Nitrate removal for drinking water by FeCl3-oxidated polypyrrole- grafted activated carbon: Adsorption property and mechanism

Developing efficient nitrate removal technologies is crucial for ensuring the safety of drinking water, a polypyrrole-grafted activated carbon (PPy-AC) was synthesized via in situ chemical oxidative polymerization to enhance nitrate adsorption from water. It was showed that the PPy-AC composite featured a maximum adsorption capacity of 13.36 mg NO₃⁻-N/g and exhibited high selectivity toward nitrate in the presence of co-existing anions. The PPy-AC composite exhibited a considerable capacity for adsorbing nitrate over a wide pH range of 3.0–9.0. The absorption performances were well-fitted by the Redlich-Peterson isotherm model, and the adsorption kinetics were well-described by the pseudo-second-order equation. Furthermore, the mass and charge balance calculations showed that 8.4% of the nitrogen atoms in the PPy-AC facilitated the adsorption of nitrate. The mechanisms of nitrate removal by the PPy-AC composite were determined through the electrostatic attraction and ion-exchange process, in which the nitrate ions are replaced by doped chloride ions, and the other N⁺ sites in PPy were occupied by nitrate ions. The PPy-AC is a promising material for the nitrate removal from wastewater.