Adsorptive removal of C.I. Direct Yellow 142 from textile baths using nanosized silica-titanium oxide

Abstract

.The adsorption properties of the silica-titanium mixed oxide consisting of 80 wt.% SiO2 and 20 wt.% TiO2 (ST20) in relation to C.I. Direct Yellow 142 (DY142) were examined. The experimental adsorption capacity of ST20 for DY142 determined at room temperature equals 104.8 mg/g. The equilibrium data were fitted by means of the Freundlich, Langmuir and Tempkin isotherm models. The values of determination coefficients (r2) confirmed applicability of the Langmuir ( r^{2}=0.990) isotherm model, the monolayer capacity was found to be 106.5 mg/g. The kinetic parameters calculated from the pseudo-first-order (PFO) and pseudo-second-order (PSO) equations as well as the intraparticle diffusion (IPD) model revealed that the chemisorption is the rate limiting step as the r2 value obtained for the pseudo-second-order model equals 0.999. The PSO adsorption rate constant was found to be 0.070 g/mg min. The presence of additives such as electrolytes (Na2SO4 and Na2CO3) and surface active agents (anionic SDS, cationic CTAB and non-ionic Triton X-100) reduce dye retention compared to systems that do not contain these additives. The presence of the dye with the anionic character in the colloidal suspension of ST20 oxide particles results in considerable increase of the solid surface charge density. In the systems of mixed adsorbates (dye-surfactant and dye-salt) the specific changes in surface properties were obtained --the cationic surfactant has the greatest effect on the solid surface groups type and its concentration.