Surface Adsorption Research Articles

Optimization of carbon dioxide adsorption from industrial flue gas using zeolite 13X: A simulation study with Aspen Adsorption and response surface methodology

One of the best ways to prevent further warming of the planet and reduce pollutants is to remove or adsorb and recover carbon dioxide gas from the exit of cement factory exhaust. So far, several methods have been proposed for this; In this research, zeolite 13X adsorbent is used considering the operational conditions. To remove CO2 gas from the desired gas mixture, an adsorption operation unit with a column filled with zeolite 13X adsorbent was simulated in Aspen Adsorption V14 software. Changes in parameters such as temperature, and pressure and their effects on adsorption rate, adsorbent saturation time, and output heat rate were investigated to achieve higher system efficiency and optimal operating conditions. The adsorption unit was optimized by RSM to achieve maximum CO2 adsorption. Temperature and mole fraction of CO2 were identified as key influencing factors determining the adsorption performance of zeolite 13X for CO2 adsorption. It was found that the system should be operated at a temperature of 28.07 °C and a pressure of 1.202 bar to achieve maximum adsorption. Finally, 2.784 mol% CO2 gas was captured by the said process in optimal operating conditions. Further analysis revealed higher temperatures slightly decrease CO2 adsorption capacity, while increasing pressure enhances it. Conversely, elevated flow rates reduce breakthrough time, indicating a trade-off between adsorption capacity and capture efficiency.

Photodegradation of RB5 dye with modified zeolites: influence of temperature and UV irradiation

Abstract This study explores the photocatalytic degradation of Reactive Black 5 (RB5) dye using thermally modified natural zeolites, aiming to improve water purification methods. Zeolites were calcined at 250 °C, 350 °C, and 500 °C, and characterized through x–ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Fourier Transform Infrared Spectroscopy (FTIR) to analyze their structural and morphological transformations. The results reveal that calcination significantly enhances the photocatalytic performance, particularly for ZNM500, which exhibited the highest efficiency, reaching a 60% removal rate of RB5. The degradation process follows a pseudo-first-order kinetic model at lower dye concentrations but adheres more closely to the Langmuir–Hinshelwood equation at higher concentrations, emphasizing the role of surface adsorption in catalysis. UV irradiation was a key factor in boosting reaction rates, with shorter wavelengths (254 nm) providing greater energy, leading to more effective dye breakdown by facilitating the generation of reactive hydroxyl radicals (·OH). These findings suggest that thermally modified zeolites, especially ZNM500, represent a promising solution for wastewater treatment, offering an efficient, cost–effective, and environmentally friendly approach to removing synthetic dyes from contaminated water sources.

Anion substitution strategy for constructing abundant oxygen vacancies in perovskites enables efficient nitrate electroreduction

Perovskite oxides have emerged as promising candidates for electrocatalytic nitrate reduction (ERN) catalysts due to their unique electronic structures and tunable chemical compositions. In this work, we employed a fluorine ion substitution strategy to modulate the oxygen site of LaCoO3 (LCO), resulting in the construction of F-substituted LaCoO3 (LCOF0.5) catalyst for efficient ERN. The incorporation of fluorine ions leads to a weakening of the hybridization between the O 1 s orbital and Co 3d orbital of the catalyst, thereby inducing an increase in oxygen vacancies. The abundant oxygen vacancies can facilitate the electron transfer and surface adsorption energy of the ERN reaction intermediates. This leads to a reduction in the energy barriers for both the reduction of *HNO3 to *NO2 and the reduction of *HNO2 to *NO, thereby enhancing the performance of ERN. As excepted, LCOF0.5 exhibits a rapid reaction rate of k = 5.48 × 10−3 min−1, which is 1.70 times faster than that of pristine LCO, and its catalytic activity approaches that of the state-of-the-art electrocatalysts for ERN. Applying this strategy to LaFeO3 and LaMnO3 also yields similar results, demonstrating its general applicability. The F-anion substitution strategy offers new opportunities for significantly enhancing ERN performance.

Enhancement and sulfur poisoning mechanism of Ce doped ZrO2 catalyst in COS hydrolysis at low-temperature

In order to achieve efficient and longer-lifespan removal of carbonyl sulfide (COS), a high-performance catalyst for hydrolysis is needed urgently. In this study, Ce doped ZrO2 oxides are used to remove COS with or without H2O. The results showed that the doping of Ce significantly improves the removal of COS by ZrO2 and obtains a sulfur capacity of 155.4 mgS/g at 70 °C, but there is still accompanied by sulfur poisoning. The characterization reveals that CeO2 has a cubic phase, ZrO2 has a mixed phase of tetragonal and monoclinic, and Ce-doped Zr with different ratio of Ce/Zr forms a Ce-Zr solid solution. Ce and Ce-Zr oxides have Ce3+/Ce4+ pairs, adsorbed oxygen species and surface oxygen vacancies, while ZrO2 has adsorbed oxygen and surface oxygen vacancies, the presence of which can promote the dissociation of H2O and surface adsorption of COS. ZrO2 has abundant medium-strong basicity while CeO2 has abundant weak and strong basicity, and different proportions of Ce/Zr adjust the surface basic strength, basic amount and surface redox property of Ce-Zr solid solution, which changes the adsorption and hydrolysis of COS and H2O and related oxidation reactions on Ce and Zr, thereby changing the sulfur poisoning. Ce has abundant –OH groups, which can rapidly adsorb COS, leading to hydrolysis and direct oxidation of COS in the absence of H2O, while the OH groups on ZrO2 promote the hydrolysis of COS to H2S. Although suitable Ce-doped ZrO2 improves the removal efficiency of COS, it still inevitably leads to the sulfur poisoning, but the presence of Zr could change the sulfation degree of CeO2 and the Claus reaction.

Uncovering the electrochemical stability and corrosion reaction pathway of Mg (0001) surface: Insight from first-principles calculation

An understanding of the anomalously enhanced hydrogen evolution reaction (HER) of magnesium (Mg) under anodic polarisation in aqueous corrosion is paramount for a predictive theory of its corrosion and metal electrocatalysis. Previous theoretical and experimental studies have proposed that sub-surface hydride phases play a role in this behaviour but the underlying atomic mechanisms remain unclear. By constructing theoretical surface Pourbaix diagrams, based on density functional theory (DFT) calculations, we have identified the atomic structure of a sub-surface hydride phase on the Mg (0001) surface that remains electrochemically stable under significant anodic overpotentials across a wide pH range. Specifically, this stability persists up to 0.38 VSHE under mildly alkaline conditions (e.g., pH = 8), thus providing thermodynamic support for the proposed hydride-enhanced HER under anodic conditions. Reaction barrier analysis establishes that the proposed sub-surface hydride phase could promote anodic HER via a Heyrovsky pathway, based on hydrogen outward diffusion, with an energy barrier of 1.54 eV as the rate-limiting step, showing an anodic characteristic and significantly favouring external anodic polarisation. Furthermore, we have established that the surface adsorption condition, contingent on both the pH and potential, significantly influences the mechanism and kinetics of the initial corrosion of Mg.

Synthesis and Characterization of Hydroxyapatite Composite of Cuttlefish Bone (Sepia sp.) With Gelatin as Rhodamine b Dye Adsorbent

AbstractIn this study, hydroxyapatite‐gelatin (HAp‐Gel) composite using Ca precursor from cuttlefish bone (Sepia Sp.) has great potential to be used in hydroxyapatite synthesis. The HAp‐Gel composite was synthesized in‐situ by sol‐gel method with varying concentrations to see its ability to adsorb rhodamine b dye. XRF analysis results obtained a CaO content of 95.561 %. The 40 % HAp‐Gel composite showed the best adsorption capacity, with a percentage of 27.326 %, which experienced an increase in the percentage of hydroxyapatite adsorption capacity, namely 4.6881 %. FTIR results from 40 % HAp‐Gel composite obtained characteristic peaks of functional groups contained in hydroxyapatite and gelatin. XRD analysis showed the diffraction pattern of HAp by the ICSD standard spectrum (#157481), and the average size of the hydroxyapatite crystal was 9.72 nm. In comparison, the 40 % HAp‐Gel composite crystal was 5.25 nm. SEM‐EDS results showed that the composite morphology was agglomerated with irregular shapes and a Ca/P ratio 1.56. SAA results showed a composite surface area of 55.256 m2/g. The 40 % HAp‐Gel composite sorption application followed the Freudlich isotherm model with multilayer adsorption on the heterogeneous adsorbent surface. The interaction between rhodamine B and HAp‐Gel 40 % occurs at pseudo‐second‐order and can be reused up to two cycles when interacting with rhodamine B.

Computational insight into the selectivity of [formula omitted]-valerolactone hydrodeoxygenation over Rh(111) and Ru(0001)

The observed difference in the selectivity towards alkane, ketone, and alcohol hydrodeoxygenation products over Ru and Rh catalysts is explored using a combination of density functional theory and microkinetics. Using γ-valerolactone as a model compound, we investigate the reaction mechanism in order to identify selectivity determining species. The effect of the coadsorbed water molecule as well as the higher adsorbate surface coverage on reaction barriers and energies is explored as well. The performed calculations suggest that the desired alkane product is formed from a ketone intermediate on Ru, and through both ketone and alcohol on Rh, although the selectivity towars alkane on Rh is much lower than on Ru.

Preparation, Characterization, and Adsorption Performance of H2TiO3 Lithium Ion Sieves with Homogeneous Nanoparticles: Kinetics, Thermodynamics, and Mechanism Analysis

AbstractLi2TiO3 precursor with layered structure is successfully prepared by template‐free method using anatase TiO2 and Li2CO3, followed by the treatment of dilute hydrochloric acid, which leads to obtaining H2TiO3 lithium ion sieve nanoparticles with uniform dispersion and small size. The adsorption performance and mechanism of the H2TiO3 are being studied. The experimental results show that the H2TiO3 lithium ion sieve has a large BET specific surface area (19.10 m2 g−1) and good thermal stability. At the same time, it also has a high adsorption rate and adsorption capacity (55.13 mg g−1) towards Li+ in solution due to its high dispersibility and uniformity of particle size, which can expose more adsorption sites in LiCl solution. The adsorption capacity of the H2TiO3 lithium ion sieve can reach 46.63 mg g−1, which achieves 84.58% of the equilibrium adsorption capacity. The equilibrium adsorption parameters follow the Langmuir model perfectly, demonstrating that Li+ undergoes monolayer adsorption. The results of thermodynamic and kinetic analysis show that the adsorption behavior of H2TiO3 is spontaneous and conforms to the pseudo‐second‐order kinetic model, indicating the adsorption process is controlled by chemosorption. In addition, after five adsorption/desorption cycles, the H2TiO3 lithium ion sieve still shows a high adsorption capacity of 46.15 mg g−1, and the dissolution loss of titanium is only 0.14%, which shows that the cycle stability is excellent. XPS and zeta potential analyses illustrate that the adsorption mechanism of Li+ on the H2TiO3 is an ion exchange reaction between Li+ and H+, combined with the electrostatic attraction of the adsorbent surface. Additionally, the adsorption performance of H2TiO3 lithium ion sieve in West Taijinaier Salt Lake brine was tested, and the adsorbent material proves itself is a perspective candidate for lithium extraction from aqueous lithium resources.

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

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

Uptake of selected heavy metals from contaminated waters utilizing cost-effective and environmentally friendly biosorbents prepared from the residues of a traditionally fermented Ethiopian alcoholic beverage (Tella)

In the current study, the adsorption capacity of Tella residues (residues of fermented alcoholic beverage) for quantitative uptake of Cu(II), Cd(II), Zn(II) and Pb(II) was evaluated. Chemical treatment of the local beer residue (LBR) has improved the removal efficiency of the adsorbent, which was achieved at pH = 5, 1.0 g adsorbent, 50 mg/L initial concentration, 180 min contact time and agitation speed of 100 rpm. The adsorption was found to fit the Langmuir adsorption isotherm model, and the theoretical equilibrium capacities were well fitted with the experimental equilibrium capacities, resulting in chemical adsorption (chemisorptions) on the adsorbent surface while the equilibrium kinetics follows the pseudo-second-order. The adsorption capacity (Qo) of LBR decreases in the following order: Zn(II) > Cu(II) > Pb(II) > Cd(II) as metal concentration ranged from 20-200 mg/L. Thermodynamic parameters, including standard free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were calculated to predict the nature of adsorption. The negative values of ΔG° and the positive value of ΔH° indicate that the adsorption process was spontaneous and endothermic. Adsorption capacities were found to increase when the temperature ranged from 25-60 °C. Thus, the findings suggest a promising application of LBR as an alternative low-cost novel adsorbent for the removal of toxic heavy metals from wastewater.

Efficiency of heat-treated sepiolite in the adsorption of Cd, Zn, and Co from aqueous solutions: A low-cost approach for wastewater treatment

This study investigated the adsorption of Cd, Co, and Zn ions onto unmodified and heat-treated sepiolite, focusing on the effect of contact time, initial pH, and heat pretreatments. Kinetic experiments were conducted in triplicate, and equilibrium experiments indicated that Co2+ had the highest adsorption preference, followed by Zn2+ and Cd2+. The adsorption efficiency for Co2+ significantly increased with higher initial pH, whereas Zn2+ and Cd2+ showed optimal adsorption at lower pH levels. Heat-treated sepiolite at 250 ℃ exhibited a higher surface area and adsorption capacity in comparison with unmodified and 150 ℃-treated sepiolite, which indicated the importance of heat pretreatment. The pseudo-second-order kinetic model better described the adsorption process, and it was confirmed chemisorption as the rate-limiting step. By increasing the contact time, adsorption rates enhanced, with equilibrium achieved within 480 min for all systems. Higher initial solute concentrations led to an increase in adsorption processes, with Co ions consistently showing higher adsorption efficiency in competitive multi-ionic solutions. Adsorption percentages varied with pH and thermal treatment, indicating the importance of these parameters in optimizing sepiolite’s adsorption capacity for heavy metal removal.

Specific iron binding to natural sphingomyelin membrane induced by non-specific co-solutes

HypothesisSphingomyelin (SPM), a crucial phospholipid in the myelin sheath, plays a vital role in insulating nerve fibers. We hypothesize that iron ions selectively bind to the phosphatidylcholine (PC) template within the SPM membrane under near-physiological conditions, resulting in disruptions to membrane organization. These interactions could potentially contribute to the degradation of the myelin sheath, thereby playing a role in the development of neurodegenerative diseases. ExperimentsWe utilized synchrotron-based X-ray spectroscopy and diffraction techniques to study the interaction of iron ions with a bovine spinal-cord SPM monolayer (ML) at the liquid-vapor interface under physiological conditions. The SPM ML serves as a model system, representing localized patches of lipids within a more complex membrane structure. The experiments assessed iron binding to the SPM membrane both in the presence of salts and with additional evaluation of the effects of various ion species on membrane behavior. Grazing incidence X-ray diffraction was employed to analyze the impact of iron binding on the structural integrity of the SPM membrane. FindingsOur results demonstrate that iron ions in dilute solution selectively bind to the PC template of the SPM membrane exclusively at near-physiological salt concentrations (e.g., NaCl, KCl, KI, or CaCl2) and are pH-dependent. In-significant binding was detected in the absence of these salts or at near-neutral pH with salts. The surface adsorption of iron ions is correlated with salt concentration, reaching saturation at physiological levels. In contrast, multivalent ions such as La3+ and Ca2+ do not bind to SPM under similar conditions. Notably, iron binding to the SPM membrane disrupts its in-plane organization, suggesting that these interactions may compromise membrane integrity and contribute to myelin sheath damage associated with neurological disorders.

Enhancement of the Piezocatalytic Response of La-Doped BiFeO3 Nanoparticles by Defects Synergy.

Because of their intrinsic polarization and related properties, ferroelectrics attract significant attention to address energy transformation and environmental protection. Here, by using trivalent-ion-lanthanum doping of BiFeO3 nanoparticles (NPs), it is shown that defects and piezoelectric potential are synergized to achieve a high piezocatalytic effect for decomposing the model Rhodamine B (RhB) pollutant, reaching a record-high piezocatalytic rate of 21360 L mol-1 min-1 (i.e., 100% RhB degradation within 20min) that exceeds most state-of-the art ferroelectrics. The piezocatalytic Bi0.99La0.01FeO3 NPs are also demonstrated to be versatile toward various pharmaceutical pollutants with over 90% removal efficiency, making them extremely efficient piezocatalysts for water purification. It is also shown that 1% La-doping introduces oxygen vacancies and Fe2+ defects. It is thus suggested that oxygen vacancies act as both active sites and charge providers, permitting more surface adsorption sites for the piezocatalysis process, and additional charges and better energy transfer between the NPs and surrounding molecules. Furthermore, the oxygen vacancies are proposed to couple to Fe2+ to form defect dipoles, which in turn introduces an internal field, resulting in more efficient charge de-trapping and separation when added to the piezopotential. This synergistic mechanism is believed to provide a new perspective for designing future piezocatalysts with high performance.

Chiral sensing of glucose by surface-enhanced Raman spectroscopy

BackgroundChiral-selective molecular interactions are considered crucial in numerous physiological processes. Chiral-selective analytical methods of biomolecules with sufficient sensitivity are of great interest in numerous applications. Several surface-enhanced Raman scattering (SERS)-based methods have recently been reported for chiral sensing of biomolecules. However, the lack of molecular-level understanding of SERS spectral changes of reporter and analyte molecules may mislead the development of chiral detection methods. ResultsWe report the chiral sensing of glucose (Glu) by SERS of L- and D-phenylalanine (Phe) with colloidal gold nanoparticles (AuNPs) synthesized by borohydride ions. The Phe SERS showed drastic spectral changes only when Glu of the same chirality as Phe was added, which also showed strong dependence on Glu concentration. The increase of δ(COO−) and decrease of νs(COO−) modes in Phe SERS, exclusively observed with the chiral-selective bimolecular interactions of chirally matching Glu, are understood as modified surface adsorption geometry of the carboxylate group. Quantitative spectral analysis for the Glu concentration of a specific chirality showed the detection limit down to 2 × 10−9 - 2 × 10−7 M levels depending on the existence of the opposite enantiomer of Glu. SignificanceIn this study, we demonstrated that the Phe SERS on AuNPs can be utilized in the chiral sensing of Glu molecules with quantitative concentration analysis. The bimolecular interactions of surface-adsorbed Phe and chirally matching Glu are suggested for the chiral recognition of Phe SERS. These results imply that a molecule-level understanding is indispensable for developing SERS-based chiral sensing methods.

Positively Photo-Responsive Adsorption Over Binary Copper Porphyrin Framework and Graphene Film Sorbents.

Photo-responsive adsorption has emerged as a vibrant area because it provides a promising route to reduce the energy consumption of the traditional adsorption separation. However, the current methodology to fabricate photo-responsive sorbents is still subject to the photo-deforming molecular units. In this study, a new initiative of photo-dissociated electron-hole pairs is proposed to generate amazing adsorption activity, and prove its feasibility. Employing CuPP [PP = 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin] framework nanosheets compounded with graphene, binary film (BF) sorbents are successfully fabricated. The paradigmatic BF nanostructure brings about efficiently photo-excited electron-hole pairs with durable enough lifetime to meet the needs of microscopic adsorption equilibrium, which ultimately alters the electron density distribution of adsorption surface, and thus markedly modulates the adsorption activity. Therefore, an amazing photo-enhanced adsorption capability for the index gas CO can be gotten. Once exposed to the visible-light at 420nm, the CO adsorption capacity (0°C, 1bar) is risen from 0.23mmolg-1 in the darkness to 1.66mmolg-1, changed by+622%. This is essentially different from majority of current photo-responsive sorbents based on photo-deforming molecular units, of which adsorption capability is only decreased with photo-induction, and the maximum rate of change reported is just -54%.

Simulation of Gas‐Particle Partitioning of Semi‐Volatile n‐Alkanes and PAHs in Nanjing, China, and Denver, United States: Effects of Vapor Pressure and Surface Adsorption Estimation

AbstractThe concentration data of semi‐volatile n‐alkanes and PAHs in the gas phase and in PM2.5 were obtained from Nanjing and Denver. First, the gas‐particle partitioning coefficients of the target compounds were calculated and compared with the predictions based on the equilibrium absorptive partitioning theory. Although the vapor pressure (poL) estimation method was selected to improve the agreement between measured and predicted partitioning coefficients, n‐alkanes in Denver and PAHs in both cities exhibited stronger sorption to PM2.5 than predicted. By including the adsorption mechanism, the average logarithms and temporal variations of the partitioning coefficients were well simulated in both Nanjing and Denver. The partitioning of n‐alkanes in Nanjing can be primarily explained by the absorption mechanism, while the adsorption mechanism dominates that for n‐alkanes in Denver and PAHs in both cities. To obtain an optimal simulation, the poL of n‐alkanes and PAHs was estimated using the SPARC and SIMPOL—two group contribution methods, respectively, and the difference between desorption and vaporization enthalpies was set between 2 and 3 kcal mol−1 for n‐alkanes in Denver and PAHs in both cities. Therefore, the estimation of poL and surface adsorption should be carefully considered when parameterizing the gas‐particle partitioning of non‐polar organic compounds in future field and modeling studies.

Effect of α-tocopherol on the oil absorption of French fries based on physicochemical characteristics of frying oil and the morphology of French fries

With the development of oil processing technology, the retention rate of lipid concomitants in oil has increased. The effect of lipid concomitants on the physicochemical characteristics of oil has garnered significant interest; however, the effect of the lipid concomitant α-tocopherol on the physicochemical properties of rice bran oil (RBO) and the oil absorbency of French fries during frying is unclear. Thus, the influence of α-tocopherol on total polar compounds, diacylglycerols content, and viscosity of frying oil as well as oil content and distribution, moisture content, micromorphology, and quality of French fries is studied. The results revealed that RBO with 0%–0.1% α-tocopherol dose-dependently decreased the total polar compounds, diacylglycerols content, and the viscosity of RBO. This primarily affected the adsorption of surface and structural oils in the French fries. Additionally, RBO with 0%–0.1% α-tocopherol decreased the porous structure of the French fries. Compared with other α-tocopherol levels, RBO supplemented with 0.1% α-tocopherol demonstrated a better effect on reducing the oil absorption in French fries. Moreover, α-tocopherol had a minimal effect on French fry quality. Consequently, incorporating α-tocopherol (0.1%) into frying oil because of its inhibitory effect on the oil absorption of French fries is recommended.

Electrochemical sensor based on a glassy carbon electrode modified with a 3D carbon nanoporous composite for the detection of paracetamol in pharmaceutical samples

With the continued appearance of new drugs, there is a growing interest in the development of new analytical tools to detect and quantify drugs using a simple and reliable way. In this work, we describe the development of an electrochemical sensor based on glassy carbon electrodes modified with a carbon tubular nanocomposite for the detection of paracetamol in pharmaceutical samples. Paracetamol shows a strong adsorption on the electrode surface, which makes possible its determination by adsorptive differential pulse voltammetry in 0.1 mol/L citrate–phosphate pH 5 buffer solution. Optimal conditions for dispersion of carbonaceous material and best conditions for surface adsorption of paracetamol were obtained from experimental designs based on response surface methodology. The high adsorption capacity of paracetamol on the 3D carbon nanoporous composite and the sensitivity of the electrochemical technique employed showed a synergistic effect that allowed reaching a detection limit of 30 nmol L− 1 (4.5 ppb). In addition, the reproducibility and the repeatability were 7 and 5 %, respectively. The paracetamol determination from pharmaceutical samples was performed without pre-treatment of samples. The values of paracetamol founded for different pharmaceutical samples were in a very good agreement with those values obtained from the same samples using HPLC. Therefore, the developed electrochemical sensor is a promising, inexpensive, and easy-to-use tool for the detection and quantification of paracetamol in pharmaceutical samples.

The Use of Organoclays as Excipient for Metformin Delivery: Experimental and Computational Study

This work combines experimental and computational modeling studies for the preparation of a composite of metformin and an organoclay, examining the advantages of a Tunisian clay used for drug delivery applications. The clay mineral studied is a montmorillonite-like smectite (Sm-Na), and the organoclay derivative (HDTMA-Sm) was used as a drug carrier for metformin hydrochloride (MET). In order to assess the MET loading into the clays, these materials were characterized by means of cation exchange capacity assessment, specific surface area measurement, and with the techniques of X-ray diffraction (XRD), differential scanning calorimetry, X-ray fluorescence spectroscopy, and Fourier-transformed infrared spectroscopy. Computational molecular modeling studies showed the surface adsorption process, identifying the clay–drug interactions through hydrogen bonds, and assessing electrostatic interactions for the hybrid MET/Sm-Na and hydrophobic interactions and cation exchange for the hybrid MET/HDTMA-Sm. The results show that the clays (Sm-Na and HDTMA-Sm) are capable of adsorbing MET, reaching a maximum load of 12.42 and 21.97 %, respectively. The adsorption isotherms were fitted by the Freundlich model, indicating heterogeneous adsorption of the studied adsorbate–adsorbent system, and they followed pseudo-second-order kinetics. The calculations of ΔGº indicate the spontaneous and reversible nature of the adsorption. The calculation of ΔH° indicates physical adsorption for the purified clay (Sm-Na) and chemical adsorption for the modified clay (HDTMA-Sm). The release of intercalated MET was studied in media simulating gastric and intestinal fluids, revealing that the purified clay (Sm-Na) and the modified organoclay (HDTMA-Sm) can be used as carriers in controlled drug delivery in future clinical applications. The molecular modeling studies confirmed the experimental phenomena, showing that the main adsorption mechanism is the cation exchange process between proton and MET cations into the interlayer space.

Adsorption dynamics of chloride removal with activated vetiver root powder: dynamic modeling perspectives and ANN predictions

ABSTRACT This study evaluates activated vetiver root powder as chloride ion adsorbent for saline water treatment. Experimental results demonstrate that activated vetiver root effectively removes chloride ions from saline solutions. Higher bed heights and lower flow rates improve efficiency by providing more adsorption sites and a longer contact time. However, higher concentrations lead to rapid bed exhaustion, highlighting the need for parameter optimization. Dynamic adsorption modeling using Thomas, Yoon–Nelson, and Clark models assesses the impact of bed height, flow rates, and initial concentration on chloride removal efficiency. Breakthrough equations closely fitted experimental data in the following order: Thomas model (R2 = 0.999) > Clark (R2 = 0.996) > Yoon–Nelson (R2 = 0.994). Scanning electron microscopy (SEM) analysis identifies pores and pockets as main surface components. Insights into adsorption mechanisms were gained through infrared and X-ray spectroscopies. A novel predictive algorithm for chloride removal in a continuous mode was developed using neural networks. Artificial neural network (ANN) prediction ability was assessed using MSE and R2 values. Future commercial applications of activated vetiver powder can be investigated using real salinity-induced wastewater. Additionally, assessing the adsorbent's regeneration and reusability is vital for confirming its cost-effectiveness and sustainability in longstanding use. This study offers perceptions for developing efficient water treatment strategies by understanding adsorption dynamics and surface characteristics for optimizing chloride removal processes.