Adsorption characteristics of trace levels of bromate in drinking water by modified bamboo-based activated carbons

ABSTRACT

This study was undertaken to investigate the adsorption kinetics and isotherms of bromate (BrO₃⁻) on bamboo charcoals that are activated with nitrogen and water vapor. Bamboo-based activated carbon (AC) was dipped in acid and oxidized in a mixture of potassium permanganate and sulfuric acid. Oxidation treatment considerably improved the physicochemical properties of AC, including purity, pore structure and surface nature, significantly enhancing BrO₃⁻ adsorption capacity. AC with many oxygenated groups and a high mesopore volume exhibited a particularly favorable tendency for BrO₃⁻ adsorption. Its adsorption of BrO₃⁻ is best fitted using Langmuir isotherm, and forms a monolayer. A kinetic investigation revealed that the adsorption of BrO₃⁻ by the ACs involved chemical sorption and was controlled by intra-particle diffusion. The competitive effects of natural organic matter (NOM) on AC were evaluated, and found to reduce the capacity of carbon to adsorb BrO₃⁻. Residual dissolved ozone reacted with AC, reducing its capacity to absorb BrO₃⁻. Proper dosing and staging of the ozonation processes can balance the ozone treatment efficiency, BrO₃⁻ formation, and the subsequent removal of BrO₃⁻.

KEYWORDS:

• Activated carbon
• adsorption
• bamboo
• bromate
• natural organic matter
• ozone

Funding

The authors would like to thank the Ministry of Science and Technology, Taiwan, for financially supporting this research under contract no. MOST 103-2221-E-241-003-MY2.