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In the present work, the coupling of adsorption and electrochemical oxidation on a boron-doped diamond (BDD) electrode to treat solutions containing dyes is studied. This coupling may be convenient for the treatment of diluted pollutant that is limited by the low rate of electrooxidation due to mass-transfer limitation. A pre-concentration step by adsorption could minimize the design of the electrochemical reactor. The adsorbent chosen was mixed with softwood sawdust, and methylene blue was chosen as the model dye molecule. Isotherms of adsorption and kinetics were investigated as well as the effects of current density and regeneration time. The BDD electrochemical oxidation of methylene blue adsorbed onto sawdust led simultaneously to its degradation and sawdust regeneration for the next adsorption. It was observed that multiple adsorption and electrochemical regeneration cycles led to an enhancement of adsorption capacity of the sawdust. This study demonstrated that adsorption–electrochemical degradation coupling offers a promising approach for the efficient elimination of organic dyes from wastewater.

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.