Arsenic removal by iron-modified activated carbon

Area of Science:

• Environmental Science
• Materials Science
• Water Treatment Technology

Background:

• Iron-impregnated activated carbons show high efficacy in arsenic removal.
• Arsenic species (arsenate, arsenite) adsorb onto iron oxyhydroxide surfaces via complexation.
• Optimizing iron loading and accessibility is key for efficient arsenic sorption.

Purpose of the Study:

• To maximize iron loading within activated carbon pores.
• To enhance the accessibility of iron for arsenic sorption.
• To evaluate the performance of iron-tailored carbons in arsenic removal.

Main Methods:

• Surface oxidation of activated carbon using HNO3/H2SO4 or HNO3/KMnO4.
• Iron impregnation via precipitation or iron salt evaporation.
• Rapid small-scale column tests (RSSCTs) using groundwater with varying arsenic concentrations and pH.

Main Results:

• Surface oxidation increased iron loading to 7.6-8.0%, maintaining arsenic below 10 ppb for 12,000 bed volumes.
• Optimized iron impregnation achieved 9-17% internal loading and up to 33.6% total loading.
• Iron-tailored carbons demonstrated extended arsenic removal capacity, reaching 25,000-34,000 bed volumes to breakthrough.

Conclusions:

• Surface modification and optimized iron impregnation significantly improve activated carbon performance for arsenic removal.
• High iron loading enhances arsenic adsorption capacity and extends the operational life of water treatment media.
• Further research may be needed to address potential iron leaching at very high loading percentages.