Freundlich Isotherm Model Research Articles

Enhanced performance of coal-based adsorbents in removing phenols from highly concentrated coking wastewater: Targeting large-scale applications

Coking wastewater threatens the ecology and environment significantly, but it still has challenges in the efficient removal of organic contaminants due to its complex composition and inadequate biochemical properties. Low-cost coal-based material has potential in treating coking wastewater due to its special structure and surface oxygenic functional groups. In this work, gangue-based materials were modified in different ways and applied to coking wastewater treatment. Combined with the comprehensive analysis of the adsorbents' morphology, structure, and composition with SEM, XRD, FT-IR, XPS, etc., the adsorption behaviors and regeneration properties were extensively investigated. Notably the adsorption and regeneration capacity of the adsorbents are significantly enhanced after modification, BY-C2 exhibits a remarkable COD removal rate of 90.2 % from real coking wastewater, which remains stable at 72.0 % even after 10 cycles. The pseudo-second-order kinetic model and Freundlich isotherm model are found to fit well with the adsorption processes of phenolic compounds in coking wastewater. The adsorption mechanism involves hydrogen bonding, van der Waals' force, capillary forces and electrostatic attraction. This work paves the way for the large-scaled application of coal-based adsorbents in coking wastewater treatment and the subsequent recycling of high-valued organic pollutants.

Bentonite clay reinforced alginate grafted composite hydrogel with remarkable sorptive performance toward removal of methylene green

The rapid industrial progress in today's world has led to an alarming increase in water pollution caused by various contaminants such as synthetic dyes. To address this issue, a new hydrogel sorbent, BC-r-Na-Alg-g-p(NIPAm-co-AAc), was developed by combining bentonite clay, sodium alginate, and poly(N-isopropyl acrylamide-co-acrylic acid) through one-pot free radical polymerization at 60 °C. The developed sorbent was characterized using several analytical techniques including SEM, FTIR, TGA, UTM, and swelling studies. The swelling capacity of the sorbent was observed to increase remarkably with an increase in pH, reaching a maximum of 9664 % at pH 11. In batch mode sorption experiments, the sorbent's performance toward methylene green (MG) was investigated by analysing the effects of contact time, pH, temperature, and concentration. The experimental data were fitted to pseudo-second-order kinetic and Langmuir isotherm models, indicating chemisorption as the dominant interaction mode between the anionic sorbent and cationic MG. However, physisorption may also occur to a lesser extent, indicated by the significant R2 of the pseudo-first-order kinetic and Freundlich isotherm models. Additionally, the sorbent exhibited very little decrease (approximately 5 %) in sorptive performance for six sorption-desorption cycles. Overall, the facile fabrication, excellent swelling (9664 %), promising sorption performance (2573 mg.g−1), and good recyclability (6 cycles) make the developed sorbent a potential candidate for various industrial applications.

Preparation of NH2-MIL-101(Fe) Metal Organic Framework and Its Performance in Adsorbing and Removing Tetracycline.

Tetracycline's accumulation in the environment poses threats to human health and the ecological balance, necessitating efficient and rapid removal methods. Novel porous metal-organic framework (MOF) materials have garnered significant attention in academia due to their distinctive characteristics. This paper focuses on studying the adsorption and removal performance of amino-modified MIL-101(Fe) materials towards tetracycline, along with their adsorption mechanisms. The main research objectives and conclusions are as follows: (1) NH2-MIL-101(Fe) MOF materials were successfully synthesized via the solvothermal method, confirmed through various characterization techniques including XRD, FT-IR, SEM, EDS, XPS, BET, and TGA. (2) NH2-MIL-101(Fe) exhibited a 40% enhancement in tetracycline adsorption performance compared to MIL-101(Fe), primarily through chemical adsorption following pseudo-second-order kinetics. The adsorption process conformed well to Freundlich isotherm models, indicating multilayer and heterogeneous adsorption characteristics. Thermodynamic analysis revealed the adsorption process as a spontaneous endothermic reaction. (3) An increased adsorbent dosage and temperature correspondingly improved NH2-MIL-101(Fe)'s adsorption efficiency, with optimal performance observed under neutral pH conditions. These findings provide new strategies for the effective removal of tetracycline from the environment, thus holding significant implications for environmental protection.

A highly efficient and environmentally friendly approach to utilizing Quercus suber pericarp subfractions to remove metallic cations from aqueous solutions

Increasing water contamination from metal cations is a significant environmental challenge for humans. This has sparked extensive research into the development of adsorbents with superior removal efficiencies. This study assessed the adsorption capacity of crude and lignocellulosic fractions obtained from the pericarp of Quercus suber acorns, specifically focusing on the removal of Pb(II), Cd(II), Ni(II), and Cu(II) ions from aqueous solutions. The lignocellulosic fraction was separated from the crude fraction after extraction of cell wall polysaccharides using water and alkaline solutions. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the crude and lignocellulosic fractions. Data from equilibrium adsorption experiments were analyzed using the Langmuir and Freundlich isotherm models. The study found that the lignocellulosic fraction removed Pb(II) ions more efficiently than the crude fraction, with qmax values of 500.0 mg.g−1. Crude fractions exhibited a considerable retention potential for Cd(II), Ni(II), and Cu(II) ions with qmax values of 95.2 mg.g−1, 333.3 mg.g−1 and 200 mg.g−1 respectively. Crude and lignocellulosic fractions extracted from the acorn Q. suber pericarps could be environmentally friendly biosorbents for the removal of metal cations from aqueous solutions.

Management of trihalomethanes in water by ZnO@kaolinite composite: integrated experimental and modeling studies.

The adsorption of trihalomethanes (THMs) from drinking water was investigated in the current study through comparison studies of kaolinite and ZnO@kaolinite nanocomposites. The clay structural network's successful immobilization on the zincite hexagonal structure of ZnO nanoparticles' lattice layers was verified by the SEM/EDX analysis. Under the optimum conditions, the maximum removal of THMs was achieved by kaolinite and ZnO@kaolinite nanocomposites after 60 min. The adsorption performance of the ZnO@kaolinite nanocomposites was greater than that of kaolinite because the former had a larger surface area than the latter. The Freundlich isotherm model best matched the adsorption experimental data, which also reveals the existence of multilayer adsorption on a diverse surface with the greatest correlation (R2 = 0.956 and 0.954, respectively) for both nanoadsorbents using the pseudo-first-order (PFO), pseudo-second-order (PSO), mixed 1, 2-order (MFSO), and intraparticle diffusion (IPD) models. The mechanism by which THMs in drinking water adsorb onto nanoadsorbents was examined. This revealed that both intraparticle and film diffusion were involved in the adsorption process. Kaolinite and ZnO@kaolinite nanocomposites can be used in water treatment to remove THMs due to their great recyclable and reusable properties, even after six cycles.

Removal of Trace Cu2+ from Water by Thermo-Modified Micron Bamboo Charcoal and the Effects of Dosage

Chronic copper intoxication via drinking water induces diseases and physiological toxicity. Bamboo charcoal has been applied in the treatment of copper (Cu2+) in water. However, the adsorption by micron bamboo charcoal (MBC) of trace Cu2+ in tap drinking water and the underlying factors behind it have not been sufficiently reported. In this study, to improve the adsorption by MBC of trace levels of Cu2+ in drinking water, MBC was thermo-modified and characterized. Through batch experiments, the adsorption equilibrium was analyzed, and isotherm models were simulated. The removal rates and the optimization were investigated through a general full factorial design including the thermo-modified temperature (MT), initial concentration (C0), and dosage. The results indicated that the thermo-modification significantly improved the removal by MBC of Cu2+ at trace level C0. The satisfactorily low level of 0.12 ± 0.01 mg⋅L−1 was achieved in the range of C0 from 0.5 to 2.0 mg⋅L−1 within the short contact time of 0.5 h. The processes conformed to the Freundlich and Langmuir adsorption isothermal models at a C0 lower than 4.0 mg⋅L−1 and higher than 8.0 mg⋅L−1. The correlation between C0 and dosage played an important role in the removal of Cu2+. This work proposes the application of the ecofriendly material MBC and an optimization mode in the removal of trace Cu2+ from tap drinking water. It is also revealed that the positive and negative correlation and the “critical point” of the removal rate with dosage depend on the initial concentrations.

Magnetic activated carbon for the removal of methyl orange from water via adsorption and Fenton-like degradation

Water pollution caused by organic dyes is a critical environmental issue. Although activated carbon (AC) is commonly used for dye adsorption, its effectiveness is limited by challenges in separation and regeneration. To address these limitations, a convenient recyclable magnetic activated carbon (MAC) was fabricated via co-precipitation and calcination method, serving as adsorbent and catalyst for methyl orange (MO) removal through a Fenton-like degradation process. Characterization techniques, including XRD, FTIR, SEM and TEM, confirmed that Fe3O4 nanoparticles (10–20 nm) were uniformly dispersed on AC surface. The MAC maintaining a high surface area (997 m2/g) and pore volume (0.795 cm3/g) and exhibited superparamagnetic properties with a saturated magnetization of 5.52 emu/g, enabling effective separation from aqueous solutions by magnet. Batch adsorption studies revealed that MO adsorption onto MAC followed pseudo-second-order kinetic and Freundlich isotherm model, with a maximum adsorption capacity of 205 mg/g at 25 °C. Thermodynamic analysis showed that the adsorption process was spontaneous and endothermic. Simultaneous degradation of MO and in-situ regeneration of MAC were achieved via Fenton-like reaction using sodium persulfate (PS). Under a PS concentration of 9 mmol/L, the MO removal efficiency near 95% after 60 min, with a total organic carbon (TOC) reduction of 83.1%. The reaction of Fe3O4 and oxygen functional groups on AC surface with PS facilitated the generation of SO4•-, thereby enhancing catalytic degradation of MO. The degradation efficiency improved as the temperature increased from 25 °C to 45 °C. Cycle tests demonstrated that the MO removal efficiency of MAC remained above 90% after 5 cycles of regeneration. Overall, this study highlights the potential of MAC for efficient removal of organic dyes from water through the coupling of adsorption and Fenton-like degradation, providing a promising solution for addressing water pollution challenges.

One-step hot-press synthesis of amino functionalized Zr-based metal organic framework for determination and speciation of trace inorganic arsenic species in water samples with EDXRF spectrometry

Herein, amino functionalized Zr-based metal organic framework (UiO-66-NH2) on carbon cloth substrate was synthesized by using one-step hot-pressing method and the product (UiO-NH2@CC) was evaluated as a new solid phase extraction (SPE) material for determination and speciation of inorganic arsenic species (As(V) and As(III)) in water samples through energy dispersive X-ray fluorescence (EDXRF) spectrometry. SPE efficiency of UiO-NH2@CC was examined in batch and continuous adsorption (pre-concentration) processes and combination of either batch or continuous pre-concentration process with EDXRF spectrometry proposed analytical method, offering remarkable benefits (i.e., user-friendly, no elution procedure, environmentally friendly and cost-effective, etc.). Batch adsorption studies indicated that As(V) could be selectively adsorbed by UiO-NH2@CC at pH 2 and better represented by Freundlich isotherm model in 60 min of equilibrium time. Continuous adsorption studies at pH 2 demonstrated a drop in As(V) adsorption efficiency of UiO-NH2@CC for sample loading volume above 30 mL with increasing flow rate from 0.3 to 1.0 mL/min and initial As(V) concentration from 20 to 100 µg/L. By considering fortification experiments on real water samples at two levels (5 and 50 µg/L) of As(V) species, both batch and continuous pre-concentration steps coupled with EDXRF spectrometry, with LOD values of 0.790 and 0.220 µg/L, respectively, indicated good recoveries in the range of 87(±11)–104(±7) with no statistically significant differences. Finally, the continuous pre-concentration step followed by EDXRF measurement, as a representative analytical method, was of successful applicability to the speciation of As(III) and As(V) in real water samples with notable advantages (i.e., effortless, economical, practical and reproducible, etc.).

Removal of Moxifloxacin from Aqueous Solutions Using GO/Cr-MOFs.

The composite material, consisting of graphene oxide (GO) and chromium metal-organic frameworks (Cr-MOFs), was successfully synthesized by using a solvothermal method. The organic ligand employed was 2,5-dihydroxyterephthalic acid, while chromium acetate served as the source of the metal. The resulting material underwent characterization through Fourier transform infrared, scanning electron microscopy, and X-ray diffraction techniques. Subsequently, the adsorption capacity of the composite material toward moxifloxacin was evaluated. The results indicated a gradual increase in the moxifloxacin removal rate from GO/Cr-MOFs over time until reaching an equilibrium with a maximum removal rate of 90.4%. Additionally, it was observed that higher temperatures led to a decrease in the adsorption capacity. By incorporating 30 mg of GO/Cr-MOFs into a solution containing 40 ppm of moxifloxacin, the adsorption capacity could be maximized at 222.25 mg/g. Experimental data on MOF adsorption of moxifloxacin were analyzed using pseudo-first-order kinetics (PFO), pseudo-second-order kinetics (PSO), and Langmuir, Freundlich, and Temkin isotherm models for theoretical research purposes. Results showed that the PSO model exhibited a better correlation than the PFO model did. Furthermore, experimental data demonstrated good agreement with the Freundlich isothermal model, suggesting its effectiveness in accurately describing the adsorption process. Henceforth, it can be concluded that chemisorption plays a significant role in removing moxifloxacin by GO/Cr-MOFs. The van't Hoff equation analysis revealed an exothermic and spontaneous nature of moxifloxacin adsorption onto GO/Cr-MOFs. Compared to other materials, the GO/Cr-MOF composite exhibited high potential for applications such as drug removal or related fields.

Waste biomass-derived activated carbons for selective oxygen adsorption

Activated carbons (ACs) derived from waste rice husk ash (RHA) exhibit remarkable potential for selective oxygen adsorption. The pore morphology of the prepared materials was characterized utilizing BET measurement, t-plot, and BJH-plot suggesting a linear relation between activation temperature and mesopore volume, whereas, micropore volume decreases at activation beyond 550 °C. FT-IR spectroscopy confirms their non-polar surface. Notably, AC-600 achieves an outstanding O2/N2 (0.21/0.78) of 152.7 at 0.01 bar at 25 °C, owing to the non-polar nature of the surface, favouring oxygen adsorption due to its low quadrupole moment. Additionally, the mixed micro and mesoporous structure of AC-600 significantly enhance the oxygen adsorption, showing an ∼18.4% (or 1.2-fold) increase compared to AC-500. However, a ∼32.3% decrease in oxygen uptake was observed for AC-800 due to excessive “burn-off”. Adsorption selectivity, assessed with Ideal Adsorption Solution Theory (IAST) and fitted to the Freundlich isotherm model, and adsorption kinetics, analysed using the pseudo-second-order Lagergren and Webber-Morris intraparticle diffusion models, highlighted the impact of activation temperature on the porosity of the material. Understanding the surface chemistry and pore morphology of activated carbon offers deeper insights to enhance oxygen uptake capacity, advancing the development of sustainable, industrially viable materials for oxygen production.

Efficient Adsorption and Elimination of Tm3+ for Enhanced Seed Germination Using Pillar[5]Arene Polymer.

While rare earth elements (REEs) are essential for modern technology, their production methods raise concerns for agriculture. Researchers are now exploring ways to control and recycle REEs pollution, aiming to minimize agricultural impacts and potentially even develop methods to utilize these elements for improved crop yields. Regarding this issue, a new type of pillar[5]arene polymer (Pol-P[5]-BTZP) has been designed and synthesized by click reaction to enhance the efficiency of adsorption and recovery of rare earth metals. This polymer incorporates the unique structure of 2,6-di-1,2,3-triazolyl-pyridine. The results of various analyses revealed that Pol-P[5]-BTZP exhibits excellent thermal stability, a high specific surface area, and well-distributed networks of micropores and mesoporous structures. The adsorption capacity of Pol-P[5]-BTZP for Tm3+, a representative REE, was evaluated using the Langmuir and Freundlich isothermal adsorption models with a maximum adsorption capacity (Qmax) of 127.71 mg/g. Furthermore, the versatility of Pol-P[5]-BTZP in adsorption and recovering various REEs was tested. In addition to its adsorption capabilities, the potential of Pol-P[5]-BTZP for rare earth recovery and reuse was assessed through experiments on the impact of Tm3+ and La3+ on seed germination. These experiments demonstrated the wide-ranging applicability of Pol-P[5]-BTZP in recovering and reusing REEs for green agriculture.

Core-shell V2O5- Gum ghatti grafted poly (acrylamide-co-methacrylic acid) adsorbent for the removal of methylene blue dye in water: Kinetic, equilibrium and thermodynamic studies

Herein, vanadium pentoxide (V2O5) encapsulated Gum ghatti grafted poly(acrylamide-co- methacrylic acid) adsorbent was synthesized to remove methylene blue dye from water. The materials were characterized by FTIR, TEM, SEM, Raman and XRD analysis. Batch adsorption studies were performed on the materials. Several variables' effects on methylene blue removal, including pH, contact time, initial dye concentration, and adsorbent dosage, were examined. Kinetics and thermodynamic analysis were also carried out for the adsorbent-adsorbate interaction to determine the maximum adsorption and mechanism for adsorption. By using UV-Vis spectrophotometric analysis, the dye concentration was evaluated both before and after adsorption. Langmuir, Freundlich, and Dubini-Radushkevic's isotherm models were used to analyze the adsorption data. Results showed a maximum adsorption efficiency of 92 % at a pH of 9 and 0.2 g as the maximum adsorbent dosage. The study followed the Langmuir isotherm model with a correlation coefficient (R2) of 0.9995. The results from the kinetic studies show a pseudo-second-order mechanism. The negative values of the Gibbs free energy change ΔG° ranging from −10.57 KJmol−1 to −9.64 Kmol−1 within the temperatures of 298 K to 313 K is an indication of a spontaneous process. A negative enthalpy change (ΔH° = −29.05 KJmol−1) shows an exothermic process and a negative entropy change (ΔS° = −0.06 KJmol−1) represents a highly ordered system. ANOVA in Microsoft Excel and other statistical analyses were used to evaluate the effects of time, pH, concentration, dose, temperature, and other factors on the effectiveness of dye adsorption. Importantly, every parameter that was investigated showed statistically significant impacts on the removal of dye (p < 0.05), revealing their important impact on the adsorption process.

Polycyclic aromatic hydrocarbon derivatives onto polar microplastics of polyurethane: equilibrium, thermodynamics, and kinetics of monolayer-multilayer adsorption.

The study of the adsorption of polycyclic aromatic hydrocarbons on microplastics (MPs) has attracted much attention as to how microplastics can act as carriers of these pollutants. Polyurethane (PU) is one of the MPs found in aquatic environments, containing different functional groups it can interact with polar and nonpolar molecules. PAH derivatives (dPAHs) present different properties and thus can be adsorbed by different interactions; thus, this study investigated the adsorption of fluorene (FLN), dibenzothiophene (DBT), dibenzofuran (DBF), and carbazole (CBZ) onto PU MP. The Langmuir, Freundlich, and BET isotherm models were examined, and the BET model best fitted. The adsorption was a nonspontaneous process, exothermic for mono- and multilayer formation for FLN, DBT, and CBZ, and endothermic for DBF monolayer formation. The adsorption monolayer was formed by van der Waals forces, H─bonding, and π─π interactions, while the formation of the multilayer can be explained by π─π and hydrophobic interactions. The pseudo-second-order model proved to be more consistent for the adsorption of dPAHs. The adsorption in artificial seawater shows no significant differences for the monolayer but favored the adsorption multilayer due to the salting-out effect. Due to the existence of several adsorption mechanisms, PU MP interacts with dPAHs in greater quantities when compared to a MP with a simpler structure.

Turning waste into wonder: Arsenic removal using rice husk based activated carbon

In this study, rice husk activated carbon (RHAC) was synthesized by physicochemical activation, which consists of heat treatment with CO2 gasification and KOH chemical treatment to eliminate arsenic (As) from the polluted water. Initial arsenic concentrations, solution pH, solution temperature and contact time are the parameters that have been tested in this study. The characterization study showed that RHAC has a high BET surface area (815.52 m2/g) and its pore structure was found to be mesoporous with an average pore diameter of 2.96 nm. Characterization studies, including X-ray diffraction analysis (XRD), Raman spectroscopy and scanning electron microscopy (SEM) were employed to determine the RHAC’s performance. The adsorption of As towards RHAC followed the Freundlich isotherm model and pseudo-first order with adsorption process was favorable at higher arsenic concentrations. The mechanism study also signified that the adsorption of As-RHAC was limited by film-diffusion. Thermodynamic studies indicated that the As-RHAC adsorption system was endothermic, random, spontaneous, feasible in nature and governed by the chemisorption process. Desorption and regeneration studies of RHAC showed that it can be utilized up to 5 cycles and is stable for the water treatment facilities.

Removal of Pb(II) ions from aqueous solutions using natural and HDTMA-modified bentonite and kaolin clays

This work focused on the removal of Pb(II) from aqueous solution using kaolin and bentonite clays modified with hexadecyl trimethyl ammonium bromide (HDTMA). The clays were characterized using a zetasizer, scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), Brunauer-Emmet-Teller (BET), Fourier-transform infrared (FTIR) spectroscopy and thermal gravimetric analysis (TGA). Factors that influence the adsorption of Pb(II) from aqueous solution, namely pH, contact time, adsorbent mass, ionic strength, temperature and initial Pb(II) concentration were investigated. The results show that HDTMA was successfully incorporated into the kaolin and bentonite clay structures. The most favorable parameters for the adsorption of Pb(II) ions onto all adsorbents was pH of 6.0, temperature of 25 °C and adsorbent mass of 200 mg. Adsorption isotherms and kinetic studies showed that the adsorption of Pb(II) onto kaolin, bentonite and organobentonite clays followed the Langmuir isotherm and pseudo-first order kinetic model, while the adsorption onto organobentonite was better explained by the Freundlich isotherm and pseudo-second order kinetic model. Maximum monolayer adsorption capacity of organobentonite, calculated from the Langmuir model was 18.75 mg/g, which is higher than that obtained for the unmodified bentonite (14.71 mg/g); while for organokaolin it was 2.26 mg/g, which is less than that of the unmodified kaolin (4.19 mg/g). Thermodynamic studies showed that the reactions were exothermic and unfavoured at high temperatures. The adsorbents also showed good removal efficiency for up to four regeneration cycles.

Removal of sulphur and nitrogen compounds from model fuel by adsorption of modified activated carbon

This study aimed to achieve the highest percentage removal of dibenzothiophene (DBT), quinoline (QUI), and indole (IND) adsorbed by double-impregnated modified activated carbon (MAC). Modification of commercial activated carbon (AC) by sulphuric acid (H2SO4) of 15%, 30%, 45%, 60%, and 75% w/v followed by subsequent 1 zinc chloride (ZnCl2): 1 AC impregnation ratio and activated at 500 oC in a muffle furnace under self-generated atmosphere for an hour. The determination of optimized MAC was identified through the highest removal rate of DBT, QUI, and IND from adsorption experiments which were analysed using an ultraviolet-visible (UV-Vis) spectrophotometer. It was found that DBT and IND showed a removal high percentage of up to 86.23% and 82.77% respectively by using 75% H2SO4 with ZnCl2 MAC. Meanwhile, QUI favoured 30% H2SO4 with ZnCl2 MAC with a removal percentage of 33.17% which was still higher than unmodified AC. Physical and chemical properties such as the morphological structure, elemental analysis, porosity, pore size, surface functional group, percentage yield, pH, bulk density, content, ash content, and iodine number were studied for the optimized MAC. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy and Fourier transform infrared spectroscopy (FTIR) were used to characterize the MAC. Both MACs showed high percentage yields of 72.08% and 71.13% for 30% and 75% H2SO4 and ZnCl2 MAC respectively. Meanwhile, the pH was between the ranges of 5.36-5.53 for both MACs. Bulk densities were also favourable while the moisture and ash content were within acceptable limits. Iodine numbers for 30% and 75% H2SO4 and ZnCl2 MAC were 857 and 861 mg/g respectively, hence indicating that the MAC achieved high porosity and good adsorption performance. Langmuir, Freundlich, and Temkin adsorption isotherm models as well as pseudo-first order (PFO) and pseudo-second order (PSO) kinetic models were considered for understanding the adsorption mechanisms. The study revealed that DBT, QUI, and IND removal processes, followed the Langmuir adsorption isotherm model with correlation coefficients, R2 of 0.9905, 0.9791, and 0.9964 respectively. Moreover, the adsorption kinetic data of DBT, QUI, and IND provided a better fitting to the PSO kinetic model with R2 of 0.9992, 0.9987, and 0.9998 respectively. According to the Langmuir isotherm model and PSO kinetic model, the adsorption mechanisms of DBT QUI and IND were chemisorbed under monolayer formations.

Ammonium ion removal from contaminated water using Cikancra natural zeolite

Abstract Water quality in water bodies is deteriorating due to human activities such as industries, agriculture, and households. These activities have been reported to increase the levels of nitrogen species in water bodies, including ammonium (NH4 +). Various processes have been used to reduce NH4 + concentration in water, including adsorption and ion exchange using zeolite which is renowned as an excellent adsorbent and ion exchange material. In this study, we assessed the ability of Cikancra natural zeolite to reduce the NH4 + concentration in water. Heat pre-treatment was carried out on the zeolite to reveal its effect on the NH4 + removal rate. Furthermore, several factors such as contact time, grain size, and initial NH4 + concentration were evaluated to determine the optimum absorption condition. The experimental results reveal that heat-pretreated natural zeolite can reduce the NH4 + concentration by up to 84% after 60 minutes of contact time. Furthermore, the absorption capacity of the zeolite is reaching 2.37 mg/g at an initial NH4 + concentration of 50 mg/L. The evaluation using Freundlich and Langmuir isotherm models indicates that the process occurs physically due to Van Der Waals interaction between the adsorbate and the adsorbent.

Utilization of Base and Acid Modified Rice Husk-Corncobs Composite for Removal of Chromium (VI) Ion in Simulated Tannery Wastewater

In the ever-increasing blind race of industrialization and urbanization environmental contamination by toxic heavy metal ions is becoming a serious issue for both scientists and masses. Hence, the objective of this paper was to evaluate the utilization of base (BMOD) and acid (AMOD) modified rice husk-corncobs composite for the removal of chromium (VI) Ion in simulated tannery wastewater using appropriate standard techniques. SEM-EDX, XRD and FTIR characterizations revealed the elemental composition, crystallographic structures and the chemical bonds respectively. The results of the sorption kinetic study showed that the data fitted well with the pseudo-second order model for both acid modified (AMOD) and base modified (BMOD) biosorbent with a maximum adsorption of 28.46 mg/g and 39.66 mg/g respectively. The results of the sorption isotherm study showed that they both fitted Freundlich isotherm model. From the results obtained, rice husk and corn cob were effective biosorbent for the removal of Cr (VI) ion from tannery effluent.

Using natural antioxidant Rhubarb extracts in PVA/chitosan bio-adsorbent films for efficient removal of cationic and anionic dyes from polluted water

In this research, sustainable membrane films were developed for removal of cationic and anionic dyes from wastewater based on polyvinyl alcohol/chitosan (PVA/CS) incorporated with natural antioxidant Rhubarb dye (Rh) extracts. Rh dye was extracted from Rhubarb roots by a green method. Three different quantities of Rh dye extracts (i.e., 2.5, 5, and 10 %) were used to fabricate crosslinked PVA/CS films by solvent-casting approach. The fabricated films subjected to different techniques such as X-ray diffraction (XRD), scanning electron microscopy combined with energy dispersive X-ray spectroscopy (SEM-EDX), dynamic mechanical analysis (DMA), as well as antioxidant activity. In all cases, the incorporation of Rh dye extracts inside the composite improved the crystallinity, biocompatibility, stress–strain properties, besides the DPPH scavenging activity reached 42.50 % for PVA/CS-10 % Rh membrane compared to PVA/CS blank (i.e., ∼ 2.10 %). Dyes adsorption including different cationic and anionic dyes implemented for all selected membranes. The data revealed that the membrane containing 10 % Rh dye was the optimum for removal of malachite green oxide (MG, 93 %) as cationic dye and methyl orange (MO, 95.70 %) as anionic dye. Moreover, the kinetics of the removal process exhibited that this process followed the Langmuir, Freundlich, Temkin, Dubinin-Radushkevich models, and the pseudo-1st order kinetic model, with an R2 of 0.998 and 0.943 for MG and MG, respectively. Whereas, the adsorption process corresponded to the Freundlich isotherm model, with coefficients R2 was of 0.989 and 0.988 for MO and MG, respectively. Other parameters including dye concentration, contacting time, pH media, and kinetic studies were also applied on PVA/CS-10 % Rh membrane.

Methyl alginate/Santa Barbara amorphous-15/iron oxide nanocomposite for efficient removal of different pollutants from aquatic environments

A new eco-friendly mesoporous magnetic nanocomposite (MMNCs) known as " methyl alginate@SBA-15/IONP " has been created as a nano-adsorbent system for purifying water contaminants. The production process consisted of multiple stages, commencing with the synthesis of Santa Barbara Amorphous-15 (SBA-15) utilizing the hydrothermal approach. Subsequently, Iron oxide nanoparticle (IONP) was prepared onto SBA-15 through an in-situ co-deposition method. Experimental studies were carried out on various factors affecting the adsorption process of Lead (II) ion (Pb2+), Methylene Blue (MB), and Chlorpyrifos (CPS). Furthermore, Langmuir and Freundlich isotherm models, two kinetic models (pseudo-first-order (PFO) and pseudo-second-order (PSO)), and thermodynamic investigations were conducted for the methyl alginate@SBA-15/IONP MMNCs system. Freundlich isotherm model with PSO kinetics describes the adsorption behavior and thermodynamic parameters show the spontaneous and endothermic nature of adsorption of Pb2+, MB, and CPS in methyl alginate @ SBA-15/IONP MMNCs.