The Study Of The Products And Mechanism Of The Adsorption Of Ni²⁺ And The Desorption Of Heavy Metal Ions In Montmorillonite

Montmorillonite has been widely used to curb environmental pollution because of its high cation exchange capacity,large surface area,chemical stability and environmental friendliness.Previous studies mostly focused on the physicochemical factors of the highest adsorption capacity of Montmorillonite and how to increase operation rate.However,the adsorption site had been ignored.Nickel has been widely used in many sectors,such as electroplate,steel and catalyst.Excessive amounts of nickel in the human body causes central circulation and respiratory disorders.Nickel is one of the carcinogenic substance and pathogenic factors of leukemia.Therefore,understanding the mechanism of the adsorption and migration has significantly impact on preserving the ecological environment and maintaining health.The structure changes of the Na-montmorillonite after the adsorption of Ni2+and thermal treatment of 500? were studied.The techniques of testing include X-ray fluorescence(XRF),powder X-ray diffractometry(XRD),electron spin resonance(ESR),Fourier Transform infrared spectroscopy(FTIR)and Expand X-ray absorption fine structure spectrum(EXAFS).The chemical composition of the residue solution had been analyzed by inductively coupled plasma atomic emission spectroscopy(ICP-AES)and the result indicates the Ni2+ in solution reduced significantly and a bit of Na+,Mg2+ had been tested after the adsorption.The d001 increasing from 12.5A to 15.0A means Ni2+ occupied the interlayer region of montmorillonite.The result of EXAFS and ESR suggests Ni2+ replaced Na+ in the montmorillonite by the form of[Ni(H20)6]2+ existing in the interlayer of TOT sheet.After being heated to 500?,the result of XRD shows 'talc' occurred in the product which d001 is between talc and phlogopite and more closed to the talc one.Meanwhile,the result of FTIR indicates the albsorption peak 3708cm-1 of trioctahedral minerals,such as phlogopite and saponite.In general,the Ni2+enters into the octahedral sites of montmorillonite after being heated.Moreover,the difference of the desorption in the acidic and alkaline condition has been discussed in this experiment.The desorption results revealed that the content of heavy metal cations in the acidic solution was remarkably more than that in the alkaline solution.