Brunauer Emmett Teller Isotherm Research Articles

Surface-Functionalized Magnetic Silica-Malachite Tricomposite (Fe-M-Si tricomposite): A Promising Adsorbent for the Removal of Cypermethrin.

This study assessed the efficacy of adsorption for eliminating the agricultural pesticide cypermethrin (CP) from wastewater using various adsorbents: silica, malachite, and magnetite. Magnetic nanocomposites (NCs) (with varying amounts of Fe3O4 0.1, 0.25, 0.5, 1.0, and 1.5 wt/wt %) were synthesized, including Fe3O4 nanoparticles (NPs), bicomposites, and tricomposites, calcined at 300 and 500 °C, and then tested for CP removal. The study was conducted in two phases, with the objective of initially assessing how effectively each individual NP performed and then evaluating how effectively the NCs performed when used for the adsorption of CP. Notably, the Fe3O4-malachite combination exhibited superior CP removal, with the 0.25-Fe-M NC achieving the highest adsorption at 635.4 mg/g. This success was attributed to the large surface area, magnetic properties of Fe3O4, and adsorption capabilities of malachite. The Brunauer-Emmett-Teller (BET) isotherm analysis indicated that the NCs had potential applications in adsorption and separation processes. The scanning electron microscopy and transmission electron microscopy revealed the spherical, irregular shaped morphology of the synthesized NPs and NCs. However, the X-ray diffraction (XRD) pattern of surface functionalized materials such as surface functionalized malachite [Cu2CO3(OH)2] with Fe3O4 and SiO2 may be complicated by the specific functionalization method used and the relative amounts and crystallographic orientations of each component. Therefore, careful interpretation and analysis of the XRD pattern, along with other techniques, are necessary for accurate identification and characterization of the functionalized material. The originality of this study lies in its comprehensive investigation of several adsorbents and NCs for CP removal at neutral pH. The innovation stems from the synergistic action of Fe3O4 and malachite, which results in improved CP removal due to their combined surface properties and magnetic characteristics. The application of magnetic NCs in adsorption and separation, as validated by BET isotherm analysis, highlights the potential breakthrough in addressing pesticide contamination.

Synergistic effects (adsorption and biodegradation) of Streptomyces hydrogenans immobilization on nano-reed biochar for further application in upflow anaerobic sludge blanket.

Water pollution due to wastewater is a serious issue that needs to be studied as many organic compounds are released from wastewater, affecting the ecosystem. Therefore, appropriate treatment methods should be used to prevent these effects. Phragmites australis biochar immobilized with bacteria was prepared in this study for use as an adsorbent in a pilot-scale up-flow anaerobic sludge blanket (UASB) to remove organic matter from wastewater in a buffalo farm. Combining reed biochar and immobilized Streptomyces hydrogenans introduces a synergistic effect: reed biochar serves as a substrate for microbial colonization and provides a conducive environment for microbial growth while Streptomyces hydrogenans, immobilized on the biochar, enhances the degradation of organic matter through its metabolic activities. Suitable techniques were employed, including infrared spectroscopy (FTIR) to determine the functional groups before and after adsorption, scanning electron microscopy (SEM) to determine the morphology of the composite before and after adsorption, X-ray diffraction (XRD) to examine the mineralogical changes through reflectometry, high-resolution diffraction and Brunauer-Emmett-Teller (BET) analyses to determine the surface area that always carried out by nitrogen adsorption/desorption technique based on the BET isotherm. Two-level factorial design experiments optimized using biochar, immobilized with bacteria, were employed to enhance the UASB performance. Chemical oxygen demand (COD) removal and biogas production were studied as a function of four experimental parameters: biochar dose, buffalo sludge dose, pH, and bacteria type. The buffalo sludge (manure) dose negatively affected the model's performance. The results showed better COD removal with Streptomyces hydrogenans S11 inoculation. The optimum biochar dose, buffalo sludge dose, and pH were 20 g L-1, 0%, and 7.5, respectively. The COD removal efficiency under these experimental conditions reached 92.70% with a biogas production of 5.0 mL. The experimental results of a validated point from the model were 90.80% for COD removal ratio and 4.80 mL for biogas production at 2 g L-1 biochar dose, 0% buffalo sludge dose, and pH 7.5 using Streptomyces hydrogenans S11 bacteria. A buffalo wastewater (BWW) anaerobic digestion experimental model was best fitted to the data under optimal conditions. This study aligns with the United Nations Sustainable Development Goals (SDGs), specifically SDG 6 (clean water and sanitation) and SDG 12 (responsible consumption and production). The implications of our work extend to large-scale applications, promising a greener and more sustainable future for wastewater treatment.

Comparative study of the effective removal of hexavalent chromium via calcium alginate and calcium alginate/Ulva fasciata composite

The present study revealed for the first time the removal of hexavalent chromium Cr(VI) with a high efficiency using an eco-friendly composite beads of alginate with the green alga Ulva fasciata compared to calcium alginate beads. This conclusion was reached in this study from the comparison of the removal efficiency of Cr(VI) by the well-known biosorbent material, calcium alginate (CA) with the studied calcium alginate/Ulva fasciata (CA/UF) biocomposite beads. The characterization of the prepared beads was achieved using several techniques such as Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy dispersive X-ray (EDAX). The Brunauer, Emmett, Teller (BET) and Barrett, Joyner, Halenda (BJH) analyses were also employed which indicated a three-fold increase in the surface area, a mean pore diameter of 2.3-fold and a total pore volume of 14-fold for calcium alginate/Ulva fasciata composite compared to calcium alginate beads. The results of batch experiments demonstrated the fast complete removal of Cr(VI) by the CA/UF composite compared to the maximum removal (75%) by CA. The Dubinin–Radushkevich isotherm model reflected the physical pore volume filling of Cr(VI) rather than adsorption on the pore walls, giving an adsorption mean free energy (2.24 kJ/mol) for CA/UF greater than that of CA (0.13 kJ/mol). Furthermore, Brunauer–Emmett–Teller isotherm reflected the multilayer adsorption for CA and CA/UF. Flory–Huggins isotherm model showed the more spontaneous adsorption for CA/UF than CA, with negative Gibbs free energy ΔG0 values of − 4.76 and − 6.91 kJ/mol, respectively. Whereas, Temkin isotherm model showed a higher adsorption binding energy of Cr(VI) on CA/UF than CA beads. In this study, the Langmuir model of Cr(VI) adsorption on CA/UF beads was the least applied among all studied adsorption isotherm models, which also revealed the multilayer adsorption mechanism of Cr(VI) ions. The Intra-particle diffusion model was applied for CA/UF composite beads, and this application suggested that the intra-particle diffusion is a part of the rate-limiting steps. The regeneration study showed a decrease in the adsorption efficiency of CA/UF composite from 97.4 to 82.3% for three consecutive cycles.

Green and Facile Synthesis of Porous SiO2@C Adsorbents from Rice Husk: Preparation, Characterization, and Their Application in Removal of Reactive Red 120 in Aqueous Solution.

In this work, a green, novel, fast, and facile approach for synthesizing a SiO2/C nanocomposite series from rice husk (RH) through quenching and grinding techniques has been reported along with its application for the adsorptive removal of Reactive Red 120 (RR120) dye from an aqueous solution. The effect of carbonization temperature on the textural and interfacial features of RH was confirmed by scanning electron microscopy (SEM), while the structure and elemental composition of the as-synthesized RH were investigated via XRD, Brunauer-Emmett-Teller (BET), FT-IR, Raman, and X-ray photoelectron spectroscopy (XPS). The RH had a high surface area (521.35 m2 g-1), large micropores, mesopores, and total pore volumes of 0.5059, 3.9931, and 5.2196 cm3 g-1, while SiO2 and C were the two major components. In the batch adsorption test, the effects of pH, contact time, adsorbent mass, temperature, and initial RR120 concentration were investigated. The maximum adsorption capacity was fitted by Langmuir, Freundlich, Temkin, Dubinin-Radushkevich (D-R), Hasley, Harkins-Jura, and BET isotherm models, and Langmuir was the best-fitted model. In addition, the pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich chemisorption models were used to explain the adsorption kinetics. Additionally, the values of Gibbs free energy, enthalpy, and entropy thermodynamics suggested that the RR120 adsorption phenomenon by RH8-3 was endothermic and spontaneous. The adsorption process was controlled by a physical mechanism, and the maximum adsorption capacity was found to be 151.52 mg g-1 at pH 2, with a contact time of 90 min, adsorbent amount of 0.03 g, and temperature of 313 K. The adopted technique may open up a new alternative route for the mass utilization of RH for the removal of dyes in water and wastewater and also for various practical applications.

Asphaltene removal from model oil solution by N doped graphene in a fixed bed column

Asphaltene removal in the crude oil industry is a significant issue. It is essential to develop cost-effective adsorbents to alleviate the problems associated with the presence of asphaltene in oil transportation. Performing continuous adsorption experiments assists in getting an insight into the practical application of novel adsorbents. For the first time, N-doped graphene (N-G) was synthesized for asphaltene removal form model oil solution in a continuous adsorption process. X-ray diffraction patterns, transmission electron microscopy, field emission scanning electron, and Brunauer–Emmett–Teller isotherms were used to characterize the prepared sorbents. The synthesized N-G was mesoporous with high porosity and specific surface area of 134 m2/g. The effects of three parameters were investigated: initial asphaltene concentration from 50 to 200 ppm, flowrate at 1–10 mL/min, and bed depth of 5–20 cm. The synthesized N-G was well suited in the asphaltene removal process due to the strong interactions between asphaltene and adsorbent surface arising from the π–π interaction between nitrogen on the N-G surface and the aromatic rings in asphaltene. The highest amount of asphaltene removal occurred at low flowrates and high bed depth while the effect of concentration was less than others. The highest removal amount in the breakthrough curve was achieved at 1 mL/min flow rate. The good removal efficiency even after several cycles of regenerations indicates a considerable potential of reusability. In sum, N-G could be a highly efficient adsorbent for dynamic asphaltene removal on a large scale.

Synthesis and characterization of novel binuclear zinc complex, immobilization in nano-porous support, and its catalytic application

Binuclear zinc complex, [Zn2(L)(I)2(CH3CN)] (I) (LH2 = 1,2-phenylenebis(azaneylylidene))bis(methaneylylidene))bis(2-methoxyphenol)) was prepared and single-crystal X-ray diffraction was used to establish the structure of complex assembly. Organic acid and base were used to functionalize the nano-porous material and then binuclear Zn complex was grafted into the modified materials. Brunauer-Emmett-Teller isotherm (BET), Nuclear Magnetic Resonance (NMR), Inductively Coupled Plasma analysis (ICP), X-ray Diffraction (XRD), Fourier transform infrared spectra (FT-IR), thermogravimetric analysis (TG), Scanning electron microscope (SEM), etc., were used to characterized the synthesized nano-catalysts to check for existence of guest moiety, structural stability of the parent and modified catalysts. Catalytic performance was noticeably enhanced post modification; without catalyst, acid/base functionalized, Zn2 immobilized catalyst. Binuclear zinc immobilized on acid/base silica catalyst exhibited a maximum 95%, 89% conversion of piperidine, and 87% and 86% conversion of aniline respectively. Prior to the theoretical investigation the bond parameters of the binuclear zinc complex were measured experimentally. Time-dependent Density Functional Theory (TD-DFT) and Density Functional Theory (DFT) methods were used to calculate the molecule's UV–Vis absorption spectra at B3LYP as well as LANL2DZ and 6–31G(d)). LUMOs and HOMOs energy gap were determined from the electronic transitions to determine electrophilicity index (ω), softness (S), electronegativity (χ), hardness value (Ƞ), and chemical potential (μ), etc.

Synergistic copper-modified covalent triazine framework for visible-light-driven photocatalytic degradation of organic pollutant

The current investigation studies the covalent triazine framework (CTF) with copper modification. The analyses comprised several characterizations including, i.e. FTIR (Fourier Transform Infrared Spectroscopy), XPS (X-ray Photoelectron Spectrometer), SEM/EDX (Field Emission Scanning Electron Microscopy/Energy-dispersive X-ray), XRD (X-ray Diffractometer), BET (Brunauer–Emmett–Teller) isotherm and surface area, and UV–vis DRS (Diffuse Reflection Spectroscopy). Additionally, the effect of additional oxidants and scavengers is studied. The copper-modified CTF (CTF-Cu) was found to have favorable properties for photocatalysis purposes compared to pristine CTF-1. The copper modification extends visible light absorption, reduces estimated band gap energy, and modifies the microstructure and chemical composition of the pristine CTF-1 facet. Conclusively, the CTF-Cu exhibited higher performance for methylene blue degradation.

Enhanced UV light-driven photocatalytic degradation of methyl orange using MoO3/WO3-fluorinated TiO2 nanocomposites

TiO2-based heterogeneous photocatalysis destroys persistent organic pollutants (POPs) with a low-cost, environment-friendly alternative to the conventional method. In the current research, TiO2, TiO2-F, TiO2-F-MoO3, TiO2-F-WO3, and TiO2-F-MoO3-WO3 nano-photocatalysts were synthesized via the sol-gel route, and their photocatalytic performances were investigated for the removal of methyl orange (MO) dye in the presence of ultraviolet (UV) light in a suspension configuration. X-ray diffraction (XRD), Scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), UV–vis diffuse reflectance spectroscopy (UV–vis/DRS), and Brunauer-Emmett-Teller (BET) characterized structural, morphological, and optical properties. XRD analysis showed that the prepared catalyst was mainly anatase with a 6.29 to 17.54 nm crystal size. SEM and FTIR analysis confirmed the irregular morphologywith agglomerated particle size of 13.31 ± 2.55 nm and hydroxyl groups captured by water molecules. BET isotherms revealed five times higher surface area and pore volume in doped nanocomposites than undoped TiO2 nanoparticles (NPs). The light-absorption properties of TiO2 NPs were significantly increased by fluorine doping and subsequent coupling with WO3. The reason can be explained by increased visible light harvesting and photogenerated charge carrier recombination reduction. The highest photodegradation efficiency was found to be 99.68 % for TiO2-F-WO3 nanocomposites for MO dye (10 ppm). The best-fitted reaction rate constants were followed by the pseudo-second-order model and found to be 16.1×10−4 g.mg−1.min−1 for TiO2-F-WO3 nanocomposite. Overall, TiO2-F-WO3 can be considered a promising material for photocatalytic POPsdegradation in textile wastewater.

Impacts of Surface Adsorption on Water Uptake within a Metal Organic Nanotube Material.

The confinement-dependent properties of solvents, particularly water, within nanoporous spaces impart unique physical and chemical behavior compared to those of the bulk. This has previously been demonstrated for a U(VI)-based metal organic nanotube that displays ice-like arrays of water molecules within the 1-D pore space and complete selectivity to H2O over all other solvents and isotopologues. Based upon our previous work on D2O and HTO adsorption processes, we suggested that the water uptake was controlled by a two-step process: (1) surface adsorption via hydrogen bonding to hydrophilic amine and carboxylic groups and (2) diffusion of the water into the hydrophobic 1-D nanochannels. The current study seeks to evaluate this hypothesis and expand our existing kinetic model for the water diffusion step to account for the initial surface adsorption process. Vapor sorption experiments, paired with thermogravimetric and Fourier-transform infrared analyses, yielded uptake data that were fit using a Langmuir model for the surface-adsorption step of the mechanism. The water adsorption curve was designated a type IV Brunauer-Emmett-Teller isotherm, which indicated that our original hypothesis was correct. Additional work with binary solvent systems enabled us to evaluate the uptake in a range of conditions and determine that the uptake is not controlled by the vapor pressure but is instead completely dependent on the relative humidity of the system.

Mercury (II) removal from aqueous solutions by iron nanoparticles synthesized from extract of Eucalyptus grandis

Artisanal mining is the main source of mercury emissions in South America, which generates a serious environmental impact due to this toxic metal, recent research is directed to minimize the impact, therefore this study focuses on the green synthesis of nanoparticles for the absorption of mercury in water. For the synthesis of iron nanoparticles, an extract of Eucalyptus grandis was used with iron chloride salts using water as solvent. The synthesized nanoparticles showed a specific surface area of 131.90 m2/g, determined by Brunauer-Emmett-Teller isotherm (BET). Nanoparticles were characterized by Fourier transformed infrared spectroscopy (FTIR) and transmission electron microscopy (MET). The behavior of nanoparticles synthesized during Hg (II) retention was evaluated measuring pH, temperature, nanoparticle dosing, presence of other ions and comparing with other adsorbents. All analyses measured by atomic absorption spectroscopy by the cold vapor technique (CVAAS), presenting a retention percentage for Hg (II) between 75.05 and 79.59% with pH between 4 and 7. The adsorption isothermal was adjusted to the Freundlich model and the percentage of retention of Hg by the synthesized nanoparticle was 79.26%. This work shows a method for obtaining an environmentally friendly mercury adsorbent from iron and E. grandis with a mercury retention capacity comparable to commercial adsorbents.

Removal of perfluorooctanoic acid via polyethyleneimine modified graphene oxide: Effects of water matrices and understanding mechanisms

This research aimed to evaluate the adsorption behaviors and mechanisms of perfluorooctanoic acid (PFOA) onto polyethyleneimine modified graphene oxide (GO-PEI) from aqueous solutions. The adsorption capacity was significantly improved by doping polyethyleneimine (PEI) onto graphene oxide (GO). The Brunauer-Emmett-Teller (BET) isotherm model was considered as the best isotherm model in describing the PFOA adsorption onto GO-PEI3 (wPEI/wGO = 3). GO-PEI3 exhibited high adsorption capacity (qe = 368.2 mg/g, calculated from BET isotherm model) and excellent stability. The maximum monolayer amount of PFOA adsorption onto GO-PEI3 (qm = 231.2 mg/g) was successfully evaluated. The calculated saturated concentration (Cs = 169.9 mg/L) of PFOA on GO-PEI3 closely agrees with its critical micelle concentration (CMC = 157.0 mg/L), suggesting the formation of multilayer hemi-micelles or micelles PFOA structures on the surface of GO-PEI3. PFOA adsorption onto GO-PEI3 was inhibited by several factors including: the presence of humic acid (HA) by competing with the adsorption sites, background salts through the double-layer compression effect, and the competition from soluble ions for the amine or amide functional groups on GO-PEI3. Finally, both the FT-IR and XPS results confirmed that the adsorption of PFOA onto GO-PEI3 was through electrostatic attraction and hydrophobic interaction (physical adsorption), but not chemical adsorption. This work provides fundamental knowledge both in understanding the adsorption behavior through the BET isotherm model and in developing a stable adsorbent for PFOA adsorption. In addition, the findings highlight the potential of PFOA remediation from wastewater systems using GO-PEI in engineering applications.

Chitosan impregnation of coconut husk biochar pellets improves their nutrient removal from eutrophic surface water

The presence of excess nutrients in water resources can be harmful to human health and aquatic ecosystems. To develop an affordable water treatment method, the agricultural waste material coconut husk was converted into a low-cost adsorbent by thermal conversion to biochar, pelletized without (CH), and with chitosan (CHC), or eggshell powder (CHEG) modifications. The physical and chemical properties of all adsorbents were characterized using Brunauer-Emmett-Teller (BET) surface analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, pHzpc, iodine number and elemental analysis. The adsorption of ammonium (NH4+), nitrate (NO3−), and phosphate (PO43−) in single and mixed solute solutions was investigated for initial concentrations of 10 mg L− 1. Langmuir, Freundlich, Sips, Dubinin-Radushkevich (D-R) and BET isotherm models were used to investigate the adsorption mechanisms. The maximum adsorption capacity of NH4+ on CH, CHC, and CHEG from mixed solute solution was 5.0, 4.7 and 5.9 mg g− 1, respectively, while the adsorption capacity of mixed:single solute solution was 0.95, 0.93, and 1.04, respectively. CH, CHC, and CHEG had greater ability to remove the cation NH4+ than anions NO3− and PO43− from aqueous solution. The highest maximum adsorption capacity for anions NO3− and PO43− was found on CHEG (1.7 mg g− 1) and CH (6.7 mg g− 1), respectively. NH4+ and NO3− were bound by chemisorption as indicated by D-R isotherm E values (> 8 kJ mol− 1), and enthalpy ∆H values (> 80 kJ mol− 1). In contrast, PO43− adsorption was mainly by physical interaction, including pore-filling, and electrostatic attraction. Pseudo first order and pseudo second order models provided good fits of the sorption kinetics data (R2 > 0.9). The initial concentrations of NH4+, NO3−, and PO43− in surface water sampled from a canal in Bangkok were 10.4, 1.2, and 3.9 mg L− 1, respectively, which indicated eutrophication. At a dose of 20 g L− 1, CHC achieved the best nutrient removal from this surface water, by 24% for NH4+, 25% for NO3−, and 66% for PO43− after 48 h contact, respectively.

Modification of halloysite nanotubes by hydroxyl terminated triazine‐based dendritic polymer for efficient adsorptive removal of Cd (II) from aqueous media

In the present study, the hydroxyl terminated triazine‐based dendritic polymer was synthesized and grown on the halloysite nanotubes surface (HNT‐G2) to efficiently remove the Cd (II) ions from aqueous solution. The nano‐adsorbent morphology and structure were determined through transmission electron microscopy, X‐ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analyzer, Brunauer–Emmett–Teller isotherm, and energy dispersive X‐ray spectroscopy analysis methods. The adsorption of Cd (II) has resulted a maximum of 105.26 mg g−1 at 298 K at optimal pH 6. As research revealed the adsorption kinetic followed the pseudo‐second‐order model, while the adsorption isotherms corresponded the Langmuir model. Accordingly, it could be inferred that the Cd (II) was a single‐layer adsorption occurring on the adsorbent surface, and further, the rate‐controlling step was denoted chemical adsorption. Also, the thermodynamic results showed that the adsorption process could occur spontaneously; therefore, it was considered as an endothermic reaction. Surprisingly, the adsorption and desorption efficiency after four cycles was high, while the Cd (II) adsorption mechanism affecting the adsorbent was basically via chelation through the O atoms. Hence, it can be concluded that the HNT‐G2 was effective in efficiently removing of Cd (II) from the aqueous solution, having high applicability significance.

Simultaneous removal of mercury ions and cationic and anionic dyes from aqueous solution using epichlorohydrin cross-linked chitosan @ magnetic Fe3O4/activated carbon nanocomposite as an adsorbent

An economical epichlorohydrin cross-linked chitosan @ magnetic Fe3O4/activated carbon nanocomposite, CH-EP@Fe3O4/AC, was successfully synthesized and used as a suitable adsorbent material for removal of a triphenylmethane cationic dye, Malachite green (MG), an anionic dye, Reactive red 120 (RR120), and Mercury ions (Hg2+) from aqueous solution. The prepared adsorbent has been characterized with Fourier transform infrared spectroscopy, X-ray diffraction, Scanning electron microscopy, Thermogravimetric analysis, Brunauer–Emmett–Teller analysis as well as Vibrating sample magnetometer. According to the result of Brunauer–Emmett–Teller isotherm, the prepared adsorbent has a specific surface area of 287 m2/g, which offers relatively high adsorption capacity for the dyes and heavy metal ions. The Box–Behnken design was employed to assist in the tuning of optimum adsorption conditions, such as dosage of adsorbent, solution pH and contact time. Under optimized conditions, kinetics results exhibited that the adsorption well fitted the pseudo-second-order model. The Langmuir isotherms fitted well with experimental data of Hg2+, MG and RR120 in single component solutions, which demonstrates adsorption is along with monolayer process. Also, the experimental data for adsorption of pollutants in binary and multicomponent solutions exhibited best fit with Freundlich model, which shows multilayer adsorption on the surface of the CH-EP@Fe3O4/AC adsorbent. The efficiency of removal towards Hg2+ ions in multicomponent solution (Hg2+/MG + RR120) exceeds 88% and the maximum adsorption capacity is 166.6 mg/g. In addition, the removal efficiency of towards MG in multicomponent solution (MG/RR120 + Hg2+) is about 81% with the maximum adsorption capacity of 146.3 mg/g and the removal efficiency and the maximum adsorption capacity of RR120 in that solution is 78% and 140.7 mg/g, respectively. Also, thermodynamic studies demonstrate that the adsorption of pollutants was spontaneous, that follow an endothermic way with an enhance in entropy. It was observed that the prepared adsorbent was stable after five runs of adsorption-desorption. Therefore, it was concluded that the prepared nanocomposite is a potential applicant for the adsorption of dyes and heavy metal ions from mixed aqueous solution.

From Langmuir isotherm to Brunauer–Emmett–Teller isotherm

AbstractDeveloped for multilayer adsorption, the Brunauer–Emmett–Teller (BET) isotherm considers the adsorption of the first layer as an equilibrium chemical reaction between adsorbate molecules and adsorption sites and the adsorption of the second and subsequent layers as a condensation–evaporation process. Following the recent development of an activity‐based formulation for the Langmuir isotherm for monolayer adsorption, we present an activity‐based formulation for the BET isotherm in which species concentrations are replaced with species activities. Capturing the adsorbent surface heterogeneity for the adsorption of the first layer, the resulting thermodynamic BET isotherm is shown to accurately represent pure component adsorption isotherms over the relative pressure range of zero to unity or prior to the onset of capillary condensation. The thermodynamic BET isotherm should facilitate accurate estimation of monolayer adsorption capacity and the corresponding adsorbent surface area.

Silver-Protein Nanocomposites as Antimicrobial Agents.

The use of nanomaterials alone or in composites with proteins is a promising alternative to inhibit pathogenic bacteria. In this regard, this study used seed proteins from both fenugreek (Trigonella foenum-graecum L.) (FNP) and mung bean (Viga radiate) (MNP), with silver nanoparticles (Ag-NPs) and nanocomposites of either Ag-NPs plus FNP (Ag-FNP) or Ag-NPs plus MNP (Ag-MNP) as inhibitory agents against pathogenic bacteria. FNP and MNP were isolated from fenugreek seeds and mung bean seeds, respectively, and fractionated using Sodium Dodecyl Sulfate–Polyacrylamide Gel Electrophoresis (SDS–PAGE). Both FNP and MNP were immobilized with Ag-NPs to synthesize the nanocomposites Ag-FNP and Ag-MNP, respectively. The physicochemical characteristics of Ag-NPs and their composites with proteins were studied by X-ray Diffraction (XRD), dynamic light scattering (DLS), the zeta potential, Scanning and Transmission Electron Microscopy (SEM and TEM, respectively), Atomic Force Microscopy (AFM), and the Brunauer–Emmett–Teller isotherm (BET), elucidating their structural parameters, size distribution, size charges, size surface morphology, particle shape, dimensional forms of particles, and specific surface area, respectively. The sole proteins, Ag-NPs, and their nanocomposites inhibited pathogenic Gram-positive and Gram-negative bacteria. The inhibitory activities of both nanocomposites (Ag-FNP and Ag-MNP) were more than those obtained by either Ag-NPs or proteins (FNP, MNP). Minimum inhibitory concentrations (MICs) of Ag-FNP were very low (20 and 10 µg mL−1) against Salmonella typhimurium and Pseudomonas aerugenosa, respectively, but higher (162 µg mL−1) against E. coli and Listeria monocytogenes. MICs of Ag-MNP were also very low (20 µg mL−1) against Staphylococcus aureus but higher (325 µg mL−1) against Listeria monocytogenes. TEM images of Staphylococcus aureus and Salmonella typhimurium, treated with Ag-FNP and Ag-MNP, at their MIC values, showed asymmetric, wrinkled exterior surfaces, cell deformations, cell depressions, and diminished cell numbers.

Use of corn straw-derived biochar for magnetic solid-phase microextraction of organophosphorus pesticides from environmental samples

In this study, the potentials of utilizing corn straw-derived biochar in environmental sample pretreatment were examined. An one-step magnetization and carbonization process was developed to prepare magnetic biochar by mixing corn straw powder with Fe2+/Fe3+ and then pyrolyzed at different temperatures (400–800 °C). The obtained magnetic biochars were characterized by using scanning electron microscopy, Brunauer–Emmett–Teller isotherms, X-ray diffraction and Fourier transform infrared spectroscopy. Various extraction affecting parameters, such as Fe2+/Fe3+content, pyrolytic temperature, species of desorption solvent, extraction and desorption time, respectively, were studied and optimized. Results showed that the magnetic biochar pyrolyzed at 700 °C exhibited the best extraction performance, with enrichment factors ranging from 52 to 210, presumably due to H-bonding and π-π interactions between biochar and organophosphorus, as well as to the high surface area and pore volume of biochar. The magnetic biochar-based extraction was further combined with gas chromatography–mass spectrometry (GC/MS) to analyze trace organophosphorus pesticides from environmental samples. The method demonstrated good linearity (0.1–50 µg·L−1), low limits of detection (0.02–0.11 µg·L−1), and high recoveries (72.4–96.8%) from spiked water and soil samples. The results of this study suggested the promising potentials of utilizing corn straw-derived biochar for efficiently enriching trace organophosphorus pesticides from complex environmental samples.

Magnetic Cellulose-Chitosan Nanocomposite for Simultaneous Removal of Emerging Contaminants: Adsorption Kinetics and Equilibrium Studies

The presence of pharmaceuticals in water systems threatens both terrestrial and aquatic life across the globe. Some of such contaminants are β-blockers and anticonvulsants, which have been constantly detected in different water systems. Various methodologies have been introduced for the removal of these emerging pollutants from different waters. Among them, adsorption using nanomaterials has proved to be an efficient and cost-effective process for the removal of pharmaceuticals from contaminated water. In this this study, a firsthand/time approach applying a recyclable magnetic cellulose-chitosan nanocomposite for effective simultaneous removal of two β-blockers (atenolol (ATN)) and propranolol (PRP) and an anticonvulsant (carbamazepine (CBZ)) is reported. A detailed characterization of the eco-friendly, biocompatible cellulose-chitosan nanocomposite with magnetic properties was performed at various rates of synthesis using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and Fourier transform infrared (FTIR) spectroscopy. A N2c adsorption-desorption test showed that the prepared nanocomposite is mesoporous, with a BET area of 112 m2 g−1. The BET isotherms results showed that the magnetic cellulose-chitosan nanocomposite has a pore size of 24.1 nm. The adsorption equilibrium of PRP and CBZ fitted with the Langmuir isotherm was consistent with the highest coefficient of determination (R2 = 0.9945) and (R2 = 0.9942), respectively, while the Sips model provided a better fit for ATN, with a coefficient of determination R2 = 0.9956. The adsorption rate was accompanied by a pseudo-second-order kinetics. Moreover, the swelling test showed that up to 100 percent swelling of the magnetic cellulose-chitosan nanocomposite was achieved.

Carbon nitride nanosheets magnetically decorated with Fe3O4 nanoparticles by homogeneous precipitation: Adsorption-photocatalytic performance and acute toxicity assessment

In the present study, graphitic carbon nitride (g-C3N4) was decorated with Fe3O4 nanoparticles by using an alternative, simple and environmentally friendly method of homogeneous precipitation with urea. The magnetic nanocomposite was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM-EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller isotherms (BET), Zetametry, vibrating sample magnetometry, UV–vis absorption spectroscopy, and photoluminescence spectroscopy (PL). The acute toxicological effects of nanomaterials were evaluated in embryos/larvae of the zebrafish (Danio rerio). The performance of the nanocomposite for removal of methylene blue (MB), as a model pollutant, from water in different pH conditions was compared to that of pure g-C3N4 and a magnetic composite elaborated using conventional coprecipitation with NH4OH. The results showed that the nanocomposite synthesized with the new approach showed the best performance, corresponding to a removal rate of 98.3% in the alkaline medium. Regeneration studies showed that the proposed nanocomposite can be easily recovered by magnetic assistance and can be reused, keeping a good removal efficiency. The toxicological results showed that nanomaterials, pure and decorated, presented no acute toxicological effects in zebrafish at the concentrations recommended by OECD 236.

Eco-friendly synthesis of the Li/Al in nonionic surfactant-based vesicles (niosomes) modified with graphene oxide quantum dot nanostructures for controlled released of chlorpheniramine maleate.

The aim of the present work was the preparation of Li/Al nanoparticles (NPs) functionalized with graphene oxide quantum dots (GOQDs) for the controlled release of chlorpheniramine maleate (CPAM). The role of lemon and egg white extracts as oxidation agents were investigated for the morphology and particle size of the products. GOQDs were synthesized using green, environmentally friendly, and cost-effective precursors. This work demonstrates that Li/Al NPs functionalized with graphene oxide as a nanolayer structure can be used as efficient nanocarriers for loading and delivery of CPAM as water-insoluble aromatic drugs The final products were identified with X-ray diffraction, scanning electron microscopy, atomic force microscopy, ultraviolet-visible spectroscopy, dynamic light scattering, thermogravimetric analysis, and transmission electron microscopy nitrogen adsorption [i.e. Brunauer-Emmett-Teller (BET) surface area analysis] techniques. The calibration curve for Li/Al nanoparticles functionalized with GOQDs for controlled released of CPAM was calculated as y = 0.0137x + 0.0103 with R2 = 0.9995. The data found through BET and Barrett-Joyner-Halenda analysis using the adsorption/desorption isotherm method demonstrated by total pore volumes and dead volume were calculated respectively as 0.162 nm2 , 0.0439 cm3 g-1 . The mean pore diameter was calculated as 20.33 nm using BET isotherm data.