Effect of Polarity of Activated Carbon Surface, Solvent and Adsorbate on Adsorption of Aromatic Compounds from Liquid Phase

Abstract

In this study, introduction of acidic functional groups onto a carbon surface and their removal were carried out through two oxidation methods and outgassing to investigate the adsorption mechanism of aromatic compounds which have different polarity (benzene and nitrobenzene). Adsorption experiments for these aromatics in aqueous solution and n-hexane solution were conducted in order to obtain the adsorption isotherms for commercial activated carbon (BAC) as a starting material, its two types of oxidized BAC samples (OXs), and their outgassed samples at 900°C (OGs). Adsorption and desorption kinetics of nitrobenzene for the BAC, OXs and OGs in aqueous solution were also examined. The results showed that the adsorption of benzene molecules was significantly hindered by abundant acidic functional groups in aqueous solution, whereas the adsorbed amount of nitrobenzene on OXs gradually increased as the solution concentration increased, indicating that nitrobenzene can adsorb favourably on a hydrophilic surface due to its high dipole moment, in contrast to benzene. In n-hexane solution, it was difficult for benzene to adsorb on any sample owing to the high affinity between benzene and n-hexane solvent. On the other hand, adsorbed amounts of nitrobenzene on OXs were larger than those of OGs in n-hexane solution, implying that nitrobenzene can adsorb two adsorption sites, graphene layers and surface acidic functional groups. The observed adsorption and desorption rate constants of nitrobenzene on the OXs were lower than those on the BAC due to disturbance of diffusion by the acidic functional groups.

An investigation on the characterization of activated carbon from areca leaves and their adsorption nature towards different dyes

“…It is well known fact that adsorption mechanism mainly depends on the factors like pore structure, surface chemistry and polarity of solvents (Goto et al, 2015). Result showed that the behaviour of PALC found to be different than that of MALC towards dye adsorption.…”

Detoxification of Pesticide-Containing Wastewater with FeIII, Activated Carbon and Fenton Reagent and Its Control Using Three Standardized Bacterial Inhibition Tests

“…Such compounds tend to adsorb onto polar iron hydroxide sludge [52]. On PAC, which surface is preferred by non-polar compounds [53], therefore, no accumulation of polar phosphorus compounds occurred. The Fenton method also showed significantly higher efficiency with respect to the COD removal (95%) compared to the other two methods.…”

Comparative Study of Toluene and Hexane Adsorption on Activated Carbons From Gas and Liquid Phase. Enthalpy and Isotherms

“…Langmuir Freundlich a monolayer, due to two different behaviors: in the toluene-CST system, due to the high basicity and a high percentage of microporosity, toluene can be arranged in the micropores of the activated carbon, generating π-π-type interactions (Goto et al, 2015), having sites with which to generate van der Waalstype interactions and the sufficient amount of micropores to be arranged in a monolayer until reaching the saturation pressure, retaining a high amount of adsorbate. While in the case of hexane-CS, this sample is the one that presents the greatest heterogeneity with respect to surface chemistry and the lowest values of surface area and micropore volume, due to this and added to the fact that hexane tends to be arranged as an elongated cylinder (Wang et al, 2015), the formation of a monolayer can be reached at low relative pressures with a much lower amount of this adsorbate compared to toluene, which is evidenced in the adsorption isotherms since the amount adsorbed in the monolayer for toluene is 4.524 mmol g −1 , while for hexane is 0.052 mmol g −1 .…”

“…Langmuir Freundlich affinity by ππ interactions (Goto et al, 2015), generating less adsorbate-adsorbent interaction, mainly with toluene. Regarding to the samples, Figure 12 shows the immersion enthalpies of pure solvents and toluene-hexane mixtures in function of the molar fraction of toluene and the total acidity and basicity of samples.…”