Film Diffusion Model Research Articles

Biodiesel Production Using Palm Oil with a MOF-Lipase B Biocatalyst from Candida Antarctica: A Kinetic and Thermodynamic Study

This research presents the results of the immobilization of Candida Antarctica Lipase B (CALB) on MOF-199 and ZIF-8 and its use in the production of biodiesel through the transesterification reaction using African Palm Oil (APO). The results show that the highest adsorption capacity, the 26.9 mg·g−1 Lipase, was achieved using ZIF-8 at 45 °C and an initial protein concentration of 1.20 mg·mL−1. The results obtained for the adsorption equilibrium studies allow us to infer that CALB was physically adsorbed on ZIF-8 while chemically adsorbed with MOF-199. It was determined that the adsorption between Lipase and the MOFs under study better fit the Sips isotherm model. The results of the kinetic studies show that adsorption kinetics follow the Elovich model for the two synthesized biocatalysts. This research shows that under the experimental conditions in which the studies were carried out, the adsorption processes are a function of the intraparticle and film diffusion models. According to the results, the prepared biocatalysts showed a high efficiency in the transesterification reaction to produce biodiesel, with methanol as a co-solvent medium. In this work, the catalytic studies for the imidazolate, ZIF-8, presented more catalytic activity when used with CALB. This system presented 95% biodiesel conversion, while the biocatalyst formed by MOF-199 and CALB generated a catalytic conversion percentage of 90%. Although both percentages are high, it should be noted that CALB-MOF-199 presented better reusability, which is due to chemical interactions.

Biochar‐C‐TETA as a superior adsorbent to acid yellow 17 dye from water: isothermal and kinetic studies

AbstractAdsorbents from local materials with high adsorption capacity (Qm) are strongly needed. In this study, mandarin peels (MP) as a local waste material were refluxed in 80% sulfuric acid (H2SO4) to produce a novel biochar, which was oxidized by boiling in 50% hydrogen perioxide (H2O2) and then aminated via refluxing in tetraacetic acid (TETA) to produce mandarin biochar‐C‐TETA (MBCT). Fourier transform infrared (FTIR), Brunauer–Emmett–Teller (BET), Barrett–Joyner–Halenda (BJH), scanning electron microscopy (SEM), energy‐dispersive X‐ray (EDX), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS) and thermgravimetric analysis (TGA) studied various characterizations of MBCT. The optimal pH for AY17 dye absorption was discovered to be 1.5 using 0.75 g L−1 MBCT, the maximum absorption capacity predicted for the MBCT was 1250 mg g−1. The high new absorption peaks at 1439.89 and 1362.38 cm−1 in MBCT imply that amino groups were successfully generated onto the surface of MBCT due to TETA treatment. The experimental data were examined using the Langmuir (LNR) and Freundlich (FRH) isotherm models. The FRH best explained the experimental MBCT data. The pseudo‐first‐order (PFOM) and pseudo‐second‐order (PSOM) models, intraparticle diffusion (INDM) and film diffusion (FDM) models were applied to calculate the kinetic data. The PFOM rate model ideally defined the absorption of AY17 dye to MBCT with a linear regression coefficient (R2 > 0.99). The key mechanism for absorbing AY17 dye molecules to MBCT was chemisorption, which entails the distribution or exchange of electrons between the absorbent and the dye due to the valency force. According to the findings, the novel MBCT adsorbent had a remarkable adsorption capacity (Qm = 1250 mg g−1) and could be reused without losing its absorption effectiveness. © 2023 Society of Chemical Industry (SCI).

Adsorption of BEZAKTIV BLAU V3-R and BEZAKTIV BLAU S-2R reactive dyes onto rice husk modified by the circular economy concept

Rice husk, modified with effluent from the alkaline scouring of cotton, employing an inexpensive treatment based on the circular economy concept, is used as a bio-sorbent to study the equilibrium and kinetic on cold brand BEZAKTIV BLAU V3-R (BBV3-R) and medium brand BEZAKTIV BLAU S-2R (BBS2-R) reactive dyes. 10, 20, and 40 g L−1 rice husk is used to follow adsorption of 0.1, 0.2, 0.3, 0.4, and 0.5 g L−1 BBV3-R and BBS2-R in a presence of 60 g L−1 NaCl at pH 10, at the temperature of 25 °C and 40 °C, respectively. Langmuir, Freundlich, and Dubinin-Radushkevic's adsorption models were employed, with the Freundlich model proving the best fit for our data. Activation energy calculated with the Dubinin–Radushkevic model (lower than 8 kJ mol−1) confirms the physical sorption of these reactive dyes onto the husk. The obtained maximum experimental absorption capacities of 122.2 mg g−1 for BBV3-R and 171.7 mg g−1 for BBS2-R using 10 g L−1 ERH are the best found in the literature. Pseudo-second-order model determines the adsorption kinetics, while the liquid film diffusion model is rate-determining. This paper demonstrates the applicability of the circular economy concept to obtain an efficient adsorbent for purifying colored effluent enriched with reactive dyes, which are one of the most challenging dyes in the textile industry from the aspect of their effluent purifying.

Interaction behaviors of sulfamethoxazole and microplastics in marine condition: Focusing on the synergistic effects of salinity and temperature

Microplastics and antibiotics are two common pollutants in the ocean. However, due to changes of salinity and temperature in the ocean, their interaction are significantly different from that of fresh water, and the mechanism remains unclear. Here, the interactions of sulfamethoxazole (SMZ) and microplastics were studied at different temperatures and salinities. The saturation adsorption capacity of SMZ in polypropylene (PP), polyethylene (PE), styrene (PS), polyvinyl chloride (PVC), and synthetic resins (ABS) were highest at the temperature of 20 °C, with 0.118 ± 0.002 mg·g−1, 0.106 ± 0.004 mg·g−1, 0.083 ± 0.002 mg·g−1, 0.062 ± 0.007 mg·g−1 and 0.056 ± 0.003 mg·g−1, respectively. The effect of temperature reduction is more significant than temperature rise. The intraparticle diffusion model is appropriate to PP, when film diffusion model suited for PS. The salinity has a more significant effect than temperature on different microplastics, due to the electrostatic adsorption and iron exchange. With the increase in salinity from 0.05% to 3.5%, the adsorption capacity of microplastics on SMZ fell by 53.3 ± 5%, and there was no discernible difference of various microplastics. The hydrogen bond and π-π conjugation of microplastics play an important role in the adsorption of SMZ. These findings further deepen the understanding of the interaction between microplastics and antibiotics in the marine environment.

Potassium Hydroxide Activation as an Adsorbent for Kinetic Models of Hexavalent Chromium Adsorptions onto <i>Garcinia mangosteen</i> Shell

The utilized adsorption kinetic models, i.e., pseudo-zero order, pseudo-first-order, pseudo-second order, intraparticle diffusion, Bangham’s pore diffusion, liquid film diffusion, modified Freundlich and Elovich models have been cultivated the hexavalent chromium adsorption process. A high correlation coefficient (R2) and a small residual root mean square error (RMSE) and Chi-square (χ2) can be depicted in the pseudo-first order for the kinetic adsorption process of hexavalent chromium adsorption on the activated mangosteen shell with potassium hydroxide and carbonized at 400 °C for 2 h as a biochar adsorbent which has a specific surface area of 164 m2/g.

Adsorption Kinetics of Methyl Orange from Model Polluted Water onto N-Doped Activated Carbons Prepared from N-Containing Polymers.

This study aimed to assess the role of polymeric sources (polypyrrole, polyaniline, and their copolymer) of nitrogen (N)-doped activated carbons (indexed as PAnAC, PPyAC, and PnyAC, respectively) on their adsorption efficiency to remove methyl orange (MO) as a model cationic dye. The adsorbents were characterized using FTIR, SEM, TGA, elemental analysis, and surface area. The kinetic experiments were performed in batches at different MO concentrations (C0) and adsorbent dosages. The adsorption kinetic profiles of pseudo-first-order, pseudo-second-order (PSO), Elovich, intraparticle diffusion, and liquid film diffusion models were compared. The results showed a better fit to the PSO model, suggesting a chemisorption process. The adsorption capacity (qe, mg/g) was found to have increased as MO C0 increased, yet decreased as the adsorbent quantity increased. At the adsorption operating condition, including MO C0 (200 ppm) and adsorbent dose (40 mg), the calculated qe values were in the order of PAnAC (405 mg/g) > PPyAC (204 mg/g) > PnyAC (182 mg/g). This trend proved the carbon precursor's importance in the final properties of the intended carbons; elemental analysis confirmed that the more nitrogen atoms are in the activated carbon, the greater the number of active sites in the adsorbent for accommodating adsorbates. The diffusion mechanism also assumed a rate-limiting step controlled by the film and intraparticle diffusion. Therefore, such an efficient performance may support the target route's usefulness in converting nitrogenous-species waste into valuable materials.

Adsorption behavior of Crys tal Violet dye in aqueous solution using Co+2 hectorite composite as adsorbent surface

This study focused on the adsorption behavior of the cationic CrystalViolet (CV) dye from aqueous solutions using a Co+2‒hectoritecomposite as an adsorbent surface. The initial and equilibrium CV dyeconcentrations were determined using a UV-Vis spectrophotometer. Theresults were discussed and presented for the impacts of pH, primary CVdye concentration, composite dosage, and temperature. The optimumconditions were found for eliminating Crys tal Violet dye from theaqueous solution at a pH 4, ideal temperature 293 K, and 0.5 g L-1of composite dose. The pseudo-second-order kinetic, intraparticlediffusion analyzed the tes ts’ data and film diffusion models. Eachmodel’s defining features have been identified, and these models werein good agreement and in charge of regulating the adsorption reaction.The adsorption operation was also thermodynamically examined todetermine thermodynamic variables such as Gibbs free energy (ΔGo),entropy (ΔSo), activation energy (Ea), and enthalpy (ΔHo). The negativevalue of Gibbs free energy (ΔGo) and enthalpy (ΔHo) indicated thatthe adsorption process was a spontaneous and exothermic reaction.While the activation energy (Ea) data which fell within the normalrange for physisorption, was showed at 22.434 kJ mol-1. The physical adsorption occurs between CV dye and adsorbent .

Isotherm and kinetic studies of acid yellow 11 dye adsorption from wastewater using Pisum Sativum peels microporous activated carbon

In this study, Pea Peels-Activated Carbon (PPAC), a novel biochar, was created from leftover pea peels (Pisum sativum) by wet impregnation with ZnCl2 and subsequent heating to 600, 700, and 800 °C in a CO2 atmosphere. Investigated how the newly acquired biochar affected the capacity to extract the AY11 dye from the aqueous solution. Through the use of FTIR, XRD, SEM, BJH, BET, DSC, EDX, and TGA studies, the prepared PPAC was identified. It was found that a pH of 2 is optimum for the AY11 dye elimination. The highest removal percentage of AY11 dye was 99.10% using a beginning AY11 dye concentration of 100 mg/L and a 1.0 g/L dose of PPAC. The highest adsorption capacity (Qm) of the PPAC was 515.46 mg/g. Freundlich (FIM), Halsey (HIM), Langmuir (LIM), Tempkin (TIM), and Gineralize (GIM) isotherm models were useful in examining the adsorption results. A variety of error functions, including the average percent errors (APE), root mean square errors (RMS), Marquardt's percent standard deviation (MPSD), hybrid error function (HYBRID), Chi-square error (X2) and a sum of absolute errors (EABS) equations, were also applied to test the isotherm models data. The PPAC experimental data were best suited by the HIM and FIM isotherm models. Elovich (EM), Pseudo-first-order (PFOM), Intraparticle diffusion (IPDM), Pseudo-second-order (PSOM), and Film diffusion (FDM) models were applied to study the kinetic adsorption results. The PSOM had a strong correlation coefficient (R2 > 0.99), and it was principally responsible for controlling the adsorption rate. Anions are typically absorbed during the adsorption mechanism of AY11 dye by PPAC owing to attractive electrostatic forces created with an increase in positively charged areas at acidic pH levels. The regenerated PPAC was used in six successive adsorption/desorption cycles. This study's outcomes show that PPAC successfully removes the AY11 dye from the aqueous solution; as a result, PPAC can be used repeatedly without experiencing considerable loss in effectiveness.

Synthesis, Characterization and Application of a MIP-polyHIPE for Selective Extraction of Angiotensin II Receptor Antagonists Residues in Natural Waters.

Polymers via high internal phase emulsion (polyHIPEs) were molecularly imprinted with Irbesartan, an antihypertensive drug belonging to the class of angiotensin II receptor antagonists (sartan drugs), chosen for the proof-of-concept extraction of hazardous emerging contaminants from water. Different analyte-functional monomer molar ratios (1:100, 1:30 and 1:15) were investigated, and the MIP polyHIPEs have been characterized, parallel to the not imprinted polymer (NIP), by batch sorption experiments. The material with the highest template-functional monomer ratio was the best for Irbesartan removal, showing a sorption capacity fivefold higher than the NIP. Regarding the adsorption kinetics, the analyte-sorbent equilibrium was reached after about 3 h, and the film diffusion model best fitted the kinetic profile. Selectivity was further demonstrated by testing Losartan, another sartan drug, observing a fourfold lower sorption capacity, but still higher than that of NIP. The polymers were also synthesized in cartridges for solid-phase extraction (SPE), which was helpful for evaluating the breakthrough curves and performing pre-concentrations. These have been done in tap and river water samples (100-250 mL, 15-500 µg L-1 Irbesartan), obtaining quantitative sorption/desorption on the MIP-polyHIPE (RSD < 14%, n = 3). The NIP provided a recovery of just around 30%, evidence of partial uptake of the target from water.

Ficus Benjamin's leaf, a native sorbent for the exclusion of Methyl violet 10B from aquatic media

Due to the use of non-recyclable materials and the high costs of the technologies, removal of dyes from wastewater is becoming more and more pricey. This paper presents the capacity of Ficus Benjamina (FB) leaf powder to eradicate methyl violet dye 10 B (MV) in an aqueous fluid. The surface characteristics and presence of various functional groups on the surface of sorbent were revealed by SEM and FTIR studies. Diverse constraints on the elimination of methyl violet 10 B in an aqueous environment were also studied, including starting dye concentration, temperature, and contact duration. The Elovich & liquid film diffusion models, along with Lagergren first-order, pseudo-second-order, Bangham, and modified Freundlich modeling operated to assess kinetics. Experiments confirmed the pseudo-second-order concept. To investigate tentative data, multiple linear Langmuir, Freundlich, Temkin, as well as two parameters nonlinear isotherm models were applied, with findings indicating that sorption data were like both linear and non-linear isotherms. Sorption data were found to be in excellent agreement with the Freundlich isotherm with R2 value (0.99). The sorption capacity of the sorbent was computed i.e. 312.2 mg/g. Thermodynamic characteristics were also computed. It was concluded that the sorption of methyl violet 10 B sorption on FB leaf powder is exothermic. Hence, it is a potentially cost-effective bio sorbent for exclusion of dye from wastewater.

Achieving win-win outcomes with cerium-loaded porous aluminum sludge hydrogel microspheres for enhanced phosphate removal

Breaking the technical bottleneck of traditional powdered adsorbent in phosphate adsorption application treatment, a macroscopic high adsorption performance aluminum sludge-based composite hydrogel material was constructed to synergistically solve the problems of water eutrophication and aluminum sludge resourcization. In this study, porous Ce-modified aluminum sludge hydrogel microspheres (Ce-AlS-SA) were prepared to improve the surface chemical structure and microscopic morphology of the macroscopic adsorbent material to enhance the adsorption capacity and achieve effective solid-liquid separation. The best adsorption performance of the material (Ce-AlS12-SA1) was obtained when the Ce-AlS: SA: Na2CO3 was 12:1:1, and obtained the optimal adsorption conditions by Response Surface Method (RSM) with 1.5 mg/L of the dosage, 4 of pH and 50 mg/L of Cphosphate. The maximum adsorption of 20.36 mg P/g was obtained by the Langmuir model at 303 K, which was 2.92 times more than raw sludge. According to the Freundlich and pseudo-second-order kinetic model, the adsorption process is chemisorption; the multi-stage adsorption process is reflected in the intraparticle diffusion and film diffusion models. The main mechanisms combined with the characterization analysis are electrostatic gravity, ligand exchange, and inner-sphere complexation. Meanwhile, Ce-AlS12-SA1 shows good resistance to interference in the coexistence of multiple ions. Therefore, this material can be recognized as a new material with in-depth, diversified and practical needs for resourceful utilization, which is expected to achieve extensive engineering applications in the future.

Adsorption and immobilization of phosphorus from eutrophic seawater and sediment using attapulgite - Behavior and mechanism

The adsorption behavior of phosphorus on raw sediment (RS), attapulgite (AT), purified attapulgite (PAT) and AT/PAT-amended sediments conforms to the Langmuir, pseudo first-order kinetics and liquid film diffusion model. The adsorption process is spontaneous and monolayer adsorption, and the adsorption rate is mainly controlled by liquid film diffusion. The addition of attapulgite improved the adsorption capacity of phosphorus in the sediments of mariculture ponds. The results of long-term sediment core incubation showed that the average reduction rates of total phosphorus (TP) and soluble reactive phosphorus (SRP) in overlying water and SRP in pore water by adding 20% purified attapulgite (S/PAT20) were 62.11%, 70.83% and 56.32% respectively, and the phosphorus flux in sediments decreased by 53.81%. The addition of attapulgite reduces the risk of phosphorus release in sediments, and changes sediments from “source” to “pool”. The specific surface area and pore volume of PAT increased to 203.254 cm2/g and 0.395 cm3/g respectively, but the phosphorus adsorption capacity was only increased by 2 times compared with AT (1431.3–2671.8 mg P/kg), indicating that the changes of mineral structure and chemical composition jointly determine the phosphorus adsorption effect. Adsorption mechanisms include physical adsorption, surface chemical precipitation, ligand effects, electrostatic attraction and ion exchange. Therefore, seeking modification methods with low energy consumption, low production cost, no damage to rod crystal, expansion of pore volume, increase of hydroxyl and other functional groups, and great retention of effective components are issues that need to be considered to improve the phosphorus adsorption capacity of attapulgite.

Selective removal of aqueous Hg2+ by magnetic composites sulfur-containing on the hyper-branched surface: Characterization, performance and mechanism

The adsorbents with recyclable, large adsorption capacity and selective adsorption can effectively remove the pollution and harm of heavy metal ions in water. Therefore, two magnetic composites containing sulfur (MCP-S4 and MCP-S8) on the hyper-branched surface were prepared, furthermore, their structures were characterized and adsorption performance was analyzed by FTIR, XRD, TGA, BET, SEM, TEM, VSM and ICP. The results showed that both MCP-S4 and MCP-S8 had superparamagnetism with saturation susceptibility of 22.10 and 22.26 emu/g, and owned a specific surface area of 11.394 and 11.235 m2/g, respectively. MCP-S4 and MCP-S8 could selectively adsorb Hg2+ with the exist of Fe3+, Cu2+, Co2+, Ni2+, Mn2+, and Al3+ in solution. The adsorption kinetics accorded with pseudo-second-order model and Boyd film diffusion model, and the adsorption isotherm was fitted better with Langmuir isotherm model and D-R model, furthermore, the adsorption was an entropic-increasing and endothermic process. The removal rate of Hg2+ from simulated sewage by the two materials was more than 91%, and the adsorption retention rate was more than 85% after five adsorption-desorption cycles. The adsorption mechanism was analyzed by comparing the changes of FTIR, EDS and XPS spectra before and after adsorption. It was found that functional groups (C–N, CONH, CS, SH) could form stable chelates with Hg2+, which was the main reason why MCP-S4 and MCP-S8 could adsorb Hg2+ selectively, furthermore, S atoms of CS and –SH played a leading role in the process of adsorption. In addition, DFT calculation was also used as an auxiliary means to verify the adsorption mechanism.

Mandarin Biochar-TETA (MBT) prepared from Citrus reticulata peels for adsorption of Acid Yellow 11 dye from water

Dehydration technique with 80% sulfuric acid was used to create a novel biochar from mandarin peel wastes followed by condensate with triethylenetetramine (TETA) to give Mandarin Biochar-TETA (MBT). BJH, BET, FTIR, SEM, DSC, TGA, and EDX studies were used to characterise the MBT. The capacity of the newly developed biochar to remove Acid Yellow 11 (AY11) dye from a water solution was studied. The pH of AY11 dye adsorption was found to be best at pH 1.5. Using 100 ppm AY11 dye as a beginning concentration and 1.75 g L–1 MBT dose, the greatest percent of AY11 dye removal by MBT was 97.83%. The MBT calculated maximum adsorption capacity (Qm) was 384.62 mg g–1. Langmuir (LIM), Freundlich (FIM), Tempkin (TIM), and Dubinin–Radushkevich (DRIM) isotherm models were applied to analyse the experimental data. Furthermore, the results of these isotherm models were investigated by various known error function equations. The MBT experimental data was best suited by the LIM. Pseudo-first-order (PFO), pseudo-second-order (PSO), Elovich kinetic model (EKM), intraparticle diffusion (IPD), and film diffusion (FD) models were used to calculate kinetic data. A PSO rate model with a high correlation (R2 > 0.990) was used to assess the adsorption rate. The main mechanism of the MBT adsorption method of the AY11 dye’s anions adsorption is the electrostatic attractive forces that arise with the increase of positively charged sites in an acidic medium. The obtained data suggest that the prepared MBT adsorbent has the potential to be an effective material to remove the AY11 dye from water and that it may be used repeatedly without losing its adsorption efficiency.

Recovery of surface-plated metals from lead frame scrap using selective leaching and solvent extraction

The selective leaching of surface-plated metals from lead frame scrap followed by metal separation and enrichment through solvent extraction has been investigated. The leaching of lead frame scrap using H2SO4 solution under non-oxidizing and oxidizing conditions could efficiently and selectively dissolve Ni, leaving majority of Cu-substrate in the leach residue for further processing. The leaching carried out in a 1.0 M H2SO4 solution at 400 rpm agitation speed, 90 °C temperature and 15 g/L pulp density yielded a Ni leaching efficiency of 98.6% for 240 min (non-oxidative), but required only 60 min to reach the Ni efficiency of 96.4% while supplying 1.0 L/min O2 (oxidative). For both leaching systems, Cu dissolution was found to be <7% only without any dissolution of precious metals contained in the scrap. The kinetic study showed that the Ni leaching under non-oxidizing conditions proceeded by a single rate-controlling step following film diffusion model with activation energy of 12.6 kJ/mol in the temperature range 50–90 °C.The Ni leaching in oxidative system was however, controlled by a mixed control model comprising film diffusion and chemical reaction with the activation energy of 40.0 kJ/mol in the same temperature range. These results were corroborated by SEM analysis of the leach residue. Subsequently, leach liquor obtained from the oxidative leaching (0.84 g/L Cu2+ and 0.32 g/L Ni2+) was subjected to solvent extraction using LIX 84-I. Based on the extraction data, a two-stage counter-current extraction at A/O ratio = 10/1 was required using 20% LIX 84-I to quantitatively extract and enrich Cu2+ from the solutions (equilibrium pH 2.5). The stripping of Cu-loaded organic phase indicated that a three-stage counter-current stripping using 200 g/L H2SO4 at O/A ratio of 5/1 was required. Nickel(II) from the copper free aqueous solution was extracted and enriched using 20% LIX 84-I at an A/O ratio of 5/1, and was stripped from the loaded organic phase using 20 g/L H2SO4 at O/A ratio of 5/1. The hydrometallurgical route of selective leaching-SX results in not only Cu- and Ni-rich solutions suitable for recovery of final products, but also Ni-free lead frame scrap for further processing by smelting. Finally, a flowsheet has been proposed for the total recycling of lead frame scrap.

Microporous Activated Carbon from Pisum sativum Pods Using Various Activation Methods and Tested for Adsorption of Acid Orange 7 Dye from Water.

Highlights•Pisum sativum pods was used for producing porous activated carbon materials.•Two chemical methods and two gases were used in the activation processes.•Higher performances were achieved by applying ZnCl2 and CO2 for activation.•The products exhibited large surface areas and high AO7 dye adsorption performances.•RMS study of the AO7 dye removal by produced material was reported.This work demonstrates the preparation of high-surface-area activated carbon (AC) from Pisum sativum pods using ZnCl2 and KOH as activating agents. The influence of CO2 and N2 gases during the carbonization process on the porosity of AC were studied. The highest specific surface area of AC was estimated at 1300 to 1500 m2/g, which presented characteristics of microporous materials. SEM micrographs revealed that chemical activation using an impregnation reagent ZnCl2 increases the porosity of the AC, which in turn leads to an increase in the surface area, and the SEM image showed that particle size diameter ranged between 48.88 and 69.95 nm. The performance of prepared AC for adsorption of Acid Orange 7 (AO7) dye was tested. The results showed that the adsorption percentage by AC (2.5 g/L) was equal to 94.76% after just 15 min, and the percentage of removal increased to be ~100% after 60 min. The maximum adsorption capacity was 473.93 mg g−1. A Langmuir model (LM) shows the best-fitted equilibrium isotherm, and the kinetic data fitted better to the pseudo-second-order and Film diffusion models. The removal of AO7 dye using AC from Pisum sativum pods was optimized using a response factor model (RSM), and the results were reported.

Biosorption of crystal violet by nutraceutical industrial fennel seed spent equilibrium, kinetics, and thermodynamic studies

The present research aims to describe a study that would investigate the practicability of using nutraceutical industrial fennel seed spent (NIFSS) is one of the low-cost types of biosorbent which adsorbs a cationic dye, known as crystal violet (CV), from an aqueous solution. The effects of dye adsorption were also investigated: pH, adsorbent dosage, temperature, particle size, and initial dye concentration. Then the experimental equilibrium data attained was analyzed using isotherm models of Langmuir, Freundlich, Jovanovic, Vieth-Sladek, Brouers-Sotolongo, Redlich-Peterson, and Sips. Hence the use of Film diffusion, Pseudo-first-order, Pseudo-second-order, Dumwald-Wagner and Weber-Morris models for kinetic adsorption studies was done. The maximum experimental adsorption capacity, qe, was determined to be 140 mg g−1 at equilibrium conditions in the lab. The maximum adsorption of 166.73 mg g−1 was predicted by the Brouers-Sotolongo isotherm, which had the closest value of correlation coefficient (R2) of 0.987. Pseudo-second order model fits the kinetic data well in this paper. The thermodynamic parameter values such as ΔG°, ΔH°, and ΔS° demonstrated that the adsorption process was non-spontaneous and exothermic. The lower value of ΔH° shows the physical nature of the process. The CV was adsorbed onto NIFSS, as per the evidence by SEM images and FTIR spectra. The possibility of interaction in the CV-NIFSS system is discussed. To remove CV from an aqueous solution, NIFSS is a fast and effective adsorbent.

Selective adsorption of heavy metals from water by a hyper-branched magnetic composite material: Characterization, performance, and mechanism

The development of adsorbents to remove heavy metal ions from water with recyclable, high adsorption capacity, strong selectivity, safe, and economic performances has always been the focus and challenge of current research. A hyper-branched magnetic composite material (Fe3O4@SiO2–S4) was fabricated by a method combining “grafting,“, “branching,” and “modification,“, and the structure was characterized by FTIR, XRD, SEM, TEM, SAED, VSM, TGA, and BET. In addition, the adsorption performance and mechanism for heavy metal ions in water were studied. The as-prepared composite material had excellent selective absorbability for Hg2+, Cd2+, and Ag+ in the presence of Fe3+, Fe2+, Cu2+, Mn2+, CO2+, Zn2+, and Ni2+, and when pH = 6, T = 30 °C, t = 4 h, it reached a saturated adsorption capacity of 2.42, 2.18, and 1.94 mmol/g to Hg2+, Cd2+, and Ag+, respectively. The adsorption isotherm was consistent with the Langmuir isotherm adsorption model, and the Dubinin Redushcke (D-R) model identified that the adsorption was chemical adsorption in nature. The adsorption kinetic followed the pseudo-second-order model and Boyd film diffusion models. The adsorption capacity of as-prepared material remained about 83% after five elutions. The adsorption mechanism and selective adsorption were revealed by FTIR, EDS, XPS, and DFT calculation. N atoms and O atoms of the active functional groups complexed with metal ions to form stable 2 heptachate chelates and 1 tridentate chelate to achieve the effect of adsorption; furthermore, the adsorption was mainly governed by N atoms of Schiff base groups. This work not only explored an innovative method for the construction of adsorbing materials but also provided a promising adsorbent to selectively remove heavy metal ions in water with potential application.

Biosorption of Acid dye by Jackfruit Leaf Powder: Isotherm, kinetics and Response surface methodology studies

A green adsorbent derived from Jackfruit leaf powder (JLP) was used to eliminate Acid Yellow 99 (AY 99) dye from an aqueous medium in this study. We checked the effect of pH, biomass dosage, and temperature (process parameters) on the adsorption potential of AY 99 was explored using the CCD model integrating the RSM approach. At a pH of 2.5, biosorbent dosage of 4 gL-1, and a 30°C temperature, maximum removal was preferred. ANOVA was incorporated to observe the importance of experimental variables and their interactions. The solution pH (A) and biomass dose (C) had the greatest effects on the decolorization of AY 99, according to the findings. ANOVA was used to identify the most important factors, which included two independent variables (A and C) and two quadratic model terms (A2 and C2). The kinetic data were effectively interpreted using a pseudo 2nd order with film diffusion model combination, indicating the chemisorptions phenomenon. Following the model of Langmuir isotherm, the utmost capacity for adsorption was determined to be 418.15 mg g-1 in terms of initial dye concentration. The findings of the maximum adsorption capacity showed that JLP could be employed as a useful adsorbent to eliminate AY 99 from its aqueous medium.

Development of high-performance adsorbent using KOH-impregnated rice husk-based activated carbon for indoor CO2 adsorption

Relatively high indoor CO2 concentration (greater than 1000 ppm) has a negative impact on human health. In this work, a cost-effective CO2 adsorbent (DKOH-AC) was developed by impregnating KOH on rice husk-based KOH activated carbon (KOH-AC, 1439 m2/g). KOH can be successfully loaded on the surface of KOH-AC and significantly changed its surface properties. DKOH-AC still remained a considerable surface area (206 m2/g) and showed a similar Smicro/SBET ratio. In-situ FTIR analysis confirmed that the major CO2 adsorption mechanism of KOH-AC was based on physisorption while that on DKOH-AC involved both chemisorption and physisorption. DKOH-AC showed a higher heat of adsorption (34 ∼ 41 KJ/mol) and gas selectivity (16.6) than these of KOH-AC. KOH-AC quickly reached an adsorption equilibrium (about 50 min) as compared to that of DKOH-AC. In addition, DKOH-AC exhibited an excellent adsorption performance of 2.1 mmol/g for a low concentration of CO2 (2000 ppm ∼ 500 ppm) under indoor conditions. Both the CO2 adsorption isotherm on KOH-AC and DKOH-AC well followed the Langmuir and Freundlich models. The CO2 adsorption kinetics on KOH-AC followed the pseudo-first order model whereas that on DKOH-AC obeyed the pseudo-second order model. The adsorption process was controlled by the intraparticle diffusion combined with the film diffusion model.