Synthesis of ion-imprinted mesoporous silica gel sorbent for selective adsorption of copper ions in aqueous media

A new Cu(II) ion-imprinted sorbent was synthesized by a surface imprinting technique and characterized by FT-IR and SEM. Compared to the non-imprinted sorbent, the Cu(II) ion-imprinted sorbent had a higher adsorption capacity and selectivity for Cu(II). The static adsorption capacity of the Cu(II) ion-imprinted sorbent and non-imprinted sorbent for Cu(II) were 84.5 and 46.5 μmol?g^?1, respectively. The best selectivity coefficient over Zn(II) or Cd(II) ion was over 12. The relative selectivity coefficients of the sorbent for Cu(II) in the presence of Zn(II) and Cd(II) were 13 and 35, respectively. Furthermore, the new sorbent possessed a fast kinetics for Cu(II) sorption from aqueous solution with saturation time of <30 min, and could be used repeatedly. The standard deviation for 11 replicate determinations of 0.5 mg?L^?1 Cu(II) was 0.8%. This new Cu(II) ion-imprinted sorbent can be used as an effective solid-phase extraction material for the selective preconcentration and separation of Cu(II).     

Retention profile of Fe,Mn and Cu onto chemically treated polyurethane with carbon disulfide

Dithiocarbamate modified polyurethane foam (DTC-PUF) was synthesized as a new solid-phase extraction sorbent for the preconcentration and determination of Fe(II), Mn(II) and Cu(II) in environmental samples using flame atomic absorption spectrometry. Maximum extraction of the elements was achieved at pH 5–7 and flow rate 3 mL min^?1. Quantitative desorption was achieved by 10 mL from 1.0 mol L^?1 HCl solution. The capacity of the sorbent was 149.2 ± 0.5, 237.5 ± 0.2, 200.2 ± 0.1 μg g^?1 and the limit of detection was of 0.015, 0.015 and 0.012 μg mL^?1for Fe(II), Mn(II) and Cu(II), respectively. A preconcentration factor of 100 was obtained for all elements. The developed method was successfully applied to the determination of the tested elements in water (tap and lake) and plant (spinach and parsley leaves) samples and showed good recovery values from 98 to 111% with corresponding RSD values ranged from 0.6 to 8.6%.     

A Ce3+-imprinted functionalized potassium tetratitanate whisker sorbent prepared by surface molecularly imprinting technique for selective separation and determination of Ce3+

A surface molecular imprinting technology was developed to adsorb Ce(III) ions that showed much higher adsorption affinity and selectivity for than for other metal ions. The batch adsorption process was studied with respect to effects of pH value, residence time, temperature, and initial concentration of Ce(III) ion. The maximum adsorption capacity is 43 mg g^?1 at an initial Ce(III) concentration of 300 mg L^?1 and at a sorbent dosage of 1.0 g L^?1. A Langmuir isotherm fits the experimental data. The imprinted sorbent exhibits a much higher separation and selectivity for the target imprinted ion than the non-imprinted polymer. Cerium ion can be desorbed with 1M hydrochloric acid solution which is also proven by scanning electron microoscopy and X-ray diffraction experiments. The limit of detection is 37 ng mL^?1. The sorbent has been applied to the determination of trace cerium in different environmental samples with satisfactory results.     

Application of a new nanoporous sorbent for extraction and pre-concentration of lead and copper ions

The authors describe a method for the trace determination of copper (II) and lead (II) in water and fish samples using solid-phase extraction via siliceous mesocellular foam functionalised by dithizone. Siliceous mesocellular was functionalised with dithizone, and the resulting sorbent was characterised by scanning electron microscopy, surface area analysis, thermogravimetric/differential thermal analysis and FTIR. Following solid-phase extraction of target ions by the sorbent, copper and lead ions were quantified by flame atomic absorption spectrometry. Factors affecting the sorption and desorption of target ions by the sorbent were evaluated and optimised. The calibration plot is linear in the 1 – 500 μg L^?1 copper (II) and 3–700 μg L^?1 lead (II) concentration range. The relative recovery efficiency in real sample analysis is in the range from 96 to 102%, and precision varies between 1.7 and 2.8%. It is should be noted that the limits of detection for the copper and lead analysis were 0.8 and 1.6 μg L^?1, respectively. Also, the adsorption capacities for copper and lead ions were 120 and 160 mg g^?1, respectively. The obtained pre-concentration factor for the lead and copper ions by the proposed solid-phase extraction was 75. The method was successfully applied to the determination of low levels of copper (II) and lead (II) in tap, Caspian sea, Persian gulf and lake water and also their detection in fish samples.     

Speciation and determination of chromium ions by dispersive micro solid phase extraction using magnetic graphene oxide followed by flame atomic absorption spectrometry

A selective, simple and fast dispersive micro solid phase extraction method using magnetic graphene oxide (GO) as an efficient sorbent has been developed for the extraction, separation and speciation analysis of chromium ions. The method is based on different adsorption behaviour of Cr(VI) and Cr(III) species onto magnetic GO in aqueous solutions which allowed the selective separation and extraction of Cr(VI) in the pH range of 2.0–3.0. The retained Cr(VI) ions by the sorbent were eluted using 0.5 mL of 0.5 mol L^?1 nitric acid solution in methanol and determined by ?ame atomic absorption spectrometry. Total chromium content was determined after the oxidation of Cr(III) to Cr(VI) by potassium permanganate. All effective parameters on the performance of the extraction process were thoroughly investigated and optimised. Under the optimised conditions, the method exhibited a linear dynamic range of 0.5–50.0 µg L^?1 with a detection limit of 0.1 µg L^?1 and pre-concentration factor of 200. The relative standard deviations of 3.8% and 4.6% (n = 8) were obtained at 25.0 µg L^?1 level of Cr(VI) for intra- and inter-day analysis, respectively. The method was successfully applied to the speciation and determination of Cr(VI) and Cr(III) in environmental water samples.     

Multi‐Walled Carbon Nanotubes as Sorbent for Flow Injection On‐Line Microcolumn Preconcentration Coupled with Flame Atomic Absorption Spectrometry for Determination of Cadmium and Copper

Abstract

Multi‐walled carbon nanotubes (MWNTs) were used as sorbent for flow injection (FI) on‐line microcolumn preconcentration coupled with flame atomic absorption spectrometry (FAAS) for determination of trace cadmium and copper in environmental and biological samples. Effective preconcentration of trace cadmium and copper was achieved in a pH range of 4.5–6.5 and 5.0–7.5, respectively. The retained cadmium and copper were efficiently eluted with 0.5 mol L^?1 HCl for on‐line FAAS determination. The MWNTs packed microcolumn exhibited fairly fast kinetics for the adsorption of cadmium and copper, permitting the use of high sample flow rates up to at least 7.8 mL min^?1 for the FI on‐line microcolumn preconcentration system without loss of the retention efficiency. With a preconcentration time of 60 sec at a sample loading flow rate of 4.3 mL min^?1, the enhancement factor was 24 for cadmium and 25 for copper at a sample throughput of 45 h^?1. The detection limits (3σ) were 0.30 and 0.11 µg L^?1 for Cd and Cu, respectively. The precision (RSD) for 11 replicate measurements was 2.1% at the 10‐µg L^?1 Cd level and 2.4% at the 10‐µg L^?1 Cu level. The developed method was successfully applied to the determination of trace Cd and Cu in a variety of environmental and biological samples.     

Solid phase extraction of hexavalent chromium by Mannich base polymer wrapped flower-like layered double hydroxide

In the present work, synthesis of polymer wrapped flower-like MgAl layered double hydroxide was done through condensation of 1,4 phenylenediamine and resorcinol by p-formaldehyde. The nanocomposite was characterised with X-ray diffraction analysis, fourier transform infrared spectroscopy, thermogravimetric analysis and field emission scanning electron microscopy techniques and employed for effective adsorption of Cr(VI) from aqueous solution prior to flame atomic absorption spectrometer determination. Optimum level of effective parameters (pH, reaction time and adsorbent dosage) and their interaction was determined by response surface methodology. To investigate applicability of method for trace heavy metal adsorption, the method was employed for preconcentration of Cr(VI) in water samples. At the optimum conditions, pH = 4.5, shaking time of 15 min and adsorbent dosage of 20 mg, analytical performance of the method was evaluated and results showed that calibration curve is linear in the concentration range of 2–100 μg L^?1. Moreover, limit of detection was 0.22 µg L^?1 and relative standard deviation of six replicate experiments at initial concentration of 0.1 mg L^?1 was 3.3%. Isotherm study showed that Freundlich model can better describe adsorption behaviour as well as the sorbent showed the adsorption capacity of 62.5 mg g^?1. Moreover, thermodynamic study revealed that chromate adsorption was spontaneous and followed the endothermic path. Regeneration of sorbent was performed using 1.0 mol L^?1 of NaOH solution. The sorbent was employed for Cr(VI) determination from food additives and seawater samples.     

Preconcentration of Trace Cadmium (II) and Copper (II) in Environmental Water Using a Column Packed with Modified Silica Gel-Chitosan Prior to Flame Atomic Absorption Spectrometry Determination

A new column loaded with modified silica gel-chitosan is proposed as a preconcentration system for adsorption of trace cadmium (II) and copper (II). The optimization steps were performed under dynamic conditions, involving pH, sample flow rate, eluent selection, concentration, volume, and flow rate. Trace Cd(II) and Cu(II) were quantitatively adsorbed by the modified silica gel-chitosan. The metal ions adsorbed on the separation column were eluted with 0.1 M HNO₃ and determined by flame atomic absorption spectrometry. Under the optimum conditions, this method allowed the determination of cadmium and copper with limits of detection (LOD) of 20 ng L^?1 and 38 ng L^?1, respectively. The relative standard deviation values (RSDs) for 1.0 mg L^?1 of cadmium and 1.0 mg L^?1 of copper were 2.62% and 2.85%, respectively.     

Chemically modified silica gel for selective solid-phase extraction and preconcentration of heavy metal ions

This paper describes our research on the synthesis of the sorbent with chemically bonded ketoimine groups, and, furthermore, using this sorbent in the SPE technique to extract and preconcentrate trace amounts of metal ions in water samples. Surface characteristics of the sorbent were determined by elemental analysis, NMR spectra for the solid phases (²⁹Si CP MAS NMR), and analysis of pore size distribution of the sorbent and nitrogen adsorption-desorption. The newly proposed sorbent with ketoimine groups was applied for the extraction and preconcentration of trace amounts of Cu (II), Cr (III) and Zn (II) ions from the water from a lake, post-industrial water and purified water unburdened back to the lake. The determination of the transition-metal ions was performed on an emission spectroscope with inductively coupled plasma ICP-OES. For the batch method, the optimum pH range for Cu (II) and Cr (III) extraction was equal to 5, and Zn(II)–to 8. All the metal ions can be desorbed from SPE columns with 10?mL of 0.5?mol?HNO₃. The detection limits of the method were found to be 0.7?µg?L^?1 for Cu (II), 0.08?µg?L^?1 for Cr (III), and 0.2?µg?L^?1 for Zn (II), respectively.     

Preconcentration of trace amounts of cobalt (II) ions in water and agricultural products samples using of 5-(4-dimethylaminobenzylidene) rhodanin modified SBA-15 sorbent prior to FAAS determination

In the present study, the ?5-(4-dimethylaminobenzylidene)rhodanin-modified SBA-15? was applied as stable solid sorbent for the separation and preconcentration of trace amounts of cobalt ions in aqueous solution. SBA-15 was modified by ?5-(4-dimethylaminobenzylidene)rhodanin reagent. The sorption of Co²⁺ ions was done onto modified sorbent in the pH range of 6.8–7.9 and desorption occurred in 5.0 mL of 3.0 mol L^?1 HNO₃. The results exhibit a linear dynamic range from 0.01 to 6.0 mg L^?1 for cobalt. Intra-day (repeatability) and inter-day (reproducibility) for 10 replicated determination of 0.06 mg L^?1 of cobalt was ±1.82% and ?±1.97%?. Detection limit was 4.2 µg L^?1 (3S_b, n = 5) and preconcentration factor was 80. The effects of the experimental parameters, including the sample pH, flow rates of sample and eluent solution, eluent type and interference ions were studied for the preconcentration of Co²⁺. The proposed method was applied for the determination of cobalt in standard samples, water samples and agricultural products.     

New Application of Chemically Modified Multiwalled Carbon Nanotubes with Thiosemicarbazide as a Sorbent for Separation and Preconcentration of Trace Amounts of Co(II), Cd(II), Cu(II), and Zn(II) in Environmental and Biological Samples Prior to Determination by Flame Atomic Absorption Spectrometry

The present article reports the application of Thiosemicarbazide‐modified multiwalled carbon nanotubes (MWCNTs‐TSC) as a new, easily prepared selective and stable solid sorbent for the preconcentration of trace Co(II), Cd(II), Cu(II) and Zn(II) ions in aqueous solution prior to the determination by flame atomic absorption spectrometry. The studied metal ions can be adsorbed quantitatively on MMWNTs at pH 5.0 and then eluted completely with HNO₃ (1.5 mol L^?1) prior to their determination by flame atomic absorption spectrometry. The separation/preconcentration conditions of analytes were investigated, including the pH, the sample flow rate and volume, the elution condition and the interfering ions. The maximum adsorption capacity of the adsorbent at optimum conditions were found to be 32.5, 27.3, 44.5 and 34.1 mg g^?1 for Co(II), Cd(II), Cu(II) and Zn(II), and the detection limits of the method were found to be 0.28, 0.13, 0.21 and 0.17 μg L^?1, respectively. The proposed method was successfully applied for extraction and determination of the analytes in well water, sea water, wastewater, soil, and blood samples.     

Selective solid-phase extraction of lead(II) from biological and natural water samples using surface-grafted lead(II)-imprinted polymers

A new Pb(II)-imprinted amino-functionalized silica gel sorbent was synthesized by an easy one-step reaction by combining a surface imprinting technique for selective solid-phase extraction of trace Pb(II) prior to its determination by inductively coupled plasma optical emission spectrometry. The Pb(II)-imprinted amino-functionalized silica gel sorbent was characterized by Fourier transform infrared spectroscopy. Compared to non-imprinted polymer particles, the ion-imprinted polymers had higher selectivity and adsorption capacity for Pb(II). The maximum static adsorption capacity of the ion-imprinted and non-imprinted sorbent for Pb(II) was 19.66 and 6.20 mg g^?1, respectively. The largest selectivity coefficient of the Pb(II)-imprinted sorbent for Pb(II) in the presence of Cd(II) was over 450. The relative selectivity (α _r) values of Pb(II)/Cd(II) were 49.3 and 46.3, which were greater than 1. The distribution ratio (D) values of Pb(II)-imprinted polymers for Pb(II) were much larger than that for Cd(II). The detection limit (3σ) was 0.20 μg L^?1. The relative standard deviation was 2.0% for 11 replicate determinations. The method was validated for the analysis three certified reference materials (GBW 08301, GBW 08504, GBW 08511), and the results are in good agreement with standard values. The method was also successfully applied to the determination of trace lead in plants and water samples with satisfactory results.     

A magnetic metal-organic framework as a new sorbent for solid-phase extraction of copper(II), and its determination by electrothermal AAS

We report on the synthesis of Fe₃O₄-functionalized metal-organic framework (m-MOF) composite from Zn(II) and 2-aminoterephthalic acid by a hydrothermal reaction. The magnetic composite is iso-reticular and was characterized by FTIR, X-ray diffraction, SEM, magnetization, and TGA. The m-MOF was then applied as a sorbent for the solid-phase extraction of trace levels of copper ions with subsequent quantification by electrothermal AAS. The amount of sorbent applied, the pH of the sample solution, extraction time, eluent concentration and volume, and desorption time were optimized. Under the optimum conditions, the enrichment factor is 50, and the sorption capacity of the material is 2.4 mg g^?1. The calibration plot is linear over the 0.1 to 10 μg L^?1 Cu(II) concentration range, the relative standard deviation is 0.4 % at a level of 0.1 μg L^?1 (for n?=?10), and the detection limit is as low as 73 ng L^?1. We consider this magnetic MOF composite to be a promising and highly efficient material for the preconcentration of metal ions.

Separation and preconcentration of trace quantities of copper ion using modified alumina nanoparticles, and its determination by flame atomic absorption spectrometry

We report on a sensitive, reliable and relatively fast method for separation, preconcentration and determination of trace quantities of copper(II) ion. It is making use of nanometer-sized γ-alumina nanoparticles modified with sodium dodecyl sulfate (SDS). The adsorptive potential was assessed via a Langmuir isotherm and the maximal sorption capacity was found to be 138 mg g^-1. The effects of pH values, amount of ligand, flow rate, type of eluting agent, volume of eluent, and the volume of sample were examined. The effects of interfering ions on the recovery of the analyte were also investigated. Copper ion was then determined by flame atomic absorption spectrometry. The relative standard deviation for five replicate determinations (at 50 μg L^?1 of copper) is 3.3%. The detection limit (at 3 s) is 2.5 μg L^?1. This method was validated with a certified reference material of oyster tissue (NIST SRM 1566b) and the results coincided well with the certified values. The procedure was successfully applied to the determination of Cu in water and food samples.

Magnetic dispersive solid phase extraction using modified magnetic multi-walled carbon nanotubes combined with electrothermal atomic absorption spectrometry for the determination of selenium

A novel magnetic dispersive solid phase extraction method using magnetic multi-walled carbon nanotubes modified with 5-mercapto-3-phenyl-1,3,4-thiadiazole-2-thione potassium salt (bismuthiol II) (MMWCNTs@Bis) as the sorbent was developed for the separation and preconcentration of inorganic selenium (IV) prior to its determination by electrothermal atomic absorption spectrometry. The prepared MMWCNTs@Bis sorbent was characterised by Fourier transform infrared spectroscopy, scanning electron microscopy, vibrating sample magnetometer and X-ray diffraction. Total selenium was determined after reduction of Se(VI) to Se(IV) by addition of hydrochloric acid and heating the mixture in a boiling water bath. Se(VI) concentration was determined from the difference between the amounts of total selenium and Se(IV). Under the optimised experimental conditions, an enhancement factor of 196 and a detection limit (based on 3S_b/m) of 0.003 µg L^?1 was obtained for aqueous samples. The relative standard deviation at 0.1 µg L^?1 concentration level of Se(IV) (n = 6) was found to be 5.2 and 7.7% for intra- and inter-day analysis, respectively. The method was successfully applied to the determination of inorganic selenium species in water and total selenium in food samples.     

Stripping voltammetry method for determination of manganese as complex with oxine at the carbon paste electrode with and without modification with montmorillonite clay

Oxine (8-hydroxyquinoline) was used as an efficient and selective ligand for stripping voltammetry trace determination of Mn(II). A validated square-wave adsorptive cathodic stripping voltammetry method has been developed for determination of Mn(II) selectively as oxine complex using both the bare carbon paste electrode (CPE) and the modified CPE with 7 % (w/w) montmorillonite-Na clay. Modification of carbon paste with montmorillonite clay was found to greatly enhance its adsorption capacity. Limits of detection of 45 ng l^?1 (8.19?×?10^?10 mol L^?1) and 1.8 ng l^?1 (3.28?×?10^?11 mol L^?1) Mn(II) were achieved using the bare and modified CP electrodes, respectively. The achieved limits of detection of Mn(II) as oxine complex using the modified CPE are much sensitive than the detection limits obtained by most of the reported electrochemical methods. The developed stripping voltammetry method using both electrodes was successfully applied for trace determination of Mn(II) in various water samples without interferences from various organic and inorganic species.     

Multi-wall carbon nanotubes chemically modified silica microcolumn preconcentration/separation combined with inductively coupled plasma optical emission spectrometry for the determination of trace elements in environmental waters

A novel adsorbent of multi-wall carbon nanotubes (MWCNTs) chemically modified silica (MWCNTs-silica) was synthesised and employed as the adsorbent material for solid-phase extraction (SPE) of trace Zn(II), Cu(II), Cd(II), Cr(III), V(V) and As(V) in environmental water samples followed by inductively coupled plasma optical emission spectrometry detection. This material inherits the advantages of nanomaterial MWCNTs and conventional silica with dual functional groups (–NH₂ and –COOH), and avoid the problem of nanomaterial in SPE, such as high pressure. The factors affecting the separation and preconcentration of target elements such as pH, sample flow rate and volume, eluent concentration and volume were investigated. Under the optimised conditions, the detection limits for Zn(II), Cu(II), Cd(II), Cr(III), V(V) and As(V) were 0.27, 0.11, 0.45, 0.91, 0.55 and 0.67 μg L^?1 with the relative standard deviations of 3.1, 5.9, 4.1, 4.0, 7.3 and 8.6% (c = 10 μg L^?1, n = 7), respectively. The adsorption capacity of MWCNTs-silica was 26.6, 70.0, 13.8, 58.0, 20.0 and 20.0 mg g^?1 for Zn(II), Cu(II), Cd(II), Cr(III), V(V) and As(V), respectively, and the prepared adsorbent could be reused more than 100 times. In order to validate the developed method, two certified reference materials of GSBZ50009-88 and GSBZ 50029-94 environmental waters were analysed and the determined values were in good agreement with the certified values. The developed method has been applied to the determination of trace elements in environmental water samples with satisfactory results.     

Simultaneous preconcentration and determination of nickel and cobalt using functionalised mesoporous silica spheres by ICP-OES

In this work functionalised mesoporous silica spheres have been utilised for the simultaneous preconcentration of nickel and cobalt. The silica spheres (SiSPs) prepared by the sol-gel method were functionalised with sodium diethyldithiocarbamate (DDTC-SiSPs). They were characterised by SEM, TEM, XRD, FTIR, CHN and nitrogen adsorption. The adsorption efficiency of DDTC-SiSPs was examined by batch equilibrium technique. The DDTC-SiSPs showed 100% adsorption for Ni (II) and Co (II). The effect of changing variables such as pH, shaking time, sample volume, preconcentration factor, eluent type and volume were investigated so as to obtain maximum recovery with high selectivity over interfering ions. The maximum adsorption capacity was found to be 15.15 mg g^?1 and 11.80 mg g^?1 for Ni (II) and Co (II) respectively using DDTC-SiSPs. 100% recovery was achieved with 5 mL of 2 M HNO₃. The maximum preconcentration factor was 400 and the 3σ limits of detection were 0.201 µg L^?1 and 0.198 µg L^?1 for Ni (II) and Co (II) respectively. Thermodynamic studies showed that adsorption of Ni (II) and Co (II) on DDTC-SiSPs is exothermic with enthalpy changes of –0.514 KJ mol^?1 and –0.854 KJ mol^?1 for Ni (II) and Co (II) respectively. The method was applied to the preconcentration and determination of Ni (II) and Co (II) from tap, river and sea water.     

Preconcentration and determination of low amounts of cobalt in black tea,paprika and marjoram using dispersive liquid–liquid microextraction and flame atomic absorption spectrometry

A dispersive liquid–liquid microextraction (DLLME) method for separation/preconcentration of ultra trace amounts of Co(II) and its determination with FAAS was developed. The DLLME behavior of Co(II) using Aliquat 336-chloride as ion pairing agent was systematically investigated. The factors influencing the ion pair formation and extraction by DLLME method were optimized. Under the optimized conditions for 150 µL of extraction solvent (carbon tetrachloride), 1.5 mL disperser solvent (acetonitrile) and 5 mL of sample, the enrichment factor was 30. The detection limit was 5.6 µg L^?1 and the RSD for replicate measurements of 1 mg L^?1 was 1.32 %. The calibration graph using the preconcentration system for cobalt was linear from 40 to 400 µg L^?1 with a correlation coefficient of 0.999. The proposed method was successfully applied for determination of cobalt in black tea, paprika and marjoram real samples.     

Application of stripping voltammetry method for the analysis of available copper,zinc and manganese contents in soil samples

Determination of copper (Cu), zinc (Zn) and manganese (Mn) micronutrients in soil samples have been studied for an efficient fertiliser application. Plant-available micronutrients of soils were extracted with DTPA extraction procedure, then differential pulse stripping voltammetry (DPSV) and square wave stripping voltammetry (SWSV) methods were performed with inexpensive and disposable pencil graphite electrode for determination of Cu(II), Zn(II) and Mn(II). Parameters such as deposition potential, deposition time, pH and concentration of the supporting electrolyte were optimised for these ions. Under optimised conditions, the limits of detection were found as 0.01 mg L^?1 for Cu(II) and 0.02 mg L^?1 for Zn(II) and 0.25 mg L^?1 for Mn(II). Relative standard deviation (%RSD) was 6.80, 8.86 and 3.29 for Cu(II), Zn(II) and Mn(II), respectively. The experimental study was conducted using a flame atomic absorption spectroscopy. The described stripping voltammetry methods were successfully applied for the determination of Mn(II), Cu(II) and Zn(II) in soil samples.