Enhanced water permeability and rejection of As(III) in groundwater by nanochannels and active center formed in nanofibrillated celluloses UF membranes with ZIF-8

Abstract

Surface-modified UF membranes are considered to be effective in removing strong toxic, high pKa, difficult-to-remove As(III) from contaminated groundwater but usually leads to a loss of water permeability. Hybrid UF membranes prepared from porous particles can be used to solve this problem due to their abundant nanochannels and outstanding rejection. Herein, porous ZIF-8 modified nanofibrillated celluloses UF membranes (ZIF-8/NFCUM) were prepared by co-mixing and filtration for enhancing the removal of As(III). The results show that ZIF-8 in solution not only achieves As(III) rejection of 97.65% through the formation of active Zn–OH and –NH+ by hydration but also contributes to the enhancement of the water permeability of the membrane through its abundant nanochannels. Furthermore, ZIF-8/NFCUM has also excellent stability that can extend its service life. Except for the phosphate ion which has a significant inhibitory effect on the separation of As(III), ZIF-8/NFCUM can maintain high rejection (>70%) in the environment of many coexisting ions. Moreover, ZIF-8/NFCUM also has good anti-fouling properties with hydrophilic, high desorption rate (94.36%), and excellent reusability with 73.21% rejection of As(III) after 7 cycles. Thomas dynamics and simulated separation of As(III) in polluted groundwater further demonstrated the excellent practical performance of ZIF-8/NFCUM. Besides, ZIF-8/NFCUM has a high removal rate for dyes such as methylene blue and malachite green, especially methylene blue can reach almost 100%. This result shows that ZIF-8/NFCUM is expected to achieve the removal of As(III) from contaminated groundwater and can also be used for the removal of other contaminants (dyes), which has a wide application prospect.