Kinetic Model Research Articles

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.

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.

Intensification of Cr(VI) adsorption using activated carbon adsorbent modified with ammonium persulfate

Granular activated carbon has been modified by ammonium persulfate as a new adsorbent for Cr(VI) adsorption from aqueous solutions. The adsorbent was characterized by nitrogen adsorption–desorption isotherm data and infrared spectroscopy. The impact of different factors, such as the initial pH level of the solution, time, temperature, ionic strength, and initial concentration of the Cr(VI) ion, on the adsorption efficiencies of the adsorbent has been studied by batch experiments. Kinetic studies and the adsorption thermodynamics of Cr(VI) with ammonium persulfate-modified activated carbon adsorbent were carefully studied. The results showed that the Cr(VI) adsorption follows a pseudo-second-order kinetic model and the adsorption reaction is endothermic and spontaneous. The adsorption isotherm was scrutinized, and the fitting results showed that the Langmuir model could well represent the adsorption process. The maximum adsorption capacity of Cr(VI) onto persulfate-modified activated carbon was 108.69 mg g−1. The research results showed that using persulfate-modified activated carbon adsorbent can greatly remove Cr(VI) from aqueous solutions.

A potential thermosensitive poloxamer 407-based in situ hydrogel containing moxifloxacin-loaded silk fibroin nanoparticles for prolonged ocular delivery

The aim of this study was to develop a hybrid system of thermosensitive poloxamer 407-based in situ hydrogel containing moxifloxacin-loaded silk fibroin nanoparticles (MFX-FNPs ISG) for improving the residence time of the antibacterial drug on the eye. Moxifloxacin-loaded silk fibroin nanoparticles (MFX-FNPs) were successfully formulated by absorption technique and two optimized poloxamer 407-based in situ hydrogels (ISG) were prepared by cold method. Consequently, the MFX-FNPs dispersion was embedded into these in situ hydrogels and sterilized by autoclave. Optimized MFX-FNPs displayed an average particle size of 210 nm, zeta potential of -30 mV, and moderate entrapment efficiency ∼ 44%. The hybrid system of MFX-FNPs ISG possessed homogeneous solutions with acceptable osmolality, optimal pH levels, and transmittance of ∼ 90% and manifested a pseudoplastic flow behavior at 35 °C. Furthermore, they exhibited a solution form at room temperature and quickly transformed into gel at ocular temperature. The in vitro release of MFX from MFX-FNPs ISG showed a prolonged drug release following Peppas-Sahlin kinetic model. Interestingly, the in vitro mucoadhesive study revealed that the combination systems significantly increased the residence time of the particles on the mucus membrane over 6 h compared to the solution and nanodispersion form. The prepared formulations showed effective antibacterial activity against both Staphylococcus aureus and Pseudomonas aeruginosa without causing toxicity to human corneal epithelial cells, suggesting no ocular irritation. Therefore, the MFX-FNPs ISG offer the potential to enhance the contact time of moxifloxacin on the ocular surface, thus improving the therapeutic efficacy in treating bacterial keratitis.

Efficacy of activated carbon using Salvadora persica stem for remediation of potentially toxic dyes from aqueous solution.

Potentially toxic dyes are introduced mainly to rivers through industrial effluents which have a high risk to human health and aquatic life. Activated carbon (AC) from the stem of Salvadora persica was synthesised to take off toxic industrial dyes from an aqueous solution. KOH was used as the activating agent throughout the preparation process for the AC. The morphology and composition of the prepared AC were studied by various analytical methods. From the overall results, it was found that the prepared AC is highly porous and thermal stability gained around 800 ℃. At room temperature, remediation of the dyes (cationic dye, methyl red and anionic dye, methylene blue) using the adsorption method was carried out to ascertain the impact of time and the quantity of AC on methylene blue (MB) and methyl red (MR) removal. During the initial 60min, equilibrium was attained for the optimum dye concentration (200mg/L). The data for adsorption on the AC obtained at equilibrium were examined by the Langmuir and Freundlich isothermmodels. Both the isotherms accurately predicted the data, with regression values of 0.99 for MR and 0.90 for MB, respectively. The equilibrium adsorption data was also analysed by kinetic models. The adsorption data well fittedin2nd order kinetic model. The results of MB and MR adsorption from solutions have demonstrated that the stem of Salvadora persica is one of the cheap and more eco-friendly options for remediation of toxic dyes from aqueous solutions.

Prediction of Soot in an RQL Burner Using a Semi-Detailed Jeta-1 Chemistry

Abstract The present work proposes a methodology to include accurate kinetics for soot modeling taking into account real fuel complexity in Large Eddy Simulation of aeronautical engines at a reasonable computational cost. The methodology is based on the construction of an analytically reduced kinetic mechanism describing both combustion and gaseous soot precursors growth with sufficient accuracy on selected target properties. This is achieved in several steps, starting from the selection of the detailed kinetic model for combustion and soot precursors growth, followed by the determination of a fuel surrogate model describing the complex real fuel blend. Finally the selected kinetic model is analytically reduced with the code ARCANE while controlling the error on flame properties and soot prediction for the considered fuel surrogate. To perform all evaluation and reduction tests on canonical sooting flames, a Discrete Sectional Model for soot has been implemented in Cantera. The resulting code (Cantera-soot) is now available for the fast calculation of soot production in laminar flames for any fuel. The obtained reduced kinetic scheme is finally validated in a Rich-Quench-Lean burner of the literature in terms of soot prediction capabilities by comparison of LES coupled to the Lagrangian Soot Tracking model with measurements. Results show a significant improvement of the soot level prediction when using the reduced more realistic kinetics, which also allows a more detailed analysis of the soot emission mechanisms. This demonstrates the gain in accuracy obtained with improved reduced kinetics, and validates the methodology to build such schemes.

Experimental and modeling of potassium diclofenac uptake on activated carbon.

The presence of pharmaceuticals in wastewater resulting from human activities has driven researchers to explore effective treatment methods such as adsorption using activated carbon (AC). While AC shows promise as an adsorbent, further studies are essential to comprehend its entire interaction with pharmaceuticals. This article investigates the adsorption of potassium diclofenac (PD) onto AC using experimental and modeling approaches. Batch adsorption studies coupled with Fourier transform infrared spectroscopy (FTIR) were employed to clarify the adsorption mechanism of PD on AC. Various kinetic and isotherm adsorption models were applied to analyze the adsorbent-adsorbate interaction. The kinetics were best described by Avrami's fractional order (AFO) nonlinear model. Also, the intraparticle diffusion (IP) model reveals a three-stage adsorption process. The experimental equilibrium data fitted well with the three-parameter nonlinear Liu model, indicating a maximum adsorption capacity (Qmax) of 88.45mgg-1 and suggesting monolayer or multilayer adsorption. Thermodynamic analysis showed favorable adsorption (ΔG° < 0), with an enthalpy change (ΔH° = -30.85kJmol-1) characteristic of physisorption involving hydrogen bonds and π-π interactions. The adsorption mechanism was attributed to forming a double layer (adsorbate-adsorbent and adsorbate-adsorbate).

Solar Photodegradation of a Novel des-F(6)-Fluoroquinolone, Garenoxacin, and Ecotoxicity of Its Phototransformation Products.

Garenoxacin (GRNX) is a novel des-F(6)-fluoroquinolone on the horizon; thus, its fate and risk in the aquatic environment deserve attention. This study systematically investigated, for the first time, the phototransformation of GRNX under simulated and natural sunlight and assessed the ecotoxicity of its photodegradation products. Phototransformation of GRNX was observed to depend strongly on its ionization state, with direct photolysis and self-sensitized photolysis having comparable contributions for the cationic and zwitterionic species, while the latter dominated for the anionic species. Singlet oxygen generated via the self-sensitized photolysis of GRNX was the major reactive oxygen species in its photodegradation. Phototransformation of GRNX in different ionization states followed distinct pathways, with defluorination of the difluoromethyl group occurring only for the zwitterionic and anionic species. GRNX photodegradation in natural water could be described by a simple kinetic model based on the measured steady-state concentrations of 1O2 and ·OH. Toxicity tests with Vibrio fischeri and Chlorella vulgaris consistently indicate that the generation of hydroxylation and decarboxylation products during photodegradation of GRNX increased the acute toxicity. These findings not only provide insights into the fate of GRNX in sunlit surface water but also reveal the potentially significant risk of its photodegradation products to the aquatic ecosystem.

Synthesis, application and molecular docking of modified cellulose with diaminoguanidine as complexing agent for selective separation of Cu (II), Cd (II) and Hg (II) ions from alum sample

A new modified cellulose with diaminoguanidine (Cel-Gua) synthesized for specific recovery of Cu (II), Cd (II), and Hg (II) from the alum sample. Cellulose was silanized by 3-chloropropyltrimethoxysilane and then was modified with diaminoguanidine to obtain N-donor chelating fibers. Fourier transform-infrared spectroscopy, scanning electron microscopy, X-ray diffraction, zeta potential, electrons disperse X-ray analysis, elemental analyses (C, H and N), and thermogravimetric analysis were used for characterization. Factors influencing the adsorption were thoroughly examined. Under the optimal conditions, the Cel-Gua sorbent displayed maximum adsorption capacities of 94.33, 112.10 and 95.78 mg/g for Cu (II), Cd (II), and Hg (II), respectively. The sorption process of metal ions is equipped by kinetic model PSO and Langmuir adsorption isotherm. The calculated thermodynamic variables confirmed that the adsorption of Cu (II), Cd (II) and Hg (II) by Cel-Gua sorbent is a spontaneous and exothermic process. In our study, we used the molecular operating environment software to conduct molecular docking simulations on the Cel-Gua compound. The results of the docking simulations showed that the Cel-Gua compound displayed greater potency and a stronger affinity for the Avr2 effector protein derived from Fusarium oxysporum, a fungal plant pathogen (code 5OD4). The adsorbent was stable for 7 cycles, thus allowing its safe reutilization.

Kinetic modeling of the effect of the conditions of conjugate oxidation of propane and ethylene on the yield of propylene

The study of the oxidation of propane-ethylene mixtures by numerical kinetic modeling allowed us to establish that in the range of 400–600 oC with an increase in the conversion of propane with an increase in temperature, the selectivity of propylene formation passes through a maximum, the position of which depends on the concentration of ethylene in the initial mixture. The addition of ethylene to the initial mixture leads to a reduction in propane consumption and an increase in the selectivity of propylene formation. The conditions under which ethylene introduced into the initial mixture is not consumed during the process are determined, so formally it can be considered as a catalyst, and the process of propane oxidation as proceeding in a pseudo-catalytic regime.

An Experimental and Theoretical Investigation on Highly Reusable Visible Light Active CoTe Nanosheets for Improved Photocatalytic Degradation of Toxic Aniline Blue Dye

AbstractSemiconductor‐assisted photocatalytic treatment is among the most effective methods for eliminating persistent contaminants from industrial wastewater. This study presents a hydrothermal approach for the preparation of Cobalt Telluride (CoTe) nanosheets for the degradation of aniline blue dye under visible light irradiation. The synthesized catalyst was characterized using various techniques, including X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X‐ray spectroscopy (EDX), Fourier transform infrared (FTIR) spectroscopy, RAMAN spectroscopy, high‐Resolution transmission electron microscopy (HRTEM), and X‐ray photoelectron spectroscopy (XPS). Tauc's model was used to determine the optical band gap. The key operating parameters, such as the amount of CoTe, initial aniline blue (AB) concentration, and contact time, have been optimized to achieve the highest AB degradation percentage. Under visible light, 98 % of dye degradation occurred within 60 minutes. The degradation process was further assessed using total organic carbon (TOC) measurements. Free‐radical capture experiments were conducted to identify the role of radical species in the photocatalytic process. The photocatalytic process revealed that the equilibrium data aligns well with the Langmuir‐Hinshelwood kinetic model. A rate constant of 0.03486 min−1 was obtained. The photocatalyst demonstrated excellent recyclability, maintaining efficiency and structural integrity over five cycles. The photocatalytic experiment results also have been confirmed by a density functional theory (DFT) calculation.

Valorization of toxic methylene blue dye adsorption by sodium alginate/carboxymethyl cellulose/activated carbon ternary composites

In the present study, the performance of the sodium alginate/carboxymethyl cellulose/activated carbon (SA/CMC/AC) ternary composite microbeads containing different weight ratios of AC for the adsorptive removal of hazardous methylene blue (MB) from aqueous solutions. Firstly, the composite beads were prepared by adding AC with weight ratios of 10%, 20%, and 30% concerning the polymer amount. Then the composite beads were prepared by crosslinking in 2 wt. % CaCl2 solution. Initially, adsorption studies were carried out to determine the optimum properties, and the highest performance was obtained at pH = 7 and 298 K by using the composite containing 30% AC. Adsorption data were applied to several isotherms, and the Langmuir isotherm was found to be the best isotherm model for adsorption. The highest adsorption capacity was calculated as 308.6 mg/g at 298 K using this isotherm. Studies on adsorption kinetics revealed that the process followed a quasi-second-order kinetic model. FTIR-ATR analyses showed the interactions between dye molecules and the adsorbent and also indicated that the hydroxyl and carboxyl groups functioned as active adsorption sites. Furthermore, SEM analyses proved the presence of the dye particles on the surface of the adsorbent. This study demonstrated that the produced composite microbeads may be employed as a promising adsorbent for removing cationic contaminants from aqueous solutions.

Efficacy, kinetics, inactivation mechanism and application of cold plasma in inactivating Alicyclobacillus acidoterrestris spores

As spores of Alicyclobacillus acidoterrestris can survive traditional pasteurization, this organism has been suggested as a target bacterium in the fruit juice industry. This study aimed to investigate the inactivation effect of cold plasma on A. acidoterrestris spores and the mechanism behind the inactivation. The inactivation effect was detected by the plate count method and described by kinetic models. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), the detection of dipicolinic acid (DPA) release and heat resistance detection, the detection and scavenging experiment of reactive species, and cryo-scanning electron microscopy were used to explore the mechanism of cold plasma inactivation of A. acidoterrestris. The results showed that cold plasma can effectively inactivate A. acidoterrestris spores in saline with a 3.0 ± 0.3 and 4.4 ± 0.8 log reduction in CFU/mL, for 9 and 18 min, respectively. The higher the voltage and the longer the treatment time, the stronger the overall inactivation effect. However, a lower gas flow rate may increase the probability of spore contact with reactive species, resulting in better inactivation results. The biphasic model fits the survival curves better than the Weibull model. SEM and TEM revealed that cold plasma treatment can cause varying degrees of damage to the morphology and structure of A. acidoterrestris spores, with at least 50 % sustaining severe morphological and structural damage. The DPA release and heat resistance detection showed that A. acidoterrestris spores did not germinate but died directly during the cold plasma treatment. 1O2 plays the most important role in the inactivation, while O3, H2O2 and NO3− may also be responsible for inactivation. Cold plasma treatment for 1 min reduced A. acidoterrestris spores in apple juice by 0.4 ± 0.0 log, comparable to a 12-min heat treatment at 95 °C. However, as the treatment time increased, the survival curve exhibited a significant tailing phenomenon, which was most likely caused by the various compounds in apple juice that can react with reactive species and exert a physical shielding effect on spores. Higher input power and higher gas flow rate resulted in more complete inactivation of A. acidoterrestris spores in apple juice. What's more, the high inactivation efficiency in saline indicates the cold plasma device provides a promising alternative for controlling A. acidoterrestris spores during apple washing. Overall, our study provides adequate data support and a theoretical basis for using cold plasma to inactivate A. acidoterrestris spores in the food industry.

Effects of carbonization on the structure and sorption properties of coffee grounds for Pb(II) and Ni(II) in various metal systems

Two biochars (i.e., Mu@CG and Tu@CG) derived from waste coffee grounds (CG) were prepared and muffle furnace (Mu) and tube furnace (Tu) were utilized to inspect the impact of carbonization process. It indicated that the specific surface area of Mu@CG could reach 124.26 m2/g, which was 37 times higher than that of Tu@CG (3.288 m2/g). Sorption experiments revealed that the optimal conditions were 55 °C, pH= 4, time= 10 h, and concentration was 80 mg/L for both combustion furnaces. Specifically, Mu@CG exhibited larger pore size (3.42 nm) than Tu@CG (0.015 nm), suggesting that Mu can increase the pore size of CG. The sorption of Pb(II) and Ni(II) on Mu@CG and Tu@CG followed pseudo-1st-order kinetic model. The Langmuir qm value of Mu@CG for Pb(II) was 67.037 mg/g. While, the cycle times of Mu@CG for Pb(II) and Ni(II) can be arrived at 5 times and HCl is an ideal de-sorbent for the regeneration of Mu@CG for Pb(II) and Ni(II). Further, the negative ∆G and positive ∆H data confirmed that Pb(II) and Ni(II) sorption on Mu@CG and Tu@CG were spontaneous and endothermic processes. Based on these findings, it can be concluded that for CG pyrolysis, muffle furnace will be one of the most favorable manners.

Composite flat-sheet membrane adsorbent of Li2TiO3-Ethylene-co-vinyl alcohol (LTO-EVAL) for lithium extraction

Composite bead adsorbents have been prevalent for the extraction of Li+ from brines. However, adsorbent beads generally demonstrate declining adsorption capacity and require extended equilibrium time when used repeatedly in absorption/desorption cycles. To overcome this challenge, a novel composite flat-sheet membrane adsorbent based on ethylene-co-vinyl alcohol (EVAL) and Li2TiO3 (LTO) is reported herein for highly efficient Li+ extraction from a geothermal brine. At an optimal LTO loading and membrane thickness, the resulting LTO-EVAL membrane was characterized by a large open macrovoid structure for fast ion transport, a fast adsorption rate that reached equilibrium in 0.5 h, and a high capacity of 96 % of that of the powder. The new membrane adsorbent showed adsorption behavior consistent with the Langmuir model and pseudo-second-order kinetic model. For a geothermal brine with a low lithium concentration, the LTO-EVAL membrane showed stable performance in 13 rapid adsorption/desorption cycles, with adsorption capacity at an average adsorption capacity of 7.3 mg/g and a 70 % adsorption efficiency. The average dissolution rate of Ti4+ was below 0.6 % in each cycle. The structure of the adsorbent material showed no discernable changes in chemical structure as confirmed by XRD and SEM results. With the improved extraction efficiency, the reusable membrane adsorbents would be economically viable in the long run and could potentially serve as the next generation of scalable Li+ adsorption material for brines. Further utilization of membrane adsorbent would lead to new design of adsorption modules and systems with reduced footprint. We need to further optimize the stability of the membrane adsorbents so that loss of Li2TiO3 remain at low level to reduce the lost for lithium extraction from the geothermal brine.

Quinoline and cholesterol based organogelator for selective adsorption of cationic dyes

A novel quinoline and cholesterol based organogelator G1 has been successfully synthesized and characterized. G1 could form stable organogels in ethanol, n-propanol, n-butanol, isobutanol, acetone and ethyl acetate (EA), and the concentration-dependent 1HNMR revealed that hydrogen bonding, π-π stacking and van der Walls interaction were the main driving force to form organogels via the self-assembly of G1. Furthermore, the G1-EA gel realized selective adsorption properties for cationic dyes, such as malachite green (MG), brilliant green (BG), rhodamine B (RB) and crystal violet (CV). The results revealed that at pH = 9.90, c0 = 18 mg·L−1, the adsorption process of G1-EA gel for MG reached equilibrium in 7 h, and the removal rate was 99.13 %. The selective adsorption experiments of the G1-EA gel indicated that the cationic dyes (MG and BG) were efficiently adsorbed out of the mixed dyes solutions. Also, the adsorption isotherm and the adsorption kinetics for the adsorption process were investigated, the results suggested that the Freundlich equation and the quasi-second-order kinetic model were more appropriate to describe the adsorption process.

Performance and mechanism of sulfadiazine and norfloxacin adsorption from aqueous solution by magnetic coconut shell biochar.

In this study, magnetic coconut shell biochar loaded with spherical Fe3O4 and γ-Fe2O3 particles was successfully synthesized using a chemical coprecipitation method. The magnetic biochar exhibited a good magnetic separability and environmental security. The maximum sulfadiazine (SDZ) and norfloxacin (NOR) removal efficiencies were 94.8% and 92.3% at pH 4 and 25°C with adsorbent dosage of 2.5g/L, respectively. When antibiotic concentrations ranged from 5 to 50mg/L, the theoretical maximum adsorption capacities of SDZ and NOR were 16.7mg/g and 25.8mg/g, respectively. The Langmuir isotherm and pseudo-second-order kinetic models could better describe the adsorption process of both antibiotics, implying the monolayer chemical adsorption. The thermodynamic analysis indicated that the adsorption process was spontaneous and endothermic. The ionic strength had no significant effect on the adsorption behavior of either antibiotic. Combined with BET, FTIR, and XPS results, the dominant mechanisms for SDZ and NOR adsorption were pore filling, π-π electron-donor-acceptor interaction, hydrogen bonds and surface complexation. Moreover, Lewis acid-base interaction also contributed to SDZ adsorption.

Degradation Kinetics of Antifouling Biocides in Sediment During the Spiking Equilibrium Phase

The new generation of antifouling biocides, as well as other emerging contaminants, has not yet been included in sediment quality guidelines or present standard protocols for sediment spiking. Most of these biocides have short half-lives in water, but little information is available regarding their degradation in sediments. Thus, there is a need to establish a reliable duration of the equilibrium phase for sediment spiking prior to sediment toxicity testing to determine the actual exposure concentrations during ecotoxicological tests. This study aimed to evaluate the degradation of DCOIT, Irgarol, Diuron, and Dichlofluanid during a spiking equilibrium phase of 24 h at three different time intervals (0, 6, and 24 h) and concentrations (10, 100, and 1000 ng g-1), by applying kinetic degradation models. The models presented a better fit for the 1000 ng g-1 treatments, in which the half-lives of DCOIT and Diuron were &lt; 5 h, Dichlofluanid &lt; 2 h, and Irgarol &lt; 6h. Our results also indicate that, except for Dichlofluanid, the degradation rates of the other antifouling biocides were reduced dramatically after 6 h of equilibrium. Therefore, an equilibrium phase of 24 h (or greater than 6 h) was considered viable for sediment spiking. Our findings provide valuable information to guide future sediment toxicity tests using these compounds.

Fabrication of graphitic carbon nitride/gum Arabic/potassium carrageenan composite for efficient adsorption of erythromycin: Kinetic and thermodynamic studies

Erythromycin (ERY) molecules are robust to the environment and hard to remove due to their aromatic structure. Nowadays, numerous researches have reported that the ERY amount in water is above the standard level and its removal is necessary. Here, we prepared three solid adsorbents: graphitic carbon nitride (g-C3N4), potassium carrageenan beads (Cr), and graphitic carbon nitride/gum Arabic/potassium carrageenan composite (g-ACr). Several techniques such as XRD, SEM, TEM, TGA, ATR-FTIR, Zeta potential, and N2 adsorption were employed to characterize the fabricated adsorbents. Five essential factors of adsorbent dose, initial ERY concentration, contact time, temperature, and pH were optimized to investigate the batch adsorption of ERY. The maximum adsorption capacity of 356.12 mg/g was attained by g-ACr composite at an adsorbent dose of 1.25 g/L, contact time of 6 h, and pH 7 at 15 °C. The data showed that the experimental findings exhibited the best agreement with Langmuir, Temkin, and DR isotherm models, in addition to the kinetic models of pseudo-second-order, Elovich, and intra-particle diffusion. The evaluated thermodynamic factors designated that the ERY adsorption is endothermic, physisorption, favorable, and spontaneous process. The g-ACr reusability displayed a decline in the adsorption capacity after seven adsorption/desorption runs by 5.7 %. Finally, this work outcomes depict that g-ACr composite is an efficient reusable adsorbent for ERY elimination from wastewater.