Isotherm Model Research Articles

Synergistic effect of Canarium strictum leaves extract and KI on the corrosion protection of mild steel in 15% HCl solution

The inhibitory potential of an alcoholic extract derived from Canarium strictum leaves (CSL) was evaluated as a corrosion inhibitor for mild steel (MS) in 15% HCl solution. Furthermore, to enhance its inhibition effectiveness, the influence of potassium iodide (KI) was also examined. The corrosion inhibition and adsorption characteristics of CSL were comprehensively analysed through weight loss measurement, electrochemical impedance measurement (EIS), potentiodynamic polarization (PP), UV–visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), scanning electron microscopy and energy dispersive spectroscopy (SEM–EDS). The effect of temperature and immersion time on corrosion inhibition was also investigated. The studied CSL extract exhibited maximum inhibition efficiency of 92.2% at 700 ppm alone, while adding 5 ppm KI 96.8% inhibition efficiency was observed. Moreover, with KI, an efficiency of 98% was observed at extended immersion of 48 h. The PP results showed that CSL and CSL + KI were good mixed-type inhibitor system. Adsorption data was best fitted to the Langmuir isotherm model, and thermodynamic, kinetic, and surface analyses shed light on the inhibitory mechanism.

Bimetallic Zinc-Iron-Modified Sugarcane Bagasse Biochar for Simultaneous Adsorption of Arsenic and Oxytetracycline from Wastewater

Arsenic (As), a highly toxic and carcinogenic heavy metal, poses significant risks to soil and water quality, while oxytetracycline (OTC), a widely used antibiotic, contributes to environmental pollution due to excessive human usage. Addressing the coexistence of multiple pollutants in the environment, this study investigates the simultaneous adsorption of As(III) and OTC using a novel bimetallic zinc-iron-modified biochar (1Zn-1Fe-1SBC). The developed adsorbent demonstrates enhanced recovery, improved adsorption efficiency, and cost-effective operation. Characterization results revealed a high carbon-to-hydrogen ratio (C/H) and a specific surface area of 1137 m2 g−1 for 1Zn-1Fe-1SBC. Isotherm modeling indicated maximum adsorption capacities of 34.7 mg g−1 for As(III) and 172.4 mg g−1 for OTC. Thermodynamic analysis confirmed that the adsorption processes for both pollutants were spontaneous (ΔG < 0), endothermic (ΔH > 0), and driven by chemical adsorption (ΔH > 80 kJ mol−1), with increased system disorder (ΔS > 0). The adsorption mechanisms involved multiple interactions, including pore filling, hydrogen bonding, electrostatic attraction, complexation, and π-π interactions. These findings underscore the potential of 1Zn-1Fe-1SBC as a promising adsorbent for the remediation of wastewater containing coexisting pollutants.

Fabrication of a poly(m‑aminophenol)/3-aminopropyl triethoxysilane/graphene oxide ternary nanocomposite for removal of Cu(II) from aqueous solution

Three composites based on Poly (meta-aminophenol) (PmAP), (3-aminopropyl) triethoxysilane (APTES) and graphene oxide (GO) were synthesized with initial GO dispersion of 3.3, 6.6, and 9.9 mg/mL. First, in-situ polymerization of meta-aminophenol monomer on the surface of graphene oxide (GO) was carried out. Then, the hydroxyl groups of both the GO and the polymer were targeted using (3-aminopropyl) triethoxysilane (APTES) to stop the polymer solubility, increase adsorption sites, and bind the two components. The obtained three composites were applied for efficient removal of Cu(II) from polluted water. PmAP/APTES/GO(6.6) composite was the best one for the uptake of Cu(II) with a maximum adsorption capacity of 324.54 mg/g at 40 °C and pH 7 according to Langmuir. PmAP/APTES/GO(6.6) hybrid composite was characterized by different techniques. The adsorption of Cu(II) on this composite was optimized under various experimental conditions. Furthermore, the isotherm data of the uptake of Cu(II) on PmAP/APTES/GO(6.6) were found to agree with the Freundlich and Langmuir model’s linear and nonlinear forms. Chemosorption was suggested by the Dubinin-Radushkevich (D-R) isotherm model as the calculated mean sorption energy exceeds 16 kJ/mol. The thermodynamic analysis of the adsorption process reflects an endothermic, spontaneous process that leads to more disorder at the solid-liquid interface. The chemical interactions between Cu(II) versus oxygen and nitrogen of the functional groups on the surface were demonstrated by X-ray Electron Spectroscopy (XPS). Five cycles of adsorption and desorption of Cu(II) from the prepared composite were carried out with a loss of only 6.3% of its adsorption capacity.

Unveiling the potential of Aspergillus terreus SJP02 for zinc remediation and its driving mechanism

In present study, 15 morphologically different fungi isolated from rhizopheric soils of an industrial area were screened for their Zn2+ removal efficiency from aqueous solution. Isolate depicting highest potential was molecularly identified as Aspergillus terreus SJP02. Effect of various process parameters viz. biosorbent dose, contact time, temperature, agitation rate, pH and initial Zn2+ concentration on the fungal sorption capacity were studied. The biosorbent exhibited maximum Zn2+ sorption capacity of 10.7 ± 0.2 mg g− 1 in 60 min. Desorption studies showed 71.46% Zn2+ recovery rate in 120 min with 0.01 N HNO3, indicating efficient metal recovery for reuse and subsequent reutilization of spent mycosorbents. Acid digestion study suggested adsorption being the primary mechanism accounting for 87% Zn2+removal. It was further confirmed by the FE-SEM and EDX analysis. FTIR analysis suggested involvement of amino, hydroxyl, carbonyl, and phosphate functional groups of fungal cell wall in adsorption. The experimental results were in accordance with the tested isotherm and kinetic models, and suggested the role of physical adsorption for Zn2+ removal. Noteworthy, the present study showed better sorption capacity in considerably shorter equilibration time compared to previous reports and advocate potential utilization of A. terreus SJP02 for bioremediation of Zn2+ contaminated wastewater at industrial scale.

Novel palm peat lignocellulosic adsorbent derived from agricultural residues for efficient methylene blue dye removal from textile wastewater

Palm Peat (PP), the world’s first rich lignocellulosic medium derived from date palm agricultural residues, has not been previously explored for environmental purification. This study evaluates PP's performance in adsorbing methylene blue (MB) dye. PP is characterized by a spongy, porous structure with a surface area of 16 m2/g. It possesses a significant carbon and oxygen composition and features active surface functional groups. Under conditions of 30 mg/L initial MB concentration, 1 g/L PP dose, T = 30 °C, pH 7, and 900 rpm stirring speed, PP achieved a 68.26% MB removal efficiency within 90 min. Although higher temperatures enhanced MB removal efficiencies, room temperature (30 °C) was chosen for subsequent experiments to assess adsorption performance under ambient conditions and minimize energy consumption. Stirring speeds exceeding 900 rpm reduce MB removal efficiency, likely due to shear forces disrupting the interaction between MB molecules and PP or causing desorption of previously adsorbed dye molecules. Response surface methodology combined with a central composite design was employed to optimize the initial MB concentration, PP dosage, and solution pH. Under the optimum conditions, PP achieved 97.89% MB removal. PP exhibited strong stability over five adsorption cycles. Adsorption occurs via π-π stacking, hydrogen bonding, hydrophobic-hydrophobic interactions, and electrostatic interaction with the process being endothermic and following the Langmuir isotherm model and pseudo-second-order kinetic model. The adsorption efficiency studies across different water matrices revealed the lowest degradation rate in the drain water matrix. PP achieved 71.5% MB removal and 48.16% TOC removal from real textile wastewater.

Interfacial Adsorption Interactions of Dyes and Chitosan/Activated Carbon@Curcumin Derivatives in Single-Component and Binary Solutions.

The remediation of wastewaters contaminated with dyes (discharged mainly from industry) is very important for preserving environmental quality and human health. In this study, a new composite chitosan (CS)-based adsorbent combined with activated carbon (AC) and curcumin (Cur) (abbreviated hereafter as CS/AC@Cur) in three different ratios (12.5%, 25%, and 50%) was synthesized for the removal of anionic [reactive black 5 (RB5)] and cationic [methylene blue (MB)] dyes in single-component or binary systems. The synthesized materials were completely characterized through Fourier transform infrared spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller analysis, and X-ray diffraction. Specifically, a decrease in the surface area of CS/AC@ was observed with the addition of curcumin, from 163 to 18 m2/g, for all CS/AC@Cur derivatives. In terms of the adsorption results, the optimal derivative for the removal of both RB5 and MB was found to be CS/AC@Cur50%, providing 93% removal at pH 2.0 ± 0.1 for RB5 and 54% removal at the optimum pH of 9.0 ± 0.1 due to electrostatic attractions. The Elovich and pseudo-second-order kinetic model, with a correlation coefficient R2 of >0.98, better tailored the results, indicating that adsorption was controlled by chemisorption. In addition, the Sips (Langmuir-Freundlich) isotherm model fitted better to the results, with calculated capacities of 338 and 307 mg/g for RB5 and MB, respectively. The thermodynamic analysis showed a spontaneous and endothermic procedure, with chemisorption as the main mechanism. Reuse experiments showed that the removal efficiency was retained at high levels, while stability studies revealed that the adsorbent retains its structural integrity, even at extreme pH values. Finally, the adsorption of RB5 and MB in a mixed solution was investigated, providing a competitive effect between the anionic and cationic dyes.

Pharmaceuticals removal from aqueous solution by water hyacinth (Eichhornia crassipes): a comprehensive investigation of kinetics, equilibrium, and thermodynamics.

This study shows the efficiency of WH-C450, an adsorbent obtained from water hyacinth (WH) biomass, in the removal of sulfamethoxazole (SMX) from aqueous solutions. The process involves calcination of WH at 450°C to produce an optimal adsorbent material capable of removing up to 73% of SMX and maximum SMX adsorption capacity of 132.23mg/g. Fourier-transform infrared (FTIR) characterization reveals the involvement of various functional groups in the adsorption process through hydrogen bonds and electron-donor-acceptor (EDA) interactions. X-ray diffraction (XRD) analysis confirms the presence of phases containing CO32-, PO43- ions, as well as elements such as Si and Fe, which contribute to the adsorption mechanism through hydrogen bonding and complexation, respectively. X-ray photoelectron spectroscopy (XPS) analysis further supports these interactions. Kinetic analysis shows rapid adsorption, which combines physical and chemical processes and leads to rapid attainment of equilibrium. This is due to the high affinity of WH-C450 for SMX, which allows for a fast and efficient adsorption process. Isothermal modeling reveals multilayer adsorption with favorable interactions. Thermodynamic analysis confirms the endothermic and temperature-dependent nature of the process. In addition, pH, adsorbent dose, and initial concentration are important in adsorption. Lower pH levels enhance cationic SMX adsorption, while higher adsorbent doses improve efficiency. Optimal conditions were identified by experimental design, enabling the establishment of a predictive model. Consequently, the SMX removal capacity is strongly correlated with the initial concentration. This research underscores the potential of WH-C450 for antibiotic removal in water treatment applications.

Advancing eco-friendly adsorption: a sustainable approach for rapid and efficient methylene blue removal

Abstract Synthetic dyes, particularly methylene blue (MB), pose significant environmental challenges due to their persistent presence in water bodies. This study introduces a sustainable polymer adsorbent, poly(LIM-co-DVB-co-AcM), synthesized using d-limonene and 4-acryloylmorpholine. Comprehensive characterization using FTIR, SEM, TGA, and BET analysis revealed its thermal stability, surface morphology, and adsorption properties. Adsorption experiments demonstrated optimal MB removal at pH 7.0 with a 20 mg dosage and a 60-min contact time. The Langmuir isotherm model showed monolayer adsorption with a capacity of 54.2 mg g−1, while kinetic studies confirmed the suitability of the pseudo-second-order model. Thermodynamic analysis indicated a spontaneous and exothermic process. The polymer achieved over 99% MB removal efficiency across diverse water matrices, highlighting its potential as a scalable and eco-friendly solution for water purification.

New functionalized magnetite chitosan–heterocyclic nanocomposites excelling in Cd2+ removal from aqueous solution with biological activity

Newly modified magnetic chitosan nanoparticles were synthesized for the high-efficiency removal of cadmium ions from aquatic environments. The structure and morphology of the composites were confirmed using FTIR, TGA, XRD, BET, SEM, TEM, SAED pattern analysis, and zeta potential. Under optimal conditions (pH = 6.0, contact time = 120 min, and sorbent dosage = 0.005 g/100 mL), the maximum removal of Cd (II) by synthesized samples MC, SA, and SB was 90.8%, 95%, and 95.15%, respectively. The kinetic data at optimal pH = 6 could be accurately described using a pseudo-second-order equation, while the Langmuir isotherm model best represented the sorption process. The Langmuir Qmax values for the synthesized nanocomposites S*, S3, S4, S*t, S3t, and S4t were 243.90, 250, 270.27, 212.76, 237.09, and 238.09, respectively. The thermodynamic analysis of these samples shows that the sorption process was exothermic (negative ∆H°) − 15.148, − 13.60, − 13.18, − 18.163, − 16.820, and − 16.06 kJmol−1, respectively. This implies that the diffusion of Cd(II) on the sorbent decreased with the temperature rise. The positive values of ΔS⁰ were 152.37, 147.80, 146.83, 160.94, 157.08, and 154.93 kJmol−1, respectively. The antimicrobial properties of the functionalized sorbents SA and SB were evaluated by measuring the zone of inhibition (ZOI) against Staphylococcus aureus and Klebsiella pneumoniae, representing Gram-negative and Gram-positive bacteria, respectively. SA and SB showed promising activity, demonstrating clear zones of (20 ± 0.2 and 18 ± 0.4 mm), and (22 ± 0.2 and 20 ± 0.4 mm) for S. aureus and K. pneumoniae, respectively. Additionally, these sorbents demonstrated moderate antioxidant activity, with the highest scavenging percentages of 94.20% and 96.63%, respectively, at a concentration of 1000 µg/mL, as assessed by the DPPH method.

Preparation of MOEAMCl and MAAm Based Hydrogels and Effective Use in Anionic Dye Adsorption

ABSTRACTIn this study, hydrogels based on [2‐(Methacryloyloxy)ethyl]trimethylammonium chloride (MOEAMCl) and methacrylamide (MAAm) were synthesized for the removal of anionic dyes from aqueous solutions. Following detailed characterization, the use of hydrogels for methyl orange (MO) adsorption was investigated. Hydrogels prepared at MOEAMCl‐MAAm monomer feed ratios of 75:25 and 50:50 (HD‐2 and HD‐3) were found to be effective in MO removal. The optimal pH for MO adsorption was determined to be 9, the adsorption time 6 h, and the amount of adsorbent 0.1 g. Under optimal adsorption conditions, dye removal at an MO concentration of 1000 ppm was 89.4% and 90.9% for HD‐2 and HD‐3 hydrogels, respectively, with adsorption capacities of 950 and 994 mg/g. It was observed that MO adsorption on both hydrogels decreased with increasing adsorbent amount and temperature, but was almost unaffected by the medium matrix. Additionally, the Freundlich isotherm was found to be the appropriate isotherm model, and kinetic results indicated that the HD‐3 hydrogel fit all examined kinetic models better than HD‐2. In conclusion, it was determined that these adsorbents could be efficiently used for anionic dye removal.

Removal of dyes from aqueous solution using a magnetic graphene oxide nanocomposite: kinetic, isothermal, and thermodynamic characterization

The efficacy of utilizing graphene-magnetite nanocomposite for methylene blue and crystal violet adsorption treatment from aqueous samples was investigated in this study. The nanocomposite properties were evaluated by Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and vibrating quantum magnetometry. Some adsorption parameters such as adsorption capacity, contact time, stirring rate, temperature, and pH of the aqueous solution were explored in the research too. Moreover, it was found that adsorption followed a pseudo-second-order kinetic model with an R2 value of 0.999 resulting in a maximum adsorption capacity of 240 mg/g for methylene blue and 203 mg/g for crystal violet respectively. Besides, different well-known isotherm models fit the equilibrium data well. Assessments of thermodynamic parameters showed that the removal of both dyes by GO-Fe3O4 nanocomposite is spontaneous. Also, the reuse ability of GO-Fe3O4 nanocomposite was studied and the result was shown to be recycled suitably and possessed adsorptive properties so that it can be developed as an inexpensive and alternative adsorbent for dye wastewater treatment.

Deciphering the mechanism for encapsulation of MOF (Fe-glutaric acid) onto Se/SnO2 embedded CMC for effective aqueous sequestration of pharmaceutical pollutant via adsorption.

Wastewater is commonly contaminated with many pharmaceutical pollutants, so an efficient purification method is required for their removal from wastewater. In this regard, an innovative tertiary Se/SnO2@CMC/Fe-GA nanocomposite was synthesized through encapsulation of metal organic frameworks (Fe-glutaric acid) onto Se/SnO2-embedded-sodium carboxy methyl cellulose matrix to thoroughly evaluate its effectiveness for adsorption of levofloxacin drug from wastewater. The prepared Se/SnO2@CMC/Fe-GA nanocomposite was analyzed via UV-Vis spectroscopy, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermo gravimetric analysis (TGA), energy dispersive X-ray (EDX), and X-ray diffraction (XRD) to valuate optical property, size, morphology, thermal stability, and chemical composition. The results revealed that prepared Se/SnO2@CMC/Fe-GA nanocomposite was crystalline and porous having average particle size of 6.23 nm with energy band gap of 2.60 eV. Specific heat energy of Se/SnO2@CMC/Fe-GA nanocomposite was found to be 0.028 Jg-1 °C-1. Different experimental factors for example, time, temperature, concentration of LEVO, catalyst dose, ionic strength, and pH were optimized for maximum removal of levofloxacin from wastewater. The tertiary Se/SnO2@CMC/Fe-GA nanocomposite showed 99% removal efficiency for levofloxacin at pH = 7, with contact time of 60 min at 50 °C temperature. The adsorption kinetics followed pseudo-second order. Among adsorption isotherm models, Langmuir model was found most appropriate which revealed that the process was chemisorption. Main mechanism of adsorption is pore diffusion that is confirmed from Bangham, Boyd, Crank and PVSDM kinetic models. Spontaneity and endothermic nature of the process were confirmed by the values of thermodynamic parameters. Toxicity of effluent and impact of interfering ions on adsorption were also investigated. Swelling ratio of Se/SnO2@CMC/Fe-GA nanocomposite was calculated, and nanocomposite showed better results and chemical stability even after five cycles.

An exploration of RSM, ANN, and ANFIS models for methylene blue dye adsorption using Oryza sativa straw biomass: a comparative approach

This study focused on simulating the adsorption-based separation of Methylene Blue (MB) dye utilising Oryza sativa straw biomass (OSSB). Three distinct modelling approaches were employed: artificial neural networks (ANN), adaptive neuro-fuzzy inference systems (ANFIS), and response surface methodology (RSM). To evaluate the adsorbent’s potential, assessments were conducted using Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The evaluation of RSM, ANN, and ANFIS included the quantification of R2, mean squared error (MSE), root mean square error (RMSE), and mean absolute error (MAE) metrics. The regression coefficients from the process modelling demonstrated that RSM (R2 = 0.9216), ANN (R2 = 0.8864), and ANFIS (R2 = 0.9589) all accurately predicted MB adsorptive removal. However, comparative statistical analysis revealed that the ANFIS model exhibited superior accuracy in data-based predictions compared to ANN and RSM models. The ideal pH for MB adsorption utilizing OSSB was established as 7. Additionally, favourable outcomes were obtained with 60-minute contact durations, 20 mg adsorbent quantities, and temperatures of 30 °C. The pseudo 2nd -order kinetic model for MB adsorption by OSSB was confirmed. The equilibrium data exhibited a superior fit with the Langmuir isotherm model in comparison to the Freundlich model. The thermodynamic adsorption parameters, including (∆G = -9.1489 kJ/mol), enthalpy change (∆H = -1457.2 kJ/mol), and entropy change (∆S = -19.03 J mol−1 K−1) indicated that the adsorption of MB onto the OSSB surface is exothermic and spontaneous under the experimental conditions. This research effectively showcased the potential of RSM, ANN, and ANFIS in simulating dye removal using OSSB. The generated parameter data proved valuable for the design and control of the adsorption process.

Inorganic Phosphorus Fractions and Sorption Capacity of Sediments Correlated with Physicochemical Parameters of Water in Langat River, Selangor Malaysia

This study investigates the physicochemical parameters of water, their association with inorganic phosphate fractions, and the sorption capacity of sediments. Water and sediment samples were collected from upstream, midstream, and downstream sections between November 2022 and June 2023. The water samples were analysed according to the American Public Health Association (APHA) guidelines for physicochemical parameters. Inorganic phosphate fractions in the sediments were quantified using the molybdenum blue colourimetric method. Sediment phosphate sorption capacity was assessed by measuring the resulting filtrate and applying regression correlation and Langmuir isotherm models to determine the relationships among the sediment samples. Sediment analysis of inorganic phosphorous fractions revealed varying percentages of Ca-P (32.6%), Rs-P (38.3%), and Fe-P (48.4%) dominating the upstream, midstream, and downstream sections, respectively. Sediment phosphate adsorption varied between sections (upstream: 4.00 to 18.21 mg/g vs. midstream: 4.36 to 21.10 mg/g vs downstream: 4.00 to 12.98 mg/g), with no significant differences between streams at specific phosphate concentrations. However, all the sections displayed a saturation point of approximately 20–25 mg/l. The Langmuir isotherm parameters accurately described P adsorption onto Langat River sediments, as indicated by the moderately high R2 values for Qmax and RL. The downstream section of the Langat River had elevated levels of EC, COD and SRP parameters and Ex-P, Al-P, Fe-P, and Ca-P fractions, except for the Rs-P fraction that dominated the midstream section, indicating collective effects of anthropogenic activities. Therefore, strict regulations to improve wastewater treatment and promote sustainable wastewater management are essential for reducing inorganic phosphorus pollution in the Langat River and protecting water quality.

Nanocellulose/activated carbon composite aerogel beads with high adsorption capacity for toxins in blood.

Activated carbon is extensively utilized in blood purification applications. However, its performance has been significantly limited by their poor blood compatibility. In this work, 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-oxidized cellulose nanofibers (TOCN) and activated carbon (AC) were used to form composite beads by the drop curing method to improve hemocompatibility. The TOCN/AC composite beads had porous surface and exhibited extraordinary adsorption properties. The beads had a high adsorption capacity for creatinine with the optimal adsorption capacity of 83.33 mg g-1. And the equilibrium adsorption of bilirubin, uric acid and Cu2+ by TOCN/AC beads was as high as 159.80 mg g-1, 114.61 mg g-1 and 154.0 mg g-1, respectively, with a mass ratio of TOCN to AC of 1:4. It is also observed that the adsorption behavior of TOCN/AC beads on creatinine was consistent with the second-order kinetics and Langmuir isothermal model. The hemolysis rate of TOCN/AC was 1.21 %, indicating that TOCN/AC beads had good blood compatibility. The clearance of creatinine toxin in blood by TOCN/AC beads was as high as 87 % within 90 min. Overall, our produced composite beads had great potential for application in the field of blood purification.

Cellulose/covalent organic framework aerogel for efficient removal of Cr(VI): Performance and mechanism study.

Cellulose composites have exceptional qualities, particularly in removing heavy metal ions. Nevertheless, these materials' poor mechanical qualities and the restricted exposure of surface-active sites reduce the effectiveness of their removal. The removal efficiency of adsorbent materials largely depends on their macroscopic structural characteristics. This study successfully developed a novel cellulose composite aerogel adsorbent (TBPM). TBPM aerogel possesses not only numerous active sites but also excellent mechanical strength. It is particularly suitable for the efficient removal of hexavalent chromium (Cr(VI))-containing wastewater. The aerogel exhibited a low density of 0.0238 g/cm3 and high porosity of 98.51 %. Incorporating the covalent organic framework (BT-Dg) increased the active sites in the composite aerogel, enhancing its adsorption performance. Compared with other common heavy metal ion adsorbents, the TBPM aerogel demonstrated superior removal performance, with a maximum adsorption capacity of 411.12 mg/g and a removal efficiency of 95.01 % in Cr(VI) solution at 15 °C, pH = 3. The adsorption of Cr(VI) followed pseudo-second-order kinetics and the Langmuir isotherm model. Even after seven adsorption-desorption cycles, TBPM aerogel maintained over 80 % removal efficiency. In addition, the TBPM aerogel successfully filtered 3439 mL of Cr(VI)-containing wastewater. This composite aerogel expands the application of cellulose composites in purifying wastewater.

Removal of hexavalent chromium from aqueous solutions using nano-Fe3O4/waste banana peel/alginate hydrogel biobeads as adsorbent

Abstract In this study, the removal of Cr(VI), known as one of the most dangerous heavy metal pollutants, was investigated by adsorption method using magnetic alginate biopolymer-supported banana peel composite beads (MAB), which were synthesized for the first time. Using plant waste for this composite synthesis is both important in terms of utilization of plant waste and more environmentally friendly. Optimum conditions were determined by examining the parameters of concentration (10–300 ppm), adsorbent dose (1–8 g/L), mixing time (5–360 min), pH (2–8), and temperature (25–55 °C). Characterization of this new synthesized composite adsorbent, FTIR, XRD, SEM, and EDX mapping measurements were performed. The experimentally found adsorption data were modeled by applying Freundlich, Langmuir, Scharthard, Temkin, and D-R isotherm models, and isotherm constants were calculated. The adsorption data on MAB are more compatible with the Langmuir and Freundlich isotherm. In the shaking-batch system at 25 °C and pH = 2, the maximum adsorption capacity of the composite was calculated as 370.4 mg/g. Adsorption kinetics were found to be suitable for pseudo-second-order. Thermodynamic studies were realized to evaluate thermal changes of the adsorption process, and desorption processes were realized to determine the regeneration times of MAB. The temperature studies showed that adsorption capacity increased with increasing temperature, showing that the system was endothermic. As a result, it has been shown that MAB can be used as an efficient biocomposite adsorbent for the removal and recovery of Cr (VI) ions from aqueous media. Graphical Abstract

Adsorptive removal of toxic methylene blue and crystal violet dyes from aqueous solutions using Prunus spinosa: isotherm, kinetic, thermodynamic, and error analysis

Abstract In this study, it was aimed to use Prunus spinosa L. fruit pulp as an adsorbent zero-waste and low-cost for the removal of toxic methylene blue (MB) and crystal violet (CV) dyes from aqueous solutions. The adsorbent was characterized utilizing FTIR-ATR, SEM, and pHpzc tests. The pHpzc value of the adsorbent is 4.96. According to optimization experiments, the optimum adsorbent dosage was determined as 0.05 g/50 mL for MB and CV dyes, the optimum pH values were determined as approximately 7 for MB and CV dyes, and the optimum contact time was determined as 45 min for MB and 30 min for CV dyes. The Langmuir model has been used to calculate the maximum adsorption capacities of MB and CV dyes at a temperature of 298 K. The obtained values are 59.59 mg/g for MB and 53.19 mg/g for CV. The experimental data for Prunus spinosa L. for both dyes exhibited a pseudo-second-order kinetic model. According to error analyses, the reproducibility and applicability of isotherm and kinetic models were investigated. From thermodynamic results, the enthalpy values were calculated as − 42.04 kJ/mol for MB and − 24.08 kJ/mol for CV dyes, which indicates that the process is exothermic. Also, the Gibbs free energies of MB and CV dyes were determined as − 34.20 kJ/mol and − 32.33 kJ/mol at 298 K, which indicates the process is spontaneous. Research and comparisons with other adsorbents have demonstrated that Prunus spinosa L. is a cost-effective and appealing choice for removing MB and CV dyes from water solutions. Graphical Abstract

Novel enhancement strategy for Hg adsorption in wastewater: Nonthermal plasma-mediated advanced modification of zero-valent iron-carbon galvanic cells with thiol functionalization.

Mercury (Hg) pollution poses a critical threat to human health and the environment, necessitating urgent control measures. This study introduces a novel modification method for the common zero-valent iron-carbon (ZVI-AC) galvanic cells using a two-step process, nonthermal (NTP) irradiation followed by targeted functionalization, aiming to enhance Hg adsorption potential by adjusting the physicochemical properties of the cells. The NTP irradiated functionalized adsorbent demonstrated superior Hg adsorption performance across various concentrations and pH variations. Multichannel adsorption mechanisms were confirmed by fitting a total of 22 different adsorption isotherm models, indicating the coexistence of monolayer and multilayer adsorption processes. The NTP irradiation modifies the ZVI and AC, inducing nitrogen and oxygen doping on carbon-based surfaces and oxidizing ZVI to Fe(II)-Fe(III) species. The deepened oxidation of Fe in NTP-Fe-C, coupled with Hg2+ reduction to elemental Hg by raw Fe, contributed to Hg removal. NTP irradiation facilitated electron transfer between Fe and Hg, promoting oxidation of Fe and reduction of Hg2+ cations. The emergence of diverse Hg species further supported the multichannel adsorption/removal mechanism achieved by NTP-irradiated cells. This method offers a promising solution to Hg pollution and expands the application of the traditional iron-carbon galvanic cells in treating hazardous heavy metal wastes.

Gas and Liquid Isotherms: The Need for a Common Foundation.

Sorption isotherms for gases and liquids have long been formulated separately. There is a fundamental problem with this approach: the popular isotherm models (such as Langmuir, BET, and GAB) for gases cannot be applied straightforwardly to sorption from solution. This contrasts with the theory of liquid solutions, where solute-solute interaction, mediated by the solvent, is captured as the potential of mean force, providing powerful interpretive tools (e.g., virial expansion) founded on the gas-liquid analogy. This analogy will be extended to sorption by adopting sorbate numbers and their fluctuations as the common foundation. This enables the gas and liquid isotherm equations to have an analogous mathematical form with a universal language for interfaces and liquid solutions.