| With the development of industrial society,human production and life have imposed a great burden on the natural environment,among which heavy metal pollution has caused great harm.With the progress of research,there are numerous methods to treat heavy metal pollution,and adsorption method has been favored by many scholars because of its wide range of materials,simple preparation method and low cost.Among them,the preparation of biochar adsorption materials from agricultural and forestry waste materials can realize the environmental protection concept of turning waste into treasure.This article focuses on the preparation of manganese oxide loaded walnut shell biochar and investigates the adsorption effects and patterns of single-factor adsorption and competitive adsorption of this adsorbent on Cu(II)and Pb(II)simulated wastewater.Scanning electron microscopy(SEM),specific surface area and pore analysis(BET),X-ray diffraction(XRD),and X-ray electron spectroscopy(XPS)were used to characterize the walnut shells before and after modification,so as to analyze the structure,pore space,specific surface area,elemental and functional group characteristics of the walnut shell materials before and after modification;by exploring the adsorbent dosage,initial p H of the solution,adsorption time,solution The optimal adsorption conditions for Cu(II)and Pb(II)were obtained by investigating the effects of adsorbent dosage,initial p H,adsorption time,initial concentration and temperature on the adsorption effect;and the adsorption kinetic model,adsorption isotherm model and adsorption thermodynamic model were used to fit the adsorption process,and the adsorbents after adsorption of Cu(II)and Pb(II)were characterized to analyze the adsorption mechanism;the adsorption of Cu(II)and Pb(II)by MSC(850)was investigated.The adsorption performance of MSC(850)on Cu(II)and Pb(II)in water was determined by reusing and regenerating the adsorbent after the adsorption of Cu(II)and Pb(II),and the competitive adsorption of MSC(850)on Cu(II)and Pb(II)two-component solutions was investigated with reference to the optimal conditions for single-factor adsorption.The main research results are as follows.(1)MSC(850),a walnut shell biochar loaded with Mn O and Mn O2,was successfully prepared from walnut shells by carbonization at 850°C and loaded with Mn O,which is cost effective and environmentally friendly.The characterization results show that MSC(850)has a complex structure,well-developed pores with increased species,increased specific surface area and reduced surface oxygen-containing functional groups compared to walnut shells,but with crystalline loading of Mn O.(2)The optimum conditions for the adsorption of Cu(II)by MSC(850): the maximum adsorption amount of Cu(II)reached 33.12 mg/g and the maximum removal rate reached98.53% when MSC(850)was added at 0.03 g,the initial p H=6.5,and the temperature was298 K with constant temperature shaking at 200 r/min for 90 min;the optimum conditions for the adsorption of Pb(II): MSC(850)at 0.03 g,initial p H=5 and constant shaking at 200r/min for 60 min at 298 K,the maximum adsorption amount of Pb(II)reached 32.35mg/g and the maximum removal rate reached 100%.And the reuse and regeneration recycling of MSC(850)after adsorption of Cu(II)and Pb(II)were good,which indicates that MSC(850)has good adsorption performance for Cu(II)and Pb(II).(3)The adsorption kinetic fitting results showed that the processes of Cu(II)and Pb(II)adsorption by MSC(850)were in accordance with the proposed secondary kinetics,with the participation of chemisorption;the adsorption internal diffusion model fitting results showed that the adsorption of Cu(II)by MSC(850)was proposed as three stages and the adsorption of Pb(II)was proposed as two stages,both of which were dominated by surface adsorption;the adsorption isotherm fitting results showed that the adsorption of Cu(II)and Pb(II)by MSC The adsorption isotherm fitting results show that the adsorption of Cu(II)in MSC(850)is more consistent with the Langmuir isotherm adsorption model,which indicates that the adsorption process is homogeneous monolayer adsorption and preferential adsorption;the adsorption of Pb(II)in MSC(850)is more consistent with the Freundlich isotherm adsorption model,which indicates that the adsorption process is more inclined to non-homogeneous multilayer adsorption and preferential adsorption;the adsorption of Cu(II)and Pb(II)in MSC(850)Cu(II)and Pb(II)in water are more likely to occur;the results of Gibbs function parameters indicate that the adsorption of Cu(II)and Pb(II)by MSC(850)are all exothermic processes that proceed spontaneously.(4)In the competitive adsorption of MSC(850)on Cu(II)and Pb(II)two-component solutions,Pb(II)was more competitive than Cu(II),MSC(850)would preferentially adsorb Pb(II),probably because the ionic radius of Pb(II)is larger than that of Cu(II),which makes Pb(II)more electrostatic and binds to the adsorption site more quickly and easily;however,the two did not inhibit each other,probably because the ionic radius of Pb(II)is larger than that of Cu(II).However,the two did not inhibit each other,probably because the adsorption sites of Cu(II)and Pb(II)on MSC(850)were not exactly the same. |
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