The Effect And Mechanism Of Biochar On Iodine And Cadmium In The Presence Of PAHs

In recent years,the problem of soil compound pollution is becoming more and more serious.Heavy metals and PAHs pollution are common soil pollution,and radioactive pollution also has potential risks.The interaction of pollutants increases the difficulty of soil remediation.Biochar,as a common and efficient adsorbent,can effectively regulate the migration and transformation of heavy metals and PAHs in the soil environment,and has the potential to control radioactive pollutants.However,it is still unclear about the micro interface process between and on biochar and the influence of soil environmental factors on the resistance and control of biochar.In this paper,biochar from wheat straw was prepared.The target pollutants of biochar were iodine and cadmium,and naphthalene,phenanthrene and pyrene were the representatives of PAHs.The interaction and mechanism of biochar were studied from the perspective of compound pollution.The inhibition and influence factors of biochar on compound polluted soil were explored.It is of great significance to the practice of biochar in the remediation of compound polluted soil Righteousness.The main conclusions are as follows:?1?The change rule of the physical and chemical properties of biochar with temperature was studied.With the increase of pyrolysis temperature?200 ?-800 ??,the yield of biochar from wheat straw decreased and the ash content increased gradually;the aromaticity increased,the hydrophilicity and polarity weakened,the number of double bonds increased;the aliphatic functional groups of biochar disappeared gradually,the aromatic functional groups increased gradually;the irregular tube bundle structure appeared on the surface of biochar,the number of micropores increased,the specific surface area increased,and the biomass increased Thinning of carbon skeleton and wall frame.?2?The adsorption capacity and mechanism of biochar on iodine and Cd²⁺ were studied.The adsorption of iodine by biochar belongs to chemical adsorption,which may be related to the formation of covalent bond between biochar and iodine.For the equilibrium adsorption capacity,BC400 >BC300 > BC200 > BC600 > BC500 >wheat straw > BC700 > BC800.The adsorption of biochar to Cd²⁺belongs to chemical adsorption.The main mechanism is surface complexation andco-precipitation..For the equilibrium adsorption,BC400> BC200> BC300> BC700>wheat straw> BC600> BC800.?3?Biochar can effectively enhance the fixation effect of soil on iodine and Cd²⁺.With the increase of biochar addition ratio,the adsorption capacity and removal rate of iodine in soil increased significantly,and Kf of Frendlich model was positively correlated with the carbon addition ratio.Biochar inhibited the desorption of Cd²⁺ and enhanced the adsorption of Cd²⁺ on soil.With the increase of carbon ratio,the adsorption capacity and removal rate of Cd²⁺on soil increased.?4?PAHs significantly affected the adsorption of iodine by biochar added soil.PAHs can form C-I bond with iodine to promote adsorption,and compete with iodine to inhibit adsorption.Phen and PYR promoted iodine more than inhibition,while naphthalene inhibited iodine more than promotion.PAHs had no significant effect on the adsorption of Cd²⁺ by 1% BC400.