Nonlinear Isotherm Research Articles

Targeting Mycobacterium tuberculosis Parallel G-Quadruplex Motifs with Aminoglycosides Neomycin and Streptomycin: Spectroscopic and Calorimetric Aspects.

Mycobacterium tuberculosis (Mtb) contains potential G-quadruplex (PGQ) motifs in the genes espK and cyp51, which are crucial for the bacteria's virulence within host cells. Aminoglycoside molecules are commonly used as antibiotics for ribosomal targets. This study provides insight into the interactions between these aminoglycosides and Mtb-PGQ sequences (espK and cyp51), shedding light on the structural and thermodynamic dynamics of their binding. This study demonstrates the stability, affinity, and conformation of Mtb-PGQ in the presence of neomycin and streptomycin. Ultraviolet-visible spectroscopy (UV-vis), circular dichroism spectroscopy (CD), CD thermal melting, isothermal titration calorimetry (ITC), and fluorescence intercalator displacement (FID) assays were used to comprehensively examine these interactions. Our results reveal that neomycin with Mtb-PGQexhibits hypochromism accompanied by a 4-5 nm red shift in the UV-visible absorption titration, whereas streptomycin exhibits a hypochromic shift without changes in the maximum wavelength. Notably, neomycin shows a nonlinear binding isotherm, suggesting the involvement of more than one binding process in the formation of neomycin.Mtb-PGQ complexes. Scatchard plot analysis indicates higher binding affinity values for neomycin compared with weaker affinity of streptomycin. CD studies reveal that neomycin decreases the ellipticity of Mtb-PGQ with a red shift while retaining the parallel topology, ultimately enhancing the thermal stability of both espK and cyp51. In contrast, streptomycin destabilizes the cells. ITC analysis reveals that neomycin exhibits the strongest binding affinity for cyp51, with the relative order being NEO-cyp51 > NEO-espk > STR-cyp51 > STR-espk. Moreover, thermodynamic analysis reveals that neomycin possesses a unique dual mode of binding through grooves as well as stacking. FID studies further confirm a lower DC50 value for neomycin than for streptomycin, suggesting that neomycin is a strong displacer of thiazole orange. Thus, the results show that neomycin with amino groups selectively recognizes the grooves of cyp51 over espK.

Cost-effective adsorption of cationic dyes using ZnO nanorods supported by orange peel-derived carbon.

Here, porous carbon (PC) and ZnO nanorods@PC (ZnO-NR@PC) composite derived from orange peel (OP) have been synthesized via a simple carbonization process. The prepared materials have been characterized by XRD, FT-IR, TEM, and BET analysis. The adsorptive properties of the prepared PC and ZnO-NR@PC composite have been investigated toward methylene blue (MB) and crystal violet (CV) cationic dyes from their aqueous solutions. The adsorption studies concluded that the maximum adsorption efficiency was achieved after 90min in the basic conditions (pH = 10). Langmuir, Freundlich, Dubinin-Radushkevich (D-R), and Temkin non-linear isotherm models were applied to fit the experimental data. The adsorption of MB and CV dyes by the OP is fitted with the Freundlich model, and the adsorption of both dyes by the PC and the ZnO-NR@PC composite fitted with the Langmuir model. The estimated maximum adsorption capacity estimated from the adsorption of MB and CV by the ZnO-NR@PC composite was 74.45 and 74.89mg/g, respectively. The calculated adsorption free energy from D-R and Temkin models indicates the adsorption of MB, and CV dye molecules by the OP, PC, and ZnO-NR@PC composite may be physical. The kinetic studies revealed the adsorption of MB and CV dyes onto the OP, PC and ZnO-NR@PC composite fitted with the pseudo-second-order model. On the otherhand, the thermodynamic studies confirmed the adsorption of MB, and CV dyes onto ZnO-NR@PC composite is an endothermic and spontaneous process. Furthermore, the prepared materials displayed high adsorption stability with an overall removal efficiency of about 90% after five cycles. The mechanism of MB and CV dyes by the ZnO-NR@PC composite is proposed to be controlled by electrostatic bonding, π-π interactions, and ion exchange. The results indicated the potential ability of OP-derived porous carbons as adsorbents for cationic dyes from aqueous media.

The Synthesis of Functionalized W5O14 Nanorods for the Adsorption of Bismarck Brown R from Wastewater

In this research, a tungsten oxide was prepared via a green (biogenic) synthesis route where sodium tungstate dihydrate and Punica granatum peel extract were used as a precursor and a reducing/capping agent, respectively. The characterization of the prepared tungsten oxide was performed through various spectroscopic and microscopic techniques. The characterization results revealed the preparation of highly crystalline and nanorod-shaped (length = 123 nm and width = 31.3 nm) tungsten oxide with a probable chemical formula of W5O14. Various functional groups on the W5O14 surface were also reported. The prepared nanorods were further used for the removal of Bismarck Brown R (BBR) dye from water in a batch manner. By varying the dose of nanorods (0.5–3.0 g L−1), BBR solution pH (2−10), contact time (15–120 min), BBR concentration in solution (10–60 mg L−1), and temperature of BBR solution (30, 40, and 50 °C), the optimized condition for maximum adsorption efficiency was measured. The results revealed that 2.0 g L−1 amount of nanorods of tungsten oxide were used to remove ~98% of BBR dye from its 10 mg L−1 at 30 °C and 7.0 pH. The temperature-dependent adsorption data were fitted to different types of non-linear isotherm models (e.g., Langmuir and Freundlich) to assess the adsorption potential and adsorption mechanisms in relation to temperature impacts. The synthesized nano-adsorbent fits the Langmuir as well as the Freundlich isotherm model with a maximum adsorption capacity of 17.84 mg g−1. Pseudo-first-order, pseudo-second-order, and Elovich kinetic models were used for the study of adsorption kinetics. BBR adsorption onto the W5O14 nanorods follows the pseudo-second-order rates. The present adsorption is governed by physico-chemical adsorption with predominant chemical interactions.

Algal biochar: A natural solution for the removal of Congo red dye from textile wastewater

The present study was aimed at synthesizing algae-derived biochar to examine its effectiveness and adsorption capacity to remove Congo red dye. The independent variables such as dye concentration, adsorbent dose, and adsorption time were optimized by using a central composite design (CCD). An adsorption experiment was conducted to evaluate equilibrium using a detailed experimental design and characterized through XRD, TGA, SEM, EDX, and FTIR analysis. This paper also focuses on evaluating non-linear adsorption isotherm and kinetics to describe the adsorption mechanism along with applying an Artificial neural network to validate the removal efficiency. The maximum Congo red removal efficiency (96.14 %) and maximum adsorption capacity of algal biochar (186.94 mg/g) were achieved with the optimized parameters of 1 mg/L of dye concentration, 0.1 g of adsorbent dose, and 240 min of contact time. Adsorption behavior was well described by Langmuir isotherm and Pseudo-nth order. A multilayer perceptron (MLP) MLP 2–5–1 structure best validates the response. Overall, the study sheds light that Algal-derived biochar is a potential material for the elimination of Congo red dye and contributes to achieving sustainable development goals.

Adsorptive performance of bismuth-doped Ni-Zn-Co ferrite nanoparticles for the removal of methylene blue dye.

Cancer, kidney and liver damage, and even death result from water contaminated with textile dyes. This study highlighted a key approach for treating water contaminated with methylene blue (MB) dye. Bismuth-doped ferrite nanoparticles (Ni0.33Zn0.33Co0.33-xBixFe2O4) with 0 ≤ × ≤ 0.2 were synthesized using a chemical co-precipitation technique. For the structural analysis, X-ray diffraction (XRD) confirmed the successful formation of ferrite nanoparticles with a hematite phase of 21.02% for x = 0.2. The crystallite size decreased from 30.12 to 13.65 nm, as x increased from 0 to 0.2. Also, a decrease in the grain size from 24.57 to 12.37 nm was verified via transmission electron microscope (TEM) analysis. Furthermore, the X-ray photoelectron spectroscopy (XPS) confirmed the optimal stoichiometric proportions of the synthesized nanoparticles through the elemental composition analyzed. Additionally, XPS analysis revealed that the un-doped sample has gained the highest number of defects along with the photoluminescence spectra (PL) discussion. The optical analysis was investigated by photoluminescence spectra (PL) through several excitation wavelengths. The detected PL peaks in the near-band energy and the defect-level emission region confirmed the recombination rate and the presence of defects, respectively. Doping ferrite nanoparticles with bismuth increased the specific surface area from 43.82 to 71.83 m2·g-1 and altered pore volume and diameter. For further investigation, the adsorption performance of ferrite nanoparticles was tested using MB as a pollutant. Un-doped nanoparticles demonstrated significant adsorption activity, removing 97.1% of MB after a contact time of 120 min. Furthermore, un-doped nanoparticles exhibited improved adsorption activity in a basic medium, while Bi-doped nanoparticles showed enhanced performance in an acidic medium. This result was due to Bi-doping altering the surface charge, as confirmed by zeta potential analysis. Among the applied non-linear isotherms, the Freundlich model best described the adsorption of MB onto the Ni0.33Zn0.33Co0.33-xBixFe2O4 nanoparticles. Increasing the temperature boosted the adsorption of MB onto the prepared nanoparticles.

Dibutyltin dilaurate catalysed guar gum and toluene diisocyanate polyurethane foam for the removal of malachite green from wastewater

AbstractIn view of the huge potential in various applications, biopolymer‐based polyurethane foams (PUF) are attracting researchers. In the present study, we report the modification of guar gum (GG) via polyaddition reaction with toluene diisocyanate (TDI) using dibutyltin dilaurate as catalyst, silicone oil as surfactant and calcium carbonate as filler to form GG‐PUF. The as‐synthesized GG‐PUF was characterized by Fourier transform infrared (FTIR), XRD, field emission SEM, energy‐dispersive X‐ray spectroscopy, and surface charge analysis. In the FTIR spectrum of GG‐PUF, peaks at 3290, 1705, 1595, and 1510 cm−1 are attributed to stretching vibrations of –NH, –C=O, –C=C– of the benzene ring of TDI, and the –NH bending vibration of the urethane group, respectively. The XRD patterns of GG and GG‐PUF indicate their semicrystalline and amorphous nature, respectively. The field emission SEM of GG‐PUF exhibits high porosity compared to the smooth surface of GG due to the evolution of CO2 gas during the foaming reaction. The GG‐PUF was evaluated as an adsorbent for cationic dyes from wastewater. The preliminary adsorption studies showed maximum adsorption for malachite green with 93.54% removal at 40 °C and pH 6.0 in 60 min. The adsorption mechanism was studied by various nonlinear kinetic models, namely the pseudo‐first order, pseudo‐second order and Elovich, and nonlinear isotherm models, such as Langmuir, Freundlich and Temkin. The adsorption followed pseudo‐secondorder kinetics and a Langmuir isotherm with a maximum adsorption capacity of 156.44 mg g−1. The small value of the error function (χ2) and normalized standard deviation (Δq%) from nonlinear models indicated the better fitting of the data into nonlinear kinetics and isotherm models. Furthermore, GG‐PUF showed substantial degradability under simulated wastewater conditions at acidic and alkaline pH and reusability up to 10 adsorption–desorption cycles. Hence, GG‐PUF has tremendous potential as a sustainable, economical and environmentally friendly adsorbent for eliminating cationic dyes from wastewater. © 2024 Society of Chemical Industry.

Investigation of Remazol Brilliant Blue R removal in batch and fixed bed column reactor systems by MnOx: Non-linear isotherm and kinetic modelling

Remazol Brilliant Blue R (RBBR) is a dye frequently used in the textile industry. Discharging industrial effluents containing dye residues could pose a risk to biological systems. In the present study, the removal of RBBR from aqueous solutions was tested using MnOx in both batch and continuous systems. The effects of various parameters, including the solution’s initial pH, the amount of MnOx, the initial RBBR concentration, and temperature on RBBR removal by MnOx, were investigated. The optimum pH and MnOx amount at an initial RBBR concentration of 50 mg/L and 30°C were pH 7 and 0.3 g/L, respectively, resulting in an RBBR removal efficiency of 94.43 %. The adsorption capacity was found to be 227.06 mg/g at an initial RBBR concentration of 100 mg/L, pH 7, and 30°C. The adsorption process best fit the non-linear Langmuir isotherm and Elovich kinetic models, with the least error distributions and it was characterized as exothermic and spontaneous. The activation energy value was calculated to be 92.06 kJ/mol. In the fixed bed column reactor, the equilibrium uptake (qe) was 196.30 mg at an RBBR concentration of 200 mg/L and a flow rate of 3.70 mL/min. The results imply that MnOx shows great promise for wastewater treatment contaminated with dyes.

Evaluation of ZnO/NiO/kaolin nanocomposite as a sorbent/photocatalyst in hybrid water remediation process

The colored effluents causing environmental pollution pose a threat to the world. This study aims to assess the effectiveness of nickel oxide/zinc oxide/kaolin nanocomposite (NiO/ZnO/Ka) in removing methylene blue (MB) from water. Furthermore, it aims to examine the impact of synergetic adsorption/photocatalytic degradation (APCD) on the MB adsorption capacity as well as the suitability of the nonlinear adsorption isotherm and kinetic modeling in analyzing the process. The composites ZnO/Ka and NiO/ZnO/Ka were synthesized by the sol–gel method and were characterized by X-ray diffraction, Fourier transform infra-red, field emission scanning electron microscopy, and Brunauer–Emmett–Teller. The impacts of various parameters, such as pH, initial concentration of MB, dose, ionic strength, and temperature, on MB removal were studied using adsorption and APCD. The results showed that ZnO/Ka had the maximum adsorption capacity of MB (39.31 mg/g) and the maximum removal (78.61%) under optimal conditions of pH 10, clay dosage of 0.1 g/25 mL, initial concentration of MB 200 mg/L, contact time of 15 min, and 298 K, while NiO/ZnO/Ka showed the maximum adsorption capacity of MB (40.88 mg/g) and maximum removal (83.74%) at pH 7. It was also noticed that Temkin and Fritz–Schlunder models are the best isotherm models, with the highest R2 (1 and 0.842) for ZnO/Ka and NiO/ZnO/Ka, respectively. Moreover, the data of adsorption and photodegradation of MB onto ZnO/Ka and NiO/ZnO/Ka were revealed to follow pseudo-first-order and Avrami kinetic models with R2 (0.897) for ZnO/Ka and (0.986) for NiO/ZnO/Ka. Overall, NiO/ZnO/Ka showed better removal of MB than ZnO/Ka, and the hybrid process (photodegradation process after adsorption) enhanced the overall efficiency of MB removal than adsorption alone.

Magnetic carrageenan gum-grafted-polyacrylamide nanocomposite for uptake of cationic dyes from the aquatic systems

Using an ex-situ growth approach, this research fabricated k Carrageenan/Polyacrylamide@magnetite nanocomposites (NCs), (k-Car/PAM@Magnetite NCs). The k-Carrageenan (k-Car) backbone was modified through graft polymerization of acrylamide (PAm) via radical polymerization using ammonium persulfate (APS) as the initiator. N'-N' methylenebisacrylamide (MBAA) was used as the cross-linking agent, and magnetic nanoparticles (MNPs) were incorporated to impart magnetic properties. The successful synthesis of the k-Car/PAM@Magnetite NCs was confirmed through various analyses, including FT-IR, FESEM, EDS, XRD, VSM, BET, TGA, and Zeta. The adsorption effectiveness of the NCs for removing methylene blue (MB) and rhodamine B (RhB) from wastewater was evaluated by optimizing experimental parameters such as pH, adsorbent dosage, agitation time, and initial dye concentration. The NCs demonstrated a maximum adsorption capacity according to the Langmuir Isotherm (Qmax) of 204.082 mg. g−1 for MB and 200 mg.g−1 for RhB using 0.004 g of NCs.The adsorption data fit the Freundlich non-linear isotherm model well, and the kinetic data followed a pseudo-second-order (PSO) model. It is evident from the thermodynamic parameters that adsorption is an endothermic process that is spontaneous and favourable. The k-Car/PAM@Magnetite NCs also exhibited excellent regeneration capabilities, maintaining high adsorption efficiency after three consecutive adsorption-desorption cycles.

Simulation of Nonlinear and Nonisothermal Reactive Liquid Chromatography considering Finite Mass-Transfer Rates and Various Adsorption Scenarios.

A multicomponent nonisothermal lumped kinetic model (LKM) of fixed-bed liquid chromatographic reactor is introduced and numerically approximated. The model incorporates nonlinear Bi-Langmuir and Toth adsorption isotherms, reaction kinetics, axial and temporal variations of concentrations, and enthalpies of reaction and adsorption. The resulting model equations constitute a nonlinear coupled system of convection-diffusion-reaction partial differential equations (CDR-PDEs) for mass and energy balances in both the mobile and stationary phases, augmented by differential mass balances in the stationary phase and algebraic expressions for reaction rates and adsorption isotherms. Due to the nonlinearity of adsorption isotherms and reaction kinetics, which is impeding the derivation of closed-form solutions, a local-projection discontinuous Galerkin finite element (DG-FE) method is applied for space discretization. The emerging semidiscrete system of ordinary differential equations in time is solved numerically by employing a total variation bounded (TVB) Runge-Kutta method. To analyze the process performance, parametric studies are conducted using numerical simulations. A series of rigorous consistency tests are elucidating the interplay between thermal and concentration gradients, showcasing the impact of temperature on reactor performance, and highlighting the aspects of reactant conversion into products. Subsequently, a thorough comparison is performed among the considered adsorption isotherms to scrutinize the numerical findings and to augment the originality of research. The results obtained verify the validity of model equations and precision of the numerical technique used. Moreover, the outcomes of this study can be utilized to understand mass and energy distributions in nonequilibrium and nonisothermal liquid chromatographic reactors and to provide profound insights into the complexities of this separation-conversion process.

Synthesis of "Ice Cube" Shaped Zeolite A Type and Cu2+ Ion-Exchanged Zeolites and Study of Their CO2 Adsorption Performance.

In this study, zeolite type A and four Cu2+ ion-exchanged zeolites were synthesized through cationic ion exchange process with Cu concentrations of 0.05, 0.1, 0.15, and 0.2 M respectively. The physicochemical properties of both the prepared and ion-exchanged zeolites were thoroughly analyzed. Field Emission Scanning Electron Microscopy (FESEM) micrographs revealed that the synthesized zeolites exhibited an "ice cube"-shaped morphology, and this morphology was maintained even after the ion exchange process. N2 adsorption/desorption studies indicated a typical type IV isotherm with an H3 hysteresis loop for both the prepared and Cu2+ ion-exchanged zeolites. CO2 adsorption data followed a type I isotherm, with the highest adsorption capacity of 4.02 mmol/g observed for the 0.1 M Cu2+ ion-exchanged zeolites. The adsorption behavior was modeled using a nonlinear isotherm, with good agreement between experimental and fitted data.

Efficient separation of cerium from rare earth elements and major impurities using low cost manganese ferrites from highly acidic solutions

Sorption of REEs using spinel-ferrite nanoparticles has received great attention in the last decades, because of combining the advantages of iron and manganese metal oxides. Nano-manganese ferrite (MnFe2O4) was successfully synthesized using the co-precipitation method and modified with the addition of zinc to produce (Mn0.8Zn0.2Fe2O4). The synthesized materials were characterized using FTIR, SEM with EDX-mapping, XRD, chemical stability, and surface area. Several process parameters were studied to optimize the efficiency of Ce(III) separation from La(III), Eu(III), Pb(II), and Fe(III) from highly acidic media. The parameters include contact time, solution pH, and metal ion concentration. The sorption process was well fitted to the pseudo-2nd order model, which confirms the chemical nature of the sorption process where equilibrium was achieved after 30 minutes. The pH study's findings demonstrate that Ce(III) was most effectively separated at a very high, acidic pH of 0.5. Both MnFe2O4 and Mn0.8Zn0.2Fe2O4 have high chemical stability in different media where the weight loss was less than 10 %. The correlation coefficient and residual errors analysis confirm that the non-linear extended sips isotherm model more accurately expresses the behavior of the sorption process than the non-linear Freundlich and Langmuir isotherm models. The modified material Mn0.8 Zn0.2Fe2O4 shows higher sorption capacities for all the studied metal ions than MnFe2O4. The maximum sorption capacities of Ce(III), La(III), Eu(III), Pb(II), and Fe(III) in the mixture were 59.2, 6.5, 6.3, 15.4, and 13.7 mg/g, respectively.

Elimination of methylene blue dye from the aqueous solution using waste fig fruit as an activated carbon: a case study of nonlinear adsorption isotherm models and kinetic models

Elimination of methylene blue dye from the aqueous solution using waste fig fruit as an activated carbon: a case study of nonlinear adsorption isotherm models and kinetic models

Modeling of adsorptive treatment of lead (II) ions contaminated effluents using cashew nut shell alkali activated carbon: Batch kinetic, isothermal and thermodynamic studies

The numerical study of the decontamination of lead(II) ions-rich effluent employing activated carbon derived from cashew nut shell was the central focus of this work. Chemical activation with zinc chloride (ZnCl2) was used to produce powdered activated carbon at optimized activation conditions of impregnation ratio (0.531), activation temperature (1083 K) and activation time (63min). The physiochemical properties of raw and activated cashew nut shell were determined using Fourier transform infrared spectroscopy, scanning, X-ray diffractor (XRD), scanning electron microscopy (SEM), and Brunauer-Emmet-Teller (BET) analyses. Batch adsorption experiments were performed at varied process conditions of temperature (303–323) K, contact time (5–80min), and initial lead(II) ion concentrations (100–400 mg.L−1). The adsorption behavior of the batch–type operation was mathematically described in the form of non-linear parabolic partial differential equations (PDE’S) incorporating film, pore and surface diffusion mechanisms. The batch mathematical model was solved by implementing a custom MATLAB program-OkiyNwabannebatch and calibrated to predict the desired response (percentage removal) using measured adsorption data. The equilibrium adsorption, kinetics and thermodynamics of lead(II) ions adsorption onto activated cashew nut shell were also assessed using nonlinear isotherm, kinetic and thermodynamic models. Sensitivity analysis unveiled that temperature with sensitivity value of 37.31 % had a predominant effect on the model performance. The simulated equilibrium data was well explicated by the Freundlich model for lead(II) ions adsorption onto activated cashew nut shell. The pseudo-second order kinetic model best reproduced the simulated adsorption data for lead(II) ions uptake by cashew nut shell adsorbent. Likewise, the kinetic data followed Boyd model, indicating that the adsorption process is controlled by external (film) diffusion for the uptake of lead(II) ions by alkali activated cashew nut shell. Thermodynamic analysis using the Gibbs and Van’t Hoff’s models indicated that lead(II) ions adsorption by modified cashew nut shell is spontaneous and exothermic. The physical nature of the adsorption process was elucidated from the low values of the isosteric heats of adsorption (ΔHX) evaluated (<80 kJ mol−1). This study showed that zinc chloride activated cashew nut shell has good potential to be used as a cost-effective and efficient adsorbent for the uptake of lead(II) ions from aqueous solution.

Facile preparation of multifunctional cellulose nanocrystals from coffee residue via hydrothermal technique: Prolific roles on the water purification, antibacterial and antifungal applications

In this work, the facile preparation of coffee residue (CR)-derived multifunctional cellulose nanocrystals (CNCs) via hydrothermal technique has been successfully attempted. The morphological structure, functionality, crystalline pattern, surface chemistry, elemental content and surface charge were evaluated. The adsorptive property was assessed using both anionic and cationic aqueous pollutants, chlorpyrifos and methylene blue (MB), and simulated by the non-linear isotherm models and kinetic equations. Its unique antibacterial and antifungal functions were tested against both gram-negative/positive bacterial and fungal species. The particle length and diameter, aspect ratio, crystallinity index, sulfate group content and zeta potential of this newly prepared rod-shaped CNCs were identified to be 432.39 nm, 23.57 nm, 18.34, 75.0 %, 0.21 mmol/g and −32.7 mV, respectively. CR-CNCs recorded an outstanding adsorptive feature for both MB and chlorpyrifos, with the monolayer adsorption capacities of 403.02 mg/g and 159.75 mg/g, respectively. The adsorptive uptakes could be effectively preserved via solvent regeneration technique, even after 5 adsorption-desorption runs. Excellent inhibition efficiencies against both gram-negative/gram-positive bacteria, and fungal species have been detected, with the growth-inhibition zones ranging from 10.9 to 26.7 mm. The novel protective roles of the newly prepared CR-CNCs against both biological and water contaminants have been well-elucidated.

Utilization of organic waste from Chinar leaves as sustainable and eco-friendly adsorbent for fluoride removal.

Due to concerns about high water fluoride concentrations and their detrimental consequences on health, particularly dental and skeletal fluorosis, dependable and cost-effective defluoridation techniques are needed. Chinar leaves (Platanus orientalis), a common waste, might be utilized for the production of activated carbon. For Chinar leaf activated carbon (CLAC) manufacturing, two pre-pyrolysis chemical modification procedures were used: acidic HCl (H-activation) and alkaline NaOH (OH-activation). The success of fluoride removal suggests further research and implementation in locations with fluoride-related water quality issues. This study examines how CLAC dosage, fluoride concentration, temperature, pH, and contact exposure effect defluoridation efficiency. The pseudo-second-order non-linear kinetic model and Freundlich non-linear isotherm model with R2 = 0.99 fit the data, resulting in a peak adsorption capacity of 30.3mg/g for 0.3g CLAC. In the present work, the adsorption mechanism was regulated by more than intraparticle diffusion. Adsorption occurred spontaneously as exothermic monolayer chemisorption, according to thermodynamic studies. Adsorbent activated with HCl (H-activated) showed promising results, with 73% F- removal efficiency for OH-activated and 91% for H-activated CLAC.

Analytical Solutions for a Fully Coupled Hydraulic‐Mechanical‐Chemical Model With Nonlinear Adsorption

ABSTRACTAdsorption characteristics play a crucial role in solute transport processes, serving as a fundamental factor for evaluating the performance of clay liners. Nonlinear adsorption isotherms are commonly found with metal ions and organic compounds, which introduce challenges in obtaining analytical solutions for solute transport models. In this study, analytical solutions are proposed for a fully coupled hydraulic‐mechanical‐chemical (HMC) model that accounts for both the Freundlich and Langmuir isotherms. To mitigate the difficulties arising from the variable coefficients, the system of second‐order partial differential equations involving three variables is linearized. The method of separation of variables, theory of integration, and Fourier series are utilized to derive analytical solutions. The analytical method presented can potentially be extended to a broad spectrum of nonlinear adsorption isotherms. The results reveal a 56.5% reduction in solute breakthrough time under the Freundlich isotherm and a remarkable 2.6‐fold extension under the Langmuir isotherm when compared to the linear isotherm. The adsorption constants of the Freundlich and Langmuir isotherms exhibit a positive correlation with breakthrough time, while the exponent of the Freundlich isotherm and the maximal adsorption capacity in the Langmuir isotherm demonstrate a negative association with breakthrough time. This study enhances the precision of solute transport prediction and provides a more scientific assessment of clay liner performance.

Alginate-Based Hydrogel Bead Reinforced with Montmorillonite Clay and Bacterial Cellulose-Activated Carbon as an Effective Adsorbent for Removing Dye from Aqueous Solution.

According to environmental concerns related to water pollution, this study aims to develop a novel hydrogel bead as a biocompatible and efficient adsorbent by integrating bacterial cellulose-activated carbon (BCAC) and montmorillonite (MT) in alginate hydrogel (ALG). The ionotropic gelation method was applied to the fabrication of BCAC/MT/ALG hydrogel beads. The BCAC/MT/ALG hydrogel bead exhibited significantly higher tensile strength, Young's modulus, and thermal stability, with ~1.4 times higher adsorption uptake of methylene blue (MB) from aqueous solution as compared to the pristine ALG bead. The textural properties, including specific surface area and porosity, were beneficial to accommodate the size of cationic MB as the target molecule. This resulted in a remarkable MB adsorption uptake of 678.2 mg/g at pH 7 and 30 °C. The adsorption isotherm showed the best fit for the nonlinear Redlich-Peterson isotherm model. Experimental adsorption data were well-described by the pseudo-second order kinetic model, with R2 values reaching 0.997. In addition, the adsorbent bead demonstrated easy regeneration with high reusability with approximately 75% of MB removal after being used for six cycles. Therefore, BCAC/MT/ALG bead represents an eco-friendly, cost-effective, and highly efficient adsorbent for MB removal from water and could potentially be used for removal of a wide range of cationic dye pollutants from wastewater.

Synthesis, characterization, and optimization of dual‐responsivePAMAMnanodendrimers for improved dispersive solid‐phase extraction of cancer agents from complex biological samples

AbstractLevels of anticancer agents in cancer patients' body fluids are typically measured to adjust drug dosages or improve treatment results. The goal of this research is to present a new method for extracting bicalutamide (BCT) from biological samples using a responsive polymeric nanoadsorbent that reacts to temperature and near‐infrared radiation (NIR). To achieve this, the surface layers of tungsten disulfide nanosheets are modified using poly (N‐vinylcaprolactam) and three generations of polymeric dendrimers. The adsorbent product is then characterized using thermogravimetric analysis, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, and X‐ray diffraction techniques. The drug loading operation on the proposed adsorbent is studied through central composite design and response surface strategy, with optimization for temperature (25–45°C), pH (5–9), and contact time (2–18 min). Nonlinear kinetic and adsorption isotherm analysis results show the best fit with Langmuir and pseudo‐second‐order models. The drug release process from the BCT‐loaded adsorbent is investigated via an HPLC‐UV system under both NIR‐irradiated and non‐irradiated conditions. The suggested method demonstrates remarkable recovery rates for BCT spikes from urine (95.23%) and plasma (93.33%), respectively. Overall, the recommended strategy can be regarded as a potent analytical tool for evaluating BCT in complex biosamples.

Gentian violet adsorption on a super magnetic nanocomposite (Fe2O3/Bentonite), non-linear kinetic and isotherm modeling

The health of humans may be at risk from textile wastewater's harmful dye effluents. Searching for effective and inexpensive adsorbents to treat these contaminated waters has attracted a lot of interest over the years. This work aimed to prepare a super nanocomposite based on raw bentonite to remove a cationic dye (gentian violet) from wastewater. Raw and Magnetic bentonite have been characterized using X-ray diffraction (XRD) and X-ray fluorescence (XRF). The specific surface area calculated by BET transform for both adsorbents show a high specific area for magnetic bentonite, four times higher than the raw one, it is estimated to 10.3452 and 41.6073 m2. g-1 for raw and magnetic bentonite respectively. A UV-Vis spectrophotometer has also characterized the gentian violet dye (GV). Kinetic non-linear models confirm that the adsorption phenomena are well modeled by the pseudo second order model, and thermodynamic studies show that it is also a spontaneous, endothermic, and inorganized process. The non-linear adsorption isotherm results were best fitted using the Langmuir isotherm, which refers to monolayer adsorption. The effect of some parameters, such as adsorbent mass, temperature, and contact time, has also been optimized. From these results, we concluded that supporting iron oxide on bentonite can increase the adsorption capacity, with a maximum Langmuir monolayer adsorption capacity qm= 137.39 mg. g-1.