Adsorption Kinetic Studies Research Articles

"Off/On” Fluorescent Probe based on Aggregation-Induced Quenching of ZnO-Quantum dots for Determination of Ara-C: Pharmacokinetic Applications, Adsorption Kinetics & Green Profile Assessment

Herein, a turn “Off/On” fluorescence probe based on ZnO quantum dots (ZnO-QDs) has been proposed and successfully utilized for the determination of Ara-C (cytarabine) using ceric ions (Ce4+) as quencher and ethylenediamine (ED) as a linker. The probe is based initially on the quenching effect of Ce4+ ions on the strong native fluorescence of ZnO-QDs forming the Turn Off system (Ce@ZnO-QDs) that believed to occur due to the aggregation-induced quenching (AIQ) mechanism. The second step is the addition of Ara-C in the presence of ethylenediamine (ED) that encourages the formation of Ara-C/ED/Ce4+ as well as the release of the free ZnO-QDs, leading to the recovery of the fluorescence intensity. The developed sensing platform shows a linear response towards Ara-C over the range of 10 to 1000 ng mL−1 giving a limit of detection (LOD) and limit of quantitation (LOQ) of 1.22 ng mL−1 and 3.70 ng mL−1, respectively. A dispersive magnetic solid phase micro-extraction (dMSPE) method was developed and optimized for the extraction of Ara-C in spiked human plasma using thiol-modified magnetite nanoparticles (S-MNPs). The proposed platform exhibits good sensitivity toward Ara-C in the presence of different interfering substances. Excellent recoveries are obtained after spiking different concentrations of Ara-C into rabbit plasma samples. The validated experimental parameters have been successfully applied to monitor the pharmacokinetic profile of Ara-C in rabbit plasma. A detailed adsorption kinetics study has been carried out to provide a deep insight into the adsorption behavior of Ara-C on the thiol-doped-magnetite nanoparticles. The greenness assessment of the proposed method was achieved and compared with other reported methods using two tools of greenness; the green analytical procedure index (GAPI) and the analytical greenness calculator AGREE.

Metal-Mediated DNA Adsorption on Carboxylated, Hydroxylated, and Hydrogenated Nanodiamonds.

Nanodiamonds (NDs) have attracted considerable attention owing to their quantum properties and versatility in biological applications. In this study, we systematically investigated the adsorption of DNA oligonucleotides onto NDs with three types of surface groups: carboxylated (COOH-), hydroxylated (OH-), and hydrogenated (H-). Among them, only the H-NDs showed fluorescence quenching property that is useful for real-time DNA adsorption kinetic studies. The effect of common metal ions on DNA adsorption was studied. In the presence of Na+, the order of DNA adsorption efficiency was H- > OH- > COOH-, whereas all the NDs showed a similar DNA adsorption efficiency in the presence of divalent metal ions such as Ca2+ and Zn2+. Desorption studies revealed that hydrogen bonding and metal-mediated interactions were dominant for the adsorption of DNA, and the H-NDs exhibited extraordinarily tight DNA adsorption. Finally, a fluorescently labeled DNA was adsorbed on NDs for DNA detection, and the COOH-NDs had the highest target specificity, and a detection limit of 1.4 nM was achieved. This study indicates the feasibility of using metal ions to mediate the physical adsorption of DNA to NDs and compares various NDs with graphene oxide for fundamental understanding.

Improvement of Photocatalytic Degradation and Adsorption of Ciprofloxacin by Bismuth Oxyiodide

AbstractBismuth oxyiodide (BiOI) hierarchical structures were fabricated by the solution route at room temperature (BiOI‐R) and solvothermal synthesis (BiOI‐S) in the presence of KI and ethylene glycol to improve the photocatalytic and adsorption ability for the removal of ciprofloxacin from the aqueous environment. BiOI was characterized by X‐ray diffraction, scanning electron microscopy, N2 adsorption‐desorption isotherm, UV‐Vis absorption spectroscopy, and pH of the point of zero charge. It was observed that BiOI‐S has better adsorption and photocatalysis capacity as a result of having higher surface area, higher light absorption ability, and lower band‐gap energy than BiOI‐R. BiOI‐S exhibited good ciprofloxacin adsorption and photocatalytic degradation under visible‐light irradiation. Adsorption isotherm and kinetic studies fitted the Langmuir and Freundlich isotherm and pseudo‐second‐order models respectively. The photocatalytic degradation of ciprofloxacin by BiOI‐S followed a pseudo‐first‐order reaction based on Langmuir‐Hinshelwood kinetics.

Process parameter study and kinetic of remazol dye adsorption onto local rice husk‐based organic porous materials

AbstractRemazol Brilliant Blue dye (RBB) is a harmful dye from the textile industry that can damage the environment and aquatic life. Since RBB is impossible to degrade in water by primary and secondary wastewater treatment, its removal is a challenge. An excellent treatment procedure is urgently anticipated to avoid the pollution spreading into the environment. Moreover, rice husk waste (RH) in Malaysia is abundant and generally dumped into landfills. Turning the waste into a value‐added product such as biochar as an effective adsorbent material for treating water pollutants is one of the initiatives in realizing the circular economy agenda. This study develops an organic porous material of biochar from RH and assesses the kinetic of RBB adsorption onto the rice husk biochar (RHB) in aqueous solution. The production of RHB was optimized by pyrolysis procedure at various temperatures, times, and particle sizes. The removal of RBB dye by RHB was investigated at different exposure times from 0 to 120 min under 100 rpm shaken and immersed conditions. The reduction of RBB concentrations using different RHB pyrolysis conditions has also been investigated. The dye removal efficiency by RHB increased with time and the highest removal efficiency (69.3%) was achieved by the smallest particle size of RHB which was produced at the highest pyrolysis temperature of 400°C (RHB‐400). The total pore volume and BET surface area of RHB‐400 were found to be 50.4827 m2/g and 0.00875 cm3/g, respectively. The adsorption kinetic study signifies that maximum adsorption has been completed within 90–120 min depending on the RHB conditions whereas two kinetic models such as pseudo‐first order and pseudo‐second order kinetic models were utilized to fit the experimental data and the results are more consistent with pseudo‐second order kinetic models. This study revealed that RHB can be used as adsorbent materials for dye removals, yet it is economical, environmentally friendly, and sustainable.

Removal of Cationic Crystal Violet dye using Zeolite‐ Embedded Carboxymethyl Tamarind Kernel Gum (CMTKG) based Hydrogel Adsorbents

AbstractIn this research paper, various formulations of zeolite‐loaded carboxymethyl tamarind kernel gum (CMTKG) based hydrogels were synthesized and utilized as a potential adsorbent for the removal of crystal violet (CV) dye. The swelling capacity of all the synthesized hydrogels was investigated and the composition of hydrogel which exhibited maximum swelling was used for the characterization and dye removal experiment. The CV dye was chosen as a model dye for the dye removal experiment. The structure of zeolite and zeolite embedded hydrogel was elucidated by XRD, FTIR, FE‐SEM, EDX and elemental papping techniques. The adsorption experiment was investigated by varying the CV concentration, amount of hydrogel adsorbent, temperature, pH of the dye solution, adsorption time, and ionic strength. The Langmuir and Freundlich isotherm models were used to fit the adsorption data and it was observed that the data fitted well with the Langmuir model. Moreover, hydrogel‘s maximum dye adsorption efficiency was found at 123.60 mg g−1. The adsorption kinetic studies were followed by pseudo‐ first‐order and intraparticle diffusion kinetic models. In addition, regeneration studies were performed for the best adsorbent hydrogel using ethanol solvent and the result concluded the desorption efficiency of hydrogel (82 %) over four desorption cycles.

Active Cellulose Acetate/Chitosan Composite Films Prepared Using Solution Blow Spinning: Structure and Electrokinetic Properties.

Cellulose acetate (CA), a very promising derivative of cellulose, has come into the focus of research due to its highly desired good film-forming ability for food packaging applications. Frequently, this derivative is used in combination with other compounds (polymers, nanoparticles) in order to obtain active materials. Here, we report the preparation of thin films made of cellulose acetate loaded with chitosan (CS) using the solution blow spinning (SBS) method. Films are prepared by SBS processing of the polymers mixture solution, considering the following variables: (i) the concentration of cellulose acetate and chitosan in the solution and (ii) the solvent system consisting of acetic or formic acid. The prepared materials are characterized in terms of physical properties, roughness (optical profilometer), porosity, wettability (contact angle measurements), chemical structure (Fourier transform infrared spectrometry), and electrokinetic properties (zeta potential). SBS enables the preparation of CA/CS films with high water vapor permeability, high porosity, and also higher water contact angle compared with pure CA films. The electrokinetic properties of composites are influenced by the inclusion of chitosan, which causes a shift of the isoelectric point (IEP) towards higher pH values, but the magnitude of the shift is not in correlation with chitosan concentration. Adsorption kinetic studies using bovine serum albumin (BSA) as a model protein reveal that chitosan modified cellulose acetate films manifest low affinity towards proteins that suggests prevention of biofilm formation on its surface.

Understanding the process in the removal of dimethylarsenic by a zirconium-based nanoparticle

Organic arsenic contamination in groundwater and surface water is one of threats to human beings. In this study, a novel zirconium-based nanoparticle was developed to remove dimethylarenic acid (DMA) from aqueous solution. The adsorption behavior was evaluated by various batch adsorption experiments. The pH effect study revealed that the maximum adsorption was achieved around pH 3.0. The ionic strength did not have significant effect on the uptake of DMA. The adsorption kinetics study showed that the adsorption equilibrium was established within 24 h; an intraparticle kinetics model fit the experimental data well. In the adsorption isotherm study, the Langmuir equation described the adsorption data better than the Freundlich equation; the maximum adsorption capacity of the sorbent was calculated to be 58.82 mg-As/g at the optimal pH. In the natural organic matters and coexisting anions effect studies, the presence of humic acid and coexisting anions have little effect on the uptake of DMA. The performance of the Zr-based NP was not largely inhibited in the presence of NOMs and coexisting anion. The FTIR and XPS spectroscopic analyses demonstrated that DMA was successfully adsorbed onto the sorbent and the adsorption mechanism was proposed to be ions exchange between arsenic and sulfate ions.

Wine putrescine abatement by bentonites: From ideal case to practice.

Herein, we demonstrated that bentonites can be incisively used to reduce wine BAs content, especially putrescine molecules. Pioneering kinetic and thermodynamic studies of putrescine adsorption onto two commercially available bentonites (optimal concentration of 0.40gdm-3) were performed resulting in ca. 60% removal by physisorption mechanism. Both bentonites showed also promising results in more complex systems, resulting in a lower putrescine adsorption due to the competition with other molecules (as proteins, polyphenols), typically present in wines. Nonetheless, we managed to reduce the putrescine content below 10ppm both in red and white wines.

Fabrication of Nitrogen-Doped Carbon@Magnesium Silicate Composite by One-Step Hydrothermal Method and Its High-Efficiency Adsorption of As(V) and Tetracycline.

Tetracycline (TC) and arsenic contaminants are two main pollutants in aquaculture and livestock husbandry, and they have drawn worldwide attention. To address this issue, a novel N-doped carbon@magnesium silicate (CMS) was fabricated via a facile and low-cost hydrothermal route, adopting glucose and ammonia as C and N sources, respectively. The synergetic combination of carbon and magnesium silicate makes CMS possess a high surface area of 201 m2/g and abundant functional groups. Due to the abundant C- and N-containing functional groups and Mg-containing adsorptive sites, the maximum adsorption capacity values of CMS towards As(V) and TC are 498.75 mg/g and 1228.5 mg/g, respectively. The type of adsorption of As(V) and TC onto CMS is monolayer adsorption. An adsorption kinetic study revealed that the mass transfer and intraparticle process dominates the sorption rate of As(V) and TC adsorption onto CMS, respectively. Various functional groups synthetically participate in the adsorption process through complexion, π-π EDA interactions, and hydrogen bonds. This work provides a one-step, low-cost route to fabricate a N-doped carbonaceous adsorbent with a high surface area and abundant functional groups, which has great potential in the application of practical sewage treatment.

Removal of Boron from Simulated Iraqi Surface Water by Electrocoagulation Method

The removal of boron from aqueous solution was carried out by electrocoagulation (EC) using magnesium electrodes as anode and stainless steel electrodes as cathode. Several operating parameters on the removal efficiency of boron were investigated, such as initial pH, current density, initial boron ion concentration, NaCl concentration, spacing between electrodes, electrode material, and presence of carbonate concentration. The optimum removal efficiency of 91. 5 % was achieved at a current density of 3 mA/cm² and pH = 7 using (Mg/St. St. ) electrodes, within 45 min of operating time. The concentration of NaCl was o. 1 g/l with a 0.5cm spacing between the electrodes. First and second order rate equation were applied to study adsorption kinetics. The adsorption process follows second order kinetic model with good correlation. The energy consumption was evaluated for the optimum operating conditions. It was in the range of 1.296 to 1.944 Kwh/m3 . The overall expected increase in the operating cost of water treatment using membrane desalination facility (for example) will be about 20%.

Cinética e isotermas de adsorción de penconazole, cyproconazole y epoxiconazole con quitosano

En la búsqueda de tecnologías alternativas que puedan mitigar la problemática de la contaminación en las fuentes de agua, fundamentalmente a las destinadas para consumo humano, se ha evaluado la eficiencia del quitosano en polvo para la remoción de plaguicidas. En los procesos de adsorción existe un amplio espectro de mecanismos físicos y químicos, los cuales ocurren normalmente en etapas consecutivas tales como la difusión del adsorbato a través de la película de fluido hasta el material adsorbente, difusión a través de los poros y posterior reacción de adsorción. En este proceso se pudo observar que cada analito, en función de sus propiedades fisicoquímicas y/o estructurales, presentó adsorciones diferentes, lo que se evidenció en la variación de los valores de los porcentajes de remoción de los plaguicidas utilizando cantidades iguales de adsorbente. La optimización de las variables de remoción permitió determinar que los valores que maximizan el porcentaje de remoción para la mayoría de los analitos son similares y se encuentran próximos a los máximos de tiempo de contacto y cantidad de adsorbente. El estudio de la cinética de adsorción permitió establecer el tiempo de equilibrio el que fue de 180 minutos para los analitos, y la modelización de los datos respondió a una cinética de pseudo-segundo orden. Respecto a la modelización de las isotermas de adsorción, el modelo de mejor ajuste es el de Freundlich. Frente a esta compleja temática cobra relevancia la evaluación de la remoción de plaguicidas mediante procesos tecnológicos con el objetivo de lograr mantener la disponibilidad de los recursos hídricos con adecuada calidad.

Enhancing the Immobilization of Hexavalent Chromium by the Interlayer Anion Adsorption of the Brucite-Transformed LDH in the Presence of Aluminum Ions

Current studies of chromium adsorption kinetics at the solid–liquid interface often neglect the influence of coexisting ions in complex wastewaters. Thus, it is critical to explore the hexavalent chromium Cr(VI) adsorption kinetics of solid-phase brucite (Mg(OH)2) in liquid-phase wastewater containing coexisting aluminum ions (Al(III)). This paper reveals that the presence of Al(III) significantly enhanced the Cr(VI) adsorption efficiency onto Mg(OH)2, with a peak of up to 91% compared to 5% for the absence of Al(III). The main reason for this enhancement was the initial surface ternary complexation of Mg(OH)2 and the cationic (Al(III)) isomorphic substitution to form Mg(II)-Al(III) layered double hydroxides (LDH), which also indicates a solid-phase transition on the surface of Mg(OH)2, which led to electrostatic adsorption in the gallery and made Cr(VI) immobilized and not readily released. Further calculation and analysis of the adsorption energy confirmed the mechanism of Cr(VI) adsorption. It was also concluded that Cr(VI) migration in Mg(OH)2-containing minerals was affected by the phase transformation of solids in the presence of Al(III). Hence, this study not only reveals the adsorption mechanism during the treatment of composite pollutant wastewater but also provides the methodological reference for brucite synergistic adsorption to remove heavy metal ions and purify and treat complex polluted wastewater.

Chitosan-based hydrogel system for efficient removal of Cu[II] and sustainable utilization of spent adsorbent as a catalyst for environmental applications

The growing requirement for clean potable water requires sustainable methods of eliminating heavy metal ions and other organic contaminants. Herein, we synthesized a novel dual-purpose magnetically separable chitosan-based hydrogel system (CSGO-R@IO) that can efficiently remove toxic Cu2+ pollutants from water. FT-IR, XRD, SEM-EDX, VSM, XPS analyses were used to characterize the synthesized hydrogel. The CSGO-R@IO hydrogel showed high swelling capacity (1036.06 %), prominent adsorption capacity for Cu2+ ions (119.5 mg/g), and good recyclability up to four cycles. The adsorption data of Cu+2 ions on hydrogel fitted better to the Langmuir isotherm model (R2 = 0.9942), indicating spontaneous monolayer adsorption of Cu2+ ions on a homogenous surface. The adsorption kinetic studies fitted better with the pseudo-second-order model (R2 = 0.9992), suggesting that the adsorption process was controlled by chemisorption. We also showed a sustainable way to convert harmful Cu2+ pollutants into valuable Cu nanoparticles for catalysis, and Cu nanoparticles loaded hydrogel (CSGO-R@IO/Cu) had high catalytic activity. Hence, building attractive multipurpose hydrogel systems will give us new ideas about how to design and use new adsorbents to clean water in real life. They will also help in recycle metals (copper and maybe others) to conserve resources.

Thermodynamics and Kinetics Studies of Phenol Adsorption on to Anchote Peel Activated Carbon Adsorbent

Thermodynamics and Kinetics Studies of Phenol Adsorption on to Anchote Peel Activated Carbon Adsorbent

Hemicellulose-g-PAAc/TiO2 Nanocomposite Hydrogel for Dye Removal

Dyes pollution on urban environment is of great concern because of the human health hazards associated with this kind of contaminants, and the use of low-cost photocatalytic composite material is an efficient treatment method to minimize the environmental impact. A novel hemicellulose-g-PAAc/TiO2 composite hydrogel was prepared as a promising alternative material for dye removal. Wheat straw hemicellulose and TiO2 nanoparticles were first modified and then incorporated into hydrogel via covalent bonds. Effects of gel dosage, pH, initial concentration and contact time on the adsorption amount of methylene blue were systematically studied using the prepared hydrogel. The equilibrium adsorption data was fitted well to the Freundlich isotherm model, and Langmuir isotherm analysis indicated that the adsorption capacity of the hemicellulose-g-PAAc/TiO2 composite hydrogel was 389.1 mg/g, and adsorption kinetic study showed that the adsorption process can be described by the pseudo second-order kinetic model. The prepared composite hydrogel exhibited high photodegradation ability for methylene blue under alkaline conditions, and all results indicated that the hemicellulose-g-PAAc/TiO2 composite hydrogel had excellent photocatalytic degradability for dyes, which can be used in practical process.

Thermodynamics and kinetics studies of Phenol adsorption on to Anchote peel activated carbon adsorbent

Thermodynamic and kinetics (pseudo first, pseudo second) of phenol adsorption were investigated. Anchote peel (coconia Abysinica peel) was carbonized and activated by treating with KOH solution followed by heating in an electrical furnace at 800 for 2 hrs. Kinetic studies of the data showed that the adsorption follows the pseudo-second-order kinetic model. Thermodynamic parameters showed that adsorption on the surface of APAC was feasible, spontaneous in nature, and exothermic. The equilibrium data better fitted the Freundlich isotherm model. Maximum adsorption efficiencies of Phenol were 97% at optimum pH 6 and optimum contact time 210 min., adsorbent dose 0.25 g and initial conc. 0.025 mg/l respectively. Maximum adsorption capacity of APAC was observed to 43.75 mg/g of Phenol at 25 and 5 mg/L. Key words:

Contrasting effects of a novel biochar-microalgae complex on arsenic and mercury removal

Biochar and algae were commonly used as environmental-friendly adsorbents to treat wastewater contaminated with heavy metals. In the study, we used a biochar-microalgae complex of Coconut shell activated carbon (Csac) and Chlorella to evaluate and compare the adsorption ability of arsenic and mercury. The adsorption kinetic study showed that the adsorption efficiency of the biochar-microalgae complex for mercury was better remarkably than arsenic (about 74.84% higher in initial 1 min and 71.62% higher at adsorption equilibrium), which could be interpreted as the complex had excellent adsorption capacity for mercury. The new biochar-microalgae complex adsorbed up to 46.8 μg·g−1 of mercury at 100 μg·L−1 concentration. FTIR and XPS indicated that the surface of biochar-microalgae complex adsorbent had abundant oxygen-containing functional groups that could provide active sites during the adsorption process, i.e., -COOH, -OH and C-O-C et al. Compared with arsenic, the adsorption peaks of mercury moved or changed significantly, suggesting that the complex strongly adsorbed mercury and the main adsorption mechanisms were the ion exchange and complexation between functional groups and mercury ion. What must be emphasized was arsenic mainly existed as negative ions (AsO2-, AsO23-) in water, which was the reason for the weak adsorption capacity of the biochar-microalgae complex for arsenic. In short, the adsorption efficiency and performance of the biochar-microalgae complex was significantly higher than that of arsenic (p < 0.01), and the adsorption of mercury by biochar-microalgae was chemisorption based on the single molecular layer theory.

Recovery of Cationic Dyes Bearing Wastewater Using Shea Butter Leaves: Kinetic Adsorption, Desorption and Reusability Studies.

Recovery of Cationic Dyes Bearing Wastewater Using Shea Butter Leaves: Kinetic Adsorption, Desorption and Reusability Studies.

Applying MCM-48 mesoporous material, equilibrium, isotherm, and mechanism for the effective adsorption of 4-nitroaniline from wastewater

In this work, the MCM-48 mesoporous material was prepared and characterized to apply it as an active adsorbent for the adsorption of 4-nitroaniline (4-Nitrobenzenamine) from wastewater. The MCM-48 characterizations were specified by implementing various techniques such as; scanning electron microscopy (SEM), Energy dispersive X-ray analysis (EDAX), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area, pore size distribution (PSD), and Fourier transform infrared (FTIR). The batch adsorption results showed that the MCM-48 was very active for the 4-nitroaniline adsorption from wastewater. The adsorption equilibrium results were analyzed by applying isotherms like Langmuir, Freundlich, and Temkin. The maximum experimental uptake according to type I Langmuir adsorption was found to be 90 mg g−1 approximately. The Langmuir model with determination coefficient R2 = 0.9965 is superior than the Freundlich model R2 = 0.99628 and Temkin model R2 = 0.9834. The kinetic adsorption was investigated according to pseudo 1st order, pseudo 2nd order, and Intraparticle diffusion model. The kinetic results demonstrated that the regression coefficients are so high R2 = 0.9949, that mean the pseudo 2nd order hypothesis for the adsorption mechanism process appears to be well-supported. The findings of adsorption isotherms and kinetics studies indicate the adsorption mechanism is a chemisorption and physical adsorption process.

Kinetic and Thermodynamic Study of Methylene Blue Adsorption on TiO2 and ZnO Thin Films.

In this work, we fabricated and characterized ZnO and TiO2 thin films, determining their structural, optical, and morphological properties. Furthermore, we studied the thermodynamics and kinetics of methylene blue (MB) adsorption onto both semiconductors. Characterization techniques were used to verify thin film deposition. The semiconductor oxides reached different removal values, 6.5 mg/g (ZnO) and 10.5 mg/g (TiO2), after 50 min of contact. The pseudo-second-order model was suitable for fitting the adsorption data. ZnO had a greater rate constant (45.4 × 10-3) than that of TiO2 (16.8 × 10-3). The removal of MB by adsorption onto both semiconductors was an endothermic and spontaneous process. Finally, the stability of the thin films showed that both semiconductors maintained their adsorption capacity after five consecutive removal tests.