Mn-doped zirconium metal-organic framework as an effective adsorbent for removal of tetracycline and Cr(VI) from aqueous solution

Metal-organic frameworks (MOFs) with porous property have gained much concern in environment remediation. Herein, the Mn-doped UiO-66 (denoted as MnUiO-66) with cubic morphology was fabricated with a facile solvothermal method. To investigate the adsorption performance of MnUiO-66, tetracycline (TC) and Cr(VI) were chosen as the target pollutant. The maximum adsorption capacity of MnUiO-66 for TC and Cr(VI) were 184.493 mg g−1 and 32.773 mg g−1, respectively, which were 4.9 and 3.1 times higher than the pristine UiO-66. Effects of the solution pH values, initial concentrations and coexisting ions on adsorption capacity were investigated and the adsorption mechanism based on zeta potential measurement was proposed. The adsorption process of MnUiO-66 over TC and Cr(VI) had the most accordance with pseudo-second-order and Langmuir models, which suggested that chemisorption was dominant in adsorption reaction and the MnUiO-66 adsorbent had a homogenous surface for adsorption. Adsorption thermodynamic studies implied that the adsorption process of TC and Cr(VI) on MnUiO-66 were spontaneous and exothermic. In addition, the MnUiO-66 showed excellent adsorption performance in TC-Cr(VI) mixed sample and pharmaceutical wastewater. More importantly, the regeneration experiment indicated the MnUiO-66 adsorbent was recyclable. This work provided a useful insight into the fabrication MOFs-based adsorbent for water purification.