Equilibrium Time Research Articles

Highly selective capture of Hg(II) utilizing a MXene-based magnetic cenosphere: Balance on redox sites and magnetism

Hg(II), as a hazardous water pollutant, is attracting increasing attention due to its severe ecological and biological toxicity. Herein, a magnetic composite MXene/Fe3O4/FAC for aqueous Hg(II) uptake was prepared. It appeared fast adsorption kinetics (∼30 min of adsorption equilibrium time), high Hg capacity (924.34 mg/g), broad working pH range (pH=4–12), and high selectivity. Besides, the implanted Fe3O4 empowered the composite with good recycling and reusing characteristics, effectively preventing the release of nanomaterials into the environment. Multiple adsorption models and characterizations revealed the Hg(II) adsorption behaviors and mechanisms and the impact of Fe3O4 on Hg(II) adsorption onto MXene. Specifically, Hg(II) reductive adsorption aroused by the low-valence Ti species (abbreviated as Ti*) is the foremost mode of MXene. With the increasing of Fe3O4 (especially trivalent Fe), Ti* tends to be oxidized and covered by Fe3O4, and less Ti* can be used for Hg(II) reductive adsorption, leading to slower adsorption kinetics and lower adsorption capacity. The introduced inert carrier FAC favors the good dispersion of Fe3O4 and MXene to alleviate the oxidation of MXene, achieving the high utilization of MXene materials. The new insight into the interaction between MXene and Fe3O4 can beneficially guide the synthesis of Hg(II) magnetic adsorbents and MXene-based functional materials.

Chromium (VI) removal by magnetite nanoparticles immobilized with extracellular polymeric substances extracted from Lysinibacillus sp. WH.

Magnetite nanoparticles (nano-Fe3O4) and nano-Fe3O4 immobilized with bacterial extracellular polymeric substances (EPSs) extracted from Lysinibacillus sp. WH (Fe3O4/bact) were comparatively studied for the removal of Cr (VI) ions from aqueous solution in batch study. The objectives were to explore the removal of Cr (VI) efficiency by nano-Fe3O4 and Fe3O4/bact under varying bacterial concentrations at a range of acidic pH. Results indicated that 150 ppm Cr (VI) could be effectively removed by 5 g/L of nano-Fe3O4 at pH 4, with the efficiency of 89.2 ± 12%. The equilibrium time, determined by a pseudo-second-order model (R2 = 0.9983), was after 5 h, indicating chemical adsorption. The Cr (VI) removal by the nano-Fe3O4 immobilized with bacterial EPS was effective and steady under a wide range of acidic conditions although bacterial EPS has an alkaline nature. Here, we are the first to demonstrate that Cr (VI) removal efficiency by different concentrations of EPS was not significantly different, suggesting EPS concentration is possibly not the most crucial factor to be optimized for Cr (VI) removal in the future. This study shows the potential application of nano-Fe3O4 immobilized with bacterial EPS for wastewater treatment. PRACTITIONER POINTS: The equilibrium time for magnetite nanoparticles to remove Cr (VI) is 5 h, suggesting chemical adsorption. The Cr (VI) removal efficiency of either magnetite nanoparticles or bacterial EPS is stable under a wide range of acidic conditions. Magnetite nanoparticles immobilized with bacterial EPS extracted from Lysinibacillus sp. WH has a potential application for Cr (VI) removal in wastewater.

Nutrient accumulations in high-saline bottom waters in the eutrophic East China Sea inner shelf

Despite decades of mitigation efforts, eutrophication-induced algal blooms and hypoxia have not significantly decreased globally, possibly due to the legacy effects of eutrophication. The legacy effect has been more explored in inland waters and enclosed estuaries than in open coastal waters. Here, we reanalyzed cruise data from the East China Sea inner shelf to explore the effect of eutrophication on nutrient accumulations in high-saline bottom waters. Our dataset showed elevated nitrate (12.75 ± 6.51 μmol L−1) and phosphate (0.85 ± 0.26 μmol L−1) in high-salinity (salinity>34, temperature < 23 °C) bottom waters during the summer of 2006 to 2013. They were higher than those typically observed in the Taiwan Warm Current Bottom Water by approximately 5.45 ± 6.51, and 0.29 ± 0.26 μmol L−1, respectively. Significant correlations of nitrate with apparent oxygen utilization (AOU) and elevated AOU suggested that organic matter decomposition contributed to increased nitrate in bottom waters under eutrophication conditions. Based on an end-member mixing estimation, we found that the organic matter decomposition accounted for 28% to 37% of the nutrient concentrations in the bottom waters, with a standard deviation of 20%. Results from our mass-balance model indicated that 40–74% of regenerated nutrients are flushed out of the model box set within 95% equilibrium time due to the advection of offshore waters, assuming a residence time of 46.0 to 13.9 days. Based on cruise results in June and August 2009, the net accumulation rates of nitrate, phosphate, and AOU in the Taiwan Warm Current Bottom Water were estimated to be 0.046, 0.0036, and 0.44 μmol L−1 d−1, respectively. Such nutrient accumulations in the water column and the residual nutrients in sediment are crucial legacy nutrients, potentially triggering algal blooms. Conversely, the flushing effect suggests a significant transport of nutrients and other chemical elements to the offshore and open ocean.

Insights into role of microstructure in TNT adsorption performances onto zeolite, diatomite and kaolinite particles

Adsorption performances of one pollutant on different adsorbents likely depend on the adsorbent microstructures heavily. Hereon, zeolite, diatomite and kaolinite particles were selected as inexpensive adsorbents in this study with 2,4,6-trinitrotoluene (TNT) as an organic pollutant for the batch test to verify the effect of adsorbent microstructure on TNT adsorption performance. The results of kinetic, adsorption isothermic, and thermodynamic analyses indicated that the adsorption process of TNT on three particles is controlled by chemisorption, and that both are non-spontaneous entropic endothermic reactions, although they have their own specific adsorption capacities, equilibration times, and kinetic rates. Comprehensively analyzing the characterization data and adsorption performances of the particles shows that, the pore physical properties including the pore diameter distribution and volume obviously control the adsorption capacities, and well the pore surface chemical properties such as the functional groups affect the adsorption kinetics; the microstructure affects the performances through the synergistic effect of physical and chemical pathways and results in the special performances. Briefly, a particle has its special microstructure and then determinedly unique performance. The finding provides insights into the role of the microstructure of the particles in their performances, and significances for selecting and utilizing the adsorbents in water treatment.

MXene@polydopamine/oxidized sodium alginate modified collagen composite aerogel as sustainable bio-adsorbent for heavy metal ion adsorption and solar driven water evaporation

The design of an environmentally friendly bio-adsorbent for the removal of heavy metal ions from aqueous media is a sustainable strategy to ensure water safety. Herein, a three-dimensional macroscopic aerogel with photothermal conversion and heavy metal wastewater treatment capability was designed using leather collagen, MXene@polydopamine and oxidized sodium alginate as raw materials, named as MPAC composite aerogel. The applicability of the developed MPAC composite aerogel in water evaporation and heavy metal wastewater treatment was studied. MPAC composite aerogel had good Cr(VI) adsorption capacity. This article focused on the study of adsorption kinetics, isotherms and thermodynamics. The adsorption equilibrium time of MPAC composite aerogel was 60 min, and the equilibrium adsorption capacity of MPAC composite aerogel for Cr(VI) reached 80.73, 100.80 and 112.86 mg/g when the initial Cr(VI) concentration was 30, 70 and 100 mg/L, respectively. The adsorption process of Cr(VI) by MPAC composite aerogel conformed to the two-level dynamics model and the Freundlich adsorption isotherm model, and was a spontaneous endothermic reaction. Additionally, the composite aerogel had good solar-driven water evaporation ability and could enhance the water evaporation rate of Cr(VI) solution. Furthermore, the MPAC composite aerogel had high adsorption performance for Cr(VI) under solar illumination conditions. This new aerogel has the advantages of low cost, environmental friendliness, strong adsorption capacity and photothermal conversion performance and is a promising heavy metal ion adsorbent.

Computer simulation‐guided template selection for a molecularly imprinted polymer for selective trifluralin adsorption

AbstractTo meet selective adsorption toward trifluralin, a novel molecularly imprinted polymer (MIP) was fabricated by the dummy template molecular imprinting technology. First, computational simulation was performed to select a suitable dummy template, 3,5‐dinitro‐4‐methylbenzoic acid (T1), based on the maximum basis set superposition error (BSSE)‐corrected binding interaction energy (ΔE) of the monomer N‐vinylpyrrolidone (NVP)‐T1 complex and its structural overlap with trifluralin. Then, the MIP was prepared via the bulk polymerization. The adsorption experiments showed the MIP exhibited a trifluralin adsorption capacity of 5.1 mg g−1, an imprinting factor (IF) of 2.2, and short adsorption equilibrium time of 5 min. The adsorption of trifluralin conformed to the Freundlich adsorption (R2 = 0.985) and pseudo‐second‐order model (R2 = 0.999). In addition, the MIP exhibited selectivity to trifluralin over other adsorbents, including structural analogs (pendimethalin and oryzalin), pesticide (carbendazim), and nitrocompounds (nitrofurantoin, furazolidone, and furaltadone), with the selectivity factor (β) in the range of 1.2–3.0, respectively. In trifluralin/oryzalin mixture, the IF toward oryzalin was still as high as 1.9. The removal rate of the MIP to trifluralin in environmental water samples ranged from 90.08% to 99.04%. This study provides theoretical and experimental insights for the preparation of MIP using dummy templates.

Dye Sorption from Mixtures on Chitosan Sorbents.

This article presents studies on the sorption of the anionic dyes Reactive Black 5 (RB5) and Reactive Yellow 84 (RY84) from solutions of single dyes and from dye mixtures onto three chitosan sorbents-chitin, chitosan DD75% and chitosan DD95%. In this work, the influence of pH on sorption efficiency, the sorption equilibrium time for the tested anionic dyes and the sorption capacity in relation to the individual dyes and their mixtures were determined. It has been found that the sorption process for both dyes was most effective at pH 3 for chitin and chitosan DD75 and at pH 4 for chitosan DD95%. The obtained results were described by the double Langmuir equation (Langmuir 2). The obtained constants made it possible to determine the affinity of the tested dyes for the three sorbents and the sorption capacity of the sorbents. For RB5, the highest sorption capacity for chitosan DD95% was achieved with sorption from a single solution-of 742 mg/g DM and with sorption from mixed dyes-of 528 mg/g DM. For RY84, the highest efficiency was also achieved for chitosan DD95% and was 760 mg/g DM for a single dye solution and 437 mg/g DM for a mixture of dyes.

Modeling of the Time-Dependent H2 Emission and Equilibrium Time in H2-Enriched Polymers with Cylindrical, Spherical and Sheet Shapes and Comparisons with Experimental Investigations.

Time-dependent emitted H2 content modeling via a reliable diffusion analysis program was performed for H2-enriched polymers under high pressure. Here, the emitted hydrogen concentration versus elapsed time was obtained at different diffusivities and volume dimensions for cylinder-, sphere- and sheet-shaped specimens. The desorption equilibrium time, defined as the time when the H2 emission content is nearly saturated, was an essential factor for determining the periodic cyclic testing and high-pressure H2 exposure effect. The equilibrium time in the desorption process was modeled. The equilibrium time revealed an exponential growth behavior with respect to the squared thickness and the squared diameter of the cylinder--shaped specimen, while it was proportional to the squared diameter for the sphere-shaped specimen and to the squared thickness for the sheet-shaped specimen. Linear relationships between the reciprocal equilibrium time and diffusivity were found for all shaped polymers. The modeling results were confirmed by analysis of the solutions using Fick's second diffusion law and were consistent with the experimental investigations. Numerical modeling provides a useful tool for predicting the time-dependent emitted H2 behavior and desorption equilibrium time. With a known diffusivity, a complicated time-dependent emitted H2 behavior with a multi-exponential form of an infinite series could also be predicted for the three shaped samples using a diffusion analysis program.

Verification of thermodynamic parameters of a mixture of generator gas on oxygen-hydrogen fuel with an excess of one of the fuel components

Liquid gas generators (LGG) are additional firing units in the power system of liquid rocket engines (LPRE). The LGG ensure the operation of the power units of the turbopump unit (TPU) of the engine by feeding combustion products (CP) to the turbine drive. The main criteria for the efficiency of the generator gas is the complex (RT)gg and the thermodynamic properties of the mixture, depending on temperature, pressure, the degree of excess of the oxidizer and the enthalpy of the fuel, attributed to the conditions of supply to the nozzles of the GG. Changing the parameters of the generator gas leads to a change in the turbine power parameters due to its effect on the adiabatic operation of the Lad turbine. Depending on the engine circuit under consideration, CP GG can perform work in other units and elements of the engine, as well as influence many parameters of the LPRE. Among the main ones can be noted: the power of the booster gas turbine of the booster turbopump unit (BTPU) in the case of the selection of the generator gas after the GG or turbogas after the main turbine; the temperature of heating the refrigerant in the heat exchanger introduced in the GG; specific impulse of a liquid rocket propulsion system (LRPS), depending on the quantity and properties of the turbogas entering the exhaust pipe of the engine (for the engine circuit without afterburning the generator gas); mixing in the combustion chamber (CC) due to afterburning of turbogas entering the engine chamber after the turbine (for the engine circuit with afterburning of generator gas); parameters of the firing wall of the engine in the case of using a high-temperature gas curtain by blowing generator gas into the supersonic part of the nozzle. For many pairs of fuel during combustion in GG, the nonequilibrium of combustion products is characteristic (especially in hydrocarbon fuels).Due to the fact that the combustion products (CP) during the combustion of an oxygen-hydrogen mixture, due to the simplicity of the reaction, have time to form while staying in the GG (i.e., the time of chemical equilibrium of the CP is less than or equal to the time of stay in the GG), their thermodynamic parameters can be reliably determined using programs that simulate chemical equilibrium reactions. In this article, the issue of obtaining reliable results of thermodynamic calculations of generator gas at low and high coefficients of oxidant excess is investigated. Verification of parameters obtained in the programs “Astra” and “Rocket Propulsion Analysis” with calculated values was carried out. The most suitable program for performing engineering calculations and modeling the thermodynamics of liquid gas generators has been determined.

Computational simulation-assisted template selection of magnetic MOFs molecularly imprinted materials applying the adsorption and detection of multiple fluoroquinolones

This study utilized computational simulation and surface molecular imprinting technology to develop a magnetic metal-organic framework molecularly imprinted polymer (Fe3O4@ZIF-8@SMIP) capable of selectively recognizing and detecting multiple fluoroquinolones (FQs). The Fe3O4@ZIF-8@SMIP material was synthesized using the “common” template-ofloxacin, identified by computational simulation, demonstrating notable adsorption capacity (88.61–212.93 mg g−1) and rapid mass-transfer features (equilibration time: 2–3 min) for all tested FQs, consistent with Langmuir adsorption model. Subsequently, this material was employed as a magnetic solid-phase-extraction adsorbent for adsorption and detection of multiple FQs by combining with high performance liquid chromatography. The developed method exhibited good linearity for various FQs within the concentration range of 0.1–500 μg L−1, with low limit of detection (0.0605–0.1529 μg L−1) and limit of quantitation (0.2017–0.5097 μg L−1). Satisfactory recoveries (88.38–103.44%) were obtained when applied to spiked food samples, demonstrating the substantial potential of this Fe3O4@ZIF-8@SMIP material for rapid enrichment and identification for multiple FQs residues.

Adsorption of terbium (III) on DGA and LN resins: Thermodynamics, isotherms, and kinetics

Two commercially available extraction chromatography (EXC) resins containing N,N,N’,N’-tetra-n-octyldiglycolamide (DGA Resin, Normal, 50 – 100 μm) and Bis(2-ethylhexyl) phosphate (LN Resin, 100 – 150 μm) were used as adsorbents to study fundamental adsorption properties such as thermodynamic values, equilibrium isotherms, and kinetic uptake models for terbium(III) adsorption. Weight distribution ratios (Dw) for terbium on DGA and LN resins were measured using a [160Tb]Tb3+radiometric tracer in nitric acid as a function of acidity, temperature, initial analyte concentration, and equilibrium time. The Dw values showed increasing binding affinity for DGA resin at high nitric acid concentrations and decreasing binding affinity for LN resins. Thermodynamic studies for DGA and LN resins revealed that the Gibbs free energy (ΔG) increased consistently with temperature. To model equilibrium data, increasingly higher parameter equilibrium isotherm models (Henry (1) < Langmuir, Freundlich (2) < Redlich-Peterson (3) < Fritz-Schluender (4)) were compared on their root mean squared errors (RMSE) and adjusted determination coefficients to determine the most applicable model. In all cases, the empirical four-parameter Fritz-Schluender isotherm demonstrated a superior fit. Similar comparisons for reaction-based kinetic models (Pseudo-first-order < Pseudo-second-order < Pseudo-n-order) revealed that the higher-order PNO model yielded a superior fit of kinetic data for both resins. However, in some cases, adsorption isotherms and kinetic models could also be modeled by a lower-order model with minimal change in error parameters. Weber-Morris plots revealed that two linear sections are observed for each resin, where the first linear segment is attributed to fast (film diffusion) adsorption of terbium, followed by slower intraparticle diffusion of terbium through the pores as the rate-limiting step. Based on the Weber-Morris plot, both film and intraparticle diffusion are involved in controlling the kinetic rate of adsorption for DGA and LN resins.

Reversible Hydrophobic Deep Eutectic Solvent-Based Uranyl-Sensing Optode Film in Aqueous Streams: Color Transformation and Reusability.

A hydrophobic deep eutectic solvent (HDES)-based optode was designed for the preconcentration and determination of the UO22+ ion in aqueous media using spectroscopic techniques [energy-dispersive X-ray fluorescence (EDXRF) and solid-state absorption]. The optode was developed by incorporation of HDES (tri-n-octyl phosphine oxide and decanoic acid in an equimolar ratio), tri-(2-ethylhexyl) phosphate, and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol into a cellulose triacetate matrix. Characterization studies were carried out using different techniques to understand the roles of HDES as a plasticizer, UO22+ extractant, and Br-PADAP immobilizer. Uptake studies revealed that the optimal pH was 3 and sorption followed the type II adsorption isotherm. Uranium in the U-sorbed optode can be directly analyzed over a large concentration range of 0.021 × 10-3-2.1 × 10-3 Mol L-1 using EDXRF. The optode film exhibited a linear dynamic range of 0.84 × 10-6-84 × 10-6 Mol L-1 for uranium, with a lowest limit of detection of 0.084 × 10-6 Mol L-1 by colorimetric analysis. This optode-based method was employed for seawater analysis for its UO22+ concentration without any matrix separation, and the concentration was found to be 1.30 ± 0.06 × 10-8 Mol L-1. The optode exhibited better selectivity for UO22+ in the presence of various cations including Sr2+ and Cs+ in an aqueous medium. Compared to other prevailing optical sensors, this optode performed better in terms of key factors like pH, equilibration time, reusability, and detection limit.

Optimization of Batch Adsorption Study Parameters of Acid Dyes onto Spent Brewery Grains

The exploration of economical and nature friendly adsorbents for dye elimination from effluent is a promising area of research, driven by the need for sustainable and economically viable solutions. This work deals with the adsorption features of Acid Blue 25 (AB25) and Acid Green 25 (AG25) dyes from aqueous solutions using spent brewery grains (SBG). After brewing process, the obtained residue consists of spent grains. Optimum conditions for AB25 &amp; AG25 removal were found to be at pH 2, adsorbent dosage as 0.8 and 1 g/L of solution respectively and equilibrium time was found to be 60 mins. In order to adjudicate the adsorption process, analysis was carried out with kinetic and isothermal two parameter and three parameter models. The results were discovered to fit most with the pseudo-second-order (R2 = 0.990) for the kinetics and the Langmuir isotherm (R2 = 0.993) for the adsorption isotherms. The isotherms and kinetics verified that SBG had a high value of adsorption capacity. Experiment results pointed out SBG is one of the best adsorbent that eco-friendly, economical, readily accessible, and efficient on the removal of AB25 and AG25 dyes from aqueous solution.

In-Situ Hydrothermal Fabrication of ZnO-Loaded GAC Nanocomposite for Efficient Rhodamine B Dye Removal via Synergistic Photocatalytic and Adsorptive Performance.

In this work, zinc oxide (ZnO)/granular activated carbon (GAC) composites at different ZnO concentrations (0.25M-ZnO@GAC, 0.5M-ZnO@GAC, and 0.75M-ZnO@GAC) were prepared by an in-situ hydrothermal method and demonstrated synergistic photocatalytic degradation and adsorption of rhodamine B (RhB). The thermal stability, morphological structure, elemental composition, crystallographic structure, and textural properties of developed catalysts were characterized by thermal gravimetric analysis (TGA/DTG), scanning electron microscopy equipped with energy dispersive-x-ray (SEM-EDS), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) analysis. The successful loading of ZnO onto GAC was confirmed by SEM-EDS and XRD analysis. The BET surface areas of GAC, 0.25M-ZnO@GAC, 0.5M-ZnO@GAC, and 0.75M-ZnO@GAC were 474 m2/g, 450 m2/g, 453 m2/g, and 421 m2/g, respectively. The decrease in GAC could be attributed to the successful loading of ZnO on the GAC surface. Notably, 0.5M-ZnO@GAC exhibited the best photocatalytic degradation efficiency of 82% and 97% under UV-A and UV-C light over 120 min, attributed to improved crystallinity and visible light absorption. The photocatalytic degradation parameters revealed that lowering the RhB concentration and raising the catalyst dosage and pH beyond the point of zero charge (PZC) would favor the RhB degradation. Photocatalytic reusability was demonstrated over five cycles. Scavenger tests revealed that the hydroxyl radicals (•OH), superoxide radicals (O2-•), and photoinduced hole (h+) radicals play a major role during the RhB degradation process. Based on the TOC results, the RhB mineralization efficiency of 79.1% was achieved by 0.5M-ZnO@GAC. Additionally, GAC exhibited a strong adsorptive performance towards RhB, with adsorption capacity and the RhB removal of 487.1 mg/g and 99.5% achieved within 90 min of equilibrium time. The adsorption characteristics were best described by pseudo-second-order kinetics, suggesting chemical adsorption. This research offers a new strategy for the development of effective photocatalyst materials with potential for wider wastewater treatment applications.

Composite flat-sheet membrane adsorbent of Li2TiO3-Ethylene-co-vinyl alcohol (LTO-EVAL) for lithium extraction

Composite bead adsorbents have been prevalent for the extraction of Li+ from brines. However, adsorbent beads generally demonstrate declining adsorption capacity and require extended equilibrium time when used repeatedly in absorption/desorption cycles. To overcome this challenge, a novel composite flat-sheet membrane adsorbent based on ethylene-co-vinyl alcohol (EVAL) and Li2TiO3 (LTO) is reported herein for highly efficient Li+ extraction from a geothermal brine. At an optimal LTO loading and membrane thickness, the resulting LTO-EVAL membrane was characterized by a large open macrovoid structure for fast ion transport, a fast adsorption rate that reached equilibrium in 0.5 h, and a high capacity of 96 % of that of the powder. The new membrane adsorbent showed adsorption behavior consistent with the Langmuir model and pseudo-second-order kinetic model. For a geothermal brine with a low lithium concentration, the LTO-EVAL membrane showed stable performance in 13 rapid adsorption/desorption cycles, with adsorption capacity at an average adsorption capacity of 7.3 mg/g and a 70 % adsorption efficiency. The average dissolution rate of Ti4+ was below 0.6 % in each cycle. The structure of the adsorbent material showed no discernable changes in chemical structure as confirmed by XRD and SEM results. With the improved extraction efficiency, the reusable membrane adsorbents would be economically viable in the long run and could potentially serve as the next generation of scalable Li+ adsorption material for brines. Further utilization of membrane adsorbent would lead to new design of adsorption modules and systems with reduced footprint. We need to further optimize the stability of the membrane adsorbents so that loss of Li2TiO3 remain at low level to reduce the lost for lithium extraction from the geothermal brine.

Al(III)-based MOF for tetracycline removal from water: Adsorption performance and mechanism

The high concentration of pharmaceuticals in water systems can harm the ecosystem and human health. Tetracycline (TC) is a human and veterinary antibiotic widely used for bacterial infections. The excessive use of TC has resulted in a risk to health and the environment since TC has been found in various water ecosystems. Then, this study focuses on effectively removing tetracycline from water solutions using an Al(III)-based MOF CYCU-3. The material showed high adsorption in the pH range of 4–9 with an equilibrium time of 120 min and outstanding cyclability. The maximum adsorption capacity was 428.1 mg g−1. The experimental data were fitted into Pseudo-Second Order (PSO) and Temkin models, suggesting physicochemical interactions. The thermodynamic study proved the exothermic nature of the process. The adsorption mechanism was proposed based on the experimental analysis, Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and theoretical calculations. It was proposed that cation-π, π-π interactions, and hydrogen bonding played the main role in adsorption. CYCU-3 displays higher adsorption capacity compared with some representative porous materials. Therefore, CYCU-3 can be considered a suitable adsorbent for the treatment of water contaminated with pharmaceuticals.

Experimental study of methylene blue adsorption from aqueous solutions onto natural Algerian goethite

ABSTRACT The objective of this work is to study and model the methylene blue (MB) sorption, from aqueous solutions by goethite. The equilibrium time was reached during 10 min of agitation with 26.21 ℅ efficiency. MB removal efficiency is improved with an increased absorbent dose (0.5–08 g/L) for an initial 10 mg/L concentration. Treatment efficiency decreases with the increase of initial MB concentration (2–100 mg/L). The best adsorption yields were obtained in basic media. MB sorption kinetics via goethite leads to several results as to mechanisms that govern kinetics and isotherms equilibrium: Blanchard's model provides a better fit of the experimental results compared to Lagergren's model. Thus, the MB sorption kinetics is described by the pseudo-second order. Particle diffusion is involved in the MB removal mechanism, but it is not the only limiting step and the Boyd model application confirms that diffusion in the pores is the limiting step of the MB sorption process. The Elovich model is well verified and translated probably the existence of chemical-type interactions between MB and goethite. The study of MB adsorption isotherms showed that Freundlich, Temkin, and Elovich models are the best adapted than the Langmuir model. Finally, we can assess that goethite can be an interesting natural adsorbent for MB elimination from polluted waters in basic environments.

Study on VOCs of Fishmeal during Storage Based on HS-SPME-GC-MS.

Fishmeal is widely used in the feed industry as the main protein material. The freshness grade directly affects the quality of the fishmeal. During the storage of fishmeal, the odor would change accordingly as the freshness grades decreased. To study the characteristic volatile organic compounds (VOCs) of fishmeal, stored at 25 °C and 80%RH with different freshness grades, headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS) was used to analyze. The single-factor test was chosen for 50/30 μm divinylbenzene/carboxe/polydimethylsiloxane (DVB/CAR/PDMS) fiber. The equilibration time of 24 min, the extraction time of 60 min, the extraction temperature of 87 °C, and the addition of a saturated saline volume of 4 mL were determined by Box-Behnken design. There were 15 common VOCs detected during storage, the relative contents of acids increased significantly, ketones, aldehydes, esters, and nitrogen-containing compounds increased, and aromatic compounds and alcohols decreased. Combined with freshness indexes, volatile base nitrogen (VBN) and acid value (AV), hexadecanoic acid, tetradecanoic acid, methyl (Z)-N-hydroxybenzenecarboximidate, (Z)-hexadec-9-enoic acid, 6-ethoxy-2,2,4-trimethyl-3,4-dihydro-1H-quinoline, octadecanal, and [(Z)-octadec-9-enyl] acetate were determined as the characteristic VOCs based on the PLS-DA model. This study may provide data support for the development of fishmeal freshness-detecting instruments.

A novel dual channel six-membered spirorhodamine for Cu2+ and ClO- depending on solvent and application in real samples and bioimaging

To reveal the solvent dependence of six-membered rhodamine spirocycles (SMRS), a new probe SM-RB has been synthesized and investigated the spectral properties in different solvents upon the addition of various metal ions and anions. SM-RB exhibited high selectivity for Cu2+ in CH3CN/HEPES and ClO- in C2H5OH/HEPES solutions, respectively. The spectral changes of SM-RB in the presence of ClO- in C2H5OH/HEPES solution were much less than that of Cu2+ in CH3CN/HEPES. The detection limit of Cu2+ was as low as 36 nM (fl) in CH3CN/HEPES. The kinetic equilibration time (8 s) indicated that the two solvent systems did not delay the spectral response speed to Cu2+ and ClO-. Solvent systems influenced the pKa value of SM-RB in CH3CN/HEPES and C2H5OH/HEPES. The pKa value of SM-RB was 4.34 (±0.7) (Abs) and 4.75 (±0.14) (Fl) in CH3CN/H2O, but can’t be exactly calculated by pH titration in C2H5OH/H2O. The reversibility and Job plot of SM-RB were investigated to propose the response mechanism of SM-RB with Cu2+ and ClO- in the two solvent systems. Finally, SM-RB not only can be used for the quantitative detection of copper ions in grape peel, but also can real-time monitor the fluctuation of Cu2+ in lysosomal pools.

Efficient removal of perfluorooctanoic acid using fluorinated ionic liquids and granular activated carbon

Perfluoroalkylated and polyfluoroalkylated substances (PFAS) are persistent and bioaccumulative compounds in the environment and the human body. Their presence in high concentrations brings devastating consequences to health. Nowadays, there is an urgent need to develop efficient and sustainable processes that mitigate the damage caused by PFAS to improve the life quality of individuals. In the present work, perfluorooctanoic acid (PFOA) extraction properties with fluorinated ionic liquids (FILs) in aqueous media were evaluated for the first time. The most promising FIL is [P44414] [C4F9SO3] obtaining uptake capacities up to 280 mg·g−1 in 72 h. To verify if this performance is competitive for the best materials used so far in the literature for PFAS removal, adsorption processes were carried out with granular activated carbon (GAC) obtaining adsorption capacities up to 666 mg·g−1 (best fitted with the pseudo-second-order kinetic model) with an equilibrium time of 48 h. Equilibrium assays showed maximum uptake capacities around 500 mg.g−1, and multilayer adsorption due to the best fit to the Freundlich model. Both materials (FILs and GAC1240W) can open new paths in PFAS removal processes from aqueous solutions. Taking advantage of the properties of each one of these compounds, new, more efficient, and sustainable processes can be optimised in the future.