Adsorption behavior of engineered carbons and carbon nanomaterials for metal endocrine disruptors: Experiments and theoretical calculation

Abstract

Adsorption behaviors and mechanisms of metal endocrine disruptors (Pb2+, Cd2+, and Hg2+) by pyrogenic carbonaceous materials including engineered carbons (biochar and activated carbon) and carbon nanomaterials (multi-walled carbon nanotubes and graphene oxide) have been investigated by experimental and density functional theory (DFT) studies. The adsorption isotherms of metal endocrine disruptors on carbonaceous materials were better fitted by Langmuir models. The adsorption capacities were in the order as follows: GO > BC600 > BC300 > CNT > AC for Pb2+, GO > BC300 > AC > BC600 > CNT for Cd2+, and GO > BC300 ≥ AC > CNT > BC600 for Hg2+, respectively. The DFT-computed binding energy (kcal/mol) of different oxygen-containing functional groups with metal endocrine disruptors followed the orders: (ⅰ) CM–COC–Pb (−136.70) > CM-COO--Pb (−91.58) > CM–CO–Pb (−33.57) > CM–OH–Pb (−4.69), (ⅱ) CM-COO--Cd (−45.91) > CM–COC–Cd (−4.49) > CM–OH–Cd (−3.68) > CM–CO–Cd (1.08), (ⅲ) CM-COO--Hg (−25.51) > CM–COC–Hg (−3.58) > CM–OH–Hg (−0.63) > CM–CO–Hg (0.23). And –COC– has the highest binding energy for Pb2+, whereas –COC– has much lower binding energy for Cd2+ and Hg2+. Comprehensively considering DFT calculations, competitive adsorption results and the cost analysis, this work may provide insights into the design of selective adsorbent for specific contaminant.