N,P Co‐Doped Porous Carbon Derived From Waste Distiller's Grains for Efficient Cr(VI) Removal From Aqueous Solutions

ABSTRACT Biochar exhibits significant potential for application in water pollution control due to its high specific surface area, well‐developed pore structure, abundant raw material availability, and low production cost. In this work, nitrogen and phosphorus co‐doped porous carbons (PNCs) were prepared via a simple physical mixing method followed by high‐temperature activation, using waste distiller's grains as carbon precursor and diammonium hydrogen phosphate as both activating and heteroatom resource. The influence of the activator dosage on the physicochemical properties of the resulting PNCs was investigated. Furthermore, the effects of solution pH, adsorbent dosage, and initial Cr(VI) concentration on Cr(VI) removal efficiency were evaluated. Results demonstrated that PNC‐3 achieves a specific surface area of 722 m 2 ·g −1 and a total volume of 0.45 cm 3 ·g −1 . Notably, PNC‐3 exhibited a high adsorption capacity of 48.97 mg·g −1 for Cr(VI), achieving a removal efficiency of 98.19%. Comprehensive analyses based on isotherm models, kinetic studies, and x‐ray photoelectron spectroscopy (XPS) revealed that the adsorption mechanism primarily involves chemisorption, along with surface complexation and partial reduction of Cr(VI) to less toxic Cr(III). This work presents a facile and sustainable approach for valorizing waste distiller's grains in the development of functional carbon materials for effective heavy metal remediation.