Rare earth metal incorporated zeolite modified electrodes for detection and quantification of heavy metal ions in aqueous solution

Patent metadata

Field	Value
Publication number	US-10495601-B2
Application number	US-201715446035-A
Country	US
Kind code	B2
Filing date	Mar 1, 2017
Priority date	May 2, 2016
Publication date	Dec 3, 2019
Grant date	Dec 3, 2019

Abstract

Electrodes comprising conducting graphite, paraffin oil pasting liquid, and a rare earth metal impregnated zeolite, such as lanthanum or cerium impregnated mordenite electrodes. Methods and voltammetric applications, such as square wave anodic stripping voltammetry, of these rare earth metal impregnated zeolite modified electrodes for the detection and quantification of heavy metal ions such as Pb(II) and Cd(II) in aqueous solutions.

First claim

The invention claimed is:

1. An electrode, comprising:
graphite powder;
paraffin oil; and
a mordenite zeolite impregnated with a rare earth metal;
wherein the rare earth metal is at least one selected from the group consisting of lanthanum and cerium; and
wherein the mordenite zeolite impregnated with the rare earth metal is present in an amount of 4-5% by weight relative to a total weight of the electrode.

2. The electrode of claim 1 , wherein the mordenite zeolite has a silica to alumina ratio in the range of 5 to 40.

3. The electrode of claim 1 , wherein the rare earth metal is lanthanum.

4. The electrode of claim 1 , wherein the mordenite zeolite impregnated with the rare earth metal has a weight percentage of the rare earth metal in the range of 1-15% relative to the total weight of the mordenite zeolite impregnated with the rare earth metal.

5. The electrode of claim 1 , which has a weight percentage of the graphite powder in the range of 60 to 70% relative to the total weight of the electrode.

6. The electrode of claim 1 , which has a weight percentage of the paraffin oil in the range of 26-34% relative to the total weight of the electrode.

7. The electrode of claim 1 , which has a 10-40% greater electroactive surface area relative to an identical electrode except that it contains a zeolite which is not impregnated with the rare earth metal.

8. A method for detecting and quantifying a heavy metal ion in an aqueous solution, comprising:
contacting the aqueous solution with the electrode of claim 1 ;
generating a negative deposition potential at the electrode to reduce the heavy metal ion and form a reduced heavy metal that is deposited onto the electrode;
scanning a potential range from the negative deposition potential in the positive direction at the electrode to oxidize and strip the reduced heavy metal from the electrode; and
measuring the current during the scanning.

9. The method of claim 8 , wherein the heavy metal ion is at least one selected from the group consisting of Pb(II) and Cd(II).

10. The method of claim 8 , wherein the scanning and the measuring are performed with square wave voltammetry.

11. The method of claim 8 , wherein the negative deposition potential is in the range of −2.0 V to −0.2 V.

12. The method of claim 8 , wherein the scanning is performed at a scan rate of 2-500 mV s −1 .

13. The method of claim 8 , wherein the reduced heavy metal is deposited over a time period in the range of 10-250 seconds.

14. The method of claim 8 , wherein the aqueous solution has a pH in the range of 3-5.

15. The method of claim 8 , wherein the rare earth metal is lanthanum and the heavy metal ion is Pb(II), and the method has a Pb(II) detection limit in the range of 0.15-0.30 μg L −1 .

16. The method of claim 8 , wherein the rare earth metal is lanthanum and the heavy metal ion is Cd(II), and the method has a Cd(II) detection limit in the range of 0.05-0.20 μg L −1 .

17. The method of claim 8 , wherein the rare earth metal is cerium and the heavy metal ion is Pb(II), and the method has a Pb(II) detection limit in the range of 0.02-0.15 μg L −1 .

18. The method of claim 8 , wherein the rare earth metal is cerium and the heavy metal ion is Cd(II), and the method has a Cd(II) detection limit in the range of 0.01-0.10 μg L −1 .

19. The method of claim 8 , which has a reproducibility as measured by a relative standard deviation in the range of 1-5%.

20. The electrode of claim 1 , wherein the rare earth metal is lanthanum and wherein a weight percentage of lanthanum is 1.5-5% relative to the total weight of the mordenite zeolite impregnated with the rare earth metal.

Assignees

• Univ King Fahd Pet & Minerals

Inventors

• Abdulazeez Ismail
• Kawde Abdel-Naser M
• Muraza Oki
• Al-Betar Abdul-Rahman

Classifications

• G01N27/48

  using polarography, i.e. measuring changes in current under a slowly-varying voltage · CPC title

• G01N27/308

  at least partially made of carbon · CPC title

• G01N27/333 Primary

  Ion-selective electrodes or membranes (glass electrodes G01N27/36) · CPC title

• G01N27/3277

  being a redox reaction, e.g. detection by cyclic voltammetry (voltammetry per se G01N27/42, G01N27/48) · CPC title