Selective removal of dibenzothiophene from commercial diesel using manganese dioxide-modified activated carbon: a kinetic study

Enhanced adsorption of aqueous acetone by modified powdered activated carbon

Acetone, a small molecule organic compound, is freely soluble and volatile. To improve the removal rate of acetone, three different types of powdered activated carbon (PAC) were compared and then modified with formic acid and NaOH to optimize the adsorption capacities of PAC. The adsorption mechanism and the effect of physical-chemical properties of PAC to the adsorption were clarified. Results show that PAC produced from wood performed best adsorption capacities. The pseudo-second-order model and the Freundlich model accurately described the adsorption behaviour, while lower temperature was more conducive to the adsorption process. PAC giving a higher acetone adsorption capacity had a larger specific surface area, a richer micropore structure, a larger micropore volume, a smoother surface, with more acidic, oxidizing functional groups. The adsorption removal efficiency of modified PACs with formic acid was improved from 60.89% to 82.93%, while NaOH modification decreased the adsorption capacity. The positive effect of formic acid was attributed to the formation of novel acidic oxygen-containing functional groups, which was supported from the NaOH treatment that removed original acidic oxygen-containing functional groups, contrarily the formation of novel alkaline reducing functional groups did not restore the acetone adsorption capacity. We conclude that wooden PAC is a suitable adsorbent for acetone, in particular after pretreatment with formic acid.

One-pot synthesis of purple benzene-derived MnO2-carbon hybrids and synergistic enhancement for the removal of cationic dyes

MnO₂-carbon hybrid (MnO₂-C-PBz) was simultaneously synthesized by a one-step solution plasma process (SPP) using a single precursor referred to as "purple benzene", which was derived from the K⁺(dicyclohexano-18-crown-6 ether) complex. To clarify the synergistic effects on the cationic dye removal, MnO₂-free carbon and carbon-free MnO₂ samples were concurrently investigated. The results of adsorption for cationic dyes (methylene blue (MB) and rhodamine B (Rh B)) and anionic dye (methyl orange (MO)) revealed remarkably high affinity for cationic dyes. In particular, MnO₂-C-PBz exhibited the highest adsorption capacity for MB, i.e., ~3 times greater than that of the others. In addition, MnO₂-C-PBz exhibited a rapid, high decolorization ability at C₀ = 10 mg L^-1 (within a few seconds, ~99%) and at C₀ = 100 mg L^-1 (within 30 min, ~81%), and the theoretical maximum monolayer adsorption capacity was 357.14 mg g^-1 as calculated from the Langmuir adsorption isotherm equation. Furthermore, compared with carbon-free MnO₂, MnO₂-C-PBz exhibited quite a good cyclic stability. We expect that our findings give rise to the understanding of the synergistic effects of MnO₂-carbon hybrid, as well as role of each components for the cationic dye adsorption, and may open an innovative synthesis approach to inorganic-organic hybrid materials.

Synthesis of silver sulfide modified carbon materials for adsorptive removal of dibenzothiophene in n-hexane

Carbon nanotube (CNT) and graphene oxide (GO) as common nanostructures were modified with silver sulfide (Ag₂S) using chemical vapor deposition. The raw and modified materials were tested for the removal of Dibenzothiophene (DBT) from a model fuel in batch mode adsorption experiments. The maximum adsorption capacities of DBT were 52.18 and 49.65 mg g^-1, using CNT-Ag₂S and GO-Ag₂S, respectively. The adsorption isotherm was modeled using Freundlich, Langmuir and Temkin models using linear and non-linear regression. The squared correlation coefficient (R²) and HYBRID error function were used to determine the best adsorption model. IR spectroscopy was used to study the DBT adsorption mechanism, and it was found that the DBT molecules lie flat on the surface of the developed adsorbents. Significant improvement was achieved in the adsorption of DBT using CNT-Ag2S and GO-Ag₂S, where the maximum adsorption capacity increased by 127% and 117% respectively, which indicates a stronger interaction between DBT and the modified adsorbents.

Phenolic resin-derived activated carbon-supported divalent metal as efficient adsorbents (M-C, M=Zn, Ni, or Cu) for dibenzothiophene removal

The adsorption process and mechanism of dibenzothiophene (DBT) over metal-loaded phenolic resin-derived activated carbon (PR-AC) were firstly reported in this work. The metal component (Zn, Ni, or Cu) was respectively introduced to PR-AC support via an impregnation method. The effects of adsorbent component, initial DBT concentration, liquid hourly space velocity (LHSV), adsorption time, and adsorption temperature on the adsorption capacity of the adsorbents were systematically investigated. Furthermore, the adsorption mechanism was discussed by analyzing the properties of adsorption product and saturated adsorbent as well as adsorption kinetics. Experimental results indicate that the PR-AC-loaded metal adsorbents, especially with Zn, present much higher DBT adsorption capability than that of pure PR-AC support. The DBT removal rate over PR-AC-loaded Zn (Zn²⁺ = 0.2 mol L^-1) reaches 89.14 %, which is almost twice higher than that of pure PR-AC (45.6 %). This is due to the π-complexation between DBT and metal ions (dominating factor) and the weakening of the local hard acid sites over PR-AC. The multi-factor orthogonal experiment shows that the DBT removal rate over PR-AC-loaded Zn sample achieved 92.36 % in optimum conditions.