Desorption Tests Research Articles

A Phosphorylated Dendrimer-Supported Biomass-Derived Magnetic Nanoparticle Adsorbent for Efficient Uranium Removal.

A novel biomass-based magnetic nanoparticle (Fe3O4-P-CMC/PAMAM) was synthesized by crosslinking carboxymethyl chitosan (CMC) and poly(amidoamine) (PAMAM), followed by phosphorylation with the incorporation of magnetic ferric oxide nanoparticles. The characterization results verified the successful functionalization and structural integrity of the adsorbents with a surface area of ca. 43 m2/g. Batch adsorption experiments revealed that the adsorbent exhibited a maximum adsorption capacity of 1513.47 mg·g-1 for U(VI) at pH 5.5 and 298.15 K, with Fe3O4-P-CMC/G1.5-2 showing the highest affinity among the series. The adsorption kinetics adhered to a pseudo-second-order model (R2 = 0.99, qe,exp = 463.81 mg·g-1, k2 = 2.15×10-2 g·mg-1·min-1), indicating a chemically driven process. Thermodynamic analysis suggested that the adsorption was endothermic and spontaneous (ΔH° = 14.71 kJ·mol-1, ΔG° = -50.63 kJ·mol-1, 298. 15 K), with increasing adsorption capacity at higher temperatures. The adsorbent demonstrated significant selectivity for U(VI) in the presence of competing cations, with Fe3O4-P-CMC/G1.5-2 showing a high selectivity coefficient. The performed desorption and reusability tests indicated that the adsorbent could be effectively regenerated using 1M HCl, maintaining its adsorption capacity after five cycles. XPS analysis highlighted the role of phosphonate and amino groups in the complexation with uranyl ions, and validated the existence of bimodal U4f peaks at 380.1 eV and 390.1 eV belonging to U 4f7/2 and U 4f5/2. The results of this study underscore the promise of the developed adsorbent as an effective and selective material for the treatment of uranium-contaminated wastewater.

Visible-light-driven photocatalytic degradation of tetracycline using citric acid and lemon juice-derived carbon quantum dots incorporated TiO2 nanocomposites

Tetracyclines (TC) are consistently found in aquatic ecosystems, contributing to the development and spread of antibiotic resistance genes and antibiotic-resistant bacteria. This poses adverse effects on aquatic organisms and humans, emphasizing the need for an effective approach to remove these contaminants. TiO2-based photocatalysts hold great potential for efficiently removing TC from water. This study aimed to synthesize TiO2 nanocomposites incorporated with carbon quantum dots (CQDs) derived from both artificial and natural sources. The nanocomposites were characterized using X-ray diffraction, electron microscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and N2 adsorption–desorption test. The incorporation of CQDs into TiO2 resulted in the reduction of the band gap energy from 3.17 eV in pure TiO2 to 3.10 eV, broadening the light absorption range, and improving the charge carrier transfer efficiency. Continuously generated electrons led to the production of reactive oxygen species, predominantly •O2–, contributing to TC degradation. Holes and •OH radicals also played a significant role in TC degradation. As a result, CQDs/TiO2 nanocomposites exhibited 91.5 % TC removal under visible light irradiation (λ ≥ 400 nm) for 120 min at pH 8. The active sites of TC molecules were determined through density functional theory calculations, and the corresponding degradation pathways of TC were proposed using liquid chromatography-mass spectrometry. Furthermore, this study attempted to synthesize CQDs using lemon juice, showcasing the potential of these eco-friendly photocatalysts for TC removal. The visible-light-driven degradation of TC by the natural-source-derived CQDs/TiO2 nanocomposites demonstrated their applicability in water treatment to effectively address current environmental challenges.

Adsorption, kinetic, and thermodynamic studies of natural curcumin dye on cotton and polyamide fabric and the liberation of its active principle

AbstractThe increasing emphasis on environmental sustainability and the demand for eco‐friendly practices have led to a surge in interest in natural products, particularly natural dyes, across industries, including textiles. Curcumin, extracted from the turmeric plant, has gained widespread application not only for its vibrant colour characteristics but also for numerous therapeutic properties, serving as an antioxidant, anti‐inflammatory agent, and promoting wound‐healing effects. This study aims to understand the physical and chemical phenomena associated with the adsorption and desorption of turmeric extract and its active principles on cotton and polyamide fibres through mathematical models, with the goal of expanding textile applications. Dyeing experiments revealed adsorption equilibrium times of less than 25 min for both fibres, with the pseudo‐second‐order model providing the best fit for dyeing kinetics, suggesting control through the chemisorption process. The Freundlich model better suited cotton adsorption isotherms (R2 = 0.778), while the Langmuir model fit well for polyamide (R2 = 0.981). Thermodynamic parameters indicated non‐spontaneous interactions between curcumin and cotton, with an endothermic process, and an exothermic and spontaneous process for polyamide. Friction and water tests indicated greater colour resistance for polyamide, with grades exceeding 4. Desorption tests in 100% ethanol solution showed a total release of only 0.88% and 0.97% for polyamide and cotton, respectively, sustained for 12 h, fitting the Higuchi mathematical model, indicating a purely diffusive release process. These results demonstrate the potential of curcumin dye for achieving high dye exhaustion percentages in natural and synthetic fabrics and sustained release properties.

Alginate-derived solid-liquid hybrid structured adsorbent for CO2 capture

The development of highly stable structured solid amine adsorbent is crucial for the large-scale deployment of CO2 capture systems. Here, we report a structured solid amine adsorbent using the solid-liquid hybrid wrapping method, wherein a suspension of tetraethylenepentamine (TEPA) and ZSM-22 support is encapsulated within a calcium alginate film through freeze-drying. The textural properties of the structured adsorbents (SA@S/TX) were investigated using scanning electron microscopy, N2 adsorption-desorption, Fourier transform infrared spectroscopy, and thermal gravimetric analyzer. The CO2 adsorption capacity of SA@S/TX displayed an initial increase followed by a decrease with increasing TEPA loading, and the adsorption rate exhibited a similar trend according to the pseudo-first-order model. The maximum adsorption capacity and adsorption rate (k) were observed to be 2.22 mmol/g and 0.98 min−1 (under conditions of pure CO2, 1 atm and 25 °C), respectively, at a TEPA content of 0.5. In addition, SA@S/TX exhibited good regeneration stability with a low loss in capacity of 10.8 % during 30 cycle of CO2 adsorption–desorption tests, and high thermal stability with a low amine loss of 2.0 % under conditions of 100 °C and 12 h. These results demonstrate that the solid–liquid hybrid wrapping method effectively shapes the powdered adsorbent while significantly reducing TEPA volatilization, offering a possibility for the industrial applications of solid amine adsorbents.

Continuous-flow hydrogenation of cinnamaldehyde over catalysts derived from modified CoAl4 layered double hydroxides incorporating Mn, Ni, Cu and Zn ions

Series of CoxM1-xAl4 layered triple hydroxides, LTHs were prepared as catalyst precursors for hydrogenation of biomass compound cinnamaldehyde under flow and batch reaction conditions. To this end, we have successfully extended the eco-friendly family of Al-rich layered double hydroxides (LDHs) by synthesizing MnAl4-LDHs, furthermore Co3Al-, Co2Al-LDHs were also exploited. Both the magnetic Co-rich and Al-rich reduced forms behaved as robust, efficient and reusable catalysts with significantly different selectivities correlated with their acid-base properties. Al-rich solids showed increased acidity and lower basicity resulting in high hydrocinnamaldehyde selectivity (∼75 %), while the Co-rich catalysts attested enhanced hydrocinnamyl alcohol production (∼80 % selectivity) due to their low acidity and high basicity (mapped by NH3/CO2 temperature programmed desorption tests). Incorporation of Mn, Ni, Cu and Zn ions generally decreased the total acidity of Al-rich catalysts, while their Lewis basicity largely increased: the highest was found for Mn, resulting in activity similar to that of Co-rich catalysts.

Lead species formation on pure hemimorphite surface and its performance for subsequent sulfidization

Hemimorphite is important-supplementary resource for the commercial zinc production, but it easy loses into tailings due to extreme difficulty for its surface sulfidization. Adding active metal ions after sulfidization have been widely proposed for enhancing hemimorphite floatability, but its desired efficiency in flotation practice has not yet been completely achieved caused by the instability of sulfide layer. Whereas pre-adsorption of active metal ions to modify the hemimorphite surface has strong potential to make up for this shortcoming. Herein, the feasibility and appropriate environment of free Pb<sup>2+</sup> for modifying the pure hemimorphite surface was evaluated. Subsequently, the performance of Pb<sup>2+</sup> adsorption for enhancing sulfidization stability and floatability of hemimorphite were investigated. The X-ray photoelectron spectroscopy results indicated that the Pb<sup>2+</sup> adsorption on hemimorphite surface was achieved through the Pb ions displacement for Zn ions, and it was bond to oxygen-containing groups on hemimorphite surface. Such adsorption was strengthened with the increasing of solution pH, owing to the abundant Pb hydroxyl species precipitated on mineral under alkaline conditions, in term of the results of visual MINTEQ modeling and time-of-flight secondary-ion mass spectrometry. In addition, the X-ray photoelectron spectroscopy results showed dominant Pb hydroxyl species further reacted with sulfur during subsequent sulfidization to generate much more S species than that of without Pb<sup>2+</sup> pre-modification. Meanwhile, such sulfide layer composed by Pb<sup>2+</sup> on the mineral surface presented much higher stability than Zn-S species, which was verified via adsorption and desorption tests. As a result, the sulfidization and flotation recovery of hemimorphite increased after Pb<sup>2+</sup> pre-adsorption.

Dual-bioinspired and ultra-flexible photothermal eutectogels for highly efficient passive anti-freezing

Icing and frosting always cause troubles in present-day human activities, appealing for effective anti-freezing strategies to break through the bottleneck. Inspired by “predominant metabolites in the body fluid of cold-tolerant animals” and “poikilotherms that increase body temperature by absorbing solar energy”, natural deep eutectic solvents (NADES) and carbon nanotubes (CNTs) were incorporated within calcium alginate (CA) backbone to fabricate dual-bioinspired and ultra-flexible photothermal eutectogels (CNTs/NADES@CA). Normal CNTs (nCNTs) and hydroxylated CNTs (hCNTs) were used to investigate the effects of hydrogen-bonding networks of NADES on the dispersal/aggregation behaviours of nCNTs/hCNTs. Molecular dynamics (MD) simulation proved that hCNTs could form intense hydrogen-bonding interactions with NADES and disperse more uniformly, ultimately contributing to better mechanical properties. Spectral characteristics covering solar absorption and infrared emissivity showed that higher nanofiller loading could cause increased infrared emissivity, leading to more thermal energy loss during photothermal conversion. Besides, moisture absorption–desorption tests further confirmed the excellent function reproducibility and sustainability of the materials. One of the hCNTs-based eutectogels (4%-hCNTs) behaving the best in photothermal conversion was selected for anti-freezing tests concerning anti-frosting, anti-icing, and deicing capacities, announcing that the CNTs/NADES@CA could be highly efficient for passive anti-freezing. This study proposed a highly efficient nanofiller dispersion strategy enabled by NADES to fabricate ultra-flexible photothermal eutectogel by a physically simple method, and it is hoped that this work could open up new avenues for bioinspired materials and attract more concerns for the proposed dual-bioinspired anti-freezing strategy.

An experimental study on high strength self-compacting concrete inclusion of zeolite and silica fume as a potential alternative sustainable cementitious materials

One of the major sources of carbon dioxide and other greenhouse gases around the world is the cement industry. They make up 6–8 % of global warming. Therefore, by conducting this experiment, we may examine the possibility of replacing cement with different cementitious materials which include zeolite,silica fume and fly ash. These mineral additives will lessen the need for cement while enhancing the properties of the concrete that has just been hardened and also in fresh state. The objective of this experiment is to explore the impact of zeolite and silica fume on the physical and durability qualitiesof high strength, self-compacting concrete utilising nano silica that has been optimised. In the course of this study, various concrete mixtures were cast with zeolite and silica fume substituted for cement in varying amounts, and there was also a control mix for reference. These additives arereplacedcement in multiples of 5 up to 20 %. The preferred dosage as 2 % Nano silica is substituted as a regular mineral additive in all mixtures. Workability tests on the fresh qualities of concrete mixtures are conducted and the EFNARC stipulations are met by these experimental findings. All the concrete mixes' parameters, including strengths like splitting tensile and compressive were identified. Tests such as the Rapid chloride permeability test, the abrasion test, water absorption and desorption test were used to evaluate the concrete's durability.

Functionalized biochar from waste as a slow-release nutrient source: Application on tomato plants

Licorice processing waste was pyrolyzed at different temperatures (500 and 700 °C) to obtain biochar (BC500 and BC700) for use as a slow-release fertilizer on Solanum lycopersicum. The materials were characterized through BET analysis, SEM, elemental analysis, pHzc, and pyrolysis temperature effect was evaluated. The biochars were functionalized by the impregnation method to enrich them with nitrogen, phosphorus, and potassium (NPK), and desorption tests were performed in aqueous solution at different pHs (5 and 7). The pseudo-second-order model described well the release of all 3 macronutrients tested, BC500 was found to have slower release kinetics due to smaller pore size, reaching adsorption/desorption equilibrium after 14 days, compared with 10 for BC700, Kdes were lower in all 3 cases and NPK content was higher, initial pH did not change the release kinetics. BC500 was selected as an agricultural soil conditioner by testing at both different dosages of BC (0–25 %) and different NPK ratios (3:1:4 and 4:1:3). The treatment significance was evaluated. The best treatment resulted in BC dosage of 25 % nutrient ratio 4:1:3 which increased, compared to the control, total chlorophyll content (+38 %) and carotenoids (+15 %).

Study on desorption characteristics of water vapor in fly ash concrete materials

In this paper, water vapor desorption tests are carried out on water-saturated concrete materials with different water-binder ratios and fly ash content. The desorption parameters are analyzed using the adsorption curve analysis method, which enables the acquisition of desorption characteristics for concrete materials. By utilizing the desorption isothermal curve, the desorption rate is calculated and further analysis is conducted on the influence of water-binder ratio and fly ash content on this rate. The results indicate that the desorption and activation energy for water vapor desorption in concrete materials is higher than the adsorption energy at the first layer, suggesting that removing water vapor from inner pore walls is more challenging than its adsorption. The amount of water vapor released from concrete materials follows a power function over time, as does the rate of desorption. Under conditions of relatively low ambient humidity, an increase in the water-binder ratio leads to a decrease in the rate of desorption. Conversely, under relatively high ambient humidity, an increase in the water-binder ratio results in an increased rate of desorption.

Probing the differences in CO2 adsorption/desorption behaviors of solid amine sorbents in fixed and fluidized beds

Circulating fluidized bed temperature swing adsorption (CFB-TSA) CO2 capture process using solid amine sorbents has become a widely recognized solution to reduce stationary sources CO2 emissions. The successful design and operation of the adsorber and desorber requires much information on the CO2 adsorption and desorption behaviors of the sorbents in fluidized bed reactors. However, among the existing studies, little attention has been paid to desorption performance, which is equally important as adsorption performance. And almost all of them were conducted in TGAs or fixed beds, the lack of research in fluidized beds making it difficult to guide the design of industrial fluidized bed reactors. In addition, the systematic comparison of the above-mentioned adsorption/desorption behaviors and bed hydrodynamics (e.g. pressure drops) in fixed and fluidized beds can help provide theoretical support for the optimization of adsorbers, desorbers and coolers, which has not been reported yet. Therefore, we for the first time investigated the CO2 adsorption/desorption behaviors as well as hydrodynamics in both fluidized and fixed beds using a solid amine sorbent in a temperature swing adsorption (TSA) experimental rig. The results show that the sorbent exhibits faster adsorption and desorption kinetics in fluidized beds than those in fixed beds, as reflected by the fitted parameters of the Avrami kinetic model and the change of bed temperature during adsorption and desorption tests. And the bed pressure drops in fluidized beds are also much lower than that in fixed beds, especially at high superficial gas velocities and high sorbent loadings. By further discussion, a fluidized bed can also achieve lower equipment investment and less sorbent loading compared to multiple fixed beds in parallel. This study demonstrates the advantages of fluidized beds over fixed beds in large-scale TSA units in view of higher reactor efficiency, lower energy consumption and equipment investment.

Photocatalytic oxidation degradability of ammonia–nitrogen and Ni/Co ammonia complexes in ternary precursor wastewater by constructing MoS2/g-C3N4 heterojunction: Performance and mechanism

In this study, MoS2/g-C3N4 heterojunction photocatalysts were fabricated in order to treat ammonia–nitrogen wastewater resulting from the production of ternary cathode material precursors used in the manufacture of lithium-ion batteries. The catalysts were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), N2 adsorption–desorption test, UV–Vis diffuse reflectance spectra (UV–Vis DRS), Fourier-transform infrared spectroscopy (FT-IR Nicolet 6700), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The catalytic efficiency of the catalysts on ammonia–nitrogen and Ni/Co ammonia complexes in the wastewater was investigated by varying MoS2 doping, catalyst dose, adsorption duration, and photocatalysis duration. The results showed 2.0 g/L of MoS2/g-C3N4-1 wt% (photocatalyst with a content of 1 wt% MoS2) has the best photocatalytic efficiency. A degradation efficiency of 87.52 % for ammonia–nitrogen, 98.34 % for nickel and 97.80 % for cobalt was reached after one hour of dark adsorption and four hours of illumination. EDS and XPS analysis revealed that Ni2+/Ni3+ and Co2+/Co3+ were adsorbed from the solution onto the catalyst surface, and that NH4+/NH3 was converted into NO3− and N2.

Unraveling the deactivation mechanism of Co-LiH composite catalyst for ammonia synthesis at milder conditions

An efficient ammonia synthesis catalyst that operates under mild conditions has been a long-cherished goal in heterogeneous catalysis. The challenges associated with low-temperature ammonia synthesis arise from both the activation of inert N2 molecules and the presence of scaling relations between reactant dissociation and intermediate adsorption energies. Transition metals-metal hydride (TM-MH) composite catalysts have shown promise to overcome these challenges as both TM and MH actively participate in the reaction, enabling improved ammonia synthesis rates at lower temperatures (150 ºC). Considering this prospect, two types of Co-LiH catalyst were synthesized by ball-milling of precursors (CoCl2 and LiH- denoted as Co-LiH(rxn)) and pure components (Co and LiH- denoted as Co-LiH(pur)), and their catalytic activity was evaluated at several reaction conditions to investigate the stability for long-term operation. Co-LiH(rxn) was found to deactivate in less than 150 h whereas Co-LiH(pur) displayed a continuous production although the synthesis rate was 3 times lower than the former. Structural characterization techniques, such as XRD, SEM, and TEM were used, and it was found that Co metal in the FCC phase was primarily sintered due to its small particle size in the fresh catalyst. Temperature-programmed desorption (TPD) test on the spent Co-LiH(rxn) catalyst also displayed an ammonia release profile similar to that of LiNH2 decomposition, which confirms the presence of ammonia in the spent catalyst structure. Hence, another major finding is speculated that irreversible ammonia absorption by LiH at the target ammonia reaction conditions contributes to the deactivation of the catalyst and the formation of intermediate compounds that are required for continuous ammonia generation in this composite catalyst.

Effects of Polyether Amine Canopy Structure on Heavy Metal Ions Adsorption of Magnetic Solvent-Free Nanofluids.

Three Fe3O4 magnetic solvent-free nanofluids with different amine-based coronal layer structures are synthesized and characterized by using magnetic Fe3O4 as the core, silane coupling agent as the corona, and polyether amines with different graft densities and chain lengths as the canopy. The concentration of heavy metal ions after adsorption is measured by atomic absorption spectrometry (AAS) to study the effect of Fe3O4 magnetic solvent-free nanofluids on the adsorption performance of the heavy metal ions lead (Pb(II)) and copper (Cu(II)) in water. The adsorption of Fe3O4 magnetic solvent-free nanofluid was explored by changing external condition factors such as adsorption contact time and pH. Additionally, the adsorption model is established. The magnetic solvent-free nanofluid is separated from water by applying an external magnetic field to the system, and desorption and cyclic adsorption tests are carried out. Based on the adsorption mechanism, the structure design of Fe3O4 magnetic solvent-free nanofluid was optimized to achieve optimal adsorption performance.

Hierarchical aerogels based on cellulose nanofibers and long-chain polymers for enhancing oil–water separation efficiency

The hydrophobic chain length of biomass-based aerogels used for oil–water separation was evaluated as a major parameter influencing the aerogels’ hydrophobicity. The properties of the porous structure were enhanced by the hierarchical assembly of the aerogels with biopolymeric structural units and polymer mineralization. The cellulose network was strengthened through silanization, and the nanocellulose network was further enhanced through coating with mineralizers containing long-chain hydrophobic molecules. Interfacial engineering was employed to establish multiscale interactions through the freeze-drying-induced modification of cellulose nanofibers and mineralized coatings of long-chain alkyl polymers. The resulting hierarchically structured aerogel exhibits low density (11.4 kg/m3), excellent mechanical compression properties across a wide temperature range (capable of enduring 100 cycles of compression), high porosity (99.2%), superhydrophobicity (152°), and recyclability. It maintains a 57.9% adsorption rate even after 40 adsorption–desorption tests, while also preserving its shape integrity. Moreover, it can be recycled and reused. At a temperature of 700 °C, the mass loss was only 44.47%, with excellent thermal stability. The aerogel can reduce oil pollutants in the ocean by adsorption, recover oil resources, and protect the natural environment. The assembly and optimization of nanofibrous matrix interfaces through the mineralization of long-chain polymers enhanced the performance of functionalized cellulose-based aerogels.

Uncovering the potential of MSC CT-350 for CO2/CH4 separation toward the optimization of a Pressure Swing Adsorption process for biogas upgrading

A laboratory-scale fixed-bed column is employed to study the dynamic behavior of the carbon molecular sieve MSC CT-350 for CO2/CH4 separation. Breakthrough adsorption tests in single-component systems are carried out at different pressures (1, 3, 5, 6.5 and 8 bar) and constant temperature (20 °C). Moreover, an additional test is conducted with a 40% CO2/60% CH4 binary mixture at 3 bar. Desorption tests are performed by varying the purge-to-feed ratio (P/F) at 50%, 30% and 20%, optionally using a vacuum pump. Experimental results show that MSC CT-350 has a good CO2 adsorption capacity for each pressure, considerably higher than CH4. In the binary test, very slight differences are experimentally found in the adsorption kinetics and equilibrium adsorption capacity with respect to single-compound tests, which results equal to 2.16 mol kg−1 for CO2 and 0.302 mol kg−1 for CH4 at 3 bar, compared with 2.29 mol kg−1 for CO2 and 0.262 mol kg−1 for CH4 for the single-compoound counterparts. The time required for a complete regeneration decreases with the increase in purge flowrate and with the simultaneous use of the vacuum pump. Finally, CO2 adsorption is a reversible process as the CO2 adsorption capacity of the adsorbent is not significantly reduced when utilized in subsequent adsorption-desorption cycles.

Smart Sorption: Novel applications of cellulosic nanomaterials for selective critical metal recovery from black mass leachates through multibatch processes

Selective critical metal recovery from black mass leachates (BML) is a great challenge for the Li-ion batteries recycling sector. This paper shows the potential of nanocellulose products as green adsorbents for a selective recovery of critical metals through multibatch sorption processes. Cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs) of 0.4 and 1.5 meq/g cationic demand, respectively, have been produced and used as biosorbents. Metal leaching from non-pyrolyzed black mass with HCl presented the highest critical metal extraction yield, obtaining up to 10 g/L of Co and more than 1 g/L of Cu, Mn and Ni. The adsorbents were tested under different dosages and pH conditions for the treatment of both synthetic multimetal solution (MMS), with Mn, Cu, Co, and Ni, and real BML, through a multiple step batch treatment to increase the selectivity towards each critical metal. For MMS treatments, the lowest pH (1–2) conditions are favorable for Co separation, reaching 135 g/g, while higher pH values (4–5) are better to recover Cu and Ni. Selectivity indexes between metals could reached values above 40 for the optimal conditions. For the treatment of BML, pH around 3 enhanced the selectivity of Al and pH of 5 of the Li. In this case, metal recoveries were higher than 30 g/g. When CNCs were used, more than 4 g/g of Co was adsorbed, recovering more than 99 % of the Co present in the waste. 99 % of Co purity was obtained at the optimal Co selective recovery conditions. Although the studied critical metals were strongly sorbed onto the nanocelluloses, a solution with a concentration of 2.5–5 g/L of these metals could be extracted from desorption tests.

Fabrication of Fe-CoS2@N-doped C electrode for highly efficient and durable electrosorption of Yb(III) from aqueous solutions

In this study, the novel Fe-doped CoS2@nitrogen-doped carbon (Fe-CoS2@NC) composites were manufactured and investigated as the capacitive deionization (CDI) electrode materials for electrosorption of Yb(III). The as-prepared materials were characterized with X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, N2 adsorption–desorption test with Brunauer-Emmett-Teller method, Raman spectroscopy, and X-ray photoelectron spectroscopy. The electrochemical tests, including cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy, revealed that Fe-CoS2@NC exhibited the better electrochemical performance with a specific capacitance of 58.41 F g−1 than Fe-CoS2@0.5NC and Fe-CoS2. The electrosorption results demonstrated that Fe-CoS2@NC possessed the Yb(III) uptake of 129.4 mg·g−1 within 60 min at a voltage of 1.2 V and a flow rate of 20 mL·min−1. After five successive sorption–desorption cycles, the electrosorption efficiency of Fe-CoS2@NC remained at 98 %, exhibiting the robust durability for future industrial application. Furthermore, Fe-CoS2@NC also showed the favorable electrosorption performance towards various rare earth ions, especially for heavy rare earth ions. The mechanism analysis indicated that the impressive electrosorption performance is attributed to the synergistic contribution by the electric double layers of carbonaceous matrix and the pseudo-capacitance that induced by the redox reactions of Fe atom.

Dual p-n Z-scheme heterostructure boosted superior photoreduction CO2 to CO, CH4 and C2H4 in In2S3/MnO2/BiOCl photocatalyst

The creation of a Z-scheme heterojunction is a sophisticated strategy to enhance photocatalytic efficiency. In our study, we synthesized an In2S3/MnO2/BiOCl dual Z-scheme heterostructure by growing BiOCl nanoplates on the sheets of In2S3 nanoflowers, situated on the surface of MnO2 nanowires. This synthesis involved a combination of hydrothermal and solution combustion methods. Experiments and density functional theory (DFT) calculations demonstrated that the In2S3/MnO2/BiOCl composite exhibited notable photo reduction performance and photocatalytic stability. This was attributed to the pivotal roles of BiOCl and MnO2 in the composite, acting as auxiliaries to enhance the electronic structure and facilitate the adsorption/activation capacity of CO2 and H2O. The yield rates of CO, CH4, and C2H4 over In2S3/MnO2/BiOCl as the catalyst were 3.94, 5.5, and 3.64 times higher than those of pure In2S3, respectively. Photoelectrochemical analysis revealed that the dual Z-scheme heterostructure, with its oxygen vacancies and large surface area, enhanced CO2 absorption and active sites on the nanoflower/nanowire intersurfaces. Consequently, the dual Z-scheme charge transfer pathway provided efficient channels for boosting electron transfer and charge separation, resulting in high C2H4, CH4, and CO yields of formed and exihibits an promising photoreduction rate of CO2 to CO (51.2 µmol/g.h), CH4 (42.4 µmol/g.h) and C2H4 (63.2 µmol/g.h), respectively. DFT, in situ Diffuse reflectance infrared fourier transform spectroscopy, and temperature-programmed desorption tests were employed to verify the intermediates pathway. The study proposed a potential photocatalytic mechanism based on these findings.

Mechanism of Phosphate Desorption from Activated Red Mud Particle Adsorbents.

Herein, activated red mud particles are used as adsorbents for phosphorus adsorption. HCl solutions with different concentrations and deionized water are employed for desorption tests, and the desorption mechanism under the following optimal conditions is investigated: HCl concentration = 0.2 mol/L, desorbent dosage = 0.15 L/g, desorption temperature = 35 °C, and desorption time = 12 h. Under these conditions, the phosphate desorption rate and amount reach 99.11% and 11.29 mg/g, respectively. Notably, the Langmuir isothermal and pseudo-second-order kinetic linear models exhibit consistent results: monomolecular-layer surface desorption is dominant, and chemical desorption limits the rate of surface desorption. Thermodynamic analysis indicates that phosphorus desorption by the desorbents is spontaneous and that high temperatures promote such desorption. Moreover, an intraparticle diffusion model demonstrates that the removal of phosphorus in the form of precipitation from the surface of an activated hematite particle adsorbent primarily occurs via a chemical reaction, and surface micromorphological analysis indicates that desorption is primarily accompanied by Ca dissolution, followed by Al and Fe dissolutions. The desorbents react with the active elements in red mud, and the vibrations of the [SiO4]4- functional groups of calcium-iron garnet and calcite or aragonite disappear. Further, in Fourier-transform infrared spectra, the intensities of the peaks corresponding to the PO43- group considerably decrease. Thus, desorption primarily involves monomolecular-layer chemical desorption.