The Research Of Heavy Metals Accumulation In Several Plants And The Post-processing Resource Recycling

At the farmland with heavy metal pollution in guiyang county guanxi village of hunan chenzhou,select three kinds of oil crops: rape、peanut、sunflower and tobacco as the research object,Study the absorption accumulation ability on soil heavy metalsof rape、peanut sunflower and tobacco;then compare the removal efficieny of heavy metals by thee kinds of extractants(potassium tartrate,potassium citrate,hydrochloric acid)for rapeseeds and peanut meal after the oil extraction and thee kinds of extractants(hydrochloric acid,nitric acid,sulfuric acid);Finally selected tobacco in several kinds of plant straw stalks as a representative for the recycling of the straw making biochar and the liquid potassium fertilizer research.The results of the research are as follows:(1)Rape and peanut have the capability of enrichment heavy metals in pollution farmland。Heavy metals mainly concentrated in the root、stem and leaf,the Cd concentration in peanut of the root、stem and leaf is greater than the rape,respectively 13.09 mg/kg,10.38 mg/kg and 12.78mg/kg,BCF is 9.09,9.09 and 7.21;The sunflower root is the highest accumulate part of heavy metal,the concentration of Pb、Zn are respectively 208.7 mg/kg、568.9 mg/kg,BCF is 4.54 and2.34,the Cd concentration in the root、stem、leaf、flower、fruit are just 14.48 mg/kg、3.67 mg/kg、11.28 mg/kg、6.25 mg/kg、6.51 mg/kg,but the BCF reached 10.06、2.55、7.83、4.34 and 4.53,and it is the poor enrichment ability on Cu。Then the enrichment ability of soil heavy metal by tobacco is showed:Cd>Zn>Pb>Cu,and the enrichment ability of Cd in every part is showed:bottom leaves>middle leaves>upper leaves>stem>root,the BCF of Cd in bottom leaves、middle leaves、upper leaves are 11.24、12.82、16.37 while the BCF of Cu are Below 1。(2)The capacity of extract heavy metals from peanut meal : hydrochloric acid>potassium tartrate>potassium citrate.with the concentration and extraction times increasing,removal rate of Pb,Zn,Cu and Cd increased,the trend of heavy metals decreased became gently in 12h;The Pb removal rate of 30 m M potassium tartrate、30m M potassium citrate and 1% hydrochloric acid are71.9%、34.2% and 59.3%,and the removal rate of Cd is higher than Cu、Zn。After the 3rd of30 m M potassium tartrate and 2nd of 1% hydrochloric acid extracted,the Cd concentration is0.36mg/kg and 0.21mg/kg,It is below the limits for feeds in China。While the extraction of nutrients by potassium tartrate and potassium citrate are lower than hydrochloric acid,then there have little influence on crude protein in extraction process by those three extractants 。(3)It is the experiment of heavy metal leached in rapeseed meal shows:The removal efficiency for heavy metals in rapeseed meal increased with the extracting time increased;and the efficiency would be significant if extracted several times and the concentration ofhydrochloric acidimproved.The removal efficiency of Cd is the best,followed by Zn,Cu,Pb.The Pb and Cd in rapeseed meal could below the limits for feeds after the first leaching with 1% hydrochloric acid and 0.25% and0.5% hydrochloric acid extraction for twice.(4)The removal rate for tobacco leaves would be enhanced with the increasing of extraction time of by the 1% hydrochloric acid,nitric acid and sulfuric acid.The removal ability of three kinds of extraction agents for heavy metal is Zn > Cd > Pb > Cu,in 12 h of leaching time,the remaining Pb concentration is 4.32mg/kg and 4.42mg/kg after by hydrochloric acid and sulfuric acid respectively which both are below the limits for feedsof Pb.The Cd removal rate can be stable when extracted about 12 h as 88.97%,83.05% and69.01% while the content is 2.01mg/kg,3.09mg/kg,5.65mg/kgrespectively for hydrochloric acid,nitric acid and sulfuric acid.There are only hydrochloric acid after 3rd extracted have make the tobacco leaves meet the limits for feedsof three 1% acid,so comparing with nitric acid and sulfuric acid,hydrochloric acid is the best extraction agent for remove heavy metal in tobacco leaves。It is after the 2nd extracted of 0.5%、1%、2% and the 3rd of 0.25%、0.5%、1%、2% hydrochloric acid,both Cd and Pb in tobacco leaves have meet the limits for feeds;Comprehensive economic costs,the best extraction conditions is the 2nd extract by 0.5% hydrochloric acid;and Ca,Mg,K,P would be extracted greater while Fe,Al are little after extracted twice with 0.5% hydrochloric acid which can extracts crude protein insignificantly but can completely removal the nicotine.(5)The charcoalproductivitydecreases with the increasing of temperature for rape straw 、sunflower straw and tobacco straw,there are little volatilization of heavy metal in 300℃,most of heavy metal in the biochar,the Cd is easily volatilize compare with Pb、Zn、Cu,volatilize completely at 500℃。Then we make extraction for 300℃ biochar in different p H conditions,the results showed that when p H was 1,90% Cd is separate out,Adjust p H to alkaline after filtered,the heavy metal have generate precipitation,and the amount of K increased with the rise of p H。filtered again,remaining low heavy metal in the solution...