Biochars Characteristics From Biomass Residues Produced Through Slow Pyrolysis And Amendment Of Albic Soil Mercury Pollution

Biochar is produced by thermal decomposition of various biomass under oxygen-limited conditions(pyrolysis), and it has been well considered to be a nice modifying agent in both soil remediation and waste disposal.After pyrolysis process, biochar obtains great characteristics including large surface area, highly aromatic structure which make it absorptive and stable in soil. Biochar can make a difference by improve the granular structure of soil. Discovering the characteristics of biochar is of great importance on soil improvement mechanism,it can also offer the basic data for the following research. In the difficult time to deal with agricultural residues, biochar offer a new method to make waste useful.This article selected 5 kinds of biomass feedstocks to discover the characteristics of biochar, including soybean straw, corn straw, rice straw, rice husk and pine needle, they were pyrolysed for two hours at 300?C, 400?C, 500?C, 600?C and 700?C, respectively. After the biochar cooled down, the structure was observed, The surface area of biochar was measured. The proximate analysis for the element content was carried out. The p H measurement was determined by an Orion PH meter. Cation exchange capacity(CEC) of biochar was measured. The amount of functional groups of biochars was determined. The experiment of the amendment of albic soil mercury pollution was carried out by simulating the polluted environment by potting, the form of mercury was determined.The result shows: the structures and phychemcial characteristics of biochars derived from different feedstocks were compared. Biochars carbonized well and showed a clearer structure after pyrolysis. And BET surface area, T-Plot micropore volume, p H and CEC of biochars increased with the rising of the pyrolysis temperature. The surface areas of biochar derived from corn stalk and soybean were the highest at 700?C. However, the average pore diameter of biochars decreased with the pyrolysis temperature increased. Biochar made from corn stalk at 500~700?C pyrolysis temperature showed better properties than that other raw feedstocks, suggesting that it could be applied into acidic soil because of providing nutrients and minerals, and holding water, adsorbing organic pollutants. Biochar derived from rice husk had the highest content of Si at 700?C. Biochar derived from pine needle was acidic at 300~500?C, illustrating that it would be used in alkalescent soil as amendment agent.Adding biochar into albic soil which is polluted by mercury, the results show the absorptive form of mercury:water-soluble and exchange state have reduced obviously, humid acid combined state and ferrimanganic oxidation state have also reduced while organic bond and residual form have increased obviously, when the addition of biochar comes to 7%, the residual form increased by 2.73%, 2.87%, 2.47%, 2.82% under different addition of mercury compared with no addition of biochar. The result shows with the addition of biochar, the absorptive mercury in albic soil transfer into less aborbed forms, biochar has inactivition to mercury in albic soil.