Microalgae Removal Effect And Mechanism Of Low Concentration Heavy Metals In Water Environment

Living microalgae are often used to remove low concentrations of heavy metal contaminants in water bodies due to their high efficiency and economy.In order to achieve the effective removal of multiple heavy metals in the water environment,and to enhance the microalgae’s ability to enrich the heavy metal polluted water,it’s necessary necessary to study the removal effect and related mechanisms of the complex heavy metals.In this project,Chlorella vulgaris(C.vulgaris)was used as a typical microalgae,and the heavy metals Cu(Ⅱ),Ni(Ⅱ),Cr(Ⅵ)and Zn(Ⅱ),which are common in the water environment,were selected to study the removal effect of C.vulgaris on single heavy metals.And through the cell growth and enzyme system changes to identify the removal mechanism,on the basis of this investigation Cu(Ⅱ)and Cr(Ⅵ),Zn(Ⅱ)and Cr(Ⅵ)composite heavy metals on algal cell growth characteristics and physiological characteristics To reveal the effect and related mechanism of C.vulgaris on the removal of composite heavy metals.The main research results of this topic are as follows:(1)Chlorella on single heavy metals(Cu(II),Ni(II),Cr(VI)and Zn(II))and composite heavy metals(Cu(II)+ Cr(VI),Zn(II)+ Cr(VI))The absorption capacity of each metal exhibits a significant "dose-effect" relationship with each heavy metal.The higher the concentration of heavy metals,the higher the absorption capacity.(2)For single heavy metals,lower concentrations of heavy metals Cu(II)(≤0.1mg/L),Ni(II)(≤0.2mg/L)and Zn(II)(≤1.0-2.0mg/L)By stimulating the activity of SOD and CAT enzymes,and thereby promoting the growth of algal cells,it is conducive to the absorption of more heavy metals in the form of active transportation,but when it exceeds a certain threshold,the degree of cell damage is enhanced,causing changes in cell membrane permeability,In turn,the active transport function is weakened,while passive transport is dominant,and the absorption of heavy metals continues to increase.At this time,the continued enhanced SOD and CAT enzyme activities can not eliminate the cell toxicity.The growth promotion is weakened or even suppressed.When the heavy metal concentration continues When it is increased,the SOD and CAT enzyme activities in the algal cells are inhibited.At this time,the cytotoxicity is further enhanced,which further enhances the growth inhibition effect.Chlorella’s relatively low absorption rate of Cr(Ⅵ)is attributed to the growth inhibition and efflux of Cr(Ⅵ)on Chlorella.(3)Compared with the single heavy metal experiment,the presence of Cu(Ⅱ)or Zn(Ⅱ)promotes the absorption of Cr(Ⅵ),which may be the competitive adsorption of heavy metals on cell surface active groups or polysaccharides the result of.As far as the typical 0.1 Cu+1.0 Cr group is concerned,the SOD and CAT enzyme activities are the lowest year-on-year,and the performance of Chlorella is the best year-on-year.This may be due to a certain synergy between 0.1 Cu+1.0 Cr,which reduces The absorption of Cu(Ⅱ)by algae cells is reduced to reduce the cytotoxicity;in the case of the same typical 0.1 Zn +1.0 Cr composite group,its SOD and CAT enzyme activities are the highest year-on-year,making Chlorella growth status the most Poor,it may be that there is some antagonism between 0.1 Zn +1.0 Cr,which enhances the absorption of Cr(Ⅵ)by algae cells,thereby enhancing the cell toxicity.