Reactive dyes remotion by porous TiO 2-chitosan materials

Abstract

In this work, the aim was to evaluate the remotion (adsorption plus degradation) of two reactive dyes, Methylene Blue (MB) and Benzopurpurin (BP), from aqueous solutions by the utilization of TiO 2-chitosan microporous materials. Two different TiO 2-chitosan hybrid materials were synthesized: TiO 2-Chit A with 280 mg chitosan/gTiO 2 and TiO 2-Chit B with 46.76 mg chitosan/g TiO 2. Adsorption data obtained at different solution temperatures (25, 35, and 45 °C) revealed an irreversible adsorption that decrease with the increment of T. Langmuir, Freundlich and Sips isotherm equation were applied to the experimental data. The obtained parameters and correlation coefficient showed that the adsorption of both dyes on TiO 2-Chit A at the three work temperatures was best predicted by the Langmuir isotherm, while Sips equation adjusted better to adsorption data on TiO 2-Chit B. The adsorption enthalpy was relatively high and varied with T, indicating that interaction between adsorbent and adsorbate molecules was not only physical but chemical. There is a change in the adsorption heat capacity, ( Δ ads C p < 0), related with intense hydrophobic interactions. The kinetic adsorption data were processed by the application of Lagergren and Avrami models. It was found that adsorption of both dyes on both adsorbents under the operating conditions was best predicted by Avrami model. The variation of kinetic order, n, and k av with T are related to a pore followed by intra particle diffusion control of the adsorption rate. MB photodegradation on both TiO 2-chitosan hybrid materials was of 91 (in A) and 41% (in B) and augmented with the chitosan content. For BP can be seen that the process in darkness resulted in a high remotion capacity than in UV light presence.