Effective and low-toxicity: A membrane cleaning method using peroxymonosulfate catalytic chlorination.

Area of Science:

• Water treatment technologies
• Membrane science and engineering
• Environmental chemistry

Background:

• Chemical membrane cleaning faces challenges in removing irreversible fouling without damaging membrane materials.
• Conventional hypochlorite cleaning generates toxic halogenated by-products, posing environmental and health risks.
• Humic acid fouling is a common issue in water treatment, reducing membrane efficiency.

Purpose of the Study:

• To develop and evaluate a novel cleaning system using peroxymonosulfate and chloride (PMS/Cl-) for irreversible humic acid fouled polyethersulfone (PES) membranes.
• To assess the cleaning efficiency, impact on membrane properties, and environmental safety of the PMS/Cl- system compared to hypochlorite.
• To elucidate the foulant detachment mechanism during the PMS/Cl- cleaning process.

Main Methods:

• Application of a combined peroxymonosulfate and chloride (PMS/Cl-) solution to irreversible humic acid fouled PES membranes.
• Characterization of membrane performance (flux recovery, resistance removal) before and after cleaning.
• Analysis of membrane surface properties and stability through multiple cleaning cycles.
• Investigation of foulant detachment mechanisms using 3D-fluorescence spectroscopy.
• Toxicity assessment through halogenated by-product analysis and acute toxicity tests (Photobacterium phosphoreum T3).

Main Results:

• Achieved 94% flux recovery and 96% resistance removal after 1 hour of PMS/Cl- cleaning.
• Cleaned membrane surface properties were similar to virgin membranes, indicating minimal material impact.
• Demonstrated stable separation performance over multiple fouling and cleaning cycles.
• Identified PMS-catalyzed chlorination as the primary foulant detachment mechanism.
• Exhibited significantly lower toxicity, with reduced halogenated by-products and lower acute toxicity compared to hypochlorite.

Conclusions:

• The PMS/Cl- system offers an efficient and environmentally friendly solution for irreversible organic foulant removal in water treatment.
• This novel cleaning approach minimizes membrane damage and reduces toxic by-product formation.
• The PMS/Cl- system shows great promise for practical applications in water purification processes.