Removal of phenylarsonic acid compounds by porous nitrogen doped carbon: Experimental and DFT study

Abstract

Phenylarsonic acids are deemed as emerging contaminants, and their removal by carbonaceous materials has aroused wide attentions. However, the adsorption behaviors and mechanisms on nitrogen doped carbon still remain unclear. Herein, nitrogen doped porous carbons (NC-x) for adsorbing p-arsanilic acid and roxarsone were fabricated by hydrothermal and following activation treatment of peanut shell. The results revealed that NC-750 which was activated at 750 °C exhibited high BET surface area of 1331.11 m2/g, total pore volume of 0.97 cm3/g and average pore size of 2.91 nm, and its maximum equilibrium capacities based on Sips model for p-arsanilic acid and roxarsone were 287.3 mg/g and 462.6 mg/g, respectively. The sufficient adsorption space, rich defect structure and high affinity of nitrogen-containing groups endow NC-750 with high adsorption capacities, and the adsorption mechanisms involve with pore-filling, hydrogen bonding and π-π interactions. Density functional theory (DFT) calculation demonstrated that p-arsanilic acid was electron donor while roxarsone was electron acceptor, and graphitic nitrogen was conducive to the π-π interactions while pyrrolic nitrogen and pyridinic nitrogen were preferential for hydrogen bonding interactions. This work can provide reference for understanding the adsorption behaviors and interfacial mechanisms between phenylarsonic acid and nitrogen doped carbonaceous materials.