Effect of Lithium Chloride Concentration in Polymer Solution on Structure and Performance of Polyethersulfone Hollow Fiber Membranes for Oily Wastewater Treatment

Document Type : Research paper

Authors

1 Master of Science in Chemical Engineering, Separation Processes, Gachsaran Branch, Islamic Azad University, Gachsaran, Iran

2 Associate Professor, Department of Chemical Engineering, Gachsaran Branch, Islamic Azad University, Gachsaran, Iran

Abstract

Objective: This study investigates the effect of lithium chloride (LiCl) concentration on the structure and performance of polyethersulfone hollow fiber membranes for the treatment of oily and industrial wastewater. The membranes were fabricated using the phase inversion and wet spinning methods, and different concentrations of LiCl (2 and 4 wt%) were added to the polymer solution.
Materials and methods: The membrane structure was examined using Scanning Electron Microscopy (SEM), and its physical and performance characteristics, including porosity, pore size, water permeability, and oil rejection rate, were evaluated.
Results: The results showed that increasing the LiCl concentration led to the formation of thinner finger-like pores and an increase in their number, thereby improving the surface porosity of the membranes. The membranes containing 4% LiCl exhibited a surface porosity of 437 m²/m³, a pure water flux of 23 L/m²/h, and an oil rejection rate of over 98%, which was attributed to the nanometer-sized pores (36 nm). Furthermore, the addition of LiCl enhanced the mechanical strength of the membranes; the modified membranes with 4% LiCl showed tensile strength of 3.8 MPa (65% higher than membranes without LiCl) and greater resistance to compression (30% flux decline after 3 hours of operation compared to 50% for membranes without LiCl). These mechanical improvements positively impacted the membrane lifespan and the efficiency of the filtration processes.
Conclusions: This study demonstrated that adding LiCl to the polymeric composition improves the structural, functional, and mechanical properties of polyethersulfone membranes, making them a suitable option for separating oil pollutants from industrial wastewater. These membranes can play a significant role in water and wastewater treatment processes, improving efficiency and reducing treatment costs.

Keywords

References

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Journal of Separation Science and Engineering
Volume 17, Issue 2
December 2025
Pages 34-48

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