The Research On Preparation And Performance Of Magnetic Hydroxyapatite Nanoparticles Adsorbents

With the rapid development of economy, large discharge of wastewater,accumulation of the heavy metals in soil and water, heavy metal pollution is becomingmore and more serious. Due to the heavy metals can take a serious threat to organismand human health through the food chain and bioaccumulation, how to efficiently dealwith heavy metal pollution has become an attractive topic.Heavy metal pollution comes mainly from the mining industry, metallurgy,machining, surface treatment and heavy industry and so on. There are many ways toromove heavy metal in wastewater. The conventional technologies for the removal ofheavy metal ions from aqueous solution include chemical precipitation,oxidation-reduction, ferrite and ion exchange resins etc. But all the methods above notonly have the drawback of large investment, high cost and complicated operatingmanagement even leading to cause secondary pollution problems, but also can noteffectively achieve the reuse of heavy metals and water. Currently, adsorption iswidely used in practice. With the superiority of wide resource, low cost and greatefficiency, adsorption method attracts the eyes of people all the time.In recent years, the use of inorganic materials and nano-materials as adsorbentshas become a hot research field. Nano-hydroxyapatite （NHAP） as an adsorbentcomposed of inorganic nano-materials has been widely used to remove heavy metalions with its high biocompatibility and adsorption properties. But as adsorbent used todeal with heavy metals, the performance and efficiency of nano-hydroxyapatiteremains much room to improve.In this study, we propose to synthesize magnetic hydroxyapatite nanoparticles（MNHAP） and explore the possibility of using MNHAP as adsorbents for the removalof Cd²⁺and Zn²⁺from aqueous solution. The properties of this magnetic adsorbentwere characterized by scanning electron microscopy （SEM）, energy dispersiveanalysis system of X-ray （EDAX）, X-ray powder diffraction （XRD） analysis, Zetapotential, BET surface area measurements and magnetic analysis. Experiments werecarried out to investigate the influence of different sorption parameters, such ascontact time, initial concentration of metal ions, the dosage of MNHAP, pH value ofthe solutions and competitive adsorption behavior. In addition, desorption of preparedadsorbent in four eluants was also studied. Kinetic data are well fitted by a pseudosecond-order model and the equilibrium data are analyzed by Langmuir model very well with high correlation coefficient. From the Langmuir isotherms, the maximumadsorption capacities of MNHAP adsorbents towards Cd²⁺and Zn²⁺are1.964mmolg^-1and2.151mmol g^-1, respectively. The optimal dosage of adsorbent was0.1g L-1.The adsorption amount increased with increased pH ranging from4to8. In the binarycomponent system, the adsorption maximum of total adsorption was approximatelyconstant, but the MNHAP adsorbents had better affinity for cadmium ion than for zincion. The most efficient eluant used for desorption of metal ions was EDTA with66.2%and67%of Cd²⁺and Zn²⁺released, respectively. The most prominent advantage ofprepared MNHAP adsorbents with paramagnetism and high specific surface area(142.5m²g^-1) was the separation convenience from aqueous solutions.