Significant role of counterion for lead(Ⅱ) ion adsorption on carbon pore surface. (30th August 2022)

• Record Type: Journal Article
• Authors: Horikawa, Toshihide; Okamoto, Miku; Kuroki-Matsumoto, Ayaka; Yoshida, Ken
• Is Part Of: Carbon. Volume 196(2022)
• Page Start: 575
• Page End: 588
• Publication Date: 2022-08-30
• Subjects: Metal ion adsorption -- Activated carbon -- Anions -- HSAB theory -- Molecular dynamics simulation; AC activated carbon -- MD molecular dynamics -- G/D graphite/carbon defect ratio -- HSAB hard and soft acids and bases; Carbon -- Periodicals; Carbone -- Périodiques; Koolstof; Toepassingen; Electronic journals; 546.681
• DOI: 10.1016/j.carbon.2022.05.031
• Languages: English
• ISSNs: 0008-6223

Abstract

Abstract: We have presented a predictive tool for describing Pb 2+ adsorption on activated carbon (AC). Based on the correlation between the G/D ratio and the adsorbed amount of Pb 2+ obtained in our previous study (Kuroki et al., 2019), we have further validated the predictive tool by carefully analyzing the results of lead ion adsorption on different AC samples in the present study. Our results show that the method can predict the amount of Pb 2+ adsorption within 10%, which corroborates our previous interpretation based on the hard and soft acids and bases theory. Molecular dynamic simulations were carried out to resolve the role of the counter anion and how it affects the configuration and the amount adsorbed of Pb 2+ ions on the non-polar graphite surface of AC. The simulation results showed that when the counterion is NO3 −, the adsorption of Pb 2+ is enhanced by the electrostatic interactions of lead ions with adsorbed NO3 − because NO3 − is attracted strongly to the surface of graphite. This unique feature of adsorbed NO3 − is substantiated with the use of Cl − as the counter anion, which did not show any significant adsorption of lead ions because chlorine ions are not strongly attracted to the surface of graphite. This mechanism is presented for the first time in the literature, and it can pave the path to exploring and understanding the complex phenomena of ions in the aqueous phase onto activated carbon. Graphical abstract: Image 1 Highlights: High predictability of the correlation between Pb 2+ adsorption and G/D ratio. Mechanism of adsorption of ions in carbon pores is derived with MD simulation. Adsorption of Pb 2+ is enhanced with NO3 − as the counter anion. Cl − is not effective in Pb 2+ adsorption due to its weaker attraction to graphite.