Study On The Removal Of Manganese Ions From Aqueous Solution By Zeolite Phase Adsorption Materials Synthesized From Illite

With the rapid development of economy and industry,the discharge of wastewater containing heavy metal manganese is increasing,which poses a serious threat to the ecological environment and human health.Illite is rich in reserves,cheap and easy to obtain,environment-friendly,and has great application value.However,the weak adsorption capacity of illite for heavy metals limits its wide application as an adsorbent for environmental pollutants.The physical and chemical properties of illite can be regulated by means of roasting activation and hydrothermal method,which not only improves the additional value of illite,but also provides a cheap and efficient adsorbent for the removal of heavy metals from wastewater.In this paper,zeolite phase adsorption materials?ZAM?were first prepared by calcined activation?CA?with illite?I?,calcium carbonate and calcium sulfate and then by hydrothermal reaction with those activator as raw materials.The effects of the molar ratio of illite to CaCO₃/CaSO₄,activation temperature and activation time on the activation of illite were investigated.The optimum conditions for the activation of illite were determined as follows:the molar ratio of illite,CaCO₃ and CaSO₄ was 1:15.6:1.2,activation temperature was 950 ^oC and activation time was 1 h.Under the above conditions,illite was almost completely activated.Then,the effects of Si/Al ratio,hydrothermal temperature,hydrothermal time and solid-liquid ratio on the preparation of ZAM were investigated.The optimum conditions for the preparation of zeolite phase adsorption materials were determined as follows:Si/Al ratio was 2,hydrothermal time was 4 hours,hydrothermal temperature was 150 ^oC,and solid-liquid ratio was 1:10.X-ray diffraction?XRD?,scanning electron microscopy?SEM?,Fourier infrared spectroscopy?FTIR?and N₂ adsorption desorption were used to characterize and analyzed the samples.XRD patterns showed that the main mineral phases of the as-prepared adsorbents were typical environmental remediation minerals such as thomsonite,gismondite,phillipsite,gehlenite,hydrated calcium silicate.SEM images showed that the ZAM had developed pore structure and presented rod-shaped and network aggregation.N₂ adsorption desorption results showed that zeolite phase adsorption materials has a larger specific surface area which was 24.1 m²/g.Taking heavy metal ion Mn²⁺as the target pollutant,the effects of initial p H,adsorbent dosage,contact time,coexisting cations and other factors on the adsorption performance of ZAM for Mn²⁺were investigated,and the thermodynamic and kinetic simulation were also carried out.The results showed that the adsorption capacity of ZAM for Mn²⁺increased with the increase of initial p H,dosage and reaction time.At 25 ^oC,p H 5,0.6 g/L and 180 min,the maximum removal of Mn²⁺by ZAM was 44.26 mg/g.The existence of coexisting cations can inhibit the adsorption reaction to a certain extent and increase with the increase of cation concentration.The degree of inhibition was:Ca²⁺>Mg²⁺>Na⁺>K⁺.The study of adsorption kinetics showed that the adsorption of Mn²⁺by ZAM followed the second-order kinetics model,and the rate limiting reaction step was chemical adsorption process;the adsorption thermodynamics process was well described by Freundlich isothermal model;it was entropy driven endothermic reaction,and high temperature was favorable for adsorption.The regeneration experiment showed that the adsorption capacity of ZAM was 32.02 mg/g,which was 72%of the adsorption capacity of the first adsorption,and it had good reusability.The results of XRD?SEM and XPS showed that the main removal mechanism of Mn²⁺in aqueous solution was the ion exchange between Ca²⁺and Mn²⁺,followed by adsorption and oxidation precipitation.