Investigation of the adsorption and immobilization mechanism of Fe(Ⅱ)-modified montmorillonite on soil mercury
In order to clarify the adsorption,desorption characteristics and the potential mechanism of Fe-MMT on soil mercury ions(Hg2+),Fe(Ⅱ)-based montmorillonite(Fe-MMT)was synthesized by modifying sodium-based montmorillonite(Na-MMT)with FeSO4·7H2O to investigate the adsorption and desorption characteristics,adsorption kinetics and isothermal adsorption modeling of soil Hg2+with Fe-MMT under the conditions of different pH values,adsorbent dosages,initial Hg2+concentrations,and reaction time.It was found that Fe-MMT removed up to 76.8％of soil Hg2+at pH=5,adsorbent dosage of 0.5 g,initial Hg2+concentration of 170 mg/L and reaction time of 0.5 h.The adsorption process of Fe-MMT on Hg2+was consistent with the Langmuir isothermal adsorption model,and the pseudo-second-order kinetic model could fit the adsorption kinetic behavior well,indicating that the ad-sorption process was mainly monomolecular layer adsorption and mainly occurs on the homogeneous re-action sites on the adsorbent surface.Combined with microstructural characterization,it was found that the adsorption of soil Hg2+by Fe-MMT was mainly induced by the complexation of-S2-,-SH and-OH with Hg2+,and the in situ co-precipitation complexation of Fe2+with Hg2+.The desorption rate of Fe-MMT in the water-soil mixed system was 9.7％,indicating that Fe-MMT had an excellent immobiliza-tion effect on soil Hg2+.It can be seen that Fe MMT has the potential to remediate soil contaminated with Hg.
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