Equilibrium Studies Research Articles

Study of phase equilibrium of refractory high-entropy alloys using the atomic size difference concept for turbine blade applications

Abstract In the pursuit of advancing turbine blade materials, refractory high-entropy alloys (RHEAs) have emerged as promising candidates, offering superior performance at elevated temperatures compared to conventional superalloys. With the plateauing of melting temperatures in Ni-based superalloys, the demand for innovative material systems capable of substantial performance enhancements in turbines has increased. The expansive compositional space of high-entropy alloys (HEAs) presents a rich yet underexplored realm, particularly concerning the intricate phase equilibria pivotal for alloy stability at high temperatures. This research purpose is to elucidate the phase formation dynamics within the W–Re–Ni–Co–Mo HEA system across varying atomic percentages of each constituent element. Employing two-dimensional mapping methodology for correlating atomic size difference and enthalpy mix parameters, enabling the differentiation between intermetallic (IM) phase and single-phase formations in the non-equimolar W–Re–Ni–Co–Mo system across numerous atomic percentages of each element. Major findings indicate distinct phase formations based on elemental compositions, with elevated nickel and rhenium percentages favouring single-phase solid solution (SPSS) structures, while diminished concentrations yield alternative configurations such as (IM + SPSS). Similarly, variations in tungsten and molybdenum concentrations influence phase stability. The ability to assess phases for diverse atomic percentages of elements in the W–Re–Ni–Co–Mo system will facilitate to analyse HEA systems for high-temperature turbine blades.

Study of quaternary liquid-liquid equilibria for systems (water/ methanol/ cyclohexanol+ toluene): Experimental and modelling

The experimental liquid-liquid equilibrium (LLE) data for the extraction of methanol from aqueous solution using mixed solvents (toluene + cyclohexanol) at 291.15 K and atmospheric pressure at the ratios (0, 0.25, 0.4, 0.6, 0.8, 1) was studied. The values of the solvent ratio 0 and 1 led us to study the liquid-liquid equilibrium of the ternary systems (water/methanol/cyclohexanol) and (water/methanol/toluene). The compositions of the coexisting phases were determined by the cloud point method. The tie line data for ternary and quaternary systems were correlated by NRTL model. The Othmer-Tobias and Hand correlations were also tested, to verify the reliability of the experimental tie lines data. The separation factor and the distribution coefficient were calculated from the experimental data to evaluate the effect of using mixed solvents. It was found that the ratio M = 0.4 is the best suited for the liquid-liquid extraction of methanol from water.

Microwave-Assisted Hydrothermal Synthesis of Zinc-tin Based Nanoflower for the Adsorptive Removal of Cadmium from Synthetic Wastewater

The present study utilized zinc-tin nanoflowers (ZT-NFs) in a batch adsorption treatment process to effectively remove cadmium from synthetic wastewater. The batch adsorption strategy was optimized using the univariate approach to enhance the efficiency of the adsorption process. The dominant parameters examined in the optimization experiments were pH/volume of buffer solution, nanoflower amount, and sample agitation type/period. After determining the optimal batch adsorption conditions, equilibrium studies were performed by adding cadmium to synthetic wastewater at concentrations in the range of 1.0 – 40 mg/L. The quantification accuracy for cadmium was improved by developing the calibration plot with spiked sample matrix. The equilibrium data were subjected to mathematical modelling utilizing the Langmuir adsorption isotherm model. The calculated isotherm constants indicated a well-fitted isotherm model to the experimental data. The reported ZT-NFs-based adsorptive removal strategy was effectively employed to remove cadmium from synthetic wastewater.

Adsorption of ciprofloxacin and ofloxacin onto green multi-walled carbon nanotubes in single and multi-component systems: Equilibrium study and machine learning modeling

The existence of residual concentrations of pharmaceutical substances in wastewater may impact the local ecosystem and human health, thus, it is required to mitigate the occurrence of these pollutants in effluents. This study performed the equilibrium adsorption in single and multi-component systems for two drugs (ciprofloxacin-CIP and ofloxacin-OFL) onto multi-walled carbon nanotubes, which were functionalized using a green route. Adsorption analyses were performed in batch aqueous systems in single- and multi-component mixtures at 25, 35, and 50 °C. Moreover, multi-component interaction was evaluated in equimolar (1:1) and non-equimolar (1:3 or 3:1) binaries of CIP with OFL. The results indicated that, for all systems evaluated, temperature did not majority influence the adsorption process. Even so, the adsorbed amount of antibiotics was slightly higher at the highest temperature (single-component systems: 0.433 mmol CIP. g−1 and 0.457 mmol OFL. g−1; and multi-component system: 0.958 mmol. CIP.g−1 and 0.872 mmol. OFL.g−1), indicating an endothermic process. The adjustment of the isothermal models indicated that the Sips and the Langmuir-Freundlich models were those that best fit the isotherms for the studied single-component and multi-component systems, respectively. Finally, artificial intelligence techniques were employed as an alternative to adjust the experimental data and revealed greater accuracy in calculating the observed results than traditional equilibrium models.

Sequestration of divalent heavy metal ions from aqueous environment by adsorption using biomass-bentonite composites as potential adsorbent: Equilibrium and kinetic studies

Hybrid clay adsorbents have been investigated in recent studies as cheap and effective adsorbents for eliminating micropollutants, such as heavy metal ions from aqueous solution. Here, we modified bentonite (BEN) with palm kernel shell and groundnut shell by calcination to obtain palm kernel shell-modified bentonite (BPKS) and groundnut shell-modified bentonite (BGS). We studied the batch equilibrium adsorption of Pb2+, Cd2+ and Ni2+ ions under the influence of dosage, solution pH, contact time and concentration. Under these conditions, we found that the modified adsorbents (BGS and BPKS) had a higher equilibrium adsorption (qe) for the metal ions than unmodified BEN. BEN exhibited Langmuir adsorption capacities (Qo) of 32.47, 14.04 and 14.16 mg/g for Pb2+, Cd2+ and Ni2+, respectively. BGS and BPKS had Qo values of 29.15, 14.27, 16.61 and 31.75, 17.67, 15.625 mg/g for Pb2+, Cd2+, Ni2+, respectively. Investigations revealed that the rate of adsorption on the three adsorbents is best described by a pseudo-second-order kinetic model, with R2 values ≥ 0.9; the intra-particle diffusion model establishes a surface interaction mechanism involving the exchange of electrons between the surfaces of the adsorbents and the adsorbate. Scanning electron microscopy results suggest porous and heterogeneous adsorbent surfaces, indicating a physio-sorption phenomenon. The modifications increased the surface area of BEN from 78.435 to 194.850 and 140.650 m2/g in BGS and BPKS, respectively, using BET surface area analysis. However, the average pore width of BEN reduces from 3.8 to 3.3 nm in both BGS and BPKS. Also, the modification enhanced the cation exchange capacity in BPKS only. The findings from this study offered invaluable insights into how biomass can enhance the physicochemical properties of BEN, as needed for practical environmental application and/or optimization, during the removal of Pb2+, Cd2+ and Ni2+ ions from aqueous media.

Removal of Humic Acid from Water by Adsorption Using Chitosan and Metal Organic Framework ZIF 8 Loaded Chitosan Adsorbents

Water is the most necessary need for life on the earth. There are a lot of organic pollutants in water. One of the organic pollutants is natural organic substances. Humic acid, a natural organic substance, turns into very harmful substances along with other pollutants. In this study, the humic acid removal from aqueous solution by adsorption using chitosan and chitosan/ZIF 8 composite spheres was examined. Chitosan spheres cross-linked with epichlorohydrin (ECH) and composite spheres consisting of metal organic framework ZIF8 and chitosan were prepared as adsorbents. Equilibrium, kinetic, and thermodynamic studies were investigated for humic acid adsorption by pristine chitosan-ECH and composite chitosan/ZIF 8 adsorbents. Chemical adsorption was found to be compatible with the Freundlich isotherm model and the pseudo-first-order kinetic model for pure chitosan adsorbents. Studies were carried out using chitosan/ZIF8 composite adsorbent, and the most suitable models for chemical adsorption were determined as Langmuir isotherm and pseudo-second order kinetic model. The response surface method was applied with the design expert program to determine the optimum experimental conditions. The adsorption tests were carried out using chitosan-ECH, ZIF 8 and chitosan/ZIF 8 adsorbents for specified optimum conditions, and the humic acid removal was determined as 95.1%, 98.3%, and 97.3%, respectively. In addition, desorption was performed using chitosan-ECH and chitosan/ZIF 8 spheres, and the desorption efficiency was found to be 20.9% and 82.5%, respectively. It has been observed that the developed adsorbents have potential in removing humic acid from water.

By-product Eucalyptus leaves valorization in the basic dye adsorption: kinetic equilibrium and thermodynamic study

Abstract Algerian Eucalyptus Leaves (AEL), a natural biodegradable adsorbent abundantly available, was used for the removal of methylene blue (MB) dye. The AEL properties for the removal of MB were investigated under different conditions by varying the AEL amount, MB concentration, pH of the solution and the reaction temperature. Scanning electron microscopy (SEM) and infrared spectroscopy (FTIR) techniques have been used to characterize AEL biosorbent. Experimental results showed that the adsorption of MB dye at the concentration of 50 mg L−1 reached to 91 % at pH 10 with a stirring speed of 200 rpm and after 180 min of reaction time. The experimental data were analyzed using the linear forms of different kinetic models (pseudo-first order kinetic model, pseudo-second order kinetic model, and intra-particle diffusion models). The results demonstrated that the adsorption kinetics of MB was consistent with the pseudo-second order model with R 2 value of 0.9969. The isotherm models Langmuir, Freundlich, Dubinin, Elovich, Brunaut Emmet Teller and Temkin models were also investigated to describe the adsorption equilibrium. The results show that the AEL adsorption is in accordance with Temkin isotherm. The thermodynamic study revealed that the adsorption is spontaneous and exothermic. Therefore, as a cheap green adsorbent with high MB adsorption performance, AEL is expected to become one of the best candidate materials for future industrial wastewater treatment.

Comprehensive Studies of Adsorption Equilibrium and Kinetics for Selected Aromatic Organic Compounds on Activated Carbon.

This work presents a comprehensive analysis of the adsorption of selected aromatic organic compounds on activated carbons. Both the equilibrium and kinetics of adsorption were studied using UV-Vis spectrophotometry. The influence of a number of factors: pH, contact time, presence of an accompanying substance, adsorbate concentration, as well as the mass and size of adsorbent grains, on the adsorption process from aqueous solutions was investigated. Phenol, 2-nitrophenol, 3-nitrophenol, 4-nitrophenol and methylene blue (as an accompanying substance) were selected as adsorbates. GAC 1240W and RIAA activated carbons were used as adsorbents. The equilibrium data were analyzed using the generalized Langmuir isotherm equation (R2 = 0.912-0.996). Adsorption rate data were fitted using a multi-exponential kinetic equation (1 - R2 = (1.0 × 10-6)-(8.2 × 10-4)). As an additional parameter, the half-time was also used to present the influence of selected factors on the adsorption kinetics. An increase in the amount of adsorption was demonstrated with increasing contact time as well as with decreasing solution pH and adsorbent grain size. For selected systems, an increase in the adsorption rate was observed with increasing adsorbate concentration, adsorbent mass and at lower pH values. In some cases, the presence of an accompanying substance also resulted in an increase in adsorption kinetics. In the tested experimental systems, optimal conditions for adsorption were established (T = 298 K, pH = 2, contact time: 7 days, grain diameter: >0.5 mm and the ratio of the mass of the adsorbent to the volume of the adsorbate solution: 1 g/L). Additionally, the acid-base properties (potentiometric titration), morphology (SEM) and structure (TEM) of the used adsorbents were also examined.

Preparation of styrene-based imprinted polymer for the adsorption of hazardous bromocresol green dye: Equilibrium, kinetics and thermodynamics study

In this study, styrene was used as a functional monomer for the production of molecularly imprinted polymer (MIP) via free radical polymerization method, using bromocresol green dye (BCG) as template. A non-imprinted polymer (NIP), that excluded the template, was also synthesized. Both polymers were applied for the removal of BCG from aqueous medium. The synthesized polymers were characterized with Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray powder diffraction spectroscopic techniques. The effect of operating variables, such as pH, contact time, initial dye concentration and process temperature, on the efficiencies of the polymers in removing the dye were evaluated. Equilibrium time of BCG adsorption onto the MIP was reached within 40 min, with adsorption capacity of 49.68 mg g-1 . The adsorption process followed the pseudo-second-order kinetic and Freundlich isotherm models, while chemisorption mechanism was predicted. The adsorption process was spontaneous and exothermic in nature, with DH values of -140.03 and -25.01 kJ/mol-1 recorded for BCG removal by MIP and NIP, respectively. The styrene-based MIP showed good mechanical stability, and retained up to about 99% of its adsorption capacity after six sequential cycles of regeneration. Comparatively, the MIP (99.81mg g-1 ) performed considerably better than its NIP (59.00 mg g-1 ) analogue in the removal of BCG from aqueous medium, thus affirming the potentials of the molecular imprinting technique in the production of efficient adsorbents for adsorption of toxic dyes from industrial effluents.

Effect of the type of ion-exchange resin on Mn<sup>2+</sup> adsorption in the presence of competing cations

Present in soils, ground and surface waters, manganese is among the most common metals in Earth crust. It is also an essential trace element to the functioning of several enzymes in the human body. However, exposure to high manganese concentrations can also be harmful to humans with psychiatric and motor effects and therefore, manganese concentrations in drinking water and also industrial effluents are regulated. In the current work, the adsorption of Ca<sup>2+</sup>, Mg<sup>2+</sup> and Mn<sup>2+</sup> on three different ion-exchange resins: (i) aminophosphonic acid - chelating (Purolite S950), (ii) polyacrylic weak acid cation (Purolite C104E) and (iii) polystyrene strong acid cation (Purolite C100) was investigated. The results revealed that Purolite S950 had the highest Mn2+ uptake (37.9 mg/mL-resin or 0.69 mmol/mL-resin) as compared to Ca<sup>2+</sup> (3.2 mg/mL-resin or 0.08 mmol/mL-resin) and Mg<sup>2+</sup> (~0 mg/mL-resin) and was selected for further kinetics and equilibrium studies. The results indicated Purolite S950 as particularly suited to be applied in the treatment of neutral mine waters with high Mg/Mn ratios. Additionally, Purolite S950 showed a small affinity for Ca<sup>2+</sup> and therefore an efficient Mn<sup>2+</sup> removal will depend on the Ca/Mn ratio of the mine water under treatment. According to the kinetic analysis, manganese sorption on Purolite S950 was described by the pseudo-second order model (r<sup>2</sup> > 0.98) with an activation energy of 10.40 kJ/mol and thus pore-difussion was the rate controlling step of the process. In terms of equilibrium studies, manganese sorption on Purolite S950 followed the Langmuir model with maximum loadings of up to 41.5 mg/mL-resin. The thermodynamic modelling indicated an exothermic process (-85.0 kJ/mol, as standard enthalpy) with a standard entropy of -274 J/mol.K, which was ascribed to the release of two adsorbed H<sup>+</sup> ions for each Mn<sup>2+</sup> ion taken up from solution

Purified residues from the production of biogenic silica as resources for the remediation of oilfield produced water: A strategy for phenol removal

The escalating fuel demand generates significant volumes of oilfield-produced water containing complex environmental pollutants such as phenol. This study proposes a purification method for converting activated carbon (CAM), obtained at zero cost as a by-product of biogenic silica production, into an effective adsorbent. The activated carbon was characterized extensively for its morphological, structural, and chemical properties, revealing a substantial surface area exceeding 1000 m2/g. The adsorption process for phenol removal was investigated through kinetics, isotherms, and thermodynamic analyses. Kinetic data analysis favored the PSO models within 150 min, while equilibrium studies showed the best fit for the Sips and Liu models. CAM achieved an adsorption capacity of 23.9 mg g−1 for phenol removal at pH 6, the typical pH of produced water. The adsorption process was found to be exothermic and spontaneous. The produced adsorbent demonstrated high recyclability, with up to 15 reuse cycles achievable through regeneration via thermal desorption at 180 °C. Furthermore, CAM removed 73 % of total organic carbon from real produced water within 150 min. Thus, using activated carbon intrinsically carbonized during silica production is an economically viable and attractive solution for treating phenol-contaminated oilfield-produced water.

Adsorption of Coomassie Brilliant Blue on a Novel Eco‐Friendly Nanogel from Simulated Water: Equilibrium, Kinetic, and Thermodynamic Studies

AbstractHerein a novel gum acacia‐alginate nanogel (GAA) was synthesized via ultrasound‐assisted crosslinking by DPPH and applied for the removal of coomassie brilliant blue (CBB) dye. The fabrication of GAA and its interaction with CBB was specified via FTIR, XRD, SEM, and TEM techniques. The process parameters at which maximum adsorption efficiency, qe (80.12 mg/g), and % efficiency >94 % were achieved include dosage (0.8 g/L), time (80 min), initial dye concentration (20 mg/L), and pH (6). Ultrasound‐assisted uptake was greater than stirring‐assisted due to acoustic cavitation′s hydrodynamic and thermal processes. Pseudo‐second‐order model described the adsorption kinetics and the diffusion mechanism suggested that the rate‐determining step was controlled by both the intraparticle diffusion and the liquid film models. Isotherms showed an excellent fit to the Freundlich model based on higher R2 (0.998) and lower standard error of estimate values (SEE=0.367). The −ΔG° values (−8.152, −8.292, −8.433, −8.586 kJ/mol) indicated that the adsorption process was feasible and spontaneous. The removal of CBB ensued via hydrogen bonding, electrostatic, π‐π, and n‐π interactions. The maximum adsorption capacity of 182.096 mg/g, eco‐friendly characteristics along with regeneration competence depicted that GAA could be effective for scavenging CBB from wastewater.

Acid-activated corn silk as a promising phytosorbent for uptake of Malachite green and Cd (II) ion from simulated wastewater: equilibrium, kinetic and thermodynamic studies

Malachite green (MG) dye and cadmium metal ion are toxic pollutants that should be removed from aqueous environment. The recent study aimed to examine the adsorption behavior of MG dye and Cd (II) from wastewater onto low-cost adsorbent prepared by activating corn silk with nitric acid (ACS) and characterized by SEM, FTIR, XRD, BET and TGA. The optimum MG and Cd (II) adsorption was observed at pH 7 and pH 9 and maximum uptake of both pollutants was at 0.5 g dosage, 60 mins contact time and 20 mg/L initial concentration. The retention of dye and metal ion by the studied adsorbent was best fit to Langmuir isotherm and Pseudo-second order kinetics. The maximum monolayer coverage capacity of ACS for MG dye and Cd (II) ion was 18.38 mg/g and 25.53 mg/g, respectively. Thermodynamic studies predicted a spontaneous reaction with exothermic process for MG dye whereas an endothermic and spontaneous process was confirmed for Cd ion based on estimated parameters. The adsorption mechanism of MG dye and Cd (II) uptake was by combination of electrostatic interaction, pore diffusion, ion exchange, pie-pie attraction, hydrogen bonding, and complexation. The adsorbed pollutants were effectively desorbed with significant regeneration efficiency after successive five cycles that proved the potential of low-cost biosorbent for selective sequestration of cationic dye and divalent metal ion from effluents.

The production of a novel adsorbent from forest waste (Platanus orientalis L.) for dye adsorption: Adsorption process optimization and experimental design

In the study, a novel activated carbon material was produced using forest waste commonly found in nature. The activation was completed by modifying the surface of the material with H3PO4. Using this adsorbent material, we investigated the adsorption of the hazardous dyestuff, methylene blue, from the water environment. The adsorbent was characterized using BET, SEM, and FT-IR analyses. The characterization processes revealed that the adsorbent has a wealth of functional groups and many cavities and protrusions on its surface. Moreover, according to the BET analysis result, it was observed that it is an adsorbent with a high surface area (876.01 m2 g−1). Kinetic, equilibrium and thermodynamic studies have been conducted to fully understand the nature of methylene blue adsorption. The pseudo-second order kinetic model best represents the adsorption process data, and the Langmuir isotherm aligns with the equilibrium data. According to the Langmuir isotherm data, the maximum adsorption capacity (qmax) was determined to be 198.01 mg g−1. The thermodynamic results showed that the process of adsorption of methylene blue on various surfaces is spontaneous and occurs via physisorption. Additionally, in addition, the effects of the parameters (adsorbent dose, time, and concentration) determined for the methylene blue adsorption process were optimized using the surface response method. Activated carbon from plane tree fruits (Platanus orientalis L.) has the potential to be a novel adsorbent due to its unique surface morphology and strong adsorption capabilities.

Equilibrium and kinetic modeling of Cr(VI) removal by novel tolerant bacteria species along with zero-valent iron nanoparticles

This work describes the study of the removal of a refractory contaminant, i.e., Hexavalent chromium (Cr(VI)) from aqueous systems by a novel adsorbent comprising Cr(VI) tolerant bacteria and zero valent iron nanoparticle (nZVI). A gram-positive, rod-shaped bacteria used in the study were isolated from wastewater (WW) received from the effluent of leather industries. The adsorbents were prepared with bacteria, nZVI alone, and a combination of both. The adsorbent comprising both elements was found to remove Cr(VI) with a higher percentage (93%) and higher capacities (0.58 mg/g) as compared to adsorbent with bacteria (Cr(VI) removal = 63%, qe = 0.163 mg/g) or nanoparticles (Cr(VI) removal = 80%, qe = 0.45 mg/g) alone. The adsorbent worked best at neutral pH, and the removal became saturated after 90 min of incubation. Equilibrium studies with isotherm modeling suggested that the adsorption process follows sips isotherm (R2 = 0.9955), which is expected to bean intra-particle diffusion process before the actual adsorption. Process kinetics was modeled with pseudo-first order, pseudo-second order, and Vermeulen model. The diffusion coefficient determined by fitting the kinetic data to Vermeulen model was found to be 0.0000314 cm2/s. The adsorbent can be tested further for continuous flow processes to find more insights about the usage on a large scale.

Functionalised Seed Pods for the Sorption of Crystal Violet from Aqueous Solution: Kinetics and Equilibrium Studies

Functionalised Seed Pods for the Sorption of Crystal Violet from Aqueous Solution: Kinetics and Equilibrium Studies

Adsorption of cyanide from Cassava wastewater using activated carbons derived from Raphia hookeri kernels: a comparison of in-situ and ex-situ activation

The rise in cyanide concentration in groundwater in many developing countries is linked to the indiscriminate discharge of cyanide-bearing wastewater from cassava processing industries. This research synthesized a super-active activated carbon (AC) from a novel biomass precursor, Raphia hookeri kernel, functionalized with phosphoric acid via in-situ and ex-situ methods. Morphological and functional characterizations were performed, and the influence of some key process variables on cyanide adsorption was also investigated for the two derived ACs to study the impact of the activation method used. The optimal conditions for cyanide adsorption for the in-situ and ex-situ–derived ACs were identified as pH 8, AC dose of 0.15 g, temperature of 40 °C, and initial cyanide concentration of 100 mgL−1 at different equilibrium times of 100 min and 120 min, respectively. The kinetic studies revealed that the pseudo-second-order kinetic model fitted the adsorption data better for the two ACs based on the high correlation coefficients (r2), suggesting that the adsorption process is chemisorption. The equilibrium studies showed that the in-situ-derived AC followed the Langmuir isotherm with a maximum adsorption capacity (qm) of 93.821 mgg−1 indicating monolayer adsorption for the in-situ-derived AC. The ex-situ-derived AC, however, followed the Sips isotherm with a maximum adsorption capacity (qm) of 79.381 mgg−1 indicating a heterogeneous surface for the ex-situ-derived AC. The ACs showed decreasing cyanide adsorption after five cycles but maintained significant adsorption capacity after desorption-adsorption cycles.

Harnessing microwave energy to transform Nephelium lappaceum L. peel into activated carbon for chloramphenicol eradication in aqueous solutions

Emerging contaminants (EC) like chloramphenicol in wastewater are highly related to human, livestock, and aquaculture therapeutic activities. High levels of chloramphenicol in water may cause toxic effects on an aquatic environment, humans, and animals. The removal of chloramphenicol in wastewater was the main objective of this study. This study explores the use of microwave irradiation in the production of Rambutan peel-based activated carbon (RPAC) at a heating power of 700 W for 15 min under carbon dioxide, CO2 gas flow. RPAC had a BET surface area of 583.44 m2/g, mesopores surface area of 469.87 m2/g, total pore volume of 0.27 cm3/g, and average pore diameter of 2.31 nm. The equilibrium study shows that the concentration of Cp adsorbed by RPAC increased as the initial concentration increased from 4.93 mg/g to 25.10 mg/g. Isotherm adsorption determined that Langmuir was the preferred model since it has the lowest RSME and highest R2 of 3.34 and 0.9994, respectively. It was observed from kinetic studies that the adsorption system relies on the pseudo-second order. According to thermodynamic studies, the enthalpy change, △H° and Gibbs free energy, △G° obtained indicating that the adsorption process occurs in an exothermic and spontaneous state.

Synergistic removal of toxic anionic reactive red dye Me4BL (RRME4BL) from aqueous media using chemically synthesised nano-adsorbents (ZnO, CuO, NiO and CoO); equilibrium, kinetics and thermodynamic studies

ABSTRACT This study explores the efficient removal of the synthetic anionic dye-reactive red Me4BL (RRMe4BL) from an aqueous medium which is a significant contributor to environmental pollution. The present study investigates the synthesis of zinc oxide, nickel oxide, cobalt oxide and copper oxide nano adsorbents (ZnO (II), NiO (II), CoO (II), CuO (II)) through the co-precipitation method and their effectiveness in eliminating the reactive red dye Me4BL(RRMe4BL). Maximum adsorption capacities were achieved at pH 2 for ZnO (96.1 mg/g), NiO (86.9 mg/g), CoO (93.4 mg/g) and at pH 6 for CuO (76.3 mg/g) under a 0.05 g/50 mL nano-adsorbent dose, 50 mg/L dye initial concentration and 25°C T and 90 min of contact time. The fitness of the pseudo-2nd-order model explained the kinetics, while Langmuir and Temkin adsorption isotherm highlighted the efficiency of the dye adsorption. Thermodynamic studies revealed the spontaneous and exothermic nature of adsorption. The influence of electrolytes, surfactants and desorption was also analysed. Characterisation of the nanoparticles was done through SEM, XRD and FTIR which revealed the morphology and functional groups of nano-adsorbents. The adsorption method used for eliminating this anionic red dye shows several benefits, including affordability, simplicity of use and the presence of intelligent adsorbents for environment-friendly removal of industrial dyes from wastewater.

Adsorptive uptake of thymol blue from aqueous medium using calcined snail shells: equilibrium, kinetic, thermodynamic, neuro-fuzzy and DFT studies

ABSTRACTS The spontaneous discharge of pollutants or toxicants into the ecosystem as a result of various anthropogenic activities is alarming, this necessitates a drastic cheap, and eco-friendly clean-up approach. Out of all the methods, adsorption has proven to be the most effective. The batch adsorptive removal of Thymol Blue (TB) dye from aqueous solutions is examined in this study utilizing calcined snail shells (CalSS). With the aid of SEM, EDS, XRD, and FTIR, the synthesized adsorbent was examined for different physicochemical characteristics. A machine learning model namely Adaptive Neuro-Fuzzy Inference System (ANFIS) was developed to assess the TB adsorption process while taking into account the important adsorption parameters contact time, temperature, pH, adsorbent dosage, then initial adsorbate concentration. Adsorbent pHpzc was also evaluated. EDX and FTIR confirm the formation of CaO with sharp peaks at 547 cm−1 and C–O and O–H are present. SEM and XRD show an irregularly shaped highly crystalline adsorbent material having a typical particle size of 65 ± 2.81 nm and lattice parameter value of 8.611617 Å. The pHpzc value is 11.04, indicating basic surface characteristics. The pH of 3.0, an adsorbent dose of 10 mg and the highest achievable adsorption efficiency were measured to be 98.75% at 20 °C. The findings from the study fit nicely onto Brouser Sotolongo with q BS = 259.4887 mg/g and R 2 = 0.9888. The pseudosecond order model (PSOM) recorded the least error value of 0.3336 and R 2 = 0.9952. This indicates chemisorption and multilayer adsorption processes. The thermodynamic parameters ΔH° and ΔG° demonstrate the exothermic and spontaneous nature of the adsorption process. The ANFIS model for the TB sequestration was evaluated using relevant statistical metrics, giving Root Mean Square Error (RMSE) value of 1.4644, Mean Absolute Deviation (MAD) value of 0.576, Mean Absolute Error (MAE) value of 1.2974 and Mean Absolute Percentage Error (MAPE) value of 1.5141. This outcome revealed that the ANFIS model and experimental findings are in good agreement. The efficacy of calcined snail shell in removing Thymol Blue dye from aqueous solution was also examined using in-silico technique which was in accordance to the value of the calculated descriptors obtained from the adsorbent as well as the calculated binding affinity. The elimination of TB-polluted wastewater using calcined snail shells is demonstrated in this study to be a successful and environmentally benign process.