Hybrid adsorbents of tannin and APTES (3-aminopropyltriethoxysilane) and their application for the highly efficient removal of acid red 1 dye from aqueous solutions

Abstract

Hybrid adsorbents were prepared by reacting tannin with different amounts of 3-aminopropyltriethoxysilane (APTES). The materials were characterized by SEM, TEM, FTIR, CHN, N2 adsorption/desorption isotherms and vapor sorption (water and n-heptane adsorptions–for determination of the hydrophobicity-hydrophilicity ratio). The modified materials were utilized as adsorbents for the removal of Acid Red 1 (AR-1) dye from aqueous solutions. The N2 isotherm results showed low porosities of the modified materials, however they presented high efficient adsorption of AR-1 dye. To find a proof of hybridization between tannin and APTES, the materials were characterized by Diffuse Reflectance Ultraviolet-Visible Absorption (DRUV) spectroscopy. The results indicate that the electronic structure of the final materials was changed, and was related to a hybrid formation between tannin and APTES.For the adsorption experiments, the best experimental conditions were reached at pH 2.0, contact time of 8h and at 50°C. The equilibrium and kinetics adsorption data were well represented by the Liu isotherm and the General order kinetic models, respectively. The maximum adsorption capacity of 418.3mgg−1 was obtained at 50°C for a tannin-APTES material at ratio 1:1 (Tan-Ap-1.0). Based on experimental data it was found that electrostatic interactions and hydrogen bonds between adsorbent and AR-1 dye played the most important role in the adsorption process.Effect of temperature and thermodynamic studies revealed that the adsorption processes of AR-1 onto tannin materials are dependent on temperature and are exothermic and spontaneous. With regards to the applicability of the adsorbents for treating simulated effluents, they showed an excellent outcome confirming their high-efficiency for dye adsorption.