Limits...
On-line micro column preconcentration system based on amino bimodal mesoporous silica nanoparticles as a novel adsorbent for removal and speciation of chromium (III, VI) in environmental samples.

Shirkhanloo H, Khaligh A, Golbabaei F, Sadeghi Z, Vahid A, Rashidi A - J Environ Health Sci Eng (2015)

Bottom Line: TEM, XRD, and SEM results confirmed the beneficial properties of NH2-UVM-7 as the adsorbent for chromium extraction.The efficiency of nanoadsorbent for preconcentration and extraction of Cr (VI) was 96 %, whereas it was less than 5 % for Cr (III).Good recoveries, with low detection limits and good preconcentration factors are the main advantages of this procedure.

View Article: PubMed Central - PubMed

Affiliation: Occupational and Environmental Health Research Center (OEHRC), Iranian Petroleum Industry Health Research Institute (IPIHRI-PIHO), Tehran, 1485733111 Iran ; Research Institute of Petroleum Industry (RIPI), Tehran, 14665-1137 Iran.

ABSTRACT

Background: Chromium (VI) has toxic and carcinogenic effects. So, determination and speciation of chromium in environmental samples is very important in view of health hazards. In this study, solid phase extraction (SPE) based on bulky amine-functionalized bimodal mesoporous silica nanoparticles (NH2-UVM-7) as a novel nanoadsorbent was applied for preconcentration and speciation of chromium (III, VI) in water samples.

Methods: UVM-7 was synthesized via atrane route and subsequently functionalized with amino silane via grafting method. In SPE procedure, polymer tubing as a micro-column was filled with NH2-UVM-7 adsorbent. Preconcentration and speciation of Cr (III) and Cr (VI) ions with NH2-UVM-7 were obtained in water samples due to the fact that only Cr (VI) ions can be complexed with-NH2 groups at optimized pH. Finally, chromium concentration was determined by flame atomic absorption spectrometry (F-AAS).

Results: TEM, XRD, and SEM results confirmed the beneficial properties of NH2-UVM-7 as the adsorbent for chromium extraction. Under the optimal conditions, linear calibration curve, detection limit and preconcentration factor were obtained 6-320 μg/ L, 1.2 μg/L and 66.7, respectively (RSD < 5 %). The efficiency of nanoadsorbent for preconcentration and extraction of Cr (VI) was 96 %, whereas it was less than 5 % for Cr (III).

Conclusions: The developed NH2-UVM7-based SPE/F-AAS method has enough sensitively and simplicity for speciation and determination of Cr (VI) and Cr (III) ions in real water samples. Good recoveries, with low detection limits and good preconcentration factors are the main advantages of this procedure.

No MeSH data available.


Related in: MedlinePlus

The influence of solution pH on the recovery of Cr (VI) (▲) and Cr (III) (■) ions with NH2-UVM-7 (▲). Conditions: sample volume 100 mL; adsorbent amount 0.12 g; eluent 1.5 mL of 0.3 mol/L NaOH; sample flow rate 2.5 mL/min
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC4940767&req=5

Fig5: The influence of solution pH on the recovery of Cr (VI) (▲) and Cr (III) (■) ions with NH2-UVM-7 (▲). Conditions: sample volume 100 mL; adsorbent amount 0.12 g; eluent 1.5 mL of 0.3 mol/L NaOH; sample flow rate 2.5 mL/min

Mentions: In the SPE studies, the pH of the sample solution is an important parameter to obtain quantitative recoveries of metal ions, because it affects the surface charge of the adsorbent, the degree of ionization and speciation of the adsorbate. The influence of sample pH on speciation and recovery efficiency of Cr (VI)/Cr (III) ions by NH2-UVM-7 was investigated at different pH values (1-10) by using buffered sample solutions containing Cr (III) and Cr (VI) ions, according to the general procedure. The complexation was strongly conditioned by the pH of solutions and subsequently affects extraction efficiency of the complex. As shown in Fig. 5, the highest extraction efficiency (>97 %) for Cr (VI) was achieved in the pH range of 1 -3.2, whereas the recovery values for Cr (III) were below 5 % in the same pH. Thus, the procedure was applied to speciation of Cr (VI)/Cr (III) ions at pH = 2. For higher pH values (pH > 3), the recovery percentages of Cr (VI) ions decreased with increase in pH. The extraction mechanism of Cr (VI) ions on the NH2-UVM-7 may be based on the electrostatic attractions between metals ions and NH2 groups of nanoadsorbent, which is highly dependent on solution pH. The NH2 groups on the surface of the NH2-UVM-7 can either be protonated (-NH3+) at low pH or be deprotonated (NH−) at high pH. The variation in adsorption capacity of Cr (VI) at different pH values may be attributed to the affinities of NH2-UVM-7 nanoadsorbent for the different anionic species of Cr (VI) existing at acidic pH conditions namely HCrO4−, CrO42− and Cr2O72−. It is clear that negatively charged HCrO4− and Cr2O72− are easily adsorbed to the positively charged NH3+ at low pH values due to the electronic attraction. By using UVM-7 as the SPE adsorbent for preconcentration of Cr (IV) ions, it was observed that the extraction efficiencies were less than 5 % in the studied pH range. This is because the physical adsorption of Cr (VI) ions by unmodified UVM-7 is the main mechanism. So, the NH2-UVM7 is favorite adsorbent for speciation and determination of Cr (VI)/Cr (III) ions in water samples by SPE method and can be used for on-line removal Cr (VI) in water samples at pH = 2.Fig. 5


On-line micro column preconcentration system based on amino bimodal mesoporous silica nanoparticles as a novel adsorbent for removal and speciation of chromium (III, VI) in environmental samples.

Shirkhanloo H, Khaligh A, Golbabaei F, Sadeghi Z, Vahid A, Rashidi A - J Environ Health Sci Eng (2015)

The influence of solution pH on the recovery of Cr (VI) (▲) and Cr (III) (■) ions with NH2-UVM-7 (▲). Conditions: sample volume 100 mL; adsorbent amount 0.12 g; eluent 1.5 mL of 0.3 mol/L NaOH; sample flow rate 2.5 mL/min
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4940767&req=5

Fig5: The influence of solution pH on the recovery of Cr (VI) (▲) and Cr (III) (■) ions with NH2-UVM-7 (▲). Conditions: sample volume 100 mL; adsorbent amount 0.12 g; eluent 1.5 mL of 0.3 mol/L NaOH; sample flow rate 2.5 mL/min
Mentions: In the SPE studies, the pH of the sample solution is an important parameter to obtain quantitative recoveries of metal ions, because it affects the surface charge of the adsorbent, the degree of ionization and speciation of the adsorbate. The influence of sample pH on speciation and recovery efficiency of Cr (VI)/Cr (III) ions by NH2-UVM-7 was investigated at different pH values (1-10) by using buffered sample solutions containing Cr (III) and Cr (VI) ions, according to the general procedure. The complexation was strongly conditioned by the pH of solutions and subsequently affects extraction efficiency of the complex. As shown in Fig. 5, the highest extraction efficiency (>97 %) for Cr (VI) was achieved in the pH range of 1 -3.2, whereas the recovery values for Cr (III) were below 5 % in the same pH. Thus, the procedure was applied to speciation of Cr (VI)/Cr (III) ions at pH = 2. For higher pH values (pH > 3), the recovery percentages of Cr (VI) ions decreased with increase in pH. The extraction mechanism of Cr (VI) ions on the NH2-UVM-7 may be based on the electrostatic attractions between metals ions and NH2 groups of nanoadsorbent, which is highly dependent on solution pH. The NH2 groups on the surface of the NH2-UVM-7 can either be protonated (-NH3+) at low pH or be deprotonated (NH−) at high pH. The variation in adsorption capacity of Cr (VI) at different pH values may be attributed to the affinities of NH2-UVM-7 nanoadsorbent for the different anionic species of Cr (VI) existing at acidic pH conditions namely HCrO4−, CrO42− and Cr2O72−. It is clear that negatively charged HCrO4− and Cr2O72− are easily adsorbed to the positively charged NH3+ at low pH values due to the electronic attraction. By using UVM-7 as the SPE adsorbent for preconcentration of Cr (IV) ions, it was observed that the extraction efficiencies were less than 5 % in the studied pH range. This is because the physical adsorption of Cr (VI) ions by unmodified UVM-7 is the main mechanism. So, the NH2-UVM7 is favorite adsorbent for speciation and determination of Cr (VI)/Cr (III) ions in water samples by SPE method and can be used for on-line removal Cr (VI) in water samples at pH = 2.Fig. 5

Bottom Line: TEM, XRD, and SEM results confirmed the beneficial properties of NH2-UVM-7 as the adsorbent for chromium extraction.The efficiency of nanoadsorbent for preconcentration and extraction of Cr (VI) was 96 %, whereas it was less than 5 % for Cr (III).Good recoveries, with low detection limits and good preconcentration factors are the main advantages of this procedure.

View Article: PubMed Central - PubMed

Affiliation: Occupational and Environmental Health Research Center (OEHRC), Iranian Petroleum Industry Health Research Institute (IPIHRI-PIHO), Tehran, 1485733111 Iran ; Research Institute of Petroleum Industry (RIPI), Tehran, 14665-1137 Iran.

ABSTRACT

Background: Chromium (VI) has toxic and carcinogenic effects. So, determination and speciation of chromium in environmental samples is very important in view of health hazards. In this study, solid phase extraction (SPE) based on bulky amine-functionalized bimodal mesoporous silica nanoparticles (NH2-UVM-7) as a novel nanoadsorbent was applied for preconcentration and speciation of chromium (III, VI) in water samples.

Methods: UVM-7 was synthesized via atrane route and subsequently functionalized with amino silane via grafting method. In SPE procedure, polymer tubing as a micro-column was filled with NH2-UVM-7 adsorbent. Preconcentration and speciation of Cr (III) and Cr (VI) ions with NH2-UVM-7 were obtained in water samples due to the fact that only Cr (VI) ions can be complexed with-NH2 groups at optimized pH. Finally, chromium concentration was determined by flame atomic absorption spectrometry (F-AAS).

Results: TEM, XRD, and SEM results confirmed the beneficial properties of NH2-UVM-7 as the adsorbent for chromium extraction. Under the optimal conditions, linear calibration curve, detection limit and preconcentration factor were obtained 6-320 μg/ L, 1.2 μg/L and 66.7, respectively (RSD < 5 %). The efficiency of nanoadsorbent for preconcentration and extraction of Cr (VI) was 96 %, whereas it was less than 5 % for Cr (III).

Conclusions: The developed NH2-UVM7-based SPE/F-AAS method has enough sensitively and simplicity for speciation and determination of Cr (VI) and Cr (III) ions in real water samples. Good recoveries, with low detection limits and good preconcentration factors are the main advantages of this procedure.

No MeSH data available.


Related in: MedlinePlus