Dubinin-Radushkevich Isotherm Research Articles

Low-cost biosorption of Fe(II) and Fe(III) from single and binary solutions using Ulva lactuca-derived cellulose nanocrystals-graphene oxide composite film

The marine algal biomass of Ulva lactuca was utilized for the extraction of cellulose and the development of cellulose nanocrystals/graphene oxide film. Cellulose nanocrystals with 50–150 nm were produced by H2SO4 hydrolysis of the algal cellulose. The adsorption efficiency of the nanocomposite film for Fe(II) and Fe(III) ions was successfully evaluated using Box-Behnken design. The maximum removal for Fe(II) (64.15%) could be attained at pH 5.13, adsorbent dosage 7.93 g L−1 and Fe(II) concentration 15.39 mg L−1, while the biosorption of Fe(III) was 69.92% at pH 5.0, adsorbent dosage 2 g L−1, and Fe(III) concentration 15.0 mg L−1. However, in the binary system, the removal efficiency of Fe(II) was enhanced to 95.48% at Fe(II):Fe(III) ratio of 1:1, while the Fe(III) removal was increased to 79.17% at ratio 1:2. The pseudo-second-order kinetics exhibited better fitting to the experimental results of Fe(II) and Fe(III) adsorption in both single and binary systems. The intra-particle diffusion was prominent during the biosorption, but the effect of the external mass transfer was significant. The Langmuir, Freundlich, Langmuir–Freundlich, Temkin, and Dubinin-Radushkevich isotherms showed satisfactory fitting to the experimental data, but they differ in priority based on iron state and pH. The adsorption of Fe(II) in the presence of Fe(III) in a mixture was best represented by the extended Langmuir model, while the extended Langmuir–Freundlich model best fitted the adsorption of Fe(III). The FT-IR analysis indicated that physisorption through electrostatic interaction/complexation is the predominant mechanism for the adsorption of iron using the nanocomposite film.

Thermodynamic, kinetic, and isotherm studies of Direct Blue 86 dye absorption by cellulose hydrogel

In this study, cellulose hydrogels were simply fabricated by the chemical dissolution method using LiCl/dimethylacetamide as a new method, and the hydrogel produced was investigated for removing Direct Blue 86 (DB86) dye from the aquatic environment. The produced cellulose hydrogel (CAH) was characterized by FTIR, XRD, SEM, and TGA analyses. The removal efficiency of DB86 dye using CAH was achieved via a batch equilibrium process. The impact of pH, time of contact, CAH dosage, starting concentration of DB86 dye, and absorption temperature were scanned. The optimum pH for absorption of DB86 dye was determined to be 2. The absorption results obtained were scanned by Langmuir (LIM), Temkin (TIM), Freundlich (FIM), and Dubinin-Radushkevich (DRIM) isotherm models (IMs) and chi-square error (X2) function used to identify the best-fit IMs. The CAH had 53.76 mg/g as a maximum absorption capacity (Qm) calculated from the LIM plot. The TIM was the best fitted to the CAH absorption results. Kinetic absorption results were investigated by pseudo-first-order (PFOM), Elovich (EM), pseudo-second-order (PSOM), film diffusion (FDM), and intraparticle diffusion (IPDM) models. A PSOM with a high R2 (> 0.99) accounted for the majority of the control over the absorption rate. The findings indicate that CAH can potentially remove the DB86 dye from wastewater.

Performance of molybdenum vanadate loaded on bentonite for retention of cesium-134 from aqueous solutions

This article studied the sorption behavior of Cs(I) ions from aqueous solutions onto molybdenum vanadate@bentonite (MoV@bentonite) composite. MoV@bentonite has been fabricated using the precipitation method and was characterized by different analytical tools including, FT-IR, XRD, and SEM attached with an EDX unit. The sorption studies applied on Cs(I) ions include the effect of contact time, pH, initial metal concentrations, ionic strength, desorption, and recycling. The experimental results revealed that in the adsorption process carried out after equilibrium time (300 min), saturation capacity has a value of 26.72 mg·g−1 and the sorption of Cs(I) ions is dependent on pH values and ionic strength. Sorption kinetic better fit with the pseudo-second-order model; sorption isotherms apply to Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models. Data of thermodynamic parameters indicate that sorption is spontaneous and endothermic. Recycling experiments show that MoV@bentonite could be used for 7 cycles and the best eluant for the recovery of Cs(I) ions is 0.1 M HCl (76.9%). All the obtained data clarify that MoV@bentonite is considered a promising sorbent for the sorption of Cs(I) ions from aqueous solutions.

Radiation synthesis of chitosan/poly(acrylamide-co-maleic acid) hydrogel for the removal of 152+154Eu (III) ions

Using gamma radiation, a chitosan-poly (acrylamide-co-maleic acid) hydrogel was created by copolymerizing acrylamide and maleic acid onto the surface of chitosan. The shape, thermal stability, and structure of the hydrogel were confirmed by Fourier transform infrared analysis, scanning electron microscopy, thermogravimetric analysis, and differential thermal analysis. The batch adsorption of 152+154Eu(III) ions from an aqueous solution showed a rapid initial uptake with an equilibrium time of 24 h at pH (∼4). The Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm models were used to study the adsorption equilibrium data. The adsorption behavior of 152+154Eu(III) ions closely followed the Langmuir isotherm, exhibiting a maximum adsorption capacity of 144.96 mg/g. The adsorption kinetics of 152+154Eu(III) ions are best described by the pseudo-second order model. The thermodynamic parameters were studied and revealed that the adsorption process was spontaneous, exothermic, and favorable at a lower temperature. 0.1 M HCl and AlCl3 desorbed 152+154Eu(III) ions with 97.09% and 88.63%, respectively. Hence, the hydrogel will serve as a starting point for the adsorption of trivalent lanthanide ions in the future.

SYNTHESIS OF ZnAl-LDH/PVA NANOCOMPOSITE AND ADSORPTION OF PATENT BLUE V FOOD DYE FROM WATER SOLUTION

In the presented research work, zinc and aluminum containing layered double hydroxides on the polyvinyl alcohol matrix (ZnAl LDH/PVA) were prepared by the co-formation technique and characterized by X-ray diffractometer, Brunauer-Emmett-Teller (BET) and Ultraviolet-visible (UV-Vis) spectroscopy. Both low and high pH is determined as optimal pH for Patent Blue V (PBV) adsorption on the ZnAl LDH/PVA nanocomposite and it is explained by the fact that the dye molecule is zwitterionic. Sorption of Patent Blue V food additive (E 131) on the obtained nanocomposite was studied by Temkin, Freundlich, Langmuir, and Dubinin-Radushkevich (D-R) isotherm models. Based on the obtained isotherm curves, the adsorption of PBV more closely matches Temkin model. The regenerated nanocomposite shows higher adsorption because the specific surface area increased from 5m2 g-1 to 8.94 m2 g-1 by BET analysis

Insights into adsorption theory of phenol removal using a circulating fluidized bed system

Phenol is one of the most dangerous industrial pollutants in water sources due to its toxic effects on humans and animals. The adsorption process using activated carbon is one of the applicable methods that can be used to remove phenol traces and it is found to be the most efficient due to its various advantages. The present study investigates phenol adsorption using activated carbon which was hand coated onto glass beads. Various calculations were conducted with the data obtained from batch and column adsorption. Kinetic model analysis indicated that the system was best suited for pseudo-second-order kinetics. Thermodynamic parameters such as a change in enthalpy, change in entropy, and change in Gibbs free energy were evaluated, and it can be inferred from the results that this adsorption is endothermic and non-spontaneous for batch study. Physisorption can be inferred from low values of change in enthalpy and change in Gibbs free energy. From the two diffusion models, it was concluded that there is more than one rate-limiting step. The Temkin isotherm model, among the various isotherm models studied, was found to have the best fit with an R2 value of 0.987. The energy value (E) estimated using the Dubinin–Radushkevich isotherm model also proved that the system is physisorption in nature. The column study kinetic calculations indicated that for the column experiment, the process followed was the second-order kinetic model and the thermodynamic report concluded the process to be spontaneous and feasible. MATLAB coding was done for the entire calculations involved in the project, which can be utilized for future applications.

Fly ash and TiO2 modified fly ash as adsorbing materials for removal of Cd(II) and Pb(II) from aqueous solutions

The FA and MFA had been sued to adsorb heavy metals on their surface in this work. For this purpose, fly ash alone is efficient for adsorption, but its efficiency increases when modified with TiO2. TiO2 enhanced the adsorption site of the FA. The study of the surface morphology of FA and MFA by SEM and XRD provides information about their morphology and crystallinity, which is enhanced by modification with TiO2. The crystallinity calculated by Debye-Scherrer's equation was 49.36% for FA, which increased to 79.70%, modifying it with TiO2. The BET analysis reveals that the adsorbent surface area increases after treatment from SBET = 10.79 m2 g−1 (FA) to SBET = 30.59 m2 g−1 (MFA). The adsorption parameters to define the adsorption, such as contact time, temperature, adsorbate concentration, and the adsorbent mass ratio, have been optimized. The TEM analysis revealed that the mean diameter of FA and MFA was 19.45 and 57.71 nm, respectively. The percentage removal of Cd(II) onto FA and MFA was found to be 78.10% and 94.30% and of Pb(II) onto FA and MFA was found to be 75% and 93.10%, respectively at 308 K. The adsorption capacity, qm of Cd(II) onto FA and MFA was found to be 59.20 and 68.80 mg/g, and of Pb(II) onto FA and MFA was found to be 75.30 and 62.70 mg/g, respectively at 308 K. The experimental data had been applied to various adsorption and kinetic models for both FA and MFA, and the order of the best-fitted model was Temkin > Langmuir > Freundlich > Dubinin-Radushkevich isotherm for the adsorption model and pseudo-second-order >pseudo-first-order > intraparticle diffusion for kinetic models.

Adsorption of cationic dye on nanostructured biocarbons: kinetic and thermodynamic study

AbstractNanostructured bio-adsorbents were prepared by physical or chemical activation of the residue of supercritical extraction of raspberry seed. Their physicochemical properties were determined by elemental analysis, low-temperature nitrogen adsorption/desorption, Boehm titration and scanning electron microscopy. The biocarbon obtained as a result of physical activation of the precursor showed basic character of the surface and its SBET was 700 m2/g. The chemical activation of the residue of supercritical extraction of raspberry seed with potassium carbonate favored generation of acidic functional groups and SBET of this biocarbon was 1177 m2/g. The nanostructured biocarbons were used for removal of Rhodamine B from its aqueous solutions. The process was best described by the Langmuir isotherm and the maximum capacity of the monolayer was 181.82 mg/g and 277.83 mg/g for the physically and chemically activated samples, respectively. The adsorption energy obtained from the Dubinin–Radushkevich isotherm indicated that the process observed was physisorption, while the kinetics of the process was best described by the pseudo-second-order model. The negative values of Gibbs free energy indicated the spontaneous character of the process. For the chemically activated sample, the highest sorption capacities toward Rhodamine B were obtained in an acidic environment, while for the physically activated sample—in a basic environment. The yield of desorption decreased for the media: distilled water > hydrochloric acid > acetic acid, which means that Rhodamine B molecules were weakly bound to the biocarbon surface.

Develop and validate a mathematical model to estimate the removal of indoor VOCs by carbon filters

Adsorption-based air filters, especially carbon-based ones, are usually employed to remove VOCs from indoor air. Conducting tests at ppm level, which is substantially higher than the actual indoor concentration of VOCs, is recommended for reducing the test duration. Consequently, developing a model for estimating the service life of adsorptive filters under actual conditions is imperative.A comprehensive model that considers axially dispersed plug flow for interpellet mass transfer and pore surface diffusion model (PSDM) with variable surface diffusivity for intrapellet mass transfer was used to predict the performance of two filters exposed to three VOCs. First, the results of experiments conducted at concentrations ranging from 9 to 90 ppm in a bench-scale setup were used to compute the Dubinin-Radushkevich (D-R) isotherm parameters, which are concentration-independent. Then, the surface diffusivities at zero loading for various adsorbate-adsorbent systems were determined by fitting the developed model into the results of the experimental data performed at concentrations of 9 ppm or 30 ppm. Finally, the model was validated using experimental data which were conducted at lower concentrations, a higher velocity and on a full-scale setup.The inter-model comparison was carried out by comparing the comprehensive model with four other models to study the importance of various mass transfer steps. Finally, in sensitivity analysis, five dimensionless parameters (Pe, St, Edp, Eds and Dg) were examined to investigate their impact on the filter's efficiency.

CARBON FIBERS IN THE ADSORPTION PROCESSES

The parameters of the porous structure of carbon fiber sorbents based on polyacrylonitrile fiber of different activation have been studied. Fibrous carbon sorbents for the adsorption of water-soluble organic compounds have been analyzed. Sorption isotherms were constructed in the coordinates of the Langmuir equation of the studied substances on non-activated and activated carbon fibers, as well as Brunauer-Emmett- Teller isotherms, which allow one to reliably calculate the specific surface area of a carbon fiber sorbent. The sorption isotherms are satisfactorily described by the Freundlich equation. The selectivity of adsorption with a description of adsorption isotherms from solutions of organic substances is considered. It is noted that the linear form of the dependence of the Dubinin-Radushkevich isotherms makes it possible to determine the limiting value of adsorption. The parameters of the «carbon-fiber sorbent-sorbate» systems were calculated using the Dubinin-Radushkevich and Brunauer-Emmett-Teller equations. It is shown that the Dubinin-Radushkevich equations for the analysis of adsorption in the liquid phase make it possible to describe a wider range of relative concentrations than the Langmuir, Frendlich and Brunauer-Emmett-Teller equations. It is shown that the adsorption isotherms for the studied sorbents depend on temperature, and the characteristic curves are not invariant, which does not make it impossible to use the Dubinin-Radushkevich equation to describe adsorption in the liquid phase for the analysis of experimental data on adsorption isotherms. The values of the sorption capacity for extracting organic substances using a carbon fiber sorbent are analyzed. The efficiency of using carbon sorbent based on polyacrylonitrile fiber as a sorbent of organic compounds is shown. For citation: Menshova I.I., Averina Yu.M., Zabolotnaya E. Carbon fibers in the adsorption processes. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 3. P. 52-58. DOI: 10.6060/ivkkt.20236603.6715.

Strong adsorption of CV dye by Ni ferrite nanoparticles for waste water purification: Fits well the pseudo second order kinetic and Freundlich isotherm model

This work focuses on the crystal violet (CV) dye removal from water by using prepared spherical and crystalline nickel ferrite nanoparticles (NiF-NPs) having cubic spinel phase with average size of 28 nm. The toxic, carcinogenic and mutagenic nature of CV dye along with long time persistence in the environment without degradation causes a major impact on living organisms and hence, the removal of CV dye from drinking water is necessary. The experimental batch adsorption data have been analyzed through Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. It is observed that the data fits well in the Freundlich isotherm model as correlation coefficient value (R2) is 0.985, which indicates formation of multilayer coverage over the surface of NiF nanoparticles. Again, Dubinin-Radushkevich's model has provided the adsorption energy (E) of CV dye as 1.629 (kJ/mol), which indicates that dye adsorption takes place through the physical-sorption process. Further, kinetic study indicates that the pseudo 2nd order model is suitable for adsorption data as equilibrium adsorption capacity has been found as 19.58 (mg/g) and R2 value as 0.998 with low value of rate constant (k2) as 0.019 (g mg−1 min−1). Further, R2 value for intra-particle diffusion model is obtained as 0.999, hence it is suitable for explaining the mechanism of adsorption process.

Eco-Friendly Anionic Surfactant for the Removal of Methyl Red from Aqueous Matrices

This study aimed to evaluate the methyl red (MR) removal efficiency from aqueous matrices using an eco-friendly anionic surfactant (a calcium surfactant, or CaSF), obtained from frying oil residue. Data obtained by infrared spectroscopy revealed several functional groups that favor the capture of the dye by chemisorption by forming hydrogen bonds and covalent interactions. The kinetic testing results fit the pseudo-second order model, reaching equilibrium in 30 min. Adsorption was greatly influenced by temperature. The Langmuir isotherm was the one best fitting the process at 20 °C, while the Dubinin–Radushkevich isotherm fitted it better at higher temperatures. Under optimized conditions, the maximal MR adsorption capacity of CaSF reached 53.59 mg·g−1 (a removal rate of 95.15%), proving that the adsorbent at hand can be an excellent alternative for the removal of undesirable levels of MR present in aqueous matrices.

Biosorption of Aqueous Pb(II), Co(II), Cd(II) and Ni(II) Ions from Sungun Copper Mine Wastewater by Chrysopogon zizanioides Root Powder

In this study, a plant-based adsorbent was used in order to remove lead, nickel, cobalt and cadmium metals from a wastewater sample collected from Sungun mine real wastewater. The biosorbent was one of the most abundant native plants of the Sungun region, named Chrysopogon zizanioides (C. zizanioides). The root powder of C. zizanioides was used in order to remove heavy metals from the wastewater sample. The biosorbent was characterized by FTIR, SEM, HR-TEM, EDS, BET and ZPC analyses. The effect of pH, initial metals concentrations, contact time and temperature on the biosorption process were accurately investigated. The metal concentrations were significantly reduced to lower concentrations after the biosorption process, which indicated that the C. zizanioides root powder removal efficiency was more than 95% for the metals from the wastewater sample, with maximum adsorption capacities of 31.78, 21.52, 26.69 and 27.81 mg/g, for Pb(II), Co(II), Cd(II) and Ni(II) ions, respectively. Furthermore, the adsorption kinetic results showed that the pseudo-second-order kinetic model correlated with the experimental data well, with correlation coefficient values of 1 for all metals. Isotherm studies illustrated that the Freundlich and Dubinin-Radushkevich (D-R) isotherm models could describe the obtained equilibrium data well. Moreover, from the D-R model, it was found that the biosorption type was physical. The thermodynamic studies demonstrated that the metals’ biosorption was an exothermic and spontaneous process. Moreover, the reusability of the biosorbent to be used in several successive cycles, and also the percentage of recovery of adsorbed metals from the biosorbent, was investigated. Altogether, being simple and cost-effective and having a high adsorption rate, fast kinetics, easy separation and high reusability prove that C. zizanioides root powder shows significant performance for the removal of heavy metals from waste effluents.

Adsorption Characteristics and Electrochemical Behaviors of Methyl Blue onto Magnetic MgxCoyZn(1-x-y)Fe2O4 Nanoparticles

Magnetic MgxCoyZn(1-x-y)Fe2O4 nanoparticles were successfully prepared by the rapid combustion approach, and SEM, XRD, VSM, EDX, and FTIR techniques were applied for their characterization. The influence of the element ratios (Mg2+, Co2+, and Zn2+) in magnetic MgxCoyZn(1-x-y)Fe2O4 nanoparticles on their properties was explored. To acquire a larger specific surface area for better adsorption of methyl blue (MB), magnetic Mg0.4Co0.5Zn0.1Fe2O4 nanoparticles calcined at 400°C for 2 h with 25 mL anhydrous ethanol were selected, and their average particle size and the saturation magnetization were about 81.3 nm and 13.5 emu·g-1, respectively. Adsorption kinetics models and adsorption isotherm models were applied to research the adsorption characteristics of MB onto magnetic Mg0.4Co0.5Zn0.1Fe2O4 nanoparticles. The pseudo-second-order kinetics model ([Formula: see text]) and Temkin isotherm model ([Formula: see text]) were the most consistent with the data, indicating that the adsorption was the chemical multilayer adsorption mechanism, and the process was an exothermic reaction. The E of the Dubinin-Radushkevich (D-R) isotherm model was 0.2347 KJ·mol-1, indicating the adsorption involved physical adsorption besides chemical adsorption. The [Formula: see text] and [Formula: see text] ([Formula: see text] KJ·mol-1) of the adsorption process of MB adsorbed onto magnetic Mg0.4Co0.5Zn0.1Fe2O4 nanoparticles measured through the thermodynamic experiment were both less than 0, which proved that the process was a spontaneous exothermic reaction. The adsorption capacity of MB onto magnetic Mg0.4Co0.5Zn0.1Fe2O4 nanoparticles increased with the pH of MB solution increasing from 2 to 4 at room temperature, and it had no significant change when the pH of MB solution was 4-12, while the relative removal rate was 98.75% of the first one after 2 cycles. The electrochemical impedance spectroscopy (EIS) and the cyclic voltammetry (CV) data further demonstrated that MB was adsorbed onto magnetic Mg0.4Co0.5Zn0.1Fe2O4 nanoparticles.

Phenol removal from aqueous environments by natural & chemically modified kaolin clay

AbstractNatural, acid and base modified kaolin clays were studied for the sake of phenol and 4‐chlorophenol removal from aqueous environments and their application to real ground and industrial wastewater samples. Scanning electron microscope (SEM), infrared spectroscopy (IR), X‐ray diffraction (XRD), Thermo Gravimetric Analysis (TGA), Differential Thermal Analysis (DTA), and Surface area analysis were employed for characterization of the adsorbents microstructure. Operating factors such as adsorbent dose, solution pH, initial phenol concentration, and contact time were studied. The experimental data displayed that the increase of the adsorbent dose, contact time, and pH value from 2 to 7 increases the efficiency of the removal process. Optimal conditions for phenolic removal were; contact time of 300 min, primary phenol solution of 25 mg/L, pH 7 and 2.5 g/L as an appropriate adsorbent dose using crude (natural), acid modified and base modified kaolin clays. The higher phenolic removal efficiencies were obtained at 5 mg/L as 90, 97, 96.2%, respectively, for the adsorbents in the previously mentioned order. The adsorption capacity in the removal of phenol and 4‐chlorophenol were 7.481 and 4.195, 8.2942 and 3.211, and 8.05185 and 18.565 mg/g, respectively, for the adsorbents in the same mentioned order. The adsorption equilibrium data were fitted and analyzed with four isotherm models, namely, Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm equations. The adsorption process of phenol on studied adsorbents was exothermic, spontaneous and thermodynamically favorable proved by the negative values of their thermodynamic parameters ΔH° and ΔG°. The correlation coefficient (R2) for all concentrations was higher than 0.94, which indicates that in the studied system, the data suitably fit the first‐order kinetics. The % desorption capacity was amounted to 96%, 91.11%, and 87.06% of adsorbed phenol, respectively, for the adsorbents in the previous order using 0.1N NaOH and 10% V/V ethanol solutions as eluents at 25°C, indicating the reusability of the adsorbents. Kaolin and its modified forms can be introduced as eco‐friendly and low‐cost adsorbents in water remediation implementation.

Novel zirconia-halloysite nanotube material for arsenite adsorption from water

Drinking water contaminated with arsenic for a long time will lead to serious human health problems. In this work, to extract arsenite (As(III)) from water, zirconia (ZrO2) loaded on halloysite nanotubes (ZrO2/HNTs) was prepared. ZrO2 nanoparticles were well dispersed on ZrO2/HNTs, and the ZrO2 in this nanohybrid was present in a monoclinic phase. The nanohybrid demonstrated a strong As(III) adsorption capacity (36.08 mg/g) because of the large number of readily accessible hydroxyl groups and its large surface area. The As(III) adsorption on ZrO2/HNTs matched the pseudo-second-order kinetic model and the Langmuir isotherm model, and it was independent of the solution pH. Applying the Dubinin-Radushkevich isotherm model verified that the As(III) removal processes were chemisorption reactions. Studies utilizing X-ray photoelectron spectrometry and Fourier transform infrared analysis revealed that Zr-OH bonds had a significant role in the removal of As(III). In addition, the ZrO2/HNTs nanohybrid demonstrated sufficient As(III) adsorption selectivity with the majority of common coexisting ions present. This research demonstrated the potential of ZrO2/HNTs as a material for the treatment of water polluted with arsenic.

Thermodynamic study of the adsorption of Cd2+ and Ni2+ onto chitosan – Silica hybrid aerogel from aqueous solution

Adsorption studies have been conducted on aqueous solution to investigate the effect of temperature on the sorption of Cd2+ and Ni2+ by Chitosan-silica hybrid aerogel [(CS)hA], which was developed using a blend of components from crab exoskeleton and bamboo biomass and synthesized using sol–gel method. The application of this derived aerogel for clean-up of water bodies polluted with heavy metals at varying temperatures was undertaken with a view to establish its effectiveness. The studied temperatures were 301 K, 308 K, 318 K, 328 K and 338 K at pH 3 and contact time of 180 mins and 60 mins for Cd2+ and Ni2+, respectively. Data obtained were subjected to Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm models which were used to evaluate the adsorption process. Langmuir Isotherm model proved to be the best fit in interpreting the adsorption process with the maximum Cd2+ sorption values within 57.14 to 57.80 mg g−1 while Ni2+ sorption values lie between 52.08 and 58.82 mg g−1. The effect of enthalpy (ΔH°), entropy (ΔS°) and Gibbs free energy (ΔG°) on the sorption of Cd2+ and Ni2+ by the derived aerogel were also deduced. The process is spontaneous, exothermic with the studied ions well aligned on the derived aerogel surface.

Fabrication and characterization of a gum ghatti-cl-poly(N-isopropyl acrylamide-co-acrylic acid)/CoFe2O4 nanocomposite hydrogel for metformin hydrochloride drug removal from aqueous solution

Hydrogels are desirable biomaterials because of their innovative organization structure, which allows them to function with a wide range of hydrophilicity and biocompatibility. Hydrogels, on the other hand, possess sensitive physical characteristics when coupled with live tissue. In the current work, metformin hydrogen chloride (metformin HCl)- loaded the original [Gum ghatti-cl-Poly(N-isopropyl acrylamide-co-acrylic corrosive)/CoFe2O4] nanocomposite hydrogel were orchestrated through the free extreme polymerization strategy utilizing ammonium persulfate (APS) as initiator and N, N′-methylene bis-acrylamide (MBA) as a cross-connecting specialist to eliminate the metformin hydrochloride drug from watery arrangements. The influence of numerous parameters on the amount of adsorbate, including pH, temperature, equilibrium time, and adsorbate weight, was investigated, and the ideal conditions for preparing adsorbate were determined. The hydrogel was characterized using FTIR, XRD, AFM, FESEM, and TGA methods. Three powerful models viz. pseudo-first order, pseudo-second order, and intraparticle scattering model, were used and fitted to the equilibrium data to choose the adsorption part of metformin adsorption onto Gg-cl-poly(NIPA-co-AA)/CoFe2O4 nanocomposite hydrogel. The adsorption isotherm information was explored with the assistance of four isotherm models viz. Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (DRK) isotherms. The metformin adsorption process followed the pseudo-second-order model and Langmuir adsorption isotherm with a most extreme adsorption limit of 151.07 ​mg/g. To investigate the adsorption nature and promptness metformin, a couple of thermodynamic limits were estimated and observed that the adsorption system is exothermic and unconstrained.

Batch adsorption of safranin dye from aqueous solution using activated groundnut pods (AGP)

This work aimed on the adsorption of safranin dye from wastewater using activated groundnut pods (AGP). The raw pods were collected, crushed into particle size of about 400 - 550 μm and modified in-situ with ZnCl2 to prepare AGP which was characterized using analytical technique; Fourier Transform Infra-Red (FTIR), Energy Dispersive X-ray (EDX) spectroscopy, Thermo gravimetric analyser (TGA) and Scanning Electron Microscopy (SEM). The absorbance of the dye solution was monitored at 530 nm with UV-Visible spectrophotometer. FTIR analysis showed the vibration frequency for C‒H, O‒H, C=O and C‒O stretches at 2900, 3420, 1730, and 1100 cm-1 respectively. SEM results revealed the AGP has a porous surface with heterogeneous pores which became compact after dye adsorption. EDX confirmed the presence of C, O, Zn and Cl in the adsorbent. The suitability of the pseudo-first, pseudo second and Elovich kinetic models for the sorption of safranin onto AGP was examined. The equilibrium data were subjected to Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich isotherm models. Adsorption factors were optimized by Box-Behnken design using response surface methodology (RSM). The pseudo-second order kinetic model provided the best correlation and was found to be more statistically significant. Langmuir model was found to fit well based on the high values of the coefficient of regression R2 and low % standard error values. The monolayer adsorption capacity Qmax was found to be 45.45 mgg-1. Thermodynamic adsorption processes showed the spontaneous, endothermic and randomness of the systems with free energy change less than zero, enthalpy change (∆H) of 66.43 kJmol-1and entropy change (∆S) of 145.37 Jmol-1K-1. Response Surface Methodology (RSM) showed that 0.55 g was the optimum dosage with 92.50 % removal of safranin dye concentration of 200 mgL-1 at pH 10.

Ficus-mediated green synthesis of manganese oxide nanoparticles for adsorptive removal of malachite green from surface water

The extract of ficus leaves was used to prepare manganese (IV) oxide nanoparticles (MnO2 NPs) for the first time. Several different analytical techniques were used to characterize the prepared MnO2 NPs. MnO2 has spherical crystals that are ~ 7 nm on average in size and have 149.68 m2/g of surface area and 0.91 cm3/g of total pore volume. Malachite green (MG) dye was then taken out of the water by adsorption using MnO2 NPs. Optimization of various adsorption parameters resulted in 188.68–277.78 mg/g maximum adsorption capacities at 298–328 K tested temperatures and 99.6% removal of 50 mg/L MG within 90 min using MnO2 dose of 0.01 g at pH 10 and 298 K. The results were tested using pseudo-first order, pseudo-second order, intraparticle diffusion, Elovich, and Liquid film kinetic models as well as Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models. The most likely models to describe the adsorption process at 298 K are pseudo-second-order kinetics (R2 = 0.997) with a rate constant of 4 × 10−4 g/(mg.min) and Langmuir isotherm (R2 = 0.973). Additionally, the positive values of enthalpy change (3.91–67.81 kJ/mol) and the negative values of Gibb’s free energy (− 3.38 to − 19.7 kJ/mol) indicate that the process is endothermic, spontaneous, and thermodynamically feasible. MnO2 NPs sustained their adsorption efficiency at 90.4% after 5 sorption cycles. MnO2 appears to be more selective for MG in studies examining the adsorption of various cationic dyes. Lately, the biosynthesized MnO2 NPs can be utilized to remove MG from aqueous solutions effectively.