Isotherm Studies Research Articles

Efficient Removal of Congo Red Dye Using Activated Carbon Derived from Mixed Fish Scales Waste: Isotherm, Kinetics and Thermodynamics Studies

Efficient Removal of Congo Red Dye Using Activated Carbon Derived from Mixed Fish Scales Waste: Isotherm, Kinetics and Thermodynamics Studies

Kinetic, Isothermal and Thermodynamic Study on the Removal of Hexavalent Chromium with Biocomposites (Cellulose–PLA)

Currently, water is being polluted via various anthropogenic activities, resulting in wastewater contaminated with multiple pollutants, including heavy metals. Hexavalent chromium is a toxic heavy metal that poses significant health risks upon exposure. Biocomposites are materials that are partially composed of organic substances that enhance different properties of a composite. The aim of this study was to evaluate the kinetic, isothermal, and thermodynamic behaviour of a cellulose-based biocomposite with polylactic acid (PLA) for the removal of Cr (VI) from synthetic water. The results indicated that the Freundlich and Elovich models provided the best fit for the isothermal and kinetic data, with R2 values of 0.671 and 0.973, respectively, suggesting that the adsorption process was chemical in nature and occurred on a heterogeneous, multilayer surface. Additionally, the thermodynamic analysis revealed that the adsorption process was exothermic, irreversible, and non-spontaneous. This study presents an innovative approach to the removal of metal ions using a cellulose–PLA biocomposite for wastewater treatment, offering kinetic, isothermal, and thermodynamic data applicable to the adsorption of other heavy metals.

Efficiency of Phragmites australis (Cav.) Trin. Ex Steud. and Typha latifolia L. in remediating methyldiethanolamine (MDEA) from Ilam gas refinery wastewater: Isotherm and kinetic studies.

This study presents a novel, eco-friendly method for removing methyldiethanolamine (MDEA) from wastewater, addressing its environmental impact and elevated chemical oxygen demand (COD) from gas refineries. We employed two wetland plants, Phragmites australis and Typha latifolia, utilizing a hydroponics approach to assess MDEA removal efficiency. Wastewater samples from the Ilam gas refinery in Iran were tested at varying initial concentrations (50 to 1600ppm) over three consecutive 7-day periods, with a 1-day rest interval. Key factors influencing MDEA absorption-contact time, initial effluent concentration, and pH-were systematically analyzed. Results indicated a significant decrease in pH, COD, and MDEA concentration during the first four days. Kinetic modeling employed pseudo-first-order (PFO) and pseudo-second-order (PSO) models, alongside adsorption isotherms (Langmuir, Freundlich, Temkin, Dobinin-Radeshkovich, and Louis), to evaluate MDEA absorption capacity. The Langmuir isotherm best described the absorption characteristics of both plants. Maximum adsorption capacities were recorded for P. australis at 1.181, 2.018, and 3.77mg/L across the experimental periods, while T. latifolia showed values of 0.779, 1.099, and 2.99mg/L. Kinetic analysis favored the pseudo-second-order model for both species. Our findings suggest that P. australis is the more effective candidate for phytoremediation of MDEA in wastewater treatment applications.

Biosorption performance toward Co(II) and Cd(II) by irradiated Fusarium solani biomass.

Fusarium solani biomass plays a significant role in water pollution remediation due to its ability to sequester heavy metals, particularly cobalt (Co(II)) and cadmium (Cd(II)), which pose severe environmental and health risks. This study aimed to identify fungi from sewage-contaminated sites and evaluate their efficiency in absorbing and reducing Co(II) and Cd(II) ions. The biosorption potential of irradiated Fusarium solani biomass for removing Co(II) and Cd(II) ions from aqueous solutions was investigated. Six fungal isolates were screened, and the most promising isolate, identified as F. solani, was selected for further research. The biomass was exposed to different gamma irradiation doses (0, 1, 3, and 5kGy), and its biosorption efficiency was assessed. The highest biosorption efficiencies were observed with the biomass exposed to 5kGy (FS-5), achieving 37% for Co(II) and 90% for Cd(II) removal within 25min. The surface area of the biosorbent increased from 13.12m2g-1 for unexposed biomass (FS-0) to 34.87m2g-1 for FS-5, enhancing the biosorption capacity. The adsorption kinetics followed a pseudo second order model with high correlation coefficients (R2 > 0.993), indicating chemisorption as the rate-limiting step. Isotherm studies showed that the Langmuir model provided a better fit to the experimental data, with maximum adsorption capacities of 4.44mgg-1 for Co(II) and 21.00mgg-1. This study provides valuable insights into the effective removal of Cd and Co from polluted sites, underscoring the potential of developing eco-friendly and cost-effective bioremediation approaches.

Synthesis and characterization of SiO2/GO/Al2O3 nanocomposite adsorbent for the uptake of ciprofloxacin: isothermal and reusability studies

Synthesis and characterization of SiO2/GO/Al2O3 nanocomposite adsorbent for the uptake of ciprofloxacin: isothermal and reusability studies

Azithromycin removal from water via adsorption on drinking water sludge-derived materials: Kinetics and isotherms studies.

In this study, we utilized drinking water treatment sludge (WTS) to produce adsorbents through the drying and calcination process. These adsorbents were then evaluated for their ability to remove azithromycin (AZT) from aqueous solutions. The L-500 adsorbent, derived from the calcination (at 500°C) of WTS generated under conditions of low turbidity in the drinking water treatment plant, presented an increase in the specific surface area from 70.745 to 95.471 m2 g-1 and in the total pore volume from 0.154 to 0.211 cm3 g-1, which resulted in a significant AZT removal efficiency of 65% in distilled water after 60 min of treatment. In synthetic wastewater, the rate of AZT removal increased to 80%, in comparison, in a real effluent of a municipal wastewater treatment plant, an AZT removal of 56% was obtained. Kinetic studies revealed that the experimental data followed the pseudo-second-order model (R2: 0.993-0.999, APE: 0.07-1.30%, and Δq: 0.10-2.14%) suggesting that chemisorption is the limiting step in the adsorption using L-500. This finding aligns with FTIR analysis, which indicates that adsorption mechanisms involve π-π stacking, hydrogen bonding, and electrostatic interactions. The equilibrium data were analyzed using the nonlinear Langmuir, Freundlich, and Langmuir-Freundlich isotherms. The Langmuir-Freundlich model presented the best fitting (R2: 0.93, APE: 2.22%, and Δq: 0.06%) revealing numerous interactions and adsorption energies between AZT and L-500. This adsorbent showed a reduction of 19% in its AZT removal after four consecutive reuse cycles. In line with the circular economy principles, our study presents an interesting prospect for the reuse and valorization of WTS. This approach not only offers an effective adsorbent for AZT removal from water but also represents a significant step forward in advancing sustainable water treatment solutions within the framework of the circular economy.

Adsorption of resorcinol onto synthetic calcium phosphate compounds: Kinetic, isotherm, and thermodynamic studies

Adsorption of resorcinol onto synthetic calcium phosphate compounds: Kinetic, isotherm, and thermodynamic studies

Molecular insights into the aspartate protease Plasmepsin II activity inhibition by fluoroquinolones: A pathway to antimalarial drug development

Plasmepsin II (PlmII) belongs to the aspartate proteases and is involved in hemoglobin degradation in Plasmodium falciparum. Due to its critical role in the survival of the Plasmodium, PlmII is considered as a potent drug target for antimalarial therapy. We have done recombinant protein production of pro-plasmepsin II (Pro-plmII). Pro-PlmII was further activated to mature form (mPlmII) and its activity was confirmed by enzyme kinetics studies. The fluorescence spectroscopic and isothermal titration calorimetric studies show that fluoroquinolone-based antibiotic drugs norfloxacin, ciprofloxacin, and sparfloxacin bind with mPlmII. Molecular docking results show that only norfloxacin and ciprofloxacin are able to bind at the active site of mPlmII via hydrogen binding and hydrophobic interactions. Enzyme kinetics analysis reveals that norfloxacin and ciprofloxacin effectively inhibit mPlmII activity, while sparfloxacin does not exhibit any inhibitory effect on the enzyme's catalytic function. The two methyl groups on the 3rd and 5th carbon atoms of the piperazine ring make sparfloxacin unable to go inside mPlmII and bind at its active site. Overall, the results here suggested that fluoroquinolone-based antibiotic drugs norfloxacin, and ciprofloxacin, can be repurposed as antimalarial inhibitors targeting aspartic proteases. These findings contribute to pave the way for potential therapeutic interventions targeted at malaria.

Multi-walled carbon nanotubes/TiO2/Chitosan nanocomposite for efficient removal of malachite green dye from aqueous system: A comprehensive experimental and theoretical investigation.

This study presents the preparation, characterization, and application of a novel Multi-walled carbon nanotubes/TiO2/chitosan (MWCNT/TiO2/CS) nanocomposite, prepared using a hydrothermal method, for the removal of malachite green (MG) dye from aqueous solutions. Adsorption studies revealed optimal dye removal within 15min of adsorption equilibrium time, with maximum removal efficiency of 98.53% at pH7.0, dose 0.4g/L and 298K. Isotherm studies showed the Langmuir model best described the adsorption equilibrium data with maximum monolayer adsorption (qm) value was found to be 269.98mg/g at 298K. Kinetic analyses favored the pseudo-second-order model with qcal value was found to be 201.6mg/g at Co=100mg/L. Thermodynamic investigations indicated an exothermic, spontaneous adsorption process. Seven successful adsorption-desorption cycles were achieved using HCl as an eluent (97.65% desorption). Theoretical reactivity parameters derived from DFT calculations corroborated experimental findings, elucidating the molecular-level mechanisms underlying the efficient adsorption of MG onto the MWCNT/TiO2/CS surface. The strong electrophilic nature and electron-accepting character of the MG molecule, along with its ability to form electronic interactions, explain its high adsorption affinity. These findings demonstrate the potential of MWCNT/TiO2/CS nanocomposite as an effective and sustainable solution for MG dye removal from aqueous environments.

ADSORPTIVE REMOVAL OF CRYSTAL VIOLET AND SUNSET YELLOW FROM WATER USING LABLAB PURPUREAUS HUSK- COST-EFFECTIVE DE-DYING APPROACH

A novel citric acid-activated Lablab purpureus husk is proposed to remove crystal violet (CV) and sunset yellow (SY) by column chromatographic elution in a cost-effective way. The adsorbent was characterized by Scanning Electron Microscopy (SEM) and the images supported the adsorptive nature of the material. The experiments were carried out on a chromatographic column by homogenously packing the pre-wetted adsorbent into the column and eluting the dye solution through it. The effects of initial dye concentration, adsorbent dose, pH, contact time, and flow rate were optimized. The efficient removal of up to 300 and 4400 µg/mL of CV and SY, respectively, was observed. The pH range of 4-5 for CV and >4 for SY were found effective. The flow rate was optimized at 1 ml/min. The contact time was found less than 10 minutes. The adsorbent was successfully removed 96.62% and 99.62% of CV and SY, respectively. The Freundlich and Langmuir adsorption isotherm studies were carried out to interpret the interaction between the adsorbate and adsorbent. These models are instrumental in optimizing and scaling up the adsorption process for practical and industrial applications. The experimental data for the adsorption of CV and SY fitted well with the Freundlich isotherm, and the kinetic study of both CV and SY fitted well with the pseudo-second-order reaction.

Kinetic and isotherm studies of nickel and cadmium ions adsorption onto Clay-Chitosan composite

Kinetic and isotherm studies of nickel and cadmium ions adsorption onto Clay-Chitosan composite

Correction to: Adsorption of ytterbium(III) ions on ivy leaves marc: isotherm, kinetic and thermodynamic studies

Correction to: Adsorption of ytterbium(III) ions on ivy leaves marc: isotherm, kinetic and thermodynamic studies

Synthesis, characterization, experimental design and process analysis of heavy metals adsorption on a wheat straw based amidoximated bioadsorbent

In this research, 3-(trimethoxysilyl)propyl methacrylate (MPS) silane agent was applied to modify the extracted wheat straw (WS) cellulose as a natural biopolymer. Polyacrylonitrile (PAN) was attached to the MPS-modified WS (MPS-WS) via in-situ polymerization to form PAN-WS biocomposite. AO-WS amidoximated biocomposite adsorbent was synthesized through amidoxime reaction and the effects of different parameters including agitation speed, metal ion concentration, and adsorbent dosage on its efficiency of Pb(II) removal were investigated using the Taguchi experimental design method. The adsorbent was characterized using FE-SEM, FTIR, XRD, and TGA. The FTIR results confirmed that the alkaline treatment removed the hemicellulose and lignin groups and that the silane agent successfully bonded to the WS cellulose. The thermal stability of WS was enhanced by the MPS-WS composite due to the attachment of acrylonitrile polymer chains. The ANOVA results indicated that increasing the adsorbent dosage and decreasing the pollutant’s initial concentration significantly improved the adsorption efficiency. The optimal conditions (an agitation speed = 400 rpm, C0 = 60 mg/L, an adsorbent amount = 0.1 g) yielded maximum adsorption capacity of 22.26 mg/g for the AO-WS bioadsorbent. The kinetic and isotherm studies revealed that the pseudo-second-order kinetic model and the Dubinin-Radushkevich isotherm fit the experimental data best.

Design and fabrication of nanocomposite adsorbents for dairy industry wastewater treatment

The dairy industry produces a significant volume of effluents that contain various pollutants, which causes environmental issues. In this study, the fabrication and performance of nanocomposite adsorbents incorporating activated carbon (AC), calcium alginate (CA), and nanosilica, as a simple, cost-effective, and eco-friendly approach to treat dairy wastewater, aiming to enhance food processing sustainability by reducing water consumption, minimizing wastewater, and supporting the Water-Food-Environment Nexus. The nanoparticles were synthesized using sand extraction in an environmentally friendly approach with a size of 30–45 nm. Several techniques such as X-ray fluorescence (XRF), X-ray diffraction (XRD), ultraviolet–visible spectroscopy (UV–VIS), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) were used to characterize the materials. Furthermore, the nanocomposite adsorbent performance and efficiency in removing chemical oxygen demand (COD) were assessed through batch experiments. The nanocomposite adsorbents’ optimal conditions were investigated through batch experiments, achieving a 99.7% COD removal in dairy wastewater treatment. The best results were obtained with a 4-h contact time, pH of 2, and nanosilica dosage of 10%, demonstrating the adsorbent’s high efficiency in organic pollutant removal. However, the adsorption isotherm, kinetic, and thermodynamic studies were carried out and the best-fitted models of isotherm, and kinetic models were Langmuir, and pseudo-second-order reaction, respectively. The thermodynamic reaction of this study is related to being endothermic.

Synthesis and characterization of corn cob activated carbon for Pb(II) adsorption with real-time monitoring using Internet of Things

Abstract Here, we investigate the adsorption of Pb(II) using AC derived from corn Rachis (RAC) with various carbonization temperatures: 500°C, 700°C, and 900°C using KOH solution as the activator. Fourier Transform Infrared Spectroscopy (FTIR) analysis revealed the presence of hydroxyl and carbonyl functional groups and optical-dielectric function change under the carbonization process. X-ray Diffraction (XRD) patterns confirmed the presence of (002) and (100) lattice planes, indicating a graphitic phase with amorphous area (X_a) domination. Scanning Electron Microscopy (SEM) images showed a honeycomb-like morphology, while Energy Dispersive X-ray (EDX) analysis indicated a carbon content of over 90%. Brunauer-Emmett-Teller (BET) analysis shows the high specific surface area of each sample (>1000 m2/g). The highest Pb(II) adsorption efficiency was achieved at 99.77%, with maximum performance at pH = 7.31, and temperature ~26.7℃, supported by the narrowing phonon vibration (Δ(LO-TO), lower electron loss function (ELF) shifts in wavenumber, higher X_a, and confirmed through adsorption kinetic and isotherm study. Here, we demonstrate a fresh methodology based on real-time monitoring using the Internet of Things of RAC as a promising adsorbent for Pb(II) removal with an adsorption capacity of 2.598 mg/g. In addition, the ability of adsorption results without stirring aids to determine their ability when applied to the environment has been studied.

Efficient magnetic adsorption of polystyrene nanoplastic from aqueous solutions by eco-friendly Fe3O4 nanoparticles: Removal, kinetic and isotherm modeling studies

Efficient magnetic adsorption of polystyrene nanoplastic from aqueous solutions by eco-friendly Fe3O4 nanoparticles: Removal, kinetic and isotherm modeling studies

Synthesis and characterization of a fluorescent magnetic molecularly imprinted polymer for enhanced adsorption and selective extraction of pesticides from agricultural waters

IntroductionA novel fluorescent magnetic molecularly imprinted polymer (FMMIP) was developed for the effective extraction of malathion (MLT) and chlorpyrifos (CPS) from agricultural water sources.MethodsThe FMMIP was confirmed to have a stable polymer structure with significant thermal resilience through comprehensive characterization using techniques such as TEM and TGA. The magnetic properties of the FMMIP facilitated easy separation by external magnetic fields, with a notable magnetization of 0.006 emu/g. Kinetic and isotherm studies revealed that adsorption of MLT and CPS onto the FMMIP conformed best to the pseudo-first-order model and Freundlich isotherm, suggesting a predominance of physisorption mechanisms and heterogeneous binding sites.Results and DiscussionThe FMMIP demonstrated exceptional adsorption capacities, achieving a maximum of 93 mg/g for MLT and 69 mg/g for CPS. Regeneration trials indicated that the FMMIP maintains its high adsorptive performance over multiple cycles, highlighting its potential for sustainable use. Statistical validation confirmed the method’s reliability, with RSD values for MLT and CPS at 6.5% and 7.3%, respectively, and LODs determined to be 1.26 mg/L for MLT and 1.22 mg/L for CPS. The strong R2 values of 0.992 for MLT and 0.998 for CPS from the adsorption studies substantiate the method’s effectiveness. This study demonstrates that the synthesized FMMIP is a promising material for removing MLT and CPS, supporting its application in environmental clean-up initiatives to protect and preserve ecosystems.

Facile Synthesis of Acyl-Hydrazone Composites Based on Hydrazide-Modified Formylated Polystyrene for Effective Removal of Heavy Metal Ions and Sulfides from Water.

In this study, waste polystyrene was modified and upgraded to prepare formylated polystyrene, and the modified polystyrene acetyl hydrazone (LT-HPA) was synthesized by condensation with polymethyl-propionyl-hydrazine. It is proven that the modification of the adsorption material is successful by various characterization methods. In the subsequent pollutant removal study, pH, mass, concentration, contact time, and salt ion interference were investigated. The optimal pH for Cu(II) and sulfide removal was 5 and 11, respectively, and the optimal mass of adsorbent was 1 g/L. It was found that the maximum removal rate of Cu (II) was 231.51 mg/g. The adsorption equilibrium time was less than 40 min. This is due to the good adsorption activity of acyl hydrazide groups on the skeleton for Cu (II) through coordination. The maximum desulfurization amount in 60 min was 370.21 mg/g, which was mainly caused by the oxidation of sulfides by surface oxidizing groups. Isotherm and kinetic studies show that the adsorption processes of Cu (II) and sulfides are consistent with the Langmuir model and pseudo-second-order kinetic model. Thermodynamic parameters show that the removal of Cu (II) and sulfides is a spontaneous endothermic process. The adsorption mechanism is mainly chemical adsorption, supplemented by physical adsorption. After 10 regenerated adsorption/desorption cycles, the removal rates of Cu (II) and sulfides remained above 85%, indicating that polystyrenesulfonate acetylhydrazone (LT-HPA) adsorption materials have good reusability. In addition, the adsorbent has good thermal stability, salt resistance, and environmental friendliness. In summary, the modified formylated polystyrene acetyl hydrazone (LT-HPA) has a good application prospect in the removal of copper(II) and sulfides and provides a fresh way for upgrading polystyrene.

Graphene Oxide as a Highly Efficient and Reusable Adsorbent for Simultaneous Removal of Parabens: Optimization by Response Surface Methodology, Adsorption Isotherms and Reusability Studies

Graphene Oxide as a Highly Efficient and Reusable Adsorbent for Simultaneous Removal of Parabens: Optimization by Response Surface Methodology, Adsorption Isotherms and Reusability Studies

Application of CuFe2O4/CuS as a new green magnetic nanocomposite in adsorption of tetracycline from aqueous solutions: mathematical models of thermodynamics, isotherms, and kinetics

In current study, a novel adsorbent of CuFe2O4/CuS magnetic nanocomposite (MNC) was constructed via a green approach for tetracycline (TC) removal. The leaf extract of the Alhagi pseudalhagi plant was employed as a green reductant agent. The features of the nanocomposite were characterized using XRD, FTIR, FESEM, TEM, BET, and VSM. Batch studies were conducted to assess the impact of parameters, including pH (3.0–9.0), adsorbent dosage (0.025–2 g/L), TC concentration (5–100 mg/L), and temperature (5–50 °C) on the TC adsorption efficiency. The antibiotic was fully removed at pH 7.0, nanocomposite dose of 1.5 g/L, time of 200 min, and TC content of 5 mg/L. Based on the thermodynamic study, the TC adsorption onto the CuFe2O4/CuS MNC occurred spontaneously and was primarily driven by physical interactions (physisorption). Positive values of ∆H° (enthalpy change) and ∆S° (entropy change) demonstrated that the adsorption process is naturally endothermic, and the degree of dispersion improves with rising temperature. Adsorption kinetics was well fitted by the pseudo-second-order model. The isotherm studies showed that TC can be removed by the adsorbent at a maximum of 31 mg/g. Overall, CuFe2O4/CuS MNC exhibited notable efficacy and cost-effectiveness (reusability: 5 times) for the TC adsorption from water.