Magnetic fibrous silica mesoporous system for selective and efficient removal of divalent cadmium ions

Tech 2023-05-28 16:10:34 Source: Network

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Wen | Pan Hu Says

Editor | Pan Hu Says

Preface

In this study, the efficiency of iron in removing cadmium ions from aqueous solutions was a simple and effective adsorbent.The prepared adsorbent was synthesized in a short period of time using microwave assisted hydrothermal method.

The results indicate that the model has ideal ability in predicting the removal rate of divalent cadmium ions in aqueous solutions.

Introduction

The United States Environmental Protection Agency has classified heavy metals such as cadmium, mercury, arsenic, nickel, lead, and cadmium as toxic environmental pollutants.Chemical and other industries incorporate these heavy metals into the environmental cycle and its ecology, such as water, agricultural products, and the human body.Due to the fact that many heavy metals can cause various diseases in humans, their entry into the environment has always been a concern.

Therefore,It is necessary to find efficient and high-performance suitable methods to eliminate these toxic metals,Many efforts have been made to reduce and eliminate heavy metals, such as chemical precipitation, ion exchange, reverse osmosis, membrane treatment, evaporation, solvent extraction, and adsorption. Cadmium, mercury, arsenic, nickel, lead, and cadmium

Compared with other methods, adsorption method has advantages in initial cost, wastewater reuse, design simplicity and flexibility, and ease of operationMore attention has been paid to the insensitivity to pollutants and toxic compounds, as well as the lack of free radicals.

Nanoparticle adsorption of metals is an environmentally friendly technology,In recent years, it has been studied as an effective reagent for removing organic pollutants and heavy metal ions from water and wastewater.

KCC-1 (KAUST catalytic center) is a mesoporous silica with a spherical fiber morphology and a dandelion like structure,

The combination of the surface properties of porous silica and the magnetism of magnetic nanoparticles can achieve a structure with multiple functions.

Fibrous silica mesopores were synthesized by sol-gel method and tetraethyl orthosilicate polymerization, and were magnetized by magnetic nanoparticles.

Therefore,

Statistical models have been used to optimize various processes in many disciplines. The statistical models used in the experimental design include the response surface method, which is used to optimize the process where the required response is influenced by a large number of variables.

Through this method, the number of experiments and the predictability of quadratic regression coefficients are reduced, as well as how to use the influence of independent variables to measure the relationship between one or more responses.:

Magnetic fibrous silica mesoporous materials were prepared by sol-gel method.This material has a highly ordered pore structure and a large specific surface area, which can provide a large number of adsorption sites.

Optimize using response surface methodology to determine the optimal operating conditions and parameters.pH

By designing a series of experiments, collecting corresponding data, and applying response surface methodology to analyze these data.A mathematical model was established between the removal rate of divalent cadmium ions and operating conditions through regression analysis.

Using this mathematical model, the optimal operating conditions were determined to achieve the highest removal rate of divalent cadmium ions.This optimization process can improve removal efficiency and maximize the adsorption capacity of magnetic fibrous silica mesopores.

The main purpose of this study is to investigate the adsorption efficiency of synthesized magnetic fibrous mesoporous silica as a new adsorbent for divalent cadmium ions in aqueous solutions, and to determine the optimal adsorption conditions using response surface methodology.

Experiment related

All reagents used are analytical grade, and the solution is prepared with deionized water.Deionized water is obtained through a device used for drug purification of water.

The concentration of cadmium in the solution was read by WFX-210 atomic absorption spectroscopy (Rayleigh model).After the adsorption process, the adsorbent is separated from the solution using a centrifugal instrument. The powder X-ray diffraction spectrum was obtained using a maximum 2400 diffractometer using Cu Ka radiation.

Use iron to synthesize iron oxide nanoparticles 2+and iron 3+in basic media through coprecipitation.

Add approximately 150 milliliters of ammonia solution drop by drop, as long as the pH remains constant within the range of 9 to 10.In the process of adding ammonia, the color of the solution gradually changed from orange to brown and then to black, indicating the formation of iron 3O4 nanoparticles.

To achieve this, 0.1g of iron oxide nanoparticles were dispersed in a mixture of 80mL ethanol and 20mL water as solvents, as well as 0.5mL 28% ammonia as catalysts, sonicated for 30 minutes, and then stirred for 15 minutes.

Then add 0.1g of tetraethyl orthosilicate dropwise under stirring as the precursor.Place the solution in a strong sterilizer at room temperature for 12 hours.

The experiment used batch adsorption experiments to study the adsorption of divalent cadmium by iron in aqueous solutions. The experiment was conducted in a 100ml conical flask containing 50ml of a known concentration of divalent cadmium solution and the required amount of adsorbent.

Before mixing with the adsorbent, adjust the pH of each cadmium solution to the desired value of 3 by adding 0.1 mL of sodium hydroxide or 0.1 mL of nitric acid.In a typical experiment, the Stoke solution of cadmium is diluted with deionized water to obtain the concentration of other solutions.

The mixture was mechanically stirred to reach equilibrium, and then the adsorbent was taken out of the solution by magnetic separation using a magnet, and the residual concentration of metal ions in the solution was measured using a WFX-210 atomic absorption spectrometer (Rayleigh type).

Results

The infrared spectroscopic record of iron shows that the presence of fibrous silica shells can be confirmed by their characteristic spectral band at 1089 cm.

3431O-H16311The peak at 565 cm is due to Fe-O stretching vibration, which is similar to magnetite.

The morphology and particle size of iron were studied by scanning electron microscope. The image of the standard electronic module of the prepared iron can be seen that it has a monodisperse and uniform shape of radial fiber structure spheres.This fiber structure facilitates mass transfer and increases the accessibility of active sites.

The normal probability map is a graphical tool for comparing data sets with normal distribution.It can be used in conjunction with the standardized residuals of linear regression models. The normal probability and student residual plot show that it can be used for the removal of divalent cadmium 2+from aqueous solutions.

Predicting the removal rate of pollutants in wastewater treatment is important for understanding the mechanism and pathway of adsorption reactions.Describing the adsorption kinetics of iron on divalent cadmium using quasi first and quasi second order kinetic models 3O4@SiO2 @KCC-1 adsorbent.

In the removal of pollutants, it is necessary to desorb divalent cadmium ions and reuse adsorbents for other continuous cycles to develop cost-effective technologies.

To do this, add 1.0 g of adsorbent to 100 mL of 1 mol nitric acid solution and stir for 30 minutes.Then, filter the solution and determine the residual cadmium concentration in the solution.

The applicability of the model tested in this project has been targeted at real samples. The experiment was conducted using drinking water and industrial wastewater samples with different amounts of divalent cadmium added, and the treatment was carried out according to general procedures under optimized conditions.The results indicate that with the increase of cadmium concentration, the removal efficiency value decreases.

The optimal process conditions were determined through experimental design and statistical analysis.Under optimized process conditions, magnetic fibrous silica mesoporous materials can achieve efficient and selective removal of divalent cadmium ions. throughThrough surface adsorption and other mechanisms, the material also exhibits good reusability and stability.

In fact, each adsorbent has a limited number of active adsorption sites for the adsorption of pollutants. At higher concentrations, the removal efficiency decreases because these active site on the adsorbent surface are saturated with pollutants.The results showed an ideal removal rate, confirming the excellent performance of the adsorbent proposed for the actual sample.

In my opinion

In this study, Fe3O4@SiO2 @KCC-1 serves as an effective adsorbent for the removal of cadmium ions,X

This study optimized the magnetic fibrous silica mesoporous system using response surface methodology,Used for selective and efficient removal of divalent cadmium ions.

The optimized system exhibits excellent removal performance and has potential application prospects.Further research can explore the application of this system in the removal of other heavy metal ions and conduct in-depth research on its adsorption mechanism.

Under the response surface method, the effect of different parameters on the removal rate of divalent cadmium was studied using a charge coupled device.The Langmuir and Freundlich isotherm models were used to study equilibrium data and fitted well with the Freundlich model.

The maximum adsorption capacity of iron on cadmium was studied using the Langmuir model 3O4@SiO2 @KCC-1 is 59.17 milligrams per liter, with a contact time of 60 minutes at pH 6 and an adsorbent dose of 2g/L.

The high adsorption capacity of this adsorbent in cadmium removal is due to its porous structure and the presence of many pores. The dynamic model was studied and well fitted using a pseudo second-order model.The complex mechanism of adsorbent adsorption into adsorbent is the pathway through which diffusion occurs.

These pathways can be considered parallel pathways through which matter passes.When a material can penetrate through several parallel paths, the path with a higher diffusion rate always has a significant impact on the transfer process. The diffusion mechanism is usually based on two models, "pore diffusion" and "surface or solid diffusion" models, or a combination of these two models.

In the pore diffusion model, the pore diffusion coefficient and in the solid diffusion model, the solid surface diffusion coefficient control the adsorption rate, while in the mixed model, the effective diffusion coefficient is a function of both.Comparison of Fe 3O4@SiO2 @KCC-1 and other adsorbents reported in literature have shown ideal adsorbent adsorption capacity.

The results indicate that, Fe3O4@SiO2 @KCC-1 can serve as a simple adsorbent for removing divalent cadmium from aqueous solutions.

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