N-doped activated carbon with hierarchical pores for the efficient removal of perchlorate from water

Abstract

Perchlorate contamination in drinking water is causing serious health issues. N-doped activated carbon with hierarchical pore structure having very high perchlorate adsorption capacity was synthesized from polypyrrole using Pluronic 123 as a template followed by KOH activation. The N 2 adsorption-desorption isotherm of the N-doped activated carbon showed a combination of micro and mesopores, with a high BET surface area of 1720 m 2 g −1 and a total pore volume of 0.869 cm 3 g -1 . Systematic batch experiment studies were conducted to understand the effect of pH, contact time and other interfering anions on the perchlorate adsorption. The equilibrium adsorption data are well described by the Freundlich adsorption model. The adsorption kinetic data is fitted by the pseudo-first-order model with R 2 > 0.99. The adsorption mechanism was established as an electrostatic interaction of positively charged N-doped carbon with perchlorate ion. The spent adsorbent could be regenerated by treatment with 2 M NaCl solution and the regenerated adsorbent retains the perchlorate adsorption capacity of the virgin sample over a large number of adsorption-desorption cycles. The maximum adsorption capacity of 587 mg g −1 obtained was the highest of the reported values suggesting polypyrrole based N-doped activated carbon as a potential adsorbent for the removal of perchlorate from drinking water. • Nitrogen-doped hierarchical porous carbon was synthesized by a soft template approach from polypyrrole (PPy-T-C-K-650). • PPy-T-C-K-650 displayed a high surface area of 1720 m 2 g −1 and large mesopore volume of 0.721 cm 3 g −1 • PPy-T-C-K-650 exhibited a record perchlorate adsorption capacity of 587 mg g −1 • The spent adsorbent showed an excellent regeneration and recycling ability.