Engineering of UiO-66-NH as selective and reusable adsorbent to enhance the removal of Au(III) from water: Kinetics, isotherm and thermodynamics.

Efficient removal of gold ions from wastewater has become a hot research topic. A new metal-organic framework material (PAR-UiO-66) was prepared by post-modification of UiO-66-NH. A series of characterizations proved the successful preparation of PAR-UiO-66. The batch adsorption experiment was carried out. Under the room temperature (298 K) of and pH 4.0, the optimal adsorption capacity of PAR-UiO-66 for gold ions was 683.45 mg/g, which was an increase of 426.8 mg/g compared with that of UiO-66-NH. The adsorption of gold ions on PAR-UiO-66 accords with pseudo-second-order kinetics and Langmuir isotherm modles. The adsorption process was endothermic and spontaneous. PAR-UiO-66 has good selectivity and still has 92.5% adsorption efficiency after five repeated adsorptions. The adsorption mechanism is electrostatic attraction, reduction and chelation.