Nanosized silica–titanium oxide as a potential adsorbent for C.I. Acid Yellow 219 dye removal from textile baths and wastewaters

摘要

The mixed SiO₂–TiO₂ oxide obtained by the pyrogenic method with the silica:titanium percentage ratio equal to 80:20 (ST20) was used as a potential adsorbent for the removal of hazardous azo dye C.I. Acid Yellow 219 (AY219) from aqueous solutions. Based on the values of determination coefficients ( r 2), it can be stated that the Freundlich ( r 2?=?0.929) model fitted the experimental data better than the Langmuir ( r 2?=?0.920) and Tempkin ( r 2?=?0.848) ones. In the system containing 20?mg/L AY219, the amount of dye adsorbed ( q _t ) by ST20 was equal to 9.7?mg/g and the time necessary to reach equilibrium was 120?min. The sorption of AY219 on ST20 may be described by the pseudo-second-order model ( r 2?=?0.999) as the adsorption capacity was calculated as 9.69?mg/g. The amount of AY219 adsorbed decreased with the increasing concentration of additives such as anionic and non-ionic (Triton X-100) surfactants. In the presence of cationic surfactant, the reverse dependence was observed. Anionic dye additions influence the structure of electrical double layer formed on the surface of mixed oxide particles. The presence of negative charges in adsorbed AY219 molecules results in increase of the solid surface charge density with simultaneous decrease of the zeta potential of ST20 particles. The addition of surfactants with different ionic character causes formation of complexes whose presence at the mixed oxide–liquid interface influences considerably both the solid surface charge density and the zeta potential of ST20 particles dispersed in aqueous solution.