The Synthesis And Modification Of Fluorite-based Y-type Zeolite For The Passivation Of Heavy Metal Contaminated Soil

In this experiment,the coal gangue in Xiayugou coal mine area of Hancheng,Shaanxi Province was used as experimental raw material,Zeolite Y were synthesized by"activated by high temperature-alkali fusion-alkali dissolution-aging-crystallize"hydrothermal system from coal gangue via the condition of each stage and the control of SiO2/Al2O3.The samples were characterized by SEM,XRD,FTIR and BET,and the synthesized products were applied to the adsorption of ammonia nitrogen wastewater.The synthesized zeolite was modified with ferrous sulfate to obtain a modified product Fe-NaY zeolite.The modified Fe-NaY zeolite was characterized by SEM,FTIR,XPS and BET,and compared with the original NaY zeolite.(NO3)2,Pb(NO3)2 and NiSO4·6H2O were used to simulate the soil quality of soil quality(GB15618-1995)in the soil of the northern part of the main building of Shaanxi Normal University with CrCl3·6H2O,CdCl2·2.5H2O,Cu(NO3)2The heavy metal elements contaminated in the soil samples exceeded the environmental quality standard and experienced eight months of aging time.The NaY zeolite with different mass ratio and Fe-NaY zeolite were added to the complex heavy metal contaminated soil for three months of chemical passivation repair.The NaY zeolite and Fe-NaY zeolite were characterized by XPS and FTIR,and the results were as follows:(1)The results showed that the leaching concentration and stability of the heavy metal were stabilized and the morphology of the heavy metal was stabilized.(Na2CO3/gangue)is equal to 1.0,alkali concentration of NaOH is 2 mol/L,aging at 60 ? for 12 h,the crystallization temperature is 850 ?,the alkali melting temperature is 850 ?,The crystallization temperature is 105 ?,the crystallization time is 6 h,the ratio of silica to alumina is 6?8,and the Y type zeolite is the highest crystallinity,up to 93%.(2)In the process of alkali melting,under the condition of high alkalinity(the ratio of the quality of coal gangue and sodium carbonate is greater than 1.0),besides the production of the target product,the formation of sodium stone,under the condition of the low alkalinity condition(coal gangue and sodium carbonate quality ratio less than 1.0),will residual not decomposed nepheline.(3)Coal gangue and sodium carbonate at the temperature of 850 ? generated sodium silicate and sodium aluminum silicate high yield and less energy consumption.(4)The yield of the target zeolite can be greatly improved by adding the seeding agent.When the addition of 2%seed crystal is the highest yield,the yield is 90.1%.With the increase of the silica/alumina ratio,the yield decreases.(5)NaY zeolite has strong chemical adsorption capacity,and the removal rate of ammonia nitrogen wastewater can reach 88.2%in 40 min.(6)FeSO4 modified by ferrous sulfate,due to the interaction of NaY zeolite with Fe2+,the formation of strong Fe-O bond,resulting in NaY zeolite structure shrinkage,crystal volume decreased,while the NaY zeolite surface Forming a porous sheet structure.(7)After modification,the specific surface area of NaY zeolite is decreased and the pore size is increased,and the pore size distribution after modification is more uniform than that before modification.(8)After the treatment of single heavy metal chromium Cr contaminated soil with NaY zeolite and Fe-NaY zeolite as stabilizer With different proportions of NaY zeolite,the leaching concentration of single heavy metal Cr has different degrees of decrease.The leaching concentration of chromium in soil treated with Fe-NaY zeolite was lower when the same ratio of 10%was added to NaY zeolite and Fe-NaY zeolite.(9)After the treatment of single heavy metal chromium Cr contaminated soil with NaY zeolite and Fe-NaY zeolite as stabilizer,the weak acid reduction state of single heavy metal chromium Cr in polluted soil was significantly reduced,and the oxidation state was significantly improved,The content of residual residue decreased slightly,and the percentages of reduced species were not changed.When the Fe-NaY zeolite is used as the stabilizer,the content of the weak acid extractable is less than that of the NaY zeolite as the stabilizer,and the content of the oxidizable state is also increased,and the other two Morphological effect is basically the same.(10)In the compound heavy metal contaminated soil,NaY zeolite had the highest stabilization rate of lead Pb,followed by Ni and Cu,and Cu was the lowest.Fe-NaY zeolite has the same effect on the stabilization of heavy metals Pb,Cd,Cu,Ni and Ni in the soil with different proportions of NaY zeolite,But the adsorption effect of lead Pb is not very different.(11)In the soil contaminated with heavy metals,after the treatment of zeolite passivation,the environmental migration ability of heavy metals in the morphology of the weak acid can extract the state and the content of the reduced state can have varying degrees of reduction,while the more stable oxidation state and residue state content has varying degrees of enhancement.