Preparation Of Biochar From Waste Pomelo And Its Effect On The Quality Of Pakchoi In Thallium Contaminated Soil

With the advancement of industrialization and natural cycles,such as dry and wet atmospheric deposition,thallium is released into the soil along with the production process and gradually becomes a"time bomb"of the future environment.In this study,biochar was prepared from waste pomelo and used for the remediation of soil contaminated thallium.The mechanism of the biochar in the remediation of thallium pollution and the effect of the quality of pakchoi in soil polluted by thallium were discussed.The main conclusions from the study are as follow.?1?Pyrolysis temperature and pyrolysis time affect the adsorption performance of biochar.PPB700-3 and WPB700-3 have the best adsorption performance because they have well-developed pore structure and rich functional groups to provide sites for Tl⁺adsorption.Furthermore,Langmuir isothermal adsorption model can better fit the adsorption behavior of thallium onto PPB700-3 and WPB700-3,and the subsequent maximum adsorption capacity was4283.9?g·g^-1 and 5286.0?g·g^-1,respectively.In addition,the pseudo-second-order kinetic model could well fit the kinetic behavior of thallium adsorption onto PPB700-3 and WPB700-3,indicating that the process is accompanied by chemical adsorption.?2?In order to increase other soil economic benefits,the biochar was modified by EDTA-Na₂ and KH₂PO₄.As adsorbents for Tl⁺in wastewater,the removal rate of PPB700-3 was90.87%when the biochar was modified in 0.03 mol/L EDTA-Na₂ for 30 min at 60°C;while WPB700-4 was 81.75%when the biochar was modified in 0.01 mol/L EDTA-Na₂ for 20 min at60°C.Besides,The removal rate of PPB700-3 was 91.02%when the biochar was modified in0.2 mol/L KH₂PO₄ for 30 min at 60°C;while WPB700-4 was 87.53%when the biochar was modified in 0.1 mol/L KH₂PO₄ for 20 min at 60°C.?3?The active thallium of agricultural soil was extracted by CaCl₂,DTPA,HCl and H₂O.According to the capacity of extraction,the arrange ranked from strong to weak were HCl>DTPA>CaCl₂>H₂O.The correlation between bioavailable content and extraction amount was explored,indicating T4?0.1M CaCl₂?was the best method to extract thallium in acid agricultural soil of Southern China and the correlation coefficient was 0.959.In order to evaluate the remediation effect of biochar in soil polluted by thallium,the 15 days batch experiments showed that PPB700-3 and WPB700-3 were the most effective,and the available thallium in soil were decreased 45.86%and 34.24%,respectively.?4?PPB700-3 and WPB700-3 were added into the pot experiment to explore the effect of biochar on the quality of pakchoi in soil polluted by thallium.The leaf length,vitamin C content,soluble sugar content and soluble protein content of pakchoi had significantly increased,while the nitrate content and thallium content had significantly decreased.The result showed that the biochar could effectively improve the quality of vegetable and alleviate the stress of thallium on pakchoi.