Monolayer Coverage Research Articles

Efficient adsorption and mechanism analysis of antibiotics by UiO-66-NH2/Bi2MoO6 composite materials

The widespread use of antibiotics in human and animal health has caused significant water pollution and increased microbial resistance, posing risks to human health and ecosystems. In this study, Bi2MoO6 nanoflowers and UiO-66-NH2 octahedra (UN-BMO) composites were synthesized via a solvothermal method and applied for the first time to antibiotic adsorption. The 3 % UN-BMO composite demonstrated high adsorption capacities: 37.74 mg·g−1 for ciprofloxacin hydrochloride (HCIP), 31.05 mg·g−1 for tetracycline (TC), 79.86 mg·g−1 for amoxicillin (AMX), and 85.54 mg·g−1 for erythromycin (EM), with adsorption rates of 98.3 % (15 s), 97.6 % (30 min), 84.1 % (60 min), and 86.4 % (100 min), respectively. Kinetic and isotherm models indicated that HCIP adsorption involves both monolayer and multilayer coverage, with a mix of chemical and physical processes. TC primarily follows multilayer physical adsorption, while AMX shifts from multilayer physical adsorption at low temperatures to monolayer physical adsorption at higher temperatures. EM is characterized by monolayer adsorption. Thermodynamic analysis revealed that HCIP, AMX, and EM adsorption is endothermic, while TC adsorption is exothermic. FTIR and XPS analyses confirmed that HCIP, AMX, and EM adsorption is dominated by π-π interactions and hydrogen bonding, with TC adsorption also involving electrostatic interactions.

Characterization and performance of novel carbon-doped aluminum-modified bentonite for cost-effective fluoride removal

Elevated fluoride levels in water pose a critical global health issue, necessitating advanced remediation strategies. This study introduces a novel, cost-effective approach using clay minerals, specifically bentonite, enhanced with carbon-doped aluminum. The resulting composite, carbon-doped aluminum-bentonite (CCDAB), exhibits exceptional fluoride adsorption performance. Detailed structural analyses by SEM, FTIR, BET, and X-ray diffraction reveal successful carbon-doped aluminum integration, which markedly improves fluoride uptake. Adsorption kinetics adhere to pseudo-second-order models, signifying predominant chemical interactions, while the Langmuir isotherm model indicates monolayer coverage. CCDAB achieves a fluoride adsorption capacity of 85.51 mg/g and a removal efficiency of 95.3 %, demonstrating robust performance even in the presence of competing ions. Its efficacy over a broad pH range (3−7) is attributed to its high point of zero charge (pHpzc), which enhances electrostatic interactions. Carbon doping introduces additional active sites, synergistically enhancing fluoride removal alongside aluminum oxide. Thermodynamic analysis confirms that the process is both spontaneous and endothermic. The mechanisms of fluoride removal encompass electrostatic attraction, ion exchange, and surface complexation. This study highlights CCDAB’s promise as a highly effective and economical solution for fluoride contamination in water.

Factors influencing quantum evaporation of helium from polar semiconductors from first principles

While there is much indirect evidence for the existence of dark matter (DM), to date it has evaded detection. Current efforts focus on DM masses over ∼GeV—to push the sensitivity of DM searches to lower masses, new DM targets and detection schemes are needed. In this work, we focus on the latter—a novel detection scheme recently proposed to detect 10–100 meV phonons in polar target materials. Previous work showed that well-motivated models of DM can interact with polar semiconductors to produce an athermal population of phonons. This new sensing scheme proposes that these phonons then facilitate quantum evaporation of He3 from a van der Waals film deposited on the target material. However, a fundamental understanding of the underlying process is still unclear, with several uncertainties related to the precise rate of evaporation and how it can be controlled. In this work, we use density functional theory calculations to compare the adsorption energies of helium atoms on a polar target material, sodium iodide, to understand the underlying evaporation physics. We explore the role of surface termination, monolayer coverage, and elemental species on the rate of He evaporation from the target material. Using this, we discuss the optimal target features for He-evaporation experiments and their range of tunability through chemical and physical modifications such as applied field and surface termination. Published by the American Physical Society 2024

Efficacy of Andrographis paniculata leaf extract as a green corrosion inhibitor for mild steel in concentrated sulfuric acid: Experimental and computational insights

The rising demand for eco-friendly corrosion inhibitors has intensified efforts to find sustainable alternatives to hazardous chemical inhibitors widely used in industry. Mild steel, although commonly utilized in acidic environments, is prone to significant corrosion, necessitating effective solutions to prevent structural degradation. This study investigates the potential of Andrographis paniculata leaf extract (APLE) as a sustainable, green corrosion inhibitor for mild steel in concentrated sulfuric acid, a condition representative of harsh industrial environments. Using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) methods, APLE demonstrated a high inhibition efficiency of 95.14% at a concentration of 4000 ppm, effectively reducing both anodic and cathodic corrosion reactions. Scanning electron microscopy (SEM) revealed a protective layer formation on the steel surface, significantly reducing corrosion. The adsorption of APLE followed the Langmuir isotherm, indicating monolayer coverage, while quantum chemical calculations validated APLE's electron-donating capability, enhancing surface stability through physisorption. These findings underscore APLE as a viable, eco-friendly alternative to conventional inhibitors, offering promising applications in various acidic environments.

Biosorption of cypermethrin from aqueous solutions by Pediococcus acidilactici: kinetics, isotherms, and mechanisms.

Pediococcus acidilactici is an effective adsorbent for removing of pyrethroid insecticides. This study investigated the biosorption characteristics and mechanisms of P. acidilactici D15 using adsorption measurement, scanning electron microscopy, and Fourier-transform infrared spectroscopy. Isotherm and kinetic models were used to analyze the biosorption process. The Langmuir isotherm model best described the cypermethrin biosorption process, with the maximum adsorption capacity of P. acidilactici D15 being 21.404 mg/g. The biosorption appeared to involve monolayer coverage with uniform forces. The pseudo-second-order model also fits well. The rate-controlling steps involved intraparticle diffusion, film diffusion and chemosorption. The main cellular components involved in cypermethrin biosorption were exopolysaccharides, spheroplast, and cell wall, especially peptidoglycan. The functional groups (-OH, -NH, -CH3, -CH2, -CH, -CONH-, -CO, and -C-O-C-) from proteins, polysaccharides, and peptidoglycan on the cell surface likely played a role in binding cypermethrin. Additionally, P. acidilactici D15 effectively reduced cypermethrin in pickle wastewater. These findings suggest that P. acidilactici D15 could be a potential agent for reducing pesticide residues, laying the groundwork for treating pickle wastewater containing such pesticide residues. © 2024 Society of Chemical Industry.

Hydrogen adsorption on zinc-terminated ZnO(0001) surface at varying coverages and its effects on electronic and optical properties: a DFT+U study

Abstract Spin-polarized density functional theory implementing Hubbard corrections (DFT + U) were utilized to study H adsorption of different coverages on Zn-terminated ZnO(0001) surface. Changes in electronic and optical properties were observed upon H adsorption of varying coverages, namely with 0.25 monolayer (ML), 0.50 ML, 1 ML, and 2 ML coverage. In terms of surface structure, H atoms were found to adsorb on top of Zn forming Zn–H bond lengths ranging from 1.54–1.73 Å for certain coverages. On the other hand, O–H bond length values are 2.41 Å and 2.37 Å for 0.50 ML and 2 ML coverage respectively. Additionally, for 0.50 ML, the most stable configuration is when one H atom adsorbs on top of Zn and the other near the hollow site. At low coverage (0.25 ML and 0.50 ML), H prefers to interact with topmost layer Zn atoms resulting to shifts in the electronic bands relative to the pristine surface’s. In addition, at high coverage (1 ML and 2 ML), shifting of bands are observed and are mainly guided by Zn–H atom interaction for 1 ML and weak H–O atom interaction for 2 ML. The observed decrease in band gap as the coverage was increased from 1 ML to 2 ML is supported by the red shift in the absorption plot. However, for low H coverage adsorption, the optical plots deviate due to emergence of flat bands. Changes in electronic properties such as shifts in conduction band minimum and decrease in measured band gap occur as guided by the interaction of adsorbed H atoms with the surface atoms and are supported with obtained optical plots. These findings present the tunability of Zn-terminated ZnO(0001) polar surface properties depending on H coverage.

Synthesis of cubic mesoporous silica SBA16 functionalized with carboxylic acid in a one-pot process for efficient removal of wastewater containing Cu2+: Adsorption isotherms, kinetics, and thermodynamics

Wastewater containing heavy metal ions, such as Cu2+, that are released into the environment will cause irreparable damage to the nature and human health of living. It is, therefore, absolutely crucial to remove these toxic ions from water. Herein, this paper utilizes the cyano group as a functional reagent to prepare carboxyl-functionalized SBA16 for adsorbing Cu2+ in water. In this paper, 2-cyanoethyltriethoxysilane is employed as a functionalizing reagent to prepare carboxyl-functionalized SBA16 through a one-pot method. The prepared material was characterized using various techniques, such as WXRD, TEM, FT-IR, and XPS. The results indicated that the introduction of the functionalizing reagent did not disrupt the original cage-like cubic mesoporous structure (Im3m symmetry) of SBA16. Crucial adsorption factors, namely pH, adsorbent dosage, Cu2+ initial concentration, and contact time, affecting the removal of Cu2+ were monitored and the optimum adsorption conditions were determined. Isotherm and kinetic investigations were conducted and a non-linear fitting method of experimental data was used to obtain isotherm and kinetic parameters. Maximum adsorption capacity reaches 181.3 mg g−1 was achieved in 60 min at pH = 3. Adsorption kinetics and adsorption isotherm followed the pseudo-second-order (R2 = 0.999) and Langmuir (R2 = 0.999) models, respectively. This suggests that the adsorption process primarily involves chemisorption and monolayer coverage. Thermodynamic parameters showed the spontaneous and endothermic nature of the adsorption process. After 5 cycles, the adsorbent still maintains a good adsorption capacity for Cu2+. This suggests promising applications for the adsorbent in treating wastewater containing Cu2+.

Factors influencing surface coverage and structural organization of phosphonic acid self-assembled monolayers on zinc oxide

Factors influencing surface coverage and structural organization of phosphonic acid self-assembled monolayers on zinc oxide

Design and testing of an (inert) gas cell for in situ polarization modulation infrared reflection absorption spectroscopic (PM-IRRAS) measurements under specific atmospheres.

Infrared reflection absorption spectroscopy (IRRAS) is a powerful surface-sensitive analytical technique to characterize the adsorbed molecules on metal surfaces down to (sub)monolayer coverage. In this paper, a new (inert) gas cell is presented that expands the scope of the commercially available Bruker PMA50 module. The cell is designed as a sample holder to measure thin films of molecules adsorbed on a metal substrate under a specific gaseous atmosphere. The dimensions of the cell are chosen in such a way that it can be transferred into a glovebox via the standard entrance port (Ø150mm), allowing the investigation of air-sensitive molecules under an inert-gas atmosphere. The cell has two hose connections through which the gas atmosphere can be varied as desired. This also allows for studying the reactivity of the adsorbed structures toward the surrounding gas in situ and in a (potentially) time-dependent fashion. Furthermore, the metal substrate can be irradiated via an exposure window to investigate the influence of light on the adsorbed molecules and/or their reactivity. Using the polarization-modulation (PM-) IRRAS technique along with the described gas cell, an air-sensitive molybdenum(0) tricarbonyl complex adsorbed on an Au(111) surface is investigated. This complex reacts with molecular oxygen to the molybdenum(VI) trioxo analog, and this conversion is accelerated by irradiation with light of 365 and 440nm.

Sequestration of Ni2+ and Zn2+ utilising agricultural biowaste-based amorphous M−SiO2 and modified green M−SiO2/Fe3O4 nano-adsorbents: Modelling and electroplating wastewater performance

This work reports the synthesis of novel amorphous mesoporous silicon dioxide (M−SiO2) nanoparticles and modified hybrid green mesoporous silicon dioxide embedded magnetite (M−SiO2/Fe3O4) nanocomposite by one-pot co-precipitation green approach. The nano-adsorbents’ ability to sequester Ni2+ and Zn2+ ions was investigated in batch experiments using synthetic solutions. The M−SiO2/Fe3O4, having specific surface area of 171.71 m2/g and mesoporous diameters of 6.281 nm, exhibits soft ferromagnetism with a saturation magnetisation of 35.45 emu/g. Specific surface areas and mesoporous diameters of 909 m2/g and 2.288 nm were recorded for M−SiO2. The Langmuir isotherm, pseudo second order kinetic, and Elovich kinetic were found to be best fitted to explain the highest capability of adsorption. The Langmuir monolayer coverage (qmax) of 108.70 and 96.15 mg/g for Ni2+ and Zn2+ by M−SiO2/Fe3O4, respectively, was notably higher than M−SiO2 (80.65 and 72.46 mg/g). The best-fitted kinetics imply that chemisorption predominates on M−SiO2 and M−SiO2/Fe3O4 heterogeneous adsorption surfaces. Thermodynamic parameters confirm endothermic adsorption of cationic metals, and sequestration improved marginally at elevated temperatures. The lab scale cost estimation, magnetic separability and superior metal ions sequestration efficacy of M−SiO2/Fe3O4 nanocomposite up to five ad-desorption cycles with > 90 % regenerability render it an economically feasible and recyclable nano-adsorbent. The feasibility of cationic metals sequestration from electroplating effluent confirms an effective and cost-efficient environmentally friendly nano-adsorbent (M−SiO2/Fe3O4) for treatment of wastewater contaminated with potentially toxic metals.

Unveiling the Composition-Dependent Catalytic Mechanism of Pt-Ni Alloys for Oxygen Reduction: A First-Principles Study.

Unveiling the composition-dependent catalytic mechanism of Pt-based alloy cathodes for the oxygen reduction reaction (ORR) helps improve the proton exchange membrane fuel cells. Using density functional theory calculations, this study investigates the ORR catalytic performance of the Pt-Ni system with various compositions (1.00, ∼0.99, 0.75, 0.50, 0.25, ∼0.01, and 0.00). The ordered solid solution PtNi3(111) system shows activity comparable to Pt(111) and is cost-effective. The Ni1/Pt(111) system, featuring a single Ni atom on the Pt(111) surface as a surface single-atom alloy (SSAA), demonstrates the highest activity with an overpotential of only 0.28, which could be further reduced to 0.21 V by decreasing the surface Ni concentration to 1/16 monolayer coverage. The predicted high activity of Ni1/Pt(111) is confirmed when considering factors such as the implicit solution environment, constant potential conditions, and protonation capability. Moreover, surface-adsorbed oxygen species driven by reaction conditions stabilize these single Ni atoms of Ni1/Pt(111) by preventing segregation and dissolution processes, thereby exhibiting a dual functionality. This study reveals the composition dependence of Pt-based alloys and highlights the stability mechanisms of SSAA catalysts during the ORR.

Appraisal of Characterization and Adsorption Isotherm in the Bioremediation of Cu and Zn Ions from Aqueous Solutions Exploiting Unmodified Corn and Coconut Husk

Environment is contaminated by heavymetals has emerged as a substantial globaly. Conventional remediation methods have proven inadequate and costly in addressing this issue. Hence, there is a pressing need to discover bio-remediation as a cost effective, effectual, and environmentally, a substitute for heavymetal removal. This work investigates the adsorption behaviour of Corn Husk (CH) and Coconut Husk (CCH), an inexpensive adsorbent, towards Cu and Zn ions for potential application in wastewater treatment. The physico-chemical variables of unmodified CH and CCH were appraised, and batch experimental methods were employed to study variables like pH, contact time, size of particle, and preliminary content of metals. The impact of solution pH on metals uptake by the adsorbent was investigated on the pH range of 3 to 8, revealing optimal removal efficiencies at pH 6 for Cu and pH 5 for Zn. Equilibrium adsorption times were determined to be 80 minutes for Cu and 60 minutes for Zn ions onto CH and CCH. adsorption volumes is conforming to mono-layer coverage, attained from the Langmuir plots were 4.792 mg/g and 4.594 mg/g respectively for Cu and Zn metals onto the CH and 4.771 mg/g and 4.400 mg/g for their adsorption onto CCH. Experimental values were confirmed to the Langmuir model and Freundlich model, with the Langmuir model providing the best fit. The CH based adsorbent was generally found to have an increased capacity of adsorption of the metal contents than Coconut husk (CCH). These findings underscore the strength of Corn husk as an active adsorbent to extract cationic heavymetal contents from industrial effluents.

Assessing the Stability and Photocatalytic Efficiency of a Biodegradable PLA‐TiO2 Membrane for Air Purification

AbstractThe potential of a biodegradable polylactic acid (PLA)‐TiO2 membrane for air purification is investigated, utilizing the environmentally friendly solvent Cyrene. Through the integration of TiO2 nanoparticles within a PLA matrix, the membrane is used to degrade ethanol as a model volatile organic compound (VOC) under UV light. Scanning Electron Microscopy (SEM), Energy Dispersive X‐ray Analysis (EDX), and UV–vis spectrophotometry confirm the porous structure of the membrane, the even distribution of TiO2, and its effective band gap of 3.06 eV, respectively. Ethanol adsorption is best described by the Langmuir isotherm model, suggesting monolayer coverage on a homogeneous surface. Photocatalytic tests demonstrate that the membrane decomposes ethanol (6800 ppm) within 14 min under UV light, generating acetaldehyde, acetic acid, formaldehyde, and formic acid as intermediates, and ultimately producing CO2 and water. Reusability tests indicate a decrease in decomposition time over successive cycles due to increased TiO2 exposure from the gradual degradation of PLA. However, this degradation poses challenges for continuous use, compromising the membrane's long‐term durability.

Selective adsorption of gold ion in wastewater with competing cations by novel thiourea-reduced graphene oxide

In this study, selective adsorption experiments of Au were carried out using graphene oxide (GO) and thiourea-reduced GO (TU-rGO). Adsorption experiments using Au, Cu, Pb, and Zn were performed with GO and TU-rGO in order to selectively adsorb Au from simulated waste electric and electronic equipment leachate or printed circuit board wastewater. Optimal adsorption conditions were determined, adsorption isotherm models were fitted, and desorption and regeneration experiments were performed. Additionally, GO and TU-rGO were characterized to better understand the material and propose the adsorption and desorption mechanisms for TU-rGO. It was found that TU-rGO could selectively adsorb Au, achieving a high efficiency of 95‒99% at initial Au concentrations of 0.1‒10 mg L−1 with little to no adsorption of Cu, Pb, and Zn. Moreover, the desorption efficiency of Au by ammonium thiosulfate reached 94% with the adsorption efficiency of TU-rGO decreasing from 99 to 78% after five adsorption and desorption cycles. Isotherm adsorption experiments indicated that the Langmuir model better fitted the adsorption of Au than the Freundlich model. This implied that the adsorption process was mainly controlled by monolayer coverage, with a high Au adsorption capacity of approximately 833 mg g−1 for TU-rGO.

Fabrication of electrospun ion exchanger adsorbents with morphologies designed for the separation of proteins and plasmid DNA

Electrospun cellulose adsorbents are an emergent class of materials applied to a variety of bioprocess separations as an analogue to conventional packed bed chromatography. Electrospun adsorbents have proven to be effective as rapid cycling media, enabling high throughput separation of proteins and viral vectors without compromising selectivity and recovery. However, there is a current lack of knowledge in relation to the manipulation and control of electrospun adsorbent structure with function and performance to cater to the separation needs of emerging, diverse biological products.In this study, a series of electrospun cellulose adsorbents were fabricated by adjusting their manufacturing conditions. A range of fiber diameters (400 to 600 nm) was created by changing the electrospinning polymer solution. Additionally, a range of porosities (0.4 to 0.7 v/v) was achieved by varying the laminating pressures on the electrospun sheets. The adsorbents were functionalized with different degrees of quaternary amine ligand density to create 18 prototype anion exchangers. Their morphology was characterized by BET nitrogen adsorption surface area, X-ray computed tomography, capillary flow porometry and scanning electron microscopy measurements.The physical characteristics of the adsorbents were used in an adapted semi-empirical model and compared to measured permeability data. Permeabilities of prototypes ranged from 10−2 to 10−4 mDarcy. The measured data showed good adherence to modelled data with possible improvements in acquiring wet adsorbent characteristics instead of dried material. Finally, the electrospun adsorbents were characterized for their binding capacity of model proteins of different sizes (diameters of 3.5 nm and 8.9 nm) and plasmid DNA. Static binding capacities ranged from 5 mg/ml to 25 mg/ml for the proteins and plasmid DNA and showed <20 % deviation from monolayer coverage based on BET surface area. Therefore, it was concluded that the electrospun adsorbents most likely adsorb monolayers of proteins and plasmid DNA on the surface with minimal steric hindrance.

Binding energies of CD4 and fragment species to Pt(111): Implications for measurements of anion electron stimulated desorption.

We consider the electron stimulated desorption, via dissociative electron attachment, of anionic species from thin condensed CD4 films deposited on a Pt substrate and compare experimentally observed desorption yields with density functional theory calculations of the binding energies of various anionic and neutral moieties to Pt(111). Certain species (which can be considered chemisorbed) exhibit very high binding energies and large charge transfer with the substrate. Other "physisorbed" species have much lower binding energies. Species that chemisorb have lower desorption yields than those that physisorb, especially at 1-2 monolayer coverage of the Pt substrate. The binding energy of D- to Pt is the weakest, and experimentally, the desorption yield is the highest regardless of the thickness of CD4. The calculations show that the formation and desorption of anionic species at a distance of 16Å from the substrate, which is equivalent to the thickness of CD4 films of four monolayers, are not influenced by the short-range interactions between the substrate and the molecule and DEA products.

Surface anchoring requirements for vanadia clusters on titanium oxide surfaces and their impact on activity for oxidative dehydrogenation of ethanol

Titanium oxide site requirements for the anchoring of catalytically active forms of dispersed vanadia species are investigated. Using a series of oxygen-modified titanium nitride materials, we systematically modify the available vanadia-anchoring moieties on the titanium-bearing support surface. This strategy in turn results in a very narrow size distribution of well-dispersed vanadia clusters anchored on the support. This synthesis technique ensures that only highly dispersed vanadia is present on the catalyst surface even at nominal monolayer coverages. A deeper insight into the catalytic behavior for ethanol partial oxidation of the active vanadia species is obtained by comparing intrinsic kinetic and thermodynamic parameters of kinetically relevant reaction steps (heat of ethanol adsorption, hydrogen abstraction activation energy, and the energetics of catalyst reoxidation). It is found that these parameters are dependent on the relative amount of oxygen in the titanium-bearing support and the resulting distribution of vanadia species, which validates the premise of a potential participation of lattice oxygen atoms of the titania support into the catalytic activity of active vanadia species.

STUDY ON THE CO\(_2\) ADSORPTION PROPERTIES OF ACTIVATED CARBON PRODUCED FROM CORN COB

Activated carbon (AC) prepared from corn cobs was used as an adsorbent for CO2 capture under different temperatures. The characterization by Boehm titration and TGA showed that the total acidic groups of AC were significantly higher than the total basic groups, and the increasing activated temperature resulted in increases in the total basicity and decreases in the total acidity. The CO2 adsorption behavior of AC was predicted by four isotherm models. It was found that the suitable order was Sips &gt; Tóth &gt; Freudlich &gt; Langmuir. The maximum monolayer coverage capacity and isosteric heat of adsorption were in the range of 6.28 - 10.92 mmol g-1 and 26.48 - 21.55 kJ mol-1, respectively. High specific surface area and high amount of carboxylic groups were found to be in favor of CO2 capture.

The effective treatment of dye-containing simulated wastewater by using the cement kiln dust as an industrial waste adsorbent

This study compares the adsorption behavior of both Methylene Blue (MB) and Congo Red (CR) dyes on the surfaces of cement kiln dust (CKD) powder from the experimentally simulated wastewater solution. The cement kiln dust powder was characterized using X-ray Fluorescence (XRF), X-ray diffraction (XRD), N2 adsorption–desorption Brunauer–Emmett–Teller (BET), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM) tests. The adsorption for such dyes was studied under varying mixing contact times, temperatures, and pH as well as various initial concentrations of both dyes and adsorbent using the batch mode experiments. Pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were applied, and the results revealed that the pseudo-second-order fitted well to the kinetic data. Thermodynamic parameters stated that the adsorption process was endothermic. Studying Linear and nonlinear forms of Langmuir and Freundlich's adsorption isotherms revealed that the adsorption process was followed by both homogeneous mono-layer and heterogeneous multilayer coverage on the active sites of cement kiln dust particles. The data showed that the adsorption capacities of the methylene blue and Congo red dyes were 58.43 and 123.42 mg/g, respectively and cement kiln dust is an adsorbent with little cost for the treatment of wastewater.

Acid Treatment on Bentonite Clay for the Removal of Fast Green FCF Dye from Aqueous Solution

ABSTRACTThe bentonite clay has been activated by acid treatment and utilized as a lower‐cost and eco‐friendly adsorbent required to remove Fast Green FCF dye from the aqueous solution. At first acid activated bentonite clay minerals were analyzed by various analytical techniques like Fourier Transform Infrared Spectroscopy (FTIR), x‐ray diffraction (XRD), and x‐ray fluorescence (XRF) analysis. The batch adsorption research was performed to investigate the Fast Green FCF dye adsorption onto the acid‐treated (Bent) bentonite clay. Sorption studies investigated the impacts of adsorbent dosage, initial pH, and time of contact on Fast Green FCF color elimination. The adsorption capacity decreased as the pH was above 7 and then remained almost the same after a pH value of 9. At acidic conditions (below pH value 7), the capacity of adsorption diminished by a decrease in the pH of the solution. The results indicated that the maximum capacity of adsorption has been obtained at an adsorbent dosage of 0.1 g. As the dosage of the adsorbent was improved, several active sites that were available at the time of the dye adsorption increased. As a result, the dye percentage that was removed from the clay increased. Besides these, adsorption kinetics, adsorption equilibrium isotherm, and thermodynamics studies have been also conducted. While studying the adsorption kinetics pseudo‐2nd‐order kinetics has been seen to be more appropriate as compared to pseudo‐1st‐order model. The experimental findings indicated that the attachment of the dye to the clay surface followed the “Langmuir adsorption” isotherm rather than the Freundlich adsorption isotherm with a monolayer coverage of 18.93 mg/g. From the thermodynamics study, it was revealed that the process of adsorption takes place instantly at high temperatures.