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US-12623171-B1 - Method of cleaning a fouled reverse osmosis membrane

US12623171B1US 12623171 B1US12623171 B1US 12623171B1US-12623171-B1

Abstract

A method of cleaning a fouled reverse osmosis (RO) membrane using a comb-shaped polymer which includes dissolving the comb-shaped polymer and a base in water to form a solution, contacting the fouled RO membrane with the solution to produce a cleaned RO membrane. The comb-shaped polymer includes reacted units of poly(isobutylene-alt-maleic anhydride) and an oligoethylene amine where, the oligoethylene amine is triethylenetetramine, tetraethylene pentaamine, or pentaethylenehexamine.

Inventors

  • Majad KHAN
  • Asif MATIN
  • Nadeem BAIG

Assignees

  • KING FAHD UNIVERSITY OF PETROLEUM AND MINERALS

Dates

Publication Date
20260512
Application Date
20251121

Claims (19)

  1. 1 . A method of cleaning a fouled reverse osmosis membrane, comprising: dissolving a comb-shaped polymer and a base in water to form a solution; contacting the fouled reverse osmosis membrane with the solution to produce a cleaned reverse osmosis membrane, wherein the comb-shaped polymer comprises reacted units of poly(isobutylene-alt-maleic anhydride) and an oligoethylene amine, wherein the oligoethylene amine is one or more selected from the group consisting of triethylenetetramine, tetraethylene pentaamine, and pentaethylenehexamine, and wherein the fouled reverse osmosis membrane comprises a reverse osmosis membrane and a foulant.
  2. 2 . The method of claim 1 , wherein the concentration of the comb-shaped polymer in the solution is 2-3 gL −1 .
  3. 3 . The method of claim 1 , wherein the foulant comprises one or more polysaccharides.
  4. 4 . The method of claim 1 , wherein the pH of the solution is 9-12.
  5. 5 . The method of claim 1 , wherein the solution is contacted with the fouled reverse osmosis membrane for 40-60 hours.
  6. 6 . The method of claim 1 , wherein the solution is contacted with the fouled reverse osmosis membrane at a temperature of 30-50° C.
  7. 7 . The method of claim 1 , wherein the cleaned reverse osmosis membrane has a flux recovery of 55-95% compared to the fouled reverse osmosis membrane before the contacting.
  8. 8 . The method of claim 1 , wherein the cleaned reverse osmosis membrane has a Ca 2+ presence of less than 2 wt. %.
  9. 9 . The method of claim 1 , wherein the cleaned reverse osmosis membrane has a carbon to oxygen ratio of 1.5-5 to 1.
  10. 10 . The method of claim 1 , wherein the cleaned reverse osmosis membrane has a sulfur content of 3-10 wt. %.
  11. 11 . The method of claim 1 , wherein the cleaned reverse osmosis membrane has an isoelectric point of 3-4.
  12. 12 . The method of claim 1 , wherein the reverse osmosis membrane is a ceramic membrane.
  13. 13 . The method of claim 1 , further comprising; mixing poly(isobutylene-alt-maleic anhydride) (PIMA) and a first organic solvent to form a solution; mixing an oligoethylene amine and a second organic solvent to form a mixture; adding the solution to the mixture and stirring to form the comb-shaped polymer, wherein the oligoethylene amine is one or more selected from the group consisting of triethylenetetramine, tetraethylene pentaamine, and pentaethylenehexamine.
  14. 14 . The method of claim 12 , wherein the first organic solvent is dimethyl sulfoxide.
  15. 15 . The method of claim 12 , wherein the second organic solvent is dimethyl sulfoxide.
  16. 16 . The method of claim 12 , wherein the solution and the mixture are stirred at a temperature of 40-80° C.
  17. 17 . The method of claim 12 , wherein the solution and the mixture are stirred for 60-90 hours.
  18. 18 . The method of claim 12 , wherein the molar ratio of the oligoethylene amine to the PIMA is 18-22 to 1.
  19. 19 . The method of claim 12 , wherein the degree of pendent oligoethylene amine conjugation is 90-100%.

Description

BACKGROUND Technical Field The present disclosure is directed to a method of cleaning a fouled reverse osmosis (RO) membrane using a polymer, more preferably, with a comb-shaped polymer including poly(isobutylene-alt-maleic anhydride) and an oligoethylene amine groups. Description of Related Art The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. Membrane-based technologies are gaining wide acceptance in water and wastewater treatment, with RO emerging as the dominant method for seawater desalination and wastewater reclamation. Nonetheless, membrane fouling caused by natural organic matter remains an important challenge, as it leads to decreased permeability, increased solute leakage, and consequently higher operational and maintenance costs. Conventional cleaning relies on harsh chemical agents such as acids, alkalis, and surfactants, which act via hydrolysis, solubilization, and chelation. Despite restoring performance, such practices damage the active layer of membranes and generate environmentally hazardous waste streams. Moreover, existing cleaning agents often fail to completely remove hydrophobic foulants, resulting in incomplete recovery. Recent research has explored eco-friendly alternatives. For instance, Tian et al. (2022) [Tian, C., et al. Environ. Sci. Technol, 56 (2022), 12563] used a green solvent, methyl-5-(dimethylamino)-2-methyl-5-oxopentanoate (MDMO), achieving nearly 100% flux recovery in PVDF membranes, while Xiao et al. (2024) [Xiao, H., et al. J. Hazard Mater. 462, (2024) 132827] demonstrated a PMS/Cl− cleaning system restoring 94% flux in humic acid-fouled ultrafiltration membranes. These studies highlight the potential of green cleaning but were mostly conducted on ultrafiltration membranes including polyethersulfone (PES) and polyvinylidene fluoride (PVDF), leaving their compatibility with PA-based RO membranes uncertain. Thus, despite progress, eco-friendly cleaning agents need further investigation for RO membranes, particularly regarding their chemical compatibility, operational feasibility, and performance under practical conditions such as pH and temperature variations. Accordingly, it is one object of the present disclosure to provide a method of developing a polymer-based material for water treatment applications that may overcome the limitations of existing membranes, including fouling, reduced performance after cleaning, and environmental concerns associated with conventional chemical treatments. SUMMARY In an exemplary embodiment, a method of cleaning a fouled reverse osmosis (RO) membrane using a comb-shaped polymer is described. The method includes dissolving the comb-shaped polymer and a base in water to form a solution, contacting the fouled RO membrane with the solution to produce a cleaned RO membrane. The comb-shaped polymer includes reacted units of poly(isobutylene-alt-maleic anhydride) and an oligoethylene amine where, the oligoethylene amine is one or more selected from the group consisting of triethylenetetramine, tetraethylene pentaamine, and pentaethylenehexamine. In some embodiments, the concentration of the comb-shaped polymer in the solution is 2-3 gL−1. In some embodiments, the pH of the solution is 9-12. In some embodiments, the solution is contacted with the fouled RO membrane for 40-60 hours. In some embodiments, the solution is contacted with the fouled RO membrane at a temperature of 30-50° C. In some embodiments, the cleaned RO membrane has a flux recovery of 55-95% compared to the fouled RO membrane before the contacting. In some embodiments, the cleaned RO membrane has a Ca2+ presence of less than 2 wt. %. In some embodiments, the cleaned RO membrane has a carbon to oxygen ratio of 1.5-5 to 1. In some embodiments, the cleaned RO has a sulfur content of 3-10 wt. %. In some embodiments, the cleaned RO membrane has an isoelectric point of 3-4. In some embodiments, the RO membrane is a ceramic membrane. In another exemplary embodiment, a method of synthesizing a comb-shaped polymer is described. The method includes mixing poly(isobutylene-alt-maleic anhydride) (PIMA) and a first organic solvent to form a solution, mixing an oligoethylene amine and a second organic solvent to form a mixture. The method further includes adding the solution to the mixture and stirring to form the comb-shaped polymer. The oligoethylene amine is one or more selected from the group consisting of triethylenetetramine, tetraethylene pentaamine, and pentaethylenehexamine. In some embodiments, the first organic solvent is dimethyl sulfoxide. In some embodiments, the second organic solvent is dimethyl sulfoxide. In some embo