Preparation of Zr-MOF/Poly(hexamethylenediamine-tannic acid)/Attapulgite for efficient Cr(VI) removal

In this study, attapulgite (ATP) was modified by Zr-based metal organic framework (UiO-66-NH2) and poly(hexamethylenediamine-tannic acid) (HTA), an amino material named UiO-66-NH2/HTA/ATP (UHA) was prepared to efficiently remove Cr(VI). The morphology and structure of UHA were analyzed through various characterization methods. The conditions and influencing factors of UHA preparation and Cr(VI) adsorption were studied. The material had a maximum adsorption capacity of 270.3 mg/g for Cr(VI) when pH was 2.0, temperature was 298 K, adsorption time was 300 min, and ionic strength was 0.01 mol/L, which was obtained by the Langmuir fitting model. The adsorption process conforms to the pseudo-second-order kinetic and Langmuir isothermal models, indicating that the adsorption process is mainly based on the chemical adsorption of monolayers. X-ray photoelectron spectroscopy analysis shows that UHA mainly removes Cr(VI) by hydrogen bonding, electrostatic attraction, reduction, and complexation. Thermodynamic investigation suggested a disordered, endothermic and spontaneous adsorption process. After UHA treatment, the simulated wastewater containing Cr(VI) met the discharge standard, and the results of cycling experiments showed that UHA has good renewable performance and offers potential prospects for Cr(VI) removal in water.