Electrospun polyacrylonitrile nanofibrous membranes supported with montmorillonite for efficient PM2 .5 filtration and adsorption of Cu ( II ) ions

ZnO-PLLA/PLLA Preparation and Application in Air Filtration by Electrospinning Technology

With the increasing environmental pollution caused by disposable masks, it is crucial to develop new degradable filtration materials for medical masks. ZnO-PLLA/PLLA (L-lactide) copolymers prepared from nano ZnO and L-lactide were used to prepare fiber films for air filtration by electrospinning technology. Structural characterization of ZnO-PLLA by H-NMR, XPS, and XRD demonstrated that ZnO was successfully grafted onto PLLA. An L₉(4³) standard orthogonal array was employed to evaluate the effects of the ZnO-PLLA concentration, ZnO-PLLA/PLLA content, DCM(dichloromethane) to DMF(N,N-dimethylformamide) ratio, and spinning time on the air filtration capacity of ZnO-PLLA/PLLA nanofiber films. It is noteworthy that the introduction of ZnO is important for the enhancement of the quality factor (QF). The optimal group obtained was sample No. 7, where the QF was 0.1403 Pa^-1, the particle filtration efficiency (PFE) was 98.3%, the bacteria filtration efficiency (BFE) was 98.42%, and the airflow resistance (Δp) was 29.2 Pa. Therefore, the as-prepared ZnO-PLLA/PLLA film has potential for the development of degradable masks.

Recyclable Composite Membrane of Polydopamine and Graphene Oxide-Modified Polyacrylonitrile for Organic Dye Molecule and Heavy Metal Ion Removal

Developing efficient and recyclable membranes for water contaminant removal still remains a challenge in terms of practical applications. Herein, a recyclable membrane constituted of polyacrylonitrile-graphene and oxide-polydopamine was fabricated and demonstrated efficient adsorption capacities with respect to heavy metal ions (62.9 mg g^-1 of Cu²⁺ ion, CuSO₄ 50 mg L^-1) and organic dye molecules (306.7 mg g^-1 of methylene blue and 339.6 mg g^-1 of eriochrome black T, MB/EBT 50 mg L^-1). The polyacrylonitrile fibers provide the skeleton of the membrane, while the graphene oxide and polydopamine endow the membrane with hydrophilicity, which is favorable for the adsorption of pollutants in water. Benefitting from the protonation and deprotonation effects of graphene oxide and polydopamine, the obtained membrane demonstrated promotion of the selective adsorption or desorption of pollutant molecules. This guarantees that the adsorbed pollutant molecules can be desorbed promptly from the membrane through simple pH adjustment, ensuring the reusability of the membrane. After ten adsorption-desorption cycles, the membrane could still maintain a desirable adsorption capacity. In addition, compared with other, similar membranes reported, this composite membrane displays the highest mechanical stability. This work puts forward an alternative strategy for recyclable membrane design and expects to promote the utilization of membrane techniques in practical wastewater treatment.