A model hydrochar was synthesized from glucose at 180 °C and its Cu(II) sorption capacity was studied experimentally and computationally as an example of molecular-level adsorbent design. The sorption capacity of the glucose hydrochar was less than detection limits (3 mg g−1) and increased significantly with simple alkali treatments with hydroxide and carbonate salts of K and Na. Sorption capacity depended on the salt used for alkali treatment, with hydroxides leading to greater improvement than carbonates and K+ more than Na+. Subsequent zeta potential and infrared spectroscopy analysis implicated the importance of electrostatic interactions in Cu(II) sorption to the hydrochar surface. Computational modeling using Density Functional Theory (DFT) rationalized the binding as electrostatic interactions with carboxylate groups; similarly, DFT calculations were consistent with the finding that K+ was more effective than Na+ at activating the hydrochar. Based on this finding, custom-synthes... [more]

In this study, corn cob was used as raw material and modified methods employing KOH and KMnO4 were used to prepare activated carbon with high adsorption capacity for mercury ions. Experiments on the effects of different influencing factors on the adsorption of mercury ions were undertaken. The results showed that when modified with KOH, the optimal adsorption time was 120 min, the optimum pH was 4; when modified with KMnO4, the optimal adsorption time was 60 min, the optimal pH was 3, and the optimal amount of adsorbent and the initial concentration were both 0.40 g/L and 100 mg/L under both modified conditions. The adsorption process conforms to the pseudo-second-order kinetic model and Langmuir model. Scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and Zeta potential characterization results showed that the adsorption process is mainly physical adsorption, surface c... [more]

The desorption of heavy oil is one of the important indicators affecting the development efficiency of the remaining oil in nanopores. However, the study of the adsorption and diffusion mechanisms of heavy oil molecules in nanopores remains scarce. In this work, the influences of temperature on the adsorption and diffusion properties of the heavy oil four-fractions in quartz nanopore have been investigated via molecular dynamics simulations. Our results show that the heavy oil molecules will form a denser multilayer adsorption oil layer on the nanopore surface, and high temperature can alter the adsorption behaviors of the heavy oil four-fractions. As the temperature increases, the saturate molecules are desorbed from the nanopore surfaces, but the aromatic, resin, and asphaltene molecules maintain a tendency to aggregate towards the nanopore surface. In particular, the agglomeration behaviors of most saturate, aromatic and asphaltene molecules in nanopore can be suppressed by the conf... [more]

Arsenic contamination of groundwater is still a global problem due to the toxicity at low dose on human health confirmed by epidemiological studies. Magnetic xerogel monoliths (MXs) were synthesized by the sol-gel polymerization using resorcinol, formaldehyde, alkaline catalyst and magnetite. The varying molar ratios of magnetite and resorcinol (M/R) in the gel were evaluated for As(V) removal from groundwater. The surface chemistry, structure and morphology of MXs related to arsenic adsorption were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and point of zero charge. Batch adsorption experiments were carried out to investigate the effects of Fe contents, initial pH and adsorbent dose on As(V) removal performance. The MXs with molar ratio of M/R at 0.15 gave the maximum As(V) adsorption capacity and removal with values of 62.8 µg/g and 86.7%, respectively. The adsorption data were well d... [more]

Carbon sequestration via the carbon capture and storage (CCS) method is one of the most useful methods of lowering CO2 emissions in the atmosphere. Ethylenediamine (EDA)- and triethylenetetramine (TETA)-modified mesoporous carbon (MC) has been successfully prepared as a CO2 storage material. The effect of various concentrations of EDA or TETA added to MC, as well as activated carbon (AC), on their CO2 adsorption capacity were investigated using high-purity CO2 as a feed and a titration method to quantitatively measure the amount of adsorbed CO2. The results showed that within 60 min adsorption time, MCEDA49 gave the highest CO2 capacity adsorption (19.68 mmol/g), followed by MC-TETA30 (11.241 mol/g). The improvement of CO2 adsorption capacity at low TETA loadings proved that the four amine functional groups in TETA gave an advantage to CO2 adsorption. TETA-functionalized MC has the potential to be used as a CO2 storage material at a low concentration. Therefore, it is relatively benign... [more]

Drift deposition of emerging and carcinogenic contaminant dicamba (3,6-dichloro-2-methoxy benzoic acid) has become a major health and environmental concern. Effective removal of dicamba in aqueous medium becomes imperative. This study investigates the adsorption of a promising adsorbent, MIL-101(Cr) metal-organic framework (MOF), for the removal of dicamba in aqueous solution. The adsorbent was hydrothermally synthesized and characterized using N2 adsorption-desorption isotherms, Brunauer, Emmett and Teller (BET), powdered X-ray diffraction (XRD), Fourier Transformed Infrared (FTIR) and field emission scanning electron microscopy (FESEM). Adsorption models such as kinetics, isotherms and thermodynamics were studied to understand details of the adsorption process. The significance and optimization of the data matrix, as well as the multivariate interaction of the adsorption parameters, were determined using response surface methodology (RSM). RSM and artificial neural network (ANN) were... [more]

This study focuses on using a facile method for the green preparation of activated carbon (AC) from palm tree fiber (PTF) waste. The synthesized cost-effective AC was investigated for the removal of an anionic dye (Congo red, CR) and a cationic dye (Rhodamine B, RhB) from wastewater. The morphological and structural characterization of the synthesized AC were performed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), surface area, Fourier transform infrared spectroscopy (FTIR), total pore volume, average pore diameter and pore size distribution, zeta potential, and zero-point charge. To investigate the adsorption efficiency, different parameters such as adsorbent dosage, solution pH, initial dye concentration, and duration were applied using the batch experiments. Various adsorption isotherm and kinetics models were applied to study the adsorption mechanism and dynamics. The results showed that chemical activation with a weak acid (H3PO4) at 400 °C for 30... [more]

A liquid-solid circulating fluidized bed (LSCFB) helps to overcome the shortcomings of conventional fluidized beds by using a particle separation and return system as an integral part of the overall reactor configuration. Batch adsorption experiments were carried out for the removal of phenol from a synthetically prepared solution using fresh activated-carbon-coated glass beads. The morphological features and surface chemistry of the adsorbent were analyzed via SEM and FTIR techniques. The adsorbent dosage, contact time and temperature were varied along with solution pH to assess their effects on the adsorbent performance for phenol removal. Isotherm modeling showed that the phenol removal using the activated-carbon glass beads followed the Langmuir model. Effectively, it was observed at an adsorbent loading of 2.5 g/150 mL of feed volume and a contact time of 3 h produced an 80% efficiency in the batch study. Furthermore, on scaling it up to the column, the desired 98% phenol-removal... [more]

The aim of this study was to investigate the adsorption of Cu(II) and Zn(II) onto apple tree branches biochar (BC) produced at 300, 400, 500 and 600 °C (BC300, BC400, BC500, and BC600), respectively. The effect of adsorbent dosage, pH value, contact time, initial concentration of Cu(II) or Zn(II), and temperature on the adsorption process were investigated. The result showed that 5 g BC·L−1 was the optimal dosage to remove Cu(II) and Zn(II) from wastewater and the maximum adsorption efficiency was achieved at a pH of 5.0 for all the BCs when the initial concentration of Cu(II) and Zn(II) were 64 and 65 mg L−1, respectively. Adsorption kinetics and isotherm experiments showed that the pseudo-second order equation and the Langmuir isotherm could best describe the adsorption process, indicating that the adsorption of Cu(II) and Zn(II) onto BCs were monolayer processes and chemisorption was the rate limiting step. The values of ΔG0 for the absorption of Cu(II) and Zn(II) on all BCs were ne... [more]

Over time, oil production in a reservoir tends to decrease, which makes it difficult to flow through the reservoir to the well, making its production increasingly difficult and costly. Due to their physical properties, such as reducing the water/oil interfacial tension, surfactants have been used in enhanced oil recovery (EOR) processes, however, their adsorption presents as an undesirable and inevitable factor and can decrease the efficiency of the method. This work’s main objective is to evaluate the effect of glycerol in the adsorption of surfactants in sandstones, as well as in the recovery factor during EOR. Brine solutions containing the nonionic surfactant saponified coconut oil (SCO), with and without glycerol, were used in the adsorption and oil recovery tests in sandstone. Adsorption, recovery, rheological, and thermogravimetric analysis were carried out. Regarding the surfactant/glycerol/brine solution, there was an improvement in the oil mobility, as the glycerol contribute... [more]

Adsorption chillers offer an environmentally friendly solution for the valorisation of waste or solar heat for cooling demands. A recent application is high efficiency data centre cooling, where heat from CPUs is used to drive the process, providing cooling for auxiliary loads. The metal organic framework aluminium fumarate with water is potentially a suitable material pair for this low temperature driven application. A targeted heat exchanger design is a prerequisite for competitiveness, requiring, amongst other things, a sound understanding of adsorption equilibria and adsorption enthalpy. A novel method is employed for their determination based on small isothermal and isochoric state changes, applied with an apparatus developed initially for volume swing frequency response measurement, to samples with a binder-based adsorbent coating. The adsorption enthalpy is calculated through the Clausius−Clapeyron equation from the obtained slopes of the isotherm and isobar, while the absolute... [more]

Glycerol conversion processes such as aqueous phase reforming and hydrogenolysis generate value-added compounds highly diluted in water. Because distillation is a high energy demand separation step, adsorption could be an attractive alternative to recover these chemicals. Adsorption isotherms of 1,2-propanediol, acetol, ethylene glycol and glycerol onto activated carbon were determined by batch adsorption experiments. These isotherms were fitted slightly better to the Freundlich equation than to the Langmuir equation. Acetol is the compound with the highest adsorption at concentrations smaller than 1 M. Properties of the adsorbate such as the −OH group number, chain length, molecular size and dipole moment, besides characteristics of the adsorbent such as the surface area, oxygen and ash content, are considered to explain the observed results. Moreover, adsorption experiments were performed with mixtures of compounds and it was determined that the molar amount adsorbed is less than pre... [more]

The high environmental impact of conventional methods of cooling and heating increased the need for renewable energy deployment for covering thermal loads. Toward that direction, the proposed system aims at offering an efficient solar powered alternative, coupling a zeolite−water adsorption chiller with a conventional vapor compression cycle. The system is designed to operate under intermittent heat supply of low-temperature solar thermal energy (<90 °C) provided by evacuated tube collectors. A prototype was developed and tested in cooling mode operation. The results from the testing of separate components showed that the adsorption chiller was operating efficiently, achieving a maximum coefficient of performance (COP) of 0.65. With respect to the combined performance of the system, evaluated on a typical week of summer in Athens, the maximum reported COP was approximately 0.575, mainly due to the lower driving temperatures with a range of 75 °C. The corresponding mean energy effici... [more]

In this research, the idea of multicomponent, one-vessel cleaning of syngas through simultaneous dedusting and adsorption is described. Data presented were obtained with the use of a pilot-scale 60 kWth fixed-bed GazEla reactor, coupled with a dry gas cleaning unit where mineral sorbents are injected into raw syngas at 500−650 °C, before dedusting at ceramic filters. The research primarily presents results of the application of four calcined sorbents, i.e., chalk (CaO), dolomite (MgO−CaO), halloysite (AlO−MgO−FeO), and kaolinite (AlO−MgO) for high-temperature (HT) adsorption of impurities contained in syngas from gasification of biomass. An emphasis on data regarding the stability of the filtration process is provided since the addition of coating and co-filtering materials is often necessary for keeping the filtration of syngas stable, in industrial applications.

Due to global climate change and fossil fuel depletion, the rational use of thermal energy has attracted great research interest. Large differences between indoor and outdoor temperatures in cold regions results in huge amounts of heat waste and drop in indoor humidity. Ventireg, an adsorption method, has been often recommended for heat and humidity regeneration in cold countries. In this research work, VentireC, an advanced method employing two thermally coupled adsorbent beds is discussed. It allows the heat released during adsorption of moisture in one adsorber to be transferred to another adsorber to facilitate water desorption. The VentireC approach is comprehensively analysed and described in this paper. A composite adsorbent based on LiCl in silica gel pores, which can exchange up to 0.5 g-H2O/g-sorbent, is selected for VentireC processes under cold Western Siberia conditions. Mathematical simulation of humidity recuperation, employing the selected sorbent with and without therm... [more]

Biogas upgrading is a key operation for transforming raw biogas into valuable biomethane that can be used as fuel or transported through pipelines. Pressure swing adsorption (PSA) is one possible technique that can be used for upgrading. ZSM-5 with high silica/aluminum (Si/Al) ratio has a reasonable CO2/CH4 selectivity and an almost linear CO2 adsorption isotherm, which can reduce power consumption. Extrusion of zeolites uses Al-based binders which can result in a denaturation and in a decrease of Si/Al ratio, promoting a steeper CO2 isotherm and also impacting the water adsorption. In this work, we have extruded a ZSM-5 (with a Si/Al = 200) using only silica-based binder. Different samples were obtained using different extrusion paste compositions and operating conditions and their textural properties characterized. The mechanical strength of the samples as well as the CO2, CH4, and H2O adsorption equilibrium isotherms at 303−343 K were measured. Our results show that it is possible t... [more]

The thermal masses of components influence the performance of many adsorption heat pump systems. However, typically when experimental adsorption systems are reported, data on thermal mass are missing or incomplete. This work provides original measurements of the thermal masses for experimental sorption heat exchanger hardware. Much of this hardware was previously reported in the literature, but without detailed thermal mass data. The data reported in this work are the first values reported in the literature to thoroughly account for all thermal masses, including heat transfer fluid. The impact of thermal mass on system performance is also discussed, with detailed calculation left for future work. The degree to which heat transfer fluid contributes to overall effective thermal mass is also discussed, with detailed calculation left for future work. This work provides a framework for future reporting of experimental thermal masses. The utilization of this framework will enrich the data av... [more]

The pulse decay test is the main method employed to determine permeability for tight rocks, and is widely used. The testing gas can be strongly adsorbed on the pore surface of unconventional reservoir cores, such as shale and coal rock. However, gas adsorption has not been well considered in analysis pulse decay tests. In this study, the conventional flow model of adsorbed gas in porous media was modified by considering the volume of the adsorbed phase. Then, pulse decay tests of equilibrium sorption, unsteady state and pseudo-steady-state non-equilibrium sorption models, were analyzed by simulations. For equilibrium sorption, it is found that the Cui-correction method is excessive when the adsorbed phase volume is considered. This method is good at very low pressure, and is worse than the non-correction method at high pressure. When the testing pressure and Langmuir volume are large and the vessel volumes are small, a non-negligible error exists when using the Cui-correction method. I... [more]

The thermal energy storage properties of a working fluid can be modified by the exothermic and endothermic adsorption and desorption of fluid molecules in the micro/nanoporous materials. In this study, thermogravimetric (TG) analysis experiments and molecular simulations (molecular dynamics, MD, and grand canonical Monte Carlo, GCMC) were employed to examine the thermal energy storage properties of the UIO-66 metal organic framework material, UIO-66/H2O nanofluids and pure water. Our results showed that the molecular simulation calculations were, in principle, consistent with the obtained experimental data. The thermal energy storage performance of UIO-66/H2O nanofluids was enhanced with the increase in the UIO-66 mass fraction. In addition, the differences between the simulation calculations and experimental results could be mainly ascribed to the different structures of UIO-66 and the evaporation of fluid samples. Furthermore, this work indicated that molecular simulations contribute... [more]

Natural gas sweetening is an essential process within hydrocarbon processing operations, enabling compliance with product quality specifications, avoiding corrosion problems, and enabling environmental care. This process aims to remove hydrogen sulfide (H2S), carbon dioxide, or both contaminants. It can be carried out in fixed-bed adsorption towers, where iron oxide-based solid sorbent reacts with the H2S to produce iron sulfides. This study is set out to develop a fluid-dynamic model that allows calculating the pressure drop in the H2S adsorption towers with the novelty to integrate reactivity aspects, through an iron sulfide layer formation on the solid particles’ external skin. As a result of the layer formation, changes in the particle diameter and the bed void fraction of the solid sorbent tend to increase the pressure drop. The shrinking-core model and the H2S adsorption front variation in time support the model development. Experimental data on pressure drop at the laboratory sc... [more]

In a resorption heat pump, the adsorption and desorption reaction of ammonium chloride (NH4Cl) with ammonia (NH3) is of interest as a Low Temperature Salt (LTS). Reviewing previously published NH4Cl-NH3 equilibrium lines, ammonium chloride appears to offer useable working temperatures (50−70 °C) in the 10−15 bar pressure range during the adsorption reaction, and provides beneficial working conditions for the desorption reaction, when compared with alternative LTS candidates at atmospheric pressure. The NH4Cl-NH3 adsorption and desorption reactions, using a NH4Cl composite salt, have been evaluated under dynamic ‘real-world’ conditions in a Large Temperature Jump (LTJ) experimental testing rig; although there are concerns with mass transfer characteristics, the salt exhibits no hysteresis between the adsorption and desorption reactions, contrary to previous literature. The experimentally obtained equilibrium line values for the reaction enthalpy and entropy are 29,835 J/mol and 207 J/(m... [more]

The growing interest in using low-cost methods that use natural sources makes the study of adsorption processes increasingly frequent and common. Thus, the use of uçá crab shell (Ucides cordatus) in the adsorption of reactive dye (reactive blue 222) was studied in two systems (S1 and S2) in a finite bath, with a scale-up of 12 times and considering different forms of agitation. The biosorbent material was previously characterized from FTIR and EDX spectroscopies, SEM, physical adsorption of N2, and point of zero charge. The kinetic study allowed modeling the experimental data and defining the equilibrium time for the S1 system as 400 min, and the S2 system as 360 min. The equilibrium adsorption capacities are 3.623 mg·g−1 (S1) and 4.191 mg·g−1 (S2). The pseudo-second-order (PSO) model best described the experimental data. The favorable multilayer adsorption was confirmed for the isothermal analysis, and the Freundlich and Sips models represented the experimental data of S1 and S2, resp... [more]

Adsorption-based processes using metal-organic frameworks (MOFs) are a promising option for carbon dioxide (CO2) capture from flue gases and biogas upgrading to biomethane. Here, the adsorption of CO2, methane (CH4), and nitrogen (N2) on Zn(dcpa) MOF (dcpa (2,6-dichlorophenylacetate)) is reported. The characterization of the MOF by powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), and N2 physisorption at 77 K shows that it is stable up to 650 K, and confirms previous observations suggesting framework flexibility upon exposure to guest molecules. The adsorption equilibrium isotherms of the pure components (CO2, CH4, and N2), measured at 273−323 K, and up to 35 bar, are Langmuirian, except for that of CO2 at 273 K, which exhibits a stepwise shape with hysteresis. The latter is accurately interpreted in terms of the osmotic thermodynamic theory, with further refinement by assuming that the free energy difference between the two metastable structures of Zn(dcpa) is a norma... [more]

The results of the advanced computer analysis of the influence of time and gas atmosphere of the chemical activation process on the microporous structure formation of activated carbons prepared from oil palm shell via microwave irradiation and activation, using potassium hydroxide as an activation agent, are presented in this paper. The quenched solid density functional theory (QSDFT) and the new numerical clustering-based adsorption analysis (LBET) methods were used especially in the analysis of the microporous structure of the activated carbons, taking into account the surface heterogeneity, and the results obtained were confronted with the simple results achieved earlier using Brunauer−Emmett−Teller (BET) and T-plot methods. On the basis of the computer analysis carried out and taking into account the results obtained, it has been shown that the material with the best adsorption properties and suitable for practical industrial applications is activated carbon obtained in a gaseous n... [more]

Based on density functional theory calculation, we screened suitable Ti-decorated carbon-based hydrogen adsorbent structures. The adsorption characteristics and adsorption mechanism of hydrogen molecules on the adsorbent were also discussed. The results indicated that Ti-decorated double vacancy (2 × 2) graphene cells seem to be an efficient material for hydrogen storage. Ti atoms are stably embedded on the double vacancy sites above and below the graphene plane, with binding energy higher than the cohesive energy of Ti. For both sides of Ti-decorated double vacancy graphene, up to six H2 molecules can be adsorbed around each Ti atom when the adsorption energy per molecule is −0.25 eV/H2, and the gravimetric hydrogen storage capacity is 6.67 wt.%. Partial density of states (PDOS) analysis showed that orbital hybridization occurs between the d orbital of the adsorbed Ti atom and p orbital of C atom in the graphene layer, while the bonding process is not obvious during hydrogen adsorptio... [more]