Graphene oxide (GO) has an excellent adsorption capacity toward metal ions. Therefore, it is wide... more Graphene oxide (GO) has an excellent adsorption capacity toward metal ions. Therefore, it is widely recognized as an auspicious material for fabrication of membranes applied in metal ions separation. However, the GO membranes are not stable in aqueous solution, due to the electrostatic repulsion between the GO nanosheets which are negatively charged. This paper shows that stable GO membranes can be easily obtained by the noncovalent interaction of GO with oxidized carbon nanotubes (CNTs). The experiment shows also that the GO/CNTs membranes can be used for the effective adsorption of metal ions. The kinetic data, adsorption isotherms, competitive adsorption experiment and X-ray photoelectron spectroscopy indicate that the adsorption of metal ions is based on chemisorption. The membranes are remarkably durable in acidic, neutral and basic solutions. Although, the significant stabilization of the membranes by CNTs is observed, they strongly influence the adsorption process. Our study reveals that even small amount of CNTs (GO/CNTs in ratio 8:1) significantly reduces adsorption capacities of the membranes which were: 37, 40, 50, 42, 48, 98 mg g-1 for Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II), respectively. The reduction of the membranes adsorption capacities results from the creation of micro- and nano-channels formed by entangled CNTs. Durability and adsorptive properties of studied membranes indicate their potential use for the removal of metals from water.
An ultrasound-assisted methodology for the determination of dissolved silicate in water has been ... more An ultrasound-assisted methodology for the determination of dissolved silicate in water has been developed by combining the miniaturized ion-associated based preconcentration method with energy dispersive X-ray fluorescence spectrometry (EDXRF). The method has been devised for the determination of silicate through molybdenum in the ion-associated complex between 12-molybdosilicate and crystal violet. Because silicate is determined indirectly via molybdenum fluorescent radiation the difficulties resulting from low fluorescence yield and low energy of silicon radiation were successfully overcome. A good ratio of silicon to molybdenum (1 to 41) and a sensitive Kα line of molybdenum make possible the determination of low concentration of silicon in the form of dissolved silicate. Under optimized conditions, good linearity, up to 5 μg of silicon in the form of silicate (r = 0.9990) and a detection limit of 9 ng mL(-1) were achieved. The total RSD for the EDXRF determination of silicate, followed by precipitation of the ion-associated complex and its dissolution in a microdrop of isoamyl alcohol, was 6.5%. The enrichment factor was equal to 142. The developed method was used to determine the dissolved silica content in surface waters. The accuracy and repeatability of the proposed procedure were checked by the standard addition method and compared to the results obtained using the ICP-OES technique. The recovery (in the 93-97% range) was satisfactory and indicated the usefulness of the developed procedure.
ABSTRACT A new method for sample preparation using graphene oxide (GO) as a novel sorbent was dev... more ABSTRACT A new method for sample preparation using graphene oxide (GO) as a novel sorbent was developed for the preconcentration of trace amounts of Co(II), Ni(II), Cu(II), Zn(II) and Pb(II). The proposed preconcentration procedure is based on dispersive micro-solid phase extraction (DMSPE). It means that GO was dispersed in aqueous samples containing trace elements to be determined. During the stirring of the analyte solution containing the GO suspension, metal ions were sorbed by GO. After the sorption, the solution was filtered under vacuum and GO with the metal ions was collected onto a membrane filter. The obtained samples were analyzed directly by energy-dispersive X-ray fluorescence spectrometry (EDXRF). The parameters affecting the extraction and preconcentration process were optimized. The pH of the analyte solution, the amount of GO, the sample volume, the contact time between analytes and sorbent (stirring time), and the effects of foreign metals are discussed in detail in this paper. The proposed procedure allows us to obtain the detection limits of 0.5, 0.7, 1.5, 1.8 and 1.4 ng mL−1 for Co(II), Ni(II), Cu(II), Zn(II) and Pb(II), respectively. The linearity of the method is in the range of 5-100 ng mL−1. The proposed method was successfully applied in the analysis of water. The accuracy of the method was verified using spiked samples and inductively coupled plasma optical emission spectrometry (ICP-OES) as a comparative technique. The recoveries over the range of 94-106% were obtained. This paper shows the great potential of GO as an excellent sorbent in the preconcentration field of analytical chemistry. The proposed method meets green chemistry rules.
ABSTRACT This article gives an overview of the state-of-the-art of recent preconcentration strate... more ABSTRACT This article gives an overview of the state-of-the-art of recent preconcentration strategies published in X-ray fluorescence spectrometry (XRF), including the use of microextraction procedures, nanomaterials, filters and activated thin layers. We give special attention to current XRF instrumentation and the advantages and the limitations of each mode (including large-scale instrumentation, bench-top spectrometers and hand-held systems). Also, we comment on and discuss trends and future perspectives of XRF spectrometry in trace and ultratrace analysis of liquid samples.
In this paper, graphene oxide/cellulose membranes were prepared in order to perform effective ads... more In this paper, graphene oxide/cellulose membranes were prepared in order to perform effective adsorption of heavy metal ions: cobalt, nickel, copper, zinc, cadmium and lead.
Graphene oxide (GO) has an excellent adsorption capacity toward metal ions. Therefore, it is wide... more Graphene oxide (GO) has an excellent adsorption capacity toward metal ions. Therefore, it is widely recognized as an auspicious material for fabrication of membranes applied in metal ions separation. However, the GO membranes are not stable in aqueous solution, due to the electrostatic repulsion between the GO nanosheets which are negatively charged. This paper shows that stable GO membranes can be easily obtained by the noncovalent interaction of GO with oxidized carbon nanotubes (CNTs). The experiment shows also that the GO/CNTs membranes can be used for the effective adsorption of metal ions. The kinetic data, adsorption isotherms, competitive adsorption experiment and X-ray photoelectron spectroscopy indicate that the adsorption of metal ions is based on chemisorption. The membranes are remarkably durable in acidic, neutral and basic solutions. Although, the significant stabilization of the membranes by CNTs is observed, they strongly influence the adsorption process. Our study reveals that even small amount of CNTs (GO/CNTs in ratio 8:1) significantly reduces adsorption capacities of the membranes which were: 37, 40, 50, 42, 48, 98 mg g-1 for Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II), respectively. The reduction of the membranes adsorption capacities results from the creation of micro- and nano-channels formed by entangled CNTs. Durability and adsorptive properties of studied membranes indicate their potential use for the removal of metals from water.
An ultrasound-assisted methodology for the determination of dissolved silicate in water has been ... more An ultrasound-assisted methodology for the determination of dissolved silicate in water has been developed by combining the miniaturized ion-associated based preconcentration method with energy dispersive X-ray fluorescence spectrometry (EDXRF). The method has been devised for the determination of silicate through molybdenum in the ion-associated complex between 12-molybdosilicate and crystal violet. Because silicate is determined indirectly via molybdenum fluorescent radiation the difficulties resulting from low fluorescence yield and low energy of silicon radiation were successfully overcome. A good ratio of silicon to molybdenum (1 to 41) and a sensitive Kα line of molybdenum make possible the determination of low concentration of silicon in the form of dissolved silicate. Under optimized conditions, good linearity, up to 5 μg of silicon in the form of silicate (r = 0.9990) and a detection limit of 9 ng mL(-1) were achieved. The total RSD for the EDXRF determination of silicate, followed by precipitation of the ion-associated complex and its dissolution in a microdrop of isoamyl alcohol, was 6.5%. The enrichment factor was equal to 142. The developed method was used to determine the dissolved silica content in surface waters. The accuracy and repeatability of the proposed procedure were checked by the standard addition method and compared to the results obtained using the ICP-OES technique. The recovery (in the 93-97% range) was satisfactory and indicated the usefulness of the developed procedure.
ABSTRACT A new method for sample preparation using graphene oxide (GO) as a novel sorbent was dev... more ABSTRACT A new method for sample preparation using graphene oxide (GO) as a novel sorbent was developed for the preconcentration of trace amounts of Co(II), Ni(II), Cu(II), Zn(II) and Pb(II). The proposed preconcentration procedure is based on dispersive micro-solid phase extraction (DMSPE). It means that GO was dispersed in aqueous samples containing trace elements to be determined. During the stirring of the analyte solution containing the GO suspension, metal ions were sorbed by GO. After the sorption, the solution was filtered under vacuum and GO with the metal ions was collected onto a membrane filter. The obtained samples were analyzed directly by energy-dispersive X-ray fluorescence spectrometry (EDXRF). The parameters affecting the extraction and preconcentration process were optimized. The pH of the analyte solution, the amount of GO, the sample volume, the contact time between analytes and sorbent (stirring time), and the effects of foreign metals are discussed in detail in this paper. The proposed procedure allows us to obtain the detection limits of 0.5, 0.7, 1.5, 1.8 and 1.4 ng mL−1 for Co(II), Ni(II), Cu(II), Zn(II) and Pb(II), respectively. The linearity of the method is in the range of 5-100 ng mL−1. The proposed method was successfully applied in the analysis of water. The accuracy of the method was verified using spiked samples and inductively coupled plasma optical emission spectrometry (ICP-OES) as a comparative technique. The recoveries over the range of 94-106% were obtained. This paper shows the great potential of GO as an excellent sorbent in the preconcentration field of analytical chemistry. The proposed method meets green chemistry rules.
ABSTRACT This article gives an overview of the state-of-the-art of recent preconcentration strate... more ABSTRACT This article gives an overview of the state-of-the-art of recent preconcentration strategies published in X-ray fluorescence spectrometry (XRF), including the use of microextraction procedures, nanomaterials, filters and activated thin layers. We give special attention to current XRF instrumentation and the advantages and the limitations of each mode (including large-scale instrumentation, bench-top spectrometers and hand-held systems). Also, we comment on and discuss trends and future perspectives of XRF spectrometry in trace and ultratrace analysis of liquid samples.
In this paper, graphene oxide/cellulose membranes were prepared in order to perform effective ads... more In this paper, graphene oxide/cellulose membranes were prepared in order to perform effective adsorption of heavy metal ions: cobalt, nickel, copper, zinc, cadmium and lead.
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