Treatment of dilute methylene blue-containing wastewater by coupling sawdust adsorption and electrochemical regeneration.

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 adsorption­electrochemical degradation coupling offers a promising approach for the efficient elimination of organic dyes from wastewater.

Infrared characterization and electrochemical study of γ-methacryloxypropyltrimethoxysilane grafted in to surface of copper.

The formation of a protective layer of γ-methacryloxypropyltrimethoxysilane (γ-MPS) on copper is studied by diffuse reflectance infrared spectroscopy (DRIFT), gravimetric chemical (weight loss) and electrochemical (cyclic voltammetry and potentiodynamic polarization) measurements. By simple immersion in the silanic bath (90/5/5 v/v ethanol/water/silane), this agent immediately physisorbed on copper, but the protective effects are poor. Thiolate and siloxane band formation improve the performances of the silanic layer on the surface of copper especially after heat treatment process. Chemical and electrochemical measurements show that the protective action of heat treatment (HT/Cu-MPS) process is higher than that of aged process (aged/Cu-MPS).

Electrochemical degradation of 4-chloroguaiacol for wastewater treatment using PbO2 anodes.

Electrochemical oxidation of 4-chloroguaiacol (4-CG) at Nb/PbO(2) anodes was studied under different experimental conditions such as initial concentration of substrate, electrolysis time, temperature and pH. We measured the concentrations of 4-chlorocatechol (4-CC), 2-methoxyhydroquinone (2-MHQ), maleic acid (MA) and carbon dioxide as the main products. Black solid particles consisting mainly of polymers were formed during electrolysis. A mechanism of electrochemical oxidation of 4-CG was investigated. The oxidation of 4-CG can generally be described by simple pseudo first-order kinetics. The degradation of 4-CG was favoured at high temperature and lower initial concentration of 4-CG and low solution pH. However, the increase of temperature has not a significant effect on the mineralization of carboxylic acids. Moreover, these products required long electrolysis time.