Research On The Preparation Of Potassium Feldspar Modified Materials And Its Effect On Adsorption And Stabilization Of Lead And Nickel

In recent years,heavy metal contamination incidents occur frequently.Its degradation in natural environment is difficult and it has a long latency,which poses a serious threat to human health.In this research,carbon hydroxyapatite?CHAP?was used to modify the potassium feldspar?RK?in Hami to obtain adsorbing material?CHAK?.The adsorption properties of CHAK on Pb²⁺or Ni²⁺in water and the bioavailability effect of CHAK on Pb or Ni in contamination soil were investigated.Pot experiments were conducted to verify the stability of CHAK on Pb or Ni in soil.The research contents as follows:1.Preparation and Characterization of the Modified Potassium Feldspar MaterialsPotassium feldspar as raw material was modified by loading carbon hydroxyapatite and the preparation conditions of CHAK were optimized by single factor experiments and response surface analysis experiments.The optimum preparation conditions:the molar ratio of CO₃^2-to PO₄^3-is 0.23,the mass ratio of RK and hydroxyapatite?HAP?is 0.4,the stirring time is 2 h,the stirring temperature is 43.1°C,and the aging time is 24 h.In this condition,the adsorption rate of the CHAK for Ni²⁺is 92.9%,which is basically consistent with the predicted value of response surface model?RSM?of 93.3%,and was nearly 9 times higher than the adsorption rate of the raw materials.The structure and morphology of CHAK and RK were analyzed by BET,FTIR,SEM,XRD and EDS mapping.The results showed that CHAP was successfully loaded on RK surface,and the surface of the obtained CHAK become fluffy and rough.Its specific surface area and total pore volume increased by nearly 60 and 55 times compared with raw material,which was more conducive to remove heavy metal ions than RK.2.CHAK was used to remove heavy metal ions Pb²⁺?Ni²⁺in water.The effects of the CHAK amount,initial solution pH value,adsorption time and temperature,and initial ion concentration on the adsorbability were investigated by static adsorption test,in addition,kinetics and thermodynamic are used to explore the adsorption processes.The results show that the removal rate of Ni²⁺increased with the CHAK addition,while the adsorption capacity of Ni²⁺is decreased.The optimal adsorption effect is obtained at the pH=6.The adsorption equilibrium was obtained with the adsorption time of 10 h.The adsorption ability of CHAK to Ni²⁺increased with the initial concentration of Ni²⁺from 50 to 4000 mg·L^-1,and then it reached stabilized.The saturated adsorption capacity of the CHAK is 44.97 mg·g^-1,which is 7.1 times than that of the RK.The removal capacity of CHAK to Pb²⁺was good in the range of pH 2⁷,the removal rate increased with the CHAK amount,while the adsorption capacity of CHAK to Pb²⁺is decreased.The adsorption process tended to equilibrium after 10 h.With the increase of initial concentration of Pb²⁺from 100 to6000 mg·L^-1,the adsorption capacity of CHAK for Pb²⁺in solution increased to1135.25 mg·g^-1,which is 45.3 times than that of the RK.The pseudo second order kinetic model is well fitted with the adsorption process,and the correlation fitting coefficient can reach 0.999.Freundlich isothermal adsorption model can better describe the adsorption processes of CHAK on Pb²⁺or Ni²⁺,and the adsorption processes are spontaneous,endothermic,entropy increasing process.3.Effects of CHAK addition on the forms distribution of Pb or Ni in soilThough changing the amount of CHAK or RK applied,the transformation of different forms of heavy metals in contaminated soils was analyzed by Tessier method.The soils were contaminated with different concentrations of Pb or Ni.The results showed that the addition of CHAK could significantly improve the quality of soil compared with the RK.With the addition of CHAK,the contents of exchangeable and carbonate-bound heavy metals with high toxicity decreased significantly,and all of them turned to residue state.There was a significant negative correlation between the amount of CHAK and the bioavailability of Pb or Ni in soil?P<0.05?.With the increase of CHAK,the bioactivity of Pb or Ni decreased significantly.CHAK has good potential application value in the remediation of soils contaminated with Pb or Ni seriously,and its passivation effect on Pb is obviously better than that of Ni.4.Effect of CHAK on the absorption performance of Pb or Ni in alfalfaThe pot experiment of alfalfa was applied in Pb or Ni contaminated soil with different mass fractions of CHAK or RK.The results showed that compared with the application of RK,the application of CHAK could significantly reduce the content of Pb or Ni in the above-ground and underground parts of alfalfa,and the amount of CHAK was negatively correlated with the absorption of Pb or Ni in the above-ground and underground parts of alfalfa?P<0.05?,which also verified that the bioavailability of Pb or Ni in contaminated soil decreased with the addition of CHAK.The migration ability of Pb or Ni in Soil-Alfalfa and underground-aboveground of alfalfa decreased with the increase of CHAK addition.