Preparation Of Biochar And Its Application In Environmental Remediation Of Heavy Metals

In recent years, the heavy metal contamination is getting worse along with industrialization and social progress. Heavy metal pollutes the atmosphere, water and soil,endangers human health and affects the normal human life. With the improvement of people's living standards, the peasant is no longer dependent on straw as life energy. There are plenty of straw is discarded which pollutes the environment and making security risk every year. It is important using the straw reasonable and utilization for energy saving. Biochar is a product of the biomass feedstock in anoxia or hypoxia closed environment pyrolysis?<700 ?? resulting carbon-rich. Since straw rich in cellulose, is an important raw material of biomass charcoal produced. So the main purpose of this study was to work out the optimal biomass charcoal production scheme. Then, the biochar screened under different conditions of preparation was used to explore its adsorption of heavy metal contaminated wastewater and heavy metal contaminated soil passivation ability. The results are as follows:?1? Biochar was prepared in slow pyrolysis.The biomass carbon char yield by carbonization time, carbonization temperature, the particle size of raw materials, the impact of three significant order of carbonization temperature >> Straw diameter> carbonization time,and biomass carbon char yield with increasing carbonization temperature drops significantly.The three straw produced biochar which surface was modified of Cu and Cd adsorption capacity is greater than the unmodified biomass charcoal. But there is a big improvement differences adsorption capacity of Cu and Cd between different modified biomass carbon.Combining with different mode of preparation, the modified cotton and wheat straw enhance the adsorption capacity significantly and the corn stalks enhance smaller. Considering the char yield, energy supplies and heavy metal adsorption capacity factors, the final screening of biochar treatment of heavy metal Cu and Cd pollution of the environment: biomass charcoal treatment of heavy metals Cu was GA3?cotton stalks, modified, 300 ?, 6h, 100 mesh?,adsorption capacity of 32.4mg / g; treatment of heavy metals Cd biomass charcoal B9?not modified, 300 ?, 3h, 100 mesh?, adsorption capacity of 19.5mg / g.?2? The biomass carbon testing for adsorption of Cu²⁺ and Cd²⁺ can be well fitted with a quasi-second order kinetics, indicating that the adsorption of Cu²⁺and Cd²⁺on biomass carbondividing into two reaction speed phases. Modified for biomass carbon adsorption capacity of heavy metals increases significantly. Biochar carbonized after the same kind of straw prior to crushing and pulverizing under carbonization two processes for preparing are the same as its adsorption properties, but the adsorption vary. With Langmuir equation to calculate the A3 and GA3 biochar for Cu²⁺ maximum adsorption capacity was 10.00 mg / g and 33.33 mg / g, A9 and B9 biochar was 14.29 mg / g and 20.00 mg/ g for Cd²⁺maximum amount of adsorption.Freundlich fitted with a value of n greater than 1, indicating that Cu²⁺ and Cd²⁺ adsorbed on the biomass charcoal are preferential adsorption. By adsorption kinetics and thermodynamics adsorption experiments, We can find further evidence of the water environment of heavy metals Cu contamination repair using GA3 biomass carbon, water environment for the restoration of Cd using B9 biomass carbon.?3? After three soils was applied to biomass carbon, the content of available heavy metal Cd in soil has significantly reduced compared to the control. Adding biochar in the early days,effective state of Cd decreased the fastest, and then gradually slowed, and in 30 to 40 days stabilized. With the application of increasing biochar intake, the effective content of heavy metal Cd declined little change, but the decline rate was a big difference. Under three dosage for the three soil, the content available of heavy metals Cd can be reduced by 30% in 40 days.When corn stover biomass charcoal dosage of 5%, after 40 days passivation culture, the content available of heavy metals Cd in soil, cinnamon, brown decreased by 34.1%, 39.1%,34.1%. It proved B9 biomass charcoal was suitable for remediation of polluted soil of heavy metal Cd. Biochar added to cinnamon has the best effects of heavy metal pollution. The effective content of Cd also tended to decrease in blank experiment of soil, cinnamon and brown in 40 days, decreased by 23.5%, 22.5%, 11.1%.In summary, overall economic efficiency, we can select the best preparation parameters by comparing the biochar's adsorption capacity of heavy metals which prepared under different parameters. The biomass carbon prepared under this parameter were used for water and soil environment repair of heavy metals, achieved good results. It proved the value of this study.