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A new hybrid process that integrates adsorption on sawdust and electrochemical oxidation on a boron doped diamond anode was investigated for the treatment of dilute solutions containing phenol. In such combined process the pollutant is adsorbed until saturation and electrochemical oxidation has been used for both the regeneration of adsorbant and the pollutant removal. Phenol is used as model of pollutant and the efficiency of the regeneration of loaded sawdust has been compared with that of activated carbon (AC), a widely used adsorbent due to its high adsorption capacity which results from its high porosity. The study highlights the effect of electrolysis in the increase of the phenol desorption during the treatment of adsorbents. The regeneration efficiency of AC after 1 cycle of adsorption and regeneration is only 59% due to the electropolymerisation of the strongly adsorbed phenol. By contrast, the electrochemical regeneration of sawdust led to increase the adsorption capacity multiple adsorption and electrochemical regeneration cycles led to an enhancement of adsorption capacity of the sawdust with a complete removal of phenol and the possible reuse of the electrolysis solution.

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The electrochemical regeneration of methylene blue-saturated adsorbents has been assessed in this work. This study compares the performances of activated carbon, Nyex®1000 and sawdust. Isotherms of adsorption were investigated and the maximum adsorption capacity was compared. The maximum adsorption capacity obtained for MB onto the virgin sawdust reached 25 mg/g which is 11.4 times lower than the one obtained onto activated carbon. The electrochemical regeneration efficiency, under the same experimental conditions, of the activated carbon and Nyex®1000 were significantly less than 100% while in the case of sawdust, this efficiency increased after each adsorption. This study confirmed that the coupling adsorption onto sawdust and electrochemical degradation is a potential technique for the efficient elimination of low concentration organic dyes from waste water.

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The first part of this work relates to the analytical study of the electrochemical behavior of 1,3,5-trimethoxybenzene (TMB) by cyclic voltammetry at treated gold electrode. The second part is relative to the results of its conversion into a high added value product 2,6-dimethoxy-1,4-benzoquinone (DMBQ) by electrolysis at lead dioxide anode. The used electrolyte which is a simulated solution of TMB in water-acetone mixture should be prepared using a preconcentrated TMB wastewater. The partial substitution of water by acetone permit to control the TMB solubility to avoid the electrochemical efficiency reduction by TMB transfer limitation. Moreover, the DMBQ desorption from the electrode surface by the effects of acetone and its displacement by TMB provides the slowdown of its degradation. The electrochemical DMBQ recovery increases with the enhancement of acetone volumic percentage and decreases by increasing the current density.