Spontaneous Adsorption Research Articles

Potential Water Collection From Air by Chloride Perovskites.

Directly capturing water from the air has become a compelling strategy to secure water resources. Yet, challenges persist with sorption-based hygroscopic materials, such as inadequate water adsorption efficiency, material degradation post-adsorption, and the need for energy input during water collection. This study introduces an alternative category of sorbent materials potentially for atmospheric water harvesting-metal chloride perovskites-that exhibit spontaneous water vapor adsorption and liquid water collection. This water uptake capability stems from the uncoordinated polar ions that form hydrogen bonds with water molecules, while the cubic lattice imparts a solid framework ensuring structural stability and inhibiting hydrolysis. The methylammonium lead chloride perovskite pellets exhibit efficient water collection performance, with a record absorption rate of 0.841 L m-2 h-1 and a total water collection of 3.675 L m-2 within a 7-h cycle. This initiative attempts to provide a new material class candidate for the potential application of passive atmospheric water harvesting.

Using the reactive/transport dispersive models to simulate a monolithic anion exchanger: Experimental parameter determination, simultaneous model evaluation, and validation.

Selecting an adequate model to represent the mass transfer mechanisms occurring in a chromatographic process is generally complicated, which is one of the reasons why monolithic chromatography is scarcely simulated. In this study, the chromatographic separation of model proteins bovine serum albumin (BSA), β-lactoglobulin-A, and β-lactoglobulin-B on an anion exchange monolith was simulated based on experimental parameter determination, simultaneous model testing, and validation under three statistical criteria: retention time, dispersion accuracies, and Pearson correlation coefficient. Experimental characterization of morphologic, physicochemical, and kinetic parameters was performed through volume balances, pressure drop analysis, breakthrough curve analysis, and batch adsorptions. Free Gibbs energy indicated a spontaneous adsorption process for proteins and counterions. Dimensionless numbers were estimated based on height equivalent to a theoretical plate analysis, finding that pore diffusion controlled β-lactoglobulin separation, whereas adsorption/desorption kinetics was the dominant mechanism for BSA. The elution profiles were modeled using the transport dispersive model and the reactive dispersive model coupled with steric mass action (SMA) isotherms because these models allowed to consider most of the mass transport mechanisms that have been described. RDM-SMA presented the most accurate simulations at pH 6.0 and at low (250mM) and high (400mM) NaCl concentrations. This simulation will be used as reference to forecast the purification of these proteins from bovine whey waste and to extrapolate this methodology to other monolith-based separations using these three statistical criteria that have not been used previously for this purpose.

Application of layered Nickel/Indium double hydroxide in the highly efficient removal of crystal violet dye from textile effluent

Worldwide freshwater demand will soon exceed supply if measures are not taken to mitigate inadequate wastewater treatment and its indiscriminate release into the environment. The textile industry is one of the largest consumers of freshwater and the third largest contributor to clean water pollution. Conventional treatment of textile effluent is inadequate and expensive. Adsorbent materials obtained from discarded solid waste precursors that contain high amounts of valuable metals can be an inexpensive way to obtain a highly efficient and low-cost wastewater treatment process. This study developed and explored a highly efficient adsorbent layered double hydroxide of Nickel and Indium (Ni/In-LDH) for the adsorption of widely used textile cationic dye, crystal violet (CV). The adsorbent material was synthesized by co-precipitation process of indium nitrate and nickel nitrate. The adsorbent material morphology and its adsorption capacity were investigated in different studies, such as the influence of pH, dosage, kinetics, isotherms, thermodynamics, ionic strength, adsorbent regeneration capacity, and interaction mechanisms of adsorption. Optimal operating conditions for Ni/In-LDH adsorption revealed maximum adsorption capacity Qmax of 570.94 mg g−1 at starting pH 8 and 60°C, which maintained approximately 75 % of the initial adsorption capacity in three successive adsorption/regeneration cycles. The experimental data fitted Pseudo first order kinetic model (PFO) and the Liu isothermal adsorption model. Thermodynamic studies indicated a spontaneous endothermic adsorption process, and a mechanism of physisorption of CV onto Ni/In-LDH substrate. After FTIR analysis of CV loaded Ni-In/LDH, electrostatic, hydrogen bonding, and n-π bonding interactions were suggested as the interaction mechanisms of adsorption. The Ni/In-LDH demonstrated excellent performance in the removal of CV dye in aqueous solutions compared to other high performing adsorbents.

D113 resin in-situ loaded with Fe3+ to develop glyphosate adsorbent with the characteristics of salt-resistance and the remarkable saturated adsorption capacity

There are inorganic salts in glyphosate production liquor and natural water bodies coexisting with glyphosate. It is imperative to develop a salt-tolerant adsorbent for glyphosate in water. Industrial D113 resin undergone two-step transformation to optimize the preparation of D113 in-situ loaded with Fe3+ (D113-Fe3+) as salt-resistance glyphosate adsorbent. The loading amount of Fe3+ on D113-Fe3+ is 3.5 mmol/g. The adsorption mechanism revealed that Fe3+ in D113-Fe3+ formed Fe-O-P bond with the phosphonate group of glyphosate. At 293 K, the maximum complex ratio of the adsorbed glyphosate to Fe3+ in D113-Fe3+ was 2.4:1. At 293 K, the remarkable saturated glyphosate adsorption capacity of D113-Fe3+ reached 1420.2 mg/g. In pK2 state of glyphosate, D113-Fe3+ featured its maximum adsorption capacity at the zero charge point 2.43 of D113-Fe3+ and 293 K. In glyphosate solution coexisting 0–16 % NaCl, D113-Fe3+ exhibited stable glyphosate adsorption capacity and salt-resistance compared with D201, D301 and 330 resin. The endothermic and spontaneous adsorption of glyphosate on D113-Fe3+ can fit Freundlich model and pseudo-second-order model. 2 mol/L NH3·H2O, 2 mol/L FeCl3 and 2 mol/L H2SO4 could all regenerate D113-Fe3+. The characteristics of salt-resistance and the remarkable saturated adsorption capacity made D113-Fe3+ comparable to all reported glyphosate adsorbents.

AI-based Prediction of Protein Corona Composition on DNA Nanostructures.

DNA nanotechnology has emerged as a powerful approach to engineering biophysical tools, therapeutics, and diagnostics because it enables the construction of designer nanoscale structures with high programmability. Based on DNA base pairing rules, nanostructure size, shape, surface functionality, and structural reconfiguration can be programmed with a degree of spatial, temporal, and energetic precision that is difficult to achieve with other methods. However, the properties and structure of DNA constructs are greatly altered in vivo due to spontaneous protein adsorption from biofluids. These adsorbed proteins, referred to as the protein corona, remain challenging to control or predict, and subsequently, their functionality and fate in vivo are difficult to engineer. To address these challenges, we prepared a library of diverse DNA nanostructures and investigated the relationship between their design features and the composition of their protein corona. We identified protein characteristics important for their adsorption to DNA nanostructures and developed a machine-learning model that predicts which proteins will be enriched on a DNA nanostructure based on the DNA structures' design features and protein properties. Our work will help to understand and program the function of DNA nanostructures in vivo for biophysical and biomedical applications.

2D-3D cyclodextrin-modified montmorillonite assembly for efficient directional capture of amines

Shale gas exploitation produces a large amount of waste liquid, which cannot be fully recovered and discharged. Discharged wastewater contains several chemicals, including petroleum hydrocarbons, salts, and heavy metals. Amine compounds can absorb harmful gases but may lead to the presence of these compounds in wastewater. Some amine compounds may cause DNA mutations and health threats to humans and animals. Inspired by the assembly of artificial two-dimensional structures, this paper attempts to shape montmorillonite (MMT) with a natural layered structure. Specifically, a functional 2D/3D amine compound collector within the limitations of 2D MMT (Mt) was prepared by self-assembling cyclodextrin molecules. With the assembly of cyclodextrin (CD) molecules, the two-dimensional Mt. layer length increased from 12.14 to 19.11 Å. Adsorption experiments revealed that functional MMT powder (FMP) has good trapping ability for amines, that the adsorption of amine groups on FMP decreases with increasing temperature, and that it has greater potential to remove amine compounds with fewer carbon chains. Through molecular dynamics simulation, it was found that there was a molecular binding energy between FMP and branched polyethyleneimine (BPEI), indicating that FMP had a spontaneous adsorption effect on BPEI. Furthermore, their adsorption favored the Langmuir isotherm model and the pseudo-second-order kinetic model. This study also provides a new collector for the total organic carbon (TOC) advanced treatment system. Compared with that of ozone and UV treatment, the removal rate of FMP is 10 times higher than that of activated carbon and active resin, which can better remove polar molecules and is beneficial for gas field water recovery.

The role of chitosan grafted copolymer/zeolite Schiff base nanofiber in adsorption of copper and zinc cations from aqueous media

The objective of this research was to develop and assess chitosan-grafted copolymer/HZSM5 zeolite Schiff base nanofibers for Cu2+ and Zn2+ adsorption from aqueous media. Nanofibers were prepared via electrospinning and characterized using XRD, FTIR, 1H NMR, FESEM, TGA, BET, and XPS. The study evaluated the effect of unmodified HZSM5 and Schiff base functionalization on adsorption capacities. Incorporating 10.0 wt% zeolite Schiff base as the optimum content into the chitosan-grafted copolymer significantly enhanced adsorption, achieving increases of 98.2 % for Zn2+ and 42.2 % for Cu2+. Specifically, Zn2+ adsorption increased from 27.6 to 54.7 mg/g, and Cu2+ from 67.1 to 95.4 mg/g. Factors such as temperature, pH, adsorption time, and initial cation concentration were analyzed. Kinetic studies revealed a double-exponential model, and isotherm analysis indicated a good fit with the Redlich-Peterson model, showing maximum monolayer capacities of 310.1 mg/g for Cu2+ and 97.8 mg/g for Zn2+ (pH 6.0, 240 min, 45 °C). The adsorption thermodynamics indicated a spontaneous and endothermic adsorption. Reusability tests showed minimal capacity loss (4.91 % for Cu2+ and 5.59 % for Zn2+) after five cycles. The nanofiber displayed greater selectivity for Cu2+ over Zn2+ in multi-ion systems and real electroplating wastewater, highlighting its potential for targeted heavy metal removal.

Simultaneous Removal of As(iii) and As(v) from Aqueous Solution by Using Iron-Functionalized Polythiophene: A Novel Approach toward Water Treatment.

Arsenic contamination in groundwater poses a significant threat to human health, affecting millions worldwide. This study presents a novel approach for simultaneous remediation of both As(III) and As(V) by using iron-functionalized polythiophene (PTh@Fe) composites. The PTh@Fe composite was synthesized by a reduction process involving FeCl2/FeCl3 byproducts of polymerization, resulting in a highly efficient adsorbent for both As(III) and As(V) species. The investigation systematically examined key parameters influencing arsenic removal, including adsorbent dosage, pH, initial arsenic concentration, and contact time. The composite exhibited exceptional adsorption capacities, with maximum removal percentages of 98.7% for As(III) and 98.8% for As(V) under the optimized conditions. Thermodynamic and kinetic analyses suggested endothermic and spontaneous adsorption processes following a pseudo 2nd-order mechanism. Furthermore, the Langmuir isotherm model provided an excellent fit to the experimental data, with maximum adsorption capacities of 8.62 mg/g for As(V) and 7.57 mg/g for As(III). Density functional theory (DFT) calculations confirmed the feasibility of arsenic adsorption onto iron species in various oxidation states, offering valuable theoretical insights into the process. Furthermore, the composite demonstrated good reusability over multiple adsorption-desorption cycles and tolerance to coexisting anions, highlighting its practical applicability for water purification. This research demonstrates the potential of iron-functionalized polythiophene composites as a promising solution for addressing arsenic contamination in water sources, bridging the gap between innovative materials and theoretical understanding in environmental science and water treatment technologies.

Synthesis, characterization, and physico-chemical aspects of a new PVC-based quaternary triethanol ammonium chloride anionite for tungsten recovery.

The usability of polyvinyl chloride-based quaternary triethanol ammonium chloride anionite (PVC-TEAC) as a potential extractant for tungstate was investigated to recover tungstate from Gabal Qash Amir, Egypt, assaying 70.91% WO3. Structure elucidation for PVC-TEAC anionite was successfully carried out using several techniques. Experimental measurements, such as pH, agitation time, initial tungsten concentration, anionite dose, co-ions, temperature, and eluting agents, have been optimized. It was found that PVC-TEAC anionite has a maximum capacity of 63 mg per gram. From the distribution isotherm modeling, Langmuir's model fits the experimental results better than Freundlich's, with a theoretical value of 61.728 mg g-1. According to kinetic modeling, the first- and second-order modeling may be regarded as a mixed modeling for a successful adsorption system. Thermodynamic prospects reveal that the adsorption process was predicted as an exothermic, spontaneous, and preferable adsorption at low temperatures. Tungsten ions can be eluted from the loaded anionite, by 1M H2SO4 with a 97% efficiency rate. It was found that PVC-TEAC anionite reveals good separation factor (S.F.) towards most of co-ions. A successful Alkali fusion with NaOH flux followed by tungstate recovery by PVC-TEAC anionite is used to obtain a high-purity tungsten oxide concentrate (WO3), with a tungsten content of 78.3% and a purity of 98.75%.

Development of banana pseudo stem cellulose fiber based magnetic nanocomposite as an adsorbent for dye removal

A hybrid hydrogel nanocomposite derived from cellulose fiber extracted from Banana Pseudo Stem (BPS) was developed as an adsorbent material for wastewater treatment. The hydrogel was developed by graft copolymerization of N-hydroxyethylacrylamide on Cellulose Fiber (BPSCF-g-PHEAAm) with potassium peroxodisulphate (KPS) as an initiator and N, N′-methylene bisacrylamide (MBA) as a crosslinker using microwave irradiation. Magnetic nanoparticles generated by an in-situ method were incorporated into the network structure. Fourier Transform Infrared Spectroscopy (FTIR), Powder X-ray Diffraction (XRD), Thermogravimetric analysis (TGA), Vibrating Sample Magnetometer (VSM), Brunauer-Emmett-Teller analysis (BET), Field Emission Scanning Electron Microscopy (FESEM), and Energy Dispersive Spectrometer (EDS) were employed. The adsorption capacities of hydrogel and its nanocomposite were evaluated using Methylene Blue (MB) and Crystal Violet (CV) as model dyes. The parent gel exhibited the maximum absorption capacity of 235, and 219 mg g−1 towards MB and CV respectively which was enhanced to 320 and 303 mg g−1 for the nanocomposite. Adsorption data were best fitted with the pseudo-second-order kinetic model and the Freundlich isotherm model. Negative ΔG° and positive ΔH° indicated spontaneous and endothermic adsorption. Desorption was effective to an extent of 99 % in the HCl medium suggesting high reusability potential of the developed adsorbent material.

Enhanced methylene blue adsorption using single-walled carbon nanotubes/chitosan-graft-gelatin nanocomposite hydrogels

In the present study, single-walled carbon nanotubes (SWCNTs) incorporating chitosan-graft-gelatin (CS-g-GEL/SWCNTs) hydrogels were fabricated with multiple advantages, including cost-effectiveness, high efficiency, biodegradability, and ease of separation for methylene blue (MB) dye from aqueous solution. To verify the successful formulation of the prepared hydrogels, various characterization methods such as NMR, FTIR, XRD, FE-SEM, TGA, BET, and EDX were employed. The removal efficiency of CS-g-GEL/SWCNTs nanocomposite hydrogel increased significantly to 98.87% when the SWCNTs percentage was increased to 20%. The highest adsorption was observed for pH = 9, an adsorbent dose = 1.5 g L−1, a temperature = 25 °C, a contact time = 60 min, and a contaminant concentration = 20 mg L−1. Based on the thermodynamic results, spontaneous adsorption occurred from a negative Gibbs free energy (ΔG°). In addition, the thermodynamic analysis of the adsorption process revealed an average enthalpy of − 21.869 kJ mol−1 for the adsorption process at a temperature range of 25–45 °C, which indicates its spontaneous and exothermic behavior. The Langmuir isotherm model was successfully used to describe the equilibrium behavior of adsorption. The pseudo-first-order model better described adsorption kinetics compared to the pseudo-second-order, intra-particle, and Elovich models. CS-g-GEL/SWCNTs hydrogels have improved reusability for five consecutive cycles, suggesting that they may be effective for removing anionic dyes from aquatic environments.

In-Depth Investigation of Role of -BCO2 in the Degradation of Sulfamethazine by Metal-Free Biochar/Persulfate: The Mechanism of Occurrence of Nonradical Process.

The remediation of organic wastewater through advanced oxidation processes (AOPs) based on metal-free biochar/persulfate systems has been extensively researched. In this work, boron-doped alkali lignin biochar (BKC1:3) was utilized to activate peroxymonosulfate (PMS) for the removal of sulfamethazine (SMZ). The porous structure and substantial specific surface area of BKC1:3 facilitated the adsorption and thus degradation of SMZ. The XPS characterization and density functional theory (DFT) calculations demonstrated that -BCO2 was the main active site of BKC1:3, which dominated the occurrence of nonradical pathways. Neither quenching experiments nor EPR characterization revealed the generation of free radical signals. Compared with KC, BKC1:3 possessed more electron-rich regions. The narrow energy gap (ΔEgap = 1.87 eV) of BKC (-BCO2) promoted the electron transfer to the substable complex (BKC@PMS*) on SMZ, driving the electron transfer mechanism. In addition, the adsorption energy of BKC(-BCO2)@PMS was lower (-0.75 eV → -5.12 eV), implying a more spontaneous adsorption process. The O-O (PMS) bond length in BKC(-BCO2)@PMS increased significantly (1.412 Å → 1.481 Å), which led to the easier decomposition of PMS during adsorption and facilitated the generation of 1O2. More importantly, a combination of Gaussian and LC-MS techniques was hypothesized regarding the attack sites and degradation intermediates of the active species in this system. The synergistic T.E.S.T software and toxicity tests predicted low or even no toxicity of the intermediates. Overall, this study proposed a strategy for the preparation of metal-free biochar, aiming to inspire ideas for the treatment of organic-polluted wastewater through advanced oxidation processes (AOPs).

Facile synthesis of poly(tannic acid-1,4-butanediamine) microsphere based on the “self-assembly to polymerization” mechanism and its fast removal feature toward Cr(VI) ions

To remediate toxic Cr(VI) ions in wastewater is a daunting environmental challenge nowadays, thus advanced adsorbents are developed and used to overcome the low removal rate of existing technologies. Herein, poly(tannic acid-1,4-butanediamine) (PTBA) microspheres were synthesized for the purpose of fast removal of Cr(VI) from the aqueous phase. The synthesis was based on the “self-assembly to polymerization” mechanism. The microstructures and chemical characteristics of the fresh and used adsorbents PTBA were characterized systematically by means of TEM, SEM, FT-IR, XPS, TGA and XRD. Effects of pH, contact time, Cr(VI) initial concentration, PTBA dosage, temperature, and the presence of foreign ions on the removal of Cr(VI) had been investigated sequentially. The results indicated that almost 100% of removal efficiency could be achieved in short time intervals, based on the initial concentration of Cr(VI). The spontaneous and endothermic adsorption behavior could be well described by the pseudo-2nd-order (P2O) and Langmuir isotherm models. Finally, the process of partial reduction of Cr(VI) to non-toxic Cr(III) during the adsorption process was explained. Overall, the refined PTBA adsorbent presents a satisfactory behavior to ameliorate the Cr(VI)-pollution elimination means.

Biodegradable Acid-Based Fe2MnO4 Nanoparticles for Water Remediation.

This study demonstrated the synthesis of Fe2MnO4 modified by citric acid, a biodegradable acid, using a simple co-precipitation method. Characterization was performed using qualitative analysis techniques such as Fourier-transformed infrared spectroscopy, scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy, X-ray diffraction, selected-area electron diffraction, N2 adsorption-desorption, and zero-point charge. The prepared nanoparticles had a rough and porous surface, and contained oxygenous (-OH, -COOH, etc.) functional groups. The specific surface area and average pore size distribution were 83 m2/g and 5.17 nm, respectively. Net zero charge on the surface of the prepared nanoparticles was observed at pH 7.5. The prepared nanoparticles were used as an adsorbent to remove methylene blue dye from water under various conditions. Using small amounts of the adsorbent (2.0 g/L), even a high concentration of MB dye (60 mg/L) could be reduced by about ~58%. Exothermic, spontaneous, feasible, and monolayer adsorption was identified based on thermodynamics and isotherm analysis. Reusability testing verified the stability of the adsorbent and found that the reused adsorbent performed well for up to three thermal cycles. Comparative analysis revealed that the modified adsorbent outperformed previously reported adsorbents and unmodified Fe2MnO4 in terms of its partition coefficient and equilibrium adsorption capacity under different experimental conditions.

Petroleum residue-based ultrathin-wall graphitized mesoporous carbon and its high-efficiency adsorption mechanism

Creating petroleum residue-based new functional materials are vital for the sustainable development of petroleum residues. This study developed a method to prepare a petroleum residue-based ultrathin-wall graphitized mesoporous carbon (PGMC) with high specific surface area by the carbonization of a composite of the petroleum residue uniformly mixed with aluminium isopropoxide. Results show that the PGMC possesses a highly fluffy ultrathin-wall mesoporous structure with a high degree of graphitization. It had a high specific surface area of 1174 m2 g−1 with a high pore volume of 4.57 cm3 g−1 and a narrow pore size distribution at 8.09 nm. These unique features endow the PGMC with excellent adsorption properties for Congo red, Malachite green, and Methylene blue removal. The experimental data were better described with Freundlich isotherm and Quasi-second-order kinetic models. Thermodynamic analysis indicated a spontaneous and endothermic adsorption process. The adsorption mechanisms proposed that pore-filling effect, π-π conjugation, and electrostatic interaction were the main interactions between the PGMC and dyestuff, followed by functional groups and hydrogen bonding. Moreover, the PGMC could maintain good adsorption rates after five cycles, proving that it is an effective adsorbent with good adsorption ability and cycling stability.

Super-efficient removal of yellow 161 anionic dye from water by activated carbon based on coffee grounds

The study evaluates the effectiveness of activated carbon derived from coffee grounds (ACcg) in removing Reactive Yellow 161, a pollutant from the textile industry. The properties of ACcg are analyzed by various techniques such as FTIR, SEM, EDS and X-ray diffraction. In addition, physico-chemical analyses, such as moisture content, ash content, volatile matter, iodine value and zero charge point (pHpzc), were carried out on the prepared ACcg. The Box-Behnken Design (BBD) scheme combined with the Response Surface Method (RSM) is used to optimize adsorption variables. Results show high microporosity of ACcg, adsorption kinetics fitted to pseudo-first order and Langmuir isotherm consistent with experimental data. Thermodynamic parameters indicate spontaneous and exothermic adsorption behavior. Residue analysis and ANOVA confirm a high adsorption capacity of ACcg (97.67 %) at an initial concentration of 20 ppm Reactive Yellow, with an ACcg mass of 1 g/L and a pH of 3. The chosen model is validated for this application.

Peanut shell biochar for Rhodamine B removal: Efficiency, desorption, and reusability

A high-performance and affordable peanut shell-derived biochar was employed for the efficient removal of Rhodamine B (RhB) from aqueous solutions. The properties of peanut shell biochar (PSB) were investigated through Fourier transform infrared (FTIR) spectroscopy and Brunauer–Emmett–Teller surface area measurements. The FTIR analysis revealed numerous active sites and functional groups for the binding of dye molecules, while the BET surface area was determined to be 351.11 m2g-1. Four different isotherms and kinetic models were applied to determine the equilibrium adsorption of RhB, and the results indicated that the Freundlich isotherm was the most appropriate model. A maximum dye removal rate of 94.0% occurred at a pH of 3 with an adsorbent dose of 0.325 g L−1. The prepared adsorbent showed excellent sorbent behaviour and can be reused multiple times after regeneration, with the surface area decreasing from 351.11 m2g-1 to 140.13 m2g-1 after the third cycle. The negative Gibbs free energy ΔGo at all applied temperatures suggested that spontaneous adsorption occurred and RhB adsorption on the PSB was found exothermic, as evidenced by the negative value of ΔHo. The regenerated PSB can be utilized as an efficient, environmentally friendly, and cost-effective sorbent for the removal of dyes at temperatures lower than ambient temperature, providing both technical and financial advantages for sustainable environmental management.

Insight into adsorption-desorption of methylene blue in water using zeolite NaY: Kinetic, isotherm and thermodynamic approaches

It is critical to find an efficient method to separate methylene blue (MB) in wastewater before discharging them into environment. Adsorption using zeolites is the most commonly used one. To determine adsorption mechanism providing useful data to enhance adsorption capacity and practicability of scale-up, kinetic, isotherm and thermodynamic adsorption were evaluated and discussed intensely. Zeolite NaY was synthesized from rice husk ash with a one-stage process. Effects of pH, contact time, initial concentration, adsorbent dose, temperature, solvents and recyclic stability on MB adsorption and desorption were investigated in detail via alternating variable method. Optimal conditions for adsorption were at pH 8, 1 h, 50 mgMB/L, 303K. Adsorption kinetics and isotherms showed that the process fitted to pseudo-second-order, Freundlich and Temkin isotherm, indicating a spontaneous, exothermic and physical adsorption process with multilayer adsorption. Desorption process showed that EtOH:H2O (1:1) solvent at 323K was optimal for releasing MB and its thermodynamic studies revealed that this process was favorable with rising temperature. The maximum adsorption capacity was calculated as 49 mg/g and the adsorbent could maintain its adsorption performance after six cycles. Generally, this study provided a comprehensive approach of an efficient, cost-effective, and recyclable NaY for MB removal from water.

Thermodynamics, kinetic study and equilibrium isotherm analysis of cationic dye adsorption by ternary composite

This article investigates the kinetics, equilibrium, and thermodynamics of brilliant green dye adsorption on Fe3O4/CdS/MWCNTs. The effects of adsorbent dosage (0.01–0.06 g), contact time (1–120 min), temperature (278, 288,298 and 308 K), ionic strength (NaCl and CaCO3 salt), and initial solution pH (4,6,7, and 10) were all studied in relation to the adsorption of BG dye. Langmuir (R2 = 0.86883), Temkin (R2 = 0.96323) and Freundlich (R2 = 0.96958) and isotherms were fitted to describe the equilibrium of BG adsorption process. Isothermal models showed that BG adsorption was a favorable process on ternary composite Adsorption kinetics were well fitted by Pseudo-second order kinetic model (R2 = 0.99396). The thermodynamic parameters ΔH° = −0.0277 kJ.mol−1 and ΔS° = −60.9031 J mol−1.k−1 indicate endothermic and spontaneous adsorption process, (ΔG° > 0) non-spontaneous, and exothermic. Five adsorption/desorption cycles were demonstrated by the adsorbents’ high reusability.

Selective recovery of esterase from Trichoderma harzianum through adsorption: Insights on enzymatic catalysis, adsorption isotherms and kinetics

In recent years, numerous attempts have been made to develop a low-cost adsorbent for selectively recovering industrially important products from fermentation broth or complex mixtures. The current study is a novel attempt to selectively adsorb esterase from Trichoderma harzianum using cheap adsorbents like bentonite (BT), activated charcoal (AC), silicon dioxide (SiO2), and titanium dioxide (TiO2). AC had the highest esterase adsorption of 97.58% due to its larger surface area of 594.45 m3/g. SiO2 was found to have the highest selectivity over esterase, with an estimated purification fold of 7.2. Interestingly, the purification fold of 5.5 was found in the BT-extracted fermentation broth. The functional (FT-IR) and morphological analysis (SEM-EDX) were used to characterize the adsorption of esterase. Esterase adsorption on AC, SiO2, and TiO2 was well fitted by Freundlich isotherm, demonstrating multilayer adsorption of esterase. A pseudo-second-order kinetic model was developed for esterase adsorption in various adsorbents. Thermodynamic analysis revealed that adsorption is an endothermic process. AC has the lowest Gibbs free energy of −10.96 kJ/mol, which supports the spontaneous maximum adsorption of both esterase and protein. In the desorption study, the maximum recovery of esterase from TiO2 using sodium chloride was 41.34 %. Unlike other adsorbents, the AC-adsorbed esterase maintained its catalytic activity and stability, implying that it could be used as an immobilization system for commercial applications. According to the kinetic analysis, the overall rate of the reaction was controlled by reaction kinetics rather than external mass transfer resistance, as indicated by the Damkohler number.