Synthesis of porous UiO-66-NH2-based mixed matrix membranes with high stability, flux and separation selectivity for Ga(III)

Reported powdery adsorbents with poor adsorption efficiency and stability make it imperative to develop novel materials to extract gallium ions (Ga(III)) from effluents. Herein, UiO-66-NH2-based mixed matrix membranes (TPU/0.1THB/U6N-1.5 MMMs) via electrospinning is firstly reported for separation and recovery of Ga(III). TPU/0.1THB/U6N-1.5 MMMs efficiently overcomes multiple bottlenecks of powder UiO-66-NH2, including poor stability, reusability and adsorption capacity. Its maximum adsorption for Ga(III) is 96.18 mg.g(-1) at pH 10.0. It has superiority in selective adsorption of Ga(III) from Al(III), Cu(II), Zn(II), Co(II) coexistence solution. Adsorption capacity of TPU/0.1THB/U6N-1.5 for Ga(III) reaches more than 80% after 9 cycles. Specially, it still retains excellent mechanical strength, flexibility and structural integrity after 12 h filtration, or after 9 adsorption-desorption cycles, even soaked in 5 mol.L (-1) HCl for a week. TPU/0.1THB/U6N-1.5 MMMs also improves the problem of low water flux. TPU/0.1THB/U6N-1.5 with high MOFs loading possess high water flux of 382.2 L.m(-2) .h(-1) with a permance of 382.2 L.m(-2).h(-1).bar(-1) and rejection rates of 90% for Ga(III). The main adsorption mechanism of TPU/0.1THB/U6N-1.5 is based on the chelation between phenolic hydroxyl groups of MMMs and Ga(III) at pH 10.0. Overall, the as-prepared TPU/0.1THB/U6N-1.5 has potential for water treatment through the process of membrane adsorption.