Linear Isotherm Model Research Articles

N-doped three-dimensional carbon nanosheets: Facile synthesis and high-concentration dye adsorption

Purification of dye-contaminated wastewater has always been a research hotspot, yet also a challenge, due to high concentration and species diversity of pollutants. The present study designs an efficient nitrogen-doped 3D carbon nanosheets (N-3DCNs) adsorbent with 2592.50 m2 g−1 of specific surface area and 2.68 m3/g of average pore volume based on nitrilotriacetic acid trisodium salt by combining calcination and activation techniques. Microstructure and surface potential of N-3DCNs indicate that a large number of N heteroatoms in the lattice of main material can effectively optimize Zeta potential from 1.53 to −31.08 mV with solution pH increases from 3 to 11. So, as-prepared N-3DCNs possesses necessary conditions for efficient and selective adsorption of cationic dyes due to the abundant adsorption sites and strong electrostatic interactions. When 700 mg/L of cationic rhodamine and anionic methyl orange are respectively used as high concentration industrial dye-contaminated wastewater, N-3DCNs shows 97.97 % and 89.13 % of removal efficiency within 60 min. Furthermore, the adsorption capacity of N-3DCNs displays a wider pH tolerance at 1000 mg/L of cationic concentration, with a maximum adsorption capacity of 4888.70 mg/g at pH = 7 and a minimum value of 4203.77 mg/g at pH = 3, only 14 % of attenuation rate. The kinetics mechanism of dye adsorption could be well explained by pseudo-second-order kinetic model, suggesting chemisorption behavior, while fitting better with the linear Langmuir isothermal model. The groundbreaking and exceptional adsorption performances of N-3DCNs can be attributed primarily to the high specific surface area and negatively charged active sites, facilitating synergistic adsorption.

Occurrence, dissipation kinetics and environmental risk assessment of antibiotics and their metabolites in agricultural soils

Antibiotics are among the emerging contaminants of greatest concern to the scientific community. However, the occurrence and behaviour of their metabolites in soils have been scarcely studied. To address this research gap, this study investigates the occurrence, sorption, dissipation kinetics, and environmental risk of highly important antibiotics (sulfamethazine, sulfadiazine, sulfamethoxazole, trimethoprim) and their main metabolites in Mediterranean agricultural soils. Batch experiments were conducted under natural conditions for 120 days. Five different dissipation kinetics models were applied to elucidate antibiotics degradation. The sorption isotherms were evaluated by three different models. Most of the antibiotics and metabolites tested showed a good fit with the Linear Isotherm model (R2 >0.96) and biphasic dissipation kinetic models (R2 >0.90). The dissipation and the endpoints values (DT50 and DT90) depended on the soil type properties. A Lixisol soil demonstrated reduced degradation of the investigated compounds. Trimethoprim showed the highest persistence, followed by sulfamethazine, sulfamethoxazole, and sulfadiazine. Parent compounds exhibited lower degradation rates than their metabolites. Remaining antibiotic concentrations were found to be below the predicted no-effect concentration in soil, suggesting that they may not pose a risk to terrestrial biota. This study provides valuable insights into the behaviour of these antibiotics and their metabolites in soil.

Adsorption and photocatalytic degradation of 2,4-dicholrophenol using surgical mask derived SMAC-Fe2O3 composite; adsorption isotherms, kinetics, thermodynamics.

Hybrid material of surgical mask activated carbon (SMAC) and Fe2O3 (SMAC-Fe2O3) composite was prepared by simple co-precipitation method and used as potential material for the remediation of 2,4-dicholrophenol (2,4-DCP). The XRD patterns exhibited the presence of SMAC and Fe2O3, FTIR spectrum showed the FeO-carbon stretching at the wavenumber from 400 to 550cm-1. UV-Vis DRS results showed the band gap was 1.97eV and 2.05eV for SMAC-Fe2O3 and Fe2O3, respectively. The SEM images revealed that the Fe2O3 doped onto the fiber morphology of SMAC. The outcomes of the BET examination exhibited a surface area of 195 m2/g and a pore volume of 0.2062 cm3/g for the SMAC/Fe2O3 composite. The batch mode study shows the maximum adsorption and photocatalytic degradation efficacies which were 97% and 78%, respectively. The experimental data was studied with both linear and nonlinear adsorption isotherm and kinetics models. The nonlinear Langmuir isotherm and pseudo-second-order kinetics (PSOK) models have well fit compared with other models. The Langmuir maximum adsorption capacity (qmax) was found 161.60mg/g. Thermodynamic analysis shows that the 2,4-DCP adsorption onto SMAC-Fe2O3 was a spontaneous and exothermic process. The PSOK assumes that the adsorption process was chemisorption. The photocatalytic degradation rate constant of 2,4-DCP was calculated using pseudo-first-order kinetics (PFOK) and the rate constant for SMAC-Fe2O3 and Fe2O3 were 0.859 × 10-2min-1 and 0.616 × 10-2min-1, correspondingly. In addition, the obtained composite exhibited good reusability after a few cycles. These results confirmed that SMAC-Fe2O3 composite is an effective adsorbent and photocatalyst for removing 2,4-DCP pollutants.

Graphene Oxide Covalently Functionalized with 5-Methyl-1,3,4-thiadiazol-2-amine for pH-Sensitive Ga3+ Recovery in Aqueous Solutions.

A novel graphene-based composite, 5-methyl-1,3,4-thiadiazol-2-amine (MTA) covalently functionalized graphene oxide (GO-MTA), was rationally developed and used for the selective sorption of Ga3+ from aqueous solutions, showing a higher adsorption capacity (48.20 mg g-1) toward Ga3+ than In3+ (15.41 mg g-1) and Sc3+ (~0 mg g-1). The adsorption experiment's parameters, such as the contact time, temperature, initial Ga3+ concentration, solution pH, and desorption solvent, were investigated. Under optimized conditions, the GO-MTA composite displayed the highest adsorption capacity of 55.6 mg g-1 toward Ga3+. Moreover, a possible adsorption mechanism was proposed using various characterization methods, including scanning electron microscopy (SEM) equipped with X-ray energy-dispersive spectroscopy (EDS), elemental mapping analysis, Fourier transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Ga3+ adsorption with the GO-MTA composite could be better described by the linear pseudo-second-order kinetic model (R2 = 0.962), suggesting that the rate-limiting step may be chemical sorption or chemisorption through the sharing or exchange of electrons between the adsorbent and the adsorbate. Importantly, the calculated qe value (55.066 mg g-1) is closer to the experimental result (55.60 mg g-1). The well-fitted linear Langmuir isothermal model (R2 = 0.972~0.997) confirmed that an interfacial monolayer and cooperative adsorption occur on a heterogeneous surface. The results showed that the GO-MTA composite might be a potential adsorbent for the enrichment and/or separation of Ga3+ at low or ultra-low concentrations in aqueous solutions.

Cerium-based metal-organic-frameworks with ligand tuning of the microstructures for fluoride adsorption: linear and nonlinear kinetic and isotherm adsorption models.

We present the synthesis and characterisation of three Ce-based metal-organic frameworks (Ce-MOFs) using fumaric acid (Fu), terephthalic acid (BDC), and trimesic acid (H3BTC) as linkers. The use of different linkers influenced the size of the MOF particles, surface area, crystallinity, and microporous structure. The successful implementation of Ce-Fu, Ce-BDC, and Ce-H3BTC MOFs for fluoride ion removal from wastewater was carried out, in which Ce-Fu MOFs exhibited a maximum adsorption capacity (AC) of 64.2 mg g-1. The study also reveals that the use of ultrasound as a mediator for adsorption study over conventional method gives rapid adsorption rate, in which 85% of the fluoride uptake took place just in 10 min and achieved maximum AC in 30 min. The kinetics data were most accurately explained by the pseudo-second-order model (PSO). The existence of co-ions such as NO3-, Cl-, HCO3-, SO42-, Br-, CO32-, and PO43- has a substantial effect on fluoride removal. The mechanism between the fluoride ions and the MOF surface took place via the electrostatic force and the ion exchange process, confirmed using X-ray photoelectron spectroscopy (XPS) and delsa nano. The material is sustained its relatively higher F- ions removal efficiency up to the five cycles. This research might help in the development of novel microporous Ce-based MOFs since it possesses a highly stable crystalline structure in water, suggesting a promising role in aqueous applications.

Removal of Fe and Mn from Co leach solutions by adsorption on activated carbon based on post-consumer polyethylene terephthalate (PET) - Mechanism insights through linear and nonlinear isotherm and kinetic models

ABSTRACT The removal of Fe2+ and Mn2+ from cobalt sulfate-saturated solutions is frequently problematic for Cu-Co hydrometallurgical process performance. Among the applied and developed methods for the removal of these metals, adsorption has drawn less attention. This study investigates on the removal of Fe2+ and Mn2+ in industrial cobalt solutions known as raffinates by adsorption on activated carbon prepared from post-consumer polyethylene terephthalate (PET). The adsorption operating conditions were studied in synthetic solutions and industrial solutions. The Langmuir, Freundlich, and Temkin isotherms were then used to fit the adsorption data, while the pseudo-first-order (PFO), pseudo-second-order (PSO), and Elovich models were used to describe the kinetics. Linear and nonlinear kinetic and isotherm models were studied and compared. Furthermore, intraparticle diffusion (IPD) models were used to study the transfer mass mechanism. The results show that Fe2+ and Mn2+ are removed from Co solutions with the efficiencies of 62.14 and 68.43, respectively. The Langmuir model fits the Fe2+ and Mn2+ adsorption data better, indicating that chemisorption is preferred over physisorption, whereas the Freundlich model fits the Co2+ adsorption data better, indicating that physisorption is preferred over chemisorption. The PFO model describes well the kinetic behavior of Fe2+ and Mn2+, whereas the Elovich model describes better the kinetic behavior of Co2+. According to the IPD model, the step that limits the adsorption of Fe2+, Mn2+, and Co2+ is essentially diffusion through the activated carbon pores. The reported experimental results will highlight the use of activated carbon in the removal of Fe2+ and Mn2+ in Cu and Co hydrometallurgy.

Facile hydrothermal assembly of three-dimensional GO-MTZE composite and its adsorption properties toward Cu2.

Three-dimensional (3D) graphene oxide (GO)-based aerogels, GO and 4-methyl-5-thiazoleethanol (MTZE) composites, were prepared by a facile hydrothermal method. Due to the hydrogen bonding and π-π stacking interactions, the produced 3D GO-MTZE composites possessed large cylindrical structures. The morphologies, composition, and chemical states of 3D GO-MTZE3:1 composite were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and N2 adsorption-desorption isotherms based on the Brunauer-Emmett-Teller (BET) method. The existence of nitrogen (N)-containing heterocyclic system and oxygen (O)-containing branched chain of MTZE contributed to the formation of 3D structures, while the complexation effect of heterocyclic sulfur (S)- and N-containing functional groups of MTZE for metal cations dominated the adsorption performance of 3D GO-MTZE3:1 composite, which could selectively adsorb copper ions (Cu2+). In addition, the better hydrophobic property of 3D GO-MTZE3:1 composite facilitates its facile recycling from aqueous solution after adsorption. The adsorption data of 3D GO-MTZE3:1 composite toward Cu2+ fitted well (R2 = 0.9996) with the linear pseudo-second-order kinetic model, giving an equilibrium rate constant (k2) of 0.0187gmg-1min-1. The linear Langmuir isothermal model could more accurately describe the experimental data, indicating the adsorption process is mainly dominated by the complexation interactions between MTZE and Cu2+. The thermodynamic parameters of ΔG° (< 0), ΔH° (> 0), and ΔS° (> 0) further indicate that the adsorption is a spontaneous and endothermic, confirming that the complexation between Cu2+ and 3D GO-MTZE3:1 composite occurs. Due to its high selectivity for Cu2+, good hydrophobicity, and excellent stability, the developed 3D GO-MTZE3:1 composite possesses might be promisingly used in the aqueous selective enrichment/removal of Cu2+.

Capparis spinosa L waste activated carbon as an efficient adsorbent for crystal violet toxic dye removal: Modeling, optimization by experimental design, and ecological analysis

Textile dyes are dramatic sources of pollution and non-aesthetic disturbance of aquatic life and therefore represent a potential risk of bioaccumulation that can affect living species. It is imperative to reduce or eliminate these dyes from liquid effluents with innovative biomaterials and methods. Therefore, this research aims to highlight the performance of Capparis spinosa L waste-activated carbon (CSLW-AC) adsorbent to remove Crystal Violet (CV) from an aqueous solution. The mechanism of CV adsorption on CSLW-AC was evaluated based on the coupling of experimental data and different characterization techniques. The efficiency of the CSLW-AC material reflected by the equilibrium adsorption capacity of CV could reach more than 195.671 mg·g–1 when 0.5 g·L–1 of CSLW-AC (Particle size ≤250 μm) is introduced into the CV of initial concentration of 100 mg·L–1 at pH 6 and temperature 65° C and in the presence of potassium ions after 60 min of contact time according to the one parameter at a time studies. The adsorption behavior of CV on CSLW-AC was found to be consistent with the pseudo-second-order kinetic model and Frumkin's linear isothermal model. The thermodynamic aspects indicate that the process is physical, spontaneous, and endothermic. The optimization of the process by the Box Behnken design of experiments resulted in an adsorption capacity approaching 183.544 mg·g–1 ([CV]=100 mg·L–1 and [CSLW-AC]=0.5 g·L–1 at 35 min). The results of the Lactuca sativa seeds germination in treated CV (70%), adsorbent solvent and thermal regeneration (more than 5 cycles), and process cost analysis (1.0484 $ L–1) tests are encouraging and promising for future exploitations of the CSLW-AC material in different industrial fields.

Implications of polystyrene and polyamide microplastics in the adsorption of sulfonamide antibiotics and their metabolites in water matrices

Microplastics (MP) and antibiotics coexist in the environment and their combined exposure represents a source of increasing concern. MP may act as carriers of antibiotics because of their sorption capacity. Knowledge of the interactions between them may help improve understanding of their migration and transformation. In this work, the adsorption behaviour of a group of sulfonamides and their acetylated metabolites on different sizes of polyamide (PA) and polystyrene (PS) MP were investigated and compared. Sulfonamides were adsorbed on both MP (qmax up to 0.699 and 0.184 mg/g, for PA and PS, respectively) fitting to a linear isotherm model (R2 > 0.835). A low particle size and an acidic and salinity medium significantly enhances the adsorption capacity of sulfonamides (i.e. removal of sulfamethoxazole increased from 8 % onto 3 mm PA pellets to 80 % onto 50 mm of PA pellets). According to characterization results, adsorption mechanism is explained by pore filling and hydrogen bonds (for PA) and hydrophobic interactions (for PS). After adsorption, surface area was increased in both MP as result of a potential ageing of the particles and the intensity of XRD peaks was higher denoting a MP structure more amorphized. Metabolites were adsorbed more efficiently than their parent compounds on PS while the opposite effect was observed on PA explained by the acetylation of the amine group and, subsequently the reduction of hydrogen bond interactions. Although the dissolved organic matter inhibits sulfonamides adsorption, removal up to 65.2 % in effluent wastewater and up to 72.1 % in surface water were observed in experiments using real matrices denoting the role of MP as vectors of sulfonamide antibiotics in aquatic media.

Design of Experiments for Increasing of Methylene Blue Adsorption onto Cellulose Derivative-Based Composites

Hematite-cellulose acetate composite membranes (M1, M2, and M3) were evaluated for their performance in methylene blue (MB) adsorption. Box-Behnken design was used to evaluate the influence of operational parameters on the adsorption of MB by these adsorbents. The idea was to optimize the process with maximum efficiency on adsorption, through identification of the influential factors to the process, evaluation of interactions between these factors, and modeling mathematical expressions. Adsorption experiments versus time were better described by the non-linear pseudo-first-order model, followed by the pseudo-second-order model, and then the non-linear pseudo-first-order model. The R2 and chi-square values corroborate this finding. Equilibrium data was also evaluated and modeled to the linear and non-linear Langmuir and Freundlich isotherm models. The linear isotherm models were better models to fit the adsorption equilibrium data on the membranes, followed by the non-linear Langmuir model. Thus, it was presumed that chemisorption was the prevailing adsorption mechanism. Additionally, adsorption proved to be exothermic and spontaneous. A quadratic model equation was found to describe the interaction between factors. The coefficients of pH and MB concentration were positive, thus positively affecting the adsorption of MB, but those of the temperature were negative, justifying the negative effect on the adsorption process. Analysis of variance (ANOVA) showed a high coefficient of determination value and a high prediction of the regression model was derived. The highest adsorption capacity was found at the optimum experimental conditions of pH = 9.0, MB initial concentration = 100 mg · L-1 and temperature = 20 ℃. Finally, the composites provided 5 use cycles which is good when considering the adsorbents used in removing textile dyes from wastewater.

Efeito da aplicação do biochar na mobilidade do corante têxtil vermelho drimaren em uma camada de solo aluvionar

ABSTRACT The region of Alto Capibaribe, in the Brazilian semiarid, faces an environmental issue due to contamination from textile activities. Inadequate release of dyes and other toxic substances threatens human health and water resources, such as alluvial reserves. Thus, biochar, a low-cost adsorbent produced by biomass pyrolysis, helps mitigate these problems by increasing soil retention capacity. This study analyzed the effect of applying biochar, produced from coffee husks, a biomass already established in biochar production, at temperature of 530 °C with a pyrolysis time of 10 to 12 hours, in a homemade metallic furnace, resulting in a product with 67.11% carbon. This biochar was applied to evaluate the mobility of the textile dye Red Drimaren, at a concentration of 25 mg.L-1, used for garment dyeing in local industries, in a subsurface layer of an alluvial deposit located in the dry bed of the Capibaribe River. Fourier Transform Infrared Spectroscopy (FTIR) showed that the highest spectral vibrations are in the range of 1400-1800 cm-1, indicating the presence of amine and amide functional groups, favoring the biosorption process. The pH in water is higher than in KCl for all situations, with biochar being basic and the alluvial soil being acidic. The zero charge point values are equal to 6.96 and 7.96 for the proportions Soil+0.25%BC and Soil+1.00%BC, respectively. Layers with 0.25%BC and 1.00%BC added had an increase in adsorptive capacity of 31.68% and 8.62%, respectively, compared to the natural soil sorption capacity. Kinetic data best fit the pseudo-second-order model, and intra-particle diffusion was not the determining mass transfer process nor the occurrence of the adsorption process. Linear and Freundlich isotherm models consistently described the process under varying concentrations, and the Langmuir model did not show a valid physical significance.

Linear and Non-linear Regression Methods to Study the Adsorption of Cr(VI) from an Aqueous Solution Using Pomegranate Peel

In this study, the previous data of the adsorption of Chromium (VI) ions on the pomegranate peels (MPGP) as adsorbents were used. linear and non-linear equations for Langmuir, Freundlich, Dubinin-Radushkevich, Tempkin, Redlich-Peterson, Sips, and Toth adsorption isotherm models were applied. The five error functions ERRSQ, HYBRD, MPSD, ARE, and EABS were analyzed for non-linear isotherm equations and in each case a set of isotherm parameters were determined. The algorithms for the simulation of linear and non-linear isotherm models using error functions were achieved with the aid of Microsoft Excel solver Add-Ins for minimizing the respective error function across the concentration range studied. Linear and non-linear methods show comparable data for two-parameter models, also high R2 values were obtained for Langmuir, Freundlich, and Temkin models while the Dubinin-Radushkevich model reveals low R2 values, on the contrary, three-parameter models show different data between linear and non-linear methods with high R2 value for all. Which indicates that the error does not obey the Gaussian distribution.

Removal of Brilliant Green Dye from Aqueous Solutions Using Multi-walled Carbon Nanotubes (MWCNTs): Linear and Nonlinear Isotherm Models and Error Analysis

Current research explains the comparison of linear and nonlinear regression methods for finding the optimal isotherm study using experimental data for the adsorption of BG on multi-walled carbon nanotubes MWCNTs. BG dye maximum adsorption onto MWCNTs occurred at pH 2 and 35°C, with the apparent equilibrium reached after 15 min. In this study, five error functions were used: ERRS, Hybrid, Chi-square (χ2), ARE, and EABS. The values of error functions suggest that the Langmuir Linear type 3 is a suitable isotherm to describe the adsorption of BG on MWCNTs. The results showed that the Langmuir isotherm is a fit good isotherm to describe the adsorption process. The coefficient of non-determination (K2) showed Hybrid, and ERRS were the preferable error functions used to predict the fit of linear and nonlinear isotherm models. Compared with other studies, MWCNTs can be used as a low-cost adsorbent with low contact time for the removal of BG dye from an aqueous solution.

Applicability of the equilibrium adsorption isotherms and the statistical tools on to them: a case study for the adsorption of fluoride onto Mg-Fe-CO3 LDH

The demand for a low-cost, easy-to-use, low-maintenance system of adsorbents for detoxifying wastewater effluents is growing. A proper understanding of adsorption mechanisms, their controls, and adsorbate-adsorbent behavior is essential. Thus, the current study deals with the required understanding of linear equilibrium adsorption isotherm models. The adsorption data of different concentrations of fluoride onto Mg-Fe-CO3 LDH is fitted to isotherm models. The two-parameter models discussed are Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich, whereas the three-parameter model cited is Redlich-Peterson. To identify the best-fitting model(s) in an equilibrium isotherm study to quantitatively represent the relevant sorption system, various error functions and statistical tools, such as average relative error deviation (ARED), sum of square errors (ERRSQ or SSE), hybrid relative error function (HYBRID), Marquardt’s percent standard error deviation (MPSD), sum of absolute errors (EABS), sum of normalized errors (SNE), correlation coefficient of Pearson (r), coefficient of determination (r2), chi-square test (χ2), student’s T-test and F-test were applied. It is found that the Temkin model best fits the isotherm data, and the sorption process occurs over multiple layers as per the Freundlich isotherm and was found to be more promising than Langmuir’s monolayer sorption process. The exothermic physisorption course for the adsorbate-absorbent interactions is deduced from the isotherm parameters.

Application of novel phytosorbent to sequester chromium(VI) and lead(II) from aqueous phase: Optimization, equilibrium and kinetics

AbstractThis study investigates the potential of Prosopis cineraria leaf powder (PCLP) as a biosorbent for removing heavy metal ions (HMIs) from aqueous solutions. The biosorption characteristics of PCLP were evaluated with respect to pH, contact time, initial concentrations, and biosorbent dosage. Equilibrium data were analyzed using Langmuir, Freundlich, Temkin, and Dubinin‐Radushkevich (D‐R) isotherm models. Langmuir isotherm demonstrated monolayer adsorption for Cr(VI) (R2 = 0.9876) and Pb(II) (R2 = 0.9990), with maximum adsorption capacities of 10.046 and 10.238 mg g−1, respectively. Kinetic analysis showed a good fit to the pseudo‐second‐order (PSO) model, with R2 values of 0.9979 for Cr(VI) and 0.9821 for Pb(II), indicating that H‐bonding and electrostatic interactions were the dominant adsorption mechanisms. Additionally, non‐linear regression analysis was performed to determine the best‐fitting equilibrium model and compared with linear isotherm and kinetic models. The results confirmed that the nonlinear method outperformed the linear method in isotherm analysis. Specifically, the nonlinear Temkin isotherm model exhibited stronger correlation with the experimental data, making it the most suitable model for fitting the equilibrium data. Conversely, the non‐linear pseudo‐second‐order models yielded comparable goodness of fit to the linear kinetic analysis results. Overall, the findings highlight PCLP as a promising, environmentally friendly, and cost‐effective biosorbent for the removal of toxic HMIs, contributing to sustainable environmental management.

Dual-purpose magnetic κ-carrageenan/montmorillonite hydrogel for carrying and removal of tetracycline from aqueous medium

In this work, a novel magnetic adsorbent obtained via the conjugation of montmorillonite clay and κ-carrageenan was fabricated. The successful synthesis of adsorbent was confirmed by various analytical techniques, including Fourier transform infrared spectroscopy, X-ray diffraction, zeta potential measurements, scanning electron microscopy, and N2-adsorption/desorption isotherms. The synthesized material was used as a high-performance sorbent in the removal of tetracycline from aqueous media, and the influential parameters of the process were investigated. It showed high adsorption performance in a wide pH range of 4–11. A maximum adsorption capacity of 80.28 mg g−1 was obtained at 45 °C. Furthermore, the best-fitted kinetic model was found to be the pseudo-second-order model. Regarding two-parameter nonlinear isotherms, best fitting followed the order: Freundlich ≈ Redlich-Peterson > Temkin > Langmuir, which was not the same that was obtained using linear isotherm model regression (Langmuir ≈ Redlich-Peterson > Temkin > Freundlich). Among the different isotherm models, the isotherm data was best fitted to the nonlinear Sips isotherm model. Thermodynamic studies showed the endothermic and spontaneous nature of the adsorption process, as well as its random motion. A plausible mechanism includes hydrogen bonds as well as electrostatic and anion-π interactions as adsorption interactions between tetracycline and the functional groups (O-SO3- and OH–) on the surface of magnetic clay/biopolymer adsorbent.

Operative utilization of the feasible anion exchange membrane BIII for Sorptive exclusion of acid orange 7 from Hydrated media

Anion exchange membranes have received great deal of attention for their ability to remove harmful dye contamination from industrial wastewater while also ensuring profitable and fuel-efficient commercialization. The ability of anion exchange membrane BIII to eradicate acid orange 7 dye from aquatic environment is demonstrated here. SEM and FTIR analyses revealed the surface properties and existence of distinct operational groups on the sorbent. Numerous constraints on AO7exclusion in an aquatic environment, such as contact duration, temperature, sorbent dose, and starting dye concentration were also scrutinized. For the purpose of assessing kinetics, Liquid film diffusion, Elovich, Lagergren first-order, Bangham, pseudo-second-order, and modified Freundlich models, were employed. These findings imply that the AO7 dye sorption onto the BIII membrane is well controlled by the liquid-film diffusion process and that the sorption comprehends pseudo-second-order kinetics with an utmost value of R2(0.99). To evaluate tentative data, multiple linear and nonlinear isotherm models were utilized. Freundlich isotherm was found to be in excellent agreement with sorption data. Thermodynamic specifications, such as a change in Gibb's free energy, enthalpy, and entropy, for dye sorption on the anion exchange BIII membrane were optimized between 308 and 338 K to maximize AO7 dye removal. Since ΔGo is negative and, ΔHo and ΔSo are positive, inferred that the sorption is spontaneous and endothermic. Anion exchange membrane BIII was effective for up to four successive cycles without losing its competence.

Preparation of three-dimensional 2-mercaptothiazoline modified GO aerogel for selective adsorption of Cu2+ in aqueous solution

A novel 3-dimensional graphene oxide/2-mercaptothiazoline (3D GO-MT) aerogel was prepared by using GO and MT which contains heteroatoms (nitrogen-, sulfur-) through a facile hydrothermal assembly process and a following freeze-drying technology. The effects of hydrothermal reaction temperature and GO-to-MT mass ratio on the physicochemical properties of the composites were investigated. The removal of Cu2+ from aqueous solution by 3D GO-MT aerogels was evaluated. The results showed that the composite (GO-MT1:3/100 °C) with GO-to-MT mass ratio of 1:3 prepared at 100 °C had the highest adsorption capacity for Cu2+ (0.5299 mmol g−1). In a bicomponent system of Cu2+/Pb2+, GO-MT1:3/100 °C exhibited higher adsorption selectivity for Cu2+. And the distribution coefficients K of GO-MT1:3/100 ° C for Cu2+/Y3+, Cu2+/Nd3+ in the bicomponent systems were 0.6224 and 0.1253, respectively. The morphology and composition of GO-MT1:3/100 °C, as well as the adsorption mechanism for Cu2+ were investigated by scanning electron microscopy, Brunauer-Emmett-Teller, elemental analysis, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The presence of nitrogen and sulfur on MT heterocycle promoted the possible assembly of MT with GO through π-π stacking and hydrogen bonding interactions. Additionally, the existence of these heteroatoms in MT dominated the metal-chelate affinity of 3D GO-MT aerogel for selective adsorption of Cu2+. The fitted data of kinetics and thermodynamics showed that the adsorption process followed linear pseudo-second-order kinetics and linear Langmuir isotherm model. The adsorption process is non spontaneous and endothermic. The adsorption mechanism of GO-MT1:3/100 °C for Cu2+ involves coordination, cation-π electron interaction, electrostatic attraction and other intermolecular interactions. 3D GO-MT1:3/100 °C can be used as an adsorbent material for selective adsorption/enrichment of Cu2+ in aqueous solution.

Experiments and simulation of adsorption characteristics of typical neonicotinoids in urban stream sediments.

Sediment adsorption is one of the main environmental fates of neonicotinoids (NEOs) in aquatic environments. Little information is available on for the adsorption characteristics of NEOs on urban stream sediments. In this study, urban tidal stream sediments were collected to determine the adsorption properties of four selected NEOs. The influence of environmental factors on NEO adsorption was determined by the RSM-CCD method. The NEO adsorption rates on sediments were established by multiple regression equations. As a result, the adsorption of four NEOs onto sediments fitted a linear isotherm model. The adsorption amounts of thiacloprid (THA), clothianidin (CLO), acetamiprid (ACE), and imidacloprid (IMI) were 1.68 to 2.24, 1.71 to 2.89, 1.88 to 3.07, and 2.23 to 3.16mg/kg, respectively. The adsorption processes of four NEOs on urban sediments were favorable. Moreover, adsorption behaviors of NEOs were typical physical adsorption and readily adsorbed onto urban sediments. The adsorption processes of NEOs were exothermic reactions, and their adsorption rates decreased with increasing pH. Flow rates and organic matter contents could promote the adsorption ratios of typical NEOs. Multiple linear regression was used to assess the relationships between the adsorption rates of NEOs and environmental factors. The p-values of the fitting equations of adsorption rates were all less than 0.05. Within the ranges of concentration of the investigated factors, the multiple regression equations were able to reasonably model and predict the sorption of typical NEOs onto urban stream sediments. Therefore, the adsorption rate equations effectively predicted the NEO adsorption performance of urban streams and were helpful for controlling risk assessment of NEOs.

Preparation of Polyoxometalate-Based Composite by Solidification of Highly Active Cobalt-Containing Polytungstate on Polymeric Ionic Liquid for the Efficient Isolation of Proteinase K.

A novel porous polyoxometalate (POM)-based composite (Co4PW-PDDVAC) was prepared via the solidification of water-soluble polytungstate (Co4PW) on the polymeric ionic liquid dimethyldodecyl-4-polyethylene benzyl ammonium chloride (PDDVAC) via a cation-exchange reaction. The solidification was confirmed by EDS, SEM, FT-IR, TGA, and so on. The strong covalent coordination and hydrogen-bonding interaction between the highly active Co2+ of the Co4PW and the aspartic acid residues of proteinase K endowed the obtained Co4PW-PDDVAC composite with excellent proteinase K adsorption properties. Thermodynamic investigations indicate that the adsorption behavior of proteinase K was consistent with the linear Langmuir isothermal model, giving an adsorption capacity as high as 1428 mg g-1. The Co4PW-PDDVAC composite was applied in the selective isolation of highly active proteinase K from Tritirachium album Limber crude enzyme fluid.