Polypyrrole-Tailored Activated Carbon for Trifluoroacetate Removal from Groundwater

Positively charged polypyrrole (Ppy) was grafted into coconut-based activated carbon (AC), and this increased trifluoroacetate (TFA, CF3COO-) removal from a groundwater source. For batch isotherm tests, the most favorable Ppy-tailored AC was achieved by applying a 1.5 mol/L pyrrole pretreatment and followed by chemical oxidative polymerization. This Ppy-tailored carbon exhibited a TFA adsorption capacity of 29.0 mg/g, and it offered 8100 bed volume (BV) to 20% breakthrough during rapid small-scale column tests in distilled water that was spiked with 200 ppb TFA. This bed life was more than twice as long as for the pristine AC (4020 BV). This favorable tailoring was attributed to the product's suitable pore structure and highly charged pyrrolic nitrogen ratio (1.37, atomic %), corresponding to 0.29 meq/g positive charge. When processing groundwater that has been spiked with 200 ppb TFA, this Ppy-tailored carbon removed TFA to 20% breakthrough for 780 BV, which was three times longer than the 225 BV for the pristine AC. By employing several characterization protocols, the authors discerned that the pyrrolic nitrogen became less effective at higher pH conditions where the surface charge diminished, and this likewise diminished the TFA removal ability of Ppy-tailored ACs. This Ppy-tailored functionality on AC offers a novel opportunity for removing TFA from groundwater.