Study On Heavy Metal Pollution In Water And Soil By Bedding Materials Derived-biochar

With the development of industrialization, the pollution of heavy metals in water and soil of our country is becoming more and more intensified. Biochar is porous, of a large surface area, has a high degree of aromatic, anti-decomposition and thermal stability, can absorb heavy metals from the polluted environment, can also promote the absorption of plants to nutrient elements. The bedding materials, as the final residue of the "zero discharge" of the bio-bed pig rearing, can determine whether the model can be used on a large scale. Therefore, this research chose the bedding materials as raw materials with rice straw as a contrast group. Using limited oxygen pyrolysis to manufacture the bedding materials derived-biochar (D300, D400, D500) and rice straw derived-biochar (S300, S400, S500) at different temperatures (300,400 and 500℃). And their physical and chemical properties were analyzed by means of X-ray spectrometer, scanning electron microscopy (SEM) and fourier transform infrared spectrometer (FTIR). Adsorption and its influential factors of biochar to Cd2+ in aqueous solution were investigated including the different adsorption time and different concentration of Cd2+ and different initial pH conditions. The amendment to contaminated soil by the biochar was tested by the methods of potting plants, leaching and etc. The main conclusions are as follows:(1) Bedding materials derived-biochar on the adsorption of Cd2+ reached apparent equilibrium in 30h, later than the time required for rice straw derived-biochar. The adsorption capacity of the three kinds of bedding materials derived-biochar was:D400>D300>D500, the saturated adsorption capacity of Cd2+ to 21.52mg/g was D400. The adsorption process of D300 and D400 was more consistent with the quasi two level dynamics model, and the adsorption process of D500 was more in line with the particle diffusion model, and the adsorption rate of D400 and D300 was slower. In the range of pH, the adsorption effect on Cd2+ was better in the range of 4.5～7.5. The adsorption capacity of Cd2+ was slightly worse than that of rice straw derived-biochar, but the difference was not significant.(2) The pH value of Cd2+ contaminated soil became significantly high after adding biochar to the soil. The increase of pH after the addition of S500 was much higher than that of D500. Biochar had a very good fixation effect on Cd2+, which could greatly reduce the biological effectiveness of Cd2+. Compared with S500, the fixation effect of D500 was better, and the effect of adding biochar on the yield of brassica chinensis was obvious. After 5% S500 and D500 were applied to the contaminated soil, the concentration of Cd2+ in the brassica chinensis was reduced, but the concentration of Cd2+ in the brassica chinensis was not so as to meet the requirements of the national standard. The effect of D500 on reducing the heavy metal Cd2+ in the brassica chinensis was better than that of S500.(3) The bedding materials derived-biochar was not inferior to the rice straw derived-biochar about the remediation of heavy metal Cd2+ in the water and soil. It is feasible to use the waste material of the fermentation beds to prepare the biochar to repair the heavy metal pollution in the water and soil and improve the soil fertility.