Simultaneous and ultrafast removal of anionic and cationic dyes from aqueous solution by Zr-based MOFs hybridized by attapulgite and adsorption performance research

Zr-based MOFs hybridized by attapulgite (APT) were successfully prepared by simple reflux method and characterized by FTIR, BET, XRD, TGA and XPS. Both cationic and anionic dyes were efficiently, quickly and simultaneously adsorbed by UiO-66, 1%APT/UiO-66 and 5%APT/UiO-66 in 5 min. In anionic dyes (Congo red and alizarin yellow GG) and cationic dye methylene blue, adsorption capacities of UiO-66, 1%APT/UiO-66 and 5%APT/UiO-66 for Congo red were higher, 304.07, 585.00 and 394.63 mg/g, respectively. Capillary effect was adopted to explain characteristic trend of adsorption kinetic curves (first decrease and then increase of adsorption capacity in the second stage). Pseudosecond-order kinetic model and Langmuir isotherm was the best fit model to evaluate adsorption behaviors of UiO-66, 1%APT/UiO-66 and 5%APT/UiO-66 for adsorption of Congo red. It was more favorable and effective for prepared materials to removal Congo red from solutions containing inorganic salts. When concentration of NaCl was 0.09 mol/L, adsorption capacities of 1%APT/UiO-66 were increased to 589.77, 724.56 and 635.59 mg/g, accordingly. UiO-66, 1%APT/UiO-66 and 5%APT/UiO-66 exhibited good stability and reusability. Main adsorption driving forces were hydrogen bonding interactions, pi-pi conjugations, electrostatic interactions and sieving effects, and adsorption driving forces of 1%APT/UiO-66 were largest. Above results indicated that UiO-66 hybridized by APT could simultaneous and ultrafast removal of anionic and cationic dyes in aqueous solution, and were potential adsorbents in practical application.