Using low-energy PTFE with AGMD at high recovery for sustainable seawater and wastewater reclamation

Abstract

Desalination is an imperative measure to address the global water scarcity issue, and one effective approach for desalination is through membrane distillation. This method of desalination is a recent innovation that exploits the temperature gradient between a hot feed solution and a cold permeate side to transfer water vapour across a porous hydrophobic membrane. Consequently, the outcome of this process is the production of high-quality water that is free from minerals and salts. Notably, membrane distillation offers several advantages compared to other desalination methods, such as reduced energy consumption and the capacity to treat highly concentrated saline solutions. These attributes make membrane distillation appealing for desalinating various water sources, including seawater, brackish water, and wastewater. However, this technology has limitations, including low recovery and fouling of the membrane. The discharge of high-saline seawater and wastewater contaminants from landfills can result in severe health consequences for humans, such as cancer, acute toxicity, and genetic damage. While membrane distillation (MD) has demonstrated potential in eliminating contaminants from this form of seawater and landfill leachate wastewater, conventional chemical cleaning approaches are inadequate in removing certain hazardous pollutants, including nickel, barium, and magnesium. This study employed a cleaning approach utilizing hot deionized water and hydrogen peroxide (H2O2), displaying remarkable effectiveness in removing fouling caused by elevated silane levels in seawater and landfill leachate wastewater contaminants without impacting membrane rejection rates. This in-situ cleaning technique is efficient in energy consumption, cost-effective, and environmentally friendly since it can be reused multiple times without releasing harmful chemicals into the environment. Compared to traditional acid or base cleaning methods, this approach has proven to be more efficient in eliminating hazardous pollutants from high-silane seawater and wastewater contaminants. The present study investigates the impact of various factors on membrane distillation performance, namely temperature, (PTFE) membrane material, the concentration of feed solution, and coating (PTFE) by anti-fouling material. The research is carried out at two different temperatures, 55 °C and 65 °C while utilizing different types of membranes with recovery rates ranging from 80% to 90%. The aim is to identify the optimal conditions for membrane distillation and assess each membrane's potential for water desalination and wastewater purification. The study also examines the performance of (PTFE), Graphene-coated (PTFE), and Tin Sulfide-coated (PTFE) membranes in air-gap membrane distillation. The cleaning technique for fouled membrane involves flushing with (DI) water for 60 min, followed by (H2O2) at 3% concentration for 30 min as chemical cleaning. The study's findings provide valuable insights into developing more efficient and cost-effective membrane distillation systems. Furthermore, the outcomes of this research contribute to the ongoing efforts to address the global water crisis by identifying the potential suitability of membrane distillation for various applications such as seawater and brackish water desalination, wastewater treatment, and controlling fouling on the membrane surface. This thesis comprehensively describes the experimental methodology, materials used, results obtained, and a discussion of their implications. The conclusion summarizes the essential findings and provides recommendations for future research in this field.