Electron Donor–Acceptor Interaction Strengthens 2-Methylisoborneol Affinity to Nitrogen-Doped Activated Carbon: A Combined Batch and Theoretical Calculation Study

Abstract

2-Methylisoborneol (2-MIB) is an annoying algae-derived odorous compound found worldwide. Due to its low affinity to powdered activated carbon (PAC), great effort has been made to enhance its adsorption performance. Here, we synthesized a series of nitrogen-doped PACs through calcination with urea under various temperatures (400, 600, and 800 °C) and investigated the effects of nitrogen surface functional groups on the adsorption affinity with 2-MIB. The adsorption capacities normalized by the micropore volume of C-600 were 1.4 and 2.2 times greater than those of C-virgin in water with and without dissolved organic matter (DOM), respectively. In addition, under pH 5−9 and hydrophilic/hydrophobic background DOM, C-600 always exhibited higher affinity and greater capacity for 2-MIB. Experiment test and theoretical calculation results indicated that the higher affinity of C-600 to 2-MIB was mainly due to the electron donor−acceptor (EDA) interactions. The unpaired electrons of −OH on 2-MIB act as an electron donor and interact with electron-deficient pyridone, and the low-electron-density group −CH 3 on 2-MIB bound with the electron donor functional group −NH 2 on the carbon. This study was the first to reveal that 2-MIB adsorption could be facilitated by N-doped carbons through EDA interaction, which could provide novel strategies for the development of adsorbents.