Electrospinning Equipment: Investigating ZnO-PAN Composite Membrane for Dye Removal in Wastewater Treatment

With the development of industrialization, wastewater treatment has become a crucial issue in environmental protection. Traditional methods have shortcomings such as low efficiency, high cost, and secondary pollution. Nanotechnology, especially nanocomposite membrane technology, has become a research hotspot due to its advantages of high efficiency, environmental friendliness, and reusability. As a multifunctional semiconductor material, ZnO has photocatalytic activity and antibacterial properties, and its nanostructure performs well in improving membrane flux, antifouling, and antibacterial properties.

In this study, a ZnO - PAN composite membrane was prepared to explore its dye removal efficiency and antifouling performance in wastewater treatment, aiming to provide new solutions for water treatment technology. This research was a collaborative effort by Run Zhao from Yunnan Academy of Ecological and Environmental Sciences, Shirong Zong (corresponding author) from Yunnan Yuntianhua Co., Ltd., Qingfu Ma, Zhenling Xu, and Jiahong Yuan. The relevant results were published under the title "Investigating the Electrocatalytic properties of ZnO - Based composite membrane for dye removal" in Volume 15 of Scientific Reports in 2025 (Scientific Reports, 2025, 15: Article number 6306). The core research findings are presented as follows.

I. Main Research Findings

(1) Development and Performance Enhancement of ZnO - PAN Composite Membrane

In this study, a novel ZnO - PAN composite membrane was developed through an electrospinning machine. By combining zinc oxide (ZnO) with polyacrylonitrile (PAN), the electrocatalytic and permeation properties of the membrane in water treatment were significantly enhanced. The introduction of ZnO greatly improved the water treatment capacity of the membrane, achieving high permeability and an extremely high water flux.

Introduction of ZnO: As a semiconductor material, ZnO has excellent photocatalytic activity and antibacterial properties. In this study, ZnO nanoparticles were uniformly distributed on the surface of PAN fibers, significantly improving the electrocatalytic performance of the membrane. Through physical vapor deposition (PVD) technology, ZnO nanoparticles were successfully deposited on the PAN fiber membrane to form the ZnO - PAN composite membrane. X - ray diffraction (XRD) analysis showed that the main crystal phase of the composite membrane was ZnO, with corresponding crystal plane indices of 100, 002, and 101 (Figure 1).

High Permeability and Water Flux: Experimental results indicated that the water flux of the ZnO - PAN composite membrane was significantly higher than that of the pure PAN membrane. As the deposition time of ZnO increased, the pore size of the membrane gradually decreased, further improving the membrane's rejection rate, but also leading to a reduction in water flux. At the optimal deposition time (10 minutes), the water flux of the composite membrane reached 1,140 L·m⁻²·h⁻¹·bar⁻¹, demonstrating excellent permeation performance (Figure 2).

(2) Electrocatalytic Coupling Experiments

Electrocatalytic coupling experiments revealed that the ZnO - PAN composite membrane exhibited remarkable efficiency in removing small molecule dyes while maintaining a stable water flux, highlighting its great potential in advancing water treatment technology.

Electrocatalytic Performance: The ZnO - PAN composite membrane showed different electrocatalytic performances at different voltages. At 30 V, the dye removal rate of the composite membrane reached a maximum of 99%. The results of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests showed that as the voltage increased, the current response of the composite membrane increased, and the charge transfer impedance decreased, indicating a significant improvement in electrocatalytic performance (Figure 3).

Dye Removal Efficiency: In the electrocatalytic stability test, the initial organic contents were as follows: Congo Red (CR) 28.53 mg/L, Rhodamine B (Rh B) 14.89 mg/L, Sunset Yellow (YS) 9.62 mg/L, Methyl Orange (MO) 11.47 mg/L, and Methylene Blue (MB) 13.16 mg/L. After 10 hours of electrocatalytic treatment, the organic contents of different dye solutions were reduced by 90% (Figure 4).

(3) Long - Term Operational Stability

In addition, the electrocatalytic performance of the composite membrane remained stable during long - term operation, indicating broad application prospects.

Long - Term Stability Test: During the 10 - hour electrocatalytic treatment, the ZnO - PAN composite membrane maintained a stable removal efficiency for different dyes, demonstrating good electrocatalytic stability. Experimental results showed that the removal efficiency of the composite membrane for dyes at different voltages exceeded 90%, indicating good performance during long - term operation.

Mechanical Stability: Electrochemical conditions had a certain impact on the mechanical properties of the composite membrane. As the voltage and treatment time increased, the tensile strength of the membrane gradually decreased. After 20 hours of treatment at 30 V, the tensile strength of the membrane decreased to 28 MPa, indicating that the mechanical properties of the membrane would decline under high - intensity electrochemical conditions (Table 1).

(4) Antifouling Performance

The membrane also demonstrated excellent antifouling capabilities under the influence of an electric field, verifying the effectiveness of electrocatalysis as a sustainable and efficient membrane cleaning method.

Antifouling Performance Test: Through the methylene blue (MB) filtration experiment, it was found that the flux recovery rate of the ZnO - PAN composite membrane under the action of an electric field could reach 85%, and there was less pollutant deposition on the membrane surface with minor changes in pore size, indicating good antifouling properties of the composite membrane (Figure 6).

Antifouling Mechanism: The introduction of ZnO improved the hydrophilicity of the membrane and the number of surface active sites, reducing the adsorption of pollutants on the membrane surface. In addition, the electric field further enhanced the antifouling ability of the membrane. The adhered pollutants could be effectively removed through electrocleaning technology, restoring the membrane flux (Figure 7).

II. Future Research Directions

In this study, a novel ZnO - PAN composite membrane was developed using an electrospinning device. By combining zinc oxide (ZnO) with polyacrylonitrile (PAN), the electrocatalytic and permeation properties of the membrane in water treatment were significantly enhanced. The research results showed that the introduction of ZnO greatly improved the water treatment capacity of the membrane, achieving high permeability and an extremely high water flux. Electrocatalytic coupling experiments revealed that the ZnO - PAN composite membrane exhibited remarkable efficiency in removing small molecule dyes while maintaining a stable water flux, highlighting its great potential in advancing water treatment technology. In addition, the electrocatalytic performance of the composite membrane remained stable during long - term operation, indicating broad application prospects. The membrane also demonstrated excellent antifouling capabilities under the influence of an electric field, verifying the effectiveness of electrocatalysis as a sustainable and efficient membrane cleaning method.

These findings highlight the advantages of the ZnO - PAN composite membrane over traditional materials in terms of permeability, electrocatalytic activity, and antifouling performance, thus promoting the application of composite membranes in water treatment. The innovation of this study lies in the significant improvement of dye removal rate and membrane stability through electrocatalytic coupling technology, demonstrating the potential of the composite membrane in treating complex water matrices. Future research should focus on optimizing the preparation process, material selection, and production technology to further enhance the structural stability, separation performance, and cost - effectiveness of the membrane.

Article Source: https://doi.org/10.1038/s41598-024-75153-2