Thiol-functionalized chitosan filter membrane for chloramine conversion in water treatment

Overview

Chloramine is widely used as a secondary disinfectant in municipal water systems, but it is difficult to remove and can damage downstream ultrafiltration membranes. This technology introduces thiol (-SH) functional groups onto a polymer filter material that chemically react with chloramine, converting it into compounds that can be readily removed by a secondary ultrafiltration or nanofiltration layer. The approach is based on the same chemical principle by which chloramine deactivates bacteria—reaction with sulfhydryl groups—and applies it to water treatment in a controlled, replaceable filter format.

The proposed solution uses chitosan functionalized with thioglycolic acid to introduce -SH groups onto the polymer backbone. This modified chitosan is then fabricated into a filter membrane that can be deployed upstream of existing ultrafiltration or nanofiltration membranes. Once the thiol groups are consumed, the filter can be easily swapped out, simplifying maintenance compared with chemical dosing or activated carbon alternatives.

Technical specifications

Core chemistry:

• Thiol (-SH) groups covalently attached to chitosan via thioglycolic acid functionalization
• Reaction with chloramine converts it into compounds removable by nanofiltration or ultrafiltration
• Designed for use in dead-end filtration configurations

Performance targets under investigation:

• Conversion efficiency of chloramine across varying water chemistries, including different pH, salinity, and total hardness conditions
• Operational lifetime of the thiol-functionalized filter before replacement is required
• Compatibility and performance when coupled with downstream ultrafiltration or nanofiltration membranes

Material advantages:

• Chitosan is an abundant, low-cost biopolymer
• Functionalization method is scalable and adaptable to other polymer membrane substrates
• Filter format supports straightforward replacement once thiol sites are exhausted

Technology readiness level

This is an early-stage research and development effort. The underlying concept is grounded in the principal investigator's prior experience preparing functionalized filtration materials for organic and inorganic contaminant removal. Planned validation activities include fabricating the thiol-modified chitosan membrane, integrating it with secondary filtration membranes, and measuring chloramine conversion efficiency and filter lifetime in dead-end filtration experiments over an estimated one-year study period. The work requires funding for materials, reagents, and key personnel before performance data can be generated and commercial readiness assessed.