Langmuir Model Research Articles

Preparation of ZnAlLa-LDHs by one-step hydrothermal method and its adsorption properties for phosphate

Abstract Phosphate is one of the main limiting factors of water eutrophication, and the effective removal of phosphate is essential to control the eutrophication of the aquatic environment and meet the increasingly stringent phosphate discharge regulations. This study successfully prepared ZnAlLa-LDHs materials using a simple hydrothermal method using triethanolamine as a soft template, which SEM, XRD, and FT-IR characterized. The results show that ZnAlLa-LDHs is a kind of two-dimensional porous structure material; the adsorption isotherm of ZnAlLa-LDHs on phosphate conforms to the Langmuir model, and the maximum adsorption capacity is 83.333 mg g−1; the adsorption kinetics conforms to the pseudo-second-order kinetic model, and the adsorption rate is mainly controlled by chemical adsorption; the adsorption mechanism of ZnAlLa-LDHs on phosphate is mainly ion exchange and electrostatic adsorption. ZnAlLa-LDHs have an excellent effect on phosphorus in wastewater from sewage treatment plants.

Lead (Pb) removal from gold mining-impacted water utilizing palm oil fuel ash (POFA)

Mining, particularly gold mining, is a lucrative industry. However, it poses significant environmental risks, such as releasing heavy metal elements into the soil and water. After gold mines are exhausted, whether they are small or large scale, the excavated sites often need to be repaired. This situation has led to a global concern regarding the presence of heavy metals from mining activities, which are known to be carcinogenic and harmful to living organisms. The concentration of heavy metals in these areas often surpasses safety limits, necessitating advanced treatment methods for their removal, especially lead (Pb) compounds from gold mining waste. One effective treatment method is the adsorption process. This study examined POFA's inherent capacity to remove lead from water contaminated by gold mining without modification. This method was preferred due to its high efficiency and cost-effective option for removing heavy metal compounds. According to the experiment's results, the largest adsorption capacity of 0.816 mg/g was followed by the greatest removal efficiency of 91.837%. The isotherm analysis found that the Langmuir model provided an outstanding fit for the experimental data. Thus, this relationship suggested that on the surface of the POFA, a monolayer and an adsorption process suitable for physical adsorption took place.

Flagella, palmella and cyst Haematococcus lacustris microalgae cells decorated on graphene oxide and graphene nanoplatelets-activated carbon as novel adsorbents for the removal of lead from water

Industrialization has led to generation of large quantities of waste which constitutes various toxic heavy metals such as lead (Pb). In this work, novel bio-nanostructured graphene-based microalgae nanohybrid adsorbents, using three different cell types of Haematococcus lacustris (i.e., flagella (flg-C), palmella (Pal-C) and cyst (Cyst-C)) to introduce more functional moieties and enhance the surface properties of the nanohybrids. The nanostructured graphene oxide-activated carbon modified with algae cells (GO-AC@algae) and graphene nanoplatelets-activated carbon modified with algae cells (GNPs-AC@algae) nanohybrids were characterized and used for the removal of Pb ions. The GO-AC@algae nanohybrids demonstrated a high lead removal efficiency of over 98.0%, whereas the GNPs-AC@algae nanohybrids achieved more than 85.0%. Among the GO-AC@algae nanohybrids, the nanohybrid with cyst cell (GO-AC@Cyst-C) shown remarkable efficacy as an adsorbent for the removal of Pb2+ ions from aqueous solutions due to its high specific area, abundance of oxygen-nitrogen-based functional moieties, hydrophilicity, and pore structure. Chemisorption was found to be a beneficial process for both GO-AC@algae and GNPs-AC@algae samples, where Pb2+ was adsorbed in a single layer onto the uniform material surface. Among the various adsorbents, GO-AC@Cyst-C achieved the highest monolayer adsorption capacity of 25.58 mg/g according to the Langmuir model, making it the most effective nanoadsorbents. Kinetic studies revealed that the sorption mechanism of GO-AC@algae were better described by the second-order kinetic model. Meanwhile, the first-order kinetic model was found to be suited for GNPs-AC@algae samples. The nanohybrids could be employed as greener adsorbents at industrial scale for wastewater treatment without incurring significant costs.

Preparation, Characterization, and Adsorption Performance of H2TiO3 Lithium Ion Sieves with Homogeneous Nanoparticles: Kinetics, Thermodynamics, and Mechanism Analysis

AbstractLi2TiO3 precursor with layered structure is successfully prepared by template‐free method using anatase TiO2 and Li2CO3, followed by the treatment of dilute hydrochloric acid, which leads to obtaining H2TiO3 lithium ion sieve nanoparticles with uniform dispersion and small size. The adsorption performance and mechanism of the H2TiO3 are being studied. The experimental results show that the H2TiO3 lithium ion sieve has a large BET specific surface area (19.10 m2 g−1) and good thermal stability. At the same time, it also has a high adsorption rate and adsorption capacity (55.13 mg g−1) towards Li+ in solution due to its high dispersibility and uniformity of particle size, which can expose more adsorption sites in LiCl solution. The adsorption capacity of the H2TiO3 lithium ion sieve can reach 46.63 mg g−1, which achieves 84.58% of the equilibrium adsorption capacity. The equilibrium adsorption parameters follow the Langmuir model perfectly, demonstrating that Li+ undergoes monolayer adsorption. The results of thermodynamic and kinetic analysis show that the adsorption behavior of H2TiO3 is spontaneous and conforms to the pseudo‐second‐order kinetic model, indicating the adsorption process is controlled by chemosorption. In addition, after five adsorption/desorption cycles, the H2TiO3 lithium ion sieve still shows a high adsorption capacity of 46.15 mg g−1, and the dissolution loss of titanium is only 0.14%, which shows that the cycle stability is excellent. XPS and zeta potential analyses illustrate that the adsorption mechanism of Li+ on the H2TiO3 is an ion exchange reaction between Li+ and H+, combined with the electrostatic attraction of the adsorbent surface. Additionally, the adsorption performance of H2TiO3 lithium ion sieve in West Taijinaier Salt Lake brine was tested, and the adsorbent material proves itself is a perspective candidate for lithium extraction from aqueous lithium resources.

The adsorption mechanism and optimal dosage of walnut shell biochar for chloramphenicol

Biochar derived from biomass pyrolysis has proven to be an excellent material for pesticide adsorption and can be used as soil amendment for pesticide non-point pollution. However, the adsorption and desorption mechanisms for certain biochar and pesticide are still unclear. In this study, we investigated the properties of biochar derived from walnut (Juglans regia L.) shell (WSB), and used batch equilibrium method to investigate the adsorption and desorption behavior for chlorantraniliprole (CAP). The physical-chemical analysis showed that there were mainly lignin charcoal of alkyl carbon, methoxyl carbon, aromatic carbon, and carboayl carbon as the primary carbon compounds of WSB. The π - π electron donor acceptor interaction, electrostatic interaction, and hydrogen bond were the primary adsorption mechanisms of the WSB adsorption. Batch equilibrium study under 298 K showed that WSB application in the soil significantly improved the adsorption ability for CAP, and the adsorption behavior was a mono-layer adsorption process as Langmuir model fitted the adsorption isotherm data better than the Freundlich model. While Freundlich model analysis showed that WSB addition to the soil changed the isothermal adsorption line from the S style to the L style. The spontaneous degree reaction of sorbents from strong to weak was in the following order: 5%-WSB >7%-WSB >10%-WSB >1%-WSB >3%-WSB > soil > WSB, and the maximum application effect was achieved at 5 % (m/m) WSB dosage mixed with the soil. Therefore, we considered that WSB addition in soil increased its CAP adsorption capacity, and 5 % (m/m) WSB application was the best choice for CAP pollution control. These data will contribute to the adsorption mechanism and the optimal use dosage of WSB for CAP pollution control.

Microwave-assisted synthesis of γ-alooh nanoflowers as an adsorbent for cadmium removal from domestic wastewater.

In this study, cadmium ions were effectively removed from domestic wastewaters using an adsorptive treatment strategy based on γ-AlOOH nanoflowers. A novel, rapid, and simple procedure was developed for the synthesis of the nanoflowers. Characterization studies were performed using X-ray powder diffraction patterns and scanning electron microscope images. The synthesized nanoflowers were utilized as adsorbent in the batch adsorption experiments. The influential parameters of the adsorption process were optimized, and a flame atomic absorption spectrophotometry (FAAS) system was used to determine maximum percent removal of cadmium ions. Matrix-matched calibration strategy, in which the calibration plot was developed in wastewater medium, was utilized for the accurate and precise quantification of cadmium in the effluent samples. The percentage removal efficiency values were calculated between 84 and 98% for different concentrations of cadmium ions in the wastewater samples. Equilibrium data was fitted to the four different linearization methods of the Langmuir isotherm model, as well as the Freundlich isotherm model and Elovich isotherm model. The best fitting was achieved for the Langmuir model with a high R2 value of 0.9956 and maximum adsorption capacity was calculated as 6.23mg/g.

Adsorption of fluoxetine in aqueous environments: Development of macroporous cryogels based on sodium poly(acrylate) and carboxymethyl chitosan

This study focuses on the development of macroporous monoliths using cryopolymerization of sodium acrylate/carboxymethyl chitosan solutions for the adsorption of the antidepressant fluoxetine in aqueous environments. The cryogels were characterized using various analytical techniques, and the effects of pH, temperature, initial concentration, and contact time on the adsorption capacity were investigated. The surface charge of the cryogel was negative when pHsolution > pHPZC, and pH 8.5 was optimal for swelling rates and fluoxetine removal efficiency. The NaPA4-CMCs cryogel (0.5 mg.mL−1) showed the best adsorption performance, with the pseudo-first-order model best describing the experimental kinetics data. The intraparticle diffusion model revealed rapid diffusion through macropores and mesopores. The Langmuir model fitted well to the experimental adsorption equilibrium data, with qmax = 80.6 ± 3.4 mg.g−1. The adsorption process was favorable, exothermic, and governed by physisorption, involving electrostatic, hydrogen bonding, π–π, and hydrophobic interactions. The binary solvent HCl (0.1 M)/methanol 1:1 v/v was effective for regenerating the adsorbent, with adsorption efficiency greater than 60 % after three cycles of reuse. The study highlights the potential of these macroporous monoliths for the effective removal of antidepressants from aqueous environments.

Enhanced Adsorption of Cadmium by a Covalent Organic Framework-Modified Biochar in Aqueous Solution.

In the environmental field, the advancement of new high-efficiency heavy metal adsorption materials remains a continuous research focus. A novel composite, covalent organic framework-modified biochar (RH-COF), was fabricated via an in-situ polymerization approach in this study. The COF-modified biochar was characterized by elemental analysis, BET analysis, SEM, FT-IR, and XPS. The nitrogen and oxygen content in the modified material increased significantly from 0.96% and 15.50% to 5.40% and 24.08%, respectively, indicating the addition of a substantial number of nitrogen- and oxygen-containing functional groups to the RH-COF surface, thereby enhancing its adsorption capacity for Cd from 4.20 mg g-1 to 58.62 mg g-1, representing an approximately fourteen-fold increase. Both the pseudo-second-order model and the Langmuir model were suitable for describing the kinetics and isotherms of Cd2+ adsorption onto RH-COF. The adsorption performance of Cd2+ by RH-COF showed minimal sensitivity to pH values between 4.0 and 8.0, but could be slightly influenced by ionic strength. Mechanistic analysis showed that the Cd2+ adsorption on RH-COF was dominated by surface complexation and chelation, alongside electrostatic adsorption, surface precipitation, and Cπ-cation interactions. Overall, these findings suggest that the synthesis of COF-biochar composite may serve as a promising remediation strategy while providing scientific support for applying COF in environmental materials.

ADSORPTION OF TEXTILE DYE ACID GREEN 42 (AG42) ON ACTIVATED CARBON FROM CHICKEN EGGSHELLS (CAC30)

The present work is a contribution to the valorization of chicken eggshells, an abundant waste product in Cote dIvoire, as a credible alternative to commercial activated carbon.Chemicalactivation of the precursorwascarriedoutwith30%phosphoricacidfor24h of contactin a ratio of 200 g of material to 100 mL of acid, and calcined at 600°C for 1h. The surface of the activated carbon obtained was studied using the BET (Brunauer-Emmett and Teller) method, which consists in establishing the adsorption isotherm for nitrogen N2. The results reveal a specific surface area of 5.42 m2.g-1, 65.68% of micropores and a pHzc of 7.40. Chemical characteristics determined by Boehms method indicate the basic nature of the surface. The elemental composition is dominated by oxygen(50.53%),calcium(30.78%)andcarbon(11.33%).The experiments demonstrated that the removalof AG42by adsorption on CAC30 is influenced by contact time, activated carbon mass, solution pH, and initial concentration and temperature of the dye aqueous solution. Adsorption kinetics followed the pseudo-second-order model and the isotherm is described by the Langmuir model. The thermodynamic study revealed the spontaneous (ΔG < 0) and exothermic (ΔH < 0) nature of dye adsorption, with a well-organized distribution of dye molecules at the adsorption sites (∆S°< 0).

CTAB-Si Nanoparticles Derived from Rice Husk Ash for Nitrate Ions Removal in Simulated Wastewater

In this study, silica (Si) nanoparticles derived from rice husk ash is coated with cetyltrimethylammonium bromide (CTAB), a cationic surfactant, and used as adsorbent of nitrate ion in wastewater. CTAB functionalized Si (CTAB-Si) nanoparticles were characterized using scanning electron microscope (SEM), energy dispersive X-Ray (EDX), dynamic light scattering (DLS) Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The synthesized CTAB-Si nanoparticles has a non-spherical shape, with visible polydispersity and is amorphous with average particle size of 72nm. It showed stretching vibrations of silanol at 963cm-1, siloxane at 1073cm-1, sharp peaks at 2852cm-1 and 2922cm-1 due to the methylene tail of CTAB and amine peak at 1,384cm-1. An ∼80% nitrate removal and adsorption capacity of 7.98 mg NO3/g CTAB-Si nanoparticles was obtained at optimized condition using Face Centered Central Composite Design (FC-CCD) at pH 4, 50 mgL-1 of adsorbate concentration, 0.2 gL-1 adsorbent dose and 30 minutes contact time. The adsorption isotherm and kinetic models fits well in Langmuir model and Pseudo second order with a R2 of 0.984 and 0.999 respectively. The efficiency of the nanoparticle after 5 adsorption cycles was ∼50% nitrate removal.

Study of adsorption isotherms and kinetics models for lead ions removal from simulated wastewater using three-dimensional, printed water-filtration system with synthesized α-Fe2O3

In this study, lead ions were removed from simulated wastewater by batch adsorptive filtration. A three-dimensional printed water filtration was designed using a blender and successfully synthesized from a PLA spool and a 3d printer machine. The filter surface was treated with NaOH solution to hydrolyze the polyester group in PLA. After that, α-Fe2O3 was prepared by the coprecipitation method and coated on the filter through doping and drying. α-Fe2O3 was characterized by X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDX), and Brunauer-Emmet-teller (BET). The results successfully indicate the synthesis of α-Fe2O3 consisting of 67.3% Fe and 32.7% O2. α-Fe2O3 appeared to have a surface area of 95 m²/g with distinct morphology and functional group. The effect of initial Pb concentration (100-800) ppm and the effect of contact time (5-120) min on the removal process were studied. Lab data was collected, and the adsorption was investigated kinetically. The 3d printed filter system coated by iron oxide showed significant and promised results for wastewater treatment and lead ions removal using this technique. Also, the results showed that the adsorption of Pb ions on the α-Fe2O3 surface fitted with the Langmuir model, with a correlation coefficient (R²) of 98.65%. The kinetic model’s investigations revealed that the pseudo-second-order model was the most fitted model for the process with R² of 99.997%. The highest adsorption saturation capacity was 165.2 mg/g adsorbent.

Removal of Lead Cations by Novel Organoclays Derived from Bentonite and Amphoteric and Nonionic Surfactants.

For many decades, natural and modified clay minerals have been used as adsorbents to clean up aquatic and soil ecosystems contaminated with organic and inorganic pollutants. In this study, organoclays based on bentonite and various amphoteric and nonionic surfactants were synthesized and tested as effective sorbents for lead ions. The maximum values of R were obtained when describing the sorption processes using the Langmuir model, which ranged from 0.97 to 0.99. The adsorption of lead ions by these organoclays was investigated using different sorption models including the Langmuir, Freundlich, and BET. It was found that, according to the values of limiting adsorption to the Langmuir equation, the synthesized organoclays formed an increasing series: organoclay with cocamide diethanolamine < bentonite < organoclay with lauramine oxide < organoclay with sodium cocoiminodipropionate < organoclay with disodium cocoamphodiacetate < organoclay with alkyl polyglucoside. The Gibbs energy for all of the analyzed samples was calculated and found to be negative, indicating the spontaneity of the cation adsorption process in the forward direction. The maximum value of the adsorption capacity of lead cations on organoclay-based bentonite with alkyl polyglucoside was 1.49 ± 0.05 mmol/g according to the Langmuir model, and 0.523 ± 0.003 mmol/g as determined by the BET model. In the process of modifying bentonite, there was an increase in negative values of the zeta potential for organoclays compared to the initial mineral, which clearly enhanced their electrostatic interactions with the positively charged lead ions. It was hypothesized, based on the physicochemical principles, that exchange adsorption is the main mechanism for lead absorption. Based on chemical approaches, organoclays based on amphoteric surfactants absorb lead mainly through the mechanisms of electrostatic attraction, ion exchange, and complexation as well as the formation of insoluble precipitates. Organoclays based on nonionic surfactants, on the other hand, absorb lead through mechanisms of complexation (including chelation) and the formation of insoluble chemical precipitates. The comparison of isotherms from different models allows us to find the most accurate match between the model and the experimental data, and to better understand the nature of the processes involved.

Engineered MXene/Bi2S3 nanoflowers in sodium alginate hydrogel: A synergistic eradicator of disinfected byproducts in aqueous environment

In this work, Bi2S3 nanoflowers were in situ anchored on the surface of Ti3C2 via a hydrothermal process to obtain MXene-supported Ti3C2/Bi2S3 nanocomposite, then incorporated inside in sodium alginate polymer to prepared hydrogel materials (Ti3C2/Bi2S3@SA-H) which outperforms and have an excellent capability for the removal of pollutants like disinfected byproducts. The synthesized hydrogel material Ti3C2/Bi2S3@SA-H may be utilized for a variety of functional materials in environmental applications. Furthermore, the Ti3C2/Bi2S3@SA-H was characterized by SEM, EDX, XRD, BET, AFM, FTIR, Zeta potential, XPS, Raman and TGA. Remarkably, Ti3C2/Bi2S3@SA-H hydrogel 0.007 cm3 g−1, 159.5 nm and 0.0017 cm3 g−1, 160.5 nm materials exhibited the highest average pore diameter. The research focused on evaluating the adsorption capability of Ti3C2/Bi2S3@SA-H hydrogel materials for 2,6-dibromo-4-nitrophenol (DBNP), 2,4,6-triiodophenol (TIP), 2,4,6-Trichlorophenol (TCP) and 2,6-dichloro-4-nitrophenol (DCNP). The findings indicated that the material exhibited the eradication efficiency of about 662, 657, 647 and 617 mg/g from DBNP, TIP, TCP and DCNP respectively. Several adsorption isotherms were extensively examined, encompassing the Temkin, Langmuir and Freundlich models, alongside pseudo-first and second-order models. The Langmuir and pseudo-second-order models showed the highest degree of consistency with the observed data. Concerning regeneration and reusability, the materials demonstrated easy regeneration and effective recyclability over the course of 10 cycles. The notable adsorption capacity, coupled with the innovative combination of Ti3C2/Bi2S3 and polymer hydrogel, along with its recyclability, positions our material Ti3C2/Bi2S3@SA-H as a highly prospective competitors for wastewater treatment and other critical areas in water research.

Facile Synthesis of Core-Shell Magnetic Iron Oxide@SiO2-NH2 Nanoparticles and Their Application in Rapid Boron Removal from Aqueous Solutions

In this study, amino-functionalized magnetic particles (iron oxide@SiO2-NH2) with core-shell structures were synthesized and evaluated for rapid boron removal from aqueous solutions. The results showed that the specific surface area of the iron oxide@SiO2-NH2 (131.24 m2⋅g−1) increased greatly compared to pure iron oxide (30.98 m2⋅g−1). The adsorption equilibrium was less than 2 h, with an adsorption capacity of 29.76 mg⋅g−1 at pH = 6 at 15 °C. The quasi-second-order kinetic model described the boron adsorption process well, and both the Langmuir and Freundlich models were suitable for characterizing the adsorption isotherms. The zeta potential and XPS analysis before and after adsorption revealed that the main adsorption mechanism was the hydrogen bonding formation between the terminal -NH2 groups of the adsorbent and the boric acid. In addition, the adsorbent still maintained a high adsorption performance after five adsorption–desorption cycles, which illustrated that the iron oxide@SiO2-NH2 may be a potential adsorbent for environmental boron removal treatment.

Применение моделей адсорбции при исследовании поглощения ионов никеля почвой

The aim of the presented work is to study the absorption of nickel ions by soils of the Udmurt Republic using four sorption models. Humus horizons (0–20 cm) of Albeluvisols Umbric, Leptosols Rendzinic and Phaeozems Albic soils widely distributed in Udmurtia were selected as objects of nickel adsorption research. According to the Langmuir model, good sorbents are characterized by high Amax values and low – KL, therefore, the best sorbent of nickel ions is Albeluvisols Umbric (Amax=0.0562 mol/kg, KL=2075.19 dm3/mol), and a weaker absorber is Phaeozems Albic (Amax=0.0192 mol/kg, KL=19474.48 dm3/mol), Leptosols Rendzinic occupies an intermediate position (Amax=0.0289 mol/kg, KL=14766.47 dm3/mol). The negative value of the Gibbs energy (∆G=–17.97 kJ/mol for Albeluvisols Umbric, –22.59 kJ/mol for Leptosols Rendzinic and –23.24 kJ/mol for Phaeozems Albic) indicates the spontaneous nickel adsorption by soil absorbing complex (SAC). In accordance with the Freundlich model, in all types of studied soils, the nickel ion – SAC binding energy decreases as the surface is filled, herewith the studied soils are characterized by heterogeneity of sorption centers. The approximation coefficient of the Temkin model is in the range of 0.80–0.85, therefore, the discrepancy between the experimental data of the theoretical model indicates the absence of interaction between the adsorbed particles. The Dubinin – Radushkevich model allows us to determine the nature of adsorption forces, as well as the value of the average free energy of adsorption: E=8,325 kJ/mol in Albeluvisols Umbric, 9.5477 kJ/mol in Leptosols Rendzinic and 9.6296 kJ/mol in Phaeozems Albic. Consequently, chemisorption is characteristic of all soils, and proceeds by an ion-exchange mechanism.

Rapid and selective separation of heavy metal ions from aquatic medium using a bidentate functionalized hybrid material

Low-cost mesoporous silica material, functionalized with a bidentate pyrazolyl pyridine metal acceptor and presenting a high specific surface area of 417 m²/g, was synthesized (mSi-L3) using a two-step procedure and characterized in detail to confirm the successful covalent binding onto silica surface. Notably, mSi-L3 exhibited strong selectivity for PbII among CdII and CuII ions, and displayed rapid metal ion removal, typically less than 10 min, from water samples.The influence of various environmental parameters on the adsorption process, such as pH, contact time and temperature, was systematically investigated. Optimal adsorption of metal ions was achieved at pH 6, as lower pH values reduced the availability of active sites due to competitive hydronium ion presence. Kinetic studies indicated that the adsorption process adhered to the pseudo-second-order model, suggesting a chemisorption mechanism. Temperature significantly influenced the adsorption capacity, with increased temperatures enhancing metal ion removal and confirming the endothermic nature of the process. The isotherm study suggests that the Langmuir model accurately describes the adsorption process, confirming that CuII, CdII and PbII ions are adsorbed as a monolayer on the homogeneous surface of m-SiL3 material, implying that the material has uniform adsorption sites where each metal ion occupies a distinct site without interaction with neighbouring ions. These findings underscore the importance of optimizing environmental conditions to maximize the efficiency of mSi-L3 for heavy metal removal. Also, mSi-L3 demonstrated excellent stability, with only a slight (∼1−3 %) decrease in functional groups on its surface after multiple regeneration cycles. Extensive analytical studies conducted with real water samples provided further evidence of the stability and effectiveness of mSi-L3 for the separation of metal trace elements of lead, copper and cadmium.

Binding mechanisms of trivalent chromium on colloidal phases from ultramafic systems: Insights from batch experiments and XAS analysis

Understanding the availability and mobility of chromium is a key factor in gaining insight into the fate of chromium and thus essential for assessing the risk of contamination and developing effective remediation strategies. In the natural environment, such as ultramafic systems, which are natural pools of chromium, chromium occurs mostly in the trivalent state (Cr(III)), which is known to have a high affinity for the solid phases such as particles and colloids. However, since Cr(VI) is more toxic, the vast majority of experimental studies focus on its reduction to Cr(III), which is often considered to form (hydr)oxide precipitates due to its poor solubility. Furthermore, while the oxidation state of Cr dictates its geochemical behavior, its interaction with particles and colloids is rarely controlled or monitored. Therefore, the interaction mechanisms between Cr(III) and particles or colloids require further attention. In this study, ten mineral phases (goethite, hematite, pyrolusite, kaolinite, montmorillonite, chlorite, serpentine, fuchsite, amphibole, and chromite) and one organic phase (humic acid), relevant to chromium bearing and carrier phases in ultramafic soils, were investigated to explore their interaction with Cr(III) species. These phases were first characterized by various techniques (including XRD, XRF, SEM, and BET). Adsorption and desorption experiments of Cr(III) on these phases were then carried out, and the distribution of Cr oxidation states in both the aqueous and solid phases was carefully monitored using UV–vis spectroscopy, geochemical speciation modeling, and Cr K-edge XAS spectroscopy. With the exception of pyrolusite, where partial oxidation of Cr(III) to Cr(VI) occurred, Cr(III) was shown to persist as a single oxidation state in all experiments. Desorption analyses showed significantly low desorbed rates, which further confirmed the prevalence of Cr(III). Experimental sorption isotherm data were interpreted using the Langmuir model and its linearized form, which provides important thermodynamic characteristics of adsorbents related to their structural and surface features. This study will provide better constraints for the understanding and prediction of Cr behavior and fate in the environment, especially in ultramafic systems.

Synthesis of bifunctional copolymeric nanofibers with selective extracting U(VI) from the solution and antibacterial property

Facing the problem of future nuclear fuel shortage, developing high-performance adsorbent materials is key. In this work, the amidoxime group/imidazole functionalized ionic liquid copolymer fibers containing bromide salts, and fluoroborate salts (namely P(AO/VEIMBr)8 and P(AO/VEIMBF4)6) were prepared by a one-pot method and free radical polymerization, hydroxyl amination reaction and electrostatic spinning, and characterized by SEM, FT-IR, and 1 H NMR. The influence of solid-liquid ratio, ionic strength, and adsorption time on the adsorption performance was investigated by batch adsorption experiments. In the meanwhile, the adsorption kinetics and thermodynamic processes of U(VI) on the copolymer fibers was also studied. Adsorption mechanism of U (VI) on polymer fibers was explored by XPS spectroscopic analysis combined with DFT method. Finally, the antimicrobial properties of the copolymer fibers were tested. The experimental results showed that the polymer nanofibers synthesized for U(VI) has a fast adsorption, high adsorption capacity at ionic strength close to seawater, and excellent reusability. The adsorption process conformed to the pseudo-second-order kinetic model and Langmuir model, which indicated that chemical adsorption and monolayer adsorption are dominant for adsorption U(VI) on the polymer nanofibers, and exhibits the highest Uranium adsorption capacity (76.92 mg/g and 81.96 mg/g at pH=8.1+0.1, respectively). XPS result showed the amine nitrogen and oxime oxygen in the amidoxime functional group were coordinated with uranyl(VI) ions. The antibacterial experiments showed that the copolymer fibers have antimicrobial properties and the antibacterial rate is over 90 %. Therefore, the nanofibers may be a promising material for extracting uranium from the weak alkaline wastewater or seawater.

Effect of natural aging on biochar physicochemical property and mobility of Cd (II).

This project utilized both field experiment and laboratory analyses to address the gap in understanding regarding the alterations in properties and functions of biochar, and the impact of heavy metal passivation in soil over long-term natural field aging. The study aimed to examine the changes in the physical and chemical characteristics of biochar over an extended period of natural aging. Additionally, it sought to analyze the impact and mechanisms of biochar in reducing of the harmful effects of the heavy metal cadmium (Cd) during the aging process. Both original and aged biochar conformed to the pseudo-second-order kinetics model and the Langmuir model. The aging process enhanced the adsorption of Cd by biochar and mitigated the leaching of Cd2+ into the soil. These findings provide a scientific basis for evaluating biochar's environmental behavior and its potential use in the remediation of soil contaminated with heavy metals.

Tailoring Morphology of MgO with Mg-MOF for the Enhanced Adsorption of Congo Red.

The active site is a highly anticipated property of adsorbent in the field of separation, as it enables a concurrent enhancement of both adsorption efficiency and adsorption rate. Herein, employing morphology-oriented regulation, we successfully fabricated heterogeneous MgO adsorbent from a magnesium-based metal-organic framework (MOF) precursor, octahedral MgO-M and laminated sheets MgO-P, for the capture of Congo red (CR). Specifically, the octahedron MgO-M exhibits a greater abundant of moderately and strongly alkaline sites, which facilitate the adsorption of CR. Furthermore, the synergistic effect between alkaline site and lattice oxygen further enhances the adsorption process. The adsorption data align more closely with the Pseudo-second-order kinetic model and Langmuir models. Notably, the exceptional adsorption capacity (exceeding 1900 mg·g-1 for MgO-M) and the secondary regeneration efficiency (over 96% removal rate across six cycles) offer promising prospects for future industrial applications, effectively addressing challenges related to poor water stability and difficult storability. Additionally, characterizations reveal the positive roles of alkaline sites, lattice oxygen, and pore structure in capturing significant quantities of CR through mechanisms such as electrostatic interactions, hydrogen bonding, and pore filling.