Adsorption Equilibrium Parameters Research Articles

Cluster adsorption of L-histidine on carbon nanotubes at different temperatures

The adsorption isotherms of L-histidine on MKN-SWCNT-S1 CNTs from aqueous solution at temperatures of 25, 35, 45, 55, 65 and 80 °C were interpreted within the framework of the single-layer cluster adsorption model. A new approach to determine the equilibrium parameters of the cluster adsorption isotherm equation and sorbate structure on CNTs, as well as a nonlinear modelling method, was applied. To confirm the cluster nature of amino acid adsorption on CNTs, the clustering criterion proposed in the previous work was applied, and the cluster structure was evaluated, which is significant for the application of CNTs in biomedicine. The found equilibrium parameters of adsorption were applied to the determination of thermodynamic characteristics of adsorption (changes in Gibbs energy, enthalpy and entropy) of L-histidine on CNTs and the character of adsorption was analysed.

Preparation, Characterization, and Adsorption Performance of H2TiO3 Lithium Ion Sieves with Homogeneous Nanoparticles: Kinetics, Thermodynamics, and Mechanism Analysis

AbstractLi2TiO3 precursor with layered structure is successfully prepared by template‐free method using anatase TiO2 and Li2CO3, followed by the treatment of dilute hydrochloric acid, which leads to obtaining H2TiO3 lithium ion sieve nanoparticles with uniform dispersion and small size. The adsorption performance and mechanism of the H2TiO3 are being studied. The experimental results show that the H2TiO3 lithium ion sieve has a large BET specific surface area (19.10 m2 g−1) and good thermal stability. At the same time, it also has a high adsorption rate and adsorption capacity (55.13 mg g−1) towards Li+ in solution due to its high dispersibility and uniformity of particle size, which can expose more adsorption sites in LiCl solution. The adsorption capacity of the H2TiO3 lithium ion sieve can reach 46.63 mg g−1, which achieves 84.58% of the equilibrium adsorption capacity. The equilibrium adsorption parameters follow the Langmuir model perfectly, demonstrating that Li+ undergoes monolayer adsorption. The results of thermodynamic and kinetic analysis show that the adsorption behavior of H2TiO3 is spontaneous and conforms to the pseudo‐second‐order kinetic model, indicating the adsorption process is controlled by chemosorption. In addition, after five adsorption/desorption cycles, the H2TiO3 lithium ion sieve still shows a high adsorption capacity of 46.15 mg g−1, and the dissolution loss of titanium is only 0.14%, which shows that the cycle stability is excellent. XPS and zeta potential analyses illustrate that the adsorption mechanism of Li+ on the H2TiO3 is an ion exchange reaction between Li+ and H+, combined with the electrostatic attraction of the adsorbent surface. Additionally, the adsorption performance of H2TiO3 lithium ion sieve in West Taijinaier Salt Lake brine was tested, and the adsorbent material proves itself is a perspective candidate for lithium extraction from aqueous lithium resources.

Application of zirconium aspartic acid metal-organic framework (MIP-202(Zr)) for high efficient ruthenium adsorption from aqueous solutions

The zirconium metal – organic framework MIP-202(Zr), based on L-aspartic acid, was prepared by hydrothermal method and used for study of ruthenium adsorption from aqueous solutions. The obtained material was characterized by X-ray diffraction (XRD), infra red spectroscopy (IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The batch adsorption experiment was performed for determination of adsorption equilibrium, kinetics and thermodynamics parameters to Ru(III) from aqueous solution on MIP-202(Zr). The data of ruthenium sorption onto MIP-202(Zr) were fitted and analyzed by the Langmuir, Freundlich and Temkin equilibrium isotherm models, while the Langumir adsorption isotherm models fit the best. Kinetic data were analyzed by four kinetic models, and ruthenium sorption on MIP202(Zr) can be describes the best by intra particle diffusion (Weber Morris). Analysis of thermodynamic properties of ruthenium ions sorption onto MIP-202(Zr) shows that the sorption process has a spontaneous and endothermic nature and is energetically beneficial.

Pressure dependence of adsorption isotherm parameters and transport dynamics of a nonionic surfactant, LS-36, at the carbon dioxide (CO[formula omitted]) gas–liquid water interface

Surfactants are important to a wide variety of elevated pressure processes; however, little is understood about the effect of pressure on surfactant interfacial thermodynamics or transport. While some experimental studies exist, concrete conclusions are difficult to infer due to experimental artifacts, e.g., non-equilibrium conditions. We recently showed that few experiments are capable of achieving bulk fluid saturation, which is essential to careful measurements of surfactant thermodynamics and transport dynamics. In other words, the accurate study of surfactant adsorption equilibrium and transport parameters first and foremost requires bulk fluids that are otherwise in equilibrium. This work uses our recently developed high pressure microtensiometer (HPMT), which ensures bulk phase saturation, to measure thermodynamic isotherms for tri(ethylene glycol)-hexa(propylene glycol)-monododecyl ether (LS-36) surfactant (concentrations between 10−7 and 10−3mol/L and pressures between 1 and 57bar) at the CO2 gas–liquid water surface. All measurements were conducted at 22.5 °C. Note that in this study, the surfactant was dissolved in the liquid water phase and is unable to partition into the gaseous CO2 phase. Isotherms at different pressures were determined from surface tension data, analyzed, and compared to determine trends in thermodynamic parameters. Dynamic surface tension measurements were performed to assess transport dynamics in terms of the well-studied diffusion timescale. We find that surface tension depends non-linearly on pressure and surfactant concentration, such that surfactants are less effective at lowering surface tension as pressure increases. Furthermore, surfactant adsorption is a non-monotonic function of pressure and goes through a maximum at intermediate pressures. This result suggests that surfactant adsorption is strongly dependent on the free energy of the CO2-water surface. Overall, this work shows that the thermodynamics of surfactants at equilibrium surfaces under pressure are non-trivial and need additional investigation to quantify the driving forces for surfactant adsorption and to develop models for high pressure processes.

Simulation Study of the Air Separation Performance of Cr-MIL-101 in High-Altitude Environments

The most severe challenge for troops in a high-altitude environment is hypoxia. Pressure swing adsorption coupled with membrane separation is an ideal solution for oxygen production in high-altitude areas, but the molecular sieve membranes and organic membranes used in this technique are greatly affected by the ambient temperature, humidity, and pressure. Compared with traditional porous materials, metal-organic frameworks (MOFs) have outstanding features such as low densities, large specific surface areas, high crystallinities, and flexible structures. Cr-MIL-101 (MIL: Matérial Institut Lavoisier) and its derivatives are MOFs with high nitrogen adsorption capacities and can be used for oxygen production by air separation. However, since the plateau climate is complex, the applicability of Cr-MIL-101 for oxygen production in high-altitude environments awaits clarification. Therefore, this study constructed a molecular model of Cr-MIL-101, simulated the adsorption equilibrium of N2 and O2 molecules on this material using the grand canonical Monte Carlo (GCMC) method, and obtained their adsorption isotherms and densities. At 298 K and 100 kPa, the maximum adsorption capacities of Cr-MIL-101 for N2 and O2 were 0.94 per cell and 0.23 per cell, respectively. While at 238 K and 100 kPa, the maximum adsorption amounts of Cr-MIL-101 for N2 and O2 were 5.10 and 1.07 per cell, respectively. The thermodynamic parameters and adsorption equilibrium parameters during the adsorption process were analyzed. The conclusion of this study provides theoretical support for optimizing the N2/O2 separation performance of Cr-MIL-101 in high-altitude environments.

Surfactant supported chitosan for efficient removal of Cr(VI) and anionic food stuff dyes from aquatic solutions

In order to develop a novel and cost-effective adsorbent with outstanding adsorption capacity and excellent recyclability for anionic pollutants, the chitosan-modified cetyltrimethylammonium bromide sorbent (CS@CTAB) was fabricated. Fourier-transform infrared spectroscopy, N2 adsorption–desorption isotherm, elemental analysis, Thermogravimetric analysis, X-ray diffraction, and Scanning electron microscopy have been applied to evaluate both raw and surfactant modified chitosan (CS@CTAB). Azorubine, Sunset Yellow, and hexavalent chromium were used to study the adsorption behavior of CS@CTAB under various parameters such as adsorbent dose, initial dye and metal ion concentration, contact time, and temperature. Adsorption equilibrium, kinetics models and thermodynamic parameters were investigated. The adsorption isotherm fitted well with the Langmuir isotherm model, with a maximum adsorption capacity of 492.6 mg/g, 492.6 mg/g, and 490.196 mg/g for Azorubine, Sunset Yellow, and Hexavalent Chromium, respectively. The kinetic studies showed that the pseudo-second-order model provided a better correlation between experimental data. Furthermore, the calculated thermodynamic parameters confirmed that the adsorption of Cr(VI), E110, and E122 by CS@CTAB material is a spontaneous and exothermic process. The fabricated CS@CTAB adsorbent was employed for the efficient elimination of Azorubine, Sunset Yellow, and hexavalent chromium from real water samples, synthetic mixtures, and colored soft drinks, with a percentage of recovery of ~ 96%. The plausible adsorption mechanisms of Azorubine, Sunset Yellow, and hexavalent chromium on the surface of CS@CTAB are elucidated. The adsorption anticipated to be due to electrostatic interaction and hydrogen bond formation for hexavalent chromium; while the adsorption of Azorubine and Sunset Yellow, was assumed to be due to electrostatic interaction, hydrogen bonding, and n-π interaction. Finally, the study demonstrates the efficiency of CS@CTAB for the removal of anionic species from several samples, including natural water and colored beverages.

Removal of Toxic Basic Fuchsin Dye from Liquids by Antibiotic Azithromycin Using Adsorption, TD-DFT Calculations, Kinetic, and Equilibrium Studies

This work aims to study the removal of new fuchsin dye (NFD) using azithromycin (Az) by a spectrophotometric technique at two different wavelengths (547 and 286 nm), which formed the blend [Az+NFD]. Afterward, the [Az]TF, [NFD]TF, and nanoblend [Az+NFD]NB thin films were fabricated using the spin-coating technique. The models of Langmuir and Freundlich isotherms were applied to examine the experimental data of adsorption equilibrium and activation parameters. At 547 and 286 nm, the sorption capacity (qm) was determined to be 0.0095 and 0.01 mg g–1, correspondingly. The kinetic data showed that the reaction was fitted with a first-order reaction and the maximum adsorption capacity of Az at 547 nm was 0.0198 mg g–1 at 313 and 323 K, whereas at 286 nm, it was 0.0071 mg g–1 at 303 K. The thermodynamic parameters (ΔH°, ΔS°, and ΔG°) were calculated, and the experimental results showing negative values of ΔH° at 547 and 286 nm (−33.67 and −11.22 kJ mol–1, respectively) indicate the adsorption of NFD using Az is an exothermic reaction. The negative values of ΔG° at 547 and 286 nm (−19.67 and −13.01 kJ mol–1, respectively) indicate a spontaneous reaction. The calculated time-dependent density functional theory (TD-DFT) spectra matched the measured IR spectra precisely and corroborated the molecular structure of the tested materials. The experimental values and TD-DFT/CASTEP predictions for these properties are in great agreement. The optical (TD-DFT/CASTEP) characteristics of the [Az]Iso, [NFD]Iso, and [Az+NFD]NB gaseous phases are in close agreement with the experimental results. The greatest absorption bands for [Az]TF, [NFD]TF, and [Az+NFD]NB correspond to the π → π* electronic transition at 268, 547, and 625 nm, respectively, and the Gaussian program corresponds well with the experimental analysis for synthetic IR and molecular electrostatic potential. Optical illumination studies suggest that the nanoblend device films investigated may be employed in solar cell applications. The quantity of dye removed by Az decreases with an increase in the contact time and optimum adsorption was achieved in 4 min at 547 nm, whereas it increases with time at 286 nm and an optimum adsorption capacity was achieved in 6 min. The isolated molecule of [Az+NFD]Iso has a band gap of 2.415 eV, as determined by TD-DFT/DMol3. Thin films of thickness 100 ± 3 nm of [Az]TF, [NFD]TF, and [Az+NFD]NB via a spin-coating technique at room temperature were fabricated.

CO2 methanation enhanced with a cyclic SERP process using a commercial Ni-based catalyst mixed with 3A zeolite as adsorbent

Valorization of greenhouse gas CO2 is needed to mitigate and reduce climate change impact. The sustainable production of methane to obtain synthetic natural gas (SNG) is one of the most attractive solutions, given current needs. The methanation reaction, known as the Sabatier reaction, is limited by the formation of CO as an intermediate at high temperatures and the formation of H2O as a by-product. For this reason, recent research has focused on the use of catalysts/adsorbents mixtures capable of retaining the water produced as well as being methane-selective at low temperatures. In this work, the kinetic model of a commercial Ni/SiAl catalyst in an experimental reaction bed was obtained. Moreover, the water adsorption capacity of the catalyst has been studied in the typical reaction temperature range (473–623 K), and the adsorption equilibrium and diffusional parameters were determined. With the data obtained from these experiments, the methane production in a cyclic Sorption Enhanced Reaction Process (SERP) has been simulated, adding zeolite 3A as a water selective adsorbent. The process consists of three consecutive stages: an adsorption/reaction stage and two other stages, rinse and purge, to desorb the adsorbed water and remove it by condensation. A sensitivity analysis has been carried out to determine the effect of the operational variables on the process performance to obtain methane suitable for domestic natural gas consumption. A CO2 conversion of 99.7 %, methane selectivity of 99.9 %, molar purity of CH4 of 98.2 % as product, and compression energy consumption (6.97 kJ/mol CH4) 99 times lower than methane combustion energy has been obtained, proposing, therefore, a new process of methanation.

Calculation of the Henry’s Constant and the Thickness of the Equilibrium Adsorption Layer of Radon in the Layer-by-Layer Measurement of the Sorbent Activity

The radioactive gas radon is ubiquitous in the environment and is a major contributor to the human inhalation dose. It is the second leading cause of lung cancer after smoking. Radon concentrations are particularly high in the air of radon-hazardous facilities—uranium mines and radioactive waste repositories containing radium. To reduce the dose load on the staff, air in these premises should be continuously or periodically purified of radon. Carbon adsorbers can be successfully used for this purpose. The design of sorption systems requires information on both equilibrium and kinetic parameters of radon dynamic adsorption. The traditional way of obtaining such characteristics of the sorbent is to analyze the breakthrough curves. The present paper proposes a simple alternative method for determining parameters of dynamic radon adsorption (Henry’s constant and equilibrium adsorption layer thickness) from the results of a layer-by-layer gamma-spectrometric measurement of the sorbent. The analytical equation for smooth distribution of radon activity in the sorbent layer is obtained based on equilibrium adsorption layer theory for elute chromatography (pulsed injection of radon into the column). Using the dynamic adsorption of 222Rn on AG-3 activated carbon as an example, both equilibrium (Henry’s constant) and kinetic (thickness of the equilibrium adsorption layer) parameters of the adsorption dynamics were calculated. It was shown that the exposure duration of the column bed in the air flow and superficial gas velocity do not affect the result of the Henry’s constant calculation. The dependence of the equilibrium adsorption layer thickness on the superficial gas velocity over a wide range of values (5–220 cm/min) is described by the van Deemter equation. It was shown that the optimum air flow velocity, which corresponds to the maximum effectiveness of the bed, is 15–30 cm/min. This corresponds to the minimum of the equilibrium adsorption layer thickness (about 0.6 cm). The developed mathematical model makes it easy to define both equilibrium and kinetic parameters of dynamic adsorption of radon based on discrete distribution of its activity over the sections of the adsorption column. These parameters can then be used to calculate and design gas delay systems. It can be useful for studying the sorption capacity of various materials relative to radon.

A sustainable, low-cost carbonaceous hydrochar adsorbent for methylene blue adsorption derived from corncobs

In this study, activated carbon from corncobs was successfully synthesized by hydrothermal carbonization and hydrochemical activation at low temperatures, followed by pyrolysis. A developed method of hydrochemical activation of hydrochar that uses only small amounts of chemicals is a promising approach. After activation, the activator residues in the hydrothermal product can constantly act as a chemical activator during pyrolysis to form corncob-activated carbon (AHC-KOH), which had specific surface area of 965.028 m2/g and oxygenated functional groups of 0.3780 mmol/g, 31.67 and 4 times, respectively, of those of the inactivated sample. AHC-KOH was used to study the adsorption characteristics of methylene blue (MB). The MB adsorption efficiency of AHC-KOH was the highest at 489.560 mg/g, which was considerably higher than that of activated carbons produced from other biomasses. The isotherm equilibrium and adsorbent kinetics parameters of MB adsorption on AHC-KOH were also determined using the Langmuir isotherm model (R2 = 0.99) and pseudo-second-order kinetic model (R2 > 0.99). Thus, the results indicate that an inexpensive adsorbent produced from corncobs using the above method is a promising material for wastewater treatment.

Nonlinear Fitting for Estimation of Adsorption Equilibrium, Kinetic and Thermodynamic Parameters of Methylene Blue onto Activated Carbon

Adsorption equilibrium, kinetics, and thermodynamics of methylene blue dye (MB) from aqueous solutions onto activated carbon (AC) synthesized from pomegranate peel was conducted in controlled batch systems. The effects of initial MB concentration, AC particle size, contact time, and temperature on adsorption were evaluated. Under the optimized conditions (i.e., contact time 120 min, pH ∼ 5, particle size 125 µm, dye concentration 20 mg/L, temperature 333 K, and 0.5 g AC/50 mL MB solution), the removal percentages can achieve ∼ 98.28%. The nonlinear method was conducted for estimating the equilibrium and kinetic parameters, where the equilibrium data were fitted to the Langmuir isotherm model. The Langmuir isotherm suggested a maximum monolayer adsorption capacity of 5.03 mg/g at 60 °C. The pseudo-second-order kinetic model provided the best fit to the experimental data compared with the pseudo-first-order. Kinetic studies showed that the adsorption equilibrium was rapidly established, with low activation energy entailed for adsorption (Ea; 15.60 kJ/mol). Thermodynamic parameters showed that the adsorption was spontaneous (−∆G° and +∆S°), exothermic (+∆H°), and favorable at ambient conditions.

Mitigating Water Pollution Using a Sustainable Biobased Low-Cost Adsorbent Derived From Mustard Straw

The present work is focussed on treating dye-laden polluted water by using a mustard straw-based activated carbon prepared using ZnCl2 and H3PO4 activation methods. The activation conditions based on the parameters reported in the literature are taken as follows: 700 °C activation temperature, impregnation ratio 2.0, and heating time 2 h. The textural and surface properties of mustard stalk activated carbon (MSAC) were studied by using SEM, nitrogen adsorption, and FT-IR, whereas its adsorption capacity was obtained using the methylene blue (MB) adsorption method. Activation of ZnCl2 and H3PO4 resulted in a BET surface area of 402 and 496 m2/g, respectively. The average pore diameter of the MSAC was found to be 2.13 and 2.59 nm for ZnCl2 and H3PO4 activation respectively. The Langmuir and Freundlich models were applied to evaluate the equilibrium parameters of MB adsorption. The monolayer adsorption capacity of MSAC by ZnCl2 and H3PO4 for MB removal from the Langmuir model were 122.25 and 213.21 mg/g respectively. Activation with H3PO4 was found to be more effective in modifying the structure of the mustard straw when compared with ZnCl2 and also it resulted in a higher adsorption capacity of MB. The present work highlights that the MSAC produced using H3PO4 activation is a low-cost bio-based adsorbent using abundant agricultural by-product namely mustard straw, and this adsorbent can be used in numerous industrially important applications.

Improvement of Methanol Production from Carbon Dioxide and Hydrogen by a Sorption Enhanced Reaction Process

Climate change caused by carbon dioxide emissions is one of the most concerning problems worldwide. CCS (Carbon Capture and Storage) technologies are not enough to achieve climatic goals, so there is the need to embrace new processes, like CCUS (Carbon Capture Utilization and Storage). Hydrogenation of CO2 to produce methanol is one of the most feasible ways, however, the conversion rates are small. It could be solved by a SERP process (Sorption Enhanced Reaction Process), displacing the reaction equilibrium through the adsorption of the products, water and methanol. There is scarce information of the adsorption of these compounds, especially methanol, at the reaction temperature (200-300 oC). In this work, adsorption equilibrium and diffusional parameters for water and methanol are obtained for the design of a SERP process. 3A zeolite, silica gel and silica-alumina have been studied at temperatures of 200-300oC by a chromatographic method. The performance of these adsorbents in a PSA reactor for CO2 hydrogenation with a commercial catalyst (Cu/ZnO/Al2O3) is compared by simulation.

Non-Linear Regression Applied to the Sorption of Bisphenol A on Multi-Walled Carbon Nanotubes in Aqueous Systems.

In the present study, equilibrium parameters of adsorption of bisphenol A (BPA) on multi-walled carbon nanotubes were determined using non-linear Langmuir and Freundlich sorption models and regression methods were applied. In the calculations, some error functions were applied in the non-linear regression analysis, the best fit between the data being obtained, for a minimum error distribution. Non-linear regression analysis and the error distribution suggested Langmuir isotherm model the best one for estimation of equilibrium parameters. The results will be further used in environmental applications for BPA removal from natural waters, taking into account the spontaneous character of the adsorption process, the endocrine disrupting effect of BPA and the reduced toxicological effects of the impregnated sorbents.

Adsorption of difluoromethane onto activated carbon based composites: Thermophysical properties and adsorption characterization

In an attempt to promote research on adsorption cooling systems, novel activated carbon-based composite adsorbents have been studied for thermophysical properties and adsorption characterization with difluoromethane (HFC 32) refrigerant. High surface area activated carbon of type Maxsorb III has been selected as the primary constituent of adsorbent composites, with H25 graphene nanoplatelets (GNPs), 1-Hexyl-3-methylimidazolium bis(trifluormethylsulfonyl)imide ([HMIM][Tf2N]) ionic liquid, and Polyvinyl alcohol (PVA) binder in varying fractions. The various thermophysical properties such as surface area and porosity, specific heat capacity, and thermal conductivity have been experimentally evaluated. The thermal diffusivities have been measured in two different planes of the composites: parallel and perpendicular to the direction of the compression. It has been observed that the perpendicular plane has significantly higher thermal diffusivities (up to 2.32 times) over the parallel plane of the composites. Besides, a considerable improvement in thermal conductivity of up to 65.6 times is observed over powdered activated carbon. Adsorption uptake characteristics are studied gravimetrically for the composite samples in the temperature range of 30–70°C. Dubinin-Astakhov (D-A) and Tóth models are fitted successfully for the adsorption isotherms, with the D-A model seen to offer better fits. Further, the specific and volumetric cooling energies are estimated for the consolidated carbon composites based on the respective D-A adsorption equilibrium parameters and thermophysical properties of the working pairs. Significant enhancements in volumetric cooling energy up to 78% over that of powdered activated carbon are seen for the consolidated composites.

Experimental and numerical investigations on the separation performance of [Cu(INA)2] adsorbent for CH4 recovery by VPSA from oxygen-bearing coal mine methane

In this work, [Cu(INA)2] metal–organic framework (MOF) adsorbent has been used to recover methane from coal mine methane (CMM) using vacuum pressure swing adsorption process (VPSA). The adsorption capacity and separation performance were investigated at one bar and different temperatures (288 K, 298 K and 308 K) for methane, nitrogen and oxygen. The breakthrough curves of the single component and gas mixture were experimentally obtained through a dynamic fixed-bed experiment. Based on the LDF model, the mass transfer coefficient was investigated according to the experimental breakthrough curves. VPSA process was also developed using adsorption equilibrium and kinetics parameters to achieve the maximum recovery of methane. The VPSA operational parameters were optimized involving feed gas flow rate, adsorption time, adsorption pressure and evacuation pressure. The maximum 90% recovery of methane with 50% purity can be achieved.

Mathematical modeling of arsenic(V) adsorption onto iron oxyhydroxides in an adsorption-submerged membrane hybrid system

The adsorption of arsenic (V), As(V), on two porous iron oxyhydroxide-based adsorbents, namely, micro-sized tetravalent manganese feroxyhyte (μTMF) and granular ferric hydroxide (μGFH), applied in a submerged microfiltration membrane hybrid system has been investigated and modeled. Batch adsorption tests were carried out to determine adsorption equilibrium and kinetics parameters of As(V) in a bench-scale slurry reactor setup. A mathematical model has been developed to describe the kinetic data as well as to predict the As(V) breakthrough curves in the hybrid system based on the homogeneous surface diffusion model (HSDM) and the corresponding solute mass balance equation. The kinetic parameters describing the mass transfer resistance due to intraparticle surface diffusion (Ds) involved in the HSDM was determined. The fitted Ds values for the smaller (1–63 μm) and larger (1–250 μm) diameter particles of μGFH and μTMF were estimated to be 1.09 × 10−18 m2/s and 1.53 × 10-16 m2/s, and 2.26 × 10−18 m2/s and 1.01 × 10-16 m2/s, respectively. The estimated values of mass transfer coefficient/ kinetic parameters are then applied in the developed model to predict the As(V) concentration profiles in the effluent of the hybrid membrane system. The predicted results were compared with experimental data for As(V) removal and showed an excellent agreement. After validation at varying adsorbent doses and membrane fluxes, the developed mathematical model was used to predict the influence of different operation conditions on As(V) effluent concentration profile. The model simulations also exhibit that the hybrid system benefits from increasing the amount of adsorbent initially dosed and from decreasing the membrane flux (increasing the contact time).

Removal of Methylene Blue in Aqueous Solution by Economic Adsorbent Derived from Apricot Stone Activated Carbon

Quantitative adsorption kinetic and equilibrium parameters for methylene blue (MB) used in the textile industry from aqueous solutions were reported in this study using pHPZC and UV-visible absorption spectroscopy. The effects of adsorbent dosage (1–10 g/l), agitation speed (100–1200 rpm), particule size (63 µm to 2 mm), initial dye concentration (4–15 mg/l), contact time, pH (2–14), and temperature (298–338 K) were determined to find the optimal conditions for adsorption. The FTIR spectroscopy is used to get information on interactions between the adsorbent and MB. The mechanism of adsorption of MB dyeing onto Apricot Stone Activated Carbon (ASAC) was investigated using the pseudo first-order, pseudo second-order kinetic, Elovich and intraparticles diffusion models. The adsorption isotherms of MB onto ASAC are determined and correlated with common isotherm equations. The smaller RMSE value obtained for the Langmuir model indicates the better curve-fitting and the monolayer adsorption capacity of MB is found to be 46.03 mg/g at 25 °C and 88.50 mg/g at 70 °C and pH 10. The evaluation of thermodynamics parameters such as the negative free energy ΔG° (+2.70025 to −1.76666 kJ/mol) and positive enthalpy change ΔH° (28.87613 kJ/mol) indicated a spontaneous and endothermic nature of the reaction with chemisorption process. This study in tiny batch gave rise to encouraging results, and we wish to achieve the adsorption tests in column mode under the real conditions applicable to the treatment of industrial effluents. The present investigation showed that ASAC is potentially a useful adsorbent for the heavy metals and dyes.

Performance of apricot stone to remove dyes from aqueous solutions – Equilibrium, kinetics, isotherms modeling and thermodynamic studies

This study investigates the potential use of activated carbon prepared from Apricot stone with H3PO4 activation as an adsorbent and its ability to removal dyes from aqueous solutions. The quantitative kinetics and equilibrium adsorption parameters for activated carbon ASAC were studied by UV visible absorption spectroscopy. ASAC with a specific surface area (88.04 m2/g) respectively are characterized by the Brunauer-Emmett-Teller (BET) method and the point of zero charge pHpzc.The infrared spectra of (ASM) were recorded with Fourier transform Bomen-Michelson type spectrometer by mixing (AS) sample (∼2% wt.) with KBr of spectroscopic in a range of 4000–400 cm−1. The adsorptive properties of the adsorbent with dyes are conducted at variable process parameters such as initial pH, adsorbent dosage, initial dye ion concentration, contact time and temperature were investigated in their respective range and their optimum conditions were ascertained using batch mode operation to find the optimal conditions for a maximum adsorption. The equilibrium adsorption data for dyes onto ASAC is analyzed by the Langmuir, Freundlich, Elovich, and Temkin models. The results indicate that the Langmuir model provides the best correlation. Kinetic parameters; rate constants, equilibrium adsorption capacities and determination coefficients, for each kinetic and isotherm model were calculated and discussed. The pseudo-second order model fit the kinetic data better than the pseudo-first order model and the intraparticle diffusion and film diffusion mechanisms jointly influenced the adsorption process but the latter was the rate-controlling step.The adsorption isotherms at different temperatures have been used for the determination of thermodynamic parameters such as Free Energy (ΔGo), Enthalpy (ΔHo), Entropy (ΔSo) and Activation Energy (Ea) of adsorption. The negative ΔGo and positive ΔHo values indicate that the overall adsorption is spontaneous and endothermic in nature.

Separation of the propane propylene mixture with high recovery by a dual PSA process

Propylene is a very important raw material in the petrochemical industry. A key step in its production is propane/propylene separation, where energy consumption and the degree of propylene recovery achieved have a strong impact on the economy of the process. A Dual PSA process has been designed for the separation of a 50:50 molar propane/propylene mixture using zeolite 13X as adsorbent. Kinetic and equilibrium adsorption parameters reported in the literature (Da Silva, F.A., Rodrigues A.E., 2001. AIChE J. 47, 341–57) have been used. The process can produce polymer-grade propylene (purity > 99.5%) with recovery higher than 99.5%, which is above the recovery achieved in other PSA processes studied in the literature for an equimolar propane/propylene mixture. Energy consumption is 38% lower than required by conventional distillation.