Abstract
Wetland water is an alternative water resource around wetland areas. However, it is typically saline due to seawater intrusion and contains high natural organic matter (NOM) that is challenging to treat. This study evaluated the stability of interlayer-free mesoporous silica matrix membranes employing a dual acid–base catalyzed sol–gel process for treatment of saline wetland water. The silica sols were prepared under a low silanol concentration, dip-coated in 4 layers, and calcined using the rapid thermal processing method. The membrane performance was initially evaluated through pervaporation under various temperatures (25–60 °C) using various feeds. Next, the long-term stability (up to 400 h) of wetland saline water desalination was evaluated. Results show that the water flux increased at higher temperatures up to 6.9 and 6.5 kg·m−2·h−1 at the highest temperature of 60 °C for the seawater and the wetland saline water feeds, respectively. The long-term stability demonstrated a stable performance without flux and rejection decline up to 170 h operation, beyond which slow declines in water flux and rejection were observed due to fouling by NOM and membrane wetting. The overall findings suggest that an interlayer-free mesoporous silica membrane offers excellent performance and high salt rejection (80–99%) for wetland saline water treatments.
Highlights
Indonesia has considerable water resource potential from river, basin, lake, seawater, and wetland water
This study developed and characterized a silica xerogel membrane and evaluated its long-term stability for wetland water desalination via pervaporation
Improvements were obtained in this work, with higher water flux, which could be attributed to the change of the fabrication method through the direct deposition of the active layer onto the alumina substrate
Summary
Indonesia has considerable water resource potential from river, basin, lake, seawater, and wetland water. Silica-based membranes have excellent molecular sieving properties and a simpler fabrication process Their structures have pore sizes in the range of 3–5 Å on the order of the kinetic diameter of the water molecule (dk = 2.6 Å), ideal to hinder the passage of hydrated salt ions (e.g., Na+: dk = 7.2 Å and Cl−: dk = 6.6 Å). Maintaining the pore size of silica-based inorganic membrane is the key to raising great performance and stability for water desalination. Previous studies have demonstrated the long-term stability of silica membrane prepared by the RTP method that is stable for about 100 h of operation for treating wetland saline water [18]. The research and long-term stability evaluation of silica-based membranes for PV is still limited, especially applied to the desalination of wetland saline water. This study developed and characterized a silica xerogel membrane and evaluated its long-term stability for wetland water desalination via pervaporation. Long-term stability tests were conducted to treat actual wetland saline water
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