β-cyclodextrin and TiO2 synergistically enhance the negative charge and reduce roughness for ultrafiltration membranes: Preparation and performance analysis

How to prepare polyvinylidene fluoride (PVDF) membranes with high flux, high rejection rate, strong anti-fouling ability and excellent durability is a crucial issue in the current production and application industries of PVDF membranes. In this work, an environmentally friendly mechanical grinding method was employed to composite β-cyclodextrin (CD) with titanium dioxide (TiO 2 ) nanoparticles, resulting in the preparation of CD@Ti composite nanomaterials. These were then incorporated into PVDF membranes to fabricate a series of nanocomposite membranes (NCM). Compared with the pristine PVDF membrane, the PVDF/CD@Ti 1.5 membrane exhibited a 1.67-fold increase in water flux, and its rejection rate for bovine serum albumin (BSA) improved from 86.6 % to 97.1 %. Compared to modification using TiO 2 alone, the CD@Ti composite modification effectively suppressed particle agglomeration within the membrane. The PVDF/CD@Ti 1.5 membrane demonstrated enhanced hydrophilicity, increased surface negative charge, and reduced surface roughness compared to the initial PVDF membrane, all of which contributed to improved antifouling performance. Specifically, after filtering BSA, humic acid (HA), and sodium alginate (SA), and subsequently rinsing with pure water, the flux recovery ratio (FRR) of the pristine PVDF membrane were 73.6 %, 64.8 %, and 53.5 %, respectively, whereas those of the modified PVDF/CD@Ti 1.5 membrane increased to 89.3 %, 83.5 %, and 78.4 %, respectively. Analysis based on the Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory indicated that the incorporation of CD@Ti effectively reduced the attractive interaction energy between the PVDF/CD@Ti membrane and foulants. Furthermore, the PVDF/CD@Ti 1.5 membrane demonstrated excellent stability in multiple filtration cycles, real lake water filtration tests, and acid–base immersion experiments, confirming its potential for practical applications.