Dynamic Adsorption Experiments Research Articles

Green synthesis of a hydrophobic metal-organic gel for the capture of trace odorous hexanal from humid air

The development of superhydrophobic adsorbents for the capture of trace volatile organic compounds (VOCs) from humid indoor air is still a challenge. Herein, we reported the formation of a granular zinc-based metal-organic gel, i.e., ZIF-412(gel) by optimizing the synthesis conditions. The thermally stable xerogel exhibited high surface area (1008 m2/g), hydrophobicity, and viscosity for self-depositing on the substrate such as non-woven fibers. Dynamic adsorption experiments under various humidity conditions demonstrated as-synthesized ZIF-412(gel) owned excellent VOC (hexanal) adsorption performance with adsorption capacity higher than commercial activated carbon and some water-stable MOFs including ZIF-8, ZIF-67, MIL-101(Cr) and ZIF-414. ZIF-412(gel) could be regenerated at temperature as low as 358 K without obvious loss in adsorption capacity. The adsorption mechanism of hexanal over ZIF-412(gel) is also simulated by Grand canonical Monte Carlo (GCMC).

Phosphate-functionalized ramie stalk adsorbent for efficient removal of Zn2+ from water: adsorption performance, mechanism, and fixed-bed column treatment of real wastewater.

A highly efficient adsorbent functionalized with phosphate groups made from a local agricultural waste, ramie stalk, was designed for Zn2+ removal from water. SEM, EDS, FTIR, zeta potential, and XPS tests were used to study the morphology and properties of modified ramie stalk (RS-P). The results showed that the phosphate groups were successfully grafted to the surface of the ramie stalk, which has a multilayered and porous structure and can provide large adsorption sites. Adsorption performance and mechanism were investigated in the static and dynamic adsorption experiments. The adsorption kinetics of Zn2+ by RS-P were better fitted by the pseudo-second-order model, indicating chemical adsorption. Adsorption isotherm was better described by Redlich-Peterson isotherm, which suggested heterogeneous and multi-site adsorption, with a maximum adsorption capacity of 0.558mmolg-1. The characterization of adsorbents before and after adsorption indicated that a combined action of electrostatic interaction and ion exchange was the primary mechanism of adsorption. Dynamic adsorption experiments with fixed-bed column displayed excellent water treatment capabilities. RS-P exhibited good reusability in 5 cycles without much deterioration in its adsorption performances. Complex co-existing ions impaired Zn2+ adsorption during real wastewater treatment. This research benefits agricultural waste recycling and provides safe water to ensure economic, social, and environmental sustainability.

Water Treatment Method for Removal of Select Heavy Metals and Nutrient Ions Through Adsorption by Magnetite

This study explored the removal of contaminants from surrogate solutions using magnetite particles. Commercially available magnetite was used for the removal of copper, lead, nitrate, and phosphate from surrogate solutions. Single-stage experiments with copper, lead, and phosphate surrogate solutions achieved over 98% removal, while nitrate removal experiments only achieved 7.47%, in 24 h at high (20 g/L) magnetite doses and initial concentrations of 100 mg contaminant/L. Two-stage experiments with copper showed over 99.9% cumulative removal after the second stage. Adsorption kinetics experiments for copper, lead, and phosphate demonstrate rapid uptake of contaminants with high doses of magnetite, removing over 90% of contaminants in 4 min or less and follow a pseudo-second-order model. Ultimately, this study aims to establish the minimum magnetite dose and/or minimum number of stages required to remove contaminants below water quality standards for human and/or aquatic life. Water pollution is a serious global issue, and this study poses a potential solution that can be modified for a variety of applications, including environmental contamination and industrial wastewater treatment.

A high-flux antibacterial poly(amidoxime)-polyacrylonitrile blend membrane for highly efficient uranium extraction from seawater

Uranium is an important fuel for nuclear power, with 4.5 billion tons of it stored in the oceans, 1,000 times more than on land. Polymer membrane materials are widely used in the marine resources fields, due to their convenient collection, good separation and can work continuously. Herein, a poly(amidoxime)-polyacrylonitrile blend membrane (PCP) with high flux, excellent antibacterial properties and uranium adsorption performance has been prepared by using the phase inversion method, and the prepared membrane was used for highly efficient uranium extraction from seawater. In static adsorption experiments, the PCP membrane reached adsorption equilibrium after 48 h, and the adsorption capacity was 303.89 mg/g (C0 =50 mg/L). In dynamic adsorption experiments, it was found that the lower flow rate and higher number of membrane layers were favorable for dynamic adsorption. In addition, the water flux of the PCP membrane was 7.4 times higher than that of the PAN membrane. The adsorption mechanism can be attributed to the chelation between amino and hydroxyl groups in CS, amidoxime group in poly(amidoxime) and uranyl ions. The simple preparation process coupled with the excellent adsorption performance indicated that the PCP membrane would be a promising material for the uranium extraction from seawater.

Activated carbon from polyurethane residues as molecular sieves for kinetic adsorption/separation of CO2/CH4

Activated carbon-based molecular sieves were synthetized, characterized and their kinetics of adsorption were evaluated to be used in separation processes of CO2/CH4 mixtures. Polyurethane (PU) foams were used as carbon precursors and the PU-derived carbons were physical activated with CO2. All the samples present a preferential adsorption of CO2 over methane in kinetic adsorption experiments. Samples activated at 800 ºC during 6 h exhibited the highest selectivity due to the absence of methane adsorption at lower resident times, which makes those samples very interesting for industrial processes of natural gas purification. Kinetic studies were performed to explain the kinetic profiles obtained, confirming that in the samples with smallest pore size, intraparticle diffusion was the limiting step, evidencing that certain oxygen groups favour CO2 adsorption, whereas adsorption was the limiting step in the samples with wider pores.

Effect of Cucurbit[7]uril on Adsorption of Aniline Derivatives at Quartz

The adsorption behavior of small molecules at solid–liquid interfaces have become an important research topic in recent years. For example, small molecules of aniline pollutants will adsorb on solid surfaces with a massive discharge of industrial wastewater and are difficult to separate. Therefore, their adsorption and desorption on solid surfaces have become an important scientific problem. In this study, the interactions of cucurbit[7]uril (Q[7]) with 4,4′-diaminodiphenylmethane (MDA) and benzidine (AN) are studied using 1H NMR, UV-Vis spectrometry and fluorescence spectroscopy. The results show that Q[7] forms an inclusion complex with MDA and AN. According to the results of Quartz Crystal Microbalance with Dissipation (QCM-D), MDA adsorbs onto a quartz surface and forms a viscous adsorption layer on it. The AN adsorbs on the quartz surface and forms a rigid adsorption film on it. Q[7] can reduce the adsorption of MDA on the quartz surface and increases the adsorption of AN on it. Through the dynamic adsorption experiments, we find that Q[7] has a desorption effect on MDA molecules adsorbed on the quartz surface. An Atomic Force Microscope (AFM) is used to measure the morphological changes in the adsorption film before and after Q[7] makes contact with the quartz surface, and it proves that Q[7] has a desorption effect on MDA molecules adsorbed on the surface.

Flavonoids from Lycium barbarum Leaves Exhibit Anti-Aging Effects through the Redox-Modulation.

Lycium barbarum leaves are a kind of vegetable, and modern nutrition studies have found that they have an anti-aging function. Our study aims to investigate the anti-aging effects of Lycium barbarum leaf flavonoid (LBLF) extracts and its underlying molecular mechanism. LBLFs were purified using D101 and polyamide resin, characterized by ultraperformance liquid chromatography coupled with mass spectrometry, and administered to hydrogen peroxide (H2O2)-treated human umbilical vein endothelial cells (HUVECs) and Caenorhabditis elegans. Appropriate enrichment conditions were optimized through dynamic adsorption and desorption experiments, the content of flavonoids reached 909.84 mg/g, rutin and kaempferol being the main ones. LBLFs attenuated H2O2-induced HUVEC apoptosis, decreased reactive oxygen species and malondialdehyde production levels, increased superoxide dismutase, glutathione peroxidase and catalase activities. Furthermore, pre-treatment with LBLF increased mRNA expression of erythropoietin (EPO) and heme oxygenase-1 (HO-1) via the mitogen-activated protein kinase (MAPK) signaling pathway in HUVECs. Compared with 100 µM rutin monomer, LBLF prolonged the lifespan of Caenorhabditis elegans, enhanced their mobility in middle life stages and upregulated expression of sod-2, gcs-1 and skn-1 genes, which indicated that the anti-aging effects of LBLF were due to its redox-modulation.

Fabrication of Uio-66-NH2 with 4,6-Diamino-2-mercaptopyrimidine facilitate the removal of Pb2+ in aqueous medium: Nitrogen and sulfur act as the main adsorption sites

In this work, the Zr-based MOF was successfully fabricated with 4,6-Diamino-2-mercaptopyrimidine (DMP) and a novel adsorbent (Uio-DMP) was synthesized for the immobilization of Pb2+ in aqueous medium. The morphological and structural characteristics of Uio-DMP were characterized by X-ray diffractometer (XRD), Fourier transform infrared (FT-IR), Field emission scanning electron microscopy (FE-SEM), Brunner Emmet Teller (BET), and X-ray photoelectron spectroscopy (XPS). The characterization results showed that the Uio-DMP maintained a pristine crystal structure and the sulfhydryl group was introduced to Zr-based MOF after chemical functionalization. The adsorption behavior of Uio-DMP for Pb2+ was investigated in different conditions (solution pH, sorbent dose, Pb2+ concentration, adsorption time, and co-existing ions). The experimental results indicated that the optimal pH was 6, the maximum adsorption capacity was 296.5 mg/g, and the Langmuir model well fitted the Pb2+ removal process based on adsorption isotherm studies. The adsorption kinetic experiments revealed that the adsorption equilibrium could be achieved at 30 min and the adsorption process was consistent with the Pseudo-second-order model. The co-existing ions had a limited impact on Pb2+ removal and the removal rate of 71.0% was maintained after five consecutive adsorption-desorption experiments. Furthermore, zeta potential and XPS analysis proved that the removal process of Pb2+ over Uio-DMP was affected by electrostatic interaction, and nitrogen/sulfur atoms acting as the main adsorption sites. This study provides an insight into the removal of Pb2+ in aqueous medium and the functionalization of adsorbents.

Ultra-adsorption enhancing peroxymonosulfate activation by ultrathin NiAl-layered double hydroxides for efficient degradation of sulfonamide antibiotics

Sulfonamides have attracted special attention due to their widespread use and refractory nature in the aquatic environment. Heterogeneous catalytic peroxymonosulfate (PMS) activation for sulfonamide degradation has been demonstrated to be an encouraging strategy. Herein, ultrathin nickel aluminium layered double hydroxide (U–NiAl-LDH) was employed as an efficient peroxymonosulfate activator. The adsorption kinetics experiment showed that U–NiAl-LDH exhibited a super-adsorption phenomenon for sulfonamide antibiotics, such as sulfamethoxazole (SMX) and sulfachloropyridazine (SCP). U–NiAl-LDH was composed of 6 layers of a NiAl bimetallic layer structure. The degradation performance of organic contaminants via PMS activation was greatly accelerated by decreasing the number of LDH layers. Ni(II) on the surface of U–NiAl-LDH activated PMS to produce surface-bound hydroxyl radicals and sulfate radicals by donating electrons to cleave the O–O bond of PMS. These in-situ generated reactive oxygen species (ROS) on the surface of U–NiAl-LDH could directly attack adjacent adsorbed SMX or SCP molecules, where the migration distance between the ROS and target contaminants was reduced. Consequently, super-adsorption synergistically promoted the degradation efficiency of SMX and SCP, which decreased the demand for PMS. The newly found ultra-adsorption enhancing peroxymonosulfate activation effect was pioneered for the ultrafast elimination of sulfonamide antibiotics in real water. This proposed mechanism provides preliminary guiding significance to design PMS catalysts with dual reaction sites for the treatment of targeted refractory organic contaminant wastewater.

A Zeolitic Octahedral Metal Oxide with Ultra-Microporosity for Inverse CO2 /C2 H2 Separation at High Temperature and Humidity.

Separation of CO2 /C2 H2 to obtain pure C2 H2 presents a challenge for the chemical industry. CO2 -selective adsorbents are favored because of the convenient separation process. However, there are only a few CO2 -selective adsorbents that can effectively isolate CO2 from CO2 /C2 H2 , and there is almost no research on CO2 /C2 H2 separation under harsh conditions, such as with high temperatures and humidities. Herein, a zeolitic octahedral metal oxide based on ϵ-Keggin polyoxometalates is utilized for separations of CO2 /C2 H2 at high temperatures and humidities. Single gas adsorption measurements show that the material only adsorbs CO2 with almost no C2 H2 taken up. Dynamic competitive adsorption experiments show that the material efficiently separates CO2 /C2 H2 , and highly pure C2 H2 is obtained directly. The robust material maintains a high separation performance at 333 K with 18.12 % water. The high stability of the material enables reuse without loss of separation performance.

A Zeolitic Octahedral Metal Oxide with Ultra‐Microporosity for Inverse CO2/C2H2Separation at High Temperature and Humidity

AbstractSeparation of CO2/C2H2to obtain pure C2H2presents a challenge for the chemical industry. CO2‐selective adsorbents are favored because of the convenient separation process. However, there are only a few CO2‐selective adsorbents that can effectively isolate CO2from CO2/C2H2, and there is almost no research on CO2/C2H2separation under harsh conditions, such as with high temperatures and humidities. Herein, a zeolitic octahedral metal oxide based on ϵ‐Keggin polyoxometalates is utilized for separations of CO2/C2H2at high temperatures and humidities. Single gas adsorption measurements show that the material only adsorbs CO2with almost no C2H2taken up. Dynamic competitive adsorption experiments show that the material efficiently separates CO2/C2H2, and highly pure C2H2is obtained directly. The robust material maintains a high separation performance at 333 K with 18.12 % water. The high stability of the material enables reuse without loss of separation performance.

A stable solid amine adsorbent with interconnected open-cell structure for rapid CO2 adsorption and CO2/CH4 separation

A novel stable porous solid amine adsorbent with three-dimensional interpenetrating network structure was prepared by polymerization of divinylbenzene using high internal phase emulsion (HIPE) template method, and followed by further introducing polyethyleneimine (PEI) by impregnation-crosslinking method. Fixed bed dynamic adsorption experiment proved that under wet condition, the former exhibited not only a higher capacity of 6.22 mmol/g but also a better adsorption kinetics process with faster adsorption rate and longer lag in breakthrough point, which makes it potential to be used in gas separation. In CO2/CH4 separation experiment, PolyHIPE-PE30-4 showed a CO2/CH4 separation selectivity of 253 at 298 K and 1 bar, and meanwhile exhibited an extra-high operating capacity. The pure methane productivity of PolyHIPE-PE30-4 was 24.1 mmol/g from CO2/CH4 (80:20, v/v) mixed gas, 4.5 times to that of PE30-4 gel (5.36 mmol/g). Significantly, PolyHIPE-PE30-4 could maintain an excellent regeneration performance after at least 7 cycles, while PolyHIPE-P30 exhibited a remarkably decrease in adsorption capacity after only three adsorption-desorption process in wet condition, demonstrating the advantage of impregnation-crosslinking method for amine functionalization. The superior CO2 adsorption capacity and regeneration stability, combined with its superior adsorption kinetics property make it a broad prospect in the field of CO2/CH4 separation.

Superior Iodine Uptake Capacity Enabled by an Open Metal-Sulfide Framework Composed of Three Types of Active Sites

Superior Iodine Uptake Capacity Enabled by an Open Metal-Sulfide Framework Composed of Three Types of Active Sites

Iron Sulfide Scale Inhibition in Carbonate Reservoirs.

Hydrocarbon production operations include water injection, varying stimulation approaches, and enhanced oil recovery techniques. These treatments often affect reservoir formation, production, and injection facilities. Such sorts of well operations cause the formation of organic and inorganic scales in the near-wellbore region and various production and injection structures. Downhole squeeze treatment is commonly used as a control measure to prevent scale precipitation. A scale inhibitor solution is introduced into a formation by applying a squeeze treatment. The method allows scale inhibitors to adsorb on the internal rock surface to avoid settling down the scale precipitates. Thus, the study of adsorption of different types of inhibitors to prevent scale formation on the reservoir rock through the execution of downhole squeeze treatment is becoming necessary. This study incorporated different experimental techniques, including dynamic adsorption experiments of chelating agents employing a coreflooding setup, inductively coupled plasma-optical emission spectrometry (ICP-OES) to inhibit the formation of iron-containing scales in limestone rocks, and ζ-potential measurements targeting determination of iron precipitation in varying pH environments on calcite minerals. The influence of the inhibitor soaking time and salt existence in the system on chelating agent adsorption was also evaluated in the coreflooding experiments. The findings based on the coreflooding tests reveal that the concentration of chelating agents plays a significant role in their adsorption on carbonate rocks. The treatments with 20 wt % ethylenediaminetetraacetic acid (EDTA) and 20 wt % diethylenetriaminepentaacetic acid produced the highest adsorption capacity in limestone rock samples by inhibiting 84 and 85% of iron(III) ions, respectively. Moreover, the presence of the salts (CaCl2 and MgCl2) considerably decreased the adsorption of 10 wt % EDTA to 56% (CaCl2) and 52% (MgCl2) and caused nearly 20% more permeability reduction, while more inhibitor soaking time resulted in comparably higher adsorption and lesser permeability diminution. The results of ζ-potential measurements showed that the pH environment controls iron(II) and (III) precipitation, and iron(III) starts to deposit from a low pH region, whereas iron(II) precipitates in increased pH environments in calcite minerals.

Kinetics of Gas Phase CO2 Adsorption on Bituminous Coal from a Shallow Coal Seam

This article examines the CO2 adsorption–desorption kinetics of bituminous coal under low pressure injection (0.5 MPa) in the context of CO2 sequestration in shallow level coal seams. This study used two different sizes of intact core samples of bituminous samples from seam no. 30 at the Experimental Mine Barbara (EMB) in Katowice, Poland. Manometric adsorption kinetics experiments were conducted on 50 mm dia. 60 mm long coal core samples (referred to as EMB1) and 50 mm dia. 30 mm long coal core samples (referred to as EMB2). The kinetics of adsorption at injection pressures ranging from 0.1 to 0.5 MPa were compared to those at elevated pressures ranging from 0.5 to 4.5 MPa. For the first time, intact sample adsorption–desorption data were fitted in pseudo first order (PFO), pseudo second order (PSO), and Bangham pore diffusion models. The PSO model fits the data better than the PFO model, indicating that bulk pore diffusion, surface interaction, and multilayer adsorption are the rate-determining steps. Comparing the equilibrium amount of adsorbed (qe) obtained for the powdered samples (9.06 g of CO2/kg of coal at 0.52 MPa) with intact samples (11.68 g/kg at 0.53 MPa and 7.58 g/kg at 0.52 MPa for the intact EMB1 and EMB2 samples) showed the importance of conducting experiments with intact samples. The better fit obtained with the Bangham model for lower pressure equilibrium pressures (up to 0.5 MPa) compared to higher pressure equilibrium pressures (4.5 MPa) indicates that bulk pore diffusion is the rate-determining step at lower pressures and surface interaction takes over at higher pressures. The amount of CO2 trapped within the coal structure following the desorption experiments strengthens the case for intact bituminous coal samples’ pore trapping capabilities.

Effect of nitrogen functional groups on competitive adsorption between toluene and water vapor onto nitrogen-doped spherical resorcinol-formaldehyde resin-based activated carbon.

To elucidate the effect of nitrogen functional groups on the competitive adsorption of toluene and water vapor, a series of N-doped resorcinol-formaldehyde resin-based activated carbons using g-C3N4 as the nitrogen source were prepared, which possessed different N contents (1.29-6.14%). The competitive adsorption characteristics and mechanisms were investigated by characterizations, dynamic adsorption experiments, adsorption isotherms, and density functional theory calculations. Results showed that the normalized toluene adsorption capacity under 50 RH% was consistent with the N content, revealing that nitrogen functional groups can enhance the competitive adsorption for toluene under a humid atmosphere. Adsorption isotherms analysis suggested that nitrogen functional groups can not only accelerate the adsorption of toluene but also improve the hydrophobicity of carbon surface. Competitive adsorption mechanisms were ascribed to π-π interactions and electrostatic interactions. Specifically, graphitic-N and pyridinic-N enhance competitive adsorption for toluene through reinforced π-π interactions with toluene and weakened electrostatic interactions with water molecule. However, pyrrolic-N improve the competitive adsorption, which is principally attributed to enhanced π-π interactions with toluene. Furthermore, it was found that the reusability of activated carbon could be improved by nitrogen functional groups. This study provides theoretical hints to develop volatile organic compound adsorbents in the presence of water vapor.

Purification of ferulic acid from corn fibre alkaline extracts for bio-vanillin production using an adsorption process

Ferulic acid is the most widely studied precursor for bio-vanillin production. This work assesses the use of an alkaline extract from corn fibre for bio-vanillin production. The results show that after extraction an additional step is needed to purify ferulic acid removing toxic/inhibitor compounds. An adsorption process was selected to purify the ferulic acid. The performances of four different macroporous resins prepared from different matrix materials were evaluated. Macronet® MN102 (not yet reported for ferulic acid purification) offered the highest ferulic acid adsorption capacity. A column packed with Macronet® MN102 was used to perform dynamic adsorption and desorption experiments, which showed a maximum ferulic acid adsorption capacity of 176 mgferulic acid.g−1dry resin at pH 4.5 at a flow rate of 3.7 BV (bed volumes).h−1. The breakthrough point was at 115 min, corresponding to an adsorption capacity of 85 mgferulic acid.g−1dry resin. In the desorption step, 90.9% of ferulic acid was recovered using absolute ethanol ≥ 99.8%) as eluent, at the same flow rate of 3.7 BV (bed volumes).h−1. This procedure confirmed the removal of compounds with a microbial inhibitory effect, such as organic acids, metals and some aldehydes. The purified ferulic acid extract was then used to produce bio-vanillin. The bio-vanillin production by Amycolatopsis sp. ATCC 39116, using a single pulse of an extract with 10 g.L-1 of ferulic acid extract, led to a maximum vanillin concentration of 5 g.L-1 and a vanillin yield of 0.52 gvanillin.gferulic acid-1, values comparable to those obtained with a commercial solution containing 10 g.L-1 of ferulic acid.

Magnetic porous cellulose surface-imprinted polymers synthetized with assistance of deep eutectic solvent for specific recognition and purification of bisphenols

Magnetic porous cellulose molecularly imprinted polymers-based bisphenols have been developed using Fe3O4 as the magnetic material, a deep eutectic solvent as the assisted solvent, and N-isopropylacrylamide as the functional monomer. The resulting magnetic porous cellulose molecularly imprinted polymers were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometry, thermal gravimetric analysis, and Brunauer–Emmett–Teller analysis. Moreover, the adsorption properties of the magnetic porous cellulose molecularly imprinted polymers toward bisphenol A, bisphenol F, and bisphenol AF were investigated using static, dynamic, and selective adsorption experiments. The introduction of porous cellulose materials significantly improves the capabilities of the material. The adsorption capacity, mass transfer efficiency, and selectivity of the magnetic porous cellulose molecularly imprinted polymers toward bisphenol A were 5.9, 4.0, and 4.4 times those of traditional molecularly imprinted polymers. Moreover, the adsorption stability of the magnetic porous cellulose molecularly imprinted polymers was investigated under different temperature and pH conditions. The adsorption characteristics of the magnetic porous cellulose molecularly imprinted polymers toward the target molecules were investigated using adsorption isotherm, kinetic, and thermodynamic models. Hydrogen bonding is the main interaction formed between the magnetic porous cellulose molecularly imprinted polymers and the target molecules. Magnetic porous cellulose molecularly imprinted polymers have great application value with excellent stability and reusability. Finally, the combination of the magnetic porous cellulose molecularly imprinted polymers and high-performance liquid chromatography or ultra-performance liquid chromatography-mass spectrometry was successfully used for the purification and detection of bisphenols in milk (1.349 ng/mL bisphenol F and 3.014 ng/mL bisphenol AF), canned fruits (1129 ng/mL bisphenol A, 10.11 ng/mL bisphenol F, and 91.87 ng/mL bisphenol AF), and fish (11.91 ng/mL bisphenol AF) samples. Furthermore, the magnetic porous cellulose molecularly imprinted polymer method is more selective, sensitive, and accurate than the traditional precipitation method.

Analysis of Sequential Adsorption–Oxidation of VOCs on Atomic Layer-Deposited PtNi/ZrO2–SiO2 Dual-Function Materials

To develop efficient dual-function materials (DFMs) for capture and destruction of volatile organic compounds (VOCs), we prepared a series of composite materials comprising PtNi nanoparticles supported on ZrO2-promoted SiO2 (PtNi/ZrO2–SiO2) via atomic layer deposition (ALD) method and investigated them for sequential adsorption and desorption/catalytic oxidation of benzene, as a model VOC compound. ZrO2 was first deposited on a unimodal SiO2 support, followed by deposition of Pt and Ni nanoparticles with varried amount. Dynamic adsorption experiments were conducted using a 500 ppmv-laden feed at 25 °C and 1 atm, followed by in situ catalytic oxidation at 200 °C. Among the DFMs investigated, 1Pt2Ni/ZrSi emerged as the material with overall in situ conversion of ∼96% due to its retaively high PtNi acid sites density compared with other DFMs. Kinetic analysis was conducted on 1Pt2Ni/ZrSi by investigating the effects of feed concentration, regenerative feed flow rate, and oxidation temperature on the benzene conversion in the sequential adsorption–oxidation process. The results of the kinetic analysis revealed that a complete oxidation can be attained over 1Pt2Ni/ZrSi and its performance can be improved upon decreasing adsorptive feed benzene concentration (maximum value of 99.7% at 125 ppmv) and regenerative feed flow rate (100% at 5 mL/min), and increasing oxidation temperature (100% at 200 °C). Overall, the obtained results highlighted the optimal operation conditions for sequential adsorption and oxidation of VOCs over ALD-based DFMs.

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 < 0.01), but significantly negatively correlated with soil pH (p < 0.05). This study can provide a reference for the safe application of biogas slurry on farmland.