Study On The Adsorption Of Cu²⁺ And Cd²⁺ In Water By Bacterial Chaff Biochar And The Remediation Effect Of Contaminated Soil

After the Lentinus edodes,Hericium erinaceus and Pleurotus ostreatuswere pyrolyzed to biochar at 500 ℃,the adsorption effect and adsorption mechanism of three kinds of bacterial bran biocharon copper and cadmium in water were studied by water adsorption experiments.The two tested soils were copper and cadmium contaminated soil,which were collected from alkaline brown soil in a sewage irrigation area in Qi County,Jinzhong City,Shanxi Province,and weakly alkaline yellow brown soil paddy soil in Xiangyin County,Yueyang City,Hunan Province.In addition,pot experiments were conducted to study the changes of basic physical and chemical properties,enzyme activity,copper and cadmium forms,and the growth physiological characteristics,stress resistance index,copper and cadmium content of rape planted in soil.The results showed that:（1）When the initial p H of the solution was 2 to 3,the adsorption amount of Cu2 + and Cd2 + in the solution by the three bacterial bran biochar increased sharply.The adsorption processes of Cu2 + and Cd2 + by LEBC,HEBC,and POBC are in accordance with the quasi-second-order kinetic model,the order of the adsorption rates of Cu2 + and Cd2 + is LEBC> HEBC > POBC.The adsorption process of Cu²⁺ by LEBC,HEBC,and POBC at different concentrations conforms to the Langmuir model,and the maximum adsorption amounts are 56.74,11.98,and 77.32 mg·g^-1,respectively;the Cd²⁺ adsorption process was in accordance with the Freundlich model,and the maximum adsorption amounts were 74.26,36.49,and 70.2 mg·g^-1.LEBC can reach a large adsorption capacity in a short period of time and can be used as a high-quality adsorbent for removing Cu²⁺ and Cd²⁺ from water.The results of FTIR and XRD show that the mechanism of adsorption of Cu²⁺ and Cd²⁺ by biochar includes physical adsorption,cation-π interaction,functional group complexation and precipitation.After acidification,the adsorption capacity of three biochar on Cu²⁺ and Cd²⁺decreased significantly,which indicated that the surface precipitation of Cu²⁺ and Cd²⁺ caused by carbonate in biochar played an important role in the adsorption process.（2）All three kinds of bacterial bran biochar can increase the p H,electrical conductivity,organic matter,available nitrogen,and the content of phosphorus and potassium of cinnamon soil and paddy soil,but they have different significance on different indicators of cinnamon soil and paddy soil.Compared with HE and PO,the overall effect of LE on the above indexes in cinnamon soil and paddy soil was more obvious.（3）The effects of the three biochar on the enzyme activities of the two polluted soils were basically the same,the invertase activity in both brown soil and paddy soil was reduced,especially in brown soil;catalase activity and urease activity increased significantly,alkaline phosphatase activity increased slightly.After the application of three kinds of bacterial bran biochar,the contents of acid-extracted Cu and Cd in the two kinds of contaminated soils were reduced to a certain extent,and residual state content was increased,and the effect of this change in paddy soil was more significant;There were no significant changes in the reducible and oxidizable states of Cu and Cd in the two types of contaminated soil;and the process of transforming Cu and Cd in the soil from the acid-extracted state to the residue state was promoted,among them,for this morphological transformation of Cu,PO showed better effects than LE and HE;for Cd,LE showed better effects than HE and PO.The application of bacterial bran biochar can increase the plant height,fresh weight and chlorophyll content of rape grown in two contaminated soils,and promote the growth and development of rape,but the effect in brown soil is not significant.Secondly,after adding biochar,the stress resistance indexes of rape planted in the two contaminated soils changed significantly,and the catalase activity increased significantly;Secondly,after adding biochar,the stress resistance index of rapeseed grown in two contaminated soils changed significantly,catalase activity increased significantly,and the peroxidase activity increased slightly;the activity of superoxide dismutase increased significantly in brown soil rape,but decreased significantly in paddy soil rape;the content of malondialdehyde decreased significantly.Finally,the application of three kinds of bacterial bran biochar can reduce the content of Cu and Cd in the above-ground and underground parts of rape grown in two types of soil,reduce the toxic effects of heavy metals on plants,and promote plant growth and development.Among them,the application of biochar has a more significant effect on the reduction of Cu and Cd content in rape planted in paddy soil.（4）In conclusion,LEBC and POBC can effectively remove Cu and Cd from polluted water,and can be used as adsorbents in Cu and Cd polluted water bodies.The three bacterial bran biocharhave good effects on the changes of soil basic physical and chemical properties,enzyme activity,soil heavy metal form,plant growth,stress resistance and heavy metal content,which can be used as an improver in the soil polluted by Cu and Cd.