Highly efficient and environmentally benign As(III) pre-oxidation in water by using a solid redox polymer.

Area of Science:

• Environmental Chemistry
• Water Treatment Technologies
• Materials Science

Background:

• Arsenic(III) pre-oxidation to arsenic(V) is crucial for effective water removal.
• Traditional homogeneous oxidants require high doses and can form harmful disinfection byproducts.

Purpose of the Study:

• To develop a heterogeneous oxidant for efficient arsenic(III) pre-oxidation.
• To evaluate the performance and environmental benefits of the novel solid redox polymer (DOX).

Main Methods:

• Covalently binding chlorine to a cation-exchange resin (D001) to create a solid redox polymer (DOX).
• Investigating DOX performance under varying pH, ionic strength, and in the presence of natural organic matter (NOM).
• Assessing disinfection byproduct (DBP) formation and DOX regenerability.
• Conducting column experiments with synthetic groundwater.

Main Results:

• DOX effectively pre-oxidizes arsenic(III) across a pH range of 6-8 and ionic strength up to 0.1 M NaNO3.
• DOX generates significantly fewer DBPs (e.g., chloroform) compared to chlorine.
• The solid matrix of DOX offers protection against NOM interference and steric effects.
• Exhausted DOX can be fully regenerated using NaClO solution for cyclic use.
• Column studies demonstrated a high working capacity (>33,200 bed volumes) for arsenic(III) removal.

Conclusions:

• DOX is a highly efficient and environmentally friendly heterogeneous oxidant for arsenic(III) pre-oxidation in water treatment.
• The regenerability and reduced DBP formation make DOX a sustainable alternative to traditional oxidants.