Intraparticle Diffusion Kinetic Models Research Articles

Fe2O3/polypyrrole/peanut husk composite for the adsorptive removal of Basic Blue 41 from the aqueous medium: Kinetics, equilibrium modeling and thermodynamic studies

In this study, Basic Blue 41 (BB41) was adsorbed from an aqueous medium using a peanut husk (PH) functional composite with polypyrrole/Fe3O4. For the adsorption of BB41 dye, the effects of process variables including pH, sorbent dose, dye concentration, agitation time, and temperature were investigated. The magnetic composite showed the highest efficiency for the adsorbents at pH 7-10, 0.05 g adsorbent dose, 90 min contact time and 200 mg/L initial dye concentration at 27 °C. The qe was found up to 48 mg/g with percentage removal of up to 96% for BB41 dye for the composite. On the experimental data of BB41 dye, the Langmuir, Freundlich, Temkin, Harkin-Jura, and Dubinin-Radushkevich isotherms were applied. The BB41 adsorption data were also subjected to pseudo-first order, pseudo-second order, and intraparticle diffusion kinetic models. Thermodynamic factors, such as the change in enthalpy (ΔH°), entropy (ΔS°), and Gibbs free energy (ΔG°), were also calculated. The results show that the BB41 adsorption process is exothermic and spontaneous. Techniques such as FT-IR and scanning electron microscopy (SEM) were used to characterize the composite materials. This study demonstrated the promising adsorption potential of magnetic/polypyrrole/peanut husk composites. This class of adsorbent could be used to remediate wastewater that contains dyes.

CuAl-LDH Modified with Filamentous Macroalgae for Anionic Dyes Removal: A Study on Selectivity, Adsorption Efficiency, and Regeneration

Continuous modifications of Layered Double Hydroxides (LDH) materials are essential to enhance their structural stability and improve their capacity for pollutant adsorption, addressing the need for more effective remediation strategies in environmental applications. This research study has proposed the preparation of CuAl-LDH supported filamentous macroalgae of Spirogyra sp. (CuAl-LDH/SA) via coprecipitation and hydrothermal methods. The prepared CuAl-LDH/SA composites were investigated for the adsorption of direct yellow 12 (DY) and remazol red (RR) dyes in batch mode experiments. The structure and morphology of the prepared CuAl-LDH/SA were identified by X-ray Diffraction (XRD), Fourier Transform Infra Red (FT-IR), (Brunauer-Emmett-Teller) BET surface area, Thermogravimetry / Differential Thermal Analyzer (TG/DTA), and Scanning Electron Microscope (SEM). For the adsorption process, the effects of initial pH, contact time, initial concentration, temperature, adsorption selectivity, and adsorbent regeneration, as well as kinetics, isotherms, and thermodynamics were studied. The adsorption selectivity test resulted in the RR dye being more selective compared to DY. The maximum capacities for RR adsorption were 72.464 mg/g (pH = 2, 150 min, 303 K). CuAl-LDH/SA can be regenerated for 4 cycles with a percent removal of 29.32%. The adsorption process followed the intraparticle diffusion kinetics model and Langmuir isotherm. Thermodynamic studies showed that the adsorption of RR using CuAl-LDH/SA was endothermic and spontaneous. The results of this study indicate that CuAl-LDH/SA composite material shows potential material in the removal of anionic dyes from aqueous solutions. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

CoFe2O4/graphene oxide/Ostrich Eggshell/chitosan/polypyrrole nanocomposite for removal 4-nitrophenol

A nanocomposite comprising CoFe2O4/Graphene Oxide/Ostrich Eggshell/Chitosan/Polypyrrole (CF/GO/ES/CS/PPY) was fabricated as both an adsorbent and photocatalyst to examine the adsorption and degradation efficiency of the organic pollutant 4-nitrophenol (4-NP), both in the absence of light and under visible light irradiation. The nanocomposite material outperformed adsorption in photocatalytic experiments conducted using the Box-Behnken Design (BBD) within response surface methodology (RSM), which investigated the correlation between responses and process variables and identified optimal combinations with Design Expert software. Under optimal conditions, the highest percentage of adsorption and degradation of 4-NP was achieved, with a pH of 5.04, concentration of 4-NP of 24.73 mg/L, nanocomposite mass of 0.04 g, and time of 27.64 min, resulting in reported efficiencies of 89.76, and 99.98% for adsorption and degradation, respectively. Upon statistical analysis, it is clear that the Langmuir isotherm model is the best fit for the studied phenomena, displaying a strong correlation (0.990) and minimal error. The data suggests that the intraparticle diffusion kinetic model has the highest correlation coefficient (0.9925) among the models examined. The value of ΔG° computed for the adsorption process exhibits an increase from 1.3704 to 3.9439 kJ/mol as the temperature rises, indicating the non-spontaneous nature of the adsorption process.

In-depth mechanistic insights into Au nanoparticles based polyurethane foams as a selective and efficient dispersive solid phase microextractor for textile dyes from water: performance and reusability study

ABSTRACT Herein, a simple, superhydrophobic, superoleeophilic and low cost microextractor Au nanparticles (Au NPs) based polyurethane (PUFs) solid platform (Au NPs/PUFs) has been developed as a promising sorbent for removal and recovery of Congo red (CR) textile dye from water bodies. The sorbent was characterised using UV-visible and SEM techniques. The procedure relied complete dye retention from the aqueous solution at pH 5.0–5.5 onto an Au NP/PUF extractor. Analytical assessments revealed that the Au NPs/PUFs combination significantly improves mass transfer of dye and enhances creation of active sites for CR retention. CR sorption by the sorbent fitted well with intra-particle diffusion and pseudo first-order kinetic models (R2 = 0.990). The enthalpy change, ΔH (37.8 kJ mol−1) indicates that dye extraction is endothermic whereas the entropy change, ΔS0 (116.6 J mol−1K−1), reveals a significant change in the entropy during dye uptake. The free energy change ΔG (3.12 kJ mol−1 at 298 K) of CR sorption indicated that the dye retention was not spontaneous at all temperatures. A twofold sorption mechanism involving absorption accompanying ‘solvent extraction’ and/or ‘weak ion exchange’, combined with surface adsorption of dye is proposed. Sorbent packed mini column demonstrated effective percent removal and recovery (101.8%) of CR from water samples using acetone or NaOH as an eluting agent. The study expands the utility of Au NPs/PUFs for reusability and spectrophotometric sensing of trace levels of CR in water. The key attention also includes integrating PUFs utility by improving the selectivity and sensing properties towards textile dyes.

Kinetic, equilibrium, and thermodynamic aspects of phenol adsorption onto acrylonitrile-divinylbenzene copolymer

Adsorption of phenol onto acrylonitrile-divinylbenzene copolymer (AN-DVB) was comprehensively investigated with the aspect of kinetic, equilibrium, and thermodynamic. The effect of adsorbent dosage, initial concentration, temperature, and pH were studied in batch adsorption process. Maximum phenol adsorption capacity was obtained at neutral pH of phenol solution (6.8), at room temperature (25 °C) and at higher initial concentrations (500 mg/L) as 117 mg/g. After examining two-parameter- and three-parameter-adsorption-isotherm models, experimental data were represented well by using Freundlich adsorption isotherm model at neutral pH. Due to the all possible interactions like hydrogen bonding, π-π stacking and hydrophobic ineractions have different strengths and energetic values, phenol adsorption at neutral pH (6.8) exhibited a heterogeneous multilayer process. On the other hand, Langmuir and BET models well represented the experimental data obtained beyond neutral pH due to the weakening of different interactions, hence, multilayer but more uniform adsorption occurred. Phenol adsorption followed pseudo-second-order kinetic model that shows the surface interactions play significant role on the adsorption rate. Analysis of Boyd's intraparticle and external diffusion kinetic models indicated that in addition to surface interactions, diffusion also controlled the adsorption rate at room temperature. Activation energy was calculated as 92.99 kJ/mol, which shows the strong interaction between phenol and AN-DVB. Adsorption enthalpy change and entropy change was calculated as −25.731 kJ/mol and −0.041 kJ/molK, respectively. Thermodynamic parameters indicated that adsorption process was exothermic and spontaneous in nature.

Reduction of 2,4-dichlorophenoxy acetic acid herbicide toxicity from aqueous media by adsorption: Experimental and theoretical study using DFT method

This work studies the possibility of reducing the toxicity of water laden with 2,4-dichlorophenoxy acetic acid (2,4-D) using a commercial activated carbon (AC). Multiple structural and textural characterization techniques including Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM/EDS), point of zero charge (pHzpc) determination, Boehm titration, iodine number, Methylene blue index, and BET analysis measurements were performed on the commercial AC. Various parameters affecting adsorption were studied and well-known isotherms models in their linear and non-linear forms were applied for fitting equilibrium data. The kinetic data was analyzed using intraparticle diffusion, pseudo-first and second-order kinetic models. Density functional modeling (DFT) of 2,4-dichlorophenoxyacetic acid was used to investigate the origin of the reactivity. The AC surface area was found to be 1017 m2⋅g−1. A contact time of 30 min, an AC dose of 4 g⋅L−1 and a pH of 6.2 resulted in a maximum adsorption capacity of 235.55 ± 6.43 mg⋅g−1. The thermodynamic study revealed that the adsorption process was physical, spontaneous and endothermic. The adsorption process was governed by second-order kinetics and controlled by intraparticle diffusion.

Green synthesis of magnesium oxide nanoparticles using extracts of two brown seaweeds for removal of acid black 1 dye from aqueous environments

Water pollution by synthetic dyes, particularly acid black 1, poses a significant environmental challenge. The present study has addressed this issue by synthesizing novel magnesium oxide (MgO) nanocomposites using extracts from Padina sanctae crucis (Psc) and Sargassum hystrix (Sh) algae via a sol-gel process. The primary objective was to evaluate the efficacy of these nanocomposites in removing acid black 1 dye from aqueous solutions. The synthesized materials were characterized using Fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis, thermal gravimetric analysis (TGA), and dynamic light scattering (DLS). The results show the successful synthesis of MgONPs and MgO@Sh and MgO@Psc NPs with approximate sizes of 45.64–65.64, 52.14–59.09 and 39.19–58.30 nm. Batch mode experiments were conducted to assess the influence of contact time, pH, and adsorbent dosage on dye removal efficiency. The results demonstrated that at pH 6, increasing the adsorbent dosage from 0.5 to 2 g/L enhanced the dye removal efficiency from 41.6% to 59.1% for MgO@Psc and from 43.4% to 64.1% for MgO@Sh. The Sips isotherm model and intra-particle diffusion kinetic model provided the best fit to the experimental data. The negative values of ΔG° indicated, which the adsorption process is more spontaneous at higher temperatures. This study highlights the potential of MgO@Psc and MgO@Sh nanocomposites as effective adsorbents for acid black 1 removal, offering a promising solution for water purification.

Response surface modelling and optimization for copper removal from acid mine drainage using oxidized Himalayan pine needle biochar

ABSTRACT This study aims to investigate and compare the adsorption behaviour of pine needle biochar (PNB) and H2O2-oxidized PNB (OPNB) in eliminating Cu(II) from acid mine drainage. The PNB and OPNB adsorbents undergo comprehensive characterization through various techniques (BET, FTIR, SEM, and pHPZC). A central composite design was employed for designing experiments and optimizing the impact of process factors (metal concentration, adsorbent doses, contact time, and pH) on adsorption capacity. Pseudo-first-order, pseudo-second-order, and intra-particle diffusion kinetics models as well as Langmuir, Freundlich, and Temkin isotherm models were used to analyze the experimental data. Langmuir isotherm best fit (R2 > 0.99) the experimental data and adsorption capacities of 29.49 and 102.04 mg/g, were determined for PNB and OPNB, respectively. Under optimized experimental conditions, desorption studies revealed the reusability of OPNB about 80% even after four cycles. Fixed-bed column experiments were conducted at ambient temperature with an initial Cu(II) concentration of 125 mg/L and 5.0 g of adsorbent, utilizing a flow rate of 1 mL/min for both PNB and OPNB. These results indicate that oxidized biochar, synthesized for Cu(II) remediation, not only addresses Himalayan pine needle concerns sustainably but also exhibits potential applicability for removing other metal ions from aqueous environments.

Adsorptive removal of anticarcinogen pazopanib from aqueous solutions using activated carbon: isotherm, kinetic and thermodynamic studies

Pazopanib, which is dangerous for aquatic environments due to its toxic and bioaccumulation potential, has been detected at different concentrations in oncology hospital wastewater, sewage, and surface waters. This study aimed to remove pazopanib from wastewater by activated carbon adsorption technique. The effect of the main variables such as initial concentration, pH of pazopanib solution, adsorbent dose, contact time of the phases, and temperature on the adsorption process was evaluated and the optimum adsorption conditions were determined. The experimental data were applied to Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich adsorption isotherm models to describe the adsorption behavior. The experimental data were applied to pseudo-first-order, pseudo-second-order, and intra-particle diffusion kinetic models to describe the adsorption kinetics. Isotherms were established in the 20–50 °C temperature range to study the adsorption equilibrium. According to the results, the highest removal efficiency of pazopanib (95.87%) was obtained at initial concentration (100 mg L−1), adsorbent dose (0.30 g L−1), temperature (20 °C), contact time (120 min) and pH (7.0). The adsorption kinetics was well described by the pseudo-second-order kinetic model (R2 = 0.9998) and the adsorption isotherm by the Langmuir model (R2 = 0.9999). In thermodynamic studies, the negative values of standard enthalpy (ΔH°), standard free enthalpy (ΔG°), and free entropy (ΔS°) indicate that the adsorption process is spontaneous and favorable, i.e. the disorder is reduced. These results indicate that the developed adsorption process can be efficiently and spontaneously applied for the removal of pazopanib from aqueous solutions.

Synthesis of a novel chitosan-TiO2 nanocomposite as an efficient adsorbent for the removal of methylene blue cationic dye from wastewater

This study investigates the efficacy of chitosan-TiO2 nanocomposites (CS-TiO2) as an efficient adsorbent for removing Methylene blue (MB) cationic dye from wastewater. The synthesis of chitosan-TiO2 nanocomposites (CS-TiO2) involved the co-polymerization and crosslinking of Chitosan biopolymer (CS) with titanium dioxide (TiO2). The CS-TiO2 nanocomposites involved their structure, morphology, and characteristics through the utilization of several analytical methods such as FTIR, XRD, SEM, TEM, TGA, UV-visible, DLS, and XPS. The removal of MB dye examined in different concentrations of chitosan exhibits an increase as the pH of the solution increases; the maximum value was attained at pH 6 and 120 minutes of contact time. The optimal dosage of CS-TiO2 nanocomposites for adsorbing methylene blue (MB) was found to be between 0.10 mg/L and 0.20 mg/L. The experimental data was evaluated using the thermodynamic process, Dubinin-Radushkevich, Langmuir, and Freundlich isotherm models. The data were examined using various kinetic models and found to be consistent with pseudo-first order, pseudo-second order, and Intraparticle diffusion kinetics models. Desorption and reuse after adsorption of MB onto CS-TiO2 nanocomposite was investigated using different desorbing agents like NH4OH/NH4Cl or NaOH. These results indicate that CS-TiO2 nanocomposite is a highly effective and cost-effective adsorbent for removing MB dyes from contaminated water.

Assessment of the Detoxification Potential of Modified Biochar from Annona senegalensis Stem Bark on Cr6+ and Cu2+ in Aqueous Solution: An Equilibrium, Kinetic and Thermodynamic Studies

Background: Environmental contamination of the air, water, soil, and food has become a threat to the continued existence of many plant and animal communities in the ecosystem. The chemically activated stem bark of Anonna senegalensis was examined for equilibrium sorption. Methods: This study aimed to assess the adsorption of Cr6+ and Cu2+ onto Annona senegalensis carbon (ASC) according to the following parameters: pH, solution temperature, starting metal ion concentration, agitation duration, dose of adsorbent, particle size, and carbonization temperature using a simultaneous batch adsorption method. Pseudo-first order, pseudo-second order, intra-particle diffusion kinetic, Freundlich, Langmuir, Temkin, and Dubinin-Radushkevich isotherm models were all fitted using the equilibrium sorption data that were produced. Thermodynamic parameters of the adsorption studies were also evaluated. Results: The physicochemical analysis of ASC showed ash content of 7.21 ± 0.02%, moisture content of 11.73 ± 0.29%, and porosity of 0.99 ± 0.08 with bulk density of 0.18 g/cm3. The heavy metalloaded scanning electron microscope (SEM) micrograph showed a filled pit, and the XRD diffractogram, as well as FTIR spectra, revealed peaks that were different from the raw spectra, implying functionalization. The sorption data gave optimum conditions of the adsorption process to be pH of 6, agitation time of 88 minutes, adsorbent dose of 2.5 g/g, initial metal ion concentration of 5 mg/L, temperature of 30°C, particle size of 0.154 mm and carbonization temperature of 400°C. Conclusion: The Langmuir isotherm was found to give the best-fit conformation of all the models based on superior R2 (R2 ≥0.99). Dubinin-Radushkevich proved the mechanism to be physisorption. The pseudo-second-order kinetic model best fits the data with R2 of 0.998 and 0.986 for Cr6+ and Cu2+. Thermodynamic results of the study revealed that ΔHᵒ for Cr6+ and Cu2+ were 32.78 and 27.14 KJ/mol and are all positive, implying an endothermic process and confirming the physisorption mechanism. The entropy change, ΔSᵒ, was also positive, revealing a high degree of disorderliness at the sorbate/sorbent interphase. The standard Gibbs free energy, ΔGᵒ, were all negative, showing spontaneity and feasibility.

Desorption and migration of dissolved organics from oil sands tailings to capped water: Demonstration pit lake

Rate and mechanism of organic compounds desorption from fluid fine tailings (FFT) deposits into the capped water are crucial to understand the geochemical stability of end pit lakes. Specifically, the intricate interplay between electrolyte concentrations and seasonal fluctuations along with their impact on the persistence of organic constituents remains insufficiently elucidated. This study utilized PASS-treated FFT (i.e., permanent aquatic structure storage) from Lake Miwasin to address these questions. Experiments were conducted to investigate the desorption of organics from FFT into lake water under different conditions, including FFT dosage, contact time, temperature, and ionic strength. Results revealed that higher FFT dosage and lake water organic matter led to increased desorption of dissolved organic carbon (DOC), while temperature and conductivity of the lake water had minimal effects. The presence of electrolytes regulated the equilibrium desorption capacity of DOC, with cations (K+ and Ca2+) significantly affecting the desorption process from negatively charged treated FFT particles. Temkin isotherms displayed that desorption dynamics followed physically favorable patterns whereas the Intraparticle diffusion kinetic model suggested the equilibrium desorption capacity of DOC as 0.65 mg/g of PASS-treated FFT. A small percentage (5.82 %) of the DOC and less than half of naphthenic acids (NAs) (39.1 %) in PASS-treated FFT were potentially released. The distribution coefficient value of DOC and NAs was comparably high, indicating that DOC and NAs were mostly stable within the PASS-treated FFT deposition. The study reflects considerable stability of PASS-treated FFT about the physical and chemical conditions of the lake water, making them a promising alternative in FFT management.

Adsorption of arsenic and fluoride: Modeling of single and competitive adsorption systems

The elevated co-occurrence of arsenic and fluoride in surface and groundwater poses risks to human health in many parts of the world. Using single and competitive batch equilibrium adsorption studies, this research focuses on As(V) and F adsorption by activated carbon and its modeling. BET, XRD, FESEM, EDS, and FTIR analysis were used to discern the structural characteristics of activated carbon. The influence of dosage, pH, and contact time were also investigated in single and simultaneous adsorption systems. The maximum adsorption capacity of activated carbon for arsenic and fluoride were found to be 3.58 mg/g and 2.32 mg/g, respectively. Kinetics studies indicated that pseudo-second-order kinetic model fit better than pseudo-first-order, Elovich, and intraparticle diffusion kinetic models. The non-linear regression analysis of Langmuir, Freundlich, Toth, Redlich Petersons, and Modified Langmuir Freundlich models was used to determine single-component asorption model parameters. Additionally, the simultaneous adsorption was rigorously modeled and compared using the Extended Langmuir (EL), Extended Langmuir Freundlich (ELF), Modified Competitive Langmuir (MCL), and Jeppu Amrutha Manipal Multicomponent (JAMM) isotherm models, and competitive mechanisms were interpreted for the simultaneous adsorption system. Further, the model performances were evaluated by statistical error analysis using the normalized average percentage error (NAPE), root mean square errors (RMSE), and the correlation coefficient (R2). According to the modeling results, single equilibrium data fitted better with the Modified Langmuir Freundlich isotherm model, with a higher R2 of 0.99 and lower NAPE values of 3.8 % and 1.28 % for As(V) and F, than other models. For the binary adsorption, the Extended Langmuir Freundlich isotherm model demonstrated excellent fit with lowest errors. All the competitive isotherm models fit the As(V) and F simultaneous sorption systems reasonably well. Furthermore, the research unveiled a nuanced hierarchy of isotherm fitting, with ELF > EL > MCL > JAMM in varying arsenic at a constant fluoride concentration, and ELF > JAMM > EL > MCL in varying fluoride at a constant arsenic concentrations. In addition, competitive studies divulged crucial insights into selective adsorption, as As(V) exhibits a pronounced adsorption selectivity over F on activated carbon. In essence, As(V) showed a more pronounced antagonistic behavior over F, whereas F exhibited a much lesser competitive behavior in the adsorption of arsenic.

UPTAKE OF Co(II), Pb(II) AND Ni(II) IONS BY Annona senegalensis STEM BARK BIOCHAR FROM AQUEOUS SOLUTION: OPTIMIZATION, KINETIC AND THERMODYNAMIC STUDIES

The concern for heavy metal pollution in the environment is especially so since they are non-biodegradable. The use of agro materials in the removal of these heavy metal pollutants has been recognized as a low-cost alternative to the costly conventional remediation techniques. The equilibrium sorption of the chemically activated Anonna senegalensis stem bark was investigated. Using standard techniques, the physicochemical properties of activated carbon (MAASC) were ascertained. By using a simultaneous batch adsorption approach, the adsorption of Co2+, Pb2+, and Ni2+ onto MAASC was examined as a function of pH, solution temperature, initial metal ion concentration, agitation time, adsorbent dose, particle size, and carbonization temperature. The equilibrium sorption data generated were fitted into Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models as well as pseudo first-order, pseudo-second-order and intraparticle diffusion kinetic models. From the obtained results, it was discovered that the Langmuir isotherm provided the best match conformation of all the models, except for Pb2+, which was best for Freundlich with an R2 of 0.95. Physisorption was shown to be the mechanism by Dubinin-Radushkevich. For Co2+, Pb2+, and Ni2+, respectively, the pseudo second-order kinetic model had R2 values of 0.997, 0.999, and 0.999 that best matched the data. Both intraparticle diffusion and the boundary layer effect also contributed to regulating the rates of the adsorption process. The study's thermodynamic results showed that Ho for Co2+, Pb2+, and Ni2+ were 27.51, 19.70, and 13.37 KJ/mol, respectively. These values are all positive and suggest an endothermic reaction, supporting the physisorption mechanism.

ZnO@ activated carbon derived from wood sawdust as adsorbent for removal of methyl red and methyl orange from aqueous solutions

Activated carbon (AC) and ZnO@AC composite derived from wood sawdust were prepared to be utilized as adsorbents for methyl red (MR) and methyl orange (MO) anionic dyes from the aqueous solutions. The maximum adsorption capacity of the AC and ZnO@AC composite toward both dyes was achieved in the strong acidic medium (pH = 3), and under stirring for 60 min. The kinetic studies revealed that the adsorption of MR and MO dyes onto the AC and ZnO@AC composite fitted well with the pseudo-second-order model. Furthermore, the intraparticle diffusion and Elovich kinetic models confirmed the adsorption is controlled by external surfaces, and the adsorption is chemisorption process. The isotherm results indicated that the MR and MO dye adsorption occurred via monolayer adsorption, and the estimated maximum adsorption capacities of both dyes onto the ZnO@AC composite were higher than those achieved by AC. Thermodynamic analysis suggested that the adsorption is endothermic and spontaneous. The mechanism for MR, and MO dyes adsorption onto the AC and ZnO@AC composite is proposed to be controlled by electrostatic bonding, π–π interactions, and ion exchange, while H-bonding and n–π interactions were minor contributors. This study reveals the potential use of carbon-based adsorbents derived from wood sawdust for the removal of anionic dyes from wastewater.

Recycling of waste toner derived from exhausted printer cartridges as adsorbent for defluoridation of water

Due to the broad adoption of electronic and electrical equipment and the quick advancement of contemporary innovations in this domain, significant amounts of electronic waste have been produced. This category of waste includes the toner powder used by printers, copiers, and fax machines to print text and images. This paper describes a sustainable and environmentally friendly method of recycling waste toner powder. The chemical composition of this printer cartridge toner (PCt) powder is carbon, Fe3O4, polypropylene (polymeric resin), and SiO2 composite. Toner powder from exhausted printer cartridges was utilized as an adsorbent to remove fluoride from water. It has a fluoride adsorption capacity of 60 mg/g and a specific surface area of 20 m2/g. X-ray diffraction and electron microscopic investigations were used to investigate the chemical composition, structure, and surface morphology of the material. To analyze the collected experimental data, the Freundlich and Langmuir adsorption isotherm models were used. Time-dependent kinetic experiments were conducted to determine the mechanism of the adsorption process using pseudo-first-order kinetics, pseudo-second-order kinetics, and intraparticle diffusion kinetic models. The fluoride adsorption process was shown to be feasible and spontaneous (ΔG < 0) based on calculated thermodynamic characteristics, which included enthalpy, Gibbs free energy, entropy (ΔS > 0), and adsorption activation energy. The study also discussed its reusability as an adsorbent and examined its functioning capability in actual water.

Mathematical models of the adsorption-desorption kinetics of fenitrothion in clay soil and sandy clay loam soil

Batch adsorption and desorption kinetic experiments of fenitrothion on clay soil and sandy clay loam soil indicated that the equilibration time was approximately 30 hours. The kinetics of adsorption and desorption exhibited two distinct stages: a rapid process in the initial stages followed by a slow process. The pseudo-first-order model followed by the Elovich kinetic model fit the experimental adsorption and desorption data quite well, with high values of R2 and low values of ∆qe% and SSE. Accordingly, the pseudo-first-order model is most suitable for describing the adsorption and desorption kinetics of fenitrothion on clay soil and sandy clay soil. Pseudo-second-order model type-1 and type-2 models fit the experimental adsorption data; however, these models cannot be used to describe desorption kinetics. Moreover, the modified Freundlich model has limited applicability, and the intraparticle diffusion kinetic model cannot describe the kinetics of the adsorption and desorption of fenitrothion on clay and sandy clay loam soils.

Remediation of organic pollutant from the aqueous environment using in-house fabricated polyaniline-based hybrid composite (PANI-MnPBA/NiCoMnS) materials

Polyaniline-based hybrid material (PANI-MnPBA/NiCoMnS) was prepared by hydrothermal-solvothermal approach. Synthesized hybrid material was characterized through FTIR-spectroscopy, p-XRD, SEM, EDX, BET, and Zetasizer techniques. Hybrid material as adsorbent for removal of Congo red (CR) from water system showed excellent results such as 98 % removal efficiency and 254 mg/g adsorption capacity. Furthermore, various studies like adsorption isothermal, kinetic, thermodynamic, and statistical analysis were performed to understand the adsorption phenomenon. From various kinetic models, pseudo-first and second-order kinetic models, intra-particle and liquid film diffusion kinetic models, pseudo-first-order kinetic model, and liquid-film diffusion kinetic model both are most suitable for explaining the adsorption phenomenon due to the greater value of R2 (0.955) for CR. According to these kinetic models, physio-sorption and diffusion play a basic role in the adsorption of CR. Moreover, ΔG (-1779.508 kJ mol−1) and ΔH (61,760.889 kJ mol−1) values explained the spontaneous and exothermic nature of the adsorption process, respectively. Furthermore, for support of the adsorption mechanism via electrostatic attractions before and after the adsorption process FTIR results of as-synthesized adsorbent were measured (NH peaks before 3668.88, after 3541.41 cm−1). These results confirm electrostatic attraction for the adsorption process. Finally, the statistical model was added (n < 1), according to this model, adsorption follows a multi-anchorage approach and adsorbent contains enough sites for adsorption of CR.

Amino- and sulfur-containing POSS for highly efficient and selective extraction of platinum group elements from acidic solution

As the platinum group elements (PGEs) are very important, expensive, and scarce in the earth's crust, the selective extraction and recovery of these elements from electronic wastes is an efficacious strategy to address the increasing demands for these elements' resources. This study reports the design and execution of a novel amino- and sulfur-containing polyhedral oligomeric silsesquioxane (POSS–S-DETA) for highly efficient and selective extraction of precious PGEs such as Pd(II) (PdCl42−) and Pt (IV) (PtCl62−) from acidic aqueous medium. The developed material shows not only very high adsorption efficacies of 505.4 ± 18.1 mg g for Pd(II) and 433.9 ± 13.9 mg/g for Pt (IV), but also proficient selectivity for these PGEs in presence of various interfering metal ions such as Mg(II), Zn(II), Cu(II), Pb(II), Cd(II), and Fe(III). The sorptions of these PGEs accord with the Langmuir isotherm, pseudo-second-order, aswellas intraparticle diffusion kinetic models. The thermodynamic data demonstrates that the sorptions of these PGEs are endothermic and spontaneous. Density functional theory (DFT) calculation shows that strong binding energies are involved among POSS-S-DETA and these PGEs during adsorption. The adsorption mechanism is found to be the electrostatic interaction, hydrogen bonding, and chelate bond formation among the active functional sites of POSS-S-DETA and the used PGEs. The developed material not only demonstrates proficient acid-resistance at pH 1, but also shows excellent repeatability for these PGEs up to eight consecutive cycles. So, these results suggest that the developed POSS-S-DETA has high potential for practical application in the selective adsorptive elimination of PGEs from acidic solution.

Cutting-edge in the green synthesis of MIL-101(Cr) MOF based on organic and inorganic waste recycling with extraordinary removal for anionic dye

MIL-101(Cr) MOF (MIL-Materials of Institute Lavoisier; Metal-organic framework) as an adsorbent has great application in water treatment because of its high stability against air, temperature, and chemicals.Herein, we develop a novel value-added, sustainable, and eco-friendly green method to prepare MIL-101(Cr) hydrothermally based on organic and inorganic waste recycling (G-MIL-101(Cr)@R) without hydrofluoric acid (HF) addition. Several characterization techniques suggest that G-MIL-101(Cr)@R was successfully synthesized. Then, it was used as an adsorbent for acid blue 92 dye (AB-92) as a model of anionic dyes. The adsorption parameters were studied, such as adsorbent dose, contact time, pH, dye concentration, temperature, salinity, and dye selectivity. The results showed that the adsorption of AB-92 is a monolayer according to the Langmuir isotherm with a qmax of 2176 mg/g. Adsorption kinetics follow the pseudo second-order model (R2 = 0.99), occurring in three steps according to the intra-particle diffusion kinetic model. The adsorption of AB-92 over G-MIL-101(Cr)@R is spontaneous and exothermic. The adsorption mechanism is mainly defined by electrostatic interactions. G-MIL-101(Cr)@R can adsorb the anionic dyes more efficiently than cationic dyes. It could also be reused for up to five cycles with an uptake efficiency of not less than 80 % without any change in its structure. Finally, G-MIL-101(Cr)@R is considered a superior adsorbent for anionic dyes. So, it will pave the way for developing MIL-101(Cr), based on organic and inorganic waste recycling, as an efficient adsorbent for removing organic dyes from wastewater.