Smart Water?based Ferrofluid: Preparation And Application In Wastewater Treatment

Water-based ferrofluids as stable magnetic nanoparticles aqueous suspensions have shown wide application prospects in many fields such as biomedicine,catalytic chemistry and wastewater treatment.However,current water-based ferrofluids preparation technology researches mainly focus on how to obtain magnetic nanoparticles highly stably dispersed in aqueous solutions,but many practical applications require magnetic nanoparticles to be not only highly stable but also recyclable.Especially in wastewater treatment,the existing adsorption materials have poor stability,tend to settle and rely on shakers to play their roles.Magnetic nanoparticles in water-based ferrofluids have highly stable dispersion,which is hopeful to solve the above problems,but if they can not be easily recovered,they would cause secondary pollution in turn.Therefore,the preparation of smart water-based ferrofluid with adjustable stability is the key and challenge to improve the preparation level of water-based ferrofluid and achieve the deep wastewater treatment application.In addition,in order to achieve high wastewater treatment efficiency,water-based ferrofluids also need to possess superior adsorption function,which further increases the difficulty of water-based ferrofluids preparation.Based on the above problems,this paper systematically explores the preparation method,performance characterization and wastewater treatment application of water-based ferrofluid with adjustable stability.In terms of ferrofluid preparation and performance characterization,polyethylenimine is used to modify Fe₃O₄ magnetic nanoparticles,which are then improved by acidification treatment and ultracentrifugation-based washing,and the products as well as intermediate products are systematically characterized.On this basis,the synthetic ferrofluid and intermediate products are systematically characterized.The results show that the prepared ferrofluid possesses superparamagnetism,high saturation magnetization as well as strong colloidal stability,and the magnetic nanoparticles contained in the ferrofluid have small aggregation size,strong electropositivity and high saturation magnetization.At the same time,by comparing with the characterization results of intermediate products,it is further proved that the acidification treatment and ultracentrifugation-based washing greatly activate the positive charge and reduce the aggregation size of polyethylenimine modified magnetic nanoparticles,which is the key to this successful synthesis of this new type of ferrofluid.In the aspect of ferrofluid application research,this paper takes anionic Ponceau S dye as the experimental object,and systematically explores the adsorption and recovery performance of the prepared water-based ferrofluid in wastewater treatment.It is found that the ferrofluid can rapidly and uniformly disperse after mixing with dye solution to effectively play its adsorption effect.The results also show that the stability of magnetic nanoparticles in the solution decreased significantly after absorbing Ponceau S dye,which can be easily separated from the solution by applying magnetic field,effectively preventing secondary pollution.By analyzing the aggregation of magnetic nanoparticles before and after absorbing Ponceau S dye,this paper finds that the stable state transition of this ferrofluid could be attributed to the dispersion transition of magnetic nanoparticle.At the same time,the adsorption dynamic process and isotherm model of this ferrofluid for Ponceau S dye are also studied,and the adsorption mechanism of the prepared ferrofluid is further explored through fitting analysis.According to the adsorption kinetics experimental data,the ferrofluid adsorption process can reach equilibrium within a very short time(<5min).By comparing the correlation coefficients obtained by fitting different models,this paper points out that pseudo-second-order kinetics and Langmuir isotherm models are more suitable to describe the ferrofluid adsorption process,which indicates that the adsorption of ferrofluid to Ponceau S dye is a chemical adsorption on the surface of a uniform single molecule layer.In addition,the Langmuir model fitting also shows that the maximum adsorption capacity of magnetic nanoparticles in this water-based ferrofluid is 140.26 mg/g.