Preparation Of Halloysite-based Composites And Study On Its Fenton-like Properties

With the accelerating rate of industrial development in China,a large amount of industrial wastewater is produced,so the removal of organic pollutants has been an urgent problem to be solved at present.Among them,adsorption is easy to operate and has a high removal efficiency,which is widely used in wastewater treatment.Natural mineral materials such as halloysite are often used as adsorbents for dye wastewater treatment because of their abundant reserves and low prices.In this paper,the composite materials were modified with halloysite as the raw material and the methylene blue present in the wastewater was selected as the removal target to investigate the performance of halloysite-based composites for the removal of wastewater containing methylene blue.The main findings of this paper are as follows:The adsorption performance of methylene blue was investigated by using halloysite as adsorbent.The effects of the amount of halloysite,solution pH value,initial concentration of methylene blue and reaction temperature on the adsorption process were investigated.The experimental results showed that at a reaction temperature of 30°C,pH value=13,a dosage of1 g·L^-1 of halloysite and an initial concentration of 100 mg·L^-1 of methylene blue,the removal of methylene blue by halloysite was 96.48%.Through the removal experiment of halloysite on methylene blue under different conditions,it can be seen that the removal rate of halloysite on methylene blue increases with the increase of time and stabilizes within 30 minutes,while temperature basically does not affect the removal rate.The adsorption mechanism of halloysite on methylene blue was studied.The adsorption process of halloysite on methylene blue conformed to the Langmuir adsorption model and the pseudo-second-order kinetic model.The magnetic halloysite composites were prepared by co-precipitation method using halloysite as the carrier.The magnetic halloysite composites were characterised using XRD,FTIR,TEM and VSM techniques,the results showed that Fe₃O₄ was successfully compounded on the surface of halloysite,and the sample had good paramagnetic properties,and it was easier to achieve solid-liquid separation under the action of an applied magnetic field.Since the loading of Fe₃O₄ on the surface of halloysite will occupy some of the adsorption sites on the surface of halloysite,resulting in a decrease in the removal of methylene blue,we introduced a Fenton-like reaction to investigate the Fenton-like performance of the magnetic halloysite composite using wastewater containing methylene blue as the object of study.The effects of different magnetic content samples,the addition of magnetic halloysite,H₂O₂ dosage,initial pH value and temperature on the removal of methylene blue by magnetic halloysite composites were investigated.The results showed that the magnetic elite composites had good Fenton-like properties at 30°C,with a sample selected with 33%magnetic content,a sample dosage of 1g·L^-1,a methylene blue concentration of 100 mg·L^-1 and an H₂O₂ dosage of 15 m L.Further increase in the amount of magnetic halloysite composites resulted in higher removal rate of methylene blue and increasing removal rate of methylene blue with increasing solution pH value,indicating that the magnetic samples can be applied to a wide range of wastewater pH values.In addition its good magnetic properties are also beneficial for solid-liquid separation and the reuse of magnetic elite composites in wastewater.In order to further improve the removal rate of methylene blue,Mn O₂ was introduced on the surface of magnetic composite halloysite.Fe₃O₄/HNTs was prepared by co-precipitation method using halloysite as raw material,and Mn O₂ material was introduced in the Fe₃O₄/HNTs composite to prepare Fe₃O₄/Mn O₂/HNTs composite with magnetic and Fenton-like catalytic properties,and at the same time The removal rate of methylene blue was improved.The Fenton-like reaction was then used to remove methylene blue,and the effects of adsorption time,adsorbent type,different Fe₃O₄/Mn O₂ ratios,H₂O₂ dosage,pH value and temperature factors were investigated.The results showed that the removal rate of methylene blue could reach 96.8%when the initial pH value of the solution was adjusted to 7,the concentration of methylene blue was 100 mg·L^-1,the sample dosage was 1 g·L^-1,the ratio of Fe₃O₄ to Mn O₂ was 4:1,the dosage of H₂O₂ was 5 m L,and the degradation time was 120 min.The results showed that the removal of methylene blue by Fe₃O₄/Mn O₂/HNTs composites was more consistent with the pseudo-second-order kinetic model.