The nature and kinetics of the adsorption of dibenzothiophene in model diesel fuel on carbonaceous materials loaded with aluminum oxide particles

Adsorption of dibenzothiophene in model diesel fuel by amarula waste biomass as a low-cost adsorbent

The effectiveness of the adsorption process is determined by the type of adsorbent used, but some adsorbents require a significant amount of processing to achieve the desired quality, and this has become a drawback economically and environmentally. This study focused on mitigating the issue of waste management and land pollution by using amarula waste biomass, which is a low-cost adsorbent that is obtained from the industrial waste by-product. The amarula shell (AmSh) waste was found to have a higher adsorption efficiency of 30 ± 3% compared to the amarula seed (AmSe) waste and the amarula fruit (AmWa) waste, which had 19 ± 5% and 9.5 ± 0.7% efficiency, respectively. It was found that the amarula waste biomass performed better at lower adsorption temperatures. The adsorption capacity was found to decrease with an increase in the quantity of the biomass. Kinetic models were applied to the experimental data. Thermodynamic parameters were also studied to determine the spontaneity of the adsorption process. The characteristics of both the fresh and used amarula waste biomass was analyzed by using Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy with Energy Dispersive Spectroscopy (FESEM-EDS), Brunauer-Emmett-Teller (BET) and Thermogravimetric Analysis (TGA). It was then concluded that cellulose and hemicellulose structures in amarula waste biomass played a major role in reducing the content of dibenzothiophene in model diesel fuel.

V2O5, CeO2 and Their MWCNTs Nanocomposites Modified for the Removal of Kerosene from Water

In this paper, the application of multiwalled carbon nanotubes (MWCNTs) based on metal oxide nanocomposites as adsorbents for the removal of hydrocarbons such as kerosene from water was investigated. Functionalized MWCNTs were obtained by chemical oxidation using concentrated sulfuric and nitric acids. V₂O₅, CeO_2, and V₂O₅:CeO₂ nanocomposites were prepared using the hydrothermal method followed by deposition of these oxides over MWCNTs. Individual and mixed metal oxides, fresh MWCNTs, and metal oxide nanoparticle-doped MWCNTs using different analysis techniques were characterized. XRD, TEM, SEM, EDX, AFM, Raman, TG/DTA, and BET techniques were used to determine the structure as well as chemical and morphological properties of the newly prepared adsorbents. Fresh MWCNTs, Ce/MWCNTs, V/MWCNTs, and V:Ce/MWCNTs were applied for the removal of kerosene from a model solution of water. GC analysis indicated that high kerosene removal efficiency (85%) and adsorption capacity (4270 mg/g) after 60 min of treatment were obtained over V:Ce/MWCNTs in comparison with fresh MWCNTs, Ce/MWCNTs and V/MWCNTs. The kinetic data were analyzed using the pseudo-first order, pseudo-second order, and intra-particle diffusion rate equations.

Synthesis and characterization of AFe2O4 (A: Ni, Co, Mg)-silica nanocomposites and their application for the removal of dibenzothiophene (DBT) by an adsorption process: kinetics, isotherms and experimental design

The kinetics, equilibrium, and statistical aspects of the sulfur removal process from hydrocarbon fuels by AFe₂O₄–silica nanocomposites (A: Ni, Mg, and Co) have been investigated in the present study. Nanocomposites were prepared via the auto-combustion sol–gel method and then employed in the adsorptive desulfurization (ADS) process. Next, the prepared samples were characterized by different analytical methods including XRD, SEM, TEM, FT-IR, TGA, and BET. The contributions of conventional parameters including adsorbent dosage and contact time were then studied by central composite design (CCD) under response surface methodology (RSM). Based on the statistical investigations, optimum conditions for ADS were an adsorbent dosage of 7.82 g per 50 ml of the model fuel and a contact time of 32 min. The adsorption amounts reached 38.6 mg g⁻¹ for DBT. The quadratic model was applied for the analysis of variance. Based on the experimental data, the pseudo-first-order (PFO) model could explain the adsorption kinetics of the compounds. Furthermore, the Langmuir isotherm demonstrated considerable agreement with the experimental equilibrium data. According to the results, the NiFe₂O₄–SiO₂ nanocomposite showed the best performance compared to other compounds. The sulfur removal efficiency increased from 63 to 94% upon increasing the NiFe₂O₄–SiO₂ dosage from 3 to 9 g per 50 ml of the model fuel.

Among the methods for adsorptive desulfurization (ADS) represents a promising alternative method of removing sulfur by adsorption.

Desulfurization studies of liquid fuels through nickel-modified porous materials from Pongamia pinnata

Abstract

A new biomass-based carbonaceous adsorbent has been developed from Pongamia pinnata and its effect upon nickel modification- and adsorption-coupled ultrasonication was investigated. Adsorption experiment of the model oil constituting 50 ppm dibenzothiophene in cyclohexane showed the maximum capacity as 8.11, 13.36, and 17.15 mg·g−1 for the commercial carbon DARCO, virgin bio-adsorbent PP, and nickel-modified adsorbent Ni@PP, respectively, with the time required for attaining equilibrium being the fastest in Ni@PP (120 min). The significant effect of ultrasonication was in attaining faster kinetics where ~ 96–98% removal was achieved in only 30 min. Also, the developed adsorbents had a very good specific surface area of 915 and 677 m2·g−1, respectively, for PP and Ni@PP. Investigation of the effect of higher initial sulfur concentration (200 ppm) indicated the significance of Ni modification, where a very high capacity of 66.18 mg·g−1 for Ni@PP was attained against 30.90 mg·g−1 for PP and 13.18 mg·g−1 for DARCO. Ni@ PP was also effective for the simultaneous removal of more refractory sulfur fractions from multicomponent model fuel systems and exhibited good regeneration ability till the fourth cycles or more. Cost estimation showed that the developed adsorbents are relatively ten times cheaper than commercial carbon, while the fixed-bed study indicated a breakthrough time of 250 min and 270 min for PP and Ni@PP, respectively.

Graphic abstract

Enhanced Adsorptive Desulfurization Using Mongolian Anthracite-Based Activated Carbon

This study reports usage of Mongolian anthracite-based porous activated carbons (PMACs), namely, PMAC 1/3 and PMAC 1/4 for model diesel fuel desulfurization, having 500 ppmw of dibenzothiophene (DBT) in n-heptane. Further, the effects of contact time, adsorbent dosage, and temperature on the adsorption capacity were studied systematically. The experimental adsorption isotherm results were well represented by the Sips isotherm for PMAC 1/3 and the dual site Langmuir isotherm for PMAC 1/4. The maximum DBT adsorption by PMAC 1/3 and PMAC 1/4 were 99.7 and 95.7%, respectively. The kinetics for the adsorption of DBT on PMACs follows the pseudo second order behavior. The Weber-Morris plot shows the multilinearity over the entire time range, suggesting that both the surface and pore diffusions control the adsorption. The values of boundary layer thickness for PMAC 1/4 and PMAC 1/3 were found to be 3.183 and 1.643, respectively. Thus, PMAC 1/4 possesses more surface diffusion control than PMAC 1/3. The changes in Gibbs free energy (ΔG°), entropy (ΔS°), and enthalpy (ΔH°) are negative, which confirms that the studied process is spontaneous and exothermic and possesses less randomness at the interface. Based on the Sips isotherm, single-stage batch-adsorber design was prepared for the adsorption of DBT onto PMAC 1/3.

Adsorptive desulfurization of dibenzothiophene (DBT) in model petroleum distillate using functionalized carbon nanotubes

Industrial hydrodesulfurization method has not been efficient for removal of dibenzothiophene (DBT) from petroleum distillates. Therefore, in this current study, adsorptive desulfurization (investigated in batch mode) was carried out using functionalized carbon nanotubes (FCNTs) to reduce the amount of DBT in a model diesel. Different techniques, such as, scanning electron microscope (SEM) equipped with energy-dispersive X-ray (EDX), were used to check the morphological structure and the elemental compositions of the adsorbent; Fourier transmission infrared (FTIR) was used to check the chemical functionalities of the adsorbent; and nitrogen physisorption at 77 K was used to check the surface area, pore size, and pore volume of the adsorbent. The results show that the FCNTs outperformed the non-functionalized carbon nanotubes (CNTs) during the desulfurization by about 10%, indicating the functionalization did improve the desulfurization performance of the CNTs. The % removal of DBT by the FCNTs and CNTs was 70.48 and 60.88%, respectively. It can be concluded that the acid treatment of CNTs enhanced its surface affinity for DBT, thus contributing to the improved adsorption performance of the adsorbent. The isotherm results show that Freundlich isotherm model described well the mechanism of the adsorption process for both CNTs and FCNTs. In addition, pseudo second-order kinetics describes the behavior of the adsorbents during the adsorption process. The results obtained in this study therefore show that functionalized CNTs could be efficient and potential adsorbent for removal of DBT in petroleum distillate (e.g., diesel), to meet up with the stringent policies regarding emission of sulfur oxides.

Carbon Nanomaterials for the Adsorptive Desulfurization of Fuels

The increasing demand for cleaner fuels and the recent stringent regulations of commercial fuel specifications have driven the research of alternative methods to upgrade the current industrial desulfurization technology. Adsorptive desulfurization, the removal of refractory sulfur compounds using appropriate selective tailor-made adsorbents, has shown up as a promising alternative in the recent years. Carbon nanomaterials, namely, graphene, graphene oxide, carbon nanotubes and carbon nanofibers, show a significant potential as desulfurization adsorbents. Their surface area and porosity, their ability of easy functionalization, and their suitability to serve as a support of different types of adsorbents have rendered them attractive candidates for this purpose. In this review, after a presentation of the current industrial desulfurization practice and its limitations, the structure and properties of the carbon nanomaterials of interest will be described, followed by a detailed account of their applications in adsorptive desulfurization. The major literature findings and conclusions will be presented and discussed as a road map for future research in the field.