Scalable, flexible, ultra-strong, free-standing papery all carbon nanotube membrane with excellent separation and antifouling properties

Carbon nanotube (CNT) based membranes have shown tremendous promise for water purification. However, fabricating free-standing all CNT membranes with excellent separation and antifouling properties remains challenging. Here, a densified flexible, ultra-strong, free-standing papery all CNT membrane with excellent separation and antifouling properties is reported. The chemically densified free-standing CNT membrane has an extremely high tensile strength up to 330 MPa, four times higher than the original CNT membrane and one order of magnitude higher than most polymeric membranes. The negatively charged surface of the densified CNT membrane enables efficient separation of two dyes even with similar molecular sizes. Meanwhile, the densified CNT membrane exhibits superior antifouling performance during the filtration of dyes, humic acid and bovine serum albumin solutions, and oil-in-water emulsions due to its reinforced hydration layer induced by the hydrophilic functional groups resulting from chemical densification. The chemically densified CNT membrane shows not only excellent separation and antifouling performance, but also superior long-term stability and regeneration performance in the filtration of foulant-containing solutions. This study may pave the way for large-scale application of densified free-standing all CNT membranes in the realm of water treatment.