Isotherm Model Research Articles

Removal of metaldehyde and acetamiprid by extracted cellulose from biomass incorporated with copper after acetylation

The presence of pesticides in water have reached to an alarming level in some parts of the world and have caused deteriorating effects on human health. Reclamation of portable water from such contaminants have become mandatory. Scientists around the world are trying to devise new methods of water purification. The target can be achieved either by limiting the use of pesticides for agriculture purposes or by devising unique methods for their recoveries from contaminated water. In this context, herein cellulose has been extracted from Populus nigra, subjected to acetylation using acetic acid in the acidic medium (sulfuric acid). The modified acetylated cellulose was treated with Cu-based salt to enable the metallic combination. The prepared sorbent was characterized by UV, SEM, EDX, XRD, and FTIR techniques. Two insecticides; metaldehyde and acetamiprid in synthetic waste-water solution were subjected for adsorption on the modified sorbent in a series of experiments to evaluate the impact of contact time, sorbent dosage, pH, and temperature. Optimum conditions established in a series of experiments such as 80 and 60 min of contact time for acetamiprid and metaldehyde respectively, pH of 8 and 9 (slightly basic) correspondingly for the mentioned pesticides, and a 0.08 g adsorbent dosage were used in the estimation of kinetics and isothermal parameters. The kinetic data successfully followed the pseudo-second-order kinetic model whereas, the isothermal data was found to be best fitted by Langmuir isotherm model in the case of acetamiprid and by Freundlich in the case of metaldehyde. The regeneration study was performed for both the pesticides showing more than 70 % removal capabilities of fabricated adsorbent after three consecutive cycles. The prepared adsorbent could be a better alternative of commercial activated carbon however, further experiments are encouraged to investigate the full environmental application spectrum of the fabricated sorbent.

Efficient removal of paracetamol, diclofenac sodium, and tetracycline using green synthesized Fe-zn co-doped sunflower seed shells

ABSTRACT In this study, carbon material obtained from sunflower seed shells and doped with Fe and Zn using mint extract (Fe-Zn-SSSC) was prepared, and the usability of this adsorbent in the removal of paracetamol, diclofenac sodium, and tetracycline was investigated. Fe-Zn-SSSC was characterized by SEM-EDX and FTIR. Additionally, the effects of pH and adsorbent dosage on the removal of paracetamol, diclofenac sodium, and tetracycline were investigated. The removal rates of paracetamol, diclofenac sodium, and tetracycline were obtained as 88.7%, 65.4%, and 76.0% at a pH of 4, after 1 hour of adsorption with 5 g/L Fe-Zn-SSSC, respectively. The best removal of paracetamol, diclofenac sodium, and tetracycline was obtained at pH 4, with qmax values calculated as 14.51 mg/g, 6.33 mg/g, and 8.99 mg/g, respectively. It was determined that the adsorption of paracetamol, diclofenac sodium, and tetracycline with Fe-Zn-SSSC was more compatible with the Langmuir isotherm model and pseudo-second-order kinetic model. As a result, this study demonstrates that carbon materials synthesized from sunflower seed shells can serve as an effective and low-cost adsorbent for drug from water.

The adsorption performance of high crystallinity Na-p zeolites prepared from oil shale ash for the waste water treatment

ABSTRACTS The Na-p type zeolite has been prepared by the alkali fusion hydrothermal synthesis method using the pure oil shale ash (OSA) and mixture of OSA and coal fly ash (CFA) as raw materials, which was used for adsorption of methylene blue (MB). The XRD spectra of zeolite synthesized from pure oil shale residue under different conditions indicated that the optimal experimental conditions were determined as follows: acid leaching concentration of 10%, sodium hydroxide dosage of 7 g, crystallization temperature of 130°C, and crystallization time of 12 h. Under the same conditions, zeolite was synthesized using the mixture of OSA and CFA, and its properties were characterized using XRD, SEM, and BET techniques. The results showed that the specific surface area and crystallinity of the zeolite prepared from the mixture were 59.6 m2/g and 86.32%, respectively, which were higher than that of pure OSA (20.6 m2/g and 64.07%). When 0.05 g of zeolite was added to the 35 mg/L MB solution and adsorbed for 180 min, the removal rates of MB by pure OSA, single-source zeolite and zeolite prepared from the mixture were 27.6%, 83.4%, and 99.2%, respectively. The adjusted R square verified that the pseudo-second-order kinetics and Langmuir isotherm model were the best fitting models. The maximum adsorption capacity (Qmax) of zeolite prepared from the mixture for MB was 55.5 mg/g. The above results proved that the novel material prepared in this study could be a potential effective wastewater treatment material.

Ternary polymeric beads of chitosan-based polyaniline doped iron oxide used for removal of cadmium and lead ions from water: Kinetic, isotherm and mechanism studies

ABSTRACT In this study, the binary polymeric magnetic beads were synthesized successfully by one-pot polymerization of polyaniline (PA) doped magnetic iron oxide nanoparticles (MNPs) followed by chitosan (CTS) cross-linkage. The newly fabricated ternary magnetic beads (CTS@MPA) were applied to enhance the removal of Pb(II) and Cd(II) ions from the aqueous media. The prepared nanocomposite was characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and vibrating sample magnetometry (VSM). Adsorption experiments were carried out under optimum conditions. To evaluate the experimental data, the isotherm and kinetic models were conducted. The behavior of adsorption was assessed, and the coefficient of determination values demonstrated that the adsorption process best fitted the Freundlich model due to high values of R2 (0.957 & 0.981). The maximum adsorption capacity was obtained at 150.82 mg.g−1 and 169.21 mg.g−1 for Pb(II) and Cd(II) ions, respectively. Kinetic studies showed that adsorption follows a pseudo-second-order model (R2 = 0.952 & 0.985). Weber-Morris claims that intraparticle diffusion plays a significant role in the adsorption kinetics. Finally, the thermodynamic study is demonstrated, and the adsorption is endothermic, and the mechanism follows a physisorption pattern.

Cnicus Benedictus roots as a low-cost adsorbent for methylene blue dye removal from aqueous solution: kinetic and equilibrium studies

In this research, Cnicus Benedictus roots powder (CBRP) was utilized as a low-cost adsorbent for removing methylene blue (MB) as a cationic dye from aqueous solution. Characterization of CBRP by Boehm titration method, Fourier transform infrared (FT-IR) and environmental scanning electron microscope (ESEM) indicates the presence of different types of functional groups and a very rough surface filled with cavities, suitable for MB adsorption. The effect of various parameters such as CBRP dose (0.2–2 g/1L), contact time (0–180 min), initial pH (1–10), coexisting anions/cations and the initial MB concentration (100–500 mg L−1) on MB adsorption were examined, the results showed that MB uptake depends on the pH of solution, the electrostatic attraction forces, the formation of H-bonds and π–π interactions are the possible CBRP–MB interaction mechanisms. Adsorption kinetic of MB on CBRP was best represented by linear and non-linear form of the pseudo-second order model. The experimental equilibrium data were best described by linear and non-linear forms of Langmuir and Redlich–Peterson isotherm models (R 2> 0.98) with a maximum MB adsorption capacity of 85.47 mg g−1 at 25 °C, the adsorption efficiency R (%) was greater than 90 (%). MB adsorption-desorption experiments showed the reusability of CBRP for five consecutive cycles. According to the obtained results, CBRP can be used as a natural adsorbent material for cationic dyes removal from aqueous solution.

Effective remediation of toxic metal ions (Cd(II), Pb(II), Hg(II), and Ba(II)) using mesoporous glauconite-based iron silicate nanorods: Experimental and theoretical studies

Glauconite minerals underwent an advanced exfoliation and scrolling process, yielding novel iron silicate nanorods (GRs) with increased surface area, reactivity, and improved physicochemical properties. These structures were introduced as superior adsorbents for the highly efficient adsorption of various toxic metal ions, such as Cd(II), Pb(II), Hg(II), and Ba(II). The GRs exhibited maximum adsorption capacities of 283 mg/g for Cd(II), 247 mg/g for Pb(II), 132.3 mg/g for Hg(II), and 165.2 mg/g for Ba(II). The adsorption properties of the GRs during the adsorption of these four metal ions were elucidated through traditional (Langmuir model) and advanced (monolayer model of single energy site) isotherm analyses. Advanced isotherm modeling revealed that the GR surface was saturated with numerous effective adsorption sites, with densities of 125 mg/g for Cd(II), 68.8 mg/g for Pb(II), 40.9 mg/g for Hg(II), and 57.9 mg/g for Ba(II). Moreover, each site could accommodate approximately four ions of the studied metals, which are vertically oriented and participate in multi-ionic adsorption reactions. Energetic analyses, whether based on classical models (Gaussian energy <8 kJ/mol) or advanced models (adsorption energy <40 kJ/mol), indicated that the adsorption processes are governed by physical mechanisms, including electrostatic attractions, van der Waals forces, and hydrogen bonding. Furthermore, thermodynamic assessments confirmed that the adsorption of these ions occurs through exothermic and spontaneous reactions.

Styrene divinyl benzene beads (SM-2) functionalized with triisobutylphosphine sulfide for selective uptake of palladium(II) from nitric acid medium

Resins impregnated with organic extractants regarded as effective adsorbent materials due to their ability for selective sorption. These resins consist of a polymeric material that is infused with accessible organic extractants. Furthermore, these resins merge the unique properties and the distinctive characteristics of both liquid-liquid extraction and solid-liquid sorption processes. In this work, the impregnation of Styrene divinyl benzene beads (SM-2 beads) with triisobutylphosphine sulfide (TIBPS = CYANEX 471X) was prepared. A SM-2 bead functionalized with CYANEX 471X (SM-2-TIBPS beads) was characterized using scanning electron microscope (SEM) and Fourier-transform infrared spectroscopy (FT-IR) techniques and investigated for recovery and separation of palladium ions from a 3 M nitric acid solution. Various parameters were studied, as shaking time effect, nitric acid concentration, SM-2-TIBPS beads weight, Pd(II) concentration and temperature. The Pd(II)/SM-2-TIBPS sorption system has an endothermic nature and was fitted with a Langmuir isotherm model with a 0.9860 regression factor. The kinetics modeling was fitted with PSO and IPD models with regression factors of 0.9889 and 0.9959, respectively. The maximum monolayer sorption capacity of SM-2-TIBPS was found to be 17.47 ± 0.9 mg/g. The sorption of Pd(II) from different media at 3 M takes the following sequence: HNO3 > HCl > H2SO4. Desorption of about 76.38 ± 2.4% was achieved with (1 M + 1 M) of thiourea + HCl after one desorption stage. Effect of other interfering ions, as Pt(II), Pb(II), Eu(III), Cu(II), Mo(VI), Co(III), Zr(IV), Fe(III), Cd(II), and Ce(III), indicates high separation factors between Pd(II) and other investigated metal ions, which ranged from 9.4 to 35.

CHANG-ES. XXXIII. A 20 kpc radio bubble in the halo of the star-forming galaxy NGC 4217

Cosmic rays may be dynamically very important in driving large-scale galactic winds. Edge-on galaxies give us an outsider's view of radio haloes, and of their extra-planar cosmic-ray electrons and magnetic fields. We present a new radio continuum imaging study of the nearby edge-on galaxy NGC\,4217. We examine the distribution of extra-planar cosmic rays and magnetic fields. We observed it with both the Jansky Very Large Array (JVLA) in the $S$ band (2--4\,GHz) and the LOw Frequency ARray (LOFAR) at 144\,MHz. We measured vertical intensity profiles and exponential scale heights. We re-imaged both the JVLA and LOFAR data at matched angular resolution in order to measure radio spectral indices between 144\,MHz and 3\,GHz. Confusing point-like sources were subtracted prior to imaging. We then fitted intensity profiles with cosmic-ray electron advection models, using an isothermal wind model that is driven by a combination of pressure from the hot gas and cosmic rays. We discover a large-scale radio halo on the north-western side of the galactic disc. The morphology is reminiscent of a bubble extending up to 20\,kpc from the disc. We find spectral ageing in the bubble, which allowed us to measure the advection speeds of the cosmic-ray electrons, which accelerate from 300 to $600\ $. Assuming energy equipartition between the cosmic rays and the magnetic field, we estimate the bubble may have been inflated by a modest 10\,&lt;!PCT!&gt; of the kinetic energy injected by supernovae over its dynamical timescale of 35\,Myr. While no active galactic nucleus (AGN) has been detected, such activity in the recent past cannot be ruled out. Non-thermal bubbles with sizes of tens of kiloparsecs may be a ubiquitous feature of star-forming galaxies, and if so this would demonstrate the influence of feedback. Determining possible contributions by AGN feedback will require deeper observations.

Enhancing Selenium Removal Using Pre-Treated Natural Clay: Experimental Investigation and Predictive Modeling

Abstract A heat treatment methodology was adopted as a pretreatment strategy, altering the porous structure of the clay to minimize leaching for selenium adsorption in an aqueous system. Rigorous experiments were carried out in batch mode to determine optimal parameters across various variables, including contact time, adsorbent dosages, selenium concentrations, pH, temperature, and stirring speed during selenium removal using natural clay. Investigating several kinetic and isotherm models revealed the best fitting for the pseudo-second-order and the Langmuir isotherm. Endothermic and spontaneous characteristics of the adsorption process were shown during thermodynamic analysis. In this study, a predictive model for the efficiency of selenium separation was established using Response Surface Methodology (RSM). Additionally, an Artificial Neural Network (ANN), a data-driven model, was employed for comparative analysis. The predictive model exhibited a high degree of agreement with experimental data, demonstrated by a low relative error of &lt;0.10, a high regression coefficient of &gt;0.97), and a substantial Willmott-d index of &gt;0.95. Moreover, the efficacy of pre-activated clay in selenium removal was assessed, revealing the superior performance of ANN models over RSM models in forecasting the efficiency of the adsorption process. This research significantly advances an effective and sustainable material for selenium removal, providing valuable insights into predictive modeling techniques applicable to similar contexts to boost scale-up confidence during industrial implementation in affected regions.&amp;#xD;

Recent Developments in the Adsorption of Heavy Metal Ions from Aqueous Solutions Using Various Nanomaterials.

Water pollution is caused by heavy metals, minerals, and dyes. It has become a global environmental problem. There are numerous methods for removing different types of pollutants from wastewater. Adsorption is viewed as the most promising and financially viable option. Nanostructured materials are used as effective materials for adsorption techniques to extract metal ions from wastewater. Many types of nanomaterials, such as zero-valent metals, metal oxides, carbon nanomaterials, and magnetic nanocomposites, are used as adsorbents. Magnetic nanocomposites as adsorbents have magnetic properties and abundant active functional groups, and unique nanomaterials endow them with better properties than nonmagnetic materials (classic adsorbents). Nonmagnetic materials (classic adsorbents) typically have limitations such as limited adsorption capacity, adsorbent recovery, poor selective adsorption, and secondary treatment. Magnetic nanocomposites are easy to recover, have strong selectivity and high adsorption capacity, are safe and economical, and have always been a hotspot for research. A large amount of data has been collected in this review, which is based on an extensive study of the synthesis, characterization, and adsorption capacity for the elimination of ions from wastewater and their separation from water. The effects of several experimental parameters on metal ion removal, including contact duration, temperature, adsorbent dose, pH, starting ion concentration, and ionic strength, have also been investigated. In addition, a variety of illustrations are used to describe the various adsorption kinetics and adsorption isotherm models, providing insight into the adsorption process.

Innovative eco-friendly methyl orange removal: Mechanism, kinetic, and thermodynamic study using starch cryogel-integrated mesoporous silica nanoparticles

This study introduces a novel, eco−friendly composite, uncalcined mesoporous silica nanoparticles incorporated into a starch cryogel (MSNs-Cry), designed for the effective removal of methyl orange (MO) from water. MSNs−Cry integrates uncalcined mesoporous silica nanoparticles (MSNs) within a starch cryogel network, leveraging the high adsorption capacity of MSNs. The composite achieved a maximum adsorption capacity of 18.98 mg g⁻1 and demonstrated high removal efficiencies of 99.00 % ± 0.21 % in synthetic water (10 mg L−1 MO) and 92.77 % ± 1.76 % in real wastewater containing 0.43 mg L−1 MO. The Langmuir isotherm model provided a superior fit (R2 = 0.9930) compared to the Freundlich model (R2 = 0.9180), and the adsorption kinetics followed a pseudo−second−order model (R2 = 0.9917). The primary adsorption mechanisms included electrostatic attraction, hydrophobic interactions, and hydrogen bonding. The process was endothermic (ΔH° = 31.3 kJ mol−1), spontaneous, and more favorable at higher temperatures (ΔG° = −34.2 to −38.6 kJ mol−1 at 298–318 K). In the presence of sodium silicate at 13.1 times the MO concentration, removal efficiency drops by 35.77 %, and with sodium sulfate and urea at 100 times the MO concentration, it decreases by 8.65 %. Despite these challenges, MSNs−Cry effectively removes MO in the presence of the anionic dye Congo Red and metal ions, demonstrating its selective adsorption capabilities. The tablet form of MSNs−Cry prevents the loss of uncalcined MSNs, mitigating potential environmental and operational impacts. Additionally, the composite's effectiveness at a natural pH of 6.65 eliminates the need for pH adjustment, offering a cost−effective solution for real−world applications. This study establishes MSNs−Cry as a promising material for sustainable water purification.

Sulfonate-Bonded Conjugated Microporous Polymer Hollowed-Out Spheres to Capture Fluoroquinolone Antibiotics and Cationic Dyes from Wastewater.

Developing adsorbent materials for the efficient removal of multiple organic pollutants in water is of importance technological significance. In the present work, a kind of conjugated microporous polymer (CMP) with a hollow sphere structure was constructed by applying SiO2 nanoparticles as a template and 1,3,5-triethynylbenzene (TEB) and 2,7-dibromocarbazole (27-DBCZ) as building blocks via the Sonogashira-Hagihara cross-coupling reaction. In order to further improve the dispersibility of the as-resulting CMPs in water, hydrophilic CMPs (H-S-CMPs) were obtained by a sulfonation modification. The adsorption performance of H-S-CMPs on dyes and antibiotics was investigated, which was based on different experimental parameters such as the initial concentration, contact time, temperature, pH, and adsorbent dose. The adsorption isotherm, kinetics, and thermodynamics were also studied, and the possible adsorption mechanism of H-S-CMPs was discussed. The experimental results illustrated that the adsorption process of H-S-CMPs on dyes and antibiotics is more consistent with the Langmuir isotherm model and the pseudo-second-order kinetic model. The maximum adsorption capacities of H-S-CMPs for rhodamine B (RhB), methylene blue (MB), ciprofloxacin, and norfloxacin were 206.2, 324.7, 222.2, and 216.9 mg/g, respectively, which were determined according to the Langmuir isothern model. In addition, the adsorption mechanism of H-S-CMPs may be attributed to the synergistic effects of hydrogen bonding, electrostatic attraction, π-π stacking, and pore filling. After 5 cycles, H-S-CMPs still maintained good stability, and their removal rate of dyes could reach more than 70%. Notably, this polymeric hollow microsphere has been less extensively investigated as an adsorbent for the removal of dyes and antibiotics. As a result, based on the designable flexibility of CMPs and the unique structure of hollow microspheres, the material holds great promise for wastewater treatment in the presence of multiple pollutants.

Synthesis of novel green nanocomposites by considering enhanced oil recovery and asphaltene adsorption effectiveness in calcite and dolomite formations

Asphaltene deposition is known as the main issues in reservoirs, which causes formation damage in reservoir. This research investigated the effects of a newly introduced green nanocomposites, namely eucalyptus/CuO/Fe3O4/xanthan nanocomposites (EC-NCs), on the inhibition of asphaltene precipitation in calcite and dolomite formations. First, at two time steps of 48 and 96 h, asphaltene adsorption on EC-NCs surfaces was examined through scanning electron microscope (SEM) tests in both calcite and formation tests. Moreover, asphaltene adsorption on the surface of EC-NCs was confirmed through isotherm models including Langmuir and Freundlich and the interfacial tension between CO2 and oil. Finally, a series of static and dynamic tests were performed at the highest adsorption pressure points, including 4200, 3950, and 3700 psi, and at the highest adsorption time step, i.e., 96 h, and the effects of asphaltene adsorption were seen on permeability reduction and asphaltene precipitation. EC-NCs exhibited superior efficacy in both asphaltene adsorption and precipitation inhibition. Two separate pressure changes were observed, and the ratios of the interfacial tension slope in the 2nd to the 1st regions [1st: 200–2700 psi, 2nd:2700–4200 psi] were changed from 19.44 % to 25.00 % and 29.74 % in 48 and 96 h, respectively, and this confirms that asphaltene had indeed adhered to the surface of the EC-NCs. Moreover, at 48, and 96 h, the size reductions of particles in SEM for calcite and dolomite were (29.27 %, 56.81 %), and (59.09 %, 62.25 %), respectively, which shows asphaltene adsorption was more efficient in dolomite formation, and in 96 h.

Sugarcane Bagasse Based Adsorbents and their Adsorption Efficacy on Removal of Heavy Metals from Nakuru Industrial Wastewater: Optimization, Kinetic and Thermodynamic Aspects

Currently, researchers are seeking to reduce heavy metal contamination from the environment, using agricultural waste materials like rice husk, groundnuts shells among others. The study focused on the removal of Cu(II), Pb(II), Cd(II), Ni(II), and Cr(III) ions from aqueous solutions and Nakuru industrial wastewater using sugarcane bagasse (NSCB) and valorised bagasse ash (VSCB), as alternative low-cost agricultural waste bio-sorbents. To achieve this goal, sugarcane bagasse was collected from Nzoia sugar industry in western Kenya, while the valorised bagasse was obtained by heating sugarcane bagasse sample in a muffle furnace at 300°C for three hours. Furthermore, batch adsorption studies were performed, and the effects of several factors, i.e. adsorbent particle size, pH, contact time, initial heavy metal ions concentration and temperature were investigated to optimise the removal efficiency of Pb, Cu, Cd, Ni, and Cr. The optimal adsorption conditions were pH of 5.0, adsorbent dosage of 0.1 g and ≤ 150µm particle size, equilibrium time of 60 minutes and at 25 degrees Celcius. The removal kinetics of the metal ions onto both adsorbents fitted well with the pseudo-second-order model. The removal kinetics of the metal ions onto both adsorbents fitted well with the pseudo-second-order model. The adsorption of Pb2+ and Ni2+ onto NSCB fitted better with the Freundlich isotherm model, while Cd2+, Cu2+ and Cr3+ showed better fit for the Langmuir isotherm model. As for VSCB adsorbent, Cr3+ has a better fit with the Langmuir isotherm model whereas Pb2+, Ni2+, Cd2+, and Cu2+ fitted well on the Freundlich isotherm model. Freundlich constant’s (1/n) values and the separation factor (RL) from the Langmuir isotherm model indicate that the metal ions were favourably adsorbed onto the adsorbents. Langmuir isotherm model was used to estimate the maximum adsorption capacities (qmax) for Cu(II), Pb(II), Ni(II), Cd(II), and Cr(III). The negative free energy change (∆G) values revealed that adsorption process of the metal ions onto NSCB and VSCB was spontaneous. Fourier Transform Infrared Spectroscopy (FTIR) was used for characterization studies. Interactions with metal ions caused the frequencies of the active functional groups, –OH, C=O and C=C, on the bio-sorbent surfaces to shift to higher values. Therefore, sugarcane bagasse and valorised bagasse have demonstrated higher potential to remove relatively all selected heavy metals in the industrial wastewater at controlled pH.

CO2 capture enhancement by metal oxides impregnated coal fly ash: a breakthrough adsorption study.

Coal fired power plants are significant contributors to CO2 emissions and produce solid waste in the form of coal fly ash, posing severe environmental challenges. This study explores the application of dry-impregnated coal fly ash for CO2 capture from gas stream. The modification of coal fly ash was achieved using alkaline earth metal oxides, specifically CaO and MgO, to alter its physical and chemical properties. Characterization techniques like X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and BET (Brunauer-Emmett-Teller) analysis were employed for physio-chemical changes in the adsorbent. Breakthrough experiments were conducted using a laboratory-scale fixed packed-bed reactor to assess the influence of temperature and gas flow rate on CO2 adsorption. Among the synthesized sorbents, calcium oxide-impregnated ash showed the highest CO2 uptake capacity, achieving 9.41mg/g at 30°C and a flow rate of 20 L/hr under atmospheric pressure. Isotherm modeling indicated a heterogeneous adsorbent surface, with the data best fitting the Sips isotherm model. Furthermore, the adsorption data conformed well to the Yoon-Nelson and Thomas kinetic models, affirming their relevance in characterizing the adsorption process under varying conditions. This research emphasizes the potential of coal fly ash-an abundant, cost-free material-as an effective CO2 adsorbent, contributing to both CO2 mitigation and landfill waste reduction.

The facile preparation of polydopamine-modified sepiolite and its adsorption properties and microscopic mechanism for cadmium ion

Natural sepiolite (SEP) has the characteristics of cation exchange, abundant reserves, low cost, and environmental friendliness, but its adsorption capacity for heavy metal pollutants is limited. Because polydopamine (PDA) molecules contain rich functional groups such as phenolic and amino groups, in the present work, dopamine and natural sepiolite were utilized as raw materials to prepare polydopamine-modified sepiolite composite (SEP/PDA) by simple co-precipitation method. According to Langmuir isotherm model, the maximum adsorption capacity of SEP/PDA for Cd2+ can reach 203.21 mg/g at 298 K. At the initial concentration of 100 mg/L, the adsorption capacity was 2.9 times that of natural sepiolite. The composite material has good reusability and anti-cationic interference performance and has 100 % removal ability of low concentration Cd2+ in actual electroplating wastewater. Density Functional Theory (DFT) calculations were performed to obtain the electronic structure information. To elucidate the microscopic mechanism, molecular surface analyses, Interaction Region Indicator (IRI), Atom In Molecules (AIM) theory, Bond Order Density (BOD), and Electron Localization Function (ELF) were conducted. These analyses revealed that the amino nitrogen and phenolic oxygen atoms in the dopamine molecules donate lone pair electrons to coordinate with cadmium ions. Polydopamine, which possesses multiple oxidation states, contains catechol, quinone, and indole or a lesser extend pyrrole groups that can complex with cadmium ions, resulting in the formation of a surface complex. This coordination significantly enhances the adsorption properties of the SEP/PDA composite.

Efficient Adsorption and Degradation of Tetracycline Hydrochloride Using Metal-Organic Framework-Derived Cobalt-Based Catalysts and Mechanism Insight.

High-performance Co-based catalysts were derived by pyrolysis using synthesized MOFs as self-sacrificial templates. Various catalytic systems were constructed by peroxymonosulfate (PMS) to degrade tetracycline hydrochloride (TC). Adsorption-degradation efficiencies, cycle performance, dynamics, and the adsorption catalytic mechanism of various catalytic systems for TC were studied. The effects of different synthetic solvents, pyrolysis temperatures, and single/bimetallic element compositions on degradation efficiency were innovatively compared. The optimal catalyst and PMS dosage for the experiment were determined to be 10 mg and 0.1 mL, respectively. The results indicated that all catalytic systems could efficiently degrade TC and have a high acid-base resistance. The catalyst activity was significantly influenced by the pyrolysis temperature. The optimum pyrolysis temperatures for Zn@Co-N-C-T, CH3OH@Co-N-C-T, and H2O@Co-N-C-T were 1000, 900 and 900 °C, respectively. More abundant pore structures and active sites were generated in Zn@Co-N-C-1000, exhibiting an excellent TC degradation efficiency and adsorption capacity, achieving 94.73% and 167.564 mg/g, respectively. Meanwhile, the total organic carbon (TOC) of TC (50 mL, 50 mg/L) achieved a removal rate (TOC/TOC0) of 50.28%. Zn@Co-N-C-1000/PMS maintained over 83.27% TC degradation after five cycles. The adsorption mechanism of the catalyst for TC was investigated through the analysis of adsorption kinetics and isotherm models. The quenching test and EPR results indicated that TC was primarily degraded through the nonradical pathway. The efficient degradation of TC is attributed to the rapid electron transfer processes occurring at the two-phase interface and the redox cycling of Co0/Co2+/Co3+. Finally, LC-MS was used to analyze the intermediate products of TC degradation in the Zn@Co-N-C-1000/PMS system, and two degradation pathways were proposed.

Compressibility effects in microchannel flows between two-parallel plates at low reynolds and mach numbers: Numerical analysis

Under certain circumstances, flow in microchannels can exhibit compressibility effects even at Reynolds numbers (Re) around (below 2,300) and low Mach numbers (below 0.3). This is particularly true for gases, especially when the flow undergoes significant pressure changes or acceleration within the microchannel. This study investigates the compressibility effects encountered in two-parallel plates microchannels at these low Reynolds and Mach numbers, due to the high-pressure drop associated with the small scale of the microchannels. This uncommon flow is characterized by an exceptionally small channel diameter-to-length aspect ratio (∼10–3), resulting in a friction coefficient that deviates from the typical value for laminar flow between parallel plates (f = 96/Re). Both steady and transient effects on the flow field are examined under low Re subsonic flow, assuming continuum behavior. The ideal gas equation is used to model gas density, while the isothermal Tait-Murnaghan equation models liquid density. For gases, compressibility effects are observed primarily when the inlet pressure ratio exceeds 0.1. The results show that these effects are less pronounced for liquids, even at elevated inlet pressure ratios. Additionally, a flow delay across the channel exhibits a first-order transient response. For liquid flow, this effect depends on the channel resistance, the total fluid volume within the channel, and the liquid's bulk properties, rather than the inlet pressure ratio.

Saraca asoca-assisted green synthesise of ZnO nanoplatelets for photocatalytic activity and adsorption kinetics

ABSTRACT ZnO nanoplatelets (ZnO NPLs) have been successfully synthesised using microwave-assisted technique (400 W, 180 sec) with the plant extract Saraca-asoca. The surface morphology analysis confirms ZnO’s plate-like nanostructure, leading to the creation of ZnO NPLs. The results show excellent photocatalytic performance (at 125 W for both UV and visible light) and effectiveness against malachite green (MG), methyl orange (MO) and rhodamine B (RhB). Notably, ZnO NPLs break down malachite green (MG) exceptionally well, reaching a maximum degradation efficiency of 92% in under 30 min (UV light). Moreover, ZnO NPLs have been evaluated for MG adsorption characterised by the pseudo-first-order kinetic model, alongside the Freundlich and Langmuir isotherm models. In the Freundlich model, the maximal adsorption capacity is determined to be 331 mg/g. These new faceted ZnO NPLs have a great potential for use in photocatalytic and adsorption processes that aim to reduce aqueous pollutants.

Green room-temperature fabrication of phosphotungstic acid functionalized MOF-808 for efficient removal of cationic antibiotics

ZrⅣ-based metal–organic frameworks (MOFs)–featuring exceptional water stability, large surface area, and structural tunability–hold promise for efficient antibiotics adsorption from water. However, their inherent positive charge in neutral environments and the harsh conditions required for their synthesis hinder their effective removal of cationic antibiotics. To address this challenge, a green one-pot synthesis approach was proposed to fabricate phosphotungstic acid-functionalized MOF-808 (termed as PTA@MOF-808) at room temperature for elevated antibiotic adsorption. This approach not only leverages the strong electronegativity of PTA to improve electrostatic interactions and π-π stacking but also finely tailors the pore size of MOF-808, resulting in enhanced adsorption capacity of PTA@MOF-808. The influence of PTA loading, solution pH, and absorbent dosage on the performance of PTA@MOF-808 were studied in detail. Adsorption experiments demonstrated that PTA@MOF-808 outperformed unmodified MOF-808 in removing various positively charged antibiotics, with 5 % PTA@MOF-808 exhibiting maximum adsorption capacities of 548.1 mg g−1 and 482.9 mg g−1, for DOX and TCHC, respectively. The adsorption process followed the Langmuir isothermal model and the pseudo-second-order kinetic equation. Furthermore, the composite PTA@MOF-808 displayed excellent reusability after multiple adsorption–desorption cycles. These findings highlight the potential of PTA@MOF-808 as a promising absorbent for removing specific antibiotics from water, with significant implications for wastewater treatment.