Monolayer Coverage Research Articles

Synergistic effect between montmorillonite and imidazolium-functionalized carboxylate-based polyelectrolyte for enhancing the removal of methylene blue

The composite of montmorillonite (Mt) and novel imidazolium-functionalized carboxylate-based polyelectrolyte (P(NaAA/VIC)) was formed through the bridging interaction of zwitterionic groups, enabling efficient and rapid removal of industrial cationic dye methylene blue (MB) from aqueous solution. The removal rate of pure P(NaAA/VIC) was difficult to reach 90%, while P(NaAA/VIC)/Mt composites achieved the removal rate of more than 95%. The substantial improvements of removal rate were attributed to the formation of larger adsorbed aggregates, facilitating easy separation. Importantly, Mt laminae, as a rigid structure, could effectively prevent molecular chain of polyelectrolyte curling due to electrostatic shielding after adsorption, which made the adsorption sites play a full role, thus enhancing the adsorption efficiency. The maximum adsorption capacity of composite (80 wt% P(NaAA/VIC) and 20 wt% Mt) was increased by about 20% compared with pure P(NaAA/VIC). And the excessive zwitterionic groups in polyelectrolyte would lead to a decrease in adsorption capacity. The systematic investigation revealed that the adsorption was a spontaneous exothermic process driven by electrostatic interactions, conforming to the pseudo-second-order kinetic model, in which the adsorption was monolayer coverage. The composite can achieve an high adsorption capacity of 1381.7 mg/g at 20 °C, demonstrating enormous potential in the treatment of cationic dye wastewater.

Single-stage microwave-irradiated activated carbon from corncob for ammonia nitrogen removal: Batch, attraction mechanism and regeneration studies

The existence of ammonia nitrogen (NH3-N) in water reservoirs contribute to the poor quality of water, thus affecting aquatic life and human. Therefore, the goal of this study was to treat NH3-N from wastewater using activated carbon derived from corncob (CCAC). The CCAC was produced through a single-stage microwave irradiation technique where carbon dioxide (CO2) was utilized for the gasification effect. The CCAC demonstrated a mesoporous surface area measuring 645.97 m2/g, accompanied by a total pore volume of 0.41 cm3/g. Furthermore, the average pore diameter was determined to be 2.74 nm. The equilibrium study revealed that NH3-N uptakes and NH3-N percentage removal increased (9.11–59.49 mg/g) and declined (91.10–59.49 %), respectively, when NH3-N initial concentration increased from 10 to 100 mg/L. At a solution temperature of 30 °C, the greatest adsorption capacity for NH3-N was observed, reaching 59.49 mg/g. Similarly, at a pH of 4, the adsorption capacity peaked at 71.46 mg/g. Adsorption of NH3-N onto CCAC obeyed the Langmuir isotherm model and pseudo-first order (PFO) kinetic model. It was determined that the maximum monolayer coverage, Qm was 78.05 mg/g. The investigation of the mechanism indicated that film diffusion is the rate-determining step in the adsorption process. In the thermodynamic section, the parameters of ΔH°, ΔS°, ΔG°, and Ea were computed to be −1.70 kJ/mol (exothermic in nature), 0.05 kJ/mol.K (elevated randomness at the solid-liquid interface), −18.22 kJ/mol (spontaneous) and 1.89 kJ/mol, respectively. The surface of CCAC was occupied with different functional groups namely nitro compound, aromatic compound, and phenol. These functional groups formed hydrogen bonding with NH3-N, thus aiding NH3-N removal from wastewater. In the regeneration study, CCAC can withstand up to 3 cycles before its yield dropped to 33.21 % and its adsorption capacity dropped to 10.15 %.

Metal-organic framework-derived LaFeO3@C: An adsorbent for removing organic dyes from water

Metal-Organic Frameworks (MOFs) and MOF-derived materials are emerging as a potential candidate in the field of adsorption owing to their vital properties of high surface area, tunable porosity and diverse functionalities. However, the instability of MOFs in harsh environmental conditions prompted to produce more stable forms of MOF-derived materials for adsorption applications. Carbonization of MOFs is becoming an efficient method to prepare stable metal oxide-carbon hybrids as adsorbents for pollutant removal. This study presents the first-time report on utilizing MIL-100(Fe)-derived mesoporous LaFeO3@C nanocomposites for the effective adsorption removal of methyl orange (MO) and sulforhodamine B (SRB). The nanocomposites having different surface chemistry and textural properties are formed from MOF-gel precursor by varying the calcination temperature in the argon atmosphere. The LaFeO3 nanoparticles in the nanocomposites crystallized into the orthorhombic structure, which is confirmed from the XRD, Micro-Raman and FTIR analysis. The material obtained at 700 °C (LFO@C-700) exhibited higher removal efficiency of 99% and 97.1% towards SRB and MO, respectively. The chemisorption is identified as the main rate-limiting step in adsorption and the isotherm follows the Langmuir model suggesting the monolayer coverage of the adsorbates. The successful elimination of dye contaminants from real water samples and industrial effluents by LFO@C-700 indicates the practical utility of this adsorbent material. Several key chemical interactions, including H-bonding, electrostatic interactions, π-π and cation-π interactions promote the adsorption process. Moreover, the LFO@C-700 nanocomposite shows reusability with sustainable adsorption for repeated experiment cycles, suggesting this adsorbent's cost-effective use in practical applications.

Spinterface Formation of Sexithiophene (6T) on Ferromagnetic Surfaces

Interfaces between organic molecules and ferromagnetic materials play a critical role in a variety of remarkable spin-related effects. In order to employ such spinterfaces in next-generation molecular spintronic devices, it is crucial to characterise and control these spin effects. Here, we report the features of prototypical spinterfaces comprised of sexithiophene 6T (C24H14S6) deposited on ferromagnetic metal and ferromagnetic oxide surfaces. We have investigated the controlled coverage of 6T monolayers on an Fe surface using a variety of advanced characterization techniques and show that adsorption leads to the formation of monodisperse conjugated solid islands. AFM results show that a 0.5 ML 6T deposition leads to solid islands, while with an increased thickness of 1.25 ML the material is deposited in the form of aggregated islands. XPS and UPS data reveal the orientation and electronic structure of the 6T/Fe system. Comparisons are also made to 6T adsorption on the more inert Fe3O4(001) surface revealing the importance of adsorption geometry, molecular packing and surface reconstruction in determining spinterfacial electronic structure and associated device performance.

Tuning the Emulsion Properties Influences the Size of Poly(Caprolactone) Particles for Drug Delivery Applications.

Advances in drug delivery have been accelerated with the addition of polymeric drug carriers. Direct delivery to a target site is a promising step in developing effective drug and gene therapies to treat disease. The efficacy of these drug carriers heavily relies on cell uptake without compromising critical cellular processes that promote cell viability. Drug release from biodegradable polymers is mediated largely by polymer degradation, and therefore the rate of polymer degradation dictates the feasibility of drug delivery applications. Traditionally, poly(caprolactone) (PCL) has only been used in long-term biomedical applications because the degradation time is much slower than other polymers. However, the biocompatibility of this polymer and the potential for longer delivery windows renders it a promising polymer candidate for drug delivery. In this work, we outline sixteen emulsion solvent evaporation preparation methods for PCL nanoparticles and microparticles to develop particles between 300nm and 1.7μm and with zeta potentials of -1.8mV. We further investigated particles in a size range suitable for systemic tumor delivery and inhaled aerosol delivery to determine cell biocompatibility with the polymer in lung adenocarcinoma, endometrial adenocarcinoma, and human embryonic kidney cells. We determined these particles aren't detrimental to cell viability below particle monolayer coverage atop cells and therefore these formulations hold promise for the next stage of development as sustained-release drug delivery carriers.

Adsorption of typical NDMA precursors by superfine powdered activated carbon: Critical role of particle size reduction

Control of N-nitrosodimethylamine (NDMA) in drinking water could be achieved by removing its precursors as one practical way. Herein, superfine powdered activated carbons with a diameter of about 1 µm (SPACs) were successfully prepared by grinding powdered activated carbon (PAC, D50=24.3 µm) and applied to remove model NDMA precursors, i.e. ranitidine (RAN) and nizatidine (NIZ). Results from grain diameter experiments demonstrated that the absorption velocity increased dramatically with decreasing particle size, and the maximum increase in k2 was 26.8-folds for RAN and 33.4-folds for NIZ. Moreover, kinetic experiments explained that rapid absorption could be attributed to the acceleration of intraparticle diffusion due to the shortening of the diffusion path. Furthermore, performance comparison experiments suggested that the removal of RAN and NIZ (C0=0.5 mg/L) could reach 61.3% and 60%, respectively, within 5 min, when the dosage of SAPC-1.1 (D50=1.1 µm) was merely 5 mg/L, while PAC-24.3 could only eliminate 17.5% and 18.6%. The adsorption isotherm was well defined by Langmuir isotherm model, indicating that the adsorption of RAN/NIZ was a monolayer coverage process. The adsorption of RAN or NIZ by SAPC-1.1 and PAC-24.3 was strongly pH dependent, and high adsorption capacity could be observed under the condition of pH > pka+1. The coexistence of humic acid (HA) had no significant effect on the adsorption performance because RAN/NIZ may be coupled with HA and removed simultaneously. The coexistence of anions had little effect on the adsorption also. This study is expected to provide an alternative strategy for drinking water safety triggered by NDMA.

Droplet slipperiness despite surface heterogeneity at molecular scale

Friction determines whether liquid droplets slide off a solid surface or stick to it. Surface heterogeneity is generally acknowledged as the major cause of increased contact angle hysteresis and contact line friction of droplets. Here we challenge this long-standing premise for chemical heterogeneity at the molecular length scale. By tuning the coverage of self-assembled monolayers (SAMs), water contact angles change gradually from about 10° to 110° yet contact angle hysteresis and contact line friction are low for the low-coverage hydrophilic SAMs as well as high-coverage hydrophobic SAMs. Their slipperiness is not expected based on the substantial chemical heterogeneity of the SAMs featuring uncoated areas of the substrate well beyond the size of a water molecule as probed by metal reactants. According to molecular dynamics simulations, the low friction of both low- and high-coverage SAMs originates from the mobility of interfacial water molecules. These findings reveal a yet unknown and counterintuitive mechanism for slipperiness, opening new avenues for enhancing the mobility of droplets.

Fabrication of physically multi-crosslinked sodium alginate/carboxylated-chitosan/montmorillonite-base aerogel modified by polyethyleneimine for the efficient adsorption of organic dye and Cu(II) contaminants

Efficient removal of contaminants, like heavy metal ions and dyes, from wastewater by eco-friendly and low-cost adsorbent is highly desirable. Herein, a green aerogel was prepared using sodium alginate/carboxylated chitosan/montmorillonite (MSC-P) as the basic framework, followed by polyethyleneimine functionalized and Ca2+ post-crosslinking. The multi-crosslinked aerogel exhibited the excellent adsorption capacity towards methylene blue (MB), Congo red (CR) and Cu(II), with the qm being 723.97 mg/g, 1573.21 mg/g and 203.99 mg/g, respectively. The mathematical model suggested that the adsorption process for MB fitted pseudo-first-order kinetics model better, whereas the CR and Cu (II)’s adsorption process were conformed to pseudo-second-order kinetics model. Moreover, the adsorption isotherm for three contaminants could be well described by Langmuir model, suggesting that the adsorption process was spontaneous and mainly controlled by monolayer coverage. Moreover, MSC-P aerogel exhibited good reusability as the removal efficiencies for MB and Cu(II) were 85.16 % and 51.4 % after ten cycles of adsorption–desorption, respectively. Importantly, it possessed considerable simultaneous removal ability for binary system mixed dyes. In combination of FTIR analyses, it was found that electrostatic attraction, hydrogen bonding, coordination and cation exchange were the main adsorption mechanisms involved. Therefore, the as-prepared aerogel can be considered as a promising adsorbent for the treatment of wastewater.

STM study of surface restructuring of oxidized Cu(100)

The Cu(100) surface offers a model platform for the investigation of the copper oxidation process. Starting from clean Cu(100), we characterized oxidized surfaces with varying oxygen exposure, sample temperature, and post-oxidation annealing conditions. Scanning tunneling microscopy was used to characterize the surfaces with atomic resolution imaging at 78 K. Annealing in O2 (P∼ 5·10−6 mbar) at 80-260 °C led to the (2√2 x √2) R45°Cu(100)-O missing row reconstruction (MRR), which self-limited at monolayer coverage and was relatively insensitive to exposure or temperature in this range. Further annealing of the MRR surface in UHV (PO2 < 10−9 mbar) at 160 °C resulted in large scale reorganization of the surface into MRR areas with a higher degree of step-bunching, coexisting with facet-like hills. The facets are decorated by terraces with a quasi-hexagonal lattice that we attribute to a Cu(110) c(6 × 2) oxygen induced reconstruction.

The role of oxygen incorporation in Ni (111) substrates on the growth of hexagonal boron nitride monolayers

Reliable and controllable growth of two-dimensional (2D) hexagonal boron nitride (h-BN) is essential for its wide range of applications. Substrate engineering is one of the critical factors that influence the growth of the epitaxial h-BN films. Here, we report the growth of monolayer h-BN on Ni (111) substrates incorporated with oxygen atoms via molecular beam epitaxy. It was found that the increase of incorporated oxygen concentration in the Ni substrate through a pretreatment process prior to the h-BN growth step would have an adverse effect on the morphology and growth rate of 2D h-BN. Under the same growth condition, h-BN monolayer coverage decreases exponentially as the amount of oxygen incorporated into Ni (111) increases. Density functional theory calculations and climbing image nudged elastic band (CI-NEB) method reveal that the substitutional oxygen atoms can increase the diffusion energy barrier of B and N atoms on Ni (111) thereby inhibiting the growth of h-BN films. As-grown large-area h-BN monolayer films and fabricated Al/h-BN/Ni (MIM) nanodevices were comprehensively characterized to evaluate the structural, optical and electrical properties of high-quality monolayers. Direct tunneling mechanism and high breakdown strength of ∼11.2 MV cm−1 are demonstrated for the h-BN monolayers grown on oxygen-incorporated Ni (111) substrates, indicating that these films have high quality. This study provides a unique example that heterogeneous catalysis principles can be applied to the epitaxy of 2D crystals in solid state field. Similar strategies can be used to grow other 2D crystalline materials, and are expected to facilitate the development of next generation devices based on 2D crystals.

Synthesis of graphene/silica composites and its removal efficiency of methylene blue dye from water

Water supply remains constant; however, industrial wastewater has been raised. Due to the high demand for clean water, there is a continued need for water treatment. Here, graphene nanoplatelets modified with silicon dioxide nanoparticles were synthesized and characterized. Structural, surface morphology and physichemical characteristics of GNP-SiO2 were characterized by FTIR, XRD, and SEM. The nanocomposite was assessed for methylene blue (MB) adsorption from wastewater. To study the impact of the adsorption parameters, the factorial design with multivariate method central design, analysis of variance, response surface 3D graph, Pareto Chart, and Normal probability plot was used. The experimental equilibrium data fit with the Langmuir isotherm model. Removal capacity (qm) was 495 mg g−1 for GNP-SiO2 nanocomposite with the formation of monolayer coverage and specific homogenous sites on GNP-SiO2 nanocomposite. The kinetic mechanism suggested that the PSO model fits kinetic MB removal mechanisms over the GNP-SiO2 nanocomposite and progressed profoundly via chemisorption. The MB cationic dye removal by GNP-SiO2 nanocomposite was by electrostatic attraction, hydrogen bond, and π–π interactions as well as the surface adsorption. The results revealed that prepared GNP-SiO2 nanocomposite was effective for MB adsorption from aquatic solution.

Computational Study on the Water Corrosion Process at Schreibersite (Fe2NiP) Surfaces: from Phosphide to Phosphates.

Phosphorus (P) is a fundamental element for whatever form of life, in the same way as the other biogenic macroelements (SONCH). The prebiotic origin of P is still a matter of debate, as the phosphates present on earth are trapped in almost insoluble solid matrixes (apatites) and, therefore, hardly available for inclusion in living systems in the prebiotic era. The most accepted theories regard a possible exogenous origin during the Archean Era, through the meteoritic bombardment, when tons of reactive P in the form of phosphide ((Fe,Ni)3P, schreibersite mineral) reached the primordial earth, reacting with water and providing oxygenated phosphorus compounds (including phosphates). In the last 20 years, laboratory experiments demonstrated that the corrosion process of schreibersite by water indeed leads to reactive phosphates that, in turn, react with other biological building blocks (nucleosides and simple sugars) to form more complex molecules (nucleotides and complex sugars). In the present paper, we study the water corrosion of different crystalline surfaces of schreibersite by means of periodic DFT (density functional theory) simulations. Our results show that water adsorbs molecularly on the most stable (110) surface but dissociates on the less stable (001) one, giving rise to further reactivity. Indeed, subsequent water adsorptions, up to the water monolayer coverage, show that, on the (001) surface, iron and nickel atoms are the first species undergoing the corrosion process and, in a second stage, the phosphorus atoms also get involved. When adsorbing up to three and four water molecules per unit cell, the most stable structures found are the phosphite and phosphate forms of phosphorus, respectively. Simulation of the vibrational spectra of the considered reaction products revealed that the experimental band at 2423 cm-1 attributed to the P-H stretching frequency is indeed predicted for a phosphite moiety attached to the schreibersite (001) surface upon chemisorption of up to three water molecules.

New-style electrokinetic-adsorption remediation of cadmium-contaminated soil using double-group electrodes coupled with chitosan-activated carbon composite membranes

Global soil cadmium (Cd(II)) contamination threatens the soil environment, food safety, and human health. Conventional electrokinetic remediation (EKR) and enhancement methods usually operate in strong electric fields, leading to strong side reactions and uneven removal. In this work, to remove Cd(II) from soil effectively in a low-voltage electric field, a new-style electrokinetic-adsorption remediation using double-group electrodes coupled with chitosan-activated carbon composite membranes (DE-EKR-CAC) was developed. Chitosan-activated carbon (CAC) composite membranes were synthesized for easy recovery and reuse of adsorbents. The effects of pH, contact time, initial concentration, and foreign ions on the removal of Cd(II) by the CAC composite membranes were determined. The CAC composite membranes performed well except in a strongly acidic environment (pH = 2.0). The soil pH varied between 3.4 and 5.0 in DE-EKR-CAC, where the CAC composite membranes were applicable. High concentrations of Ca2+ interfered with the adsorption of Cd(II), which means that the selectivity of CAC composite membranes for Cd(II) is not high enough. The Langmuir (R2 = 0.999) and pseudo-second-order kinetic (R2 = 1.0) models revealed the monolayer coverage and chemisorption mechanism, and the maximum adsorption capacity was 40.81 mg/g. Furthermore, SEM, FTIR, and XPS analyses suggest that physical adsorption, complexation of oxygen-containing functional groups, chelation of amino groups, and ion exchange are potential mechanisms for the adsorption of Cd(II) on CAC. DE-EKR-CAC performed better than the group remediated with one set of electrodes, with higher removal efficiencies and more uniform removal. The lowest energy consumption was 3.33 kWh/m3, which is lower than other enhancement methods. Separation of CAC composite membranes from soil is easy, and reuse performance is good. DE-EKR-CAC provides a potential option for Cd(II) removal from soil because of its better performance using low-voltage direct current, low energy consumption, and ease of recycling the adsorbent.

Real-space structural characterization of benzene monolayer on graphite (0001) surface investigated by low-temperature scanning tunneling microscopy

Real-space structural characterization of benzene (C6H6) adsorbed on the graphite (0001) surface was investigated at the nanoscale. Scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED) were used to assign a well-ordered 7×7R19.1° structure at around monolayer coverages. The STM image clarified the flat-lying adsorption of benzene with its molecular plane parallel to the surface. At a sample bias around the adsorption-induced highest occupied molecular orbital (HOMO) level, the STM image showed an elongated protrusion separated by a single nodal depression; this is because the degeneracy of the HOMO is lifted by the interaction with the substrate.

Role of concentration and hydrophobic nature of weak polyelectrolytes on adsorption structure and thermodynamics at oil-water interface: Study of several carboxylate polymers

Intermolecular structure, conformations, solvation and adsorption characteristics of four partially ionized polycarboxylic acids syndiotactic-poly(acrylic acid) (s-PAA), syndiotactic-poly(methacrylic acid) (s-PMA), isotactic-poly(methacrylic acid) (i-PMA) and atactic-poly(ethacrylic acid) (a-PEA) at oil (CCl4) - water interface is studied by molecular dynamics simulations over the range from dilute to monolayer coverage. Linearity and slope of Θ-Γ curves are correlated to conformational invariance and extent of adsorption (partial vs complete) respectively, within the range of concentration of study. Adsorption of i-PMA and a-PEA chains occurs deeper into the oil-side of interface region as driven by the greater hydrophobicity of these polymers. Higher tendency of highly extended s-PMA to desorb from the interface as compared to strong adsorption of compact coiled i-PMA is driven by their solvation behavior dictated by aspects of structural partitioning of chemical groups with respect to the solvents of the two phases. Hydrophobic side-group in the polyelectrolyte chain is responsible for the slower dynamics of the backbone. The observed variation in thickness of adsorbed layer and fractional interface coverage with concentration suggest partial adsorption of chain segments beyond saturation of interface rather than coiling of chains to accommodate additional chains. While a-PEA exhibits greater variation in interfacial tension, the change in electric potential difference across the interface indicates weak adsorption by s-PMA. The influence of the tacticity of PMA on dynamics and distribution of counter-ions is in agreement with experimental results. Results provide a significant advancement in our understanding of polyelectrolyte and polymer adsorption at oil-water liquid interface.

Facile surface-controlled synthesis of phytic acid-facilitated calcium carbonate composites for highly efficient ferric ion adsorption and recovery from rust

This work presents a simple synthesis of calcium carbonate (CaCO3)-based composites designed for the efficient adsorption of ferric ions (Fe3+) from solution, and specifically applied for Fe3+ recovery from rust. The strategy involves coordinating phytic acid (PA) with calcium ions (Ca2+) and coprecipitation with carbonate ions (CO32−) at room temperature to form phytate-CaCO3 (Ph-CC) composites. The obtained composites exhibited a robust mesoporous crystal structure with numerous phosphate groups of phytate functionalized on CaCO3 microparticles. The surface properties of the composites were optimized by adjusting the molar ratio (x) of PA:Ca2+ in synthesis. The Ph-CC0.10 composite (x = 0.10), with the highest specific surface area (99.56 m2/g), demonstrated exceptional Fe3+ adsorption (>99% efficiency in 80 min). The adsorption process followed the pseudo-second-order and Langmuir isotherm models, indicating monolayer coverage. Impressively, the maximum adsorption capacity reached 1385.85 mg/g, surpassing that of previously reported adsorbents. Thermodynamic studies confirmed a spontaneous and exothermic adsorption process. The superior Fe3+ adsorption of the composite was attributed to electrostatic and chelation interactions, with partial ion exchange. Furthermore, the Ph-CC0.10 composite effectively captured Fe3+ from rust dissolution in an acidic solution (pH 3) under sonication at 35 kHz for 60 min. These results highlight the potential use of the developed composites in mitigating environmental pollution and transforming waste materials into valuable sources. Therefore, Ph-CC composites are promising alternatives for wastewater treatment and metallurgical applications.

Tuning the ultra-microporosity in hierarchical porous carbons derived from amorphous cellulose towards a sustainable solution for hydrogen storage

Activated carbons exhibit a high grade of porosity, which together with structural stability, regenerability and cyclability makes them capable of achieving excellent hydrogen adsorption capacity. A further advantage comes from the ease of production and the use of recyclable and biocompatible materials. A simple way to produce activated carbons from amorphous cellulose involves procedures in which a pyrolysis process is combined with physical activation in CO2.We used this approach by optimizing the production process tuning the activation times. The aim is to evaluate the influence of this process parameter on the formation of the specific surface area, the pore volume and fraction of micropores with a typical size <2 nm. The influence of these structural parameters on the hydrogen adsorption properties was then evaluated. The textural and adsorption characteristics were investigated using a commercial volumetric apparatus (ASAP 2460, Micromeritics) at −196 °C and pressures between 0 and 1 bar, while the morphological properties were investigated using scanning electron microscopy.The results show that the nanostructured samples are characterized by a very high degree of ultra-microporosity (<0.7 nm) with an average pore size between 0.5 and 0.6 nm and a high specific surface area, reaching maximum values around 1500 m2/g and micropore volume up to 0.58 cc/g. These morphological characteristics strongly influence the hydrogen adsorption properties, where the molecules adsorbed reach values very close to the coverage of ideal monolayer. The synthesized activated carbon samples show a higher hydrogen adsorption capacity than similar commercial materials tested under the same thermodynamic conditions.

Toxic cadmium(II) monitoring and removal from aqueous solution using ligand-based facial composite adsorbent

Developing an eco-friendly composite adsorbent via an eco-friendly process for detection and removing Cd(II) from wastewater is urgently necessary due to the critical hazards of Cd(II) to public health and environmental safety. The chemical ligand of 2,2′-Biquinoline-4,4′-dicarboxylic acid (BIDA) was embedded directly on the mesoporous silica for the fabrication of facial composite adsorbent (FCA) for toxic cadmium (Cd(II)) ion detection and removal from wastewater solutions. The FCA nanostructures were characterized by SEM, TEM, and N2 adsorption/desorption analyzer systematically. The physicochemical properties of FCA, as well as the primary influencing factors and mechanism of Cd(II) detection and adsorption processes, were also investigated. More interestingly, a colorimetric method based on color enhancement upon adding Cd(II) was developed by the FCA to detect low concentrations of Cd(II) ions. The solution pH played a key factor in color formation and neutral pH of 7.0 was selected based on the optimum color formation. The limit of detection was 0.39 µg/L. The preeminent adsorption capacity of FCA toward Cd(II) was (159.21 mg/g) which was mainly ascribed to the complexation of Cd(II) with the functional groups of BIDA coating FCA. The adsorption isotherms and kinetics data preferably conformed to the Langmuir isotherms model with monolayer coverage. The detection and adsorption of Cd(II) were not affected by other cations at the optimum experimental conditions. The FCA exhibited high reusability based on the elution and regeneration performances. The elution was carried out using 0.20 M HCl and then the FCA was ready to use after washing with water without loss in its functionality. The successful removal and detection of Cd(II) water samples demonstrates the great potential of the proposed FCA to remediate Cd(II) polluted water to safeguard water quality.

Efficient separation, adsorption, and recovery of Samarium(III) ions using novel ligand-based composite adsorbent

The novel organic compound of ammonium (4-chlro-2-mercaptophenyl)carbamodithioate (ACMPC) was prepared and then subsequently grafted onto the mesoporous silica by direct approach for the preparation of composite adsorbent (CPA). The lanthanide (Ln(III)) intra-series separation behavior was measured using CPA and then the samarium (Sm(III)) ion was selected according to the high adsorption ability by CPA for effective separation, adsorption, and recovery in the solid-liquid approach. The mesoporous silica and CPA were characterized systematically for the evaluation of affecting experimental criterion. The solution acidity played an important factor as the alkaline pH area was avoided due to the hydroxide precipitation probability and pH 5.0 was selected for selective and effective Sm(III) ion separation and recovery. The data clarified that CPA exhibited high kinetic performances with high adsorption ability. The Sm(III) adsorption was highly fitted with the Langmuir adsorption isotherm model with monolayer coverage and the maximum adsorption capacity was determined as 155.13 mg/g. In addition, the diverse foreign ions were not reduced the Sm(III) ion adsorption significantly, and the CPA has approximately no adsorption capacity for other ions at this pH. The Sm(III) ion was strongly coordinated with the ACMPC and the expected highly stable complexation mechanism with the soft donor of N- and S- atoms. The elution of Sm(III) ions from the saturated CPA was desorbed successfully with 0.30 M HNO3. The regenerated CPA that remained maintained the high selectivity to Sm(III) ions and exhibited almost the same adsorption capacity as that of the original CPA. Therefore, the proposed CPA offered a cost-effective material and may be considered a viable alternative for effectively Sm(III) ion separation and recovery from waste samples as potential materials.

Detoxification of lead and arsenic from galamsey polluted water using nano synthesized iron oxide from cupola furnace slag

Drinking of water polluted with heavy metals is a means by which heavy metals bio accumulate in the human body. The rise in galamsey (illegal mining) activities in Ghana has resulted in heavy metal pollution in most water bodies in the country. Above the permissible limits, these metals cause health issues such as cancer, brain damage, kidney damage and other respiratory diseases. Hence, a smart solution to this menace is urgently needed. In this study, iron oxides were recovered from cupola furnace slag by magnetic separation and froth flotation. The recovered iron oxide was modified using electrospinning with the aid of polyvinyl alcohol after which it was calcined and used as adsorbent to detoxify lead and arsenic from two galamsey polluted water bodies in Obuasi, Ghana. Samples of the adsorbent were characterized using X-ray Fluorescence (XRF), X-ray Diffractometry (XRD), Fourier Transform Infrared Spectrometry (FTIR), Scanning Electron Microscopy (SEM) and Brunauer-Emmer-Teller (BET) method. The highest recovery for iron oxide using magnetic separation was 99.42% and that of froth flotation was 90.64%. The recovered iron oxide used as adsorbent was composed 53.04% iron oxide, with major phases like magnetite, hematite, goethite and quartz. Moreover, the surface functional group were determined to be Fe–O and OH. Also, the calcined nano fibres which were spherical in shape with rough surfaces had a specific surface area of 1.1331 m2/g. The contaminated and detoxified water were also analyzed using Atomic absorption Spectroscopy (AAS). Both adsorbent (beneficiated iron oxide and calcined nano fibre) performed well in the adsorption process, with the recovered iron oxide having 97.33% maximum lead removal efficiency while an 81.00% maximum removal efficiency for arsenic. The calcined nano fibre had a maximum of 99.99% removal efficiency for lead and 88.40% maximum efficiency for arsenic. Additionally, the adsorption fits the Langmuirian isotherm model better than the Freundlich model, indicating mono layer coverage.