Second-order Kinetic Equation Research Articles

Investigation of photocatalytic malachite green degradation by iridium doped zinc oxide nanoparticles: Application of response surface methodology

Advanced oxidation process is a rapidly expanding technology for wastewater treatment. In the current case study, the design of experiments (DOE) which is based on response surface methodology (RSM), was employed for the investigation of the effective parameters of malachite green (MG) degradation from aqueous medium. Three independent factors involving concentration of dye, the amount of the chemical oxidant and amount of iridium (Ir) as a doping agent on the MG degradation were examined in detail. Based on the results obtained from RSM analyses, an optimum pathway to reach the high MG degradation rate (>90%) under visible light was achieved by applying 10 ppm of MG concentration, 0.3224 mmol of chemical oxidant with 5% Ir doped ZnO. The experimental results proved to be in reasonable agreement with the derived response model with R2 > 0.98. The synthesized photocatalyst was in detail characterized. The photocatalytic degradation of MG at different conditions was found to be fit with the second-order kinetic equation, as the best choice for efficiency, which describes the behavior of dyes adsorption.

Polymyxin B immobilized nanofiber sponge for endotoxin adsorption

Nanofiber sponge, which showed high porosity and excellent blood compatibility, was successfully prepared by electrospinning and freeze-drying technology. The APTT (activated partial thromboplastin time) and PT (prothrombin time) of human plasma with nanofiber sponge were a little longer than control groups, which revealed the nanofiber sponge has excellent blood compatibility. By activating the carboxyl groups on the fibers, PMB (polymyxin B) was successfully immobilized on the nanofiber sponge. The adsorption performance was researched in different solutions. The adsorption capacity in physiological saline solution was around 17,889 EU/mL and the adsorption equilibrium time was about 40 min. The adsorption behavior not only obeyed to second-order kinetic equation, but also was conformed to Langmuir model, which turned out to be chemical adsorption and monolayer adsorption. The endotoxin removal rate in BSA (bovine serum albumin) physiological saline solution was about 96.6%, and the BSA recovery rate was around 75.6%, which indicated the PMB immobilized nanofiber sponge adsorbed endotoxin selectively. The endotoxin removal rate of normal nanofiber sponge was about 17.3%, while it was around 99.6% when it comes to PMB immobilized-nanofiber sponge, which manifested PMB played an important role in endotoxin adsorption. The endotoxin removal rate in human plasma reached 90%, and the adsorption reached equilibrium within 60 min, which proved the PMB immobilized-nanofiber sponge would have great potential for applying in clinical blood purification.

Kinetic Model of Batch Sorption Processes: Comparing Calculated and Experimental Data

The possibility of deriving a model of the kinetics of batch sorption processes is considered by transforming a nonlinear difference kinetic equation with a nonconstant equilibrium parameter for the interface into approximate pseudo first- and second-order equations with fixed parameters, depending on the characteristic of equilibrium isotherms in a certain way. The calculated and experimental equilibrium and kinetic parameters are compared for a large number of processes, including the sorption and electrosorption of metal ions on activated coals, the sorption of lead on nanostructured carbon materials, and phosphatidylcholine sorption on ordered mesoporous nanostructured silica materials. Good coincidence is observed between the calculated equilibrium data and the respective experimental results obtained in kinetic experiments. At the same time, there is no correspondence between calculated and experimental dimensionless parameters based on the relationships of kinetic coefficients for different order equations (due apparently to great errors in determining these coefficients when processing the experimental data using the pseudo second-order model of kinetics). The obtained results confirm earlier conclusions that it is impossible to characterize the mechanisms of kinetic processes based only on good descriptions of experimental results using pseudo first- or second-order kinetic equations.

Kinetic Models of Batch Sorption in a Limited Volume

The batch sorption kinetics described by a nonlinear equation with a variable equilibrium parameter for the interface was considered. It was shown that a difference equation of this type can be reduced, with a certain approximation, to the pseudo first- and pseudo second-order kinetic equations with constant parameters that are convenient for processing the experimental data. The errors of this approximation are smaller than the characteristic experimental errors in constructing the kinetic curves. For the linear sorption isotherm and Langmuir isotherm, the sorption kinetics can be approximated by the pseudo first-order equation. In addition, for the Langmuir isotherm and BET isotherm of polymolecular sorption, the kinetics can be described by the sum of the pseudo first- and pseudo second-order equations, or only by the pseudo second-order equation. For all these cases, it was shown how the parameters of kinetic equations are related with the equilibrium characteristics of sorbents. Our analysis shows that the possibility of describing the experimental data obtained in batch kinetic experiments using pseudo first- or pseudo second-order models is related to the possibility of mathematical approximations and transformations and cannot be used to characterize the kinetic mechanisms.

Utilization of lime-softening sludge to obtain calcium nitrate

The given research is devoted to the development of the technology of utilization of lime-softening sludge to obtain calcium nitrate.Water treatment waste by chemical composition differs from natural raw materials such as limestone, which is traditionally used to obtain calcium nitrate. Sludge obtained at the stage of lime-softening contains about 70% calcium carbonate, a fairly large amount of iron, which enters the precipitate with solutions of coagulants, as well as organic impurities. Organic impurities come from river water and precipitate as a result of coagulation.The process of extracting calcium by the acid solution is stable. The results are well reproduced on two kinds of waste from different enterprises. This is explained both by the high dissolution rate of calcium carbonate in nitric acid, and the similar chemical composition of the waste.Not only calcium compounds, but also iron ones together with the organic component of liming sludge fall into the solution. A process scheme is proposed for cleaning the solution, which should include the stages of oxidation of the solution and subsequent precipitation of iron.The concentration of iron in the experimental solutions was up to 6 g/l. With the help of the calculations of the precipitate-solution equilibrium, it has been stated that iron in the area of low concentrations of nitric acid precipitates in the solution, and calcium stays in it. The decrease of the acid concentration was carried out by the addition of pure calcium carbonate.Kinetic studies of the process of iron precipitation on model solutions of iron (III) nitrate have been carried out. The second-order kinetic equation is obtained. The calculation of the process activation energy is available in the paper. The value of the energy is ~37 kJ/ mole, which is the evidence of the precipitation process in the transition area. The undissolved residue contains about 40% iron and can be used to obtain coagulants.Thus, the application of the proposed method will allow the best use of water treatment waste

Preparation of magnetic nanocomposite based on polyaniline/Fe3O4 towards removal of lead (II) ions from real samples

In the present study, the surface of the magnetic nanoparticles was modified by cetyltrimethylammonium bromide and polyaniline polymer. The modified nanocomposite was examined as a strong absorbent for the removal of lead ions (II) from the industrial effluent samples. In order to characterize the nanocomposite, a transmission electron microscope was used to determine the exact size of the nanoparticles and the BET technique was used to determine the effective absorbent level. Moreover, CHNS and TGA analyses were used, respectively, to confirm the coating of polyaniline polymer on Fe3O4 magnetic nanoparticles and to study the thermal stability of the modified nanocomposite. Atomic absorption spectrophotometer was also used to determine the amount of lead ion in the solution. Characteristics that influence the removal of lead ions, including pH, adsorbent amount and contact time, were optimized at various temperatures. The optimal pH was obtained to be 9.3, the optimal amount of adsorbent was determined as 3 mg and the optimal contact time was obtained to be 60 min. In addition, this study was conducted to investigate the lead ion (II) in true samples with appropriate substrates. The equilibrium data obtained from the lead adsorption on nanocomposite showed better fitting by Langmuir isotherm compared to Freundlich isotherm. Furthermore, the maximum lead (II) adsorption capacity on Polyaniline/Fe3O4 nanocomposite was 111.11 mg/g. Kinetic studies also showed that the adsorption process followed the pseudo second-order kinetics equation.

STUDY OF CADMIUM OCTA(4-METHOXYPHENYL)PORPHYRINATE IN REACTION OF METAL EXCHANGE WITH TIN CHLORIDE IN DMF

Metal-exchange reaction for complexes with macrocyclic ligands refers to a special type of complex coordination interactions. The reaction of metal exchange has founded wide application for the synthesis of complexes of natural and synthetic porphyrins. In the general form, the metal-exchange reaction may be written as follows:MР + M/Xn(Solv)m-n® M/Р + MXn(Solv)m-nwhere МP and M/P are metalloporphyrins, M/Xn(Solv)m-n are metal salts of solvate complexes. Cd-octa(4-methoxyphenyl)porphyrin was obtained by the reaction of octa(4-methoxyphenyl)-porphyrin-ligand with cadmium chloride in the presence of potassium acetate in dime-thylformamide. The obtained compound was identified by the methods of UV-VIS spectroscopy, 1H NMR and mass-spectrometry. The reaction order on the salt and the complex of cadmium in the case of the reactions of the Cd-octa(4-methoxyphenyl)porphyrin metal-exchange with tin chloride in dimethylformamide is equal to 1. Thus, the metal-exchange reaction is bimolecular and its total rate obeys to the second-order kinetic equation. It is suggested that the metal-exchange reaction of Cd-оcta(4-methoxyphenyl)porphyrin with tin chloride in dimethyl-formamide proceeds through a bimolecular associative mechanism.

Four different kinds of peels as adsorbents for the removal of Cd (II) from aqueous solution: Kinetics, isotherm and mechanism

Abstract In this paper, the four agricultural wastes of litchi peel (LP), orange peel (OP), pomegranate peel (PP) and banana peel (BP) were used as the adsorption material, their adsorption properties on Cd (Ⅱ) were studied. The materials were characterized by SEM, FT-IR, Zeta and BET. Structural characterization indicated that the peels can be used as adsorption material containing a variety of functional groups, rough and porous surface. The maximum adsorption capacities were up to 230.5, 170.3, 132.5, 98.4 mg/g for LP, OP, PP and BP respectively. The adsorption ability of the four peels for Cd (Ⅱ) was: LP>OP>PP>BP. The adsorption isotherms of the four peels were best described by the Langmuir model, and their adsorption kinetics followed the pseudo second-order kinetic equation. After 10 cycles of adsorption–desorption experiments, there was no significant change in the adsorption capacity. These findings suggest that the agricultural wastes could be potentially applied to the efficient removal of heavy metal ions from waste water.

Modified Sugarcane Bagasse with Tartaric Acid for Removal of Diazonium Blue from Aqueous Solutions

The present study concerns with exploring the possibility of using of tartaric acid pretreated sugarcane bagasse (SCB) for removing diazonium blue (DB) from aqueous solutions. The effect of different factors on the efficiency of the adsorbent for the DB dye removal was investigated, including initial dye concentration, contact time, SCB dosage and SCB particle size. Langmuir, Freundlich, Tempkin and D–R isothermal models have been employed to analyze the adsorption equilibrium data. It was found that the adsorption of the dye fits well with the D–R model. The adsorption kinetics was also done applying four kinetic models. The regression equation coefficients refer to fitting the data to the second-order kinetic equation for removal of the DB dye. It is probable that the rate limiting step is a chemical adsorption between the adsorbent and the dye. This chemisorption process is further confirmed from the energy value of 15.1 kJ mol−1 deduced from the D–R isotherm.

Synthesis and application studies of chitosan acryloylthiourea derivative for the separation of rare earth elements

ABSTRACTThe adsorption behaviors of lanthanum (III) from an aqueous chloride medium, using Chitosan acryloylthiourea (CATU) derivative, were studied using an equilibrium batch technique. Here, the chemical modification of chitosan is of interest because the modification would not change the fundamental skeleton of chitosan, would keep the original physicochemical and biochemical properties, and finally would bring new or improved properties. The optimum pH value was defined to be 5.0 at a temperature of 298 K. Kinetic and isotherm experiments were carried out at the optimum pH. It was enough to reach the adsorption equilibrium at 4 hours and the maximum uptake capacity was 2.1 mmol g−1 at 25°C. Complexion, ion exchange, and electrostatic interaction were all believed to play a role in lanthanum adsorption on CATU derivative. The equilibrium adsorption data were fitted to a second-order kinetic equation. The Langmuir adsorption isotherm models were used to describe the adsorption process. The proposed method was validated and successfully applied for the determination of lanthanum in certified reference samples and ore sample with satisfactory results. The elution experiment was carried out by 0.05 mol/L CaCl2 as an eluent.

Bioremediation of Diesel-contaminated Soil by Composting with Locally Generated Bulking Agents

ABSTRACTHerein, we conducted a study toward understanding the impact of composting of the diesel-contaminated soil with some locally available bulking agents (rice husks (RHs), sawdust (SD), and wood chips (WCs)). In order to ascertain the effectiveness of petroleum degradation by the process assayed, we compared the protocols with monitored natural attenuation (MNA). The overall degradation pattern was modeled with non-linear regression by comparing the experimental data with first and second-order kinetic equations. At the end of the six-week study, the amount of total petroleum hydrocarbon removed from contaminated soil was 98.26 ± 1.33% (amendment with SD + RHs + WCs), 96.89 ± 1.20 (RHs amendment), 96.55 ± 1.29% (amendment with SD), 90.01 ± 0.22% (WCs amendment), and 85.02 ± 0.21% (MNA). The degradation of TPH trends followed a second-order kinetic model for all the four compost treatments while the MNA was found to follow a first-order (slower) degradation pattern. In general, the results of the parameter estimate showed that amendment with mixture of the three bulking agents was 1.08 (8%) slower (k2 = (1.289 ± 0.16) × 10−5 (g mg−1 d−1), r2 = 0.991) than SD amendment alone (k2 = (1.392 ± 0.14) × 10−5 (g mg−1 d−1), r2 = 0.995). However, the mixture of the bulking agents was found to be 1.67, 1.41, and 2.4 times faster than amendments with WCs, rice, and MNA, respectively. The phytotoxicity test revealed that all the compost treatments except WCs resulted in germination index of ≥80% after six weeks of bioremediation tests. The outcome of the current investigation confirms the effectiveness of bulking agents (especially when combined) in the supply of nutrients for the bioremediation of diesel-impacted soil.

Predicting trace organic compound attenuation by ozone oxidation: Development of indicator and surrogate models

Ozone oxidation has been demonstrated to be an effective treatment process for the attenuation of trace organic compounds (TOrCs); however, predicting TOrC attenuation by ozone processes is challenging in wastewaters. Since ozone is rapidly consumed, determining the exposure times of ozone and hydroxyl radical proves to be difficult. As direct potable reuse schemes continue to gain traction, there is an increasing need for the development of real-time monitoring strategies for TOrC abatement in ozone oxidation processes. Hence, this study is primarily aimed at developing indicator and surrogate models for the prediction of TOrC attenuation by ozone oxidation. To this end, the second-order kinetic equations with a second-phase Rct value (ratio of hydroxyl radical exposure to molecular ozone exposure) were used to calculate comparative kinetics of TOrC attenuation and the reduction of indicator and spectroscopic surrogate parameters, including UV absorbance at 254 nm (UVA254) and total fluorescence (TF). The developed indicator model using meprobamate as an indicator compound and the surrogate models with UVA254 and TF exhibited good predictive power for the attenuation of 13 kinetically distinct TOrCs in five filtered and unfiltered wastewater effluents (R2 values > 0.8). This study is intended to help provide a guideline for the implementation of indicator/surrogate models for real-time monitoring of TOrC abatement with ozone processes and integrate them into a regulatory framework in water reuse.

Adsorption and desorption characteristics of endosulfan in two typical agricultural soils in Southwest China.

Endosulfan is an organochlorine pesticide widely used in Southwest China. In this paper, the adsorption and desorption characteristics of endosulfan in two typical agricultural soils (latosol and lateritic red soil) in this area were studied. The results showed that Langmuir isothermal equation could well describe the adsorption thermodynamic characteristics of endosulfan in latosol and lateritic red soil, and the maximum adsorption capacities of α-endosulfan were 0.186 and 0.209 mg/g, while those of β-endosulfan were 0.140 and 0.148 mg/g, respectively. Endosulfan adsorption in the two soils was an exothermic physicochemical process, but dominated by physical process. The adsorption kinetic characteristics of endosulfan in the two soils could be well described by second-order kinetic equation, and the initial rate constants were 0.228 and 0.325 mg/(gmin) for α-endosulfan, while those were 0.119 and 0.125 mg/(gmin) for β-endosulfan, respectively. The adsorbed endosulfan in the two soils was difficult to be desorbed into the liquid phase, and showed weak desorption hysteresis. These results implied that endosulfan could be firmly adsorbed by the two soils, and their adsorption and desorption abilities may be related to the contents of soil clay and organic matter.

Viability kinetics of Lactobacillus casei Shirota strain in a commercial fermented milk drink during refrigerated storage

Background: One of the most important parameters in a commercial fermented milk drink containing probiotics is the viability of the microorganisms. Aims and Objectives: This study described the viability kinetics of Lactobacillus casei Shirota strain in a commercial fermented milk drink during refrigerated storage using nonlinear models. Materials and Methods: Viability of L. casei Shirota strain was monitored during refrigerated storage using standard bacterial plate count method. Several nonlinear mathematical models such as the zero-order, first-order, and second-order kinetic equations were employed in describing the population dynamics. Best-fit models were selected based on prescribed criteria including sum of squares of the error, p-value, and coefficient of determination. Results: The viable counts of L. casei Shirota strain in the fermented milk samples stored under refrigerated conditions decreased from 3.73 × 108 colony forming units per ml (CFU/ml) to 2.70 × 108 CFU/ml when monitored every 3-4 days interval over 10 different monitoring points within the product’s indicated shelf life. The counts significantly differed between the monitoring points that were at least 14 days apart. The lowest viable count was still within the recommended therapeutic dose. The decrease in the bacterial population behaved under a second-order kinetic relationship. Conclusion: The viability of L. casei Shirota strain in a commercial fermented milk product during refrigerated storage is governed in accordance with the second-order kinetic mechanism.

改性牡蛎壳及其吸附除磷性能研究

本文以铝盐、铁盐为原料，对牡蛎壳进行改性，研究了改性牡蛎壳吸附除磷性能。实验表明，改性牡蛎壳吸附除磷过程符合Langmuir等温吸附方程，其吸附动力学与准二级方程拟合最佳。改性牡蛎壳对磷的理论饱和吸附量为20~30 mg P (以 计)/g吸附剂，是未改性的5倍左右。通过KCl-NaOH-HCl逐级浸提法分析得知，吸附饱和后吸附剂中磷以钙磷结合、铝磷结合或铁磷结合形态存在。改性牡蛎壳对模拟含磷废水除磷率在90%以上，天然牡蛎壳只有41%。 The oyster shell was modified through ferric salt and aluminum salt, and the performance of modified oyster shell for phosphorus removal was examined. Results indicated that the adsorption processes of phosphorus by modified oyster shell were in conformity with Langmuir isothermal adsorption equation, while the relevant adsorption followed the second-order kinetic equation. The theoretical saturated adsorption capacity of the modified oyster shell was 20 - 30 mg P ( )/g, which was 5-folds higher than that of original oyster shell. Analysis of KCl-NaOH-HCl sequential extraction showed that the phosphorus speciation in saturated adsorbents was in the form of Ca-bound P, Al-bound P or Fe-bound P. More than 90% of phosphorus was removed with modified oyster shell from artificial wastewater, whereas only 41% was removed with original oyster shell.

Au (III) uptake by triazine polyamine polymers: Mechanism, kinetic and equilibrium studies

Triazine-polyamine polymers were successfully synthesized and adsorption of the gold (III) ions from chloride-containing solutions was carried out by comparing the effect of amine chain lengths in the polymers triazine-ethylenediamine (EDA), triazine-triethylenetetramine (TETA) and triazine-pentaethylene hexamine (PEHA). The second-order kinetic equation provides the best correlation for the adsorption process. Langmuir equation has a good fit for all the adsorption systems. Langmuir monolayer adsorption capacities of the EDA, TETA and PEHA polymers were 548, 1003 and 1086mg/g, respectively. Adsorption mechanism was determined using FTIR, XPS, SEM, SEM Mapping and EDS. Adsorption mechanism is followed by ionic and surface complex formation mechanisms. Hydroxy chloro gold complexes were more interacted with nitrogen atoms of amine groups in polymers than nitrogen atoms in triazine rings. The adsorption capacity did not decrease after using all polymers five times. Furthermore, elution of the adsorbed Au (III) ions was made easily using 3% (m/v) thiourea solution in 1M HCl. From the results, it was concluded that EDA, TETA and PEHA polymers have a high gold uptake capacity and are highly efficient for the recycling of gold.

A sandwich-structured graphene-based composite: Preparation, characterization, and its adsorption behaviors for Congo red

In this work, a novel sandwich-structured graphene-based composite (PPD-GO) was prepared. The graphene-based composite was prepared by amination of graphene oxide (GO) with p-phenylenediamine (PPD) with the aid of the coupling reagents. And PPD was introduced into the interlayers of graphene nanosheets. The morphology, composition, and grafted functional groups of the composite were investigated by scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. And PPD-GO was used as a highly efficient adsorbent for removal of Congo red from used from aqueous solutions. The whole adsorption process was studied in depth and elucidated systematically. A maximum Congo red adsorption capacity of 892.8 mg/g was obtained for PPD-GO composite at an initial temperature of 298 K and pH of 3.0. The second-order kinetic equation could well describe the sorption kinetics. The equilibrium data were perfectly fitted by the Langmuir isotherm. The thermodynamic analysis indicated that the adsorption of Congo red onto the PPD-GO composite was a spontaneous and endothermic process.

Adsorption of Hg(Ⅱ) in Water by Sulfydryl-Modified Sepiolite

In order to develop highly efficient and low-cost treatment technique for heavy metal wastewater and promote the resource utilization of sepiolite, natural sepiolite was modified by using thioglycollic acid and characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), specific surface, Zeta potential and infrared spectrum (IR) analysis, and the adsorption kinetic and thermodynamic characteristics of the modified sepiolite to Hg(Ⅱ) in water were studied by static adsorption experiments. The results showed that sulfydryl groups were grafted onto sepiolite, and the surface of the modified sepiolite became smoother with more gaps and negative charges to improve the adsorption ability for Hg(Ⅱ). The optimal pH for Hg(Ⅱ) adsorption on the modified sepiolite was 6, and the adsorption process reached equilibrium in 60 min at 30℃. This process could be described by the pseudo second-order kinetic equation, and the initial adsorption rate constant was 0.063 mg·(g·min)^-1. The adsorption thermodynamic characteristics could be well described by Langmuir isothermal adsorption model, and the maximum adsorption capacity was 3.256 mg·g^-1. The investigation revealed that the adsorption process was a spontaneous endothermic process, resulting in physical adsorption and chemical adsorption, which was dominated by physical adsorption.

Effects of Sulfur/sponge Iron Ratio for Deep Denitrification and Phosphorus Removal of Reclaimed Water

To study the effects of sulfur/sponge iron ratio on denitrification and phosphorus removal, a series of static experiments were conducted using different ratios of sulfur and sponge iron. The results showed that the denitrification and phosphorus removal effect of sulfur/sponge iron composite fillers was significantly higher than that of single filler, and sulfur/sponge iron ratio was one of the key factors influencing nitrogen and phosphorus removal by composite fillers. When the volume ratio was equal to or greater than 1:1, the removal efficiency of TN and TP reached 85% and 97%, respectively. The denitrification and phosphorus removal process of the composite fillers both fitted second-order kinetic equation, the denitrification was dependent on heterotrophic denitrification and sulfur autotrophic denitrification; the phosphorus removal was mainly chemical phosphorus removal caused by sponge iron corrosion.

Equilibrium, kinetic, and thermodynamic studies of adsorption of Sr(II) from aqueous solution onto GMZ bentonite

Due to low hydraulic conductivity, high swelling capacity, and good adsorption properties, the Gaomiaozi (GMZ) bentonite has been proposed as one of the most suitable buffer/backfill materials for the construction of engineering barriers in geological repository for high-level nuclear waste disposal in China. In this study, the adsorption of Sr(II) on the GMZ bentonite was studied using the batch technique, and the effects of contact time, pH, ionic strength, temperature, and concentration were analyzed. The results obtained from the tests show that the adsorption process achieved equilibrium within 60 min, and the adsorption capacity for Sr(II) by the GMZ bentonite was about 9.72 mg/g under the given experimental conditions. The equilibrium adsorption data were fitted to the second-order kinetic equation. The adsorption capacity for Sr(II) onto the GMZ bentonite increases with increasing pH from 3 to 13 but decreases with increasing ionic strength from 0 to 1.0-M NaCl. Maximum adsorption at a temperature of 298.15 K was determined to be achieved at pH ≥7. The adsorption reaction was exothermic, and the process of adsorption was favored at low temperature. The adsorption of Sr(II) was dominated by ion exchange. Furthermore, the D–R adsorption isotherm model was used for the description of the adsorption process.