Adsorption Characteristics Of Pb(Ⅱ) In Aqeous Solution By Na Oh Modified And Immobilized Auricularia Auricular Spent Substrate

With the rapid development of industries such as mining and foundry,heavy metal lead pollution has become increasingly serious,causing environmental and human health problems.The treatment of lead-containing waste water is a major problem for industrial waste water treatment in recent years.The method of using agricultural solid waste to treat heavy metal sewage is more and more widely used to purify Pb(Ⅱ)-containing wastewater.In this study,spent substrate from Auricularia Auricular were used as experimental materials and chemically modified and immobilized with sodium hydroxide and sodium alginate.Scanning electron microscopy-X-ray spectrometer(SEM-EDX),Fourier Transform Infrared Spectroscopy(FTIR)and X-Ray Diffraction(XRD)analysis of characteristics of Auricularia Auricular Spent Substrate before and after modification.Determination of adsorption conditions and adsorption mechanism of Pb(Ⅱ)on modified Auricularia Auricular Spent Substrate by batch adsorption test.Using a fixed bed test to analyze the dynamic adsorption of Pb(Ⅱ)by Auricularia Auricular Spent Substrate adsorbents.The breakthrough curve was fitted by a mathematical model to reveal the kinetic adsorption of Pb(Ⅱ)by Auricularia Auricular Spent Substrate.In this study,Auricularia Auricular Spent Substrate showed good adsorption performance.The main results of this study are as follows:(1)The sodium hydroxide modification effectively increased the adsorption capacity of Auricularia Auricular Spent Substrate to Pb(Ⅱ)by125%.The SEM test found that the modification could remove surface impurities and contribute to adsorption.FTIR analysis showed that hydroxyl,carboxyl,amide and amino groups migrated after modification and oxygen functional groups and nitrogen-containing functional groups could form complexes with Pb(Ⅱ).XRD analysis showed that the alkaline crystals on the surface of the Auricularia Auricular Spent Substrate increased after the modification and the influence of the solution H+ was smaller,which favored the adsorption of Pb(Ⅱ)by the Auricularia Auricular Spent Substrate.(2)The results of batch adsorption tests showed that the optimal conditions for the adsorption of Pb(Ⅱ)by modified Auricularia Auricular Spent Substrate were pH 5,the initial concentration of Pb(Ⅱ)was50 mg/L,the dosage of adsorbent was1g/L,the adsorption time was180 min.the temperature is 303 Kand the adsorption capacity can reach 36.35 mg/g at this time.The pH value of the solution had the most significant effect on the adsorption.Under low pH conditions,the surface of the adsorbent was protonated and it was not easy to adsorb Pb(Ⅱ).With the increase of Pb(Ⅱ)concentration(20-100 mg/L),the adsorption amount gradually increased.The process of adsorption of Pb(Ⅱ)by Auricularia Auricular Spent Substrate mainly includes rapid adsorption process within the first 20 minutes and slow adsorption process after 20 minutes.Temperature has little effect on adsorption.(3)The Langmuir and Temkin isothermal model fitted the test results better,indicating that the binding energy on the surface of the Auricularia Auricular Spent Substrate was evenly distributed and the adsorption of Pb(Ⅱ)was monolayer adsorption.The maximum adsorption amount of Auricularia Auricular Spent Substrate was 49.53 mg/g,calculated by the Langmuir model,higher than many other types of agricultural waste absorbents.Pseudo-second-order kinetics models fitted to the test data showed good fitting results indicating the presence of chemisorption in the adsorption process and the maximum adsorption amount of 36.40 mg/g are very close to those obtained by the experiment.(4)The fixed-bed test showed that as the influx of Pb(Ⅱ)increased,the breakthrough time and the exhaustion time became shorter and the adsorption amount increased.Inflow Pb(Ⅱ)concentration is too high,will result in poor treatment.When Pb(Ⅱ)concentration is low,mass transfer resistance becomes larger,and the utilization rate of adsorbent decreases.As the flow rate increases,the breakthrough time and the exhaustion time decrease,and the amount of adsorption decreases.However,the rate of inflow of the Pb(Ⅱ)solution decreases,the breakthrough time becomes longer,and the economic cost increases.As the height of the fixed-bed increases,the breakthrough time and theexhaustion time become longer and the amount of adsorption increases.The Thomas model has a better effect on the brakthrough curve fitting,indicating that the fixed bed adsorption process is not limited by external and internal diffusion.