Freundlich Isotherm Model Research Articles

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.

Olive leaf extract-assisted preparation of nanoferrite for adsorptive removal of cationic dye

In this work, magnetic Fe3O4 nanoparticles synthesized with olive leaf extract were used to investigate the adsorption of Basic violet 16 from aqueous solutions. The physicochemical characteristics of Fe3O4 nanoparticles were evaluated by DLS, zeta potential, XRD, FTIR SEM, EDX, N2 adsorption-desorption, TEM, and VSM analyses. Using DLS analysis, the average size of the Fe3O4 nanoparticles was found to be 231.2 nm. Zeta potential studies indicated that the synthesized nanoparticles were moderately stable, and zeta potential was calculated as −14.9 mV. According to TEM analysis, the synthesized nanoparticles ranged in size from 6.28 to 17.3 nm. The optimum parameters for the adsorption of basic violet 16 with Fe3O4 nanoparticles were determined as pH: 9.0, adsorbent dose: 0.8 g, contact time: 210 min, stirring speed: 250 rpm. Langmuir, Freundlich, Dubinin Radushkevich (D-R) and Temkin isotherm models were used to characterize the basic violet 16 sorption data onto Fe3O4 nanoparticles and it was seen that Basic violet 16 adsorption onto the Fe3O4 nanoparticles followed Langmuir isotherm model at all temperatures. The maximum adsorption capacity of Basic violet 16 with Fe3O4 nanoparticles was determined as 117.64 mg/g at 318 K. Pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to describe the adsorption kinetics at 298–318 K. The adsorption followed the pseudo-second-order kinetic model. Adsorption of Basic violet 16 onto Fe3O4 nanoparticles occurred spontaneously and endothermically. Characteristic peaks Fe3O4 nanoparticles were visible in the XRD analysis. The SBET surface area dropped from 110.42 m2/g to 91.27 m2/g after dye adsorption. Peaks in the FTIR analysis showed that Basic violet 16 had been successfully adsorbed on Fe3O4 nanoparticles.

Evaluating the Potential of Modified Mango Leaves as a Biosorbent for the Removal of Mercury (II) Ion and Congo Red from Wastewater

The discharge of harmful metallic elements from industrial byproducts has resulted in notable environmental and public health risks. The aim of this study was to investigate the effectiveness of mango leaves as a cost-effective adsorbent in eliminating Hg (II) ions from industrial effluents. Experimental procedures were carried out under controlled conditions at ambient temperature to evaluate the influence of pH, contact duration, initial metal levels, adsorbent quantity, and temperature on the adsorption mechanism. The most favorable pH for optimal Hg (II) ions adsorption was identified at pH 7. The adsorption process displayed swift kinetics in the initial 30 minutes of contact, leading to a removal rate exceeding 90%, with equilibrium achieved after 70 minutes of stirring. Analysis of kinetics revealed a significant correlation coefficient for a pseudo-second-order kinetic equation. The absorption of Hg (II) ions escalated with increased stirring intensity and decreased adsorbent amount. The interaction between Hg (II) ions, Congo red, and mango leaves was analyzed employing Langmuir, Freundlich, and BET isotherm models. The equilibrium data was best fitted by the Langmuir model, presenting a correlation coefficient of 0.98 and a maximum adsorption capacity of 28.40 mg/g. These results underscore the potential of mango leaves as an affordable bio adsorbent for addressing heavy metal pollution in wastewater.

Cadmium Removal by Adsorption on Biochars Derived from Wood Industry and Craft Beer Production Wastes

Cadmium pollution is a serious environmental issue that has an impact on both the ecosystem and human health. As a result, its removal from water is essential. Agro-industrial wastes are suggested as a sustainable adsorbent option, as they are among the most readily available renewable sources worldwide. Biochar is a carbonized biomass that has been shown to be a viable and novel adsorbent. This article compares the results of cadmium adsorption on biochars derived from wood industry and craft beer production wastes. Biochars were characterized before and after adsorption. Batch adsorption results of 0.18 mmol/L Cd(II) concentration solutions indicated adsorption percentages (A%) of 99.7% and 92.2% for sawdust biochar and barley biochar, respectively. For this cadmium concentration, the sawdust biochar presented an adsorption capacity (qm) of 0.0172 mmol/L, while the barley biochar presented a value of 0.0159 mmol/L. The influence of initial Cd(II) concentration on single and multimetal solutions was studied, and a decrease in Cd(II) adsorption on sawdust biochar was observed in the presence of Ni(II) and Zn(II). The Freundlich isotherm model was found to be the best fit to the data for Cd(II) adsorption isotherms on both biochars. According to the results of this article, sawdust biochar has the best performance as an adsorbent and can be safely disposed of in building bricks at the end of its useful life.

Evaluation of the optical and magnetic properties of novel Nd0.9Zn0.1FeO3 perovskite nanoparticles and their adsorption of Pb2+ ions from water

Nd0.9Zn0.1FeO3 was prepared in a single-phase with an average crystallite size of 25.82 nm using a citrate combustion technique. The energy dispersive X-ray assures the chemical formula of the sample. The elemental mapping of Zn-doped NdFeO3 illustrates the good homogeneous distribution of the elements in the sample. Nd0.9Zn0.1FeO3 has antiferromagnetic properties with weak ferromagnetic components and has good UV absorbance. The values of the band gap for the direct and indirect transitions are 1.473 eV and 1.250 eV, respectively. The adsorption of nickel(II), cobalt(II), chrome(VI), cadmium(II), and lead(II) ions has been studied at pH 7. The highest removal efficiency (η = 73.72%) was observed for the lead ions from water. The current study has examined the kinetics, recoveries, and mechanisms of utilizing Nd0.90Zn0.10FeO3 to remove Pb2+ ions from water. The optimum conditions for the absorbing Pb2+ are pH 7 and a contact time of 60 min. The Freundlich isotherm model is the best model for the absorption of Pb2+ ions. While, the pseudo-second-order kinetic model describes the kinetic adsorption data. The sample has a good efficiency for removing Pb2+ ions from water several times.

Preparation of graphene from polyethylene terephthalate (PET) bottle wastes and its use for the removal of Methylene blue from aqueous solution

We present a method to produce graphene flakes (GFs) from polyethylene terephthalate (PET) bottle wastes by the pyrolysis method using modified bentonite as a catalyst. The as-synthesized GFs are analyzed in terms of crystal phase, morphology, and surface chemistry. The synthesized GFs have a porous, thin, and leaf-like morphology with a length ranging from a few hundred nanometers to a few tens of micrometers. The XRD and FT-IR results confirm the graphitization of PET and the presence of oxygen-containing functional groups on the surface of synthesized GFs. The obtained GFs are used as adsorbents for the removal of methylene blue (MB) from aqueous solution. The effects of various factors including, contact time, pH, and initial MB concentration, on the MB removal efficiency are examined. In addition, the adsorption isotherm models of Langmuir and Freundlich are studied. The best-fitting model is observed with the Freundlich isotherm model.

Synergistic adsorption of methylene blue using ternary composite of phosphoric acid geopolymer, calcium alginate, and sodium lauryl sulfate.

The removal of dyes from the aquatic ecosystem is necessary being a major threat to life. For enhanced remediation of methylene blue (MB) dye, a new ternary biopolymer-geopolymer-surfactant composite adsorbent is synthesized by combining phosphoric acid geopolymer (PAGP), calcium alginate (Alg), and sodium lauryl sulfate (SLS). During the synthesis of the composites, PAGP and SLS were mixed with the alginate matrix, producing porous hybrid beads. The PAGP-SLS-alginate (PSA) beads prepared were characterized using different analytical tools, i.e., scanning electron microscopy (SEM), Fourier transform infrared spectrophotometry (FTIR), X-ray diffractometry (XRD), surface area and porosimetery (SAP), and thermogravimetric analysis (TGA). To ascertain the ideal conditions for the adsorption process, a batch reactor procedure was used to investigate the effects of several parameters on MB adsorption, including pH (2, 4, 6, 8, 10), PSA adsorbent dosage (0.06-0.12 g), MB concentration (50-500 mg/L), contact time (15 to 300 min), and temperature (25, 35, and 45 °C). The SEM investigation indicated that ~ 1860 μm-sized PSA beads with 6-8 μm voids are generated. Based on XRD, FTIR, and SAP examinations, the material is amorphous, having numerous functional groups and an average pore size of 6.42 nm. Variation of pH has a little effect on the adsorption process, and the pH of 7.44 was found to be the pHpzc of the PSA beads. According to the findings of the batch study, equilibrium adsorption was obtained in 270-300 min, showing that the adsorption process was moderately slow-moving and effective. The dye adsorption linearly increased with initial dye concentration over concentration range of 50-500 mg/L and reciprocally decreased with rise in temperature. 0.06 g adsorbent dose, 25 °C, pH10, and 270 min were found to be the better conditions for adsorption experiments. Langmuir isotherm fitted well compared to Freundlich, Temkin, and Dubinin-Radushkevich (DR) isotherm models on the experimental data, and the maximum adsorption capacity(qmax) calculated was 1666.6 mg. g-1. Pseudo-second-order (PSO) kinetics model and multi steps (two) intra particle diffusion (IPD) model fitted well on the adsorption kinetics data. The system's entropy, Gibbs free energy, and change in enthalpy were measured and found to be -109.171 J. mol-1. K-1, - 8.198 to - 6.014 kJ. mol-1, and - 40.747 kJ. mol-1. Thermodynamics study revealed that adsorption process is exothermic, energetically favorable and resulting in the decrease in randomness. Chemisorption is found to be the dominant mechanism as confirmed by pH effect, Langmuir isotherm, PSO kinetics, IPD model, and thermodynamics parameters. PSA beads were successfully regenerated using ethanol in a course of 120 min and re-used for five times. To sum up, the PSA adsorbent's impressive adsorption capability of 1666.66 mg/g highlights its potential as a successful solution for methylene blue removal. The results of this study add to the expanding corpus of information on sophisticated adsorption materials and demonstrate PSA's potential for real-world uses in wastewater treatment and environmental clean-up.

Corrosion mitigation of 6061 aluminium alloy hybrid metal matrix composite using a green inhibitor: experimental and theoretical investigations

Carbohydrate compounds are recognized potent green corrosion inhibitors owing to their structural properties and eco-friendliness. This study showed the effectiveness of glucosamine sulfate (GAS), an eco-friendly green inhibitor, in mitigating the deterioration of 6061 aluminium alloy reinforced with 2% SiC and 2% B4C hybrid composite (6061AA-HMMC) material in 0.1 M hydrochloric acid (HCl) medium. Electrochemical measurements were carried out to quantify the corrosion rate in the absence and presence of the GAS. The results were included in an acceptable adsorption isotherm model, and a suitable mechanism for the corrosion inhibition process was discussed in detail. To comprehend the method of adsorption, the Freundlich isotherm model was applied. Different characterization techniques were used to verify the adsorption of the investigated inhibitor. The optimized structure of the GAS was analysed using density functional theory to provide further insight into its interaction with the metal surface. The infrared (IR) and UV-visible (UV) spectra for the adsorption of the inhibitor molecule were compared with the IR and UV spectra calculated by B3LYP/6-311++G(d, p).

Cd(II) and Zn(II) adsorption on lignite‐derived humic substances and cattle manure biochar

AbstractExcessive industrial release of trace elements may pose a great risk to the environment. Conventional remediation treatments have considerable limitations, making less expensive new technologies an important research area. Batch experiments were conducted at room temperature to investigate the use of two lignite‐derived humic products (nano‐humus and humic powder) and a cattle manure biochar as adsorbents in the removal of cadmium and zinc from laboratory synthesized water. Nano‐humus was most effective in adsorbing Cd(II), wherein 89% adsorption was rapidly achieved in 15 min. The adsorbed amount of Cd(II) and Zn(II) both increased with initial metal ion concentrations from 25 to 125 mg L−1. Despite being produced from the same sources, nano‐humus and humic powder showed different properties and adsorption behaviors. The adsorption mechanism of nano‐humus followed the Freundlich isotherm model and pseudo‐second‐order kinetic model, indicating multilayer chemisorption. Humic powder followed the pseudo‐second‐order kinetic model, although it had a low isotherm model fit, implying chemisorption‐dominated adsorption. Cattle manure biochar followed the Freundlich isotherm and pseudo‐first‐order kinetics model, suggesting diffusion‐dominated multilayer adsorption. Of the three adsorbents tested, nano‐humus had greatest potential as an effective and inexpensive material for metal remediation.

Biosorption of Cadmium by Living and Non‐living Cells of Pseudomonas aeruginosa DR7

ABSTRACTThe global concern over health issues related to heavy metal pollution has driven the adoption of various treatment technologies. The investigation into optimal conditions for cadmium biosorption and bioaccumulation was conducted using a resilient bacterial strain, Pseudomonas aeruginosa DR7, which was isolated from ponds. The equilibrium time of the adsorption process of living cells was much longer than that of non‐living cells, which was about 240 min, which indicates that living cells have intracellular accumulation and delay the adsorption process. Living cells favored a pH of 6.0, while non‐living cells showed higher efficiency at pH 7.0, demonstrating the pH‐dependent nature of metal biosorption. In this context, the maximum biosorption capacities for cadmium using non‐living cells and living cells were 103.8 mg/g and 70.94 mg/g, under cell mass of 1.0 g/L, pH 7.0, initial metal concentration of 200 mg/L, and contact time of 240 min, respectively. Cadmium biosorption by living cells was more accurately described by the Freundlich isothermal model, whereas the Langmuir model was used for non‐living cells. Living cells tend to show pseudo‐second‐order kinetic adsorption behavior, while non‐living cells tend to show pseudo‐first‐order kinetic adsorption behavior. Fourier‐transform infrared spectroscopy (FTIR) analysis suggested that the hydroxyl, amino, and carboxyl groups all play a role in biosorption. Scanning electron microscopy (SEM)–energy dispersive x‐ray spectroscopy (EDS) showed that the high‐temperature treatment destroys the integrity of the cell wall, which enhances the permeability of the cell wall, thus increasing the biosorption of Cd (II) by the non‐living cells. The study found that P. aeruginosa DR7 with high temperature inactivation has a higher Cd(II) adsorption capacity than living cells, making it a green and environmentally friendly biological adsorbent for wastewater treatment with heavy metals.

Effective removal of heavy metals from aqueous solutions using activated biomass: Analytical interpretation via molecular dynamic simulation, mathematical and statistical approaches

Activated carbons basis on low-cost natural materials, Diplotaxis harra (DH) and Glebionis coronaria L. (GCL) were prepared by chemical activation. The optimization of the manufacture conditions is performed by the full factorial design with four variables. Indeed, four activated carbons are prepared, DHACH3PO4, GCLACH3PO4, DHAC-KOH et GCLAC-KOH. The approach used has been evaluated regarding Cd(II) and Co(II) sorption capacities. The optimal conditions for activated carbons preparation are investigated. Therefore, the equilibrium study is assumed using Langmuir and Freundlich isotherm models. Under the optimum conditions, the highest adsorption of Cd(II) is acquired at 118.75 mg/g onto GCLACH3PO4. However, the greater efficiency of Co(II) sorption is obtained onto DHAC- H3PO4 and it was 82.55 mg/g. The current optimization overviews the Cd(II) and Co(II) removal involving various activated carbons. In the theoretical approach, the adsorption affinity of the heavy metal is computed using molecular dynamics (MD) simulation and compared with the adsorption affinity obtained from the experiment. The adsorption energy values were fitted to an empirical interaction energy model to predict the binding energy of arbitrary pollutants. This study used MD simulation to investigate the adsorption mechanism of Cd(II) on the AC (002) surface. The adsorption and interaction energies indicated a feasible, exothermic, and spontaneous adsorption process. MD simulations demonstrate that the adsorption process of Cd(II) on activated carbon is chemical in nature. This result is confirmed by the radial distribution function (RDF) analysis. This research adds new theoretical and experimental findings about heavy metal adsorption using activated carbon.

Employing a magnetic chitosan/molybdenum disulfide nanocomposite for efficiently removing polycyclic aromatic hydrocarbons from milk samples

This study aimed to develop a highly efficient nanocomposite composed of magnetic chitosan/molybdenum disulfide (CS/MoS2/Fe3O4) for the removal of three polycyclic aromatic hydrocarbons (PAHs)—pyrene, anthracene, and phenanthrene. Novelty was introduced through the innovative synthesis procedure and the utilization of magnetic properties for enhanced adsorption capabilities. Additionally, the greenness of chitosan as a sorbent component was emphasized, highlighting its biodegradability and low environmental impact compared to traditional sorbents. Factors influencing PAH adsorption, such as nanocomposite dosage, initial PAH concentration, pH, and contact time, were systematically investigated and optimized. The results revealed that optimal removal efficiencies were attained at an initial PAH concentration of 150 mg/L, a sorbent dose of 0.045 g, pH 6.0, and a contact time of 150 min. The pseudo-second-order kinetic model exhibited superior fitting to the experimental data, indicating an equilibrium time of approximately 150 min. Moreover, the equilibrium adsorption process followed the Freundlich isotherm model, with kf and n values exceeding 7.91 mg/g and 1.20, respectively. Remarkably, the maximum absorption capacities for phenanthrene, anthracene, and pyrene on the sorbent were determined as 217 mg/g, 204 mg/g, and 222 mg/g, respectively. These findings underscore the significant potential of the CS/MoS2/Fe3O4 nanocomposite for efficiently removing PAHs from milk and other dairy products, thereby contributing to improved food safety and public health.

Efficient removal of cationic dyes using lemon peel-chitosan hydrogel composite: RSM-CCD optimization and adsorption studies

The most prominent and easily identifiable factor of water purity is its colour, which may be both physically undesirable, and act as an alert towards potential environmental contamination. The current study describes the optimum synthesis technique for Lemon Peel-Chitosan hydrogel using the Response Surface Methodology integrated Central composite Design (RSM-CCD). This adsorbent is both environmentally friendly and cost-effective. The hydrogel exhibited a maximal dye removal capacity of 24.984, 24.788, 24.862, 23.483, 24.409, and 24.726 mg g−1, for 10 mg L−1 aqueous medium of Safranin O, Methylene blue, Basic fuchsin, Toluidine blue, Brilliant green and Crystal violet, respectively. The adsorption kinetics and isotherm data suggest that the Pseudo second-order kinetic and Freundlich adsorption isotherm models precisely represent the respective behaviour of all the dyes. The thermodynamic viability of the process is determined by the values of ΔG, ΔH, and ΔS. The probable mechanism of adsorption was the electrostatic interaction between the dye molecules and the hydrogel. The regenerated hydrogel had removal efficiencies of over 80 % even after enduring six cycles. Hence, the exceptional recyclability and utility of the adsorbent show their sustainability for wastewater treatment in textile factories.

Hexavalent chromium scavenging performances of one-pot synthesized hydrous cerium-copper-mixed oxide from contaminated water with plausible mechanism

ABSTRACT Prolonged use of the chromate [Cr(VI)]-contaminated water originates severe health problems for the public. Thus, the societal urgency is a reusable and cost-effective material for efficient scavenging of Cr(VI) from contaminated industrial wastewater. Aiming this, we had targeted to prepare some cheap and effective materials for scavenging Cr(VI) from the contaminated water. Herein, we report the preparation of hydrous cerium-copper oxide (HCCO) with some tailored compositions and employed toward the abstraction of chromate from water solution. The HCCO (Ce: Cu = 1:4, mole/mole) has shown the highest Cr(VI) scavenging capacity. Experimentally, highest Cr(VI) abstraction efficiency is recorded at pH ~ 3.0 (508.853 mg. g−1 at 303 K). Kinetically, the Cr(VI) scavenging reaction with HCCO surfaces agrees better with the pseudo second-order model (R2 = 0.987) equation and the equilibrium Cr(VI) distribution data explain the Freundlich isotherm model (R2 = 0.998) equation, which anticipates the multi-layered adsorption on heterogeneous sites of the adsorbent. A negative value of the Gibbs free energy change indicates that the Cr(VI) adsorption over HCCO surfaces is spontaneous. The positive enthalpy change indicates the endothermic nature of the said reaction.

Preparation of low-cost biochar from discarded tea waste for aqueous phase removal of hexavalent chromium [Cr(VI)]: kinetics, isotherm, and recyclability analysis

ABSTRACT The paper reports the application of iron–Jatropha leaf extract functionalized biochar derived from discarded tea waste to remove hexavalent chromium from aqueous matrices. The surface of the FeJa@TB was prepared from discarded tea waste and was functionalized by FeSO4, FeCl3, and Jatropha leaf extract. The batch mode adsorption experiments with various experimental conditions such as pH, contact time, initial adsorbate concentration, and temperature, were conducted to evaluate the ability of the adsorbent to remove Cr(VI). Kinetics of the sorption were analyzed by fitting the sorption data on various models namely, pseudo-first-order, pseudo-second-order, and intra-particle diffusion models. The kinetic study concluded that chemisorption was the chief mechanism for the adsorptive removal of Cr(VI) as the sorption followed a pseudo-second-order model. Sorption data fitted better to the Freundlich isotherm model, suggesting multilayer Cr(VI) coverage onto the biochar surface. Thermodynamic parameters ΔG°, ΔH°, and ΔS° were computed to observe the influence of temperature on the process of sorption. The study concluded that the adsorptive removal of Cr(VI) onto biochar was non-spontaneous and exothermic with fewer randomness at the solid–liquid interface. The prepared biochar was recyclable up to six times with insignificant removal efficiency loss.

Effective Biosorption of Auramin O Dye with Sustainable Chickpea Pods Waste; Isotherms, Kinetics and Thermodynamic Analysis

This study investigated biosorbent properties in removing Auramin O (AO) dye from the aqueous solution of agricultural wastes released from chickpea (Cicer arietinum L.), which is widely produced in Turkey and the world. Biosorption studies were carried out using different values of parameters such as initial AO concentration, dye pH, contact time, temperature, and biosorbent amount. Characterization analyses of the biosorbent used before and after biosorption were carried out by scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Brunauer–Emmett–Teller (BET), Fourier transform infrared spectroscopy (FTIR), and point of zero charge (PZC). Biosorption isotherms were evaluated using Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models. As a result of experimental data, it has been shown that the Langmuir isotherm model (R2 = 0.930) is the most compatible model for biosorption, while the biosorption kinetic mechanism proceeds through the pseudo-second-order (PSO) kinetic model (R2 = 0.965) and the intra-particle diffusion model. As a result of thermodynamic studies, it has been reported that biosorption is endothermic (ΔH0>0), spontaneous (ΔS0>0), and entropy-increasing (ΔG0 <0).

Synthesis and Characterization of Graphene Oxide for Efficient Adsorptive Removal of Hymexazol Pesticide from Aqueous Solutions: Thermodynamic, Kinetic, and Isotherm Studies

Background: Nanomaterials play a significant role in the field of water treatment due to their environment-friendly and appealing physical and chemical characteristics. Objective: The purpose of this research is to evaluate whether graphene oxide adsorbents can effectively remove hymexazol pesticide from an aqueous solution. Methods: Graphene oxide (GO) was prepared by the modified Hummer method, and it was characterized by a number characterization techniques, including XRD, Raman spectroscopy, FE-SEM, TEM, and EDX. Furthermore, the performances of the GO adsorbents for the removal of hymexazol from aqueous solution were investigated. The effect of contact time, GO dosage, initial hymexazol concentration, and temperature was carefully studied. Results: The kinetic experimental data were best described by the pseudo-second-order kinetic model. The equilibrium data were well fitted by the Freundlich and Langmuir isotherm models. The kinetic experimental data were best described by the pseudo-second-order kinetic model. And through the thermodynamic studies, it was found that the adsorption process of hymexazol pesticide is endothermic and spontaneous, in addition to the occurrence of adsorption and absorption together. Conclusions: The findings of the adsorption process demonstrated that graphene oxide is an extremely efficient adsorbent material for pesticide adsorption, owing to its large surface area and the presence of oxygen-rich groups on its surface.

Efficient removal of Chromium(VI) from wastewater based on magnetic multiwalled carbon nanotubes coupled with deep eutectic solvents

Industrial wastewater containing heavy metal Cr(VI) seriously affects the health of organisms and may even lead to cancer. Developing efficient adsorbents that can quickly separate heavy metals is crucial for treating wastewater. In this study, magnetic multiwalled carbon nanotubes (MMWCNTs) with moderate particle size and abundant surface active sites were prepared by coating multiwalled carbon nanotubes with magnetic nanoparticles. The results of FTIR, XRD, TG, VSM, BET, and EDS showed MWCNTs completely encapsulated on the surface of the magnetic nanoparticles, with a particle size of approximately 30 nm. Oxygenated groups provided abundant surface active sites and formed numerous mesopores. The response surface methodology was used to optimize the adsorbent dose, adsorption contact time and adsorption temperature, and the removal rate of Cr(VI) was more than 95%. The quasi-second order kinetics and Freundlich adsorption isotherm model explained the adsorption process to Cr(VI). MMWCNTs interacted with Cr(VI) through electrostatic attraction, reduction reactions, complexation, and other means. The extensive hydrogen bonding of the green solvent deep eutectic solvent (DES) was employed to desorb the MMWCNTs and desorption rate exceed 90%. Even after five adsorption-regeneration cycles, the adsorbent maintained a high capacity. In conclusion, these novel MMWCNTs, as efficient adsorbents paired with DES desorption, hold broad potential for application in the treatment of Cr(VI)-contaminated wastewater.

CTAB Surfactant Promotes Rapid, Efficient, and Simultaneous Removal of Cationic and Anionic Dyes through Adsorption on Glycerol/Citrate Polyester

The discharge of dye waste by industries has caused environmental impacts on water properties, aquatic species, and human life. The production of eco-friendly materials for dye removal from wastewater has gained increasing interest, particularly through adsorption, as it is an efficient method for removing pollutants. However, the selectivity and limited adsorption capacity of materials for simultaneously adsorbing cationic and anionic dyes make it challenging to address the prevailing dye effluent issue. In this work, a poly(glycerol citrate) polyester was prepared without a solvent, using microwave heating, and was combined with cetyltrimethylammonium bromide (CTAB) to modulate the simultaneous adsorption of cationic (Rhodamine B, RB) and anionic dyes (acid blue 113, AB and acid red 27, AR). The formation of the polyester was successfully confirmed by ATR-FTIR and the thermal properties were evaluated by TGA and DCS. In the presence of CTAB 5 mM, the material removes almost 100% of the dyes, reaching the kinetics equilibrium in 30 min following the Pseudo-second order model. Additionally, dye adsorption on the polyester in the presence of CTAB was described by the Freundlich isotherm model, indicating a heterogeneous polyester surface that promotes a multi-layer adsorption driven by electrostatic interaction and hydrogen bonds. The material showed an adsorption capacity of 73.7 ± 3.2, 82.1 ± 4.4, and 21.2 ± 0.6 mg/g for RB, AB, and AR, respectively. Our results provide evidence that the poly(glycerol citrate)/CTAB has a higher potential for application in wastewater treatment to remove both anionic and cationic dyes.

A systematic evaluation of physiochemical properties and solar-driven photocatalytic activity of nanosized Mn doped CdS on Methylene Blue dye

Manganese ions were incorporated into CdS nanosystem using wet chemical protocol at different pH values namely 9.0,10.0 and 11.0 and the same were used for photocatalytic degradation of Methylene blue (MB) dye via adsorption phenomena. Several standard analytical techniques were employed to analyse the synthesized nanocompounds: XRD, scanning electron microscopy with energy-dispersive X-ray spectroscopy, transmission electron microscopy, UV-Vis absorption spectroscopy, Fourier transform infrared spectroscopy, and vibrating-sample magnetometry. The structural analysis revealed the presence of primary cubic zinc blende structure with secondary phases. The morphological studies confirmed the formation of nanostructured particles for all pH values, amongst, pH 10.0 grown particles were showing less agglomeration and better particle stabilization. The TEM analysis confirmed the particle size of 23 nm. The absorption edge and its position shown by UV-Vis absorption analysis exhibited a broad envelope and strong blue shift due to an uneven size distribution and nanodimensional state formation of particles, respectively. The elevation to superparamagnetic state from native diamagnetic state of CdS due to Mn ions incorporation was confirmed by VSM studies. The dual phase composition significantly enhanced the photocatalytic efficiency by improving charge separation and extending light absorption. The MnS phase effectively trapped electrons, reduced recombination rates and facilitated the generation of reactive species. The photocatalytic degradation of methylene blue dye was more efficient (88.87 %) under direct sunlight exposure. Additionally, the enhanced surface properties and adsorption characteristics, as confirmed by the Freundlich isotherm and intraparticle diffusion model, contributed to the superior degradation performance.