Hill Isotherm Research Articles

Optimized design of quaternary amino-functionalized chitosan fibers for ultra-high diclofenac adsorption from wastewater

The extraction of non-steroidal anti-inflammatory drugs (NSAIDs) from water bodies is imperative due to the potential harm to humans and the ecosystem caused by NSAID-contaminated water. Quaternary amino-functionalized epichlorohydrin cross-linked chitosan fibers (QECFs), an economical and eco-friendly adsorbent, were successfully prepared using a simple and gentle method for efficient diclofenac (DCF) adsorption. Additionally, the optimized factors for the preparation of QECFs included epichlorohydrin concentration, pH, temperature, and (3-chloro-2-hydroxypropyl) trimethylammonium chloride (CHTAC) concentration. QECFs demonstrated excellent adsorption performance for DCF across a broad pH range of 7–12. The calculated maximum adsorption capacity and the amount of adsorbed DCF per adsorption site were determined to be 987.5 ± 20.1 mg/g and 1.2 ± 0.2, respectively, according to the D-R and Hill isotherm models, at pH 7 within 180 min. This performance surpassed that of previously reported adsorbents. The regeneration of QECFs could be achieved using a 0.5 mol/L NaOH solution within 90 min, with QECFs retaining their original fiber form and experiencing only a 9.18% reduction in adsorption capacity after 5 cycles. The Fourier transform infrared spectrometer and X-ray photoelectron spectroscopy were used to study the characterization of QECFs, the preparation mechanism of QECFs, and the adsorption mechanism of DCF by QECFs. Quaternary ammonium groups (R4N+) were well developed in QECFs through the reaction between amino/hydroxyl groups on chitosan and CHTAC, and approximately 0.98 CHTAC molecule with 0.98 R4N+ group were immobilized on each chitosan monomer. Additionally, these R4N+ on QECFs played a crucial role in the removal of DCF.

Development of a Manganese Dioxide-Decorated Activated Carbon Nano-sorbent via Co-precipitation method for efficient lithium ion adsorption from aqueous solutions

ABSTRACT Recently, the utilization of lithium has increased significantly, particularly in high-tech industries such as nuclear, aerospace, automotive, battery, military, glass and ceramic, and lubricants. However, lithium recovery methods from brines present certain drawbacks, making lithium exploitation a global challenge. A comparative analysis of lithium recovery methods from brine solutions indicates that the adsorption method holds promising potential for separating lithium from low-concentration solutions. Despite this, the quest for an effective and efficient adsorbent for lithium-ion adsorption remains a challenge, necessitating the development of an adsorbent, using readily available materials. In this study, carbon-active underwent chemical modification. Notably, the co-precipitation method was employed for the first time to create a composite adsorbent decorated with manganese dioxide (MnO2). Various analyses, including XRD, SEM-EDS, FTIR, and BET, were conducted to elucidate the structural, morphological, physical, and chemical properties of the adsorbent. This synthesized adsorbent was applied to the adsorption of lithium from an aqueous sample. Exploration of adsorption parameters affecting capacity led to the identification of optimal conditions: 14-hour duration, an adsorbent dosage of 0.02 g, and an ambient temperature of 25°C, in a lithium solution with a concentration of 60.4 ppm. Under these conditions, the maximum adsorption capacity of the adsorbent was determined to be 30.5 mg/g. Based on experimental results, kinetic and adsorption isotherm models were investigated. The Pseudo-quadratic kinetic model, with an R2 value of 0.999, emerged as the most suitable for describing the adsorbent’s behavior. The Hill isotherm model with R2 = 0.9634 is the most appropriate isotherm model to describe the adsorbent behavior. Additionally, the selectivity of the adsorbent in the presence of other ions was investigated. The adsorbent’s reusability was examined, and after two recycling periods, the adsorbent maintained an efficiency of up to 88%, demonstrating its stability. The CAC-MnO2-P composite adsorbent shows technical and economic promise for industrial use in lithium-ion recovery processes.

A novel magnetic Ti-MOF/chitosan composite for efficient adsorption of Pb(II) from aqueous solutions: Synthesis and investigation

In this investigation, a composite material comprising Ti-MOF and chitosan, denoted as BD-MOF(Ti)@CS/Fe3O4, was successfully designed for the efficient adsorption of Pb(II) from aqueous solutions. A comprehensive array of characterization techniques, including SEM, XRD, BET, FT-IR, and XPS, were meticulously employed to scrutinize the structural attributes and morphological features of the Pb(II) adsorbent. Notably, the material exhibits adaptability to a broad pH range, with adsorption efficiency reaching 99 % between pH 3 and 6. Kinetic studies reveal that the adsorption process of Pb(II) by BD-MOF(Ti)@CS/Fe3O4 adheres closely to a pseudo-second-order kinetic model. Impressively, within a short duration of 40 min, the adsorption efficiency can reach 85 %. Furthermore, the adsorption isotherm aligns with the Hill isotherm model, signifying cooperative adsorption. This observation underscores the synergistic interplay among the functional groups on the surface of BD-MOF(Ti)@CS/Fe3O4 in capturing Pb(II). As per the Hill model, the theoretical maximum capacity was an impressive 944.9 mg/g. Thermodynamic assessments suggested that the adsorption process was spontaneous, entropy increasing and exothermic. Even in the presence of various interfering ions, BD-MOF(Ti)@CS/Fe3O4 exhibited robust adsorption performance, thereby affirming its utility in complex environments. Moreover, the material demonstrates noteworthy reusability, sustaining effective Pb(II) removal across five consecutive cycles in aqueous solutions.

Bacterial cellulose microfiber reinforced hollow chitosan beads decorated with cross-linked melamine plates for the removal of the Congo red

In this epoch, the disposal of multipollutant wastewater inevitably compromises life on Earth. In this study, the inclusion of Bacterial cellulose microfilaments reinforced chitosan adorned with melamine 2D plates creates a unique 3D bead structure for anionic dye removal. The establishment of an imine network between melamine and chitosan, along with the quantity of inter- and intra‑hydrogen bonds, boosts the specific surface area to 106.68 m2.g−1. Removal efficiency and in-depth comprehension of synthesized adsorbent characteristics were assessed using batch adsorption experiments and characterization methods. Additionally, pH, adsorbent quantity, time, beginning concentration of solution, and temperature were analyzed and optimized as adsorption essential factors. Owing to the profusion of hydroxyl, amine, imine functional groups and aromatic rings, the synthesized adsorbent intimated an astonishing maximum adsorption capacity of 3168 mg.g−1 in Congo red dye removal at pH 5.5. Based on the kinetic evaluation, pseudo-second-order (R2 = 0.999), pseudo-first-order (R2 = 0.964), and Avrami (R2 = 0.986) models were well-fitted with the kinetic results among the seven investigated models. The isothermal study reveals that the adsorption mechanism predominantly follows the Redlich-Peterson (R2 = 0.996), Koble-Carrigan, and Hill isotherm models (R2 = 0.994). The developed semi-natural sorbent suggests high adsorption capacity, which results from its exceptional structure, presenting promising implications for wastewater treatment.

Evaluation of synergistic adsorption approach for terbinafine removal by cotton shell powder immobilized zerovalent copper: Adsorption kinetics and DFT simulation

Cotton shell powder (CS), nano zerovalent copper (nZVC) and cotton shell powder immobilized zerovalent copper (ZVC@CS) were evaluated for their adsorption efficiencies towards terbinafine hydrochloride (TBH), an antifungal drug. The nZVC and ZVC@CS synthesized via one pot redox precipitation method were characterized by FTIR, XRD, BET, FESEM and TGA analysis. The TGA and AAS analysis confirmed the loading of nearly 10% of nZVC on cotton shell powder in ZVC@CS. The effect of operational parameters (pH, adsorbent dose, initial drug concentration, time, etc.) determining the extent of terbinafine hydrochloride adsorption on ZVC@CS were investigated to ascertain the optimal experimental conditions to achieve maximum adsorption efficiencies. To investigate the adsorption behavior of TBH on ZVC@CS, the experimental data were fitted for five different adsorption models viz. Langmuir, Freundlich, Temkin, Redlich-Peterson and Hill isotherms. The TBH adsorption data was best fit with Hill isotherm model indicating cooperative sorption of TBH molecules on ZVC@CS surface. Among the five kinetic equations namely the pseudo-first-order (PFO), the pseudo-second-order (PSO), Elovich model, the intraparticle diffusion model, and Boyd kinetic model used to estimate the adsorption mechanism, the PFO kinetic model give best fit with a good correlation for the physisorption of TBH on ZVC@CS composite. The mechanism of the adsorption process was observed to be complex, consisting of both surface adsorption and pore diffusion. However, the Boyd plot confirms external mass transport as the rate limiting step for the adsorption of TBH on ZVC@CS. The synergistic adsorption of TBH on ZVC@CS was hypothesized, and the idea was supported by structure optimization results from DFT studies. The ZVC@CS exhibits equilibrium TBH adsorption efficiency (qmax) of 285.3 mg.g−1, significantly higher than adsorbents used in literature for the TBH removal.It is suggested that ZVC@CS may serve as sustainable adsorbents for the removal of cationic contaminants from acidic medium.

Extensive sorption of Amoxicillin by highly efficient carbon-based adsorbent from palm kernel: Artificial neural network modeling

In the present study, a new sorbent was fabricated from Palm kernel (PK) by dry thermochemical activation with NaOH and characterized by FTIR, X-ray diffraction, FE-SEM and BET, which was used for the Amoxicillin (AMX) sorption from aqueous solution. The influence of effective parameters such as pH, reaction time, adsorbent dosage, AMX concentration and ionic strength on the sorption efficacy of AMX removal were evaluated. The main functional groups on the surface of the magnetic activated carbon of Palm Kernel (MA-PK) were C–C, C–O, CO and hydroxyl groups. The specific surface of char, activated carbon Palm Kernel (AC-PK) and MA-PK were 4.3, 1648.8 and 1852.4 m2/g, respectively. The highest sorption of AMX (400 mg/L) was obtained by using 1 g/L of sorbent at solution pH of 5 after 60 min contact time, which corresponding to 98.77%. Non-linear and linear models of isotherms and kinetics models were studied. The data fitted well with Hill isotherm (R2 = 0.987) and calculated maximum sorption capacity were 719.07 and 512.27 mg/g from Hill and Langmuir, respectively. A study of kinetics shows that the adsorption of AMX follows the Elovich model with R2 = 0.9998. Based on the artificial neural network (ANN) modeling, the MA-PK dosage and contact time showed the most important parameters in the removal of AMX with relative importance of 36.5 and 25.7%, respectively. Lastly, the fabricated MA-PK was successfully used to remove the AMX from hospital wastewater.

Eco-friendly CO2 adsorption by activated-nano-clay montmorillonite promoted with deep eutectic solvent

ABSTRACT In this work, an innovative and environmentally friendly adsorbent for CO2 capture is synthesized by Choline Chloride-Urea (ChCl: U) functionalization of the acid-activated montmorillonite (MMT) for the first time. The surface area enhancement was achieved by acid activation at 3 Molarity, which resulted in 7.1 and 10.9 times increase in the specific area and pore volume, respectively. In fact, the highest reported value of the surface area of montmorillonite has been achieved. The characterization was carried out by FTIR, BET, XRD, and SEM to ensure the qualification of the modified acid-activated and then impregnated with the solvent. The optimum condition for the input variable was 30 ºC, 9 bar, and 50% of the solvent to MMT, where the response was 252 mg/g. The evaluation of the heterogeneous and mono-multilayer adsorption indicated the experimental data well-fitted to the Hill isotherm model with n higher than 1, indicating the desirability of the adsorbent (n was also 1.59 for the Freundlich isotherm model). The Elovich kinetic model was observed to be in the best agreement with the experimental data. Eight cycles of adsorption-desorption results indicated an excellent reversible adsorbent with low-temperature regeneration (90ºC) is attained.

Copper ion removal from aqueous media using banana peel biochar/Fe3O4/branched polyethyleneimine

To address the severe pollution caused by heavy metals, adsorbents have attracted considerable attention based on the idea of energy conservation, emission reduction, and waste utilization. In this work, magnetic nanocomposites were employed as an adequate source for Cu2+ adsorption. Fe3O4 nanoparticles were modified using branched polyethyleneimine and biochar produced from banana peels. The magnetic nanocomposites (BPB/Fe3O4/BPEI) were prepared by chemical coprecipitation. The resulting adsorbents were characterized using SEM, TEM, EDS, XRD, and FTIR, and it was also indicated that BPB/Fe3O4/BPEI was successfully prepared by stepwise modification with BPB, Fe3O4, and branched polyethyleneimine. VSM result shows the BPB/Fe3O4/BPEI exhibit a paramagnetic behavior (21.22 emu/g). A mesoporous structure can be confirmed by BET analysis (BPB/Fe3O4/BPEI: 68.72 m2/g). The effects of contact time, pH, concentration of copper ions, and adsorbent dose on the efficiency of copper ion adsorption were investigated. The optimal adsorption efficiencies for BPB(81.99%), Fe3O4(20.18%), BPB/Fe3O4(82.15%), Fe3O4/BPEI(87.37%), and BPB/Fe3O4/BPEI(99.46%) were determined. Furthermore, D-R, Temkin, Freundlich, Langmuir, Redlich-Peterson, Toth, Sips, and Hill isotherm models, Weber-Morris intraparticle diffusion, and Elovich, PSO, PFO, and Boyd kinetic models were conducted to better understand the removal process. The BPB/Fe3O4/BPEI adsorbents fit the PSO kinetic model and the Sips isotherm model best. The maximum capacities for Cu2+ adsorption with BPB, Fe3O4, BPB/Fe3O4, Fe3O4/BPEI, and BPB/Fe3O4/BPEI are determined to be 15.14 mg/g, 2.75 mg/g, 24.65 mg/g, 32.66 mg/g, and 73.23 mg/g, respectively. Furthermore, the effect of other metal ions and the reusability of BPB/Fe3O4/BPEI were studied, indicating that BPB/Fe3O4/BPEI has good stability even in the presence of other influential heavy metal ions in solution and can be effectively reused for wastewater treatment.

Triethanolamine‐modified montmorillonite clay as a new adsorbent for CO2 capture: Characterization, adsorption, and RSM modeling

AbstractIn this study, CO2 adsorption capacity was investigated by modified montmorillonite with triethanolamine due to its mechanical and chemical stability. The effect of operational parameters on CO2 adsorption capacity including temperature, pressure, and percentage triethanolamine was studied in the range of 30–70°C and 1–9 bar and 10–30%wt., respectively. Isothermal, kinetic, and thermodynamic analyses were performed by conventional method under equilibrium conditions. According to the R2 values from fitting the experimental data on the isothermal models, the Hill isotherm model was proposed for the unmodified and modified montmorillonite adsorbent. The results showed that the Elovich kinetic model provides the best fit for CO2 adsorption data for montmorillonite and triethanolamine‐modified montmorillonite. In the study of thermodynamic models, the positive slope of the Ln (Kd) diagram against 1/T indicates the thermal conductivity of the surface adsorption process. Optimal operating parameters were determined to obtain the highest adsorption capacity using the Design Expert software. For montmorillonite, the adsorption capacity obtained 219.86 mg/g at a temperature of 40°C and pressure of 7 bar, and for modified montmorillonite with triethanolamine, the optimal conditions for the input variables were 40°C, 7 bar, and 18.36%wt., respectively, and the adsorption capacity obtained was 248.55 mg/g.

Adsorption behavior of carboxy- and amine-terminated magnetic beads for patulin: Batch experiments in aqueous solution and apple juice

Patulin (PAT) is a highly water soluble, heat resistant and toxic fungal metabolite mostly contaminating apple juice. Due to its serious health effects, its removal from foodstuffs is required to ensure food safety. In this study, carboxy- and amine-terminated iron oxide spheres (Fe3O4-COOH and Fe3O4-NH2) were investigated for their adsorbing capacity of PAT in both aqueous solution and apple juice, and evaluated for being an effective detoxifying agent for PAT. The physical and chemical properties of adsorbents were characterized by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) and Scanning Electron Microscopy (SEM). The maximum adsorption capacities Fe3O4-COOH and Fe3O4-NH2 for PAT obtained at 25 °C, pH 6 for 5 h were 0.206 mg/g and 0.104 mg/g, respectively. Best fitting adsorption isotherm and kinetics models of PAT adsorption process were Hill isotherm (Radj2 = 0.985) and pseudo-second kinetic models (Radj2 > 0.99) for carboxy groups and Langmuir isotherm (Radj2 = 0.974) and pseudo-second kinetic models (Radj2 > 0.99) for amine groups on the surface of adsorbents. These models with the experimental results confirmed the physical adsorption process, while thermodynamic analysis indicated that adsorption process was spontaneous and endothermic between PAT and both adsorbents. Reusability study showed the effective removal of PAT at four cycles by both adsorbents. This study indicated that carboxy- and amine-terminated magnetic spheres have promising potentials in PAT removal from both aqueous solution and apple juice without affecting quality parameters of juice.

Selective removal of mercury ions by functionalized Ti-Zr bimetallic coordination polymers

In order to effectively treat mercury pollution, a bimetallic coordination polymer (Ti/Zr-TA) was successfully synthesized by doping Ti metal for mercury removal in wastewater. The optimum pH (5.0), maximum adsorption capacity (298–318 K: 583.5, 615.4 and 654.4 mg/g), and thermodynamic behavior (endothermic) of Ti/Zr-TA was obtained by batch experiments. The adsorption process conforms to pseudo-second-order kinetic model and Hill isotherm model. Selectivity experiments confirmed that Ti/Zr-TA had a strong interaction with Hg(Ⅱ), which was more easily adsorbed than interfering ions. Adsorption-desorption experiments indicated that Ti/Zr-TA had excellent reusability, and the removal rate decreased by only 15.2 % after four cycles. In addition, the adsorption mechanism was revealed, mercury ions were adsorbated by electrostatic interaction and chelation, in which the chelation between the functional groups containing O, S and Hg(Ⅱ) was dominant.

Carbon-dot-modified polyacrylonitrile fiber as recyclable adsorbent for removing anionic, cationic, and zwitterionic perfluorooctane sulfonates from water

There are few adsorbents that can efficiently adsorb perfluorooctane sulfonate (PFOS) with differently polarized head-groups. In the present study, carbon dot (CD)-modified polyacrylonitrile fiber (PAN-g-CD) was found to be a good adsorbent for removing PFOS and its derivatives with zwitterionic or cationic head-groups from neutral water. The maximum adsorption capacities at 25 °C were found to be 1.28, 1.75, 1.87, and 2.11 mmol/g for PFOS, cationic PFOS, betaine-type PFOS, and PFOS with an amine oxide head-group, respectively. Adsorption kinetic models indicated that the surface of PAN-g-CD is energetically heterogeneous and that chemisorption occurs during the adsorption of PFOS and its derivatives. The Sips and Hill isotherm adsorption models were found to be most appropriate, and they indicated that PFOS derivatives were more preferentially adsorbed than PFOS by PAN-g-CD. The high-efficiency and wide substrate range of PAN-g-CD adsorption may be ascribed to its zwitterionic nature and its hydrophobic CDs. Moreover, PAN-g-CD can be regenerated and reused up to four times without pronounced loss of adsorption capacity.

Evaluation of pistachio shells as solid wastes to produce activated carbon for CO2 capture: Isotherm, response surface methodology (RSM) and artificial neural network (ANN) modeling

The adsorbent material selected for this study was microporous activated carbon prepared by physical activation from pistachio shells (PS). X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR), scanning electron microscopy (SEM), and analysis of N2 isotherms was used to determine the textural and structural character of this carbon material. The activated carbon from pistachio shells (AC-PS) indicted a specific surface area (Brunauer–Emmett–Teller specific area: SBET: 715.34 ​m2/g, and total pore volume: 0.346 ​cm3/g) and good sorption of CO2 (3.29 ​mmol/g at 25 ​°C and 5.682 ​bar). The effect of CO2 adsorption capacity as the response function was evaluated and optimized using response surface methodology (RSM) based on pressure and adsorption temperature as independent variables. A back-propagation training approach is used to create feed-forward multilayer perceptron (MLP) artificial neural network models to predict CO2 adsorption in this study. The experimental data of the adsorption experiments were analyzed and evaluated based on the isotherm and thermodynamic models. Adsorption data from the experiments followed the Hill isotherm model. Adsorption was an exothermic process, and there was mainly physical interaction. Minimum performance of 0.0011456 was determined by performing mean square error (MSE) validation at 22 epochs. The R2 values for the RSM and artificial neural network (ANN) models were 0.9957 and 0.999905, respectively. The results showed that the ANN and RSM models could be effectively used to estimate CO2 adsorption. According to these results, AC-PS would be a potential adsorbent for CO2 adsorption.

Lead Removal from Aqueous Solutions Using Bean Shells � Equilibrium, Kinetics, and Thermodynamic Studies

Lead ions removal from aqueous solutions onto bean shells is presented in this paper. The experiments were conducted in a batch system. The bean shells samples were rinsed with distilled water before the adsorption experiments. The analysis of the rinsed water showed that a significant amount of alkali and alkaline-earth metal ions are transferred from the adsorbent structure into the rinsed solution during the rinsing process. The COD analysis showed that these waters should be treated before being discharged into the surrounding watercourses. The influence of different process parameters (the pH value of the solution, the initial metal ions concentration, and the initial mass of the adsorbent) on the adsorption capacity was investigated. The adsorption capacity was higher at higher pH values of the solution. The adsorption capacity showed a decrease with the increase in the mass of the adsorbent. The increase in the initial metal ions concentration was shown to lead to an increase in the adsorption capacity until 0.8 g dm-3, after which a slight decrease was noted. Characterization of the adsorbent was performed by SEM-EDX, DTA-TGA, and FTIR analysis. The SEM-EDX analysis indicates a change in the morphology of the sample after the adsorption, as well as that K and Mg are possibly exchanged with lead ions during the adsorption process. The results obtained by the DTA-TGA analysis showed a weight loss of 77.8 % in the temperature range from 20oC to 900oC. The FTIR analysis indicated that the amide group is involved in the adsorption process. The pseudo-second order kinetic model was shown to be the best fit for the analyzed data, which led to the conclusion that chemisorption was a possible way of binding lead ions onto the surface of the bean shells. The Hill isotherm model was the best model for the analyzed adsorption equilibrium data. Obtained thermodynamic data indicated that the adsorption process was spontaneous, endothermic, and disordered, in which lead ions are bound to the surface of the bean shells by chemisorption. The maximum achieved adsorption capacity was 46.36 mg g-1.

Hyper-crosslinked tetraphenylborate as a regenerable sorbent for Cs+ sequestration in aqueous media through cation-π interactions

Practical adsorbents that could efficiently collect radioactive Cesium (Cs+) are critically important in achieving proper management and treatment measures for nuclear wastes. Herein, a hyper-crosslinked tetraphenylborate-based adsorbent (TPB-X) was prepared by reacting TPB anions as Cs+ binding sites with dimethoxymethane (DMM) as crosslinker. The most efficient TPB-X synthesis was attained at 1:4 TPB/DMM mole ratio with sorbent yield of 81.75%. Various techniques such as FTIR, TGA-DTG, N2 adsorption/desorption and SEM-EDS reveal that TPB-X is a water-insoluble, thermally stable and highly porous granular sorbent. Its hierarchical pore structure explains its very high BET surface area (1030 m2 g−1). Sequestration of Cs+ by TPB-X involves its exchange with H+ followed by its binding with the phenyl rings of TPB through cation-π interactions. The Cs+ adsorption in TPB-X is endothermic and spontaneous, which adheres to the Hill isotherm model (qm = 140.58 mg g−1) and follows pseudo-second order kinetics (k2 = 0.063 g mg−1 h−1). Calculations from the density functional theory reveal that the binding of TPB anion is strongest for Cs+. Thus, TPB-X was able to selectively capture Cs+ in simulated surface water containing Na+, K+, Mg2+, and Ca2+ and in HLLW containing Na+, Rb+, Sr2+, and Ba2+. Hyper-crosslinking was found beneficial in rendering TPB-X reusable as the sorbent was easily retrieved from the feed after Cs+ capture and was able to withstand the acid treatment for its regeneration. TPB-X exhibited consistent performance with no sign of chemical or physical deterioration. TPB-X offers a practical approach in handling Cs+ contaminated streams as it can be repeatedly used to enrich Cs+ in smaller volume of media, which can then be purified for Cs+ reuse or stored for long-term natural Cs+ decay process.

Soft computing-based models and decolorization of Reactive Yellow 81 using Ulva Prolifera biochar

The present research explores the application of optimization tools namely Response Surface Methodology (RSM), Artificial Neural Network (ANN) and Adaptive Neuro-Fuzzy Inference System (ANFIS) in the decolorization of Reactive Yellow 81 (RY81) from an aqueous solution. The characterization of the biochar was carried out using FTIR, elemental analysis, proximate analysis, BET analysis and Thermogravimetric analysis. Five independent variables namely solution pH, biochar dose, contact time, initial dye concentration and temperature were analyzed using RSM, ANN and ANFIS models. The maximum removal efficiency of 86.4% was obtained and the statistical error analysis was calculated. The correlation coefficient of 0.9665, 0.9998 and 0.9999 was obtained for RSM, ANN and ANFIS models, respectively. Adsorption Isotherm models and kinetic models were used to understand the adsorption mechanism. Maximum monolayer adsorption of 225 mg g−1 was predicted by Hill isotherm model. A partition coefficient of 4.09 L g−1 was obtained at an initial dye concentration of 250 mg L−1. It was revealed from the thermodynamic studies that reactions are endothermic and spontaneous. Further, to check the potential of the biochar, regeneration cycle was studied. The desorption efficiency of 99.5% was achieved at an S/L ratio of 3, regeneration cycles of 2, and sodium hydroxide was found as the best elutant for the desorption.

A sustainable nanocomposite, graphene oxide bi-functionalized with chitosan and magnetic nanoparticles for enhanced removal of Sudan dyes

The environmental pollution, particularly water pollution, has gradually caused severe human health issues. Organic dyes are one of the most emerging pollutants in the environment. In the present study, graphene oxide (GO) was functionalized with chitosan (CS) and magnetic nanoparticles (Fe-NPs) and tested to remove Sudan I, II, III, and IV dyes from water. The synthesized GO-CS-Fe was characterized using UV–vis, SEM, TEM, EDX, and FTIR spectroscopy, and confirmed the structural composition of nanocomposite, with the Fe-NPs dimension over the GO-CS surface to be 31–44 nm. The effects of various experimental factors; time,pH, adsorbent amount, dyes concentrations, and temperature were executed using the batch experiment. The experimental data were fitted to pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich kinetic models. The isotherm models parameters of the Langmuir, Freundlich, Redlich–Peterson, Temkin, and Hill isotherms, along with the thermodynamics parameters were also calculated. The data was explained by the Langmuir isotherm model with maximum adsorption capacities for Sudan I, II, III, and IV as 360.6, 353.7, 351.0, and 347.6 mg/g, respectively. The rapid uptake of the dyes fitted the pseudo-second-order kinetic, asserting that the adsorption was diffusion controlled. The process was spontaneous and endothermic in nature. The reusability study of GO-CS-Fe was performed up to five cycles. The nanocomposite can retain its efficacy even after the considered cycles. In conclusion, the GO-CS-Fe nanocomposite has exhibited a high potential for removing Sudan dyes from the aqueous solution due to its high adsorption and regeneration capability.

Piperazine-modified activated carbon as a novel adsorbent for CO2 capture: modeling and characterization.

In this study, activated carbon and piperazine-modified activated carbon adsorbents were prepared and used for CO2 adsorption. The effect of various parameters including adsorbent particle size, adsorbent amount, piperazine weight percent, pressure, and temperature were investigated on the CO2 adsorption capacity. The adsorbents were characterized using nitrogen adsorption/desorption isotherms and FTIR analyses. The results showed that the adsorption capacity decreases with temperature increasing and increases with pressure increasing. In addition, the surface modification of activated carbon improved the CO2 adsorption capacity more than the unmodified adsorbent, and the highest CO2 adsorption was obtained 203.842 mg/g at 25 °C and 8 bar. Additionally, to determine the adsorbent behavior, CO2 adsorption experimental data were fitted by isotherm and kinetic models. CO2 adsorption isotherm modeling was studied up to 8 bar at 25 °C, and kinetic modeling was investigated up to 85 °C at 6 bar. The results show that Hill isotherm model and Elovich kinetic models have a good agreement with the adsorption data. Finally, thermodynamic modeling was carried out for modified and unmodified adsorbents, and enthalpy, entropy, and Gibbs free energy changes of adsorption for piperazine-modified activated carbon at 25 °C and 6 bar obtained 17.078 kJ/mol, - 0.039 kJ/mol.K, and - 5.318 kJ/mol, respectively.

Cooperative Sorption on Porous Materials.

The functional shape of a sorption isotherm is determined by underlying molecular interactions. However, doubts have been raised on whether the sorption mechanism can be understood in principle from analyzing sorption curves via a range of competing models. We have shown recently that it is possible to translate a sorption isotherm to the underlying molecular interactions via rigorous statistical thermodynamics. The aim of this paper is to fill the gap between the statistical thermodynamic theory and analyzing experimental sorption isotherms, especially of microporous and mesoporous materials. Based on a statistical thermodynamic approach to interfaces, we have derived a cooperative isotherm, as a generalization of the Hill isotherm and our cooperative solubilization model, without the need for assumptions on adsorption sites, layers, and pore geometry. Instead, the statistical characterization of sorbates, such as the sorbate-interface distribution function and the sorbate number distribution, as well as the existence of statistically independent units of the interface, underlies the cooperative sorption isotherm. Our isotherm can be applied directly to literature data to reveal a few key system attributes that control the isotherm: the cooperative number of sorbates and the free energy of transferring sorbates from the saturated vapor to the interface. The sorbate–sorbate interaction is quantified also via the Kirkwood–Buff integral and the excess numbers.

Response surface methodology for strontium removal process optimization from contaminated water using zeolite nanocomposites.

The effective removal of strontium from polluted water is an emerging issue worldwide, especially in Japan, after the destruction of Fukushima's Daiichi Nuclear Power Plant. In the strontium removal process, statistical optimization of associated factors is needed to reduce the quantity of chemicals and the number of experimental trials. In this study, response surface methodology based on the central composite design was employed for assessing the influence of different factors and their interaction effects on the efficiency of strontium removal. We have considered nanoscale zero-valent iron-zeolite (nZVI-Z) and nano-Fe/Cu zeolite (nFe/Cu-Z) as adsorbents for the effective removal of strontium. The results suggested that the studied three factors such as pH, contact time, and concentration are positively related to the adsorption of strontium. That is, the maximum strontium removal occurred at pH, initial concentration, and contact time of 12, 200 mg L-1, and 30 min, respectively. The experimental maximum strontium adsorption capacity of nZVI-Z and nFe/Cu-Z adsorbents is 32.5 mg/g and 34 mg/g, respectively. The present study also showed that the most statistically significant potential contributor was initial concentration, followed by contact time in the removal process. The study indicated that the interaction effect between contact time and initial concentration was statistically important, suggesting the need for a multi-mechanism technique in the removal phase of strontium. Tόth, Langmuir, Dubinin-Astakhov (D-A), Freundlich, and Hill isotherm models were also fitted with the experimental strontium adsorption data, in which the Tόth model fitted best compared to the other models based on the RMSD and R2.