Elsevier

Chemical Physics Letters

Volume 759, 16 November 2020, 137930
Chemical Physics Letters

Research paper
pH-dependent electrodeposition reaction of 2-phenoxyethanol in aqueous environment and adsorption of phenols on modified surfaces

https://doi.org/10.1016/j.cplett.2020.137930Get rights and content

Highlights

  • 2-phenoxyethanol electropolymerization mechanism is different at different pHs.

  • Glassy carbon deactivates much faster than platinum.

  • In basic solutions surface activation of glassy carbon takes place.

  • Some phenols adsorb readily on the modified glassy carbon.

Abstract

In this report the electrooxidation of 2-phenoxyethanol was studied in acidic, neutral and basic aqueous solutions (pH = 1, 7, 13) on platinum and glassy carbon electrodes. The glassy carbon electrode was fouled quickly in acidic solutions of 2-phenoxyethanol but this effect was less significant in neutral conditions. In basic electrolyte solution (pH = 13) the voltammetric peak current increased continuously. This tendency was also observed on platinum electrode with increasing pH a little but weak fouling effect was observed. The modified glassy carbon electrode proved to be appropriate for adsorption of phenols from aqueous solutions.

Introduction

2-phenoxyethanol is a phenylether which can be oxidized on its phenoxyl moiety. It is well known that the electropolymerisation rate of phenols increases during changing the pH of the solutions from acidic to basic. At higher pHs the phenolic hydroxy group is deprotonated and the electropolymerisation is facilitated [1]. The most frequently used electrodes in electrochemistry like platinum and glassy carbon foul quickly in aqueous solutions of majority of phenols [2], [3]. According to the literature numerous studies were carried out in nonaqueous solvents, among them only a few report the electrochemistry of phenylethers in water and in liquids containing water [4], [5]. The results obtained in case of carbon-based electrodes generally differ according to the surface state and pretreatment. In this report the results concerning pH-dependent behaviour of 2-phenoxyethanol are shown using platinum and glassy carbon electrodes.

Phenols are toxic materials that might be released through industrial wastewater into the environment. That is why their degradation is studied extensively. Adsorption of phenols is also studied in many works with various adsorbents. A vast number of carbon based materials seemed appropriate for the adsorptive extraction of phenolic compounds from wastewaters. Ordered mesoporous carbon doped with zirconium and nitrogen [6], doping of other carbon based materials with nitrogen [7], graphene doped with nitrogen [8] were found to be very efficient adsorbents. Porous polyvinyl alcohol membrane doped with 1-arginine for 4-nitrophenol [9], cyclodextrin hydrogel for phenol [10], CO2-activated pyrolysis tyre powder for phenol [11] proved also very efficient. A Dowex ion exchange resin elevated the coadsorption of Cr(VI) ions and phenol [12]. Biopolymers are useful for sorption of phenol and nitrophenols [13], and algae especially Ulva lactuca Alga has high affinity towards many phenols [14]. Carbon based adsorbents with special surface properties collect readily phenol from the gas phase [15]. Binding to solid surfaces through weak interactions facilitates their collection so it is examined in one part of this paper at as-modified solid surfaces.

Section snippets

Experimental

The chemicals were analytical grade and used as received. Disc shaped working electrodes (platinum and glassy carbon) were obtained from eDAQ with 1 mm diameter. The surfaces of electrodes were polished with a polishing cloth by using an aqueous suspension of 0.05 μm alumina powder. After thorough washing with deionized water they were used in the studied solutions applying a platinum rod as counter electrode, while standard calomel reference electrode was filled with 1 M KCl. All three

Electrodeposition of 2-phenoxyethanol from different pH aqueous solutions

In order to investigate the electrochemical behaviour of 2-phenoxyethanol in solutions with different pHs repetitive cyclic voltammograms were taken both with glassy carbon and platinum electrode. The solution with pH = 1 was prepared by dissolving nitric acid in deionized water. The pH = 7 solution was ensured with 0.1 mol/L phosphate buffer while the solution with pH = 13 was adjusted with sodium hydroxide. The solutes applied to set the pH served also as supporting electrolyte. The solutions

Conclusion

The electrochemical behaviour of 2-phenoxyethanol was studied in different pH solutions and those properties was found to be pH-dependent using glassy carbon electrode. The modified glassy carbon electrode through electrochemical activation and electrodeposition of substrate proved to be appropriate for adsorption of phenols. This is an easy way for making surfaces efficient in adsorption of organic compounds. The reported surface modification is relatively cheap and glassy carbon surface can

CRediT authorship contribution statement

László Kiss: Conceptualization, Investigation, Writing - original draft. Sándor Kunsági-Máté: Writing - review & editing.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

Financial support of the GINOP 2.3.2-15-2016-00022 is highly appreciated.

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