Preparation of Ice-Templated MOF–Polymer Composite Monoliths and Their Application for Wastewater Treatment with High Capacity and Easy Recycling

5 years ago

Preparation of Ice-Templated MOF–Polymer Composite Monoliths and Their Application for Wastewater Treatment with High Capacity and Easy Recycling

Haifei Zhang, Daniel Pun, Yonghong Yang, Xuedan Chen, Lei Zhang, Adham Ahmed, Lang Wen, Qingshan Fu

An ice-templating process was used to fabricate polymer/MOF monoliths, specifically chitosan/UiO-66, as adsorbents for water treatment. The ice-templated macropores enhanced mass transport, while the monoliths could be easily recovered from solution. This was demonstrated by the adsorption of methylchlorophenoxypropionic acid (MCPP, a herbicide compound) from dilute aqueous solution. To enhance the stability, the freeze-dried monoliths were treated with NaOH solution, solvent exchanged, and dried. The treated chitosan/UiO-66 monolith achieved an adsorption capacity of 34.33 mg g^–1 (a maximum theoretic value of 334 mg g^–1 by the Langmuir model), closer to the capacity (36.00 mg g^–1) of the freshly prepared UiO-66 nanoparticles and much higher than that of the NaOH-washed UiO-66 nanoparticles (18.55 mg g^–1), by performing the tests in 60 ppm MCPP solution. The composite monolith could be easily picked up using tweezers and used for recycling tests. Over 80% of the adsorption capacity was retained after three more cycles. The powder X-ray diffraction and N₂ sorption studies suggested the crystalline structure of UiO-66 was destroyed during NaOH washing procedure. This, however, provides the potential to improve the adsorption capacity by developing methods to fabricate true polymer/MOF composites.

Publisher URL: http://dx.doi.org/10.1021/acsami.7b10872

DOI: 10.1021/acsami.7b10872