| The pollution of the remaining biomass generated during the soil remediation process is a bottleneck that limits the widespread application of this technology,and the use of the remaining biomass to make biochar is an effective solution.Biochar is a solid product of bio-organic materials(biomass)in an oxygen-free or low-oxygen environment after pyrolyzing.It has the ability to adsorb and remove related pollutants and is also commonly used as a soil amendment.With the excessive discharge of sewage and excessive exploitation of resources in recent years,China is currently facing problems such as eutrophication caused by excessive phosphate content in water bodies and soil damage caused by mining.So how to use biochar to reasonably solve water pollution and soil problems has aroused widespread concern in society.In this study,biochar was prepared from the Broussonetia papyrifera leaves harvested in the manganese mining area and used as an adsorbent for the removal of phosphate in water,and the effects of ionic strength and different kinds of electrolytes on the adsorption process were explored.The adsorption mechanism was explored by combining the analysis of different forms of phosphorus content in biochar after adsorption,this part of the study is of great significance to the removal of phosphate in water and the treatment of water eutrophication.Xiangtan manganese ore soil and nutrient soil were selected.Broussonetia papyrifera biochar without adsorbed phosphate and phosphate adsorbed was added to the two soils as the soil base fertilizer to explore the improvement effect of two biochars on the soil chemical properties,this part of the study is of great significance to the improvement and remediation of soil chemical properties.The main research contents and results are as follows:1.Broussonetia papyrifera biochar has a typical porous structure and a large specific surface area.Phosphate can absorbed by Broussonetia papyrifera biochar;Functional groups such as C-O,O-H and amide ? are involved in the adsorption process of phosphate by Broussonetia papyrifera biochar;Broussonetia papyrifera biochar mainly carries negative charges on the surface in aqueous solution;Broussonetia papyrifera biochar contains CaCO3 and Ca(COO)2·H2O crystals.(chapter 2)2.The biochar of Broussonetia papyrifera has better adsorption effective under neutral and alkaline conditions.Ca2+,Na+,Cl-and NO3-can promote the adsorption process.Phosphate was mainly combined with Broussonetia papyrifera biochar in Ex-P,Al-P and Fe-P.The second-order adsorption model can better fit the adsorption process,the chemical adsorption reaction was the main rate-limiting step in the adsorption process.The Freundlich model fitted the adsorption isotherm data best at 25?,whereas the Langmuir model provided the best fit at 35?.The theoretical maximum adsorption capacity at 35? is 28.2 mg/g.(chapter 3)3.The soil pH value increases with the increase of the amount of two kinds of biochar,and the effect of unadsorbed biochar on the soil pH is stronger than that of adsorbed biochar,two kinds of Broussonetia papyrifera biochars added to soil can increase soil organic matter content.With the increase of the amount of biochar added by two species of biochar,the content of available nitrogen in the soil showed a trend of rising first and then decreasing.The content of available phosphorus in the soil increased with the increase of the addition amount of two biochars,and the effect of adsorption of absorbed biochar on the soil was stronger than that of unabsorbed biochar.(chapter 4)In this study,the leaves of Broussonetia papyrifera grown in the manganese mine area were used as resources to prepare a kind of biochar with good adsorption effect on phosphate,and it can effectively improve the soil chemical properties.This provides potential remediation materials for subsequent eutrophication control of water bodies and soil remediation. |
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