Langmuir Isotherm Research Articles

Utilization of macadamia nutshell-derived activated carbon for enhanced congo red adsorption

This study addresses the challenge of removing Congo red (CR) from aqueous solutions using activated carbon (AC) derived from macadamia nutshells (MNS). A unique two-step carbonization and pyrolysis process was employed to produce MNS-AC with high surface area and porosity. Key experimental variables, including initial CR concentration, contact time, and pH, were systematically varied in batch mode. Results indicated that the modified AC achieved significantly higher removal percentages compared to unmodified charcoal. At pH 2.0 and an initial dye concentration of 50 mg L−1, CR removal reached 97.48 % for MNS-AC3. The maximum adsorption capacity (qmax) of 58.29 mg g−1 was observed at an initial dye concentration of 200 mg L−1. The pseudo-second-order kinetic model closely matched the experimental data, and equilibrium data analysis using Langmuir and Dubinin-Radushkevich (D-R) isotherm models provided excellent fits. This research demonstrates the potential of using industrial biomass waste to develop sustainable solutions for dye removal in wastewater treatment.

A Study on the Corrosion Inhibition Impact of Newly Synthesized Quinazoline Derivatives on Mild Steel in 1.0 M HCl: Experimental, surface morphological (SEM-EDS and FTIR) and computational analysis

Two new quinazoline derivatives were investigated in this research, namely 12-(4-methoxyphenyl) and 3,3-dimethyl-12-(4-nitrophenyl)-3,4,5,12-tetrahydrobenzo[4,5]imidazo[2, 1-b]quinazolin-1(2H)-one (Q-NO2). In 1M hydrochloric acid (HCl), -3,3-dimethyl-3,4,5,12-tetrahydrobenzo[4,5]imidazo[2,1-b]quinazolin-1(2H)-one (Q-OMe) proved to be an extremely effective corrosion inhibitor for mild steel. The maximum inhibition efficiencies of 94.7% for Q-NO2 and 96.7% for Q-OMe were achieved when the performance of the inhibitors was evaluated using potentiodynamic polarization (PDP), electrochemical frequency modulation (EFM) and electrochemical impedance spectroscopy (EIS). According to these findings, the Q-NO2 and Q-OMe molecules have a remarkable ability to generate a dense, resistant protective film on the mild steel surface. This protective film acted as a barrier, effectively blocking the penetration of corrosive ions and their interaction with the mild steel substrate. The adsorption characteristics of these inhibitors on the mild steel surface conform to the Langmuir adsorption isotherm. PDP experiments show that Q-NO2 and Q-OMe act as mixed-type inhibitors for mild steel in 1.0M HCl. Surface characterization by energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) determined that a protective layer had formed on the steel surface, preventing corrosion. The experimental results were corroborated by theoretical insights from density functional theory (DFT), which further clarified the molecular adsorption processes. This work highlights the potential of Q-NO2 and Q-OMe as effective inhibitors to protect mild steel in acidic situation.

Poly(ionic liquids-acrylic acid)-modified MIL-101(Cr) metal−organic frameworks: Preparation and efficient adsorption of europium☆

A novel composite material, Poly(IL-AA)@MIL-101(Cr), combining metal-organic framework, polymeric ionic liquid and acrylic acid, was synthesized for the selective and efficient adsorption of rare earths europium(III) (Eu3+). Characterization of the materials was carried out using techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), thermogravimetric analysis (TGA) and Brunauer-Emmett-Teller (BET). The results demonstrate successful incorporation of the polymeric ionic liquid onto the material surface while preserving the crystal structure and morphology of MIL-101(Cr). Adsorption experiments were conducted to explore parameters including solution pH, initial Eu3+ concentration, and duration, with comprehensive analyses of adsorption kinetics, isotherms, and mechanisms. Findings reveal that Poly(IL1-AA)@MIL-101(Cr), Poly(IL3-AA)@MIL-101(Cr), and Poly(IL5-AA)@MIL-101(Cr) achieve adsorption equilibrium for Eu3+ at approximately 9 h with an equilibrium pH of 6.2. The adsorption of Eu3+ predominantly follows a pseudo-second-order kinetic model and Langmuir isotherm adsorption model. Moreover, the prepared composite material exhibits superior adsorption selectivity for Eu3+ over other metal ions in the mixture (K+, Mg2+, Ni2+, Co2+, Zn2+, La3+, and Nd3+). Even after five adsorption-desorption cycles, the composite material maintains satisfactory adsorption performance.

Experimental and theoretical study of two Salen-type Schiff bases: green synthesis, characterization, corrosion inhibition efficiency, and biological activity

As eco-friendly corrosion inhibitors, antioxidants, and antibacterial agents, this study assesses 1,3-bis(2-hydroxybenzylidene) thiourea (B1) and 1,3-bis(2-hydroxybenzylidene) urea (B2), two new Schiff bases, on their performance in these areas. We successfully synthesized these Schiff bases in just 15 minutes using an environmentally friendly approach, and the yield was rather good, ranging from 69.8% to 87.53%. When compared to B2, B1 showed more effective corrosion inhibition and better antioxidant activity. Both chemicals were highly effective against microbes, while B1 was particularly effective against Aspergillus. B. We measured the weight loss to examine the corrosion inhibition impact of XC48 carbon steel in 1M HCl. The findings revealed that at the ideal concentration of 5.10–4 M, the estimated IE% of the Schiff bases was 63.8% for B2 and 87.28% for B1. This study employed the Langmuir isotherm model to determine a number of thermodynamic and kinetic characteristics, all of which pointed to a physical adsorbed state. Promising electrical characteristics and robust adsorption on metal surfaces for B1 were corroborated by theoretical investigations employing density functional theory (DFT) and molecular dynamics (MD) simulations. Both the theoretical and practical aspects align with one another.

Comparative Study of Cu Ion Adsorption by Nano-Hydroxyapatite Powder Synthesized from Chemical Reagents and Clam Shell-Derived Calcium Sources.

The increasing contamination of water sources by heavy metals necessitates the development of efficient and sustainable adsorption materials. This study evaluates the potential of nano-hydroxyapatite (HA) powders synthesized from chemical reagents (Chem-HA) and clam shells (Bio-HA) as adsorbents for Cu ions in aqueous solutions. Both powders were synthesized using microwave irradiation at 700 W for 5 min, resulting in nano-sized rod-like particles confirmed as HA by X-ray diffraction (XRD). Bio-HA exhibited higher crystallinity (67.5%) compared to Chem-HA (34.9%), which contributed to Bio-HA's superior adsorption performance. The maximum adsorption capacities were 436.8 mg/g for Bio-HA and 426.7 mg/g for Chem-HA, as determined by the Langmuir isotherm model. Kinetic studies showed that the Cu ion adsorption followed the pseudo-second-order model, with Bio-HA achieving equilibrium faster and displaying a higher rate constant (6.39 × 10⁻4 g/mg·min) than Chem-HA (5.16 × 10⁻4 g/mg·min). Thermodynamic analysis indicated that the adsorption process was spontaneous and endothermic, with Bio-HA requiring less energy (ΔH° = 39.00 kJ/mol) compared to Chem-HA (ΔH° = 43.77 kJ/mol). Additionally, the activation energy for Bio-HA was lower (41.62 kJ/mol) than that for Chem-HA (46.39 kJ/mol), suggesting better energy efficiency. The formation of a new Cu2(OH)PO4 phase after adsorption, as evidenced by XRD, confirmed that the Cu ions replaced the Ca ions in the HA lattice. These findings demonstrate that Bio-HA, derived from natural sources, offers environmental benefits as a recyclable material, enhancing heavy metal removal efficiency while contributing to sustainability by utilizing waste materials and reducing an environmental impact.

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.

Zeolite functionalized with macroalgae as novel material for Fe and Mn removal from real acid mine drainage

The treatment of heavy metals such as Fe and manganese Mn remains a critical global issue, necessitating solutions that are not only effective and efficient but also cost- effective and easy to implement. Adsorption has been identified as one of the most efficient techniques for removing heavy metals. This study investigates adsorption method applied to real AMD, characterized by high levels of heavy metal contamination and low pH. Key parameters analyzed include adsorption performance, isotherm and kinetic models, thermodynamic properties, and adsorption characteristics. The adsorbent used was zeolite functionalized with carboxyl, hydroxyl, and sulfate groups derived from macroalgae. Material characterization was conducted using SEM, XRD, and FTIR. The results indicate that zeolite functionalized with carboxyl, hydroxyl, and sulfate groups from macroalgae effectively reduced Fe and Mn concentrations by up to 99 % within just five minutes. Furthermore, the adsorption process followed a pseudo-second-order kinetic model and conformed to the Langmuir isotherm model.

Development and application of a new macrocyclic ligand-functionalized mesoporous silica sorbent for selective separation of radiocesium from environmental wastewater

The growing reliance on nuclear energy and uncharacteristic accidents, such as those in Chornobyl and Fukushima, have emphasized the need for effective radiocesium (r-Cs: 137Cs) removal from environmental wastewater. This study presents the development of DFDB18C6@SBA-NH2, a novel solid-phase sorbent designed to remove r-Cs from aqueous environments selectively. The sorbent was synthesized by tethering a macrocyclic ligand, DFDB18C6 (di-formyl dibenzo-18-crown-6-ether), to amino-functionalized mesoporous SBA-15 (Santa Barbara Amorphous-15). The sorbent’s structure, thermal properties, and surface morphology were comprehensively characterized. Batch sorption experiments were performed to evaluate the influence of different operating factors on r-Cs sorption, including solution pH, contact duration, initial ion concentration, ambient temperature, and matrix ions contents. The sorption behavior was better explained with the pseudo-second-order kinetic and Langmuir isotherm models, which suggest a probable monolayer chemisorption process. The thermodynamic evaluation indicated the exothermic nature of the sorption process. The DFDB18C6@SBA-NH2 sorbent demonstrated significant 137Cs removal (approximately 85 %) from Fukushima-originated wastewater, with competing matrix ions such as Ca2+, Mg2+, Na+, and K+. These results highlight the potential of DFDB18C6@SBA-NH2 as a potential solid-phase sorbent for efficient and selective r-Cs decontamination in waste aqueous matrices.

Optimization of Rhizoclonium hieroglyphicum extract for enhanced synthesis of nickel oxide nanoparticles using response surface methodology and its potential exploration in biological application.

The study investigates the potential of Rhizoclonium hieroglyphicum as a novel source for synthesizing nickel oxide nanoparticles (RH-NiONPs) and evaluates its biological applications. Phytochemicals in the algal extract serve as capping, reducing and stabilizing agent for nickel oxide nanoparticles. The process variables were optimized using BBD based RSM to obtain maximum RH-NiONPs. Characterization of RH-NiONPs using UV-Vis and FT-IR spectroscopy reveals the plasmon resonance peak at 340 nm and the functional groups responsible for reduction and stabilization. XRD confirmed the crystalline nature while the stability and size of the RH-NiONPs were determined by DLS and zeta potential. Toxicity assessments demonstrated the effect of RH-NiONPs against Vigna radiata, Allium cepa and Artemia salina was low. RH-NiONPs revealed significant zone of inhibition against the selected bacteria and fungi. The results of larvicidal activity showed that RH-NiONPs are toxic to 4th instar larvae of Daphnis nerii. Also, RH-NiONPs efficiently decolorized Reactive Violet 13 (92%) under sunlight irradiation and the experimental data well fits to Langmuir isotherm along with pseudo second order kinetic model. The thermodynamic studies enunciate the exothermic and non-spontaneous photocatalytic decolorization of reactive violet 13. Thus, the current study assesses the eco-friendly and cost-effective nature of RH-NiONPs along with its biological applications.

DFT Theoretical Analysis, Experimental Approach, and RSM Process to Understand the Congo Red Adsorption Mechanism on Chitosan@Graphene Oxide Beads

The presence of Congo red in wastewater poses significant environmental and health risks due to its toxic and carcinogenic properties. As a synthetic azo dye commonly used in the textile industry, Congo red is resistant to degradation, leading to persistent contamination in water bodies. The study focused on evaluating the efficacy of novel composite beads made from chitosan and graphene oxide as adsorbents for eliminating Congo Red from water solutions. It systematically examined various experimental factors including initial concentration, pH levels, mass of adsorbent, contact duration, and temperature, aiming to optimize the adsorption process. The composite chitosan graphene oxide beads were analyzed using several techniques, including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) method for specific surface area determination. The study involved extracting chitosan from shrimp shells and synthesizing graphene oxide from graphite using the Hummers method to enhance Congo Red adsorption efficiency. Comprehensive analysis of the composite beads assessed their physical and functional properties using various techniques. X-ray diffraction and infrared analysis identified their adsorption capabilities, while SEM and BET analysis characterized the porous surface structure of the beads. Maximum adsorption efficiency of 169.49 mg/g was achieved with an adsorbent mass of 0.05 g at pH 3. Kinetic, isotherm, and thermodynamic studies indicated an endothermic process following pseudo-second-order kinetics and the Langmuir isotherm model. The high regression coefficient R 2=0.9953 indicates the strong validity of employing Response Surface Methodology combined with the Box-Behnken Design (RSM-BBD) for accurately predicting the percentage of CR removal through adsorption. Theoretical Density Functional Theory (DFT) analysis elucidated interactions between Congo Red and the reactive sites within the chitosan/graphene oxide beads, providing insights into the adsorption mechanism.

Rapeseed cake meal extract as an eco-friendly green sustainable inhibitor for the corrosion of cold rolled steel in trichloroacetic acid solution

The inhibitory properties of rapeseed cake meal extract (RCME) on the corrosion of cold rolled steel (CRS) in trichloroacetic acid (TCA) were systematically investigated using gravimetric, electrochemical, surface characterizations and theoretical calculations. The results demonstrate that RCME exhibits excellent inhibitory performance with a maximum inhibition efficiency of 92.7% for 100 mg L−1 RCME at 20°C. The adsorption of RCME obeys Langmuir isotherm at 20 and 30°C, Temkin isotherm at 40°C, and Freundlich isotherm at 50°C. RCME acts as a cathodic inhibitor. The charge transfer resistance is increased with the addition of RCME, while the double-layer capacitance decreases. SEM, AFM, CLSM, XPS, XRD and TOF-SIMS analyses confirm that the active components in RCME adsorb onto the surface of CRS, forming a protective film that effectively inhibits the corrosion of CRS by TCA. Along with the increase in the concentration of RCME, the surface tension of the inhibited solution gradually decreases, while the electrical conductivity increases before stabilizing. HPLC-MS and FTIR analyses reveal rutin, linolenic acid, linoleic acid and adenine are the effective substances in RCME. Quantum chemical (QC) calculations and molecular dynamic (MD) simulations indicate that the active centers of the effective inhibitor molecules are predominantly located on benzene rings, O- or N-containing heterocyclic rings, and functional groups such as C=O and C=C. Additionally, their main chains adsorb onto the Fe (001) surface in an approximately flat manner, involving both chemical and physical adsorption processes.

Efficient removal of Pb(II) and Cd(II) from water by polyethyleneimine-amidated sepiolite-sodium alginate composite microspheres: Characterization and mechanistic analysis

In order to improve the physicochemical properties of heavy metal adsorbents, researchers developed a novel composite microsphere material (SEI) by incorporating Sepiolite (Sep) and cross-linked polyethyleneimine (PEI) with sodium alginate (SA) as a carrier. The stability of the SEI under normal use conditions was high by thermogravimetric analysis, and COOH, OH, and NH2 functional groups were detected by FTIR, which were confirmed to be involved in adsorption. It was found that the adsorption rate of SEI on Pb(II) and Cd(II) obeyed a pseudo-second-order kinetic model, while the adsorption pattern was closely related to the Langmuir equation. Notably, the maximum adsorption capacity of SEI for Pb(II) and Cd(II) was 1099.93 mg/g and 112.89 mg/g, respectively, at 30 °C. In addition, thermodynamic analyses showed that the adsorption process was spontaneous, with entropy increase along with heat absorption. After six adsorption and desorption cycles, the removal of Pb(II) and Cd(II) by SEI remained above 90 %. These findings suggest that SEI is a promising and environmentally friendly material for the removal of Pb(II) and Cd(II).

Comparison of Adsorption Capacity of Natural and Acid-activated Kaolinite Clay for Cesium ions from Aqueous Solution

Objectives : This study is to compare the removal efficiency of cesium ions in aqueous solutions by natural and acid-activated kaolinite clay.Methods : Natural kaolinite clay was acid-treated with H2SO4 (2M) at 80oC for 6 h under mechanical stirring. While activating natural kaolinite clay with acid, cations such as Al3+, Ca2+, Mg2+ and Fe3+ were partially eluted from the crystal lattice of natural kaolinite clay, and resulted in the increase in the surface area and the pore volume through the opening of crystal lattice. The surface area and the pore volume of acid-activated kaolinite clay were found to be roughly three times higher than natural kaolinite clay. The characteristics of natural and acid-activated kaolinite clay were observed by X-ray Fluorescence Spectroscopy, Energy Dispersive X-ray Spectroscopy, and BET Surface Area Analyzer.Results and Discussion : Generally, adsorption efficiency of Cs+ ion by acid-activated kaolinite clay showed much higher compared with natural kaolinite clay. At 50 mg L-1 of Cs+ ion concentration and the unit of dose in g L-1 , the adsorption efficiencies of Cs+ ion by natural and acid-activated kaolinite clay were 57.5% and 96.9%, respectively. The data obtained from this study were fitted to the adsorption isotherm and the kinetic models, respectively. It revealed that the Langmuir isotherm and the pseudo-second-order kinetic models described well the adsorption behavior of Cs+ ions on both natural and acid-activated kaolinite clay owing to their higher correlation coefficient R2. Based on the Langmuir isotherm coefficient Q, adsorption capacity of Cs+ ion by natural kaolinite clay and acid-activated kaolinite clay were 5.65 mg g-1 and 10.6 mg g-1, respectively.Conclusion : The results demonstrated that acid-activated kaolinite clay with acid treatment can be used as more effective adsorbent for the adsorption of Cs+ ions from aqueous solution than natural kaolinite clay.

Efficient Removal of Mercury from Wastewater Solutions by a Nitrogen-Doped Hyper-Crosslinked Polyamine.

Mercury, a highly toxic metal and pollutant, poses a significant risk to human health and the environment. This study describes the synthesis of a new nitrogen-doped heteroaromatic hyper-crosslinked polyamine (HCPA) via the polycondensation of 2,6-diaminopyrazine and tris(4-formylphenyl)amine for the efficient removal of mercury ions from aqueous solutions. The HCPA polymer was characterized by solid-state 13C-NMR and FT-IR spectroscopy. A powder X-ray diffraction and thermogravimetric analysis showed that the polymer was semicrystalline in nature and stable up to 500 °C. Adsorption isotherms indicated that mercury adsorption occurred via mono- and multilayer adsorption by HCPA, as depicted by the Langmuir, Freundlich, and Redlich-Peterson isotherm models, with a maximum adsorption capacity of qm = 333.3 mg/g. Adsorption kinetic models suggested that the adsorption process was fast and effective, reaching equilibrium within 20 min. Thermodynamics of the adsorption process revealed that it was endothermic and spontaneous in nature due to the positive ΔH0 of 48 kJ/mol and negative ΔG0 values of -4.5 kJ/mol at 293 K. Wastewater treatment revealed 98% removal of mercury indicating the selective nature of HCPA. Finally, HCPA exhibited excellent performance and regeneration up to three cycles, demonstrating its great potential as an adsorbent for environmental remediation applications.

Controllable Synthesis of Magnetic Composite Derived from MIL-88D and Study on Adsorption Properties of Cu2+

In this paper, MIL-88D (Fe) with spindle shape was prepared by the hydrothermal synthesis method, a metal oxide with a new structure was obtained by calcination at different temperatures as a precursor, and a magnetic iron oxide composite was prepared successfully. At the same time, it was used as an adsorption material for the adsorption of heavy metal ions Cu2+. The influence of the initial pH value and adsorption time on the adsorption effect was investigated, the adsorption kinetics and adsorption isotherm were further fitted, and the adsorption mechanism was preliminarily analyzed. The results show that the magnetic iron oxide composites have a good adsorption capacity for Cu2+. The pH value is an important parameter that affects the adsorption effect. The adsorption of Cu2+ by magnetic iron oxide composites reached adsorption equilibrium in 30 min. The adsorption of Cu2+ by magnetic iron oxide composites conforms to the second-order reaction kinetics and Langmuir adsorption isotherm equation, which indicates that the adsorption process mainly occurs through chemisorption and typical single-molecular-layer adsorption.

Adsorpsi Logam Cu(II) dengan Hidrogel CMC/Pektin Komposisi 2:1 Menggunakan Metode Freeze-Thaw

The Citarum River is included in the category of the most polluted river in the world because it contains chemicals that can reduce air quality. This pollution not only affects air quality but also threatens public health and the surrounding ecosystem. Heavy metals, especially Cu(II), are one of the contaminants that have exceeded the threshold and can cause serious health impacts, including organ damage and nervous system disorders. Hydrogel is an alternative adsorbent that is widely used in various fields, especially in the field of air purification. Hydrogel has the ability to absorb and adsorb contaminants. In particular, Carboxymethyl Cellulose (CMC) hydrogel and pectin hydrogel have attracted much attention for safe water purification because they are non-toxic and have good biodegradability and biocompatibility. The researchers conducted a study on the adsorption of Cu(II) metal using a Carboxymethyl Cellulose (CMC) hydrogel adsorbent and pectin in a 2:1 composition through the Freeze-thaw method. FTIR analysis of the CMC/pectin hydrogel confirmed the presence of C-O-, O-H, C=O, C-H, OH bending, and COOH stretching vibrations. Based on BET analysis, the hydrogel has micropores, a type 1 isotherm, and a surface area of ​​1,889 m2/g. The Langmuir isotherm model was used to determine the ideal adsorption conditions to be a concentration of 298 ppm, an adsorption capacity of 1,0918 mg/g, and an adsorption efficiency of 13,485%.

Biosorptive removal of toxic nitrate ion from wastewater using Albizia lebbeck seed pods: Isotherm and equilibrium studies

A major environmental issue that contaminates drinking water and endangers human health is nitrate pollution. In this study, goethite, citric acid, tartaric acid was employed to modify Albizia lebbeck seed pod for the biosorption of nitrate ion. The developed unmodified Albizia lebbeck (UALB), citric acid modified Albizia lebbeck (CALB), tartaric acid modified Albizia lebbeck (TALB), and goethite acid modified Albizia lebbeck (GALB) were characterized using scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), and point of zero charge (pHpzc) to determine the structural morphology, functional group, and adsorbent surface charge. The adsorption nitrate ion onto the biosorbents was found to be dependent on the operating parameters. The findings revealed that the maximum percentage removal of nitrate ion was 80.8 % at pH 7 for UALB, 80.3 % at pH = 4.0 for CALB, 70.30 % at pH = 3.0 for TALB and 76 % at pH 7 for GALB. The adsorption experimental data for nitrate ion adsorption onto ULAB, CALB, TALB, and GALB were best described by the Langmuir isotherm model. The UALB exhibited the highest Langmuir monolayer adsorption capacities with a value of 344.827 mg/g. Therefore, the unmodified form of Albizia lebbeck (UALB) which is economical, and sustainable provides an efficient alternative method for nitrate removal in aqueous environment.

Facile Fabrication of Zeolitic Imidazolate Framework-8@Regenerated Cellulose Nanofibrous Membranes for Effective Adsorption of Tetracycline Hydrochloride.

The excessive utilization of antimicrobials in humans and animals has resulted in considerable environmental contamination, necessitating the development of high-performance antibiotic adsorption media. A significant challenge is the development of composite nanofibrous materials that are both beneficial and easy to fabricate, with the aim of improving adsorption capacity. Herein, a new kind of zeolitic imidazolate framework-8 (ZIF-8)-modified regenerated cellulose nanofibrous membrane (ZIF-8@RC NFM) was designed and fabricated by combining electrospinning and in situ surface modification technologies. Benefiting from its favorable surface wettability, enhanced tensile strength, interconnected porous structure, and relatively large specific surface area, the resulting ZIF-8@RC NFMs exhibit a relatively high adsorption capacity for tetracycline hydrochloride (TCH) of 105 mg g-1 within 3 h. Moreover, a Langmuir isotherm model and a pseudo-second-order model have been demonstrated to be more appropriate for the description of the TCH adsorption process of ZIF-8@RC-3 NFMs. Additionally, this composite fibrous material could keep a relatively stable adsorption capability under various ionic strengths. The successful fabrication of the novel ZIF-8@RC NFMs may shed light on the further development of wastewater adsorption treatment materials.

Conversion of PET bottles into carbonaceous adsorbents for Pb(II) removal from aqueous solutions via KOH activation

In this study, we present a novel approach to repurpose waste Polyethylene terephthalate (PET), a prominent contributor to global plastic usage, for the synthesis of efficient adsorbents via facial pyrolysis. The as-synthesized adsorbents were applied for the removal of lead (Pb(II)) ions in aqueous solution. Controlled batch experiments at pH 5 with 0.075 g of adsorbent at room temperature (20 °C) were conducted to measure Pb(II) adsorption capacities (mg/g) and fitted on isotherm models (Langmuir, Freundlich, and Temkin) and kinetics models (Pseudo-First order, Pseudo-Second order, and Elovich). Thermodynamic experiments conducted at four different temperatures (293 K, 303 K, 313 K, and 323 K) provided enthalpy, entropy, and Gibbs free energy change parameters, explaining the Pb(II) adsorption behaviors on PET-based adsorbents. The activation process involving KOH, followed by carbonization, yielded adsorbents with exceptional surface areas, pore volumes, and elevated oxygen contents (up to 22.8 %). The best adsorbent exhibited superior performance, achieving a maximum adsorption capacity of 219.7 mg/g within a rapid equilibrium time of 15 min. The adsorption behavior adhered well to the Langmuir isotherm model (R2 = 0.999) and Pseudo-Second Order kinetics model (R2 = 0.999). Furthermore, C600K600 displayed outstanding reusability, with negligible efficiency reduction (<5 %) even after five consecutive cycles. These results underscore the successful conversion of PET waste into a low-cost and highly effective adsorbent, offering a promising solution for sustainable waste management.

Harnessing wood bottom ash for efficient arsenic removal from wastewater: Adsorption mechanisms and process optimisation

This study explored the innovative application of wood bottom ash (WBA) as an adsorbent for arsenic (As) removal from wastewater, focusing on the adsorption mechanism and optimisation of the operational conditions. Comprehensive spectroscopic analyses, including FE-SEM/EDS, BET, XRF, XRD, FT-IR, and XPS, were performed to examine the elemental and mineralogical changes in WBA before and after As adsorption. The study assessed the adsorption kinetics and isotherms, revealing that As adsorption reached equilibrium within 48 h, with a maximum capacity of 121.13 mg/g. The adsorption process followed a pseudo-second-order kinetic model and aligned well with the Langmuir isotherm, indicating that the process is governed by chemisorption and occurs as monolayer adsorption. The primary removal mechanism was the surface precipitation of amorphous calcium arsenate. Response surface methodology was employed to analyse and optimise the factors influencing As removal, including solution pH, ionic strength, adsorbent dose and reaction time. The optimal conditions for maximum As removal were pH 7.11, 8.37 mM ionic strength, 9.08 g/L WBA dose, and 2.58 h reaction time. This study offers novel insights into the efficient and cost-effective use of WBA for As removal, highlighting its potential as a sustainable solution for wastewater treatment in developing countries.