Study On Synthesis, Characterization Of Ca-Based Functional Materials And Their Adsorption Of Heavy Metal Ions

Heavy metal wastewater treatment has attracted serious concern in recent years.Various technologies are currently available to treat heavy metal wastewater, such aschemical precipitation, electrochemical treatment, cations-exchange, reverse osmosisand so on. Out of these processes, adsorption is a potentially promising technologydue to its incomparable advantages. Especially, environmental mineral materials asadsorbents have the advantages of low cost, wide sources and high efficiency andhave particularly broad application prospects. Thus, it has great practical significanceto develop new environmental mineral materials.In this thesis, the needle-like surface of ordinary hydroxylapatite （HAP） andmodified hydroxylapatite were synthesized by the method of sol-gel, and hexagonallayer surface of Friedel’s salt （FS） was synthesized by a co-precipitation method.Scanning electron microscope （SEM）, Transmission electron microscope （TEM）,X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FT-IR）, Surfacearea measurement （BET） and X-ray Photoelectron Spectrometer were employed tocharacterize the synthesized mineral materials. Furthermore, the adsorption productswere also characterized with the same characterization methods. The adsorptionmechanisms of the two types of adsorption materials were further discussed.In addition, the adsorptive behavior of HAP-EG and FS to the single-andmulti-element metal in the simulated wastewater was studied under certainconditions．The main factors that might influent the adsorption performance wereinvestigated，such as the dosage of adsorbent, initial metal concentration, pH, reactiontime, temperature and so on. The results demonstrate that the removal efficiency waspositively correlated with the dosage of adsorbent but negatively correlated withinitial metal concentration. Then, the adsorption process in the single-metal solutionwas simulated by adsorption isotherms and kinetic equation. The results indicated thatboth the two types of adsorbents had an outstanding ability for Cd（II） adsorption. The removal efficiency of Cd²⁺could reach up to91.6%with the adsorption capacity of45.79mg/g when the initial concentration of Cd²⁺was10mg/L, dosage of HAP-EGwas0.2g/L, pH was6, the adsorption period was180min and the reactiontemperature was ambient pressure. The basic adsorption mechanism was surfacecomplexation and the adsorption kinetics were well described by second-orderLageren equation. The removal efficiency of Cd²⁺was up to94.34%with theadsorption capacity of301.9mg/g under the same condition as HAP-EG except thepH value7, the dosage of FS0.03g/L and reaction time60min. The adsorptionmechanism was ion exchange and the adsorption kinetics were well described byfirst-order Lageren equation. Adsorption isotherm types were Langmuir-typeadsorption isotherm.Finally, the synthesized adsorbents were used to treat the wastewater containingCd²⁺, Zn²⁺and Cu²⁺ions. The results showed that the two sorbents have a certainselective adsorption. There was a higher adsorption efficiency with HAP-EG for Cu²⁺and the adsorption order was: Cu²⁺> Cd²⁺> Zn²⁺; FS’s adsorption capacity of Zn²⁺wasmore marked and the adsorption order was: Zn²⁺> Cu²⁺> Cd²⁺. Compared with variousmineral adsorbents, FS is a potential cost-effective adsorbent for metal removal inwater treatment, which further provides reference for industrial applications.The paper will provide useful exploration for the development and application oflow-cost, high-efficiency adsorbents used in the treatment of heavy metalwastewater and environment remediation．It has significant social and envrionmentalbenefits...