In the present study, the titania based adsorbent (Adsorbsia As500) was used for removal of three textile dyes such as C.I. Acid Red 18, C.I. Reactive Blue 21 and C.I. Direct Yellow 50 from aqueous solutions. The dye sorption was investigated by the batch and column methods. The experimental data were analyzed by the Langmuir, Freundlich and Temkin models of adsorption. Adsorbsia As500 exhibited the highest affinity towards DY50 as the monolayer sorption capacity were equal to 109.71 mg/g. The kinetic data obtained at different dyes concentrations were fitted to the pseudo-first order, pseudo-second order and Elovich equations. The dyes desorption experiments were investigated, too.

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The mixed SiO 2 -TiO 2 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.

Intensive development of many industries, including textile, paper or plastic, which consume large amounts of water and generate huge amounts of wastewater-containing toxic dyes, contribute to pollution of the aquatic environment. Among many known methods of wastewater treatment, adsorption techniques are considered the most effective. In the present study, the weakly basic anion exchangers such as Amberlyst A21, Amberlyst A23 and Amberlyst A24 of the polystyrene, phenol-formaldehyde and polyacrylic matrices were used for C.I. Direct Yellow 50 removal from aqueous solutions. The equilibrium adsorption data were well fitted to the Langmuir adsorption isotherm. Kinetic studies were described by the pseudo-second order model. The pseudo-second order rate constants were in the range of 0.0609–0.0128 g/mg·min for Amberlyst A24, 0.0038–0.0015 g/mg·min for Amberlyst A21 and 1.1945–0.0032 g/mg·min for Amberlyst A23, and decreased with the increasing initial concentration of dye from 100–500 mg/L, respectively. There were observed auxiliaries (Na2CO3, Na2SO4, anionic and non-ionic surfactants) impact on the dye uptake. The polyacrylic resin Amberlyst A24 can be promising sorbent for C.I. Direct Yellow 50 removal as it is able to uptake 666.5 mg/g of the dye compared to the phenol-formaldehyde Amberlyst A23 which has a 284.3 mg/g capacity.