Kinetic Model Research Articles

N-nitrosodimethylamine removal by a novel silver/sulfur-coated nanoscale zero-valent iron/activated carbon composite: Adsorption kinetics, mechanisms, and degradation pathways

The removal of disinfection by-products from water is of critical importance to achieve the water purification. N-nitrosodimethylamine (NDMA), an emerging nitrogenous disinfection by-product produced by the chlorine-ammonia disinfection, remains significantly hazardous even at low concentrations. Herein, an activated carbon (AC)-supported nanoscale zero-valent iron (nZVI) coated with sulfur (S) and silver (Ag) composite (Ag@S-nZVI/AC) was synthesized, characterized via several techniques and evaluated for NDMA removal performance. The results demonstrated that crystalline Ag and mackinawite (FeS) coated amorphous nZVI spheres were successfully anchored on AC. The removal of NDMA at ultra-lower concentrations by the Ag@S-nZVI/AC composite was better fitted by pseudo-second-order (PSO) kinetic and Freundlich isotherm models. NDMA was chemically adsorbed in multiple layers on heterogeneous surface of the Ag@S-nZVI/AC composite via spontaneous endothermic process. The adsorption constant (KF) of NDMA removal by Ag@S-nZVI/AC at T=298 K was 9.89 times greater than that of NDMA removal by pristine AC. The van der Waals forces, hydrogen bonds and surface-mediated electron transfer were the main mechanisms responsible for the highly effective remediation of ultra-lower concentrations of NDMA from drinking water. The decomposition of NDMA was significantly enhanced by Ag@S-nZVI/AC, resulting in the generation of more dimethylamine (DMA), ammonium and the nitrogen-containing compounds. The decomposition process involved the oxidation of FeS, S and Fe0 surface as well as the hydrogenation of Ag. The post-leaching concentrations of Fe, Ag and S in treated drinking water were lower than the standard permissible limits.

Kinetic Modeling of Sodium Bicarbonate Pre-treatment of Corn Stalks for Increased Biogas Generation during Anaerobic Digestion: Viability and Fertilizer Potential

Kinetic Modeling of Sodium Bicarbonate Pre-treatment of Corn Stalks for Increased Biogas Generation during Anaerobic Digestion: Viability and Fertilizer Potential

Cerebral perfusion metrics calculated directly from a hypoxia-induced step change in deoxyhemoglobin

Resting cerebral perfusion metrics can be calculated from the MRI ΔR2* signal during the first passage of an intravascular bolus of a Gadolinium-based contrast agent (GBCA), or more recently, a transient hypoxia-induced change in the concentration of deoxyhemoglobin ([dOHb]). Conventional analysis follows a proxy process that includes deconvolution of an arterial input function (AIF) in a tracer kinetic model. We hypothesized that the step reduction in magnetic susceptibility accompanying a step decrease in [dOHb] that occurs when a single breath of oxygen terminates a brief episode of lung hypoxia permits direct calculation of relative perfusion metrics. The time course of the ΔR2* signal response enables both the discrimination of blood arrival times and the time course of voxel filling. We calculated the perfusion metrics implied by this step signal change in seven healthy volunteers and compared them to those from conventional analyses of GBCA and dOHb using their AIF and indicator dilution theory. Voxel-wise maps of relative cerebral blood flow and relative cerebral blood volume had a high spatial and magnitude congruence for all three analyses (r > 0.9) and were similar in appearance to published maps. The mean (SD) transit times (s) in grey and white matter respectively for the step response (7.4 (1.1), 8.05 (1.71)) were greater than those for GBCA (2.6 (0.45), 3.54 (0.83)) attributable to the nature of their respective calculation models. In conclusion we believe these calculations of perfusion metrics derived directly from ΔR2* have superior merit to calculations via AIF by virtue of being calculated from a direct signal rather than through a proxy model which encompasses errors inherent in designating an AIF and performing deconvolution calculations.

Isotherm and kinetic modeling of Cr(VI) removal with quaternary ammonium functionalized silica

Isotherm and kinetic modeling of Cr(VI) removal with quaternary ammonium functionalized silica

Efficient degradation and enhanced anticomplementary activity of Belamcanda chinensis (L.) DC. polysaccharides via trifluoroacetic acid treatment with different degrees.

The degradation of Belamcanda chinensis (L.) DC. polysaccharides was carried out by five concentrations of trifluoroacetic acid (TFA) (1-5mol/L), and their physicochemical properties, degradation kinetics and anticomplementary activity were investigated. The findings revealed a notable reduction in the molecular weight of BCP, from an initial value of 2.622×105g/mol to a final value of 6.255×104g/mol, and the water solubility index increased from 90.66±0.42% to 97.78±0.43%. The degraded polysaccharides of B. chinensis exhibited a comparable monosaccharide composition comprising Man, GalA, Glc, Gal, and Ara. As the concentration of TFA increased, the degradation rate constant increased from 1.468×10-3 to 5.943×10-3, and the process followed the first-order degradation kinetic model (R2>0.97) and the random fracture model (R2>0.96). Furthermore, the five degraded polysaccharides still exhibit good thermal stability. In vitro experiments showed that DBCP-3 exhibited more potent anticomplementary activity than the original polysaccharides and positive drugs, which was strongly correlated with its Mw (r=0.6-0.8), inhibiting complement activation by blocking C2 and C4. These results indicated that TFA degradation has a positive effect on polysaccharides, of which DBCP-3 is expected to treat diseases involving hyperactivation of the complement system.

Assessing Onsager’s reciprocity difference in signal transduction cascade model: a new metric for evaluating cellular response dynamics

The cell signaling system translates extracellular changes into biochemical reactions within the cell, ultimately affecting gene expression. This system is crucial for responding to environmental stressors through a series of chemical interactions among intracellular molecules. Although Onsager’s reciprocity theorem is foundational in analyzing non-equilibrium systems, its limitations are evident in the nonlinear responses characteristic of the chemical reactions essential for signal transduction. In this study, we demonstrate that the reciprocity coefficients between signal molecule Xj, Lj:j+1 in the transmission from the jth step to the j + 1th step and molecule Xj+1, Lj+1:j from the j + 1th step to the jth step are not necessarily equal due to nonlinear interactions. This disparity, quantified as Jj:j+1 = −Lj:j+1 + Lj+1:j, reflects the amount of signal transduced between these steps, coupled with the phosphorylation rate of signaling molecules. Through kinetic model simulations, we analyzed the cellular response to external radiation exposure, monitoring how signal transduction progresses via phosphorylation reactions over time. The simulation showed a transition from an unstable to a stable, unimodal signaling pattern at varying radiation doses, correlating well with actual cellular responses. In conclusion, our findings suggest that the discrepancy in Onsager’s reciprocity coefficients correlates with signal transduction velocity, providing novel insights into the thermodynamic underpinnings of cellular signaling mechanisms.

Extending the shelf-life of whole egg powder with different packaging: Based on the multivariate accelerated shelf-life test model

Whole egg powder (WEP), predominantly utilized as an ingredient in ready-to-eat foods such as bakery items, puffed snacks and other products, necessitates the consideration of appropriate packaging materials to preserve its quality properties during processing and transportation. The quality changes of WEP were evaluated in PA, C-PA and PE-PP-Al packaging for 35 days at 60 °C in accelerated storage. The results indicate that among the three packaging materials, PE-PP-Al exhibits the highest barrier properties, effectively inhibiting moisture loss, caking, reduced solubility, oxidative deterioration, and decreased thermal stability in WEP. The Multivariate Accelerated Shelf-Life Test (MASLT) was carried out using water content, moisture activity, color value, lipid oxidation (PV, TBA, AV) and organoleptic attributes in different packaging methods, and the predicted shelf-life of WEP at room temperature was 421, 470 and 549 days with RMSE (0.171–0.893) using principal component analysis coupled with kinetic modeling.

Application of ATR-FTIR for Green Arabica Bean Shelf-Life Determination in Accelerated Storage

Coffee bean oxidation is associated with enzymatic and non-enzymatic browning, the degradation of desirable aromatic compounds, the development of undesirable flavors, increased susceptibility to microbial spoilage, and volatile compound losses. This study investigated natural dry process (DP) and honey process (HP) green coffee beans stored in GrainPro® bags for 0, 5, 10, and 20 days under accelerated storage conditions at 30 °C, 40 °C, and 50 °C with relative humidity of 50%. A kinetic model was used to estimate the shelf life of the green coffee beans. DP recorded durability of 45.67, 29.9, and 24.92 days at 30 °C, 40 °C, and 50 °C, respectively, with HP 60.34, 38.07, and 19.22 days. Partial least squares (PLS) analysis was performed to build the models in order to predict the shelf life of coffee based on peroxide (PV) and thiobarbituric acid reactive substances (TBARS) values. In terms of prediction with leave-one-out cross-validation (LOOCV), PLS provided a higher accuracy for TBARS (R2 = 0.801), while PV was lower (R2 = 0.469). However, the auto-prediction showed good agreement among the observed and predicted values in both PV (R2 = 0.802) and TBARS (R2 = 0.932). Based on the variable importance of projection (VIP) scores, the ATR-FTIR peaks as 3000–2825, 2154–2150, 1780–1712, 1487–2483, 1186–1126, 1107–1097, and 1012–949 cm−1 were identified to be the most related to PV and TBARS on green coffee beans shelf life. ATR-FITR showed potential as a fast and accurate technique to evaluate the oxidation reaction that related to the loss of coffee quality during storage.

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

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

Engineering Bis-Pyridine N-Functionalized Cellulose Aerogel for Efficient Extraction of Cu2+ from High-Acidity Wastewaters: Coupling Molecular Scale Interpretation with Experiment.

In order to address the issue of protonation of functional groups and structural instability on the surface of aerogel due to strong acidic wastewater, a three-dimensional bis-pyridine N cellulose aerogel [PEIPD/carboxymethyl cellulose (CMC)] with protonation resistance was prepared in this paper by grafting pyridine onto polyethylenimine. The adsorption capacity for Cu2+ of the as-prepared aerogel is as high as 1.64 mmol/g (pH 5) and is maintained well in high-acidity solutions (1.15 mmol/g at pH = 2). It reveals high selectivity, splendid anti-interference ability, and also reliable on the recycle performance. Through the zeta potential tests, this adsorbent reveals a rather low zero charge point (pHpzc = 2.2). The adsorption of Cu2+ on the adsorbent is consistent with the pseudo-second-order kinetic model and the Langmuir model, suggesting that the adsorption process is dominated by chemisorption in a monolayer. The characterizations by Fourier transform infrared spectrometry and X-ray photoelectron spectroscopy proved pyridine N as responsible binding sites, based on which two possible mechanisms are proposed, including chelation and cation-π interaction. Density functional theory calculations are further used to precisely investigate the pathway. By comparing the binding energies, molecular electrostatic potentials, electron densities, and differential charge densities, the bis-pyridine N functional group is finally determined to be of much higher affinity to Cu2+ following chelation reaction as designated. By integrating bis-pyridine N with the CMC and understanding their crucial roles, this will provide significant insights into the rational design of aerogel adsorbents to enhance the recovery of Cu from strongly acidic wastewaters.

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

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

Adsorption of a Multicomponent Pharmaceutical Wastewater on Charcoal-Based Activated Carbon: Equilibrium and Kinetics

The treatment of pharmaceutical wastewater is a critical environmental challenge, necessitating efficient removal methods. This study investigates the adsorption of a synthetic multicomponent pharmaceutical wastewater (SPWW) containing methanol, benzene, methylene chloride, 4-aminophenol, aniline, and sulfanilic acid onto charcoal-based activated carbon (AC). Batch experiments were conducted to study the effects of pH, contact time, and initial concentrations of the adsorbates. The results show that longer contact time and higher initial concentrations increase the adsorption capacity, whereas pH shows no significant effect on the adsorption capacity at a value of less than 10, eliminating the need for pH adjustment and reducing process costs. The pseudo-second order (PSO) kinetic model best describes the adsorption process, with intraparticle diffusion playing a key role, as confirmed by the Weber and Morris (W-M) model. Six models describing the adsorption at equilibrium are applied to experimental data, and their parameters are estimated with a nonlinear regression model. Among isotherm models, the Langmuir-Freundlich model provides the best fit, suggesting multilayer adsorption on a heterogeneous granular activated carbon (GAC) surface. The maximum adsorption capacity is estimated to be 522.3 mgC/gAC. Experimental results confirm that GAC could effectively treat highly concentrated pharmaceutical wastewater, achieving up to 52% removal efficiency.

Microfluidic aerosol-assisted synthesis of gefitinib anticancer drug nanocarrier based on chitosan natural polymer

An aerosol-assisted approach was devised to synthesize gefitinib anticancer drug-loaded chitosan nanocarriers (GefNCs). The nanocarrier synthesis involves mixing and interacting gefitinib molecules with chitosan natural polymer within a microfluidic chip. The combination was nebulized with an on-chip integrated micropneumatic nebulizer with N2 as the nebulizer gas. The aerosol was collected in a beaker containing a glutaraldehyde cross-linking agent while magnetically stirring. The chip was created by CO2 laser engraving on polymethyl methacrylate sheets. The synthesized GefNCs were characterized using FTIR, DLS, FESEM, and TEM. The FESEM images revealed a nanoparticle size distribution of 18.5 ± 4.6 nm. After adjusting numerous experimental parameters such as chip design, polymer concentration, solution flow rate, and nebulizer gas flow rate, the synthesized nanocarrier's release mechanism was investigated using various kinetic models. The results demonstrated that the release behavior of GefNCs is pH-sensitive and greater at acidic pH values than physiological pH, making the synthesized nanocarrier a potential for targeted gefitinib delivery to cancer cells. Furthermore, the kinetic studies revealed that the drug's release mechanism best matches Fick's diffusion rule. Under optimal conditions, the encapsulation efficiency was 77.8 %. The cytotoxicity of the produced nanocarrier was investigated on the A549 non-small cell lung carcinoma. The MTT test revealed that the produced nanocarrier had a lower IC50 than the free medication. Furthermore, cytotoxicity experiments on empty nanocarriers revealed that the materials utilized to synthesize nanocarriers have no appreciable cytotoxicity. The developed microfluidic-assisted approach provides a quicker synthesis procedure with a high encapsulation efficiency.

Efficient CO2 capture using a novel Zn-doped activated carbon developed from agricultural liquid biomass: Adsorption study, mechanism and transition state

A Zn-doped carbon was prepared and used as an effective CO2 adsorbent. This carbonaceous material was developed from olive mill wastewater (OMWW) by an innovative process using thermal shock flash pyrolysis followed by zinc chloride impregnation at ambient temperature. The developed Zn-doped carbon is highly porous (1406.56 m2.g−1), thermally stable and rich in active sites. The Temkin isotherm and the pseudo-second order kinetic model best describe the adsorption of CO2 on the developed material, and the storage capacity is of 370.41 mg g−1 (293 K). Thermodynamic parameters showed favorable, exothermic, and orderly adsorption. Two new isotherms, based on the number of layers formed at the surface, developed by advanced statistical modelling, were adapted and used to understand the mechanism in depth. The analysis of the results showed that CO2 adsorption occurs through the appearance of double layers on the adsorbent surface. Adapted models showed: only one molecule was adsorbed per surface active site, a very low degree of aggregation of CO2 molecules before adsorption and the molecules were adsorbed in a parallel orientation. The activation parameters showed a rapid and physical adsorption with a drop in entropy at the transition state. The mechanisms involved were governed by thermodynamic control with the possibility of easy desorption at high temperature. Zn-doped carbon is an ecological approach to reduce CO2 emissions on the globe.

Thermal decomposition of alkenes: role of allylic C-C bond cleavage

Thermal decomposition of alkenes is critical in many chemical processes. In the alkene moiety, allylic CC bonds are significantly weaker than alkylic and vinylic CC bonds. To address literature discrepancies in the rate of allylic CC bond cleavage, the current work investigates the thermal decomposition of two prototype molecules, namely 1-hexene (k1) and 4-methyl-1-pentene (k2). The formation of product allyl radicals is tracked using a highly sensitive UV laser diagnostic to determine the rate coefficients of k1 and k2 over 1178–1359 K in a shock tube. Both reactions exhibit a positive Arrhenius temperature dependence, with the decomposition of 4-methyl-1-pentene occurring 1.5–3 times faster than that of 1-hexene. Values of k1 adopted in literature models vary by an order of magnitude.By integrating our previous measurements of 1-butene and 1-pentene decomposition (Zhou et al., 2024), this work establishes a comprehensive set of rate rules that encompasses the decomposition of allylic-primary (P), allylic-secondary (S21 and S22), and allylic-tertiary (T) CC bonds. At 1200 K, the decomposition of a tertiary allylic CC bond (kT) occurs 42 times faster than that of the primary CC bond (kP). Notably, our established rate rules caution against commonly adopted analogies between the rate coefficients of the thermal decomposition of 1-butene and 1-pentene, as kS21 proceeds 3–7 times faster than kP.The implementation of these rate rules in various kinetic models of alkenes and biofuels greatly enhances the accuracy of their predictions. This work thus contributes to a deeper understanding of the mechanisms underlying soot formation during from the combustion of unsaturated fuels.

Enhancement of Co(II) removal via coupling of electrosorption and electrodeposition using asymmetric electrode from wastewater

The growing demand for nuclear energy and the promotion of nuclear technology applications will generate large quantities of cobalt-containing wastewater. The efficient removal of cobalt from radioactive wastewater is of great significance for the resource regeneration and environmental protection. However, conventional removal methods are constrained by the poor removal efficiency and slow removal kinetics. Herein, the sulfonated polyether ether ketone coated activated carbon fibers (anode)/activated carbon fibers (cathode) asymmetric electrodes was proposed to boost the Co(II) electrosorption performance. The experimental results showed that compared to traditional symmetric electrodes, the theoretical maximum electrosorption capacity (116.19 mg·g−1) had an exceptional enhancement of 72 %. The voltage and initial pH of the solution had an undeniable impact on the efficiency of cobalt electrosorption. Furthermore, more than 75 % of Co(II) was rapidly immobilized within 3 h. The kinetic fitting indicated that the electrosorption process was more appropriately described by pseudo-second-order kinetic model. The Co(II) removal efficiency was up to 80 % under the conditions of coexistence with Na+, Mn2+, Ni2+, Zn2+, Sr2+, and Cs+. More importantly, it combines two synthetic mechanisms of electrosorption and electrodeposition to realize the purification of cobalt-containing wastewater. Overall, considering the fast and highly-efficient cobalt removal performance and innate economy, the asymmetric electrosorption for cobalt removal provides new insights into the treatment of cobalt-containing wastewater

Insight into the mechanism of adsorption and release of 11-nor-9-carboxy-Δ9-tetrahydrocannabinol in sewage by modeling regional suspended particles for evaluation of the influence on monitoring of cannabis illicit abuse

The adsorption of 11-nor-9-carboxy-∆9-tetrahydrocannabinol (THC-COOH) by the suspended particles in sewage makes it fail to accurately monitor cannabis abuse. In this work, the model sewage sample was prepared through equivalent mixing the sewage from 10 different sewage treatment plants in Guangdong province of China and used as a comprehensive representative for investigating the adsorption and release behavior of THC-COOH on the suspended particles under different temperature and pH. The solid-liquid distribution of THC-COOH in sewage depended strongly on the adsorption and release properties which were susceptible to the temperature and pH, specially adjusting pH to 11.0 could release more than 90% of THC-COOH from the suspended particles. By means of the kinetics models, pseudo-second-order kinetic and Weber-Morris models revealed the mechanism of adsorption and release of THC-COOH in sewage that was a relatively reversible and controllable process with multiple interactions, and then it was further confirmed by the validation experiment in a variety of actual sewage samples. According to the suggested pH, the modification of the existing detection protocol prior to high performance liquid chromatography-tandem triple quadrupole mass spectrometry (HPLC-TQ-MS/MS), was successfully applied to determination of THC-COOH in the stimulated positive samples, and the recoveries and RSDs were respectively 95.48-99.79% and 4.0-5.6%. The finding could greatly help improving the accuracy of not only the detection of THC-COOH in sewage but also the estimation data of the consumption level of cannabis in the related regions.

Kinetic modeling of the photocatalytic degradation of acetaminophen and its main transformation products

In this study, a kinetic model of the heterogeneous photocatalytic degradation of acetaminophen and its main transformation products is presented. Kinetic photocatalytic modeling and photon absorption rate modeling were included. Monte Carlo method was used to model the photon absorption process. Experiments were carried out in a reactor operated in batch mode and TiO2 nanotubes were used as photocatalyst irradiated with 254 nm UVC. Kinetic parameters were estimated from the experiments data by applying a non-linear regression procedure. Intrinsic expressions to the kinetics of acetaminophen degradation and its main transformation products were derived. Model, kinetics and photon absorption formulations and parameters proved to be affordable for describing the photocatalytic degradation of acetaminophen, but improvements should be done for better description of formation and oxidation kinetics of main transformation products. The model should be tested with other pharmaceuticals and emergent pollutants to calibrate it and evaluate its applicability in a wide range of compounds.

Dark State Concentration Dependent Emission and Dynamics of CdSe Nanoplatelet Exciton-Polaritons.

The recent surge of interest in polaritons has prompted fundamental questions about the role of dark states in strong light-matter coupling phenomena. Here, we systematically vary the relative number of dark states by controlling the number of stacked CdSe nanoplatelets confined in a Fabry-Pérot cavity. We find the emission spectrum to change significantly with an increasing number of nanoplatelets, with a gradual shift of the dominant emission intensity from the lower polariton branch to a manifold of dark states. Through accompanying calculations based on a kinetic model, this shift is rationalized by an entropic trapping of excitations by the dark state manifold, while a weak dark state dispersion due to local disorder explains their nonzero emission. Our results point toward the relevance of the dark state concentration to the optical and dynamical properties of cavity-embedded quantum emitters with ramifications for Bose-Einstein condensate formation, polariton lasing, polariton-based quantum transduction schemes, and polariton chemistry.

Synthesis and Characterization of Titania-Coated Hollow Mesoporous Hydroxyapatite Composites for Photocatalytic Degradation of Methyl Red Dye in Water

Hollow mesoporous hydroxyapatite (HM-HAP) composites coated with titania are prepared to increase the stability and catalytic performance of titania for azo dyes present in the wastewater system. In this work, HM-HAP particles were first synthesized by a hydrothermal method utilizing the CaCO3 core as a template and then coated with titania to form TiO2/HM-HAP composites. Utilizing SEM, XRD, XPS, BET, FTIR, EDS, UV–vis DRS spectroscopy, and point of zero charge (PZC) analysis, the coating morphological and physicochemical parameters of the produced samples were analyzed. The photocatalytic efficiency of the synthesized coated composites was assessed by the degradation of methyl red (MR) dye in water. The results indicated that TiO2/HM-HAP particles could efficiently photodegrade MR dye in water under UV irradiation. The 20% TiO2/HM-HAP coating exhibited high catalytic performance, and the degradation process was followed by the pseudo-first-order (PFO) kinetic model with a rate constant of 0.033. The effect of pH on the degradation process was also evaluated, and the maximum degradation was observed at pH 6. The analysis of degraded MR dye products was investigated using LC-MS and FTIR analysis. Finally, a good support material, HM-HAP for TiO2 coatings, which provides a large number of active adsorption sites and has catalytic degradation performance for MR dye, was revealed.