Enhancing the Adsorption Performance of 2-Methylisoborneol by Activated Carbon by Promoting Hydrophobic Effects

Abstract

Powdered activated carbon (PAC) is the most widely used adsorbent for removing odorants like 2-methylisoborneol (MIB) for drinking water purification. The hydrophobicity exhibited by the moieties of the carbon structure is known to be important for the adsorption of activated carbon. Here we propose a novel approach for regulating the hydrophobicity of the carbon surface by rearranging carbon atoms without changing the pore structures markedly through thermal transformation using Fe-(NO 3 ) 3 as the catalyst. Five different PACs were transformed into hydrophobic porous carbons (HPCs) with 2.47−3.00 times the adsorption capacity and faster adsorption rates, accompanied by the surface free energy being decreased by 26.67−36.40%, the I G2 / I G1 representing the degree of order being increased by 17.31− 53.68%, the C−C(sp 2 )/C−C(sp 3 ) being increased by 31.9−49.8%, and the oxygen content being decreased by 4.71−8.63%. The increase in ordered planar crystals dominated by sp 2 carbons as well as the decrease in the number of heteroatoms in HPCs might be the main reason for its enhanced adsorption of MIB. Simulation based on reactive force field molecular dynamics indicated that MIB molecules tended to be adsorbed in ordered structures. This study provides a novel angle for improving the surface hydrophobicity of activated carbon, which may lead to the development of high-performance adsorbents.

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

“…Due to the relatively hydrophilic properties of 2-MIB, its adsorption capacity and affinity to PAC are limited. , Therefore, a large amount of PAC is needed to lower the 2-MIB concentration to below the odor threshold, which will lead to high costs, production of large amounts of sludge, and even the clogging of sand filters . Till now, lots of efforts have been made to improve the PAC adsorption performance through modification of the particle size, pore structure, and surface functional group. − For the particle size, Matsui et al and Ando et al proved that the 2-MIB adsorption capacity could be greatly improved with the decrease of the particle size due to shell adsorption. For the pore structure, it has been widely agreed that micropores (0–20 Å) are critical in 2-MIB adsorption .…”

“…20 In addition, a recent work by Yang et al applied iron as a catalyst to regularly arrange sp 2 carbon atoms of the carbon layer, which achieved a 2.47−3.00-fold improvement in 2-MIB adsorption. 9 In addition to the oxygen functional group, the nitrogen functional group of activated carbon is another important structure. Recently, nitrogen doping has been proven to be a useful approach to tailor the adsorption, catalysis, and electronic properties of carbon materials.…”

“…Till now, the hydrophobic force has been generally considered to be the main mechanism for 2-MIB adsorption, and some modifications of the PAC, such as methane and steam treatment, etc., have been applied to improve the 2-MIB adsorption performance . In addition, a recent work by Yang et al applied iron as a catalyst to regularly arrange sp 2 carbon atoms of the carbon layer, which achieved a 2.47–3.00-fold improvement in 2-MIB adsorption …”