Binary Adsorption Research Articles

Process intensification in binary adsorption of VOC-water vapor on zeolite in a countercurrent fluidized bed adsorber

In this study, fast ideal adsorbed solution theory was coupled with a two-phase bubbling bed approach to describe the adsorption of volatile organic compounds (VOCs) on zeolite in the presence of water vapor in a multistage fluidized bed adsorber. The binary adsorption of VOC-water vapor was predicted using their single component adsorption isotherms. The model was verified by experimental data obtained at a wide range of operating conditions before being used for studying the process intensification. Validation tests revealed that the model could accurately predict the experimental removal efficiencies (R2 = 0.94), as well as VOC concentration profiles inside the bed (R2 = 0.98). The intensification simulations showed that increasing the adsorbent feed rate is effective when there is a need for more adsorption sites (e.g. at high inlet concentrations), and is quite ineffective when the adsorption process is limited by low solid-gas contact time (e.g. high air flow rates). Increasing the adsorbent feed rate can also diminish the interference of water vapor in adsorption of VOC (even at RH as high as 75%). Reducing air flow rate at constant VOC load is always effective specially when there are enough adsorption sites available (e.g. high adsorbent feed rate, and low VOC loads and RHs). Similarly, increasing the number of stages can effectively improve the fluidized bed performance at high adsorbent feed rates and low VOC inlet concentrations and RHs. Using 3 adsorbers of 2 stages instead of 1 adsorber of 6 stages can improve the removal efficiency up to 34.5% in the range of operating conditions simulated. While having the same high weir height along the bed yields better performance than having the same low weir height, an optimized arrangement of weir heights in a descending order from the top to the bottom of the bed would maximize the removal efficiency.

An automated multi-component gas adsorption system (MC GAS)

The knowledge gap on adsorption of complex mixtures in the literature relative to single component data represents a persistent obstacle to developing accurate process models for adsorption separations. The collection of mixed gas adsorption data is an imminent need for improved understanding of the behavior of adsorbent systems in these diverse adsorption applications. Current approaches to understanding mixture adsorption using predictive theories based on pure component adsorption experiments often fail to capture the behavior of more complex, non-ideal systems. In this work, we present an automated volumetric instrument for the measurement of mixed gas adsorption isotherms. This instrument was validated by comparison to other in-house instruments and data available in the literature, and the binary adsorption measurements were found to be thermodynamically consistent. The automation of this instrument allows for rapid collection of high-quality mixture adsorption data.

Adsorption of ammonia nitrogen and phenol onto the lignite surface: An experimental and molecular dynamics simulation study

Ammonia nitrogen and phenol are typical inorganic and organic pollutants in the coal chemical wastewater, respectively. In this study, the adsorption characteristics of ammonia nitrogen and phenol on lignite were investigated through experimental and molecular dynamics simulations. The results show that the adsorption of ammonia nitrogen was carried out via ion exchange, which was significantly faster than the adsorption of phenol driven by the π–π interaction. In the binary adsorption, the surface electronegativity of lignite decreased with the adsorption of ammonia nitrogen thereby promoting the adsorption of phenol. However, the extent of ammonia nitrogen adsorption was slightly reduced in the presence of phenol. Molecular dynamics simulation results indicated that the adsorption of phenol molecules on the lignite surface was closer than that of ammonium ion. The addition of ammonium ions could enhance the adsorption of phenol molecules on the lignite surface. The simulation results were well consistent with the experimental findings. This study indicates lignite has a promising potential in coal chemical wastewater adsorption pretreatment.

Application of modified green algae Nannochloropsis sp. as adsorbent in the simultaneous adsorption of Methylene Blue and Cu(II) cations in solution

Biomass of algae is a very potent adsorbent for absorbing aqueous waste containing heavy metals and organic dyes. This study purposes to confirm the ability of adsorbents from green algae Nannochloropsis sp. modified with silica (ASN) and followed by coating magnetite particles (ASN-MPs) to absorb simultaneously the mixture of Methylene Blue (ME) and Cu(II) cations in aqueous solution. Simultaneous sorption of ME and Cu(II) cations to ASN and ASN-MPs was carried out by the batch method with the interaction pH condition 7, contact time 90 min, and initial concentrations of ME and Cu(II) cations (0.1–1.0 mM). Based on adsorption data, Cu(II) cations have a greater adsorption rate and capacity (qm) compared to ME at the same contact time and initial concentration. The adsorption capacity (qm) values of the bi-component ME and Cu(II) cation mixture in ASN and ASN-MPs were 1.39 × 10− 1 and 5.32 × 10− 1 mmol g− 1, respectively, with the binary Langmuir adsorption isotherm constant for Cu(II) cations greater than ME. Modified adsorbent from algae Nannochloropsis sp. with silica matrix and magnetite particle coating is an adsorbent that has a high effectiveness in the collective sorption of ME and Cu(II) cations. Therefore, these adsorbents can be used for the adsorption of cation mixtures of heavy metals and organic dyes that are cationic in solution.

Adsorption mechanisms of single and simultaneous removal of pharmaceutical compounds onto activated carbon: Isotherm and thermodynamic modeling

The simultaneous adsorption of pharmaceutical compounds is a challenge for real-life water treatment applications. Therefore, the present study aimed to investigate the simultaneous adsorption of paracetamol and nimesulide, using activated carbon (AC) as an adsorbent. Single adsorption experiments were also performed to compare the adsorption behavior changes. For instance, AC showed a higher single adsorption capacity for nimesulide (196.32 mg g−1) than paracetamol (58.21 mg g−1). Interestingly, during the binary adsorption, nimesulide molecules were adsorbed on active sites previously occupied by paracetamol molecules. This displacement phenomenon, due to the competition of pharmaceutical molecules at higher pharmaceutical concentrations, promoted the adsorption of nimesulide (199.49 mg g−1) and strongly suppressed the adsorption of paracetamol (25.80 mg g−1) on AC. The greater affinity between the AC and nimesulide was related to the more hydrophobic nature of nimesulide (log Kow = 2.60) than that of paracetamol (log Kow = 0.49). Besides, FTIR spectra, before and after adsorption, suggested that paracetamol was adsorbed only by H–bonding interactions, while nimesulide was adsorbed by H–bonding, π−π, and n−π dispersion interactions. Langmuir model (R2 ≥ 0.991) successfully adjusted the single equilibrium isotherms for both pharmaceuticals. Whereas, Extended Langmuir model (R2 ≥ 0.984) was chosen to predict the binary adsorption of paracetamol and nimesulide on AC. Finally, the thermodynamic analysis suggested exothermic, favorable, and spontaneous adsorption, with low adsorption energies that supported the physisorption.

On the use of single, dual and three process langmuir models for binary gas mixtures that exhibit unique combinations of these processes

Two scenarios were investigated for predicting binary gas adsorption equilibria when the single gas isotherms of one component is described by the three process Langmuir (TPL) model and the single gas isotherms of the other component is described by either the dual process Langmuir (DPL) or single process Langmuir (SPL) model. For the TPL–SPL and TPL–DPL models, 7 and 12 different correlations of energetic (free energy) site matching respectively exist. For these complex systems, perfect positive (PP) means the free energies of the sites of the two components align in some way from high to low, while perfect negative (PN) means they misalign in some way with high free energy sites for one component aligning with low free energy sites for the other component. Other variations of PP and PN exist where the free energies correlate in some way with the free energy of the site of one of the components distributed among two or more sites of the other component, and uncorrelated exit where the free energies do not correlate but possibly still have some site distribution. A consistent set of single and binary isotherms for CO2 and N2 on 13X zeolite were used to explore all 19 correlations. CO2 fitted well only to the TPL single gas model and N2 fitted equally well to either the DPL or SPL single gas model. Only 3 of the 12 cases for the TPL–DPL model and 2 of the 7 cases for the TPL–SPL model exhibited reasonable predictions of the experimental results; the remaining 14 cases failed. The predictions for CO2 for both models were very good for all 19 cases; but, some of the predictions for N2 were so overpredicted, they were not even close to reality. The simpler site matching correlations fared better than the more complex ones, such as those with the sites of N2 distributed over two or more sites of CO2. For this CO2–N2-13X binary system, PP site matching correlations provided the best predictions, with the high and low free energy sites of N2 decidedly interacting with the high and medium free energy sites of CO2 with the low free energy site of CO2 unoccupied by N2.

Effect of structure matching in the adsorption process: The preparation of alkylbenzene-functionalized polypropylene nonwoven using surface modification for adsorbing nonylphenol

In this study, a functionalized polypropylene (PP) nonwoven fabric (PP-GMA/(n-OA)) with alkylbenzene groups is developed via irradiation polymerization and ring-opening amination method, which is utilized for selectively removing nonylphenol (NP) from complex aqueous solution. The design and fabrication of PP-GMA/(n-OA) is based on structure matching with NP. The PP-GMA/(n-OA) is endowed with a superior selective adsorption property toward NP, with selectivity coefficients (α) as high as 56.06 from the binary adsorbate systems of nonylphenol (NP) and phenol (Ph), and the maximum adsorption capacity for NP was 3.684 mg/g. The adsorption isotherms, kinetics, and thermodynamics are then studied to understand the adsorption behavior. Notably, it was speculated that the π-π interplay, hydrophobic interplay, and hydrogen bonding would have synergistic effects in the adsorption process of NP by the PP-GMA/(n-OA) based on an analysis of the Fourier-transform infrared spectroscopy (FT-IR) spectrum and adsorption behaviors. The synergistic effect promoted the structure matching of NP molecule groups with the functional groups in the PP-GMA/(n-OA). In addition, the results of multiple adsorption regeneration experiments showed that the PP-GMA/(n-OA) was readily regenerated by washing in hot water with the lass decrease (12.8%) of adsorption capacity after five circulates. Overall, this study supplies a strategy for the design and preparation of efficient adsorbents for trace organic compound removal in aqueous solutions.

Effect of coexisting ions on adsorptive removal of arsenate by Mg-Fe-(CO3) LDH: multi-component adsorption and ANN-based multivariate modeling

The adsorptive removal of a pollutant from water is significantly affected by the presence of coexisting ions with various concentrations. Here, we have studied adsorption of arsenate [As(V)] by calcined Mg–Fe–(CO3)–LDH in the presence of different cations (Mg2+, Na+, K+, Ca2+, and Fe3+) and anions (CO3 2‒, Cl‒, PO4 3‒, SO4 2‒, and NO3 ‒) with their different concentrations to simulate the field condition. The experimental results indicated that Ca2+, Mg2+ , and Fe3+ have a synergistic effect on removal efficiency of As(V), whereas PO4 3‒ and CO3 2‒ ions have a significant antagonistic impact. Overall, the order of inhibiting effect of coexisting anions on adsorption of As(V) was arrived as NO3 –˂Cl–<SO4 2–<CO3 2 –<PO4 3 –. Among them, competitive adsorption of phosphate with arsenic at different initial phosphate concentrations was found to be responsive to formulate a binary adsorption system. We have also developed a modified non-competitive Langmuir and Langmuir–Freundlich models; however, the modified competitive Langmuir model was arrived to be the most adequate model for this binary system. An Artificial Neural Network based multivariate prediction model was developed, delineating the impact of coexisting ions on the adsorption system. The proposed method may appropriately demonstrate the overall system and exhibited a significantly adequate prediction model with high R2, high F-value, and low error values.

Adsorption of organic compounds from aqueous solution by pyridine-2-carboxaldehyde grafted MIL-101(Cr)-NH2 metal-organic frameworks

Metal-organic frameworks (MOFs) are of particular interest in the adsorption of organic pollutants. This study investigated the adsorption of aniline (ANI), furfural (FUR), and bisphenol A (BPA) in aqueous solution using MIL-101(Cr)-X (X = –H, –NO2, –NH2 and, –N-2-pyc), MIL-100(Cr, Fe), HKUST-1, and ZIF-8. For the first time, an imino-functionalized MOF was used to adsorb organic compounds in water. MOFs were characterized by XRD, N2 adsorption-desorption, SEM, TEM, elemental analysis, and FTIR. MIL-101-N-2-pyc demonstrated the highest adsorption capacity of 460.8, 126.5, and 100.7 mg/g towards 500 mg/L BPA, ANI, and FUR respectively. The adsorption isotherms better suited the Langmuir model than the Freundlich model. Importantly, 98% of BPA (100 mg/L) was removed and the kinetic data correlated well with the pseudo-second-order model (R2 > 0.998). Binary adsorption of FUR and acetic acid (AA) were determined for industrial relevance. MIL-101-N-2-pyc outperformed commercial activated carbon and the other MIL-101s with an impressive co-adsorption of 66.1 mg/g FUR and 62.5 mg/g AA. Overall, the adsorption mechanism was due to hydrogen bonding, π-π interaction, and electrostatic attraction. Moreover, MIL-101-N-2-pyc exhibited remarkable structural stability and less than 0.01 wt% Cr leached into water. The adsorbent regeneration was improved after 4 cycles in methanol.

Arsenic Adsorption on Modified Clay Minerals in Contaminated Soil and Water: Impact of pH and Competitive Anions

AbstractThis study evaluates the arsenic adsorption behavior of Fe‐exchanged smectite and phosphate‐bound kaolinite, in soil, tap water and double distilled water in the presence of competing anions such as silicate, phosphate, and sulfate, and at variable pH values. The maximum amounts of As adsorbed in soil are 620.6 and 607.6 µg g–1 at pH 5 by Fe‐exchanged smectite and phosphate‐bound kaolinite, respectively. The pH‐modified Freundlich equation fits well (R2 &gt; 0.96) to the adsorption data, distinguishing the effect of pH on adsorption. The coefficients of pH‐value are 0.04 and 0.05 for phosphate‐bound kaolinite and Fe‐exchanged smectite, suggesting that low pH is suitable for the adsorption. The As adsorption is decreased in tap water at low pH compared to the soil due to the presence of iron (Fe2+/3+), sulfate, and bicarbonate in tap water. Among the competing anions in distilled water, phosphate is the most interfering anion for As adsorption. The competition coefficients of As‐phosphate binary adsorption derived from the Sheindorf equation are 3.93 and 0.56 for Fe‐exchanged smectite and phosphate‐bound kaolinite at pH 5. The Fe‐exchanged smectite can be used more effectively than phosphate‐bound kaolinite for As remediation in systems having low pH (pH ≈5) and high phosphate concentration.

Application of pyridine-modified chitosan derivative for simultaneous adsorption of Cu(II) and oxyanions of Cr(VI) from aqueous solution

The bioadsorbent C1, which is a chitosan derivative prepared in a one-step synthesis, was successfully used to adsorb Cr(VI) and Cu(II) simultaneously. Here, for the first time the simultaneous adsorption of a cation and an anion was modeled using the Corsel model for kinetics and the Real Adsorbed Solution Theory model for equilibrium data. Batch studies of the adsorption of Cu(II) and Cr(VI) in single and binary aqueous solutions were performed as a function of initial solute concentration, contact time, and solution pH. The maximum adsorption capacities of C1 in single and binary aqueous solutions were 1.84 and 1.13 mmol g−1 for Cu(II) and 3.86 and 0.98 mmol g−1 for Cr(VI), respectively. The reuse of C1 was investigated, with Cu(II) ions being almost completely desorbed and fully re-adsorbed. For Cr(VI), the desorption was incomplete resulting in a lower re-adsorption. Energy-dispersive X-ray spectroscopy was used for mapping the distributions of Cr(VI) and Cu(II) adsorbed on the C1 surface in single and binary adsorption systems. Isothermal titration calorimetry experiments were performed for Cr(VI) and Cu(II) adsorption in single solutions. The thermodynamic parameters of adsorption showed that the adsorption of both metal ions was enthalpically driven, but entropically unfavorable.

A Thermodynamic Model for Pure and Binary Adsorption Equilibria of N2 and O2 on Lithium-Exchanged Low Silicon-to-Aluminum Ratio X Zeolite

To accurately describe the adsorption equilibria of N2 and O2 on LiLSX zeolite in the design of air separation by pressure swing adsorption, an applicable model (aNRTL–RAST) was developed. It was based on the real adsorbed solution theory (RAST) in which the activity coefficient was calculated by the nonrandom two-liquid theory (aNRTL). The binary adsorbate–adsorbate interaction parameters of the aNRTL theory were estimated from the pure component isotherms. The aNRTL–RAST model was used to predict the mixed gas equilibrium data under different adsorption conditions and compared with the extended Langmuir (E-L), two-dimensional equation of state (2D-EOS), and ideal adsorbed solution (IAST) models. aNRTL–RAST showed better accuracy than the other models, and the average errors for different adsorption conditions were <5%. Therefore, this model can be used to predict the adsorption equilibrium of mixed gases, avoiding complicated and tedious experiments. This study provides a theoretical basis for the selection of oxygen adsorbents for the separation process design of industrial air separation.

Bioadsorption of nickel and cadmium ions from a binary solution onto sugarcane bagasse lignin: kinetic and thermodynamic study

The single and binary adsorption of Cd(II) and Ni(II) from aqueous solution on lignin of sugarcane bagasse, a secondary product of sugarcane industry, has been demonstrated in this work. Experimental parameters affecting the adsorption are studied, such as the lignin dose, pH, contact time and temperature. The optimal values found for these parameters, both binary and single adsorption, are the followings: lignin dose (7g / L), pH (6), contact time (12 hours) and temperature (40°C). Different empirical adsorption models are used for the evaluation of sorption equilibrium data. Experimental results were interpreted considering speciation curves of ions present in the solution. In single and binary system adsorption data are analyzed using the following adsorption isotherms: single, non-modified, extended and modified Langmuir; single, non-modified and modified Redlich–Peterson; single and extended Freundlich; single and multicomponent Langmuir-Freundlich; and Sheindorf–Rebuhn–Sheintuch. The experimental adsorption isotherms are better adjusted to the extended Langmuir model. This study indicates that the lignin is an adsorbent able to remove Ni (II) and Cd (II) in binary systems, having a greater affinity for cadmium.

Energy-Saving and Sustainable Separation of Bioalcohols by Adsorption on Bone Char

The separation of ethanol, propanol, and butanol from aqueous solutions was studied using adsorption on bone char. Adsorption kinetics and thermodynamic parameters of this separation method were studied at different conditions of pH and temperature. Results showed that the maximum adsorption capacities of these bioalcohols were obtained at pH 6 and 20°C. An exothermic separation was identified, which can be mainly associated to hydrophobic interactions between bone char surface and bioalcohols. Binary adsorption studies were also performed using mixtures of these bioalcohols. An antagonistic adsorption was observed for all bioalcohols where the ethanol and propanol separation was significantly affected by butanol. A model based on an artificial neural network was proposed to correlate both single and binary adsorption isotherms of these bioalcohols with bone char. It was concluded that the bone char could be an interesting adsorbent for the sustainable separation and recovery of bioalcohols from fermentation broths, which are actually considered emerging liquid biofuels and relevant industrial chemicals.

Binary Adsorption Studies of Toxic Metal Ions of Lead and Copper from Aqueous Solution by Modified Foeniculum vulgaris Seeds (Fennel Seeds)

Discharge of copper(II) and lead(II) ions into rivers and streams by industries and other human activities has gained serious consideration from regulatory bodies. These toxic metals are harmful to human beings and aquatic life when in high concentrations. Therefore, their removal from wastewater is very important. Hence, this work reports the binary adsorption of toxic metal ions of Cu(II) and Pb(II) from aqueous solution by pristine and modified fennel seeds. Pristine fennel seeds (PFS) were treated with acidic and alkaline solutions to develop modified adsorbents designated ATFS and BTFS, respectively. SEM images revealed that PFS had an amorphous surface with irregular cavities. However, upon acid and base treatment, the surface was more refined. The ATFS had interconnected pores while BTFS had somewhat honeycomb pores. The UV-Vis results confirmed that some of the components were removed from PFS during acid and base pre-treatment. FTIR spectra revealed that the adsorbents had functional groups such as (-OH) and (-C=O), which were involved in the uptake of the metal ions. It was observed that the uptake of Cu(II) and Pb(II) ions onto all adsorbents progressively increased when the initial concentration of the solution was increased. The maximum adsorption capacity was obtained when the initial concentration of the solution was 100 mg/L. The uptake of Cu(II) and Pb(II) on PFS was 3.345 and 11.524 mg/g. While for ATFS 3.78 and 13.07 mg/g and BTFS 8.143 and 14.85 mg/g, respectively. It was observed that the isotherm data fitted Freundlich better for the uptake of both metal ions onto all adsorbents. It was observed that there was a rapid uptake when contact time increased from 5 to 60 min. However, when time increased above 60 min the uptake stabilized and reached equilibrium this was due to the saturation of active sites on the surface for all adsorbents. The kinetics study revealed that PSO fitted the data better than PFO. IPD data revealed that the uptake of metal ions was controlled by the synergistic of ESA and EPA. The ΔHº values for Cu(II) and Pb(II) uptake onto all adsorbents were all negative. This suggested that the reactions were exothermic.

Kinetics on propionic acid catalytic esterification with N-butanol over SBA-15 (santa barbara amorphous-15 material) catalyst

A batch reactor was used to investigate kinetic behaviour of propionic acid withN-butanol over acidic ion-exchange resign SBA-15. The kinetic studies were performed for temperatures ranges 358oK to 388oK then feed varies 1–5 the molar proportions of propionic acid to N-butanol. The response rate was discovered to rise with rising temperature. However, propionic acid equilibrium conversions slightly change the entire reaction temperature suggesting this reaction's impact is negligible. It’s been discovered that propionic acid conversion improves with feed molar ratios rising from 1 to 5. Based on the outcomes of binary adsorption studies, relative sorption between two interacting species is determined. Water > n-butyl propionate > propionic acid > n-butanol follows the severity of adsorption strengths. The kinetic information was associated Langmuir Hinshelwood Haugan Watson modelsto assess kinetic variables for each model, respectively. The LHHW has produced the highest outcomes among these researched models.

Single and Binary Adsorption Systems of Rhodamine B and Methylene Blue onto Alkali-Activated Vietnamese Diatomite

Diatomite was slightly modified with a sodium hydroxide solution. The resulting material was characterized by using energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and nitrogen adsorption-desorption isotherms. The so-treated diatomite has a high specific surface area (77.8 m2/g) and a high concentration of isolated silanol groups on the surface, and therefore, its adsorption capacity increases drastically in both the single and binary adsorption systems for rhodamine B and methylene blue. The binary system is more effective than the single system, with methylene blue being adsorbed more than rhodamine B. The adsorption process is spontaneous and fits well with the Langmuir isothermal model, and it depends on pH significantly.

Dynamic modelling of Alginate - Cobalt ferrite nanocomposite for removal of binary dyes from textile effluent

The performance of Alginate - Cobalt ferrite (ACF) in a fixed bed column was assessed for the simultaneous removal of binary dyes from textile effluent. The binary dye effluent containing 32.5 mg/L of reactive red 195 (RR195) and 21 mg/L of reactive yellow 145 (RY145) was used for the study. The effect of various parameters like bed depth (3, 6, 9 and 12 cm) and flow rate of influent (5, 7.5 and 10 mL/min) for the binary adsorption using ACF was studied. The results revealed that ACF bed capacity and maximum adsorption capacity showed an increasing trend with an increased bed depth and decreased flow rate. Dynamic modeling such as Yoon - Nelson model, Thomas model and Bed Depth Service Time model (BDST) were evaluated with the experimental data. Comparatively, Yoon - Nelson and Thomas model presented better fitness for the elimination of RR195 and RY145 dye. The experimental data from dynamic studies revealed ACF's effectiveness for the sequestration of binary dyes from textile effluent.

Adsorption of furan, hexanoic acid, and alkanes in a hierarchical zeolite at reaction conditions: Insights from molecular simulations

Hierarchical zeolites containing both micropores and mesopores are valuable catalysts for facilitating reactions of large molecules. Furan acylation by fatty acids is a promising reaction for valorizing biomass, and the self-pillared pentasil (SPP) zeolite was found to perform particularly well for this reaction. To better understand the distribution of molecules in hierarchical zeolites at the elevated temperature (T=523 K) and the elevated pressure (p>1 bar) associated with typical reaction conditions, unary and binary adsorption were predicted using Monte Carlo simulations in the isothermal–isobaric Gibbs ensemble. Adsorption of six species (furan, hexanoic acid, n-hexane, n-decane, n-tetradecane, and 3,6-diethyloctane) was investigated from vapor, liquid, and supercritical phases, and loadings into the micropores, onto the mesopore surface, and in the mesopore interior of SPP were obtained. As pressure increases, n-alkanes fill the micropores before loading the surface and then the interior of the mesopore, while furan and hexanoic acid adsorb strongly to the mesopore surface due to hydrogen bonding interactions with surface silanols. Hydrogen bonding interactions also draw hexanoic acid molecules in the micropore region toward the pore mouths, so their carboxylic acid group forms H-bonds with silanols, while the alkyl tails interact with the micropore walls. Mesopore condensation is observed for molecules below their critical point, and occurs when the Gibbs free energy of transfer into the mesopore interior and onto the mesopore surface converge. When hexanoic acid adsorption occurs in the presence of alkane solvents, then the selectivity and spatial distribution of hexanoic acid in the micropores and on the surface can be tuned by adjusting the fluid pressure and the alkane length and/or branching.

Influence of Salinity on the Removal of Ni and Zn by Phosphate-Intercalated Nano Montmorillonite (PINM)

The salinity influence on the adsorptions of Ni and Zn onto phosphate-intercalated nano montmorillonite (PINM) were investigated. Single adsorption isotherm models fitted the single adsorption data well. The adsorption capacity of Ni was higher than that of Zn onto PINM at different salinities. The single adsorption parameters from Langmuir model (QmL and bL) were compared with the binary adsorption (QmL* and bL*). The QmL* of Zn was lower than that of Ni. The simultaneous presence of Ni and Zn decreased the adsorption capacities. The single and binary adsorptions onto PINM were affected by the salinity. The competitive Langmuir model (CLM), P-factor, Murali and Aylmore (M−A) models, and ideal adsorbed solution theory (IAST) were satisfactory in predicting the binary adsorption data; the CLM showed the best fitting results. Our results showed that the PINM can be used as an active Ni and Zn adsorbent for a permeable reactive barrier (PRB) in the remediation of saline groundwater.