Estimating the Reducing Power of Carbon Nanotubes and Granular Activated Carbon Using Various Compounds

• Main Authors: Heesoo Woo, Ilho Kim, Saerom Park
• Format: Article
• Language: English
• Published: MDPI AG 2021-07-01
• Series: Water
• Subjects: multi-wall carbon nanotubes; granular activated carbon; reduction; adsorption; chromium; iron
• Online Access: https://www.mdpi.com/2073-4441/13/14/1959

Determining the degree of the reducing power of multi-walled carbon nanotubes (MWCNTs) and granular activated carbon (GAC) enables their effective application in various fields. In this study, we estimate the reducing power of carbon nanotubes (CNTs) and GAC by measuring the reduction degree of various compounds with different reduction potentials. MWCNTs and GAC materials can reduce Cr(VI), Fe(III) and PMo₁₂O₄₀³⁻, where the reduction potentials range from +1.33 V to +0.65 V. However, no reduced forms of PW₁₂O₄₀³⁻ and SiW₁₂O₄₀⁴⁻ compounds were detected, indicating that the reducing power of MWCNTs and GAC is insufficient for reduction potentials in the range +0.218 V to +0.054 V. MWCNTs exhibit a short reduction time (5 min), whereas GAC exhibits a gradually increasing reduction degree of all the compounds assessed until the end of the reaction. This indicates a higher reduction degree than that of MWCNTs systems. Acidic initial pH values favor reduction, and the reduction degree increases as the pH becomes lower than 4.0. Moreover, large quantities of MWCNTs and GAC increase the concentrations of the reduced compounds.