**1. Introduction**

20 Electropolymerization

[23] Deng, J.; Shi, B.; Liao, X., Synthesis and characterization of

[24] Grimmond, B. J.; Rath, N. P.; Corey, J. Y., Enantiopure siloxy-functionalized group 4

dehydropolymerization of PhSiH3. *Organometallics* 2000, 19, (16), 2975-2984. [25] Braunschweig, H.; von Koblinski, C.; Wang, R. M., Synthesis and structure of the first 1 boratitanocenophanes. *European Journal of Inorganic Chemistry* 1999, (1), 69-73. [26] Li, J.-j.; Chen, L.; Sun, J.-l.; Zhou, C.-j.; Zhang, J.-b.; Ren, M.-s., Cross-linking and

[27] Lamouroux, F.; Bourrat, X.; Naslain, R.; Thebault, J., Silicon-carbide infiltration of

[28] Fan, X.-q.; Chen, L.; Wu, S.; Zhang, F.-j.; Zhang, J.-b.; Ren, M.-s.; Sun, J.-l., Crosslinking

*Shanghai Daxue Xuebao, Ziran Kexueban* 2004, 10, (5), 479-483.

(6), 1-5.

525-535.

*Xuebao* 2006, 24, (6), 920-922.

polymethylcyclopentadienylsilane and its copolysilane. *Youjigui Cailiao* 2001, 15,

metallocene dichlorides. Synthesis, characterization, and catalytic

pyrolysis of polycarbosilane/divinylbenzene and polysilane/divinylbenzene.

porous C-C composites for improving oxidation resistance. *Carbon* 1995, 33, (4),

and pyrolysis of polymethylsilane/divinylbenzene. *Cailiao Kexue Yu Gongcheng* 

One of the promising methods for waste water remediation is The electrochemical oxidation of hazardous organic species [Fleszar & Jolanta, *1985;* Comninellis, 1994]. Phenols due to their slow degradation, bioaccumulation and toxicity constitute a large group of organic pollutants. The quantitation of phenolic compounds in environmental, industrial and food samples is currently of great interest, which can be found in soils and groundwater [Wang et al., 1998]. Also, these compounds are important synthesis intermediates in chemical industry such as resins, preservatives, pesticides, etc. Another, the main sources of phenolic waste are in glass fiber insulation manufacture on petroleum refineries. Phenol and substituted phenolic compounds such as catechol, chlorophenol are hydroquinones and discharged in the effluent from a number of chemical process industries. Today, these compounds are found in relatively high amount in domestic and industrial wastewater, discharged mainly from the mechanical industries. Many treatment technologies are in use or have been proposed for phenol recovery or destruction.

The electrooxidation of phenolic compounds can be occurs as follows: in the first step of electrooxidation of phenols, phenoxy radicals are generated, then these species can be either oxidized further or be coupled, forming ether and oligomeric or polymeric compounds [Wang et al ,1991; Iotov, & Kalcheva, 1998]. Electropolymerization of phenol beings with the formation of the phenoxy radical, or it can react with a molecule of phenol to give predominantly a para-linked dimeric radical. This radical may be further oxidized to form a neutral dimmer or it may attach another molecule. The dimer may be further oxidized create oligomers to polymers. Formation of the insoluble polyphenol results in deactivation of electrode surface. The relative rates of the two pathways (polymerization and forming quinonic structure) depend on the phenols concentration, the nature of electrode, pH, solvent, additives, electrode potential and current density [Gattrell & Kirk,1993]. Electropolymerization of phenols occur on different electrodes, such as Fe, Cu, Ni, Ti, Au, Pt

Electropolymerization of Some Ortho-Substituted Phenol Derivatives on Pt-Electrode from

water, double distilled water, rinsed with ethanol and dried.

reversed with the same scan rate up to the starting cathodic potential.

**2.2.1 Electrodes** 

cm width

**2.2.1.1 Working electrode** 

**2.2.1.2 Auxiliary electrode** 

**2.2.1.3 Reference electrode** 

experimental tests to characterize it.

**2.2.2 Procedure** 

remove dissolved oxygen.

Aqueous Acidic Solution; Kinetics, Mechanism, Electrochemical Studies and Characterization of… 23

The working electrode (WE) was a platinum sheet with dimensions of 1cm length and 0.5

The auxiliary (counter) electrode (CE) was a platinum foil with the same dimensions as the WE. Before each run, both the WE and the CE were cleaned and washed thoroughly with

A saturated calomel electrode (SCE) was used as a reference electrode. The values of the electrode potential in the present work are given relative to this electrode. The potential value for the SCE is 0.242 V vs. NHE at 25 oC. SCE was periodically calibrated and checked. Electrochemical experiments were performed using the Potentiostat / Galvanostat Wenking PGS 95. i-E curves were recorded by computer software from the same company (Model ECT). Except otherwise stated, the potential was swept linearly from starting potential into the positive direction up to a certain anodic potential with a given scan rate and then

For each run, freshly prepared solutions as well as a cleaned set of electrodes were used. All experiments were conducted at a given temperature (± 0.5 oC) with the help of circular water thermostat. After polymer film formation, the working electrode was withdrawn from the cell, rinsed thoroughly with a doubly distilled water to remove any traces of the formed constituents in the reaction medium. The deposited polymer film was subjected to different

Potentiodynamic cyclic voltammetry measurements during the formation of the polymer films on the surface of the working electrode was carried out in the electrochemical cell shown in Fig.(1).The cell was filled with the test solution (aqueous solution containing H2SO4 as supporting electrolyte, and monomer). The working and counter electrodes were introduced in the cell. The reference electrode was attached to the cell by U-shaped salt bridge (SB) ended with a fine capillary tip (Luggin –Harber probe)wherein the reference electrode was positioned very closed to the working electrode to minimize the over potential due to electrolyte resistance .The bridge was filled with the test solution. Before and during measurements a current of pure nitrogen gas was bubbled in the test solution to

Electrochemical experiments were performed using the potentiostat / Galvanostat Wenking PGS 95. i-E curves were recorded by computer software from the company (Model ECT). Except otherwise stated ,the potential was swept linearly from the starting potential vs. (SCE) into the positive direction up to a certain anodic potential with a given scan rate and

For each run, freshly prepared solutions as well as a cleaned set of electrodes were used. All experiments were conducted at a given temperature (± 0.5 oC) with the help of circular water thermostat. After polymer film formation, the working electrode was withdrawn from the cell, rinsed thoroughly with doubly distilled water to remove any traces of the medium

then reversed with the same scan rate up to the starting cathodic potential.

and other type of electrodes [Iotov, & Kalcheva, 1998; Ezerskis & Jusys, 2002]. Deactivation of electrode due to the phenol polymerization is more characteristic in alkaline medium. Insoluble high molecular weight species block the electrode surface and prevent effective electrooxidation of phenol.

In the present work, we seek to contrast the electro-oxidation of OCP and OHP from aqueous H2SO4 medium as electrolyte using cyclic voltammetry technique. The kinetic study of the oxidation processes will be useful for optimize the parameters control it. Mechanisms of the electrochemical polymerization will be discussed using electrochemical data. Also, the characterization of the obtained polymer films were carried out by elemental analysis, TGA, SEM, XRD, IR, UV-vis., 1H-NMR spectroscopy. We hope to have films with good characters to be used in applications (i.e. dye removal and pH sensor).
