Adsorption Enthalpy Research Articles

A Route to Understanding the Ethane Adsorption Selectivity of the Zeolitic Imidazolate Framework-8 in Ethane-Ethylene Mixtures.

Ethylene production has a negative environmental impact, with its separation step being one of the major contributors of pollution. This has encouraged the search for energy-efficient alternatives, among which the adsorptive separation of ethane and ethylene stands out. ZIF-8 is a molecular sieve that is potentially useful for this purpose. It is selective to ethane, an exceptional property that remains unexplained. Furthermore, the adsorption of ethane and ethylene above room temperature, such as at steam cracking process outlet temperatures, has not been addressed either. This work aims to fill this knowledge gap by combining experiments at very low volumetric fillings with density-functional theory modelling methods. Adsorption isotherms of ethane and ethylene on ZIF-8 at pressures below 0.3 bar and 311 K, 333 K, and 363 K were measured using zero-length column chromatography. The low-pressure domain of the isotherms contains information on the interactions between the adsorbate molecules and the adsorbent. This favors the understanding of their macroscopic behavior from simulations at the atomic level. The isosteric enthalpy of adsorption of ethane remained constant at approximately -10 kJ/mol. In contrast, the isosteric enthalpy of adsorption of ethylene decreased from -4 kJ/mol to values akin to those of ethane as temperature increased. ZIF-8 selectivity to ethane, estimated from ideal adsorbed solution theory, decreased from 2.8 to 2.0 with increasing pressure up to 0.19 bar. Quantum mechanical modelling suggested that ethylene had minimal interactions with ZIF-8, while ethane formed hydrogen bonds with nitrogen atoms within its structure. The findings of this research are a platform for designing new systems for the adsorptive separation of ethane and ethylene and thus, reducing the environmental impact of ethylene production.

Metal-Organic Frameworks for Phthalate Capture.

Indoor air contamination by phthalate ester (PAE) derivatives has become a significant concern since traces of PAEs can cause endocrine disruption, among other health issues. PAE abatement from the environment is thus mandatory to further ensure a good quality of indoor air. Herein, we explored the physisorption-based capture of volatile PAEs by metal-organic frameworks (MOFs). A high-throughput computational screening approach was first applied on databases compiling more than 20,000 MOF structures in order to identify the best MOFs for adsorbing traces of dimethyl phthalate (DMP), considered as a representative molecule of the family of PAE contaminants. Among the 20 top candidates, MOF-74(Ni), which combines substantial DMP uptake at the 10 ppm concentration level (∼0.20 g g-1) with high adsorption enthalpy at infinite dilution (-ΔHads(DMP),0 = 109.9 kJ mol-1), was revealed as an excellent porous material to capture airborne DMP. This prediction was validated by further experiments: gravimetric sorption isotherms were carried out on MOF-74(Ni), replacing DMP by dimethyl maleate (DMM), a molecule with a higher vapor pressure and indeed easier to manipulate compared to DMP while mimicking the adsorption behavior of DMP by MOFs, as evidenced by Monte Carlo calculations. Notably, saturation of DMM by MOF-74(Ni) (∼0.35 g g-1 at 343 K) occurs at very low equivalent concentration of the sorbate, i.e., 15 ppm, while half of the DMM molecules remain trapped in the MOF pores, even by heating the system up to 473 K under vacuum. This computational-experimental study reveals for the first time the potential of MOFs for the capture of phthalate ester contaminants as vapors of key importance to address indoor air quality issues.

Solvent-free synthesis of ZrO2 nanoparticles/nitrogen-rich two-dimensional carbon nanosheet composites as efficient catalysts for ORR

An innovative, high-performance, non-noble-metal-based oxygen reduction reaction (ORR) catalyst must be developed utilizing a new and cost-effective technique. ZrO2 has the merits of high stability, low toxicity, good catalytic activity, and low enthalpy for atomic oxygen adsorption. However, the poor conductivity restricts its application as an ORR catalyst. Here, we successfully prepared ZrO2 nanoparticles / nitrogen-rich two-dimensional carbon nanosheet composites as ORR catalysts using a straightforward, solvent-free, one-step pyrolysis approach. Due to the unique component and structure characteristics, ZrO2@N-C-900 demonstrates remarkable ORR performances in alkaline electrolytes, such as high half-wave potential (0.82 V vs. RHE), higher current density (JL = 6.4 mA cm−2), and outstanding long term stability (95 % for 36,000 s). Especially, when used in a Zn-air battery, ZrO2@N-C-900 exhibited a power density of 148 mW cm−2, exceeding that of 20 % Pt/C.

Understanding Microcystin-LR separation by hydrophobic deep eutectic solvents with COSMO simulation and experimental findings

Microcystin-LR (MCLR) is considered the most toxic compound in the large family of Microcystin. This study evaluates MCLR separation by hydrophobic deep eutectic solvents (HDESs) for the separation of Microcystin-LR from solutions. Conductor-like Screening MOdel (COSMO) was utilized to evaluate 528 type V HDES by computing the σ-surfaces, σ-profiles, σ-potentials, ln(activity coefficients), and excess enthalpy of adsorption. According to the adsorption thermodynamic, the HDES based on tetrabutylammonium bromide (TBAB) exhibits significantly higher affinity towards MCLR, with the ln(activity coefficient) being as low as −14.3, indicating strong separation capability. Excess enthalpy results reveals that the interactions between HDES and MCLR are predominantly governed by Vander Waals interactions, which exhibit >10 times higher enthalpic release compared to that of hydrogen bonding. The experimental results show that 79.85 ± 0.75 % MCLR removal can be achieved by TBAB: acetic acid (1:1 ratio). Finally, Virtual models for property Evaluation of chemicals within a Global Architecture (VEGA) analysis was performed on the best performing HDES (TBAB:acetic acid, TBAB: arginine, and TBAB: glutamic acid) to evaluate human and environmental toxicity endpoints, i.e., mutagenicity, carcinogenicity, acute toxicity, and bioconcentration factor (BCF). The results show that the HDES exhibit low toxicity and negligible environmental concerns.

Theoretical Study of Non-Isothermal Gradient Elution Liquid Chromatography.

A two-component model of gradient elution chromatography is investigated to theoretically study the effects of simultaneous variations in temperature and solvent strength on the retention behaviors of elution profiles in thermally insulated liquid chromatographic columns. The gradient elution technique is based on the gradual increase or decrease in eluent strength during the chromatographic operation by varying the composition of the mobile phase. The enthalpy of adsorption is primarily responsible for internal temperature variations inside the column, as heat adsorbs during the adsorption process and releases in the desorption phase. Both types of variations change the propagation speeds of moving pulses inside the column which can lead to better separation of the components and a reduction in the recycling time for the next injection. The equilibrium dispersive model (EDM) coupled with the energy balance equation for temperature and transport equation for the volume fraction of the solvent is utilized to simulate this complex process. The resulting nonlinear model equations are approximated by applying a semi-discrete second-order finite volume scheme. The numerical solutions are used to study the impact of a gradient starting and ending times, volume-fraction of the solvent, solvent strength parameter, the slope of gradient, enthalpy of adsorption, injection temperature, and the ratio of specific heats on the concentration profiles.

CO2/H2O adsorption and co-adsorption on functionalized and modified mesoporous silicas

A challenging current objective in the world is the decrease of the CO2 emissions in the air. Adsorption is an economically and environmentally favorable process but, it requires performant adsorbents meaning porous materials with high CO2 adsorption capacities and good affinity even in presence of water. In this study, we propose to measure not only the CO2 adsorption capacities and affinities but also the water adsorption capacities independently and the co-adsorption of these molecules on type SBA mesoporous silicas.Two different approaches have been explored to improve the CO2 adsorption on such materials: one relies on the silica structure modification by using the BTESE (1,2-Bis(triethoxysilyl)ethane) as silicon source to increase the material hydrophobicity. The other one is based on the grafted SBA silica with amine groups (3-(triethoxysilyl) propylamine called APTES) to significantly improve the CO2 affinity.Then CO2 adsorption capacities, affinities, and enthalpies, have been measured by coupling manometry and calorimetry at 303K and compared to H2O adsorption. In the case of the modified materials, the CO2 affinity and capacity decrease as the ethyl groups amount increases, relevant of the fact that for both H2O and CO2 adsorption the same adsorption sites (silanols) are involved. In the case of the grafted materials, CO2 adsorption affinity and capacity are increased, nevertheless it is less efficient when the grafted groups amount increase.Competitive breakthrough adsorption experiments have confirmed these trends. In humid conditions at 10%RH, 20%RH and 50%RH, H2O enhances CO2 adsorption for modified and grafted materials contrary to the dry sample.

Customized pore fluorination in a microporous metal-organic framework for efficient ethane/ethylene separation

High efficiency and energy-saving separation of C2H6/C2H4 mixtures to product high purity C2H4 is vital and very meaningful industrial task. However, it remains a formidable challenge to fabricate high-performance adsorbents with simultaneous high C2H6 uptake and moderate adsorption enthalpy. Here, we reported a microporous MOF (NKU-0821) with suitable aperture size and F atoms functional pore surface, which can capture efficiently C2H6 from C2H6/C2H4 mixture. Single-component adsorption experiments show that NKU-0821a (activated NKU-0821) exhibits preferred C2H6 uptake at the full-pressure region than C2H4. The corresponding C2H6 adsorption enthalpy of NKU-0821a is 27.3 kJ mol−1, which is lower than most famous C2H6-selective MOFs. The calculation of IAST selectivity and breakthrough experiments have shown NKU-0821a can effectively separate C2H6/C2H4 mixture under simulated industrial conditions. Moreover, GCMC simulations revealed the key role of fluorous surface.

Lewis acidity and substituent effects influence aldehyde enolization and C–C coupling in beta zeolites

The Claisen-Schmidt condensation between propanal and benzaldehyde was used a model aldol reaction to assess the reactivity of tetravalent framework Lewis acid sites (Ti, Zr, Sn, Hf) in hydrophobic beta zeolites (M-*BEA) and determine rates of enolization and carbon–carbon (C–C) bond formation along with selectivities among cross- and self-condensation products. Rates of enolate formation during liquid phase reactions (393 K) span nearly 100-fold, depending on the identity of the metal heteroatom, and correlate with enthalpies for adsorption of pyridine in liquid-filled pores of M-*BEA, as measured by isothermal titration calorimetry. Comparisons among adsorption enthalpies suggest that tetrahedrally substituted Zr and Hf are more effective Lewis acids than Sn and Ti for coordinating aldehydes within these environments. Ratios of initial rates of C–C coupling between propanal and benzaldehyde compared to propanal self-condensation were less than unity for all M-*BEA catalysts. These selectivity patterns reflect the combination of electronic and steric effects imposed by the larger aromatic substituent at the carbonyl carbon atom and its concerted interactions with the Lewis acid site, which causes rates for nucleophilic attack of enolates to benzaldehyde to be far less than those to propanal.

Removal of lead (II) from aqueous solution using epichlorohydrin cross-linked shrimp waste-derived chitosan based @ calcium phosphates biocomposite: Experimental study and computational approach

An economical composite has been synthesized utilizing chitosan derived from discarded shrimp shells and hydroxyapatite extracted from waste bovine bones. This research delves into the composite's adsorption properties for the purpose of eliminating Pb ions from wastewater. The structure of this novel composite has been meticulously examined through techniques including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET) analyses. Factors such as concentration, time, temperature, adsorbent dosage, and pH have been scrutinized to understand their impacts on lead ion adsorption. Concurrently, relevant adsorption parameters have been ascertained. Notably, the adsorption capacity, as determined by the Langmuir model, was found to be 154.88 mgg−1. To elucidate the adsorption kinetics, the PSO and IP models were employed. The adsorption enthalpy exhibited a positive value, while the free enthalpy displayed negativity. The mechanism governing adsorption was expounded upon through theoretical calculations, which concurred with and validated the experimental results.

Separation of the Chlorofluorocarbon (CFC) CCl2F2 from N2 in NaY Zeolite, in MIL-127(Fe) and in the two Carbon Nanotubes CNT (9,9) and CNT (11,11)

Four well-suited porous materials for the selective adsorption of the most prominent CFC, which is CCl2F2, from the air are carbon nanotubes CNT (9,9) and CNT (11,11), NaY zeolite, and the Metal Organic Framework MIL-125(Fe). The adsorption has been investigated through molecular simulations. Simulation results and theoretical considerations show that reasons for the extraordinarily high selectivity in all four cases were found to be the differences in the enthalpy of adsorption for the various adsorbed gases rather than steric reasons. The four adsorbate–adsorbent systems have been examined at different temperatures, pressures, and concentration ratios in the mixture. Among them, the carbon nanotube CNT (11,11) exhibited the highest selectivity, reaching up to 104.

Adsorption behavior of soil fulvic acid on crystal faces of kaolinite and goethite: Described by CD-MUSIC model

The interaction between organic matter (OM) and minerals has significant impacts on the mineralization process and rate of OM, and can protect part of organic carbon in soils. In this study, the complex species of fulvic acid (FA) on the surface of minerals (kaolinite and goethite) and the corresponding thermodynamic characteristics were investigated with the CD-MUSIC model and isothermal titration calorimetry. With increasing pH, the adsorption of kaolinite for FA increased at pH < 5.5 and decreased at pH > 5.5, which might be due to the binding of carboxyl groups of FA onto the positively charged sites of O-face and edge-face. However, that of goethite consistently decreased with increasing pH from 3.5 to 9.0 due to an increase in electrostatic repulsion. The fraction of FA was mainly adsorbed on the edge-face and O-face to form inner sphere complexes on kaolinite and outer sphere complexes on goethite. Molar adsorption enthalpies indicated that FA was adsorbed through two site types on kaolinite, while that was one site type on goethite. In addition, the molar enthalpy was more closely associated with inner sphere complexation for kaolinite, while with outer sphere complexation for goethite. The findings shed new light on the adsorption behavior and complexation mechanism of OM on the crystal faces of mineral-water interface.

Effect of Water on CO2 Adsorption on CaNaY Zeolite: Formation of Ca2+(H2O)(CO2), Ca2+(H2O)(CO2)2 and Ca2+(H2O)2(CO2) Complexes.

Efficient CO2 capture materials must possess a high adsorption capacity, suitable CO2 adsorption enthalpy and resistance to water vapor. We have recently reported that Ca2+ cations exchanged in FAU zeolite can attach up to three CO2 molecules. Here we report the effect of water on the adsorption of CO2. Formation of Ca2+(H2O)(CO2), Ca2+(H2O)(CO2)2 and Ca2+(H2O)2(CO2) mixed ligand complexes were established. The Ca2+(H2O)(CO2) species are readily formed even at ambient temperature and are characterized by ν(12CO2) and ν(13CO2) infrared bands at 2358 and 2293 cm-1, respectively. The Ca2+(H2O)(CO2)2 species are produced at low temperature and are identified by a ν(13CO2) band at 2291 cm-1. In the presence of large amounts of water, Ca2+(H2O)2(CO2) complexes were also evidenced by ν(12CO2) and ν(13CO2) bands at 2348 and 2283 cm-1, respectively. The results demonstrate that, although it has a negative effect on CO2 adsorption uptake, water in moderate amounts does not block CO2 adsorption sites.

Influence of potential contaminants on I2 and CH3I adsorption onto zeolitic imidazolate frameworks (ZIFs) using GCMC simulations

Zeolitic imidazolate frameworks (ZIFs) are one type of promising volatile radioiodine sorbents due to their chemical/thermal stability, tunable structures, and high iodine adsorption capacity. However, the inhibiting effect of contaminants on volatile iodine adsorption onto ZIFs remains unclear. Herein, the adsorption of volatile iodine (I2 and CH3I) onto five different ZIFs (SALEM-2, ZIF-8, ZIF-Cl, ZIF-90, and ZIF-65) and adsorption selectivity over ten contaminants were investigated by using grand canonical Monte Carlo (GCMC) methods. It is found that the I2 adsorption isotherm could be accurately described by the Langmuir-Freundlich model. Furthermore, the adsorption quantity of CH3I is much smaller than that of I2 at the same partial pressure. Ten potential gaseous contaminants that existed in a reprocessing plant or nuclear reactor accident, including CO, NO, H2O, CH4, C2H6, CH3OH, CH3CH2OH, Cl2, CH3Cl, and C6H6, were considered for calculation of binary adsorption. The results show that C6H6 has the largest adsorption enthalpy among all contaminants, whereas CO, NO, H2O, and CH4 have the smallest. Moreover, CO, NO, H2O, and CH4 have negligible effects on volatile iodine adsorption onto ZIFs. In contrast, except for CH3I adsorption onto ZIF-65, C6H6 has the strongest inhibiting effect since benzene could occupy the adsorption sites of iodine in ZIFs. This work not only provided the fundamental knowledge of volatile iodine adsorption on ZIFs but also proposed a new strategy to evaluate the inhibiting effect of contaminants. It could be helpful for future screening and design of better sorbents.

Theoretical verification on adsorptive removal of caffeine by carbon and nitrogen-based surfaces: Role of charge transfer, π electron occupancy, and temperature

Eliminating an emerging water pollutant, caffeine molecules, from an aqueous solution using carbon and nitrogen-based adsorbents is of significant interest to public health. These adsorbents have been shown to have decent adsorption capacity toward caffeine due to their surface functionality. Therefore, screening various carbon and nitrogen-based surfaces can be a better option for high-performance adsorbents to remove caffeine efficiently from wastewater. Herein, we present combined first principles and molecular dynamics quantification of the adsorption enthalpies of caffeine molecules on the possible active sites of carbon and nitrogen-based adsorbents (graphene, phagraphene, graphdiyne, single-wall carbon nanotube, fullerene, and graphitic carbon nitride) with the incorporation of Van der Waals interactions. From the DFT calculations, N-doped carbon surfaces show the highest adsorption energies of single and dimer CAF compared to pristine carbon-based adsorbents. A charge density difference and Bader charge analysis display that high charge transfer occurs between the caffeine's oxygen and the surface's nitrogen atoms. An abundance of π-electrons from the nitrogen atoms, composed of large electron clouds of aromatic rings on the graphitic carbon surface, tends to favor extensive π-π interactions with the caffeine molecule. The high value of pz electron occupancy (1.445) of N in the hexagonal ring of the graphitic surface transfers additional charge transfer, which leads to strong adsorption energy of CAF than pristine surfaces. Also, the g-C3N4 surface adsorbs the CAF molecule with higher adsorption than other N-doped carbon surfaces due to the high pz_eo (1.5448) of N atoms on the surface. At 310 K, the water molecules' kinetics aids the single and dimer caffeine molecules to adsorb with the highest adsorption energies on the active sites of g-C3N4 surfaces than graphene adsorbent.

Activity and Durability Patterns of 45 Binary Noble Metal Alloy Nanoparticle Variants for Commercial Diesel Exhaust Aftertreatment

AbstractCommercial diesel oxidation catalysis mainly uses monometallic and bimetallic Pt−Pd‐based catalysts, but alloying with different elements has rarely been done systematically under industrial testing conditions. 45 binary alloys made of platinum and a selected 1st and 2nd‐row transition metal, platinum group element, or coin metal were synthesized via a scalable laser synthesis method. Then, catalytic performance and durability were evaluated for one diesel oxidation and two ammonia‐slip environments. The results show the highest activity when the adsorption enthalpy of molecular oxygen of the alloy was similar to the value of Pt. Furthermore, the durability of the alloy catalysts was found to increase with the melting point of the 2nd element Pt was alloyed with, even at molar fractions. Our results further indicate beneficial synergies beyond the binary systems underlining the possibility of further improvements by considering ternary or multinary alloys, which are accessible via laser synthesis.

Trisurethane functionalized sulfonamide based polymeric sorbent: Synthesis, surface properties and efficient mercury sorption from wastewater

In this study, trisurethane modified sulfonamide based polymeric adsorbent was prepared starting from reaction with chlorosulfonated poly (styrene) (PS) beads and tris(hidroxymethyl) aminometane. Hydroxyl functions of the adsorbent were reacted with butyl isocyanate in the presence of dibutyltin dilaurate as a catalyst at 60 0C for 48 h to obtain tris urethane functional polymeric adsorbent (PS-TUR). Spectroscopic and morphological characterizations of the polymeric adsorbents were carried out using scanning electron microscopy (SEM-EDX), infrared spectrophotometry (FTIR), XPS and analytical methods.The surface properties of PS-TUR were investigated for the first time with the inverse gas chromatography technique at infinite dilution before adsorption studies. The dispersive surface energy of adsorbent was determined according to the method of Schultz (55.54–61.73 mJ m−2) and Dorris-Gray (57.70–67.03 mJ m−2). Adsorption enthalpy and Gibbs free energy were calculated according to this technique and it was determined that the adsorption was exothermic and spontaneous. As a result of the analyzes made with this technique, it was determined that the PS-TUR adsorbent surface was acidic (KD/KA=0.27<1) and optimum conditions (pH: 7, dose: 0.10 g) were determined for the effective adsorption of Hg (II) ions. Surface acidity-basicity behavior of sorbent was determined by isoelectric point (IEP: 6.20) and pHpzc (5.81) analyses.Batch adsorption studies of the PS-TUR adsorbent were carried out as a function of adsorbent dosage, pH, initial metal ion concentration (0.0025–0.1000 mol/L), and kinetically. After determination of optimum adsorbent dosage was found as 100 mg, mercury sorption capacity of PS-TUR adsorbent was found as 511.50 mg g−1 adsorbent.Desorption studies were carried out using glacial acetic acid and studies demonstrated that PS-TUR adsorbent is regenerable and can be successfully used for four adsorption–desorption cycles without significant loss its capacity.Also, PS-TUR adsorbent shows selectivity with high sorption capacity towards mercury as compared to other metal ions.

Microgravimetric Modeling-A New Method for Extracting Adsorption Parameters of Functionalized MIL-101(Cr).

As a volatile air pollutant, formaldehyde can enter people's living environment through interior decoration, furniture and paint, causing serious harm to human health. Therefore, it is necessary to develop a sensor for the real-time detection of formaldehyde in low concentrations. According to the chemical interaction between amino groups and formaldehyde, a MIL-101(Cr) aminated-material-based formaldehyde cantilever sensor was prepared, of which ethylenediamine- functionalized MIL-101(Cr) named ED-MIL-101(Cr)) showed the best gas sensing performance. Using quasi-in situ infrared spectroscopy, ED-MIL-101(Cr) was found bound to formaldehyde through a Schiff base. The adsorption enthalpy of formaldehyde-bound ED-MIL-101(Cr) was -52.6 kJ/mol, which corresponds to weak chemical adsorption, so the material showed good selectivity. In addition, ED-MIL-101(Cr) has the most active sites, so its response value to formaldehyde is larger and it takes longer to reach saturation adsorption than bare MIL-101(Cr). Through the research on the gas sensing performance of functionalized MIL-101(Cr) material, we found that it has a strong application potential in the field of formaldehyde monitoring, and the material performance can be quantitatively and accurately evaluated through combining calculation and experimentation for understanding the gas sensing mechanism.

Water in PHI Nanopores: Modeling Adsorption, Solvent Structure, and Thermodynamics.

We modeled the uptake of water molecules into the nanopores of potassium-polyheptazineimide (K-PHI), a 2D covalent material that is one of the best water-splitting photocatalysts to date possessing experimentally reported strong water binding. In the current models, we find that first water molecules are bound with -94.5 kJ/mol, i.e., twice the cohesion energy of water and one of the highest adsorption enthalpies reported so far. This strong binding proceeds unexpectedly on a similar enthalpy level until the pore is filled, while the binding strength is passed through a conjugated water network. The tight binding is also expressed in calculated, strongly shortened O-O distances, which are on average about 5% shorter than in bulk water, which corresponds to a much higher water density, for a 2D structure above 1.1 g/ cm3. The H-bridges are strongly aligned in the direction perpendicular to the covalent planes, which could give reasons for the experimentally observed ultrahigh ion fluxes and conductivity of K-PHI membranes. Decomposition of the adsorption energy into components reveals an unexpectedly high charge transfer contribution, where the partly naked K+ ions play a key role. The latter fact not only offers a new structural lead motif for the design of more strongly, but reversibly binding adsorption materials involving metal ions on their surface but also puts cations as known cofactors in enzymes into a new light.

Batch and continuous adsorption of Cd(II) and Pb(II) on polycarboxylated sugarcane bagasse

A bioadsorbent composed of polycarboxylated sugarcane bagasse (PSB) was prepared in a one-step reaction by the esterification of sugarcane bagasse hydroxyl groups with butane-1,2,3,4-tetracarboxylic dianhydride. 13C SS NMR measurements showed that 0.3 butane-1,2,3,4-tetracarboxylic acid units were grafted per cellobiose unit. PSB was used in the batch adsorption of Cd(II) and Pb(II) from mono-, bi-, and multicomponent aqueous solutions. For upscaling of the technology aiming at practical applications, evaluation was made of 4 cycles of continuous adsorption of Cd(II) and Pb(II) on PSB in a fixed-bed column. The maximum adsorption capacities for Cd(II) and Pb(II) on PSB in batch and continuous modes were 0.55 and 1.164 mmol g−1 (62 and 241.2 mg g−1), and 0.58 and 0.71 mmol g−1 (65 and 153 mg g−1), respectively. The standard adsorption enthalpy change (ΔadsH°) values for Cd(II) and Pb(II) were 8.6 ± 0.5 and − 0.28 ± 0.03 kJ mol−1, respectively. The interactions involved in the adsorption of Cd(II) and Pb(II) on PSB were investigated. Multicomponent studies showed that Pb(II) and Cd(II) acted to suppress the adsorption of each other. In the presence of Cu(II) and Zn(II), the adsorption capacity followed the order: Pb(II) > Cu(II) > Cd(II) > Zn(II). Batch and continuous adsorption-desorption studies showed that PSB could be reused in at least 4 successive cycles, with desorption efficiencies of 88–100 %, which is essential for minimizing waste generation and reducing process costs.

Nigella sativa-Manganese Ferrite-Reduced Graphene Oxide-Based Nanomaterial: A Novel Adsorbent for Water Treatment.

In this study, a novel nanohybrid composite was fabricated via the incorporation of manganese ferrite (MnFe2O4) nanoparticles into the integrated surface of reduced graphene oxide (rGO) and black cumin seeds (BC). The nanohybrid composite was prepared by a simple co-precipitation method and characterized by several spectroscopic and microscopic techniques. The characterization analysis revealed that the rGO-BC surface was decorated with the MnFe2O4. The strong chemical interaction (via electrostatic and H-bonding) between the integrated surface of rGO-BC and MnFe2O4 nanoparticles has been reported. The prepared composite was highly porous with a heterogeneous surface. The average size of the prepared composite was reported in the ranges of 2.6-7.0 nm. The specific surface area of the prepared composite was calculated to be 50.3 m2/g with a pore volume of 0.061 cc/g and a half pore width of 8.4 Å. As well, many functional sites on the nanohybrid composite surface were also found. This results in the excellent adsorption properties of nanohybrid composite and the effectual elimination of methylene blue dye from water. The nanohybrid was tested for various linear isotherms, such as Langmuir and Freundlich, for the adsorption of methylene blue dye. The Freundlich isotherm was the well-fitted model, proving the adsorption is multilayer. The maximum Langmuir adsorption capacity of nanohybrid composite for methylene blue was reported to be 74.627 mg/g at 27 °C. The adsorption kinetics followed the pseudo-second-order recommended surface interaction between the dye and nanohybrid composite. The interaction between methylene blue and the nanohybrid composite was also confirmed from the FTIR spectrum of the methylene blue-loaded adsorbent. The rate-determining step for the present study was intraparticle diffusion. Temperature-dependent studies of methylene blue adsorption were also carried out to estimate adsorption's free energy, enthalpy, and entropy. The methylene blue adsorption was feasible, spontaneous, and endothermic. A comparison study revealed that the present materials could be successfully prepared and used for wastewater treatment.