A Study On Sorption And Locking Effect Of Cr(Ⅵ) And Artrazine In Biochar-amended Soil

Biochar are increasingly attracting everyone’s attention for its environmental and economic advantages. Biochar are made from animals and plants’ residues. The agricultural and forestry waste recycling itself is a green, energy-efficient, sustainable process. The stored unstable residual carbon in the body of animals and plants can be transferred to biochar which has stable physical and chemical properties as well as reducing carbon dioxide emissions. Biochar surface also contains nitrogen, phosphorus and other beneficial elements. Because of its own large surface area, rich in voids and a lot of organic functional groups adding biochar to farmland not only can improve soil properties, lands qualities, but also increase crop yields. Moreover biochar also have good adsorption capacity, which could lock the pollutants and reduce biological contaminant migration. This paper investigated the biolchar adsorption capacity and discuss the biochar locking effect to hexavalent chromium and atrazine. In the experiments biochar was acidized to improve the adsorption capacity of atrazine and the paper also argues the reasons of the improving.Experimental results showed that only 1% of biochar especially the small size could greatly improve the fixing capacity of Cr(VI) in the the soil system. The adsorption capacity of small size biochar was three times than the large size biochar and it’s not easy to desorb under acid rain. It means biochar can inhibit the Cr(VI) migration in the soil.Freundlich Equation Fitting experiments showed that the acidification of biochar could improve the adsorption capacity for atrazine. With the increasing temperature, the adsorption capacity also increased.The results were in line with Elovich Kinetic Equation to pre-acidification biochar and with prospective second-order equation after acidification of biochar, respectively. The change of the equations mean that the acidification makes effects on the adsorption mechanism. The better atrazine adsorption capacity of biochar mainly due to the increasing surface area, pore sizes and the pore volume etc.by acidification, which make the biochar get more adsorption sites and stronger van der Waals forces. Meanwhile the change of the surface potential of biochar generated stronger electrostatic attraction between atrazine and biochar. That is the reason for the better adsorption effects of the acidification biochar.The soil system adsorption capcity of atrazine fixing effects was significantly improved after adding biochar into soils. The more amount of biochar added into the soil, the better adsorption effects achieved. In a one week culture test biochar have no significant desorption and perform a good stability. The main factors that affect the capacity of biochar adsorption after its acidification are not the size of soil particles but the soil moisture content. After a long period of high soil moisture status, the acidification biochar adsorption capacity declined.