Adsorption Kinetic Studies Research Articles

Removal of pollutants from landfill leachate by adsorption with nano zero-valent iron particles: adsorption isotherms and kinetic studies

AbstractNano zero-valent iron (nZVI) is an effective adsorbent for removing various organic and inorganic contaminants. In this study, nZVI particles, synthesized in our previous work, were used for landfill leachate pretreatment. The adsorption performance was tested at various adsorbent concentrations (50–500 mg Fe0/L), pH (3–8), and contact times (15–330 min). Chemical oxygen demand, dissolved organic carbon (DOC), nitrate (NO3-), and ammonium (NH4+) removal efficiency were approximately 75%, 60, 57, and 33%, respectively. The obtained data were fitted well by the Langmuir isotherm and adsorption kinetics of pseudo-second-order equations (R2 > 0.9). The adsorption capacities were found to be 29.62, 21.01, and 3.12 mg/g for DOC, NH4+, and NO3−, respectively, at Fe0 concentration of 50 mg Fe0/L, pH of 8, and contact time of 120 min, which was determined as the effective operational conditions in this work. The obtained removal levels were higher compared to the conventional activated carbon adsorption (72.3%). Results suggest that nZVI has the potential to create effective adsorption relevant to landfill leachate pretreatment, thereby providing more efficient biological treatment by decreasing important pollutants before biological treatment.

Plant-based calcium silicate from rice husk ash: A green adsorbent for free fatty acid recovery from waste frying oil

Driven by the urgent need for a solution to tackle the surge of rice husk (RH) and waste frying oil (WFO) waste accumulation at a global scale, this report highlights the use of calcium silicates (CS) extracted from acid-pre-treated rice husk ash (RHA) for free fatty acid (FFA) removal from WFO as conventional RHA shows limited FFA adsorption performance. A novel alkaline earth silicate extraction method from acid-pre-treated RHA was outlined. The structural and behavioural attributes of the synthesised CS were identified through BET, SEM-EDS, and XRD analyses and compared to those of RHA. Notable morphology and structural modification were determined, including reducing specific surface areas, mitigating from amorphous to crystalline structure with regular geometric forms, and detecting Si–O–Ca functional groups exclusive to CS adsorbents. A comparison study showed superior lauric acid (LA) adsorption performance by CS absorbents over acid-pre-treated RHA, with a significant increase from 0.0831 ± 0.0004 mmol LA/g to 2.5808 ± 0.0011 mmol LA/g after 60 min. Recognised as the best-performing CS adsorbent, CS-1.0 was used for further investigations on the effect of dosage, LA concentration, and temperature for efficient LA adsorption, with up to 100% LA removal and 5.6712 ± 0.0016 mmol LA/g adsorption capacity. The adsorption isotherm and kinetic studies showed LA adsorption onto CS-1.0 followed Freundlich isotherm with KF = 0.0598 mmol(1-1/n) L(1/n) g−1 & Qe,cal = 3.1696 mmol g−1 and intraparticle diffusion model with kid = 0.1250 mmol g−1 min0.5 & Ci = 0.9625 mmol g−1, indicating rapid initial adsorption and involvement of carboxylate end of LA and the calcium ions on the CS-1.0 in the rate-limiting step. The high equilibrium adsorption capacity and LA adsorption rate indicated that the proposed CS-1.0 adsorbent has excellent potential to recover FFA from WFO effectively.

Kinetic studies of adsorption on biochar from aqueous solutions

Kinetic studies of adsorption on biochar from aqueous solutions

Smart pillar[5]arene-based PDMAEMA/PES beads for selective dye pollutants removal: design, synthesis, chemical-physical characterization, and adsorption kinetic studies.

This article reports on the synthesis of an innovative smart polymer, P5-QPDMAEMA, opportunely developed with the aim of combining the responsiveness of PDMAEMA polymer and the host-guest properties of covalently linked pillar[5]arenes. Thanks to a traditional Non-Induced Phase Separation (NIPS) process performed at various coagulation pH, the blending of P5-QPDMAEMA with polyethersulfone gave rise to the formation of functional beads for the removal of organic dyes in water. Adsorption tests are carried out on all the produced blend-based beads by employing two representative dyes, the cationic methylene blue (MB), and the anionic methyl orange (MO). In particular, the P5-QPDMAEMA based beads, prepared at acidic pH, featured the best MO removal rate (i. e., 91.3 % after 150 minutes starting from a 20 mg ⋅ L-1 solution) and a high selectivity towards the removal of the selected anionic dye. Based on the adsorption kinetics and isotherm calculations, the pseudo-first order and Freundlich models were shown to be the most suitable to describe the MO adsorption behavior, achieving a maximum adsorption capacity of 21.54 mg ⋅ g-1. Furthermore, zwitterionic beads are obtained by a post-functionalization of the PDMAEMA and the P5-QPDMAEMA based beads, to test their removal capability towards both anionic and cationic dyes, as shown.

Microwave synthesis of amino-functionalized MCM-41 from coal gasification fine slag for efficient bidirectional adsorption of anionic and cationic dyes

Coal based solid waste has been recognized as a sustainable raw material for the preparation of high added value materials for wastewater treatment. In this paper, a preparation route was designed for the rapid, efficient, and low-cost preparation of MCM-41 zeolite using coal gasification fine slag as raw material. Functionalization modification of MCM-41 was carried out by grafting amino groups on its surface to improve its application performance. Moreover, the prepared functionalized material is used for bidirectional adsorption of anionic and cationic dyes. The experimental results indicate that MCM-41 zeolite with highly ordered pore structure was rapidly prepared using the advantages of fast heating and strong permeability of microwave synthesis method, with a specific surface area of up to 862.03 m2/g. Amine functionalized MCM-41 exhibits strong adsorption capacity for both cationic and anionic dyes, with maximum adsorption capacities for methylene blue and Congo red being 292.40 mg/g and 354.61 mg/g, respectively. The study of adsorption kinetics and adsorption mechanism indicate that the adsorption process is mainly controlled through chemical adsorption, including electrostatic attraction, hydrogen bonding, and π-π interactions. The results of this study will provide useful references for the use of coal based solid waste to prepare functional materials for the treatment of organic wastewater.

Adsorption of perfluoroalkyl substances on deep eutectic solvent-based amorphous metal-organic framework: Structure and mechanism

Perfluoroalkyl substances (PFASs) are a class of emerging organic pollutants characterized by high toxicity, environmental persistence, and widespread detection in water sources. The removal of PFASs from water is a matter of global concern, given their detrimental impact on both the environment and public health. Many commonly used PFAS adsorbents demonstrate limited adsorption capacities and/or slow adsorption kinetics. Therefore, there is an urgent need for the development of efficient adsorbents. For the first time, this work systematically investigated the performance of a deep eutectic solvent (DES)-based amorphous metal-organic framework (MOF) for the adsorption of PFASs with different carbon-chain lengths under the state of the mixture in aquatic environments. The adsorption mechanism was probed by a suite of adsorption kinetics studies, adsorption isotherm profiling, spectral characterization, and ab initio molecular dynamics (AIMD) simulations, revealing that PFAS adsorption is driven by synergistic capturing effects including acid/base coordination, CF-π (carbon-fluorine-π), hydrogen bonding, and hydrophobic interactions. Furthermore, the adsorption processes of short-chain and long-chain targets were found to involve different rate-controlling steps and interaction sites. Hydrophobic interactions facilitated the swift arrival of long-chain PFASs at the coordinatively interacting sites between carboxyl termini and Lewis acid Zr unsaturated sites, thanks to their lower reaction barriers. On the other hand, the adsorption of short-chain PFASs primarily relied on a Zr hydroxyl-based ligand exchange force, which would take place at Brønsted acid sites. The existence of massive structural disorder in amorphous UiO-66 led to the development of larger pores, thus improving the accessibility of abundant adsorption sites and facilitating adsorption and diffusion. The presence of multiple types of interactions and flexible structure in defect-rich amorphous UiO-66 significantly increased the exposure of functional groups to the adsorbates. Additionally, this material possessed outstanding regeneration efficiency and outperformed other MOF-based adsorbents with high affinity for targets. It enhances our understanding of the adsorption performances and mechanisms of amorphous materials toward PFASs, thereby paving the way for designing more efficient PFAS adsorbents.

Analysis of the adsorption mechanism of phosphoric acid-modified bamboo charcoal for chlorogenic acid based on density functional theory

BackgroundBamboo charcoal has garnered wide recognition as an adsorbent owing to its stability and availability. Phosphoric acid modification contributes to forming specific functional groups on the surface of bamboo charcoal, culminating in the augmentation of its adsorption capabilities.ResultsThe modification process in this study involved impregnating the bamboo charcoal in a 45% mass fraction of phosphoric acid solution with a 1:10 ratio (bamboo charcoal powder to phosphoric acid), followed by activation at a temperature of 500 °C for a duration of 1.5 h. The modification resulted in the formation of hydroxyl, carboxyl, and phosphate groups on the surface of the bamboo charcoal. Furthermore, the specific surface area of the modified bamboo charcoal surged from 4.91 m2/g to 115.18 m2/g, the average aperture decreased from 7.15 nm to 1.99 nm, and the pore volume escalated by 6.5 times. On this basis, a comparison in the adsorption capability for chlorogenic acid, a natural small-molecule active ingredient, was drawn before and after the modification of bamboo charcoal. The results indicate that the modified bamboo charcoal showcases an impressive 46.8-fold increase in its adsorption capacity when juxtaposed with the unmodified bamboo charcoal. Through the calculations based on density functional theory (DFT), the addition of functional groups on the surface of the modified bamboo charcoal module allows for the formation of hydrogen bonds with the chlorogenic acid module, with the highest binding energy reaching − 57.59 kJ/mol.ConclusionAs evidenced by the adsorption kinetic studies, the curve of modified bamboo charcoal for chlorogenic acid abides by a first-order kinetic equation. Additionally, adsorption thermodynamic studies reveal that the curve of modified bamboo charcoal for chlorogenic acid conforms to the Boltzmann equation. These results shed light on the mechanism of selectively adsorbing specific constituents using phosphoric acid-modified bamboo charcoal, thereby providing a solid theoretical foundation for the application of bamboo charcoal.Graphical

Adsorption Isotherms and Kinetics Studies on Adsorption of Malachite Green onto Activated Charcoal from Aqueous Solution

The article presents low-cost activated charcoal as an adsorbent in the adsorption process for the removal of malachite green from aqueous solution by batch process. To find the optimum condition of the process, contact time, shaking rate, concentration of malachite green, and concentration of activated charcoal were examined. The malachite green was removed up to 98.9%. The adsorption isotherms were studied to check the performance of the adsorbent. Langmuir, Freundlich, Temkin, Hill De Boer, and Dubinin-Radushkevich adsorption isotherms were studied and compared to which one was suitable in the process. The adsorption process with the activated charcoal adsorbent followed suitably with the order of the Dubinin-Radushkevich > Langmuir > Hill De Boer> Temkin > Freundlich models. According to a kinetic study, the adsorption process was second order. In thermodynamic studies, we obtained negative values of ΔG, ΔS, and ΔH. The negative ΔH and ΔS values suggest that enthalpy contributes more than entropy in producing negative ΔG values. The negative ΔG values of malachite green adsorptions indicate that is a favorable and spontaneous process. The negative value of ΔH ensures the adsorption process is characterized as chemical adsorption and exothermic. The negative ΔS value indicates that randomness decreases at the solid–solution interface during the adsorption of MG by activated charcoal. The surface morphology of the Activated charcoal ensured the adsorption process. The results indicate that the adsorption process is exothermic, spontaneous, and favorable. So, activated charcoal might be useful for removing the malachite green dye from the aqueous solution.

Activated Carbons as Effective Adsorbents of Non-Steroidal Anti-Inflammatory Drugs

In this study, the adsorption of naproxen sodium, ibuprofen sodium, and diclofenac sodium on activated carbon is investigated. Comprehensive studies of adsorption equilibrium and kinetics were performed using UV-Vis spectrophotometry. Thermal analysis and zeta potential measurements were also performed for pure activated carbon and hybrid materials (activated carbon–drug) obtained after adsorption of naproxen sodium, ibuprofen sodium, and diclofenac sodium. The largest amount and rate of adsorption was demonstrated for naproxen sodium. A significant impact of temperature on the adsorption of the tested salts of non-steroidal anti-inflammatory drugs was also indicated. Faster kinetics and larger amounts of adsorption were recorded at higher temperatures. Thermodynamic parameters were also determined, based on which it was indicated that adsorption in the tested experimental systems is an endothermic, spontaneous, and thermodynamically privileged process of a physical nature. The generalized Langmuir isotherm was used to study the equilibrium data. The adsorption rate data were analyzed using numerous adsorption kinetics equations, including FOE, SOE, MOE, f-FOE-, f-SOE, f-MOE, and m-exp.

Mathematical modeling by fractional calculus applied to separation processes

Process modeling is a way of representing real problems through equations and while the traditional models of mass and heat transfer processes consider the transient term as a first-order derivative, fractional order modeling is applied to verify that the order of the derivative of the transient term would not be represented by a non-integer number. In this context, the objective of this work was to apply fractional calculus to the kinetics study of adsorption and extraction processes and compare the results obtained with traditional models. The Caputo derivative was used to solve the proposed equations, and the analyzed processes were the adsorption of glycerol for biodiesel at different temperatures and the solid–liquid extraction of antioxidant compounds from corn for different proportions of solvent. For the adsorption, the fractional order model was compared with the pseudo-first, pseudo-second, and first-order models, and the fractional order model represented adsorption satisfactorily, with method efficiencies of 0.9603 and 0.9433 for the temperatures of 45 °C and 60 °C, respectively, while the performance of traditional models depends on the mechanisms that control the process. In addition, the α values obtained with the fractional order model were less than 1, indicating that glycerol adsorption does not follow an integer order derivative and implies that the adsorption exhibits a level of complexity that is not fully characterized by traditional models. The extraction of antioxidant compounds was analyzed and compared with the first-order and So and MacDonald’s models. It was verified that the derivative order values for the fractional order model were close to 1 and, therefore, the behavior is similar to the first order model and with indications that diffusion occurs as described by Fick’s law of diffusion. Thus, the results indicated that fractional order modeling can be used efficiently to describe chemical engineering processes such as adsorption and extraction.

Activated rice husk biochar for azo dye removal: batch adsorption, kinetics and thermodynamic studies

<p>The study aimed to analyze the adsorption behaviour of an activated rice husk biochar adsorbent in batch mode to expunge azo dye concentrations depletion from liquid solvents. The biochar adsorbent was formulated using different chemical synthesis processes, and its surface region was assessed using Nitrogen retention. The existence of the particular azo dyes was verified through SEM and EDX examinations. Additionally, XRD analysis was conducted to examine the intensity and crystalline structure of the activated biochar adsorbent. A batch mode study was conducted to ascertain the ideal adsorption parameters, including pH, contact time, biochar dose, and azo dye concentration. The adsorption kinetic studies supported the notion of a favourable adsorption interaction occurring through the mutual influence of the adsorbed matter and the adsorbing substrate. Most isotherm studies were well-fitted with regression values of isotherm models, indicating an adsorption process with non-uniform monolayer formation. Thermodynamic investigations validated that the binding forces between the adsorptive and the adsorbing phase are endothermic, and a significant amount of spent adsorbent was successfully recovered using a strong hydrochloric acid desorption process.</p>

Nylon fiber waste as a prominent adsorbent for Congo red dye removal

In this research nylon fibers wastes (NF) were fabricated into porous sheet using a phase inversion technique to be utilized as an adsorbent materials for Congo red dye (CR). The fabricated sheet denoted as NS was characterized using FTIR and XRD. The surface studies of the adsorbent materials using SEM and BET analysis reveals a highly pores structure with an average pore volume 0.61 cc/g and BET surface area of 767 m2/g. The adsorption studies of fabricated NS were employed into CR at different parameters as pH, effect of time and dye concentration. The adsorption isotherm and kinetic studies were more fit to Langmuir and pseudo second order models. The maximum adsorption capacity qmax reached 188 mg/g with removal percentage of 95 for CR concentration of 400 mg/L at pH 6 and 0.025 g NS dose for 10 ml CR solution. The regeneration study reveals a prominent adsorption behavior of NS with removal % of 88.6 for CR (300 mg/L) after four adsorption desorption cycles. Effect of incorporation of NaonFil Clay to NS was studied using Response Surface Methodology (RSM) modeling and reveals that 98.4% removal of CR could be achieved by using 19.35% wt. of fiber with 8.2 g/L dose and zero clay, thus at a predetermined parameters studies of NanoFil clay embedded into NS, there are no significant effect for %R for CR.

Synergistic effects of adsorption and chemical reduction towards the effective Cr(VI) removal in the presence of the sulfur-doped biochar material.

In this study, the anaerobic sludge withdrawn from thickener in a sewage treatment plant served as the precursor for sludge-based biochar fabrication, which was further modified via sulfur (S) heteroatom doping (i.e., S-BC). The S atom doping resulted in the adjustment of the physicochemical properties towards the carbon material, endowment of abundant functional groups on biochar surface, and increasing the binding sites between biochar and Cr(VI). Compared to the primary biochar (i.e., biochar without heteroatomic doping, named BC), S-BC exhibited a rough surface and possessed remarkable advantages in ash content, specific surface area, and pore volume. The existence of graphene carbon crystal structure for S-BC was confirmed through S-BC by XRD and FTIR analysis. The studies of adsorption kinetics and isotherms showed that pseudo-second-order kinetics and the Langmuir model more fitted the Cr(VI) removal behavior in the presence of S-BC. Therefore, the chemisorption and monolayer adsorption were the primary mechanisms involved in the Cr(VI) removal process. Additionally, XPS analysis results illustrated the aqueous Cr(VI) was efficiently eliminated through the synergistic effect of chemisorption and reduction to Cr(III) in the presence of S-BC. Moreover, S-BC could still achieve the Cr(VI) eliminating efficiency of 85.31% undergoing five cycles with unchanged functional group and crystal structure via FTIR and XRD analysis. Thus, the results of this study may shed light on a new approach for simultaneous economical sludge disposal and the sustainable remediation of the Cr(VI)-contaminated wastewater.

Promising and Environmentally Friendly Removal of Copper, Zinc, Cadmium, and Lead from Wastewater Using Modified Shrimp-Based Chitosan

This study explores the potential of modified shrimp-based chitosan (MSC) as an innovative adsorbent for eliminating heavy metals (HMs) from contaminated water sources. The modifications encompassed various chemical treatments, surface functionalization, and structural optimization to enhance the chitosan’s adsorption capabilities. Comprehensive analyses using FT-IR and SEM-EDS were conducted to evaluate the properties of the chitosan. The adsorption capacity of MSC was assessed using ICP-MS before and after the adsorption process. Moreover, the study investigated the efficiency of HM removal by MSC under different conditions, including variations in pH, adsorbent dosage, and contact time. Under neutral pH conditions, the highest adsorption rates of copper, zinc, cadmium, and lead were determined as 99.72%, 84.74%, 91.35%, and 99.92%, respectively, with corresponding adsorption capacities of 20.30 mg/g for copper, 7.50 mg/g for zinc, 15.00 mg/g for cadmium, and 76.34 mg/g for lead. Analysis based on the Langmuir and Freundlich isotherm models revealed highly significant adsorption of HMs, supported by strong correlation coefficients (r2 > 0.98) obtained from the data. The pseudo-second-order kinetic model with linear coefficients (r2) greater than 0.97 effectively explained the kinetic studies of metal adsorption employing modified shrimp shells. These coefficients indicate a robust fit of the models to the experimental adsorption data for heavy metals. Further confirmation of the effectiveness of the adsorbent was obtained through FT-IR spectroscopy, which confirmed the presence of specific functional groups on the adsorbent, such as N–H joined with –COO−, H–O, C−O−C, and C–H. Additionally, the SEM-EDS analysis detected the presence of elements on the surface of MSC chitosan. The results emphasize that MSC is a highly effective and cost-efficient adsorbent for eliminating Cu, Zn, Cd, and Pb from wastewater, making it a promising eco-friendly choice.

The performance of an eco-friendly adsorbent for methylene blue removal from aqueous solution: Kinetic, isotherm, and thermodynamic approaches

The current study aims to determine how well pomegranate peel can remove Methylene Blue (MB) from an aqueous solution. For this purpose, kinetic, isotherm, and thermodynamic adsorption studies were performed in a batch system. The rate of MB adsorption was rapid and reached equilibrium at about 60 minutes. The adsorption capacity reached approximately 42.71 mg g-1 at the initial dye concentration of 100 mg L-1. The kinetic modeling of MB adsorption was conducted using pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models. The pseudo-second-order model was found to be the most adequate for fitting the kinetic data based on R2, RMSE, ARE, and ?2 values. It was also discovered that MB adsorption onto pomegranate peel is not simply rate-limited by intraparticle diffusion. The isotherm approach showed a maximum adsorption capacity of 67.78 mg g-1 at 298 K using 2 g L-1 of pomegranate peel. Equilibrium modeling was also conducted. The four statistical values highlighted the better fit of the Langmuir model than the Freundlich model. Additionally, the exothermic and spontaneous nature of the adsorption process was revealed by thermodynamic research. These findings demonstrate the effectiveness of pomegranate peel as an eco-friendly absorbent for MB removal.

DRIED FRUIT POWDER OF NEEM (Azadirachta Indica) FOR REMOVAL OF LEAD IONS FROM AQUEOUS SOLUTION BY ADSORPTION

In the present study, Dried fruit powder of neem (Azadirachta indica) was used for the removal of lead ions from an aqueous solution by adsorption. The batch experiments were conducted for biosorption of Pb (II) on biosorbent by altering the various parameters, including pH—dose of biosorbents, concentration of metal ions solution, and contact time. The surface area, functionality, surface morphology, and elemental analysis of biosorbent were analyzed by Brunauer-Emmett-Teller, Fourier Transform Infrared Spectroscopy, and Field emission scanning electron microscopy with Energy-dispersive X-ray respectively. The adsorption isotherm models and kinetics study were done. The Neem (Azadirachta indica) fruit biosorbent exhibited the ability to remove 70% of Pb (II) from the aqueous solution with 20 mg/L of lead at a biosorbent dose of 2g/L. the study observed that removal efficiency increased as contact time increased, reaching saturation in approximately 90 minutes at optimum pH ~ 5. The best-fit models for the biosorption of heavy metal ions were pseudo-second-order kinetics and Langmuir adsorption isotherm, with a maximum adsorption capacity of 14.71 mg/g. The thermodynamic analysis indicated that the adsorption of these heavy metal ions was a spontaneous and endothermic process. The research indicates that neem (Azadirachta indica) fruit has the potential to be extensively studied as a highly effective biosorbent for removing metal ions from aqueous solution.

A resins-neutralization coupled route for the treatment of stainless-steel pickling effluent: A research study

One of the major environmental problems caused by stainless-steel industries is the liquid effluents generated during the production processes. It contains a high concentration of metal ions such as Fe (III), Cr (III), Cr (VI), and Ni (II) in HF and HNO3 mixture, oil, and rinse wastewater. The used pickling waste stream has a pH of 0.5 and Total Dissolved Salts (TDS) of 520g/L with a density of 1.20g/CC. The present work focused on recycling pickling effluent by combining filtration, resins, and neutralization to remove metal ions efficiently and F- greater than 99.5%. To remove TDS, laboratory experiments were performed using micro and ultra-filters with a membrane area 0.2m2. Cr (VI) was removed using TulsionFSMP 6301 resin and desorption using NaNO3 and subsequent conversion into Na2Cr2O7 as a by-product. For neutralization, Ca(OH)2 and NaOH were used to precipitate metal ions, and the resulting filtrate was polished using ZrOCl2 to remove F- to 0.12 mg/L effectively. The nitrate was recovered as NaNO3. Adsorption isotherm and kinetic studies were utilized for Cr (VI) from experimental data, and a process flow diagram was developed, which can eventually be tested on a larger scale.

PH-Dependent selective extraction of gold(iii) from synthetic solution and computer motherboard leachate using a hybrid nanocomposite.

Recycling gold from electronic waste offers significant benefits for both environmental protection and resource sustainability. However, this process presents considerable challenges due to high costs, prolonged processing times, and interference from coexisting metals. In this study, we synthesized a hybrid mesoporous nanocomposite comprising platelets-like CoNi2S4 incorporated with g-C3N4 nanosheets (CoNi2S4@g-C3N4) for the selective recovery of gold (Au(iii)) ions from spent computer motherboards. Comprehensive characterization of the CoNi2S4@g-C3N4 nanocomposite was conducted, including its physicochemical properties, textural and structural characteristics, morphology, and elemental composition. The CoNi2S4@g-C3N4 extractor demonstrated an exceptional adsorption capacity of 200.6 mg g-1, with high selectivity at pH 2, rapid equilibrium time of 60 minutes, and satisfactory reusability for over ten cycles. Adsorption isotherm and kinetic studies revealed that the CoNi2S4@g-C3N4 nanocomposite adheres to the Langmuir adsorption model and the pseudo-second-order kinetic model for Au(iii) ion adsorption. Overall, this study introduces a viable adsorbent that shows considerable promise for industrial-scale Au(iii) extraction from e-waste.

Enhanced adsorption of carbon sphere by doping with titania nanotubes for crystal violet removal: isotherm, kinetics, and thermodynamic studies.

In this study, the carbon sphere (Cs) has been prepared and modified by titania nanotubes (TNTs) to be utilized as an adsorbent toward crystal violet (CV) dye as a model for cationic dyes from aqueous solution. The prepared TNTs@Cs composites has been characterized by various techniques such as XRD, SEM, and TEM analysis. The adsorption analysis displayed that the adsorption capacity of CV dye onto the modified Cs with TNTs is 92.5 mg g-1, which is much higher than that achieved by pristine Cs (12.5 mg g-1). Various factors that influence the overall adsorption processes, such as pH, contact time, initial CV dye concentration, adsorbent weight, and temperature, were studied. The TNTs@Cs76.7 composite showed the highest removal percentage of 99.00% at optimum conditions. The adsorption isotherm analysis showed that the experimental data of adsorption CV dye fitted better with the Langmuir isotherm model with R 2 of 0.999, and the estimated maximum adsorption capacity was 84.7 mg g-1. On the other hand, the adsorption kinetic study showed that the adsorption of CV follows the pseudo-second order kinetic model with an equilibrium adsorption capacity (q e) of 10.66, 18.622, 47.61, and 48.31 mg g-1 for Cs, TNTs@Cs93, TNTs@Cs86.8, and TNTs@Cs76.7 composites, respectively. The thermodynamic analysis showed negative free energy (ΔG) values, this indicates that the adsorption of CV is a spontaneous and feasible process. Furthermore, the ΔH and ΔS are positive values that indicate an endothermic adsorption process. Furthermore, the prepared TNTs@Cs76.7 composite displayed remarkable adsorption stability and the removal efficiency of CV remains at 96.3% after five cycles.

Precise evaluation of batch adsorption kinetics of plant total polyphenols based on a flow-injection online spectrophotometric method.

Efficient evaluation of adsorption kinetics of plant total polyphenols is essential for the design of adsorption separation of bioactive compounds. The conventional method uses manual sampling with poor reproducibility. Here, we developed a new method for on-line determination of total polyphenol content (TPC) in plant extracts by applying the Folin-Ciocalteu method in flow-injection analysis (FIA). The FIA parameters were optimized and a standard curve with excellent linearity was established. Precise determination of TPC with a satisfactory sample throughput of 20 h-1 was achieved for the adsorption kinetic study. The pseudo-second-order kinetic model was found to better describe the kinetic parameters of the batch adsorption/desorption process. The developed method proved to be accurate compared with the conventional method. The FIA method holds significant promise for studying and monitoring adsorption processes, due to its automatic on-line nature, low consumption of reagents and samples, and the ability to generate large quantities of highly accurate adsorption data.