II) by Saccharomyces carlsbergensis Immobilized on Silica Gel 60 in Various Samples

Abstract

This study presents a solid phase extraction procedure based on column biosorption of Zn(II), Cu(II), and Cd(II) ions on Saccharomyces carlsbergensis immobilized on silica gel 60. The analytes were determined by flame atomic absorption spectrometry (FAAS). The optimum conditions for the quantitative recovery of the analytes, including pH, amount of solid‐phase, eluent type and flow rate of sample solution were examined. The effect of interfering ions on the recovery of the analytes was also investigated. Under the optimum conditions, recoveries of Zn(II), Cu(II), and Cd(II) were 99±2%, 98±2%, and 100±2% at 95% confidence level, respectively for spiked water samples. The analytical detection limits for Zn(II), Cu(II), and Cd(II) were 1.14, 1.66, and 1.48 ng mL^?1, respectively. The validation of the method was checked by the analysis of standard reference material (Tea leaves GBW‐07605) and spiked water, samples. The proposed method was applied for the determination of analytes in green onion, parsley, dam water, lake water, and tap water samples. The analytes has been determined in real samples with relative error lower than 8% and relative standard deviation lower than 10%.     

Kinetics of esterification of palmitic acid with isopropanol using p‐toluene sulfonic acid and zinc ethanoate supported over silica gel as catalysts

Kinetic data on the esterification of palmitic acid with isopropanol were obtained using homogeneous (para‐toluene sulfonic acid, p‐TSA) and heterogeneous (zinc ethanoate coated on silica gel, ZnA/SG) catalysts in a batch reactor. The ZnA/SG catalyst was prepared using a sol–gel technique. The esterification reaction was studied at different reaction temperatures (373–443 K), initial reactants molar ratio (1–5), catalyst loading (1–5 gcat dm^?3) and water concentration in feed (0–15 vol%). A power law rate equation was used for homogeneous kinetics analysis. The Langmuir Hinshelwood Hougen Watson (LHHW) model was used for heterogeneous kinetics. The kinetic parameters of both models were obtained using Polymath software. The reaction parameters were used to obtain simulated values of conversion for both catalytic systems. The simulated values were compared with the experimental values and were in good agreement. Copyright © 2004 Society of Chemical Industry     

Separation,Preconcentration, and Recovery of Pd(II) Ions using Newly Modified Silica Gel with Bis(3-Aminopropyl)Amine

Bis(3-aminopropyl)amine bonded silica gel (BAPA-SG) was synthesized and characterized by elemental analysis and FT-IR spectroscopy, and tested for adsorption, preconcentration, and recovery of Pd(II) ions. The effective parameters on the preconcentration of Pd(II) ions such as pH, volume, and flow rate of the Pd(II) solution, and the type and volume of eluent solution, and also matrix ions such as alkaline and heavy metals were investigated. Flame atomic absorption spectrometry was used for the determination of Pd(II) concentration. The modified silica gel could adsorb Pd(II) ions quantitatively from the solutions up to 400 mL at pH 1.0 by the flow rate of 5 mL/min. The retained Pd(II) ions could be easily eluted by using 5 mL of 1% (m/v) thiourea in 1.0 M HCl solution. The recovery of Pd(II) ions was 95 ± 2% at 95% confidence level. The analytical detection limit of Pd was found to be 0.36 µg L^?1 at the preconcentration factor of 80. Selective adsorption of Pd(II) ions over some base metal ions was also investigated. The developed method was applied to spent auto catalyst for palladium recovery, and a certified ore sample for the determination of palladium content.     

Separation and preconcentration of lead,chromium and copper by using with the combination coprecipitation-flame atomic absorption spectrometric determination

A coprecipitation method was developed for the quantitative separation and preconcentration of Pb(II), Cr(III) and Cu(II) ions. Analytes were coprecipitated using a triazole derivative (2-{4-[2-(1H-indol-3-yl)ethyl]-3-(4-chlorobenzyl)-5-oxo-4,5-dihydro-1H-1,2,4-triazol-1-yl}-N-aryl methylidene acetohydrazid). The analytes were analyzed by flame atomic absorption spectrometry. The parameters such as sample pH, amount of reagent, sample volume, matrix effects etc. were investigated. The enrichment factor for the analyzed metal ions was obtained as 50. The relative standard deviations (RSD) were in the range of 2.8–4.1%. The accuracy of the proposed procedure was checked by the analysis of the CRM-C-Sandy Soil C. The method was successfully applied to real samples.     

Separation and recovery of heavy metals from concentrated smelting wastewater by synergistic solvent extraction using a mixture of 2-hydroxy-5-nonylacetophenone oxime and bis(2,4,4-trimethylpentyl) -phosphinic acid

Extraction and separation of copper, zinc, nickel, and cadmium from calcium and magnesium in concentrated smelting wastewater by synergistic solvent extraction using a mixture of 2-hydroxy-5-nonylacetophenone oxime (Mextral 84H) and bis(2,4,4 -trimethylpentyl)-phosphinic acid (Cyanex 272) in an aliphatic diluent (DT-100) was studied. The effects of extractant concentrations, equilibrium pH, organic-to-aqueous phase ratios, system temperature, and extraction and stripping efficiencies on the extraction performance of the heavy metals were investigated. Extraction of pH isotherms showed that addition of Cyanex 272 to Mextral 84H causes obvious synergistic shifts for zinc and cadmium and a slightly antagonistic shift for nickel. The separation factor of cadmium over magnesium was 155.7 and the ΔpH₅₀ values between the metals were over 1.00 pH units. Semi-continuous tests for the metals extraction, scrubbing, and stripping were conducted in a continuous extraction apparatus with conditions further optimized for separation of the metals. Nearly 100% of the copper and nickel and over 98% of the zinc and cadmium were recovered with less than 0.1 mg/L copper and nickel, 26 mg/L of zinc, and 10 mg/L of cadmium remaining in the raffinate. A process in which all valuable metals are extracted simultaneously and stripped selectively at optimal conditions is proposed that is entirely feasible for the separation of copper, zinc, nickel, and cadmium from calcium and magnesium in concentrated smelting wastewater. The study determines the fundamental parameters for the treatment of smelting wastewater by solvent extraction.