Adsorption Isotherm Models Research Articles

Protection of stainless steel surfaces in desalination units against corrosion during acid cleaning under dynamic conditions by using lavender angustifolia extract as a green inhibitor

This study investigates the thermodynamics, kinetics, and adsorption mechanisms of Lavender angustifolia extract (LAE) as a corrosion inhibitor for stainless steel (316SS) in desalination units. The primary aim is to evaluate the efficacy of LAE in mitigating corrosion in a 5.0 M HCl solution under dynamic conditions. High-Performance Liquid Chromatography (HPLC) analysis identified key components of the LAE extract that contribute to corrosion inhibition, including linalyl acetate (41.7%), linalool (13.6%), 1,8-cineole (8.3%), β-ocimene (6.2%), terpinen-4-ol (5.7%), lavandulyl acetate (7.5%), and camphor (4.7%). Results indicate that the inhibitory efficiency of LAE increases with concentration, peaking at 94.3% at 300 mg L⁻¹. The Freundlich adsorption isotherm model best describes the experimental adsorption data. Notably, the activation energy for corrosion increases from 7.17 kJ mol⁻¹ in the 5.0 M HCl solution to 21.65 kJ mol⁻¹ with the addition of LAE, reflecting enhanced protection. The enthalpy change (∆H*) in the presence of LAE (19.04 kJ mol⁻¹) is significantly greater than that of the extract-free solution (4.55 kJ mol⁻¹), indicating improved corrosion resistance of 316SS. Electrochemical techniques confirmed the mixed-type inhibition behavior of LAE, while UV and SEM-EDAX analyses demonstrated effective adsorption of the extract on the stainless steel surface.

Temperature Dependence Evaluation of CO2 Adsorption on Eagle Ford Shale using Isothermal Models: A Comparative Study

This study investigates the CO2 adsorption capacity of the Eagle Ford (EF) shale under varying temperatures, utilizing six isothermal adsorption models: Langmuir, Freundlich, Dubinin-Radushkevich (D-R), Sips, Toth, and Brunauer-Emmett-Teller (BET). The shale sample was characterized through Total Organic Carbon (TOC) analysis, X-ray diffraction (XRD), BET surface area analysis, and Field Emission Scanning Electron Microscopy (FESEM) to assess its organic content, mineral composition, pore structure and elemental composition. CO2 adsorption experiments were conducted using a volumetric method at pressures up to 12 MPa and temperatures of 35°C, 55°C, and 70°C. The results revealed that the adsorption capacity increased with pressure but decreased with rising temperature, which is consistent with the exothermic nature of CO2 adsorption. Among the models, Freundlich and Sips provided the best fit for most temperature conditions, highlighting the heterogeneous nature of the shale surface, while the Langmuir, Toth, and D-R models performed well but with slight deviations. The BET model exhibited the poorest fit. Overall, the findings suggest that the EF shale has significant potential for CO2 storage, especially at lower temperatures, with Freundlich and Sips models being the most reliable for predicting adsorption behavior in EF shale formations.

Green adsorbents for water remediation: Removal of Cr(vi) and Ni(ii) using Prosopis glandulosa sawdust and biochar

Abstract Potentially toxic elements like Cr+6 and Ni+2 cause severe health hazards. Therefore, the current work was aimed at cleaning water using Prosopis glandulosa raw sawdust (SD) and its derived biochar (AC). Both the adsorbents were characterized via SEM, FTIR spectroscopy, EDX, and TGA and were applied for the effective removal of Ni(ii) and Cr(vi) at optimum values of experimental conditions, and the mechanism was assessed via adsorption isotherm and kinetic models. The correlation coefficient R 2 confirmed pseudo-second-order kinetics and preferred Freundlich isotherm model. Maximum removal of Cr(iv) was obtained at a pH of 4.0, a bio-sorbent concentration of 0.8 g·L−1, and a temperature of 50°C for 50 min with a metal concentration of 110 ppm, while maximum removal of Ni(ii) was obtained for a contact time of 70 min with a metal concentration of 130 ppm in the above-mentioned experimental conditions. The results of the isotherms and kinetic model revealed that metal adsorption processes involved multilayer formation on the biosorbent’s heterogeneous surface. Also, their thermodynamic investigation showed that the adsorption process is spontaneous and exothermic and, therefore, can be effectively utilized to remove Cr and Ni from water.

Removal of Phosphorus from Water onto Marsh Clam Shell to Predict Contour for Removal Efficiency and Mass of Adsorbent

Anthropogenic activities have resulted in considerable water quality degradation in water sources due to a common problem of the excessive nutrient content (phosphorus) in receiving water, resulting in eutrophication. Even though various wastewater treatment methods have been applied, focusing on phosphorus removal through biological, physical, and chemical treatment, there is still a need to identify the eco-friendly method using the adsorption process and verify the theoretical and experimental data via kinetic and isotherm models. Hence, this study investigates phosphorus removal efficiency from water onto raw marsh clam shells and verifies the experimental and theoretical data with kinetic and isotherm studies. The variable of this study used different masses (2, 4, 6, 8, 10 g) of adsorbents with particle sizes from 1.18 mm to 2.36 mm to remove phosphorus from an aqueous solution (5 mg/L). The physicalchemical properties of adsorbents were examined using X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy Dispersive X-ray Fluorescence (EDXRF), and Fourier Transform Infrared Spectroscopy (FTIR) to support the experimental data and identify the possibility of phosphorus adsorption. The batch experiment data obtained were verified using the kinetic (pseudo-first-order and pseudo-second-order) and isotherm (Langmuir and Freundlich) models. The experiments showed that the best contact time for all masses was 1440 min and the best adsorbent dose was 10 g with 78.0%removal. By comparing the two adsorption isotherm models, the study finds that the adsorption isotherm fits the Langmuir isotherm model with a correlation coefficient, R<sup>2</sup> of 0.9006. The novel use of adsorbent marsh clam shell as a potential adsorbent in the application of future water treatment technologies.

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.

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.

Introducing the Adsorption Energy Distribution Calculation for Two-Component Competitive Adsorption Isotherm Data.

This work introduces the Adsorption Energy Distribution (AED) calculation using competitive adsorption isotherm data, enabling investigation of the simultaneous AED of two components for the first time. The AED provides crucial insights by visualizing competitive adsorption processes, offering an alternative adsorption isotherm model without prior assuming adsorption heterogeneity, and assisting in model selection for more accurate retention mechanistic modeling. The competitive AED enhances our understanding of multicomponent interactions on stationary phases, which is crucial for understanding how analytes compete on the stationary phase surface and for selecting adsorption models for numerical optimization of preparative chromatography. Here, the two-component AED was tested on both synthetic and experimental data, and a very successful outcome was achieved.

Characterization and Adsorption Behavior of Newly Synthesized Aminated Cellulose with Jeffamine EDR148 Towards Ni(II), Cu(II), and Pb(II) Heavy Metal Ions.

Industrial wastewater containing heavy metal ions presents serious economic risk to the environment. In this study, a novel compound of aminated cellulose with jeffamine EDR148 was prepared to improve cellulose's adsorptive behavior towards metal ions. This study undertook a straightforward and efficient cellulose modification through homogeneous chlorination in N,N'-butylmethylimidazolium chloride to produce 6-deoxychlorocellulose (Cell-Cl), followed by a reaction with jeffamine EDR148 and ultimately resulting in the formation of aminated cellulose (Cell-Jef148). Structural and chemical characteristics of Cell-Cl and Cell-Jef148 were determined using different techniques. Various adsorption conditions were applied to evaluate the optimal adsorption conditions for the removal of Cu(II), Ni(II), and Pb(II) ions. Cell-Jef48 revealed a greater affinity and higher adsorption efficiency of 480.3, 420.5, and 463.2 mg/g for Cu(II), Ni(II), and Pb(II) ions, respectively. Different kinetics and adsorption isothermal models were studied to investigate the adsorption mechanism and interactions between Cell-Jef148 and metal ions. The results fitted the Langmuir and pseudo-second-order models. Corresponding to the Langmuir model, Cell-Jef148's maximum adsorption capacities were 952.38, 609.76, and 769.23 mg/g for Cu(II), Ni(II), and Pb(II) ions, respectively, with a high correlation coefficient, R2, in the range of 0.99575-0.99855. The research results of this study support Cell-Jef148's adsorption of heavy metal ions, and the regeneration of adsorbent highlights the potential applications of cellulose-based materials in wastewater treatment.

Lithium Recovery from Reverse Osmosis Concentrate of Geothermal Water by Spinel Type λ-MnO2 -Batch Tests

ABSTRACT Powder and granulated forms of lithium selective spinel type manganese oxide adsorbents (λ-MnO2) were evaluated for adsorption of lithium from the reverse osmosis (RO) concentrate of geothermal water. The interaction between lithium ions and λ-MnO2 adsorbents, in terms of adsorption capacity and uptake rate, was investigated by equilibrium and kinetic studies. In terms of adsorption equilibria, Langmuir isotherm adsorption model accurately represented the adsorption of lithium ions by powder and granulated λ-MnO2 adsorbents from the RO concentrate of the geothermal water. The best description of lithium uptake onto powdered and granulated adsorbents was provided by the pseudo-second-order kinetic model. Additionally, research was carried out with an objective of removing the inhibitory impacts of boron and arsenic on separation of lithium. The λ-MnO2 adsorbent showed no affinity for boron uptake from the solution. However, it exhibited some increasing uptake to arsenic with an increase in amount of the λ-MnO2 adsorbent. But it is possible to eliminate arsenic by means of arsenic selective ion exchange resins Lewatit FO36 and ArsenXnp prior to separation of lithium from the RO concentrate of geothermal water.

Preparation of ZnAl layered double hydroxides supported by silica for the treatment of Cr(VI) and Cu(II) in aqueous solution

A novel adsorbent ZnAl–LDHs/SiO2 (ZA/SiO2) was prepared by blending urea mixture of ZnSO4 and Al2(SO4)3 while using SiO2 as a support form. The adsorption properties of ZA/SiO2 for the removal of toxic metal ions (Cu(II) and Cr(VI)) from water were evaluated. By batch experiment method to investigate the ZA/SiO2 adsorption of Cu(II) and Cr(VI) solution treatment effect. The sorption kinetics curves of Cu(II) and Cr(VI) on ZA/SiO2 were L-shaped. What’s more, the solid concentration effect was found in the process of sorption kinetics. Langmuir and Freundlich sorption isotherm models were used to analyze the adsorption data. The results showed that the adsorption conforms to Langmuir and Freundlich adsorption isotherm models. However, the adsorption capacity of ZA/SiO2 compounds for Cu(II) and Cr(VI) is greatly improved. The adsorption capacity of Cu(II) is 158 mg·g−1 and of Cr(VI) is 176 mg·g−1, which were 3.6 and 1.8 times of ZnAl-LDHs (ZA), respectively. Density functional theory (DFT) was utilized for the analysis of intrinsic mechanism and specific pathways. The primary mechanism for removing Cr(VI) from water mainly included the intercalation of Cr2O72− and exchange between Cr2O72− and OH−, excluding Cr(OH)3 precipitation. Regarding the primary mechanism for eliminating Cu(II) from water, it involves isomorphic substitution as the predominant process, except for the formation of Cu(OH)2 precipitates.

Fabrication of Fe3O4@Polypyrrole@Sulfamic Acid Composite for Efficient Adsorption of Four Cationic Dyes in Aqueous Solution

ABSTRACTWith the continuous development of industry, the issue of industrial wastewater emissions is increasing. Adsorption, as an effective means possessing the features of no pollution, high efficiency, and easy operation, has become one of the effective methods to treat industrial wastewater. Fe3O4@polypyrrole@sulfamic acid (Fe3O4@PPy@SA) composite is successfully prepare by hydrothermal method, in situ polymerization, and modification. Its adsorption behaviors of the composite on MG, MB, CV, and RhB are investigated by UV–Vis, and the impacts of temperature, dye concentration, and the contact time between the composite and the dyes on the adsorption efficiency are researched. The adsorption kinetics and adsorption isotherms exhibit that the adsorption of these four dyes is more in accordance with pseudo‐second‐order kinetic model and Langmuir adsorption isotherm model, the diffusion behaviors are affected through the combined effect of intraparticle diffusion and Boyd membrane diffusion, and the thermodynamic studies display that all these adsorption behaviors are spontaneous heat absorption behaviors. The prepared Fe3O4@PPy@SA is an efficient adsorbent in the field of applications.

In Situ Synthesis of Zr-Doped Mesoporous Silica Based on Zr-Containing Silica Residue and Its High Adsorption Efficiency for Methylene Blue

Zr-containing silica residue (ZSR) is an industrial by-product of ZrOCl2 production obtained through an alkali fusion process using zircon sand. In this study, low-cost and efficient Zr-doped mesoporous silica adsorption materials (Zr-MCM-41 and Zr-SBA-15) were prepared in one step via the hydrothermal synthesis method using ZSR as the silicon source for the removal of methylene blue (MB) from dye-contaminated wastewater. The samples were characterized using X-ray fluorescence (XRF) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetry (TG), and N2 adsorption–desorption measurements. The findings indicate that the synthesized Zr-MCM-41 and Zr-SBA-15 possess highly ordered mesoscopic structures with high specific surface areas of 910 and 846 m2/g, large pore volumes of 1.098 and 1.154 cm3/g, and average pore diameters of 4.18 and 5.35 nm, respectively. The results of the adsorption experiments show that the adsorbent has better adsorption properties under alkaline conditions. The adsorption process obeys the pseudo-quadratic kinetic model and the Freundlich adsorption isotherm model, indicating the coexistence of physical and chemisorption processes. The maximum adsorption capacities of Zr-MCM-41 and Zr-SBA-15 are 618.43 and 516.58 mg/g, respectively, as calculated by the Langmuir model (pH = 9, temperature of 25 °C). Compared with mesoporous silica prepared with sodium silicate as the silicon source, Zr-MCM-41 and Zr-SBA-15 have different structural properties and better adsorption properties due to Zr doping. These findings indicate that ZSR is the preferred silicon source for preparing mesoporous silica, and the mesoporous silica prepared using Zr silicon slag is a promising adsorbent and has great application potential in wastewater treatment.

Carboxymethyl cellulose sodium/bentonite composite adsorbent for Cd(II) adsorption from wastewater

Severely polluting wastewater containing heavy metal ions has become a pressing issue. To address the current shortcomings of natural bentonite (Bent) and carboxymethyl cellulose sodium (CMC) for Cd(II) adsorption, this study developed a cellulose/bentonite composite adsorbent (CMCMW-Bent) via microwave-assisted synthesis using acrylic acid (AA)-modified CMC and pretreated bentonite (Bent), and the adsorbent was used to remove Cd(II) from wastewater. The results show that the strong interaction between AA and CMC, which successfully entered the bentonite layer, and the bentonite provided excellent structural stability and abundant adsorption sites for the adsorption process. Meanwhile, microwave-assisted heating enhanced this unique structure compared to traditional heating with the aqueous solution. The best adsorption effect occurred at pH = 6–7, with a maximum adsorption capacity of 44.76 mg/g for Cd(II). The isothermal adsorption and kinetic models demonstrate that the adsorption process followed the Langmuir adsorption fitting and pseudo-second-order kinetic equations. The thermodynamic study confirms that the adsorption process was a spontaneous endothermic process and a chemical adsorption process. This study provides a new approach for obtaining efficient adsorbents.

Effective removal of heavy metal ions (Pb, Cu, and Cd) from contaminated water by limestone mine wastes

Limestone mining waste and its derived CaO were checked as an adsorbents of pb2+, Cu2+, and Cd2+ ions from water solution. The characterization of Limestone and calcined limestone was studied by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Scanning Electron Microscope (SEM), and Surface area measurements (BET). The optimum conditions of sorbent dosage, pH, initial concentration, and contact time factors were investigated for pristine limestone and calcined limestone absorbents. The results indicate that the optimum initial concentrations of (Ci) were 1200, 500, and 300 ppm for Pb, Cu, and Cd, respectively, using calcined limestone adsorbent, while using the pristine limestone adsorbent, the corresponding optimum initial concentrations were 700, 110, and 50 ppm. In the ternary system sorption, the results indicated that the selectivity sequence of the studied metals by limestone can be expressed as Pb2+ > Cd2+ > Cu2+, while calcined limestone exhibits a higher selectivity for Pb2+ compared to Cu2+ and Cd2+. Hence, various adsorption isotherm and kinetic models were examined to explore different patterns and behaviors of adsorption. So, the results indicate that calcined limestone has great potential for eliminating cationic heavy metal species from industrial water solutions.

Experimental investigation of pyridine removal using vulcanized oil shale

The study systematically conducted orthogonal and univariate experiments to determine the optimal parameters for pyridine removal using vulcanized oil shale. The findings revealed that the key determinants of pyridine adsorption onto vulcanized oil shale included the pH level of the pyridine solution, contact time, initial pyridine concentration, and the quantity of vulcanized oil shale introduced into the system. Under optimal adsorption conditions, the vulcanized oil shale achieved a 48.00% adsorption efficiency and an equilibrium adsorption capacity of 4.83 mg·g−1. In contrast, the untreated oil shale exhibited a comparatively reduced adsorption efficiency of 22.88% under its respective optimal conditions. The research further examined the adsorption kinetics and isothermal adsorption models for both types of oil shale. The kinetic data indicated that pyridine adsorption followed a pseudo-second-order model. The pyridine adsorption isotherms for both oil shale and vulcanized oil shale were best described by the Freundlich model, compared to the Langmuir model. These findings provide significant insights into the utilization of vulcanized oil shale for the efficient treatment of low-concentration pyridine wastewater, potentially contributing to environmental remediation and pollution control strategies.

Loading of anionic surfactant on eco-friendly biochar and its applications in Cr(VI) removal: adsorption, kinetics, and reusability studies

Surfactant-modified biochar is a viable adsorbent for eliminating Cr(VI) from synthetic wastewater. The biochar obtained from the zea mays plant (BC) was tailored with sodium dodecyl sulfate (SDS) as an anionic surfactant forming SDS-BC adsorbent. Different controlling conditions have been evaluated including pH of the solution, biomass concentration, primary Cr(VI) concentration, time of adsorption, and temperature. Under the best controlling circumstances, the percentage of removal has attained 99%. The pseudo-second-order kinetic model best described the removal process, according to the kinetic data, while the Temkin model, one of the applicable adsorption isotherm models, well expressed the adsorption process. The thermodynamic parameters were computed, which disclosed the spontaneity and exothermic character of the Cr(VI) elimination. According to the regeneration cycles, SDS-BC was cost-effective and had a good removal capability.Graphical

Study on stabilization of mercury in wastewater and soil by modified coal-based humic acid residue.

Coal-based humic acid residue (HAS), as a waste generated during humic acid production, has been gaining attention in recent years due to its adsorption capacity and containing nutrients. In this study, to improve the adsorption capacity of HAS for and Hg, phosphate-modified materials (N-HAS) were prepared by a hydrothermal method and HAS and N-HAS were characterized by scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FTIR), X-ray fluorescence (XRF); batch adsorption experiments investigated the adsorption capacity of N-HAS on Hg2+ under different pH, and isothermal adsorption model and kinetic model fitted the adsorption process to explore the adsorption mechanism; the effects of various amounts of N-HAS on the Hg content in maize and the effective Hg in the soil under Hg-contaminated soil were investigated by field trial. The results showed that the pseudo-second-order kinetic model (R2=0.9641) and Langmuir isothermal (R2=0.95) adsorption model could better describe the adsorption behavior of N-HAR on Hg2+, the maximum adsorption amount was 124.20 mg/g, and the time to reach adsorption equilibrium was shorter for N-HAS compared to HAS; after 5 times of adsorption-desorption, the removal rate of Hg2+ by N-HAS was still higher than 80%, with stable cyclic adsorption performance; the adsorption mechanism of Hg2+ by N-HAS included physical adsorption, precipitation, and surface complexation, and compared with HAS, the percentage of complexation for Hg2+ adsorption by N-HAS increased by 77.81%, and the percentage of precipitation increased by 7.68%; compared to the control group, it was shown that the addition of N-HAS significantly decreased (p < 0.05) the Hg content of maize kernels by 27.44% ∼ 72.09%, increased biomass by 4.34% ∼ 11.26%, and decreased the available Hg content in soil by 50.00% ∼ 82.80%. In addition, the addition of N-HAS at 0.4 kg/m2 was optimal for the field trial. The study showed that N-HAS not only achieved resource utilization but also demonstrated great potential for treating Hg2+ in water and soil.

A novel adsorbent based on duck feather for nitrate removal

In this study, the surface of duck feather was modified with (3-chloropropyl) trimethoxysilane and (1,4-diazabicyclo[2.2.2]octane), and it was used as a natural polymeric adsorbent to remove nitrate ion from a solution. The prepared modified duck feather was characterized using TGA, FT-IR, and FE-SEM analyses. The study examined the effect of various parameters such as pH, contact time, adsorbent dosage, and initial concentration of nitrate on adsorption efficiency. pH = 7, 40 min contact time, 30 mg of adsorbent, and 40 mg/L initial concentration of nitrate were found as the optimum conditions offering the maximum efficiency of 91.85% and maximum adsorption capacity of 30.62 mg/g. Also considered were various competing anions together with nitrate ions in the solution. The results revealed that maximum nitrate adsorption could be obtained in the presence of phosphate anion via ion exchange mechanism. It could also offer the best fit for the adsorption isotherm and kinetic model for Langmuir and pseudo-second-order models. The investigation of thermodynamic parameters at 25 °C revealed that the ΔG°, ΔH°, and ΔS° were obtained −5.44, −46.56, and −0.14 kJ mol−1 K−1, respectively.

Evaluation of the efficiency of shell powder as a natural adsorbent for the adsorption of chromium in aqueous solutions: kinetic and thermodynamic approach and modeling of adsorption isotherms

Water pollution by heavy metals such as chromium is a major environmental issue requiring effective remediation solutions. In this study, shellfish powder was used as a natural material to adsorb chromium (III) from aqueous solutions. The results show that shellfish have a significant adsorption capacity, indicating their effectiveness under a variety of conditions. Adsorption kinetics tests showed that the adsorption mechanism followed a pseudo-second-order kinetic model. In addition, thermodynamic parameters show that the adsorption process is a beneficial, spontaneous and endothermic phenomenon. Isotherm models such as Langmuir, Freundlich and Temkin were applied to analyze adsorption behavior. This research could contribute to the development of more sustainable wastewater treatment methods, incorporating natural materials into remediation strategies.

Sorption Equilibrium Behaviour of Post-Characterized Bio-Filled Waste PET (RIC-1) Bottles Composites

The sorption equilibrium of characterized bio-filled waste PET(RIC-1) bottle composites was investigated. Composites were made by melt-mixing of PET(RIC-1) matrix and bio-fillers as crab shell, clay, and chitin. The adsorption capacities of the binary and ternary composites for Fe (III) ions were determined through equilibrium methods from adsorption isotherm models. In terms of equilibrium isotherm application, the ternary composites PET/CHITIN/CLAY and PET/CBS/CLAY fitted best with the Langmuir isotherm (R2 = 0.9861) than the Freundlich isotherm (R2 = 0.9411). The Freundlich isotherm was better suited to the binary composites PET/CBS and PET/CLAY; the physisorption conformity suggested from the Freundlich isotherm was confirmed by the high Polanyi potential (Ɛ2) values greater than 40 kJ/mol in the Dubinin-Radushkevich isotherm. Overall, the findings demonstrate the potential of these composites for adsorption applications and thus open a route of use of PET waste that has become an environmental pollution threat.