Langmuir Isotherm Research Articles

Synthesis of a novel chitosan-TiO2 nanocomposite as an efficient adsorbent for the removal of methylene blue cationic dye from wastewater

This study investigates the efficacy of chitosan-TiO2 nanocomposites (CS-TiO2) as an efficient adsorbent for removing Methylene blue (MB) cationic dye from wastewater. The synthesis of chitosan-TiO2 nanocomposites (CS-TiO2) involved the co-polymerization and crosslinking of Chitosan biopolymer (CS) with titanium dioxide (TiO2). The CS-TiO2 nanocomposites involved their structure, morphology, and characteristics through the utilization of several analytical methods such as FTIR, XRD, SEM, TEM, TGA, UV-visible, DLS, and XPS. The removal of MB dye examined in different concentrations of chitosan exhibits an increase as the pH of the solution increases; the maximum value was attained at pH 6 and 120 minutes of contact time. The optimal dosage of CS-TiO2 nanocomposites for adsorbing methylene blue (MB) was found to be between 0.10 mg/L and 0.20 mg/L. The experimental data was evaluated using the thermodynamic process, Dubinin-Radushkevich, Langmuir, and Freundlich isotherm models. The data were examined using various kinetic models and found to be consistent with pseudo-first order, pseudo-second order, and Intraparticle diffusion kinetics models. Desorption and reuse after adsorption of MB onto CS-TiO2 nanocomposite was investigated using different desorbing agents like NH4OH/NH4Cl or NaOH. These results indicate that CS-TiO2 nanocomposite is a highly effective and cost-effective adsorbent for removing MB dyes from contaminated water.

Removal of contaminants from river Jakara using iron oxide nano particles prepared from Citrullus lanatus fruit waste

Achieving sustainable development requires efficient waste water treatment. Green synthesized iron nanoparticles have attracted much attention as potential catalysts for water remediation in view of their lost cost, high reactivity and good adsorption capacity. This study investigated the applicability of iron oxide nanoparticles synthesized from Citrullus lanatus fruit waste (IONP) in the remediation of contaminated water samples that were collected from River Jakara in Kano State Nigeria. The prepared nanoparticle was characterized using Brunauer–Emmett–Teller (BET) surface area, Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and Thermogravimetric Analysis (TGA). The BET results revealed that IONP have large surface area and are nanometer sized particles. SEM analysis indicated that the adsorbent contain microsphere which might have facilitated the efficient purification of the river water while TGA study revealed that the adsorbent exhibited a three step decomposition process. Data obtained from XRD indicated that the synthesized adsorbent is of high purity and crystalline in nature with an average particle size of 17 nm. Results obtained after treatment of the river water with the adsorbent gave enhanced values of Total Dissolved Solids, Turbidity, Chemical Oxygen Demand, Dissolved Oxygen, phosphate and pH; thus confirming the high adsorption ability of the prepared nanoparticles. The percentage removal of Ni(II) Pb (II) and Cd (II) ions in the river water by IONP was found to depend on adsorbent concentration, agitation time and pH. The adsorption process of these metal ions onto the adsorbent was best described by the Langmuir isotherm model and followed pseudo second order kinetics. The regeneration stability of the adsorbent was adequate when treated with the heavy metals ions at optimum conditions. The nanoparticle synthesized from Citrullus lanatus waste was found to be an efficient and environmentally friendly alternative for treatment of contaminated water.

Batch adsorptive removal of Cr (VI) from aqueous phase using magnetic activated carbon nanocomposite prepared from walnut shells by ZnCl2-FeCl3 activation

ABSTRACT This work aims to assess the physicochemical and adsorptive ability of magnetic activated carbon nanocomposites (MACN) developed from walnut shells (WS) through single-step and dual-step preparation routes utilising ZnCl2-FeCl3 as an activator and magnetising agent for Cr (VI) elimination from the aqueous phase. Synthesis of MACN via a one-step route (MACN1) was achieved through direct activation of WS with ZnCl2-FeCl3. In contrast, the preparation of MACN by dual-steps route (MACN2) was accomplished by carbonising WS at 450°C for 1 h, followed by ZnCl2-FeCl3 activation of the resulting biochar. The N2-adsorption-desorption isotherms, X-ray diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive X-ray (EDX), Transmittance Electron Microscope (TEM), Fourier Transform Infra-Red spectroscopy (FTIR), and Vibrating Sample Magnetization (VSM), were implemented to characterise the MACN samples. BET surface area of MACN1 was 1780.20 m2/g with an average pore diameter of 1.95 nm compared to 283.62 m2/g and 1.91 nm for MACN2. The VSM, FESEM, and TEM measurements ensured the presence of iron oxide nanoparticles on the surface of the composites. Investigating various operating parameters disclosed that the highest adsorptive elimination (AE) of Cr(VI) from its aqueous phase by MACN1 was 99.66% compared to 97.43% for that achieved using MACN2. The adsorption results were best fitted to the Langmuir isotherm using both composites with maximum adsorption capacity of 233.12 mg/g for MACN1 compared to147.55 mg/g for MACN2, suggesting that the adsorption is homogonous and chemical. Moreover, the pseudo-2nd-order kinetics model exhibited the best match for the adsorption of Cr(VI) by both adsorbents, demonstrating that chemisorption was involved in eliminating Cr(VI) from its aqueous phase. After five repetitions, the regeneration experiments confirmed that the MACN adsorbents maintained a high AE. Based on the findings, the as-prepared composites have extensive potential to be applied on the industrial scale.

Remediation of Heavy Metal Pollution from Coal Mine Effluent Using Metal-Organic Frameworks (MOF): Impact of Water Media, Operational Factors and Metal Characteristics

The energy sector is the sector that generates the highest amount of environmental contamination, especially in water sources, mostly in the case of coal-based energy production. The aim of this study was to examine a significant contamination source, heavy metal contamination, in coal mining effluents. The current investigation introduces an MOF platform based on zirconium clusters and isophthalic acid with NH2-MIP-SO3H mixed amine and sulfonic acid functional groups in order to remove the most common heavy metal ions in coal mining effluents, including Hg, Cd, Pb, and Cu ions. The water matrix and the operational conditions were identified to be very influential in the removal process, such as the pH of water, the initial metal concentration and operating time. NH2-MIP-SO3H offers a great removal efficiency of metals starting from 745.83 mg/g for Cd, 673.67 mg/g for Cu, 589.85 mg/g for Hg, and 481.66 mg/g for Pb ions, with the Langmuir equation for equilibrium and pseudo-second-order equation for kinetics being the ideal models to express the equilibrium and kinetic data, respectively. A significant impact of water pH was found to occur, with the NH2-MIP-SO3H platform performing best at pH 6. Reuse of NH2-MIP-SO3H demonstrates excellent reusability, sustaining 90% of initial performance over eight regeneration cycles. The interaction of functional group-functional metal was the dominant mechanism in the removal process. The NH2-MIP-SO3H unique approach to heavy metal removal provides a very hopeful outlook for additional investigations in larger-scale studies.

Adsorption kinetics and thermodynamics of metal complex acid dyes on silk fabric

This study reports the adsorption phenomena of metal complex acid dyes onto silk fabric. Two commercial metal complex acid dyes namely Bestalan Yellow SF and Bestalan Navy SF were adsorbed onto degummed silk fabric. The functional properties and surface morphology of silk fabric were investigated with FT-IR spectroscopy and FE-SEM respectively. The typical absorption band of C = O stretching was found at 1620 cm−1 indicating amide I structure and C-N stretching as well as N-H bending vibrations were observed at 1510 cm−1 suggesting the β-sheet crystallites of amide I and amide II silk proteins. The effectiveness of degumming performance was confirmed by SEM images. The adsorption of dyes by silk fabric was investigated with respect to pH, initial dye bath concentration, and contact time. It was found that the adsorption of dye onto silk fabric was highly influenced by the dye bath pH, initial dye concentration, and contact time. The higher dye adsorption was observed at acidic dye bath condition (pH = 3.5). The adsorption of dye was also increased with the increase of the initial dye bath concentration. The dyes adsorption reached at equilibrium condition after 80 min. The adsorption isotherm and kinetics were also evaluated based on the experimental results. The adsorption pattern fitted well to the Langmuir adsorption isotherm with high correlation coefficient (R 2>0.97) for both dyes. The kinetic parameters suggested that the pseudo-second-order model is more suitable compare to the pseudo-first-order model considering the higher regression coefficients ( R 2 = ∼ 0.99 ) . The maximum adsorption of Bestalan Yellow SF and Bestalan Navy SF was found to be 232.5 and 222.2 mg/g respectively. The thermodynamic data were studied at 25, 40 and 60 °C. The change of Gibbs free energy of the system was positive indicating the spontaneous nature of the adsorption. The values of ΔH (-4.68 kJ/mole −3.65 kJ/mole) suggested the exothermic environment and the negative values of ΔS (-0.035 and −0.034 kJ/mole/k) advocated the good interaction between the metal complex acid dyes and silk fabric. The Langmuir adsorption model and pseudo-second-order kinetic suggested that the dyeing of metal complex acid dyes on silk fabric was controlled by ion-exchange chemical reaction.

Comparison between synthetic and natural clinoptilolites for adsorptive removal of metal ions

The present work evaluated the removal performances of Ni2+, Cd2+, Sr2+, Mn2+, and Fe3+ from an aqueous solution using a comparison between synthetic clinoptilolite (SCP) and natural CP (NCP). Unlike previous demonstrations that treated each metal ion individually, these five metal ions and the used adsorbents were combined in a single treatment and explored via various characterizations, such as XRD patterns, SEM images, N2 sorption isotherms, ICP, and AAS analysis. The results revealed that the capacities of SCP at pH 3.0–8.0 and 25–75 °C were nearly 20 times higher than those of NCP, showing 2000, 1720, 1875, 1510, and 22 mg g−1, for Ni2+, Fe3+, Cd2+, Mn2+, and Sr2, respectively. The reason is mostly attributed to its purity and perfect crystal lattice. The kinetic behaviors in both cases indicated that the pseudo-2nd-order model provided a better description. Their adsorption behaviors exhibited a better fit with the Freundlich models on the removal of Ni2+, Cd2+, and Mn2+, the Langmuir equation on the removal of Fe3+, and both Freundlich and Langmuir on the removal of Sr2+, respectively. The thermodynamic findings indicated that the SCP was used to be faster, more spontaneous, and had a better favorable adsorption performance than the NCP. Additionally, five times recyclability and different stability tests further supported the dominant adsorbent nature of using SCP as an adsorbent.

Optimizing methylene blue adsorption conditions on hydrothermally synthesized NaX zeolite through a full two-level factorial design.

Besides being hazardous to humans and aquatic organisms, dyes present in water reservoirs limit sunlight's availability to aquatic plants and animals, making significant impact on their growth and development. Herein, the adsorptive removal of methylene blue (MB) dye from aqueous solution using type X (NaX) zeolite by full experimental design 2 n was studied. The physical and chemical properties of NaX zeolite were identified using various characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray (SEM-EDS), Fourier transform infra-red (FT-IR), and Brunauer-Emmett-Teller (BET) surface area analyses. Results confirmed that NaX zeolite had a cubic shaped crystalline structure with 2-4 μm size and high (375 m2 g-1) specific surface area, having 90% optimal adsorption efficiency. Langmuir and Elovich isotherm models were best fitted to adsorption experimental data and a pseudo-second-order kinetic model describes well the adsorption kinetic data. Akaike information criteria (AIC) was used to assess the best fitted models on the experimental data. A thermodynamic study reveals that the MB adsorption onto NaX was exothermic, spontaneous, and feasible.

Enhanced adsorption of ciprofloxacin from an aqueous solution using a novel CaMgAl-layered double hydroxide/red mud composite

This work reports on CaMgAl-layered double hydroxide (LDH) based red mud (RM) composite prepared via a co-precipitation method, characterized by transmission electron microscopy (TEM), powder X-ray diffraction patterns (XRD), field-emission scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Brunauer-Emmett-Teller analysis (BET), and Fourier transform infrared spectra (FTIR) and subsequently used for elimination of ciprofloxacin (CIP) from an aqueous solution in batch mode experiments. Langmuir isotherm model provided a better fit of CIP adsorption onto CaMgAl/RM composites than a Freundlich isotherm model; indicating a monolayer adsorption phenomena. Pseudo-second-order kinetic models describe the kinetics of adsorption while the adsorption mechanisms were controlled by external mass transfer and intra-particle diffusion. Thermodynamic analysis indicated that the CIP adsorption onto CaMgAl-LDH/RM was exothermic and spontaneous in nature. The prepared adsorbent exhibited superior affinity towards CIP adsorption which yielded a maximum CIP adsorption capacity of up to 138 mg/g. The higher removal efficiency (89.45 %) was reached under the best conditions (pH 7, agitation speed 150 rpm, adsorbent dosage 0.5 g/100 ml, concentration of contaminant 70 ppm, and 90 min contact time). Moreover, the synthesized adsorbent can be recovered after six consecutive regeneration cycles with a minimal reduction in the adsorption ability of 31 %. In conclusion, this study demonstrated that the CaMgAl-LDH/RM composite could be a promising adsorbent for removing antibiotics from wastewater.

Utilizing Chamaerops humilis in removing methylene blue dye from water: an effective approach.

Removing dyes, particularly methylene blue, from wastewater is crucial due to their detrimental effects on environmental and human health. Adsorption, recognized as a simple and efficient technique, is frequently employed to eliminate various dyes from water. Although activated carbon is a favored adsorbent for wastewater treatment, its high cost often restricts its use. As a result, there is increasing interest in utilizing inexpensive, natural materials, and waste products as alternative adsorbents. Sawdust from the European fan palm tree, specifically Chamaerops humilis, a widely available and cost-effective by-product, has demonstrated effective dye removal from wastewater. This study explored the impact of various factors such as time, agitation, adsorbent quantity, dye concentration, pH, and temperature on the adsorption of methylene blue using Chamaerops humilis sawdust. Optimal dye adsorption conditions were identified at a temperature of 25 °C, a pH of 8, an adsorbent dosage of 100 mg, a contact time of 120 min, and a dye concentration of 20 mg L-1, achieving a removal efficiency of 93.5%. Moreover, the Langmuir isotherm model described the adsorption dynamics more accurately, suggesting a maximum sorption capacity of 22.7 mg g-1 for the sawdust. Additionally, adsorption kinetics aligned better with the pseudo-second-order model than the pseudo-first-order model, underscoring the efficacy of this method in treating dye-polluted water.

Investigation of adsorption potential of waste jewelry meerschaum powder for Cu(II) and cationic dye

The presence of heavy metals and pollutant dyes can have detrimental effects on aquatic ecosystems and compromise aquatic aesthetics. This study investigates the use of unprocessed waste gem meerschaum powder as a new adsorbent in the removal of both Cu(II) and methylene blue (MB) from aqueous solutions to reduce water pollution. The structure of the waste powder was characterized by FT-IR, XRD, SEM and BET methods. Optimization of Cu(II) and MB dye removal was carried out using design of experiment technique. Under optimum conditions, remarkable removal efficiencies of 95.5% (± 3.7) for Cu(II) and 97.8% (± 0.4) for MB were achieved. The removal of Cu(II) followed the Freundlich isotherm model, while the removal of MB dye adhered to the Langmuir isotherm model. Both adsorption processes obeyed the pseudo-second-order kinetic model and occurred spontaneously. This innovative approach offers a promising solution to water pollution by highlighting the importance of sustainable and cost-effective waste use.

The efficient elimination of lead ions from aqueous solution using MgCuAl-Layered double hydroxides@montmorillonite composite: A kinetic, isotherm and statistical analysis

In this study, a MgCuAl-layered double hydroxide (MCA-LDH)-based montmorillonite cationic clay (MMT) composite was synthesized via a co-precipitation method and then characterized using various analytical techniques, including BET surface area, TEM, XRD, FT-IR, and SEM/EDS analysis, to confirm the successful loading of LDH onto MMT. The material was subsequently used as a novel adsorbent for Pb2+ ion removal from aqueous solution in batch mode experiments. The effects of important variables on Pb2+ adsorption were investigated, and the values of these variables were optimized using the central composite design (CCD) of the response surface methodology (RSM). The results showed that the favorable conditions for the adsorption of Pb2+ onto the MCA-LDH@MMt composite were pH 5, an initial Pb2+ concentration of 85 mg/l, and an adsorbent dose of 0.225 g/100 ml. Under these conditions, the maximum adsorption efficiency was 89.1%. Using the RSM methodology, a quadratic polynomial equation was obtained that expresses the relationship between the adsorption efficiency and the effective parameters. The results show that pH and temperature had a greater effect on the adsorption efficiency. The pseudo-second-order model kinetically well fitted the adsorption process, while external mass transfer and intra-particle diffusion controlled the adsorption mechanics. The Langmuir isotherm model fitted the isotherm to the adsorption process, yielding a capacity of 132.83 mg/g. The thermodynamic study showed that the spontaneous adsorption of Pb2+ onto MCA-LDH@MMt composites is exothermic in nature. Moreover, there was a mere 30% reduction in the removal efficiency after five consecutive regeneration cycles. In conclusion, this work demonstrated that the MCA-LDH@MMt composite could be a promising adsorbent for the treatment of aqueous solutions contaminated with heavy metals.

Polymer-assisted synthesis of ternary magnetic graphene oxide nanocomposite for the adsorptive removal of Cr(VI) and Pb(II) ions

The presence of chromium [Cr(VI)] and lead [Pb(II)] ions in the water bodies have adverse effects on humans and aquatic life. Graphene oxide-based magnetic nanocomposites synthesized in the presence of chitosan (mGO/CS) or polyaniline (mGO/PA) as potential adsorbents for the removal of Cr(VI) and Pb(II) ions. The FTIR (Fourier transform infrared spectroscopy), EDX (Energy dispersive X-ray), XRD (X-ray diffraction) and SEM (Scanning electron microscopy) were employed to investigate the chemical composition, structural, elemental analysis, crystalline size and morphology of the nanocomposites. The FTIR results confirmed the synthesis of the nanocomposites by detecting peaks of specific functional groups. The average crystallite sizes of the mGO, mGO/CS, and mGO/PA nanocomposites were 17, 25, and 23 (nm), respectively, as determined by the Debye-Scherrer equation from the XRD data. Batch adsorption experiments were conducted for Pb(II) and Cr(VI) removal by varying the variables like pH, concentration of metal ions and contact time. The Box Behnken design (BBD) was used to optimize the adsorption parameters. Under the optimum conditions, mGO/CS and mGO/PA showed maximum removal percentages (%R) of 92.36 and 98.7 for Pb(II), and 85.25 and 93.08 for Cr(VI), respectively. The adsorption capacities were 110.84 and 118.44 mg/g for Pb(II), and 87.74 and 111.7 mg/g for Cr(VI) were obtained for mGO/CS and mGO/PA, respectively. The pseudo-second-order kinetic model and Langmuir isotherm fitted well to the experimental data and explain the adsorption mechanism of the nanocomposite materials for both metal ions.

Experimental and computational explorations for the inhibitive performances of synthesized green surfactants against the corrosion of copper in nitric acid

The inhibitory characteristics of two recently synthesized biosurfactants based on amino acids, namely sodium N-hexadecyl glycine (I) and sodium N-hexadecyl valine (II), concerning copper corrosion in 1.0 M HNO3 were studied at variance of temperatures. FTIR analysis was utilized to identify the chemical structures of both synthesized biosurfactants. Various techniques were employed in this study. According to the results, the synthesized biosurfactants were played as proficient inhibitors for copper corrosion and their inhibition efficiencies (% IEs) were concentration- and structure-dependent with respect to them. At a concentration of 400 mg/L of the synthesized biosurfactants and at 298 K, the average% IE was found to be 90% for biosurfactant I and 85% for biosurfactant II. The gained higher% IEs were suggested to as a result of the potent adsorption of these biosurfactants on the surface of copper and the type of adsorption was discovered to be physical and followed Langmuir adsorption isotherm. The obtained findings signified that the synthesized biosurfactants exhibited mixed-type and interface-type inhibitors. The thermodynamic and kinetic parameters were assessed and discussed. Furthermore, the kinetics of corrosion of copper as well as its inhibition were also investigated. The density functional theory (DFT) and molecular dynamics (MD) simulations emphasized the inhibitory mechanism of the examined biosurfactants and proved the adsorption of the biosurfactants’ molecules on the copper surface. Theoretical modeling also demonstrated that the biosurfactant I exhibited a greater% IE compared to biosurfactant II. The experimental results gained from all employed measurements are largely reliable with each others and are in a good consistent with the theoretical studies signifying the validity of these results.

Adsorptive Removal of Famotidine Drug from Aqueous Medium by Ocimum Basilicum

AbstractThe present study investigated the potential of basil seeds as adsorbent in order to remove famotidine drug from aqueous media. The optimum conditions for the adsorption of famotidine on the basil seeds were found to be 50 min contact time, 50 °C temperature, pH 1, 100 ppm concentration of famotidine, 0.03 g adsorbent mass and 50 rpm agitation rate. Pseudo 2nd order kinetics with a higher correlation coefficient (R2=0.9942) suggested chemisorption as preferable mechanism of adsorption. However, the enthalpy of adsorption (ΔH=+33.67 KJ/mol) was less than that of chemisorption but higher than that of physisorption which was attributed to strong hydrogen bonding between famotidine molecules and basil seed surface. The Langmuir isotherm with higher R2 (0.9960) than Freundlich isotherm (R2=0.8798) predicted maximum adsorption capacity (qm) of 99 mg/g while suggesting monolayer and favourable adsorption. The adsorption was endothermic (+ΔH) and spontaneous (−ΔG) in nature. The FT‐IR spectroscopy confirmed that famotidine was adsorbed on basil seed via strong hydrogen bonding. The study proposed that the simultaneous intake of famotidine and basil seeds should be strictly avoided as the drug readily adsorbs on basil seeds in acidic environment (gastric pH) thereby reducing its curing effect.

Highly effective removal of basic fuchsin dye using carboxymethyl konjac glucomannan grafted acrylic acid-acrylamide/montmorillonite composite hydrogel

This study developed a nanocomposite hydrogel, CAM4-MMT, for efficiently removing basic fuchsin dye from water. The hydrogel was prepared by grafting a copolymer of acrylic acid (AA) and acrylamide (AM) onto carboxymethyl konjac glucomannan (CMKGM), and doped with montmorillonite (MMT), exhibited excellent thermal stability, a porous inner structure, large specific surface area (1.407 m2/g), and high swelling capacity (107.3 g/g). The hydrogel achieved a maximum adsorption capacity of 694.1 mg/g and a removal rate of 99.5 %. The Langmuir isotherm and pseudo-second-order kinetic model best described the adsorption process. Regeneration and reuse tests confirmed that the hydrogel has excellent recyclability. In conclusion, the CAM4-MMT composite hydrogel efficiently removed basic fuchsin from water solutions, offering a new scheme for eliminating basic fuchsin using natural polysaccharides with promising applications.

Removal of Thiophenol from Water Using Sepiolite

Crude oil and petroleum products contain various types of sulfur compounds: aliphatic and aromatic mercaptans, hydrogen sulfide, sulfides, disulfides, thiophene derivatives, etc. Some of these may dissolve in water only slightly, but their toxicity and corrosiveness indicate that even these small amounts should be eliminated from water. This work examines, for the first time, the removal of thiophenol (synonyms: benzenethiol, phenyl mercaptan) from water using sepiolite. This clay mineral (evaluated by SEM analysis) is an attractive natural sorbent characterized by its microporosity, which results from its crystalline structure and large specific surface area. Because the structure of thiophenol changes depending on the pH of the aqueous solution (due to the loss of a proton), the research was conducted at pH 4, 7 and 9. The detection of thiophenol in aqueous solution was investigated using UV spectroscopy. It was found that the adsorption of thiophenol is possible, but it occurs only in an acidic environment (pH 4). No sorption is observed at pH 7 or 9. The adsorption of thiophenol at pH 4 does not change significantly after changing the ionic strength of the aqueous solution (distilled water, 0.01 NaCl and 0.1 NaCl). The adsorption capacity of sepioliteis approximately 0.23–0.34 mg/g. Studies using infrared spectroscopy and fitting of Freundlich and Langmuir isotherm models to the results of adsorption experiments indicate that adsorption on unmodified sepiolite follows a physisorption mechanism. Additionally, to understand the behavior of thiophenol in the presence of sepiolite across different pH ranges, DFT/PCM/B3LYP/Aug-CC-pVDZ calculations were used to analyze the charge distribution on particular atoms in its structure.

Study on the adsorption performance of zeolite imidazole frameworks materials for Co(II) and Mn(II) in solution

Abstract The radionuclides 60Co and 54Mn are the main activation products produced in the operation of nuclear power facilities. Wastewater with these radionuclides must be treated to meet standards before being discharged. A variety of zeolite imidazole frameworks (ZIFs) materials were synthesized at room temperature, and the adsorption effect of ZIF-67 was found to be the best through adsorption experiments on Co(II) and Mn(II). The thermal stability test and structural characterization of ZIF-67 were carried out. At the same time, the influence of the initial pH value, adsorption time, and initial concentration of the solution on the adsorption of Co(II) and Mn(II) by ZIF-67 was investigated. The results show that: ZIF-67 has a microporous structure with a BET surface area of 1,035.72 m2/g. In addition, ZIF-67 has good thermal stability, under the condition of pH = 6, a temperature of 303 K and the initial concentration of 500 mg/L. The saturated adsorption capacity for Co(II) and Mn(II) reached 230.25 mg/g and 338.75 mg/g, respectively. ZIF-67 exhibits good selective adsorption performance for Co(II) and Mn (II) in high concentration interfering ion solutions and multi-ion solutions. The adsorption process of ZIF-67 was analyzed by kinetics, thermodynamics, isotherms, and adsorption diffusion models. The analysis of thermodynamic parameters shows that the adsorption process of ZIF-67 to Co(II) and Mn(II) is spontaneous and endothermic. The pseudo-second-order kinetic model, Langmuir isotherm model, and Boyd model are more in line with the adsorption process of Co(II) and Mn(II) by ZIF-67. It shows that the active sites on the surface of ZIF-67 are evenly distributed, and the adsorption process is single-molecule chemical layer adsorption. In addition, the liquid film diffusion dominates the adsorption rate during the adsorption process of Co(II) and Mn(II) by ZIF-67.

Alkaloid extract of seed Citrullus colocynthis as novel green inhibitor for mild steel corrosion in one molar HCl acid solution: DFT and MC/MD approaches

The study was designed to explore the corrosion prevention capabilities of Citrullus colocynthis seeds alkaloid-rich extract (CSEA) on MS in a 1 M HCl environment by use of electrochemical and theoretical methods. Notably, Electrochemical Impedance Spectroscopy (EIS) and potentiodynamic polarization were used to probe the impact of immersion time and temperature. Energy-dispersive X-ray spectroscopy (EDX) and spanning electron microscopy (SEM) were used to confirm the presence of a protective layer on the substrate surface. Density functional theory (DFT) method was used to optimize the investigated species by use of B3LYP/6–31 + G(d, p) level of theory. The global and local quantum chemical reactivity descriptors were calculated to explore the inhibition corrosion efficiency and to identify the most favorable sites for electrophilic and nucleophilic attacks. Monte Carlo (MC) and molecular dynamics simulation (MDS) methods were used to study the interactions between corrosion inhibitor and metal surface. Noteworthy, results showed that CSEA exhibited an impressive inhibition efficiency, which reached 94.3% with a concentration of 2 g/L at 298 K. Potentiodynamic polarization revealed that the extract acted as a mixed-type inhibitor. Nyquist graphs showed that charge-transfer resistance and dæouble-layer capacitance both rised with increasing CSEA concentration, suggesting better inhibition efficiency. Notably, the Langmuir adsorption isotherm is well-aligned with the adsorption of inhibitor compounds. Importantly, all aforementioned theoretical methods were in agreement with the experimental findings. The outcome of the present work supported using Citrullus colocynthis seeds alkaloid-rich extract as ecofriendly agents to prevent corrosion.

Hydrothermal synthesis of pore-expanded hydroxyapatite for enhanced Cu2+ adsorption from aqueous solutions

This paper describes the hydrothermal synthesis of a pore-expanded hydroxyapatite (PE-HAp) from fine–grained calcareous sludge using a cetyltrimethylammonium bromide (CTAB) as a template and 1,3,5-trimethylbenzene (TMB) as a pore expander for the removal of Cu2+ ions from aqueous solutions. The PE-HAp was characterized using XRD, SEM, DTA/TGA and BET surface analysis. Adsorption behavior was assessed using Langmuir, Freundlich, Dubinin–Radushkevich, Temkin and Sips isotherms. In a solution with an initial Cu2+ concentration of 200 mg L-1 and a pH of 5.0, the highest Cu2+ removal efficiency was achieved using PE-HAp synthesized at a hydrothermal temperature of 180 °C at a concentration of 15 g/L over a period of 60 min. Using Langmuir isotherms, the highest single-layer adsorption capacity value was 9.90 mg g-1. Gibbs free energy (ΔG°), changes in enthalpy (ΔH°), and changes entropy change (ΔS°) revealed that the adsorption of Cu2+ on PE-HAp was spontaneous and exothermic. The PE-HAp synthesized in this study is a promising material for the removal of Cu2+ from aqueous solutions.

Rapid production of hydroxysodalite from a clay-based waste through microwave-assisted technique for treatment of wastewater contaminated with zinc cation

In the current work, the cabbage-like hydroxysodalite powder was produced from a clay-based waste deposited in the landfill of raw vegetable oil refinery through the microwave-assisted technique to treat the wastewater discharged from a zinc extraction industry. The selected waste was a Ca-bentonite, mainly containing montmorillonite, illite, and kaolinite which contaminated with the vegetable oil components. The effects of microwave irradiation power, and time on crystalline structure of products as well as uptake of heavy metal ions like zinc, cadmium, nickel, and aluminum were studied in details. The experimental results showed that the partial recrystallization of hydroxysodalite under the irradiation power of 200 W within 10–15 min contributes to the enhancement of adsorption efficiency. The maximal uptake of heavy metal ions was obtained in the relative crystallinity range of 22.5–43.0%. The prepared adsorbent possessed the higher efficiency, 94.0%, for the immobilization of Zn2+ from the concentrated wastewater, 413 mg L−1. The competitive adsorption of Cd2+, Ni2+, and Al3+ ions over the hydroxysodalite was extremely dependent on the ion concentration. Furthermore, the adsorption kinetics of Zn2+ over the hydroxysodalite particles follows the pseudo-second-order (PSO) model, indicating the chemical nature of treatment process. The equilibrium data were fitted by the Langmuir isotherm, confirming the homogenous, and monolayer adsorption. The presented route for the production of hydroxysodalite is facile, and rapid in comparison to hydrothermal method.