In a paper published in the magazine Scientific ReportsZinc ions were detected in marine environments affected by oil pollution, using mercury-free gold nanorods for a square anode stripping voltmeter (SW-ASV).
Contribution of offshore oil platforms to oil pollution
Oil pollution is becoming increasingly important with the rapid development of the offshore petroleum production industry. Marine oil pollution poses a serious threat to the natural balance of the marine ecosystem.
There is an urgent need to provide offshore petroleum installations with accessible analytical tools to address the problem of oil pollution. Wastewater quality can be controlled by monitoring the metal concentration in petroleum production water.
Detection of metal ions in sea water
Electrolytic assays, including peeling voltmeters (SV), are becoming increasingly popular to determine trace concentrations of metals in marine environments because they are inexpensive, accessible and can be performed on-site in saltwater.
Several modifications have been made to reduce the limit of detection (LOD) and improve the accuracy of the peak current signal of the multi-ion sensing.
These analysis techniques have achieved high levels of reliability for the detection of trace metals in a wide variety of sample mixtures.
A word about the current methods of zinc detection
Zinc is among the most common toxic elements in petroleum production wastewater.
Anodic potentiometer (ASV) is an excellent electrochemical analysis technology for the detection of zinc ions in natural waters using different electrode materials and configurations.
SW-ASV technology is the most reproducible method of electrolysis On site studies. Mostly mercury-based electrodes have been used so far because they are highly accurate and efficient in pre-concentrating metals.
The mercury-based electrodes showed remarkable accuracy in detecting zinc ions. Unfortunately, they have significant drawbacks regarding toxicity and interference with organic molecules, especially oil.
What did the researchers do?
The researchers proposed an alternative option for mercury-free electrodes capable of detecting zinc ions in seawater and petroleum mixtures. Gold nanoelectrodes were deposited on both sides of the functionalized PVDF nanofilm in this study.
Gold porous nanoelectrodes are an excellent choice for detecting zinc ions. These gold nano-electrodes have previously been shown to effectively detect lead and mercury in natural waters.
To achieve the desired sensitivity level in marine environments, the gold nanorods should be coupled with an adsorption mechanism for efficient trapping and pre-concentration of zinc ions.
The gold nanorods should also adapt the SW-ASV procedure to increase the window potential and reach the negative oxidation potential of zinc.
Using this technique and SW-ASV detection, PVDF-based gold nanoelectrodes staffed with poly(acrylic acid) were used in this study. The objective was to determine the concentration of zinc ions in synthetic water, deionized water, and production water from an offshore oil platform.
Gold nanoelectrodes operating with PAA and PVDF showed high sensitivity for detection of zinc ions using SW-ASV in brine, deionized and petroleum production waters over a wide range of concentration.
Zinc ions adsorption by PAA was thoroughly examined via XPS and SW-ASV tests and uptake using ion chromatography.
Only about 30 min of adsorption was required to balance zinc ion uptake. Poly(acrylic acid) functions showed strong affinity for zinc ions in deionized water. The peak adsorption capacity of the nano-membrane for zinc ions was found to be 1.21 mol g-1.
The zinc ion pre-concentration rate was greater in the seawater samples, as indicated by the SW-ASV analysis of the real production water samples.
LOD was expected to be 4.2 µg L−1 (ppb), but the uncertainty in this estimate would increase two-fold in moderately acidic production waters due to the shift of the hydrogen peak. However, the presented method still provides sufficient reliability.
This approach will enable On site Detection of zinc in glass containers immediately after sampling of water affected by oil contamination.
After infusion of zinc ions, the application of the proposed electrodes along with SW-ASV monitoring showed a high recovery of zinc in marine waters with oil contamination.
Clochard, M., Oral, OR. , valley, hill, Cavani, or. Castellino, M., Leggero, LM, and Ilan, T.; (2022). Detection of zinc in oiled marine environment by stripping voltmeters using a mercury-free gold nanorod electrode. Scientific Reports, 12. Available at: https://www.nature.com/articles/s41598-022-20067-0