Preparation And Adsorption Properties Of Adsorbent Based On Iron Tailings For Pb(Ⅱ) In Aqueous Solutions

Rapid development of modern mining and industrialization results excessive accumulation of iron tailings and lead pollution in water have gradually become the focus of worldwide attention.In this study,the iron tailings was used as base material to prepare modified iron tailings/corn stalk composites using acid and alkali modification,compounding and vacuum pyrolysis.The optimizes preparation conditions of the adsorbent materials were explored.The materials before and after adsorption of Pb²⁺were characterized by XRF,BET,XRD,FT-IR and SEM.The adsorption process and mechanism for removal of Pb²⁺from water were studied.The main findings of the study are as below:（1）The modified iron tailings were prepared by acid and alkali modification.The optimal preparation conditions is as follows:2 mol/L HNO₃ and NaOH contents are 4mL/g and 10 mL/g,acidification for 2 h,alkalization for 0.5 h,and reaction temperature is 85℃.Under the conditions of pH of 5,Pb²⁺initial concentration of 200 mg/L,adsorbent dosage of 1.0 g/L,temperature of 25℃,and adsorption time of 24 h,the maximum removal efficiency of Pb²⁺was 95.66%and the adsorption amount was 185.63mg/g.The Langmiur isothermal adsorption model showed a better fitting of the adsorption process,and the theoretical maximum adsorption capacity was 260.42 mg/g.Thermodynamics and kinetics indicated that the adsorption reaction was spontaneous and mainly controlled by chemisorption.（2）The modified iron tailings/corn stalk composite was prepared by compounding,vacuum pyrolysis and acid-alkali modification.The optimal preparation conditions is as follows:that the mass ratio of iron tailings to corn stalks at 3:1,the volume and mass ratio of 0.5 mol/L KOH to the mixed raw materials is 5:1,the pyrolysis temperature is 500℃,the pyrolysis time is 1 h,2 mol/L HNO₃ and NaOH contents are 40 mL/g and 50 mL/g,acidification for 3 h,alkalization for 0.5 h,and reaction temperature is 55℃.Under the conditions of pH of 5,Pb²⁺initial concentration of 200 mg/L,adsorbent dosage of 1.0g/L,temperature of 25℃,and adsorption time of 24 h,the maximum removal rate of Pb²⁺was 97.05%and the adsorption amount was 198.98 mg/g.The Langmiur isothermal adsorption model showed a better fitting of the adsorption process,and the theoretical maximum adsorption capacity was 333.33 mg/g.Thermodynamics and kinetics indicated that the adsorption reaction was spontaneous and mainly controlled by chemisorption,and it was also controlled by diffusion during the initial stage of adsorption.（3）The characterization analysis showed that the adsorption mechanism of Pb²⁺in water by the adsorption materials was the reaction between Pb²⁺and CO₃^2-released from the materials,plate-columnar cerussite crystals which were fixed the surface and inside of the materials,and the plate-columnar white lead crystals formed by the reaction were fixed on the surface of the material and in the pores.The desorption regeneration test showed that the first desorption regeneration effect of the modified composite material was better,and the regeneration rate was up to 88.89%.