Total Adsorption Research Articles

Combined effects of the chemical structure and nanopore development on water vapor/liquid adsorption in shale kerogen

The interaction between water/gas and rock plays an important role in evaluating initial fluid storage in shale gas reservoirs. It is challenging to understand the co-occurrence relationships of water, chemical structure, and nanopore in shale kerogen due to the fact that both pore-forming material and water adsorption are related to the chemical structure. In this study, we did water vapor adsorption (WVA) experiments on seven Longmaxi Formation shale kerogen, and then analyzed the vapor-liquid equilibrium process. Results show that water is preferentially adsorbed in micropores (< 2 nm) through monolayer coverage when the relative humidity (RH) is less than 75%, while mesopores (2–50 nm) contribute dominantly to the total water adsorption when the RH is greater than 75%. Furthermore, based on grand canonical Monte Carlo simulations, we constructed water-contained molecular models with the same adsorption amounts as the WVA experiments to simulate the water adsorption process. Simulation results show that water can exist in hydrophilic oxygen-containing structures in the form of monolayer coverage, and in hydrophobic carbon structures in the form of water clusters. Under low RH, the narrow ultra-micropores (mainly < 0.35 nm) within the hydrophilic oxygen-containing structures are the primary adsorption centers for water adsorption, which results in a monolayer coverage of water molecules. With increasing RH, the hydrophobic carbon structures can adsorb water molecules because the residual oxygen-containing structures bonded to aliphatic/aromatic carbons provide connecting sites for the formation and growth of water clusters. Based on the acquired results, a molecular model showing the co-occurrence relationships among water, chemical structure, and nanopore was constructed, which helps to understand the microscopic mechanism of fluids-rock interactions.

Impact of simulating real microplastics on toluene removal from contaminated soil using thermally enhanced air injection

This paper investigated the impacts of various real microplastics (MPs), i.e., polyethylene (PE) and polyethylene terephthalate (PET) with different sizes (1000–2000 and 100–200 μm) and different dosages (0.5 and 5% on a dry weight basis), on the toluene removal during the thermally enhanced air injection treatment. First, microscopic tests were carried out to determine the MPs' microstructure and behavior. The PE was mainly a small block, and PET appeared filamentous and sheeted with a larger slenderness ratio. Second, the interactions between MPs and toluene-contaminated soils were revealed by batch adsorption equilibrium experiments and low-field magnetic resonance. The morphological differences and dosage of the MPs impacted soils’ total porosity (variation range: 39.2–42.7%) and proportion of the main pores (2–200 μm). Third, the toluene removal during the air injection consisted of compaction, rapid growth, rapid reduction, and tailing stages, and the MPs were regarded as an emerging solid state to affect these removal stages. The final cumulative toluene concentrations of soil-PET mixtures were influenced by total porosity, and those of soil-PE mixtures were controlled by total porosity (influence weight: 0.67) and adsorption capacity (influence weight: 0.33); meanwhile, a self-built comprehensive coefficient of MPs can reflect the relationship between them and cumulative concentrations (correlation coefficient: 0.783).

Rapid and highly selective capture of U(VI) from water by copper phosphate

The removal of highly hazardous U(VI)-containing contaminants of concern has been a major issue for effluent discharge and ecological protection because current some inorganic adsorbents lack ion selectivity and are economically viable. Inspired by these limitations, here we reported a simple and controlled technique for the synthesis of copper phosphate (CP) that combines chemical oxidation with in-situ precipitation, able to selectively capture uranium (VI) ions. The resulting CP has been analyzed using powder X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analysis, transmission electron microscopy, infrared spectroscopy, and X-ray photoelectron spectroscopy. Adsorption experiments with U(VI) show that CP quickly adsorbs U(VI) from acidic water within 1 min, with a high removal efficiency of up to 97.8%. A maximum adsorption capacity of 1000 mgU g−1 adsorbent can be achieved at pH 3.0. Importantly, the selective adsorption experiments for a total of 11 metal ions show that the U(VI) capture is very effective, with an adsorption capacity of 1.64 mmol g−1 for U(VI) and a total adsorption capacity of 4.89 mmol g−1 for Ln-An metal ions. Finally, XRD and XPS results reveal that the underlying mechanism for U(VI) capture is driven through the dissolution-precipitation and surface complexation. Overall, this work proposes a new metal ion trapping agent that may find potential applications in the fields of water purification and environmental remediation.

Adsorption of ionic liquids forming species on Ti3C2Tx MXenes surfaces by first-principle calculations

MXenes are two-dimensional layered materials that have attracted increased attention for technological applications, e.g., electrodes, support for single atom catalysts, etc. Several experimental and computational studies have been reported, however, our atomistic understanding is still far from good, in particular, for MXene-ionic liquid interfaces, which is crucial to predict and control the charge–discharge rate of those systems. Here, we have assessed the adsorption of ionic liquids forming species, on surfaces of Ti3C2Tx (where T = F, O or OH) MXenes by means of ab initio calculations at density functional theory level. The F and O terminated MXenes showed to be stables upon the adsorption, whereas the OH terminated one suffered important structural deformations when interacting with cationic species. The adsorption of molecular species are stronger, with values ranging in between −1.10 and −7.36 eV, indicating the contribution of Coulombic and induction interactions as a result of the charge transference among MXenes and adsorbates. The adsorption of ionic pairs on the Ti3C2F2 and Ti3C2O2 monolayers were driven by dispersion interactions, that represent at least 84% of the total adsorption energy. Additionally, the work function of the stable MXenes structures were barely affected by the adsorption of the ionic pairs, and hence, the adsorption process did not affect the electronic properties of the single Ti3C2Tx monolayers.

Adsorption of Hydrophobic Ions on Environmentally Relevant Sorbents.

Environmental monitoring and remediation often requires the collection of harmful substances from aqueous solutions. Absorption with solids is a useful technique for binding such substances even at very low concentration levels. Many of these contaminants are weak acids or bases. Some novel, nonionic polymeric sorbents, such as hypercrosslinked polymers or polymers with balanced hydrophilic-lipophilic properties (HLB) have been found to bind weak acids and bases with high distribution coefficients even at pH values where these compounds are almost completely ionized (typically near pH 7). To understand this phenomenon and its practical consequences, we have experimentally studied the adsorption of ionizable weak acids and bases as a function of pH and ionic strength on a the OASIS® HLB sorbent. Not surprisingly, the ionic forms of the weak acids and bases were found to be much less bound in the aqueous solution than their neutral forms. In spite of this, OASIS® HLB binds weak acids and bases around pH 7 considerably better than typical hydrophobic sorbents. The high overall distribution coefficients around pH 7 could be explained by two factors. One is that on OASIS® HLB, and on some other novel polymeric sorbents, the binding constant of the moderately hydrophobic neutral form is on the order of 100,000, i.e., much higher than on typical hydrophobic sorbents. Thus, even if the proportion of the neutral form in solution is only around 1% near pH 7, the adsorption of the neutral form is still significant. On the other hand, the binding of the apparently hydrophilic ionized forms occurs with distribution coefficients well above 100. The distribution coefficient of the ionic form appears to depend on ionic strength and the presence of competing ions. Adsorption of the ionic forms is found to be very similar to the adsorption of ionic surfactants. The pH dependence of the total adsorption of neutral and ionic forms together, is found to be steep around pH 7, and therefore the varying pH of natural waters may strongly influence the binding efficiency in practical applications, such as the collection (concentration) of contaminants or their passive sampling.

Adsorption isotherms of Polyquaternium-10 polymers by activated sludge solids

Polymeric quaternary ammonium salts (polyquaternium-10 polymers, PQ-10) are extensively used as components of hair care products, lotions, and makeup and, therefore, are present in domestic sewage. Adsorption of these polymers by activated sludge was assessed to evaluate their removal by a commonly used wastewater treatment process. Activated sludge solids (ASS) were dosed with PQ-10 polymers with relatively high molecular mass (JR-125 and JR-30 M) and relatively low molecular mass (LR-400 and LR-30 M) and equilibrated for 2 h at 20 ± 2 °C. After equilibration, the vessels with the mixtures were centrifuged and the supernatants were analyzed with a phenol method.The relationships between dosed amounts and equilibrium concentrations in the aqueous phase (dose-response curves) for each tested polymer indicated that at relatively low dosing solution concentrations were negligible (“total adsorption” region of the dose-response curve). Light absorbance of the samples prepared for determination of polymer concentration using a phenol method within this region was close to the absorbance of the blank (0 μg (a.i.)/mL) or below absorbance of the blank, resulting in calculated concentrations apparently below zero. At some level of dosing, a subsequent increase in polymer dosage resulted in a quantifiable increase in solution concentration (“solution concentration rising” region).The relationships between concentrations of the polymers in the aqueous phase and concentrations of adsorbed polymers (adsorption isotherms) were non-linear. The ability of activated sludge solids to bind tested polymers may be characterized by apparent “threshold values” of the loading for each polymer. Below the “threshold value,” solution concentration of the polymer is close to zero and above this value it becomes measurable. “Threshold loading” for all polymers was from 50 to 100 mg (a.i.)/g, far above concentrations of these compounds expected to be present in the sewage.

Designing degradable lignin-grafted magnetic nano-composite materials for cost-effectively sustainable removal of fluoroquinolone antibiotics from environmental water

Developing a novel green adsorbent to meet the requirements of low-cost, high quality of enrichment for analytes, and environmental sustainability is significant but remains a challenge. Herein, an eco-friendly dealkaline lignin-grafted magnetic iron oxide nanoparticle (Fe 3 O 4 @DAL) used as a dispersion solid adsorbent for the removal of fluoroquinolone antibiotics (FQs) from environmental water was developed based on the amide reactions between cost-effective plant-derived dealkaline lignin (DAL) and amino-functionalized Fe 3 O 4 nanoparticles at room temperature. Fe 3 O 4 @DAL combined with the advantages of lignin and magnetic nanoparticles , which had abundant functional groups (phenols and aliphatic hydroxyl, carboxyl, phenyl) and high separation efficiency, so typical FQs including pefloxacin (PEF), lomefloxacin (LOM), enrofloxacin (ENR) and difluoxacin (DIF) could be easily removed by multiple interactions. The Langmuir isotherm model and pseudo-second-order model could be more suitable to describe the adsorption process of FQs on Fe 3 O 4 @DAL. The maximum adsorption capacities of Fe 3 O 4 @DAL for PEF, LOM, ENR, DIF were 25.2 mg g −1 , 19.2 mg g −1 , 30.0 mg g −1 , 33.7 mg g −1 , respectively. And the total maximum adsorption capacities of four FQs could reach 108.2 mg g −1 . The whole adsorption process was spontaneous and endothermic based on thermodynamic data . Moreover, Fe 3 O 4 @DAL was of great reusability and could be used at least 5 cycles. In particular, the recycled adsorbent can be degraded as slow-release fertilizer under the action of soil microorganisms , which helps the growth of plants and further expands application range of lignin. As an effective, environmental-friendly, low-cost adsorbent for alleviating FQs contamination not only increased the added value of natural raw materials, but also had a great potential in the field of water treatment . • The environment-friendly dealkaline lignin-grafted Fe 3 O 4 nanoparticles (Fe 3 O 4 @DAL) were first prepared. • Multiple interactions resulting in highly efficient removal of FQs. • Superior adsorption and reusability performance of Fe 3 O 4 @DAL were confirmed. • The recovered Fe 3 O 4 @DAL could be degraded as fertilizer to help the growth of crops. • Fe 3 O 4 @DAL increased added the value of natural raw materials.

The two-species phosphate adsorption kinetics on goethite

Studying the adsorption-desorption kinetics of ions and molecules is crucial to understand the mobility of nutrients and pollutants in the environment. This article reports the adsorption-desorption kinetics of phosphate on goethite, as measured by ATR-FTIR spectroscopy at pH 4.5, 7.0 and 9.5. The system phosphate-goethite has become a model system to test new experimental setups and theories to understand the behavior of pollutants with phosphonic or phosphinic moieties such as glyphosate or glufosinate. One of the main difficulties in the analysis of ATR-FTIR spectra in adsorption-desorption kinetics is to calibrate the equipment to convert absorbance vs. t curves into adsorption vs. t curves, and thus the methodology to achieve a good calibration using spectroscopic data in combination with adsorption isotherms is clearly described. The time evolution of the different surface species was monitored simultaneously during adsorption and desorption at different pH, showing the advantages of this spectroscopy over traditional adsorption methods that only quantify total adsorption. Results were analysed in terms of a simple adsorption-desorption model that takes into account transport, attachment, detachment and surface transformation of the adsorbed species. The same rate parameters at a given pH could predict well the adsorption-desorption kinetics of the two formed surface species and the corresponding adsorption isotherm, giving new insights into the dynamics of phosphate on the surface of goethite. It was found that phosphate desorbed faster from goethite at low pH than at high pH, which is counterintuitive, but has good practical and environmental applications.

Adsorbents selection for the enrichment of low-grade methane coal mine emissions by temperature and pressure swing adsorption technologies

This work evaluates the feasibility of common adsorbents (carbonaceous materials, zeolites and metal-organic frameworks) for the adsorption and further methane upgrading of the ventilation air methane (VAM) emissions from underground coal mining (0.57% CH4). Concentration was achieved by adsorption through two different operational procedures based on fixed bed configurations: temperature swing adsorption (TSA) and pressure swing adsorption (PSA). All the combinations have been simulated using a rigorous mathematical model implemented in a commercial simulation package. The main purpose is to evaluate the performance of the different combinations of adsorption technique and adsorbent material, as well as establishing a valid mathematical model able to test a wide range of materials. The comparison has been fulfilled with an economic evaluation of the different combinations. Results show that carbonaceous materials provide the highest concentration factors (C/C0 = 5), with low total methane recoveries (30%) and the lowest cost per kmol of methane recovered (1.5 €/kmol). MOFs can retain substantial amounts of methane, but with lower CH4/N2 selectivities than carbonaceous materials and lower methane concentration factors (C/C0 = 2.6). For this type of materials, a high recovery of methane is achieved, but at expense of the highest costs (80 €/kmol). Finally, zeolitic materials present the lowest methane concentration factor (C/C0 = 2), with intermediate both methane recoveries (58%) and costs (25 €/kmol). Concerning the adsorption technique, TSA has shown higher final methane concentrations for carbonaceous materials and some MOFs, whereas PSA overperforms for zeolitic materials. In addition, TSA is cheaper in all cases than PSA processes. On the other hand, PSA allows higher total methane recoveries and adsorption capacities for all materials, highlighting the high dependence on adsorption pressure, especially in carbonaceous materials (PSA/TSA = 18.3, in the case of Maxsorb).

Occurrence Regularity of Methane Gas Molecules in Composite Nanopores: A Molecular Simulation Study

Abstract To understand the occurrence regularity of methane gas molecules in composite nanopores, the effects of temperature, pressure, size of nanopore, and burial depth on the occurrence state of methane were studied theoretically by using the grand canonical Monte Carlo and molecular dynamic simulation methods. By comparing the results available in the literature, the reasons for the difference in the occurrence states of methane molecules in nanopores were analyzed, and a reasonable occurrence regularity of methane was proposed, which provides corresponding suggestions for the actual exploitation of shale gas. The results indicated that the methane gas molecules existed in nanopore only in the adsorption and transition states under different environmental conditions. They were preferentially adsorbed at the strong adsorption sites on the nanopore surface to form a stable adsorption layer. After the adsorption layer reached saturation, a transition layer with higher density than that of bulk methane was formed at the nanopore center. The total adsorption capacity of methane decreased gradually with an increase in the internal temperature of shale reservoirs and increased with an increase in nanopore size. In addition, the average amount of methane stored in the nanopore increased at a deeper burial depth. The occurrence state of methane under different pressure ranges was controlled under different action mechanisms. Under low pressure (P&amp;lt;20 MPa), the adsorption of methane molecules was controlled by the number of strong adsorption sites on the nanopore surface, where the density peak intensity of the adsorption layer increased with the pressure. However, under high pressure (P&amp;gt;20 MPa), the adsorption was controlled by the diffusion process of methane molecules in the organic matter layer, where both the adsorption and transition layers reached the saturation state, and excessive methane molecules diffused deeper into the kerogen layer. The approach to effectively improve the recovery efficiency was to inject water or carbon dioxide into the shale reservoir where the water or carbon dioxide molecules occupy strong adsorption positions than the methane molecules adsorbed originally under the competitive adsorption effect, and the adsorbed methane molecules were transformed to a free state.

Low-Temperature Flotation Separation of Diaspore from Kaolinite by Using a Mixed Collector

In this paper, the effect of a new mixed collector sodium oleate (NaOl)/tert dodecyl mercaptan (TDM) on the separation of diaspore and kaolinite at 283 K was investigated. The molar ratio of NaOl to TDM is 8:2. The properties of the mixed collector and its adsorption mechanism on diaspore and kaolinite were studied by surface tension measurements, Zeta potential determinations and XPS analysis. The flotation results show that the mixed collector NaOl/TDM has a good collection ability for diaspore and a good selectivity for kaolinite at low temperatures. Therefore, the mixed collector NaOl/TDM can effectively separate diaspore and kaolinite under alkaline conditions at 283 K. The results of surface tension measurements show that the molecular density, hydrophobic association ability and collection ability of the mixed collector NaOl/TDM are better than those of the single collector at 283 K. In addition, the formation of a micelle effect of the mixed collector NaOl/TDM has a synergistic effect, which improves the reagent activity at low temperatures with the flotation effect enhanced. The results of the Zeta potential determinations and XPS analysis show that the total adsorption capacity of the mixed collector NaOl/TDM on the surface of the diaspore at low temperatures is higher than that of NaOl, and the adsorption capacity on the surface of kaolinite is similar to that of NaOl. The mixed collector NaOl/TDM may be adsorbed on the surface of diaspore and kaolinite by a hydrogen bond at 283 K.

Study of the reversible/irreversible character of the deactivation of CuO/SBA–15 SOx adsorbents in wet conditions under SO2 adsorption/regeneration cycling experiments

The effect of water vapor on the DeSOx performance of regenerable CuO/SBA-15 adsorbent was investigated for different temperatures of adsorption/regeneration cycles and CuO loadings. At 400 °C a significant decrease of both dynamic and total SO2 adsorption capacity compared to the ones measured without water was observed. This decrease could be related to a faster migration and aggregation of the CuO active phase, an adsorption competition between water and SO2 molecules on the active sites and/or the formation of copper based sulfate/oxysulfate/hydroxy-oxysulfate species difficult to decompose during the reductive regeneration step. On the other hand, at 450 °C water vapor leads to an increase of the total SO2 adsorption capacity by more than 20%, which might be due to an acceleration of the oxidation of SO2, a faster chemisorption of the sulfur species on the active sites and a more efficient regeneration step with regard to 400 °C. The decrease of the CuO loading from 15 to 7 wt% leads to a lower deactivation (i.e loss of SO2 adsorption capacity) at the breakthrough of the adsorbent under wet conditions. Whatever the temperature and the CuO loading, once the water vapor is removed from the gas stream, the dynamic SO2 adsorption capacities are totally or partially recovered. This behavior shows that the deactivation of the CuO/SBA–15 adsorbent induced by water vapor is a reversible or partially reversible phenomenon. It appears that during the DeSOx process a migration towards the pore mouth and an aggregation of the CuO active phase occur faster under water vapor conditions with the formation of large particles of CuO.

Cr-Based MOF for Efficient Adsorption of Au at Low Concentrations.

The efficient enrichment and selection of Au are crucial for gold recovery. The adsorption technology is considered to have potential due to the advantages of operation simplicity and green processability. Nevertheless, the poor Au selectivity at low concentrations in complex solutions limits the further application of the adsorption technology. In this work, a novel Cr-based MOF adsorbent was successfully synthesized using 1,2,4-triazole and 4-aminobenzoic acid as ligands. Benefitting from the surface positive charge and extensive chelation and reduction sites, the novel Cr-based MOF exhibited a total adsorption capacity of up to 357 mg/g and excellent adsorption selectivity toward Au(III) in the complex metal mixed solutions, such as simulated sewage ash waste liquid and actual e-waste leachate. Furthermore, the adsorption kinetics, isotherms, and thermodynamics were discussed in depth for investigating the adsorption mechanisms of the MOF. The PXRD and XPS analyses reveal that the adsorption process involves complexation, redox, and electrostatic interactions. We believe that this study of novel Cr-based MOF adsorbents for efficient Au adsorption is meaningful for further application in the gold recovery technology from e-waste.

High-performance total sulfur removal from diesel fuel using amine functionalized biochar: Equilibrium, kinetic study and experimental design

The presence of sulfur components in diesel fuel can produce SOx gases, which emit from the combustion of diesel fuel and cause serious environmental problems. In this study, four various adsorbents biochar/CuFe2O4 (BC/CuFe2O4), oxidized biochar/CuFe2O4 (O-BC/CuFe2O4), ethylene diamine-functionalized biochar/CuFe2O4 (Et-BC/CuFe2O4) and melamine-functionalized biochar/CuFe2O4 (Me-BC/CuFe2O4) were prepared for application in the total sulfur (all sulfur compounds) adsorption from diesel fuel. The prepared samples were characterized by XRD, TGA, VSM, FT-IR, FE-SEM, TEM and Raman techniques. Also, the Response Surface Methodology-Box-Behnken design was used in order to optimize adsorption key parameters included contact time, amount of adsorbent and percentage of Cu. Because of the presence of CuFe2O4 nanoparticles, all of the prepared adsorbents can be regenerated and reused for consecutive adsorption tests. The π-complexation can be formed between Cu in adsorbents and aromatic sulfur compounds. Also Cu+2 can be a proper cation for adsorption of mercaptan components from diesel fuel. Formation of oxygenated group in O-BC sample and presence of –NH2 functions in Et-BC and Me-BC samples can form hydrogen bonding with sulfur atom in sulfur compounds and create a very high adsorption capacity. Kinetic as well as isotherm studies showed that total sulfur adsorption by the prepared adsorbents followed second order and Langmuir adsorption model. For the sample of Me-BC/CuFe2O4, the adsorption capacity was obtained 1666.7 mg/g, while this value was 192.3 mg/g in the presence of BC adsorbent. It was found that 98.6% of total sulfur was removed by Me-BC/CuFe2O4. Thermodynamic data demonstrated that total sulfur adsorption was spontaneous and followed an endothermic path. Regeneration of the prepared adsorbents employing NaOH solution showed that the adsorbents have suitable reusabilities after five sorption and desorption runs.

Polarisation‐induced covalent interactions between H+ and surface O atoms promote clay aggregation

AbstractAccumulation of H+ can cause soil acidification, affect soil particle interactions, and alter soil processes. In this study, aggregation kinetics of montmorillonite colloids induced by monovalent ions of Li+ and H+ were determined by dynamic light scattering. The experimental results indicated that the critical coagulation concentration (CCC) value of Li+ was 4.5 times that of H+, indicating that H+ can strongly promote montmorillonite colloids aggregation. Joint analysis of the adsorption force type and energy of Li+ and H+ as well as the infrared spectroscopy of Li+ and H+ montmorillonite indicated that there was only electrostatic adsorption for Li+, while there was not only electrostatic adsorption but also a new type of covalent adsorption for H+: polarisation‐induced covalent adsorption. The total adsorption energy of H+ is thus much higher than that of Li+ on montmorillonite surfaces. Moreover, the polarisation‐induced covalent adsorption energy of H+ increased linearly with increasing electric field strength, which is consistent with the quantum mechanical analysis of the asymmetric orbital hybridisation of surface O atoms on montmorillonite. On this basis, the polarisation‐induced covalent adsorption energy of H+ was employed to predict the CCC value of H+ induced montmorillonite aggregation, and it was 7.40 mmol L−1. The high agreement with experimental results (7.26 mmol L−1) proved that the polarisation‐induced covalent interactions between H+ and surface O atoms promotes montmorillonite aggregation. This polarisation induced covalent effect between H+ and surface O atoms might further affect the formation and stability of soil aggregates and the pore status of soil structure, especially as soil acidification is currently becoming a global issue. The discovery from this study will improve our understanding of the effects of soil acidification on soil properties and processes.Highlights H+ greatly promoted clay aggregation. Polarization‐induced covalent between H+ and surface O presented at clay surface. Polarization‐induced covalent bonding energy increase with increasing electric field. Electrostatic and covalent bonding forces jointly determined clay aggregation.

Study on the difference in adsorption thermodynamics for water on swelling and non-swelling clays with implications for prevention and treatment of pneumoconiosis

Excessive inhalation of mineral dust can cause irreversible damage such as diffuse fibrosis of lung tissue. Water-based dust reduction technology can effectively control the dust concentration. The study of the interaction of water-clay mineral dust is helpful to the prevention and treatment of pneumoconiosis by water-based dust removal technology. To better understand the underlying adsorption mechanisms of water molecules on clay mineral dust, the detailed adsorption thermodynamics analysis is necessary. In this paper, we research the thermodynamics of adsorption of water molecules on swelling clay of montmorillonite and non-swelling clay of illite. First, the adsorption isotherms of water molecules on montmorillonite and illite at 293–313 K were measured by gravimetric method. Then, the key thermodynamic variables, including entropy change (Δ S ), surface potential ( Ω ), isosteric heat of adsorption ( Q st ) and variation of Gibbs free energy (Δ G ), were analyzed. Results illustrate that the adsorption amount for water molecules on illite is one order of magnitude smaller than that on montmorillonite, suggesting that swelling clay plays a dominant role in water molecules adsorption process. For water molecules adsorption on montmorillonite, the contribution of secondary adsorption to total adsorption ( a 2 / a ) is always less than 30%. For water molecules adsorption on illite, the contribution of primary adsorption to total adsorption ( a 1 / a ) is greater than a 2 / a at the low pressure region, while a 2 / a can exceed 60% at the high pressure region. The difference in the uptakes of water molecules adsorption on non-swelling and swelling clays is mainly resulted from the difference in primary adsorption on two clays. The Henry’s constant ( K AA ) for montmorillonite is in the range of 21.37–75.08 mmol/g/kPa, which is evidently larger than the K AA values of 0.34–0.98 mmol/g/kPa for illite. Compared with non-swelling clay, the adsorption spontaneity degree for water molecules on swelling clay is higher, and the interaction of swelling clay-water molecules is stronger. Meanwhile, the movement of adsorbed water molecules in swelling clay is more confined than that in non-swelling clay. These findings can offer meaningful guidelines for the prevention and treatment of pneumoconiosis.

Adsorption Characteristics of Three Types of Soils on Biogas Slurry Ammonium Nitrogen

Using farmland to digest biogas slurry is an effective measure to overcome the bottleneck of sewage treatment in livestock and poultry farms. However, there is limited research on the soil adsorption characteristics of biogas slurry ammonium nitrogen (NH4+-N). In addition, the maximum adsorption capacity (Qm) of farm soil is unclear. In this study, three typical farmland tillage layer soils (silty loam, loam, and sandy loam) were used to analyze adsorption characteristics through adsorption kinetics experiments (adsorption for 0.25, 0.5, 1, 2, 4, 6, 12, 18, or 24 h with NH4+-N concentrations of 42.90 mg/L) and thermodynamic experiments (adsorption for 3 days with NH4+-N concentrations of 54.25, 88.66, 105.85, 133.71, 178.80, 273.54, and 542.87 mg/L). The Qm value was fitted by models, and its relationship with soil properties was discussed. The results showed the following: 1) the adsorption of biogas slurry NH4+-N by the three types of soils was a composite kinetic process that comprised two stages of rapid and slow reactions. Rapid adsorption predominantly occurred within 0–1 h, and the adsorption capacity accounted for 35.24%–43.55% of the total adsorption. The ExpAssoc equation produced a good fit for the adsorption kinetic behavior in the three soil types. 2) The equilibrium adsorption could be described by the Langmuir equation, the Freundlich equation, the PlPlatt model, and the Langevin model isotherm, among which the Langevin model had the best fit, with a coefficient of determination R2 close to 1. The theoretical saturated Qm fitting results of NH4+-N were 1038.41–1372.44 mg/kg in silty loam, 840.85–1157.60 mg/kg in loam, and 412.33–481.85 mg/kg in sandy loam. The optimal values were 1108.55, 874.86, and 448.35 mg/kg for silty loam, loam, and sandy loam, respectively. 3) The Qm value was significantly positively correlated with soil organic matter, total nitrogen, available phosphorus, available potassium, cation exchange capacity, and particle content of 0.02–0.002 mm (p &amp;lt; 0.01), but significantly negatively correlated with soil pH (p &amp;lt; 0.05). This study can provide a reference for the safe application of biogas slurry on farmland.

Optimized synthesis of molecularly imprinted polymers coated magnetic UIO-66 MOFs for simultaneous specific removal and determination of multi types of macrolide antibiotics in water

Macrolide antibiotics (MALs) are widely used in various fields and are resistant to degrade in the water environment, thus constituting potential hazards to human health. In this work, a new composite, molecularly imprinted polymers coated magnetic metal-organic frameworks with carboxyl modification (M-UIO-66@MIPs) was selected and characterized, for the simultaneous specific adsorption and determination of five MALs from aqueous solution. It was found that UIO-66-COOH with ligand defects showed better pre-polymerization effect than other matrix materials. The synthesis conditions for the imprinting polymer were optimized via response surface methodology. The characteristics of related materials were studied, and a series of adsorption experiments were carried out. The results showed that the adsorption equilibriums of M-UIO-66@MIPs were reached within 1 h, with the total adsorption capacity for the five MALs was 99.05 mg g−1. The pseudo-second-order kinetic model and Freundlich isotherm model could best fit the adsorption process, and the adsorption thermodynamics was controlled by the change of entropy. Adsorption mechanisms were deduced as hydrogen bonding interaction and electrostatic interaction. In addition, M-UIO-66@MIPs has good selectivity and reusability. Furthermore, a new detection method for the five MALs was developed, using the prepared material as the adsorbent for magnetic solid-phase extraction, coupled with high-performance liquid chromatography. Under the optimal extraction condition, the limits of detection for five MALs were 3.1–44.6 μg L−1, and the recoveries were 92.9–108.7 % in the determination of real water samples. Therefore, the M-UIO-66@MIPs could be the efficient adsorbent for simultaneous selective removal and sensitive determination of multi-residual MALs.

Dynamics of Adsorption of Copper Ions in Fixed-Bed Column and Mathematical Interpretation of the First Stage of the Process

The dynamics of the adsorption process in the fixed-bed column was experimentally studied on the example of the system natural zeolite - water solution of copper salt with low concentrations, which are characteristic for wastewater treatment processes from toxic contaminants. The initial curves of the adsorption process for the height of the sorbent layer of 5 and 7 cm were constructed. The equilibrium of such processes can be described by Henry's linear equation. The adsorption process in the layer consists of two stages, which are examined in the study. The first stage is the formation of concentration front and the second one – its moving. The sum of the time of the first and second stages is the total adsorption time, which is determined before breakthrough time. The first stage of adsorption is mathematically formulated by the differential equation of molecular diffusion with a boundary condition of the first type. The second stage is supplemented by the balance equation, which takes into account not only the change of concentration in time, but also in the vertical coordinate and determines the time of movement of concentration front to breakthrough time. A mathematical model of the adsorption process in a fixed-bed column has been developed. Experimental data and theoretical calculations were compared. The results of statistical calculation of research results showed a satisfactory convergence of experimental and theoretical data.

Modification of Artichoke Dietary Fiber by Superfine Grinding and High-Pressure Homogenization and Its Protection against Cadmium Poisoning in Rats.

This study was carried out to investigate the effects of superfine grinding (SP) and high-pressure homogenization (HPH) on the structural and physicochemical properties of artichoke dietary fiber (ADF), as well as the protective effects against cadmium poisoning in rats. The structural characteristics and physicochemical properties of ADF, HPH-ADF (ADF treated by HPH) and CM-ADF (ADF treated by SP and HPH) were determined, and cadmium chloride (CdCl2) was induced by exposing rats for 7 weeks. The amounts of creatinine and urea; the activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in serum; the quantity of red blood cells, hemoglobin, white blood cells and neutrophil proportion in blood samples; and the activity of glutathione peroxidase (GSH-Px) in liver tissue were analyzed. Hematoxylin-eosin (HE) staining was performed to analyze the tissue structure and pathology of the liver and testis. The results showed that ADF subjected to HPH and SP-HPH exhibited increased content of soluble dietary fiber (SDF) (p < 0.05). HPH and SP-HPH treatments increased oil-holding capacity (OHC), total negative charge (TNC) and heavy metal adsorption capacity (p < 0.05). The CdCl2 intervention led to a significant increase in AST, ALT, creatinine, urea, neutrophil proportion and white blood cell count, as well as a significant decrease in GSH-Px activity, red blood cell count and hemoglobin (HGB) (p < 0.05). In rats fed with ADF, HPH-ADF and CM-ADF significantly reduced creatinine, urea amounts, ALT, AST activity in serum, leukocyte count and the neutrophil ratio in blood and increased GSH-Px activity in the liver, in addition to increasing the erythrocyte count and hemoglobin count in blood (p < 0.05). H&E staining results showed that steatosis in the liver was significantly reduced, whereas testicular tissue edema was improved. These results indicate that ADF exhibited positive activity against cadmium poisoning in rats and that CM-ADF had a better protective effect than ADF and HPH-ADF. ADF has specific potential to be used in health foods or therapeutic drugs, providing a reference for the development and utilization of artichoke waste.