Adsorption/Enrichment Mechanism Of U(Ⅵ) And Associated Heavy Metals By Elodea Nuttallii L.

In this paper,the aquatic enrichment plants selection were the key treatment technologies of biological purification treatment for uranium contaminated wastewater,via Hydroponics experiment,to study under uranium and associate heavy metals stress,for Elodea nuttallii L.,Eichhornia crassipes L.,Pistia stratiotes L.to select best combination plants and better enrichment ability,and,to prepare E.nuttallii biochar,to analysis under uranium and heavy meatal single contaminated treatment,E.nuttallii’s physiological/biochemical indexes and photosynthetic performance of change regulation.And under uranium single contaminated E.nuttallii and E.nuttallii biochar for U（Ⅵ）adsorption and enrichment mechanism,to provide some reference for its application in ecological treatment of radioactive contaminated water.The studies’results are as follows:（1）The adsorption and enrichment capacity of E.nuttallii increased with the initial U（Ⅵ）concentrations raised.At 10 mg/L U（Ⅵ）concentrations treatment,bioconcentraion factors（BCF）reached maximum of 0.74,at 25 mg/L U（Ⅵ）concentration treatment,adsorption and enrichment capacity reached maximum of 3.92 mg/g.Through regeneration adsorption and enrichment experiment,the regeneration adsorption and enrichment rate reached maximum of 55.0%.At 30 mg/L U（Ⅵ）concentration,peroxidase（POD）and catalase（CAT）activity were increased 202.4%and 291.6%in comparison with control group,Chlorophyll a（C_a）and Chlorophyll b（C_b）were decreased 27.7%and26.7%in comparison with control group,optimal/maximal PSⅡ efficiency（F_v/F_m）and photosynthetic performance index(PI_abs)were decreased 47.7%and 83.8%in comparison with control group,net photosynthesis rate（P_n）and stomatal conductance（G_a）and intercellular CO₂ concentration（C_i）were decreased 82.1%and 20.5%and 6.4%in comparison with control group.（2）Under different initial Mn（Ⅱ）and Pb（Ⅱ）and Ni（Ⅱ）concentration,the activities of antioxidant enzymes of E.nuttallii to appear consistant tendency,which increased first and then decreased,besides Mn（Ⅱ）treatment group,SOD reached maximum at 20 mg/L,in comparison with control group were increased 40.7%and 12.5%.At 30 mg/L Mn（Ⅱ）treatment,SOD reached maximum in comparison with control group was increased 71.3%,at 20 mg/L heavy metal concentration,POD reached maximum in comparison with control group were increased 23.1%and46.2%and 21.2%,CAT reached maximum in comparison with control group were increased 22.3%and 23.3%and 15.5%.At 30 mg/L heavy metal concentration,F_v/F_m fell drastically in comparison with control group were decreased 1.8%and 5.3%and 11.4%.At 30 mg/L Mn（Ⅱ）treatment,C_a and C_b and C_t in comparison with control group were increased 34.0%and 16.1%and 20.0%.In this experiment condition,Mn（Ⅱ）had a less influence on E.nuttallii,Ni（Ⅱ）had a greater influence on E.nuttallii.（3）Under different initial U（Ⅵ）and Mn（Ⅱ）and Pb（Ⅱ）and Ni（Ⅱ）concentration treatment,the activities of antioxidant enzymes of combination plants（E.crassipes and E.nuttallii or P.stratiotes and E.nuttallii）to appear increased first and then decread tendency.The combination plants（E.crassipes and E.nuttallii）presented a better stress resistance,at 20 mg/L U treatment,the activities of antioxidant enzymes of combination plants were optimum,SOD in comparison with control group were increased 219.2%and 53.2%,POD in comparison with control group were increased 40.5%and 36.9%,CAT in comparison with control group were increased 182.4%and 211.8%,F_v/F_m and PI_absbs in comparison with control group were decreased 2.1%and 19.1%of E.crassipes.F_v/F_m and PI_abs in comparison with control group were decreased 10.3%and 19.6%of E.nuttallii.At 20 mg/L Mn（Ⅱ）concentration,SOD in comparison with control group were increased324.8%and 206.3%,POD in comparison with control group were increased 128.2%and 120.6%,CAT in comparison with control group were increased 170.2%and 147.7%,F_v/F_m and PI_abs in comparison with control group were decreased 6.1%and 9.1%of E.crassipes.F_v/F_m and PI_abs in comparison with control group were decreased 9.1%and 13.1%of E.nuttallii.At 20 mg/L Pb（Ⅱ）concentration,SOD in comparison with control group were increased 51.4%and 208.7%,POD in comparison with control group were increased 40.5%and 36.9%,CAT in comparison with control group were increased 173.4%and 171.1%.F_v/F_m and PI_absbs in comparison with control group were decreased 16.6%and 16.1%of E.crassipes.F_v/F_m and PI_abs in comparison with control group were decreased 11.8%and 14.1%of E.nuttallii.At 20 mg/L Ni concentration,SOD were more than that control group 280.8%and 203.6%,POD in comparison with control group were 104.7%and 66.6%,CAT were more than that control group 115.0%and 135.9%.F_v/F_m and PI_abs in comparison with control group were decreased 24.8%and 33.2%of E.crassipes.F_v/F_m and PI_abs in comparison with control group were decreased 36.8%and 18.8%of E.nuttallii.（4）Through the E.nuttallii biochar of preparation,to make a systematic study on the U（Ⅵ）adsorption performance,the results showed that:under the experiment condition（pH 3,temperature 303.15K,120 mg/L initial U（Ⅵ）concentration,dose 0.01 g）,the saturated adsorption capacity of U（Ⅵ）was 303.58 mg/g.The external factors（different initial U（Ⅵ）concentrations,dose,pH,temperature）e ffected on the U（Ⅵ）adsorption capacity of E.nuttallii biochar were investigated.The results showed that:with the increased of initial U（Ⅵ）concentration,the adsorption capacity of U（Ⅵ）was increased and removal rate of U（Ⅵ）was decreased（88.1%）.With the increased of pH value,the adsorption capacity of U（Ⅵ）was decreased,at pH 3,the adsorptioncapacityreachedmaximum176.43mg/g.The characterization of E.nuttallii biochar before and after adsorption（SEM,EDX,FT-IR）that the surface of the biochar was no obvious change,it has a better adsorption stability.The content of U（Ⅵ）was increased 2.0%after adsorption.It was mainly chemisorption progress by containing O multifunctional groups which took part in the adsorption U（Ⅵ）of E.nuttallii biochar.