Carbon nanotube-adsorptive dynamic membrane (CNT-ADM) for water purification. (February 2023) - Zhang, Wenxiang
Abstract: Membrane technology plays an important role in water purification, but there are some significant challenges such as membrane fouling and deep purification efficiency. The work proposes a carbon nanotube-adsorptive dynamic membrane (CNT-ADM), including carbon nanotube (CNT) and membrane module, to solve these problems with low operating cost and high removal efficiency. Above all, on the basis of physical adsorption and membrane separation, a CNT-ADM was prepared by applying "forward filtration" of a CNT solution on an ultrafiltration membrane surface. Then, the effects of preparation time, CNT loading amount, transmembrane pressure (TMP) and shear stress on the morphology and permeability were analyzed to evaluate the preparation performance. Pore blocking models were utilized to explain the influence of CNT loading amount on membrane fouling mechanism. The best optimized condition for CNT-ADM preparation was: agitation speed of 50 rpm, TMP of 1 bar, CNT loading amount of 55 g/m 2 and preparation time of 10 min. Furthermore, the optimized CNT-ADM was employed to treat the micro-polluted water. The effects of treatment condition on the micropollutant removal rate and flux were investigated with various shear stresses, TMPs, the amounts of micropollutant and CNT. Compared with the new membrane (below 10 %), CNT-ADM displayed a significant improvement for the micropollutant removal (above 95 % for three cycles), due to the synergy of membrane separation (sustaining CNT layer, separating micropollutant and increasing adsorption time) and adsorption removal (forming CNT layer and adsorbing micropollutant). On the other hand, the adsorption behavior also could effectively reduce the direct contact between membrane and micropollutant, then decreasing membrane fouling. Afterwards, the backwash cleaning was also successfully applied to alter the adsorption saturated CNT and generate the new CNT layer. In final, the implications for CNT-ADM application were discussed. Overall, CNT-ADM exhibits the desirable micropollutant removal and strong anti-fouling capacity, and has a great potential application in the sustainable water purification. Graphical abstract: Unlabelled Image Highlights: CNT-ADM was prepared by "forward filtration" and physical adsorption on membrane. The CNT-ADM with homogenous porous structure had excellent permeability. The CNT-ADM by optimized preparation conditions was used to treat micro-polluted water. The removal mechanisms were adsorption and double (membrane and CNT layer) separation Backwash altered the adsorption saturated CNT and generate new CNT layer