Effects of aerobic composting on physicochemical properties of biochar and the adsorption stability of Cd2+
Biochar can be used as a functional material for removing heavy metals in aerobic composting of livestock manure.But the complex environmental changes inside the pile will affect the physical and chemical properties of biochar,thus affecting its adsorption stability of heavy metals.A 30-day aerobic composting experiment was conducted by placing or-dinary straw biochar(BC)and magnetic straw biochar(FBC)in cow manure to study the basic physicochemical properties of the two types of biochar and the impact on the adsorption stability of Cd2+.The results showed that com-posting treatment increased the specific surface area of BC and FBC by 20.56%and 76.64%,respectively,decreased the total pore volume by 2.36%and 3.70%,and de-creased the average pore size by 19.17%and 46.54%,re-spectively.Moreover,the surface functional groups changed,and the saturation magnetization of FBC decreased by 43.67%.After composting,the proportion of TCLP extract-able Cd(TCLP-Cd)and the pH of TCLP extraction solution(TCLP-pH)of BC and FBC with saturated adsorption of Cd2+showed a decreasing trend.The proportion of TCLP-Cd significantly decreased from 28.31%and 22.85%to 26.76%and 13.85%(P<0.05),respectively,and TCLP-pH significantly decreased from 3.66 and 3.29 to 3.51 and 3.14(P<0.05),respectively.In summary,the composting aging changed the physical and chemical properties of BC and FBC,reduced the content of extractable Cd,and improved the stability of Cd2+adsorption,and the stability of Cd2+in FBC was better.
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