Facile preparation of a remarkable MOF adsorbent for Au(III) selective separation from wastewater: Adsorption, regeneration and mechanism

The recovery of valuable elements from wastewater could reduce pollution and increase resource utilization. A novel Zr-based MOF (DONA-MOF) was synthesized using an organic linker and several chelates as adsorbent. The successful preparation of DONA-MOF was confirmed by SEM, EDS, FTIR and XRD. The adsorption performance of DONA-MOF is systematically evaluated through a series of adsorption experiments. DONA-MOF has an excellent removal effect on Au(III) in pH 2–9. The adsorption reaches equilibrium in 120 min at 100 mg·L-1. 637.5 mg·g−1 is the maximum adsorption capacity of DONA-MOF at 303 K. The kinetics and isotherm models show that the adsorption behavior of Au(III) on DONA-MOF is monolayer chemisorption. In addition, thermodynamic study indicates a spontaneous and endothermic adsorption behavior. Wastewater experiments show that DONA-MOF can preferentially adsorb Au(III). The adsorption-desorption experiments show that DONA-MOF still has an excellent removal effect after five cycles. The R2 of Xm2r linear fitting is 0.99005, which indicates that the chelation interaction is involved in the adsorption process. The results of zeta potential and XPS show that electrostatic attraction, chelation and reduction are the main adsorption mechanism. Since DONA-MOF has significant adsorption capacity and excellent selectivity to Au(III), it is expected to be applied in practice.