Isotherm Studies Research Articles

Highly efficient removal of adsorbed cationic dyes by dual-network chitosan-based hydrogel

This research presents the effective preparation of a novel dual network chitosan-based hydrogel (CMAPP) for the adsorption of methylene blue (MB), malachite green (MG), crystalline violet (CV), and basic fuchsin (BF) using the sol-gel method to address the escalating issue of dye pollution. FTIR, XRD, SEM, EDS, XPS, TGA, and zeta potential study examined hydrogel production and physicochemical properties. To ascertain the maximum adsorption capacity, the influences of pH, temperature, initial dye concentration, contact time, and adsorbent dosage on adsorption were systematically analyzed. It was observed that CMAPP demonstrated significant removal efficiencies (97.62%, 96.67%, 98.12%, and 99.32%) for the dyes MB, MG, CV, and BF at a concentration of 500 mg/L under optimal conditions. The findings from the adsorption kinetics and isotherm studies indicated that pseudo-second-order kinetics and the Langmuir model were the most appropriate for characterizing the adsorption process of hydrogels. The thermodynamic findings demonstrated that the adsorption process was exothermic and spontaneous. After five cycles of adsorption, the hydrogel demonstrated a consistent dye removal efficiency of around 80%, indicating commendable recyclability. In the interference studies, CMAPP exhibits superior anti-interference capability against CV and BF, which is advantageous for its practical application. The findings from XPS and FTIR investigations indicate that electrostatic attraction, hydrogen bonding, and n-π interactions are the primary forces between the adsorbent and the dyes. The synthesis of CMAPP offers an innovative approach for the effective elimination of cationic dyes and demonstrates significant potential in the treatment of complicated wastewater.

Waste biomass-based graphene oxide decorated with ternary metal oxide (MnO-NiO-ZnO) composite for adsorption of methylene blue dye

In this study, a novel approach for the removal of methylene blue (MB) dye is effectively illustrated by using biomass based composite adsorbent. The investigation employed areca nut husk (AH) to produce graphene oxide (GO) by a single step calcination method. Thereafter, AH-GO was incorporated by using ternary metal oxide (TMO) via hydrothermal treatment. The developed AH-GO@MnO-NiO-ZnO composite was characterized by various analytical techniques, including FT-IR, XRD, FESEM, HRTEM, BET surface area and Raman spectroscopy which exhibited promising properties for dye adsorption. To study the adsorption efficiency of prepared composite, optimization experiments were performed for adsorbent dose, initial dye concentration and contact time. The optimized parameters during adsorption phenomenon were found to be 0.5g/L of dose, 20mg/L of initial concentration and 180min of time exhibiting removal efficacy of 93.05 ± 0.93%. Moreover, adsorption isotherm and kinetic models were analysed to explore the adsorption behaviour of AH-GO@MnO-NiO-ZnO towards MB dye. The adsorption isotherm and kinetic studies followed Langmuir isotherm model and pseudo-second-order (PSO) model respectively. AH-GO@MnO-NiO-ZnO has demonstrated a maximum adsorption capability of 127.06mg/g. These findings collectively underscore the potential of AH-based adsorbent as a viable, inexpensive, and environment friendly for the treatment of wastewater contaminated with MB dye.

Adsorption of aqueous uranium(VI) species on graphitic carbon nitride adsorbent (g-CNA): kinetic, isotherm and thermodynamic studies

Adsorption of aqueous uranium(VI) species on graphitic carbon nitride adsorbent (g-CNA): kinetic, isotherm and thermodynamic studies

One‐Step Green‐Synthesized UiO‐66‐NH2 /Alginate Composite Hydrogels with Improved Methylene Blue Adsorption

AbstractZirconium‐based metal‐organic frameworks (Zr‐MOFs) represent an important class of MOFs with high stability and outstanding properties, the green preparation and shaping of which are still challengeable works to hinder their real‐world applications. In this presentation, UiO‐66‐NH2 MOFs were in‐situ grown accompanied by alginate (Alg) hydrogelation under aqueous conditions, achieving UiO‐66‐NH2/Alg composite hydrogels. Relevant characterizations demonstrate the in‐situ generated UiO‐66‐NH2 MOFs were evenly distributed in hydrogel networks by attaching on Alg fiber surfaces. The network structure became denser, but both specific surface area and pore volume were augmented due to the presence of MOFs, which in turn increased active sites to interact with adsorbates. Thus, the adsorption capacity to methylene blue (MB) of composite hydrogels became higher with more dosage of MOF ligand, and the pH sensitivity of Alg adsorption to MB in the pH range of 4 to 10 was eliminated. Furthermore, the study of adsorption kinetics and isotherm reveals MB adsorption on the obtained hydrogels belong to rate controlling chemisorption mechanism. In summary, this manuscript presents a facile approach to realizing the green synthesis and shaping of Zr‐MOFs by one‐step compositing of UiO‐66‐NH2 with Alg‐based hydrogels in aqueous system, achieving MOFs‐based composite hydrogels with enhanced MB adsorption.

Enhanced adsorption of malachite green onto a composite material activated carbon and iron(III) oxide nanoparticles: isotherm, kinetic, and thermodynamic study

Enhanced adsorption of malachite green onto a composite material activated carbon and iron(III) oxide nanoparticles: isotherm, kinetic, and thermodynamic study

Oxidation kinetics and electrical properties of oxide scales formed under exposure to air and Ar–H2-H2O atmospheres on the Crofer 22 H ferritic steel for high-temperature applications such as interconnects in solid oxide cell stacks

A 100 h isothermal oxidation kinetics study for Crofer 22H was conducted in air and the Ar–H2-H2O gas mixture (p(H2)/p(H2O) = 94/6) in the range of 973–1123 K. The parabolic rate constant was independent of oxygen partial pressure in the range from 6.2 × 10−24 to 0.21 atm at 1023 and 1073 K, while at 973 and 1123 K it was higher in air than in Ar–H2-H2O. The scales consisted of Cr2O3 and manganese chromium spinel with an Mn:Cr ratio dependent on the oxidation conditions. Cross-scale resistance was evaluated with regards to the application of the steel in solid oxide fuel cells using a number of methods, including X-ray diffraction, scanning electron microscopy, confocal Raman imaging and area-specific resistance measurements.

Effective adsorption of Cr(VI) from aqueous solution by Mg-Fe LDH supported on orange peel activated carbon: isotherm, kinetic, thermodynamics and mechanism studies

The toxic Cr(VI) contaminating water released from the metallurgical, dyeing, and electroplating industries is getting worse day by day and is extremely hazardous to human health. Thus, the development of a cost-effective, quick, and efficient adsorbent is highly essential for the Cr(VI) decontamination from wastewater. Herein, a microwave-assisted carbon-based composite called Mg-Fe LDH@OPAC was prepared by assembling Mg-Fe LDH onto orange peel-activated carbon (OAPC). Prior to investigating deeply into the adsorption behavior of the composite, the Mg-Fe LDH@OPAC formation was confirmed by using instrumental techniques like FESEM, EDS, Zeta potential, XRD, FTIR, Raman, XPS, and BET analyzer. The material had a high surface area of 143.9 m2/g and showed a good monolayer Langmuir uptake capacity of 118.36 mg/g. Under ideal circumstances, the maximum amount of Cr(VI) was removed within just 120 min and showed high efficiency in the presence of other coexisting anions respectively. The adsorption was accounted by pseudo-second-order kinetics and spontaneous in nature. Ultimately, a possible adsorption mechanism was suggested, confirmed by XPS studies; which showed that oxidation-reduction, electrostatic interaction, and surface complexation reaction were responsible for Cr(VI) adsorption on Mg-Fe LDH@OPAC surface.

Facile Synthesis of Polypyrrole-Decorated RGO-CuS Nanocomposite for Efficient Nickel Removal from Wastewater.

Efficient wastewater treatment, particularly the removal of heavy metal ions, remains a challenging priority in environmental remediation. This study introduces a novel sandwich-structured nanocomposite, RGO-CuS-PPy, composed of reduced graphene oxide (RGO), copper sulfide (CuS), and polypyrrole (PPy), synthesized via a straightforward hydrothermal method. The unique combination of RGO, CuS, and PPy offers enhanced adsorption capacity for Ni(II) ions due to RGO's high surface area and CuS's active binding sites, supported by PPy's structural stability contributions. This study is among the first to explore this specific nanocomposite architecture for Ni(II) removal, achieving an adsorption capacity of 166.67 mg/g and a high removal efficiency of 94.9% within 210 min for 55 mg/L of Ni(II) concentration at pH 6 and adsorbent dose of 3 mg/15 mL. The kinetic analysis shows the best fitted time-dependent experimental data with the pseudo-second-order model, indicating chemisorption. Isotherm studies confirmed the Langmuir model as the best fit, yielding a high monolayer adsorption capacity of 166.67 mg/g. Thermodynamic analysis shows the adsorption process was endothermic (ΔH° = 80.23 kJ/mol) and spontaneous (ΔG° ranging from -6.985 to -14.399 kJ/mol). Additionally, reusability tests using 0.1 M HCl for desorption demonstrated good reusability, emphasizing the RGO-CuS-PPy nanocomposite's potential as a sustainable adsorbent for Ni(II) removal in wastewater treatment applications.

Application of a magnetic graphene nanocomposite modified with 5-aminoisophthalic acid amine group for chromium (VI) adsorption from aqueous solutions: kinetic and thermodynamic studies

ABSTRACT Polymer nanocomposites are composite materials that incorporate nanomaterials, such as magnetic graphene oxide (mGO), into a polymer matrix. To enhance its adsorption capacity, the surface of mGO nanoparticles was polymerised by a 5-aminoisophthalic acid amine group (mGO-AIPA) through a simplified co-precipitation method. The structural and morphological characteristics of the synthesised nanoparticles were evaluated through techniques such as X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM), Thermogravimetric analysis (TGA), and Vibrating sample magnetometer (VSM). Response surface method (RSM) was used to evaluate the effectiveness of mGO-AIPA nanocomposite in removing chromium (VI) ions by examining variables such as solution of pH, contact time, adsorbent dose and initial concentration. Also, the study of kinetic models, adsorption isotherms and thermodynamic modelling of the process were evaluated. The results found that the mGO-AIPA nanocomposite has the maximum removal of chromium (VI) ions from the aqueous solution by 83.11% in optimal conditions including pH 3.5, contact time of 35 min, an adsorbent dosage of 25 mg g−1 and an initial concentration of 55 mg L−1. The pseudo-second-order kinetic and Langmuir isotherm models had a better fit with the experimental data of adsorption and the maximum adsorption capacity of chromium (VI) the base of the Langmuir model was 90.91 mg g−1. Moreover, the thermodynamic analysis indicated that the process was exothermic and nonspontaneous process, implying that it was energetically unfavourable. These findings suggest that the mGO-AIPA nanocomposite has a high performance as an effectual adsorbent to eliminate chromium heavy metal from an aqueous medium.

Methylene Blue Adsorption Using Boric Acid Functionalized Activated Carbon: Kinetics, Isothermal, and Thermodynamic Studies

AbstractIn this study, the activated carbon (AC) was prepared from Sesbania sesban plant stem. Boric acid (H3BO3) was used as an activating agent. During calcination, the optimized temperature was kept upto 500 °C for 2 h. The prepared adsorbents were characterized using various techniques such as FT‐IR, scanning electron microscopy, energy dispersive x‐ray spectroscopy, and thermogravimetric analyzer. The prepared adsorbents were used for the removal of methylene blue (MB) dye adsorption. The adsorption experiments were conducted at different pHs such as (2–11), doses (0.0025–0.020 mg), times (30–300 min), MB initial concentrations (100–600 mg L−1), and temperatures (298–318 K), respectively. The maximum MB uptake capacity of the prepared adsorbent was 1380 mg g−1 under optimized adsorption conditions. Furthermore, the kinetic study is well described by pseudo‐second order, whereas the isothermal study showed the Freundlich isotherm was better followed by the equilibrium data. Based on thermodynamic studies, the negative values of ΔG° and ΔH° revealed that the MB adsorption process is spontaneous and exothermic in nature. However, the negative ∆Sxg° value indicates that solid‐solute interaction decreased randomness in the adsorption systems. The overall studies of AC showed that it was better to remove MB from an aqueous solution.

Enhanced elimination of chromium (VI) ions from wastewater with silica-mixed magnetic nanomaterial: isotherm and kinetic studies

Enhanced elimination of chromium (VI) ions from wastewater with silica-mixed magnetic nanomaterial: isotherm and kinetic studies

Utilization of poly(methacrylic acid)‐rice straw graft copolymers for Pb2+ ions removal from wastewater: Synthesis, characterization, and adsorption studies

AbstractRice straw bio waste was converted into a high‐performance adsorbent for Pb2+ ions removal by grafting it with methacrylic acid using microwave irradiation. For this purpose, six levels of poly(MAA)‐rice straw graft copolymers having different graft yields % with increasing order and designated as (PMAARSGC‐I to PMAARSGC‐VI) were prepared and characterized using FTIR, SEM, XRD, TGA, zeta potential and BET analysis. Different factors affecting the Pb2+ removal expressed as adsorption capacity such as pH, extent of grafting, treatment time, and lead ions concentrations were studied in detail. Various kinetics models (pseudo‐first‐order, pseudo‐second‐order, Elovich, and intraparticle diffusion), isothermal (Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich) and thermodynamic studies have been applied. The results demonstrated that (a) FT‐IR, SEM, XRD, TGA, zeta potential, and BET analysis confirmed the formation of carboxyl groups onto the graft copolymer, (b) the adsorption capacity increased with increasing the Pb2+ concentration and extent of grafting within the range studied; pH from 1 to 6; and the adsorption time up to 60 min then leveled off afterward, (c) maximum adsorption capacity of poly(MAA)‐rice straw graft copolymer was found to be 118 mg/g at pH 6, 200 mg/L lead ions concentration, adsorption time, 60 min, and 0.1 g adsorbent, (d) the kinetic and isothermal studies revealed that the privilege of Elovich model and pseudo‐second‐order rate equation as well the Langmuir model with more R2 value. The calculated thermodynamic parameters indicated that the adsorption process was achievable, spontaneous, and exothermic at 298–318 K. Finally, the preliminary adsorption mechanism representing the interaction between the adsorbent and adsorbate has been projected.

The harnessing of natural zeolite for adsorption of methylene blue active substances from carwash wastewater: A kinetic and isotherm study

The harnessing of natural zeolite for adsorption of methylene blue active substances from carwash wastewater: A kinetic and isotherm study

Potential of the Algerian pine tree bark for the adsorptive removal of methylene blue dye: Kinetics, isotherm and mechanism study

This study demonstrates the feasibility of Algerian native pine tree bark (NPTB) as a low-cost, sustainable adsorbent for methylene blue (MB) dye removal from wastewater. Characterization revealed a porous structure with a high surface area and abundant functional groups, ideal for adsorption. Batch experiments optimized conditions for maximum MB removal (99.47%) at pH 8, 55 °C, and 0.4 g NPTB dosage. Kinetic analysis confirmed pseudo-second-order kinetics and intraparticle diffusion, indicating chemisorption. The Freundlich isotherm model best described adsorption, with a monolayer capacity of 37.15 mg/g. Thermodynamic studies indicated the process was spontaneous, endothermic, and feasible at higher temperatures. The estimated cost of NPTB is $0.1376 USD/m³, and its low overall treatment cost makes it a promising and environmentally friendly alternative for wastewater treatment.

Evaluation of a novel activated carbon/graphene oxide as an efficient composite adsorbent for the removal of herbicide 2,4-Dichlorophenoxyacetic acid: Adsorption isotherm and kinetics study

Thysanolaena maxima-derived activated carbon/graphene oxide (TMAC/GO) composite was synthesized through a one-step mixing process via ultrasonication and used as an adsorbent for the removal of 2,4-Dichlorophenoxyacetic acid (2,4-D) herbicide from solution. Various analytical techniques, including Fourier-transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy-energy dispersive X-ray spectroscopy (FESEM-EDX), X-ray diffractometer (XRD), Brunauer, Emmett, and Teller (BET) surface area analyzer, and Transmission electron microscopy (TEM) were employed to characterize the synthesized composite. Results showed that the TMAC/GO had a porous structure with a large surface area of 960 m2/g, an average pore diameter of 2.658 nm, and a total pore volume of 0.6372 cm3/g. A series of batch experiments were conducted for different adsorption parameters, which include TMAC/GO dosage (0.05–0.25 g/L), initial concentration (50–300 mg/L), pH (2–12), contact time (20–140 mins), and temperature (298–398 K). Adsorption thermodynamics, isotherm models, and kinetics were employed to understand the adsorption mechanism. The composite showed good adsorption ability with the Langmuir maximum adsorption capacity of 98.469 mg/g. When compared with TMAC, the composite exhibited higher removal efficiency under the same dosage, concentration, and temperature with variations in pH and time. The pseudo-second-order kinetics model justified the experimental results with an R2 value of 0.997. Furthermore, the composite displayed good reusability performance up to 5 cycles. These findings, along with the cost-effectiveness of the material and its selectivity towards the herbicide, suggest its practical importance for water decontamination.

Charge Modulation at the Liquid Crystal Droplet-Aqueous Interface Enables Ultrasensitive, Nonspecific Protein Detection.

Thermotropic nematic liquid crystals (LC) have been utilized to sense/detect various analytes such as polymers, surfactants, lipids, etc. However, their use for protein detection depends on pre-adsorbed molecules, co-nematogens, or biomolecular agents for specificity.This approach impedes the platform's sensitivity with a detection limit for the folded proteins generally reported in the micromolar concentration range. Here, this work provides fundamental insights into the type of molecular interactions and their modulation that can drive ultrasensitive protein detection at an LC microdroplet/aqueous interface formed without adding an auxiliary co-nematogen. Using ultraviolet (UV) light treated 4-cyano-4'-pentylbiphenyl (5CB) LC and a flow-focused microfluidic device, we prepared different populations of monodisperse and highly negatively charged microdroplets in water. Adding an aqueous solution of various model proteins(α-synuclein, α-chymotrypsin, myoglobin, or bovine serum albumin, BSA) with different secondary structures and surface charges triggers a rapid radial- to bipolar-defect transition in these microdroplets. Isothermal titration calorimetry measurement and molecular dynamic simulation studies attribute this to the dominant electrostatic force-mediated adsorption of proteins at the LC/aqueous interface.Further, bioconjugation-based variation of protein surface charge allows tuning their detection limit.These findings can provide crucial physical cues for designing responsive LC systems and establishing a foundation for developing versatile, molecularly tailored, and highly specific biomolecular detection platforms.

The Adsorption Isotherm and Kinetics Studies of Cu(II) and Cr(III) Metal Ions from Aqueous Solutions on Activated Biosorbent of Coffee Pulp Waste

The Adsorption Isotherm and Kinetics Studies of Cu(II) and Cr(III) Metal Ions from Aqueous Solutions on Activated Biosorbent of Coffee Pulp Waste

Lemon Peel‐Extracted Recyclable Copper Oxide Nanoparticles for Methylene Blue Dye Adsorption: Optimization, Isotherms, Kinetics, Thermodynamics, and Reusability Study

AbstractResearchers are exploring sustainable methods for synthesizing metal oxide nanoparticles to address wastewater pollution, which poses a global threat to aquatic life and human health. The present research aims to biosynthesize recyclable Lemon peel‐extracted copper oxide nanoparticles (CuO NPs) to remove methylene blue dye via adsorption. Our approach involves a comprehensive range of techniques, such as FTIR, XRD, SEM‐EDX, Zeta potential, and UV‐VIS, to thoroughly characterize the NPs. SEM analysis confirmed that the CuO NPs, with an average size of 64.5 nm and a nearly spherical shape, exhibited a zeta potential value of – 16.34, indicating their relative stability. Optimized conditions for the 92.20% adsorption efficiency for methylene blue dye were pH at 6, contact time of 90 min, 0.06 g of adsorbent dose, 10 ppm dye conc., and Temp. 27 °C. Langmuir 1‐based maximum adsorption capacity (qm) was 617.28 mg/g for CuO NPs. Langmuir 1 and Freundlich are the most suitable isotherm models for experimental data, supporting Physi‐chemisorption and chemisorption as rate‐limiting steps in the exothermic adsorption process. A reusability study of up to three cycles proved the sustainability of the materials.

Lithium recovery in a batch adsorption study: Synthesis, characterization, optimization, regeneration, kinetics, and isotherm studies

Lithium (Li)recovery is significant due to an increasing need for Li in diverse applications, particularly in the energy storage domain. In this study, a synthesized adsorbent was developed and utilized to efficiently recover Li. Therefore, this research aims to assess the effectiveness of using the synthesized adsorbent LiHMO to recover Li from the aqueous solution. The surface area and characteristics of the synthesized adsorbent were subjected to analysis utilizing different methods and techniques, including scanning electron microscopy (FESEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis, and Fourier-transform infrared spectroscopy (FTIR). The findings indicated that the synthesized adsorbent demonstrated exceptional adsorption capabilities for Li recovery. Characterization analysis revealed a well-defined porous structure and functional groups on the adsorbent's surface, facilitating adsorption. The surface area of the adsorbent was determined to be 25.54 m²/g, providing a substantial active surface for adsorption processes. The Box-Behnken response surface method (RSM) was utilized to optimize the recovery process for key factors such as pH, adsorbent dose, time, and concentration. The critical operating parameters identified included a pH of 4, initial concentration of 900 mg/L, contact time of 460 min, and adsorbent dosage of 1300 mg/L. The obtained data were analyzed using a quadratic model, yielding an R² value of 0.9538, indicating that the adsorbent is effective in Li adsorption. The optimal conditions for maximizing Li recovery were found to be 95 % and 89 % for maximum and minimum recovery, respectively. The amount of adsorbate adsorbed (qe) was determined to be 6.2 mg g-1. Various kinetic models and isotherms were utilized to conform to these parameters. The Freundlich isotherm and the intraparticle diffusion model showed strong fits, as evidenced by their R² results of 0.9876 and 0.9862, respectively. The kinetic study suggested that the intraparticle-diffusion model best explained the adsorption process, indicating chemisorption as the rate-limiting step. The equilibrium data fitted well with the Freundlich isotherm, suggesting multilayer adsorption with heterogeneous surface energies. Furthermore, the study assessed the adsorbent's regeneration potential, finding that the first cycle of regeneration achieved 91.9 % efficiency, while the fifth cycle maintained a high efficiency of 89.7 %, indicating good reusability of the adsorbent. The study's findings showcase the efficiency of the synthesized adsorbent LiHMO in Li recovery from aqueous solutions, offering valuable information about the best conditions for the adsorption process. As a result of its superior sorption capacity and high recovery of adsorbed Li, the LiHMO adsorbent was selected as the optimal choice for Li recovery from aqueous solutions.

PH-responsive magnetic nanocarrier based on hyaluronic acid-folic acid conjugated Fe3O4 nanoparticles for controlled delivery of imatinib: Isotherms, kinetics, and thermodynamics studies

A novel pH-responsive magnetic nanocarrier was synthesized with hyaluronic acid/folic acid conjugated magnetic nanoparticles and used as a drug carrier for imatinib drug delivery. Magnetic nanoparticles were surface modified with (3-glycidyloxypropyl) trimethoxysilane. Grafting of hyaluronic acid/folic acid on these magnetic nanoparticles was characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, Field emission scanning electron microscopy, thermogravimetric analysis, and vibrating sample magnetometer. The effect of adsorption parameters such as pH, initial concentration, contact time, and adsorbent dosage was examined. The pseudo-second-order model best described the kinetic data, while the Langmuir model best described the isotherm data, indicating physico-sorption and monolayer imatinib adsorption, respectively. Also, thermodynamic experiments showed that the uptake of the drug by the magnetic adsorbent was endothermic and spontaneous. The maximum sorption capacity of unmodified magnetic nanoparticle for imatinib was 6.38 mg/g and for modified magnetic nanoparticles, it was 16.56 mg/g. Imatinib as an anticancer drug, was loaded and the release curve was investigated at pH 5.6 and 7.4 for 6 h. At acidic fluid, the amount of imatinib released increased to 63.01 % compared to physiological fluid with 26.04 % drug release.