The challenges of hydrodesulfurization for desulfurizing the refractory sulfur compounds of petroleum fuels are prompting researchers to investigate the different non-conventional desulfurization ...techniques. Adsorptive desulfurization (ADS) is emerging as a low-cost alternative to ultra-deep hydrodesulfurization. In ADS, sulfur compounds are removed via physicochemical adsorption using a selective adsorbent. This review focuses on the latest development in ADS. Zeolite, metal oxide, metal-organic framework, mesoporous material, and carbon are assessed for desulfurization of the model and real feedstocks. The ADS performance of these materials can be improved by incorporating metals. Recent progress on improving the selectivity, stability, reusability is discussed. Depending on adsorbent surface chemical composition, sulfur molecules are removed through π complexation, acid-base, metal‑sulfur, and Van der Waals forces. The effects of process parameters, thermodynamics, and kinetics of ADS are also discussed. Selectivity is found to be a key challenge in ADS of real feedstocks due to competitive adsorption. The testing of adsorbents with real fuels is crucial for the commercialization of ADS. Developments of robust adsorbent with less expensive metals and ideal regeneration methods are needed to demonstrate the capabilities of ADS commercially. The search for a low-cost, and efficient ADS adsorbent is ongoing, and currently, its industrial adaptation is extremely limited.
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•A brief review of various desulfurization technologies.•Review of adsorptive desulfurization (ADS) and its mechanisms, thermodynamics and kinetics.•Zeolite, metal oxide, metal-organic framework, mesoporous material, carbon, and clay are assessed for ADS.•Zeolite, metal oxide, metal-organic framework, mesoporous material, carbon, and clay are assessed for ADS.•The current status of ADS for desulfurization of real feedstocks is emphasized.•Further research to overcome the present obstacles of ADS of petroleum feedstocks is proposed.
In this study, carbon nanotube-based adsorbents, oxidized multi-walled carbon nanotube (OMWCNT) with non-magnetic property and OMWCNT-Fe3O4 and OMWCNT-κ-carrageenan-Fe3O4 nanocomposites with magnetic ...property, having different structural and surface properties were prepared and their adsorptive properties for the removal of toxic diquat dibromide (DQ) herbicide from water by adsorption were determined in detail. For each adsorption system, the effects of initial DQ concentration, contact time and temperature on the adsorption processes were determined. Equilibrium time was found to be 300 min for DQ solutions. OMWCNT showed faster adsorption and higher maximum adsorption capacity value than magnetic adsorbents. With increasing initial herbicide concentration from 5.43 mg.L−1 to 16.3 mg.L−1, the values of initial sorption rate exhibited a decrease from 29.1 mg.g−1.min−1 to 4.28 mg.g−1.min−1 for OMWCNT-DQ system, from 1.21 mg.g−1.min−1 to 0.823 mg.g−1.min−1 for OMWCNT-Fe3O4-DQ system and from 0.674 mg.g−1.min−1 to 0.612 mg.g−1.min−1 OMWCNT-κ-carrageenan-Fe3O4 system. Maximum adsorption capacity value of OMWCNT was approximately 2.8-fold higher than magnetic OMWCNT-Fe3O4 and 5.4-fold higher than magnetic OMWCNT-κ-carrageenan-Fe3O4 at 25 °C. Adsorption kinetic and isotherm data obtained for all adsorption systems were well-fitted by pseudo second-order and Langmuir models, respectively. Thermodynamic parameters indicated that the adsorption of DQ onto carbon nanotube-based adsorbents was spontaneous and endothermic process. Furthermore, OMWCNT having the highest herbicide adsorption capacity could be regenerated and reused at least five times. This study showed that carbon nanotube-based adsorbents with magnetic and non-magnetic property were of high adsorption performance for the removal of DQ from water and could be promising adsorbent materials for the efficient removal of herbicides from wastewaters.
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•CNT-based adsorbents with magnetic or non-magnetic property were used to remove DQ from water.•OMWCNT showed much higher adsorption capacity and rate than magnetic nanocomposite adsorbents.•π-e- density, SBET and Vpore of CNT-based adsorbents are mainly effective for DQ adsorption.•Herbicide loaded OMWCNT could be well regenerated.•Adsorption kinetics, isotherms and thermodynamics were investigated in detail.
Present work was mainly focused on to adopt a mixed metal oxide adsorbent for efficient fluoride treatment in drinking water with parametric optimization of the adsorption process. Mixed Al/Fe/Ca ...metallic oxide adsorbent was synthesized using co-precipitation technique of Al (III), Fe (III) and Ca(OH)2 salt solutions at molar proportion of 1:1:1. Fluoride adsorption process was optimized using Box-Bhekhen methodology by planning design of experiments with respect to various process parameters, such as, initial fluoride concentration, adsorbent dose, pH and contact time. Maximum fluoride removal of 91.1% was observed at an optimum operating condition of 7 mg L−1 initial fluoride concentration, 3 g L−1 adsorbent dosage, pH of 7 and 3 h of contact time. Freundlich isotherm model described the present adsorption experimental data with best fitting, which demonstrate the mechanism of multilayer adsorption with a pseudo second order reaction kinetics. Continuous column adsorption study was dissected utilizing Thomas model, Adams-Bohart model and Yoon Nelson model. Column breakthrough performance was best described by Thomas model. Likewise, an attempt was made to examine the synthesized adsorbent reusability. It was discovered to be minute loss in adsorption capability after 5 recycle; 92.1% fluoride removal for fresh adsorbent and 90.6% removal after 5 time use. The treated water was analysed for remaining aluminium at optimum condition and noted to have < 0.2 mg L−1 which is within the desirable limits set by WHO standards. Finally, the synthesized adsorbent was tested for ground water samples of Nagaur district of Rajasthan, India containing high fluoride content.
Adsorption is one of the most widely used and effective wastewater treatment methods. The role of ionic strength (IS) in shaping the adsorption performances is much necessary due to the ubiquity of ...electrolyte ions in water body and industrial effluents. The influences of IS on adsorption are rather complex, because electrolyte ions affect both adsorption kinetics and thermodynamics by changing the basic characteristics of adsorbents and adsorbates. For a given adsorption system, multiple or even contradictory effects of IS may coexist under identical experimental conditions, rendering the dominant mechanism recognition and net effect prediction complicated. We herein reviewed the key advancement on the interaction and mechanisms of IS, including change in number of active sites for adsorbents, ion pair for metal ions, molecular aggregation and salting-out effect for organic compounds, site competition for both inorganic and organic adsorbates, and charge compensation for adsorbent-adsorbate reciprocal interactions. The corresponding fundamental theory was thoroughly described, and the efforts made by various researchers were explicated. The structural optimization of adsorbents affected by IS was detailed, also highlighting polyamine materials with exciting “salt-promotion” effects on heavy metal removal from high salinity wastewater. In addition, the research trends and prospects were briefly discussed.
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•Six key aspects on the interaction and mechanisms of ionic strength were reviewed.•The structural optimization of adsorbents affected by ionic strength was detailed.•Polyamine materials with exciting “salt-promotion” effects were highlighted.
Booming progress in the materials science offers a huge choice of novel porous solids which may be used for adsorption transformation of low temperature heat. This communication gives an overview of ...original and literature data on several classes of materials potentially promising for this important application, namely, metalaluminophosphates (AlPOs, SAPOs, MeAPOs), metal-organic frameworks (MIL, ISE, etc.), ordered porous solids (MCM, SBA, etc.), porous carbons and various composites (SWSs, AlPO-Al foil). For the SWS composites, we briefly considered the recent trends in their developing, namely, usage of host matrices with uniform pore dimensions and binary salt systems. We hope that this review will give new impulses to target-oriented research on the novel adsorbents for AHT and may also be beneficial for further consolidating international activities in materials science and heat transformation applications.
► New efficient adsorbents are pivotal for the adsorption heat transformation. ► We critically overview several classes of materials potentially promising for heat transformation. ► The main new classes are metalaluminophosphates, metal-organic frameworks and composites. ► Current tendencies in developing composite adsorbents are briefly considered.
In this study, a magnetic chitosan/Al2O3/Fe3O4 (M-Cs) nanocomposite was developed by ethylenediaminetetraacetic acid (EDTA) functionalization to enhance its adsorption behavior for the removal of ...Cd(II), Cu(II) and Zn(II) metal ions from aqueous solution. The results revealed that the EDTA functionalization of M-Cs increased its adsorption capacity ~9.1, ~5.6 and ~14.3 times toward Cu, Cd and Zn ions. The maximum adsorption capacity followed the order of Cd(II) > Cu(II) > Zn(II) and the maximum adsorption efficiency was achieved at pH of 5.3 with the removal percentage of 99.98, 93.69 and 83.81 %, respectively, for the removal of Cu, Cd and Zn ions. The metal ions adsorption kinetic obeyed pseudo-second-order equation and the Langmuir isothermal was found the most fitted model for their adsorption isothermal experimental data. In addition, the thermodynamic study illustrated that the adsorption process was exothermic and spontaneous in nature.
•Synthesis of chitosan/Al2O3/Fe3O4 nanocomposite as new adsorbent.•Removal of Cd(II), Cu(II) and Zn(II) metal ions from aqueous solution.•Removal of metal ions with recovery range more than 99 % using new adsorbent.
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•Reusable composite oil sorbents produced by synthesizing Reduced Graphene Oxide (rGO) and its infusion in polystyrene.•Polystyrene composite, (PS)/rGO, produced via solution blending ...and electrospinning method.•Surface area of PS was enhanced from 71.52 m2/g to 285.07 m2/g by incorporating rGO.•Oil adsorption capacity of PS-rGO was evaluated using engine oil, motor oil and vegetable oil.•PS-rGO showed adsorption capacity of 164.70 g/g, 129.68 g/g and 109.87 g/g, respectively.
This study enhanced the adsorptive capacity of polystyrene (PS) by infusing reduced graphene oxide (rGO) nanoparticles obtained from the synthesis of graphene oxide to produce PS-rGO composites via electrospinning method. Physicochemical characterization of as-synthesized rGO and PS-rGO were carried out through scanning electron microscopy, N2 physisorption among others. Oil sorption performance of synthesized rGO in crude oil, vegetable oil, fresh engine oil and used engine oil are 130.96 g/g, 121.77 g/g, 105.01 g/g and 100.56 g/g. Oil sorption capacities of electrospun pure PS in crude oil, vegetable oil, fresh engine oil and used engine oil were 46.32 g/g, 38.54 g/g, 35.14 g/g and 32.57 g/g and those of PS-rGO infused with 4 wt% of rGO were found to be 105.52 g/g, 98.86 g/g, 86.25 g/g and 83.47 g/g for crude oil, vegetable oil, fresh engine oil and used engine oil samples respectively. Pseudo second order (PSO) kinetic model fits the sorption data of the four oil samples on the four composite sorbents produced. Intra-particle diffusion (IPD) model evidently showed that sorption of the four oil samples on the four composite sorbents, occurred in three (3) phases. Composites demonstrate high oil adsorption capacity, and are reusable upto three sorption–desorption cycles.
Water pollution by organic dyes poses great challenge to the environment and living organism. Hence effective removal of organic dyes by cost effective methods have received significant attention in ...recent years. Herein, we report the complete removal of organic dyes (rhodamine B), methylene blue) and eosin yellow) from water via effective adsorption by MoO3 catalyst. Hydrothermally synthesised MoO2 (1) and amorphous MoSx (2) using ammonium molybdate without and with thiourea exhibited low dye adsorption. In contrast, crystalline micro/nanoplates of MoO3 (3 and 4) obtained from calcination of 1 and 2 showed highly enhanced dye adsorption. Particularly 4 showed higher dye adsorption compared to 3. UV–Visible absorption studies confirmed complete removal of organic dyes upon stirring with MoO3 catalyst. Dye removal studies further revealed that cationic dyes are adsorbed faster than anionic dye that could be attributed to the surface charge of MoO3. Interestingly, the adsorbed dyes were not released from MoO3 for more than 50 days. The exhausted MoO3 catalyst can be recovered by annealing at 400 °C. MoO3 catalyst has also been used as packing materials in dropper column and demonstrated effective removal of dyes by passing through dyes separately as well as mixture.
MoO3 nanoplates/rods prepared by hydrothermal-calcination method exhibited superior dye adsorption while stirring as well as filtration. Display omitted
•Fabricating nano/micro plates of MoO3 via hydrothermal-calcination method.•Highly enhanced dye adsorption by MoO3 nano/micro plates fabricated from MoSx.•Easy removal of mixed dyes by filtration using dropper column.•Regenerating used MoO3 adsorbent by calcination.
The effective adsorption and treatment of toxic gases have attracted great attention amongst researchers, particularly the use of new two-dimensional materials for achieving the adsorption of toxic ...gases. We applied the density functional theory to investigate the stability, geometric structural, electrical, and magnetic properties of NH3 molecules adsorbed on pristine, F-vacancy defected, and transition-metals (V, Cr, Mn, Y, Nb, and Mo) doped Zr2CF2. The charge transfer and adsorption energy of the original substrate were low, indicating that the interaction between NH3 and Zr2CF2 was primarily physical adsorption. After introducing F-vacancy and TM-doping, the adsorption stability was enhanced, with the large charge transfer and high adsorption energies indicating that the adsorption of NH3 transitioned to chemisorption. Electronic density of state diagrams suggested that the enhanced interaction was mainly caused by the hybridization of the d orbitals of dopants and p orbitals of the adsorbed NH3 molecules. The adsorption energy of NH3 molecules on Y-doped Zr2CF2 was the highest at a value of −1.425eV, and the material was also explored as an adsorbent for NH3 gas. After adsorbing six NH3 molecules, the Y-doped substrate had an average adsorption energy of −1.350eV and still maintained a good thermal stability at a temperature of 300 K. These results can provide insights into the development of sensors and adsorbents based on MXenes.
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•The adsorption of NH3 on perfect Zr2CF2 was physical adsorption.•The introduction of F-vacancy enhanced the adsorption stability of NH3 molecule.•The doping of transition-metal (V, Cr, Mn, Y, Nb, Mo) significantly improved the sensitivity of Zr2CF2 to NH3 gas.•Y-doped Zr2CF2 can be used as effective adsorbent to NH3 gas.
