Influence of ionic strength in the adsorption and during photocatalysis of reactive black 5 azo dye on TiO2 coated on non woven paper with SiO2 as a binder

Reactive black 5 (RB5), an azo dye, was degraded by using UV-irradiated TiO2 coated on non woven paper with SiO2 as a binder. The adsorption capacity of the photocatalyst was studied at natural pH, superior to pHpzc of the binder, for various ionic strengths. Different salts such as NaCl, KCl, CaCl2, LiCl, Ca(NO3)2 were used to increase the ionic strength. The presence of salt increased the adsorption capacity. The electrostatic interactions between dye and oxide surface charges (TiO2/SiO2) is very important in the adsorption phenomena. The effect of the ionic strength of the solution on photocatalyst degradation was studied. The rate of degradation was increased by the presence of salts in the range of the experimental conditions. The increase of the initial decolorization rate was observed in the following order: Ca2+ > K+ > Na+ > Li+. Experiments with different anions (Cl-, NO3-) had shown that nitrate was an indifferent electrolyte for the adsorption and photodegradation of the dye on SiO2/TiO2