3D flower-like UiO-66-NH 2 @ZiF-8 (UZ) nanoparticles have porous structural properties and multifunctional functional groups exposed on the surface, which provide significant advantages in improving compatibility with polymers and exceptional molecular sieve performance. Poly( p -phenylene terephthamide) PPTA is an acid/alkali resistant porous membrane material. However, the preparation of highly permeable and selective nanofiltration (NF) membranes is still a challenging problem due to the low permeability of PPTA NF membranes. Therefore, in this study, PPTA/UiO-66-NH 2 @ZiF-8 (PUZ) membranes were prepared using spacer spray-assisted interfacial polymerization. It was investigated that the effects of different additions of 3D flower-like UZ nanoparticles on the physicochemical properties and structure of PUZ membranes. The results showed that the polyamide structures with different morphologies were formed on the PUZ membranes surface by depositing 3D flower-like UZ nanoparticles at a spraying frequency of 12 min −1 . When 1.3 g/L of 3D flower-like UZ nanoparticles were interval sprayed, the PUZ4 membranes surface showed a unique doughnut-like structure and featured tubular and doughnut-like interconnections. PUZ4 membranes exhibited 4.4 times higher permeance and maintained excellent dye rejection (methylene blue dye permeance up to 58.23 L/m 2 ∙h∙MPa and methylene blue dye rejection of 99.60 %) compared to pristine PPTA NF membranes (methylene blue dye permeance up to 13.25 L/m 2 ∙h∙MPa and methylene blue dye rejection of 92.10 %). In addition, the modified PUZ4 membranes had a great antifouling performance with a recovery ratio of 99.43 % for more than 6 cycles and a high rejection rate of 98.51 % at 0.1 MPa.
Yinghui Xu,Xuan Zhao,Ran Chang,Hongqiang Qu,Jianzhong Xu,Jing Ma
Rationally regulating the separation pores is an effective way to achieve efficient separation membrane . However, the developed metal-organic framework (MOF) membranes for water treatment are all formed by one kind of MOF, which can only provide rigid pores, makes it difficult to achieve high flux and excellent rejection ratio simultaneity. Here, we proposed a facile strategy for the synthesis of heterogeneous MOF-on-MOF membrane with hierarchical pores, by site-specific grown ZIF-8 layer on UiO-66-NH 2 layer. Thus unique architecture of the obtained double-layered MOF membrane (UiO-66-NH 2 @ZIF-8) endows multidimensional separation pores: (i) the large pores of UiO-66-NH 2 can facilitate water transportation, (ii) the molecular-sieving pores of ZIF-8 can intercept dyes, (iii) UiO-66-NH 2 acting as active sites can promote the growth of ZIF-8. As a result, the optimized UiO-66-NH 2 @ZIF-8 membrane exhibits high flux (36.7 L m −2 h −1 bar −1 ) and excellent dye rejections (>97.0%). Through analysis and comparison, the regulated multi-type pores play an important role in membrane performance. Coupled with the facile membrane preparing method, this work can used as a potential approach of designing other advanced MOF membrane for water treatment.
With the ever-increasing of Rare Earth Elements (REEs) in various high technology applications, efficient recovery of REEs from liquid sources is becoming significantly important. In this work, ZIF-8 and UiO-66-NH 2 (U6N) are combined to form a 3D-agaric like core-shell structure hybrid material (U6N@ZIF-8-20), which exhibits good performance in REEs extraction. Due to the abundant adsorption sites of ZIF-8 and the excellent water stability of UiO-66-NH 2 , 3D-agaric like U6N@ZIF-8-20 showed quick adsorption rate (only 10 min to reach equilibrium), high adsorption capacity and selectivity for REEs from water compared to other reported adsorbents. Maximum adsorption capacities of U6N@ZIF-8-20 for neodymium (Nd(III)), europium (Eu(III)), gadolinium (Gd(III)) and erbium (Er(III)) achieved to 249.90, 295.28, 316.22 and 340.95 mg g -1 , respectively. U6N@ZIF-8-20 has superiority in selective adsorption of REEs from Cd(II), Zn(II), Cu(II), Mn(II) and Co(II) coexistence solution. The order of adsorption capacities for REEs is in agreement with the order of their electronegativity, ionic radius and charge density. Moreover, U6N@ZIF-8-20 showed better water stability and recyclability than single MOF. Overall, MOF@MOF hybrid material has efficiency in REEs separation from solutions, and has great advantage in the application of wastewater treating.
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