Study on Biochar Adsorption for Cu2+ and Diethyl Phthalate:Effects of Particle Size and Ageing

Author:Ma Shao Qiang

Supervisor:chen jia zuo


Degree Year:2019





Biochar particles will naturally experience geochemical weathering processes that are liable to break up to nano-scale biochar and change its physicochemical properties over time within the soil.It has been noted that nano-scale biochar particles displayed stronger migration potential than other particles,which poses the potential risk of pollutant transfer through the environment.Moreover,the natural physical weathering processes also accompanied by other types of ageing,i.e.leaching,oxidation,etc.In this present study,we systematically conducted the effect of ageing process on Cu2+and DEP(Diethyl phthalate)sorption capacity and mobility by millimeter,micron-and nano-scale biochar using adsorption batch test and soil column test.Nano-scale biochar had higher Cu2+and DEP adsorption capacity than millimeter and micron-scale biochar.The surface complexation and pore filling dominated Cu2+and DEP adsorption on nano-scale biochar,respectively.It indicated that the immobilization Cu2+and DEP in soils would increase as biochar becomes finer over the longer term.In addition,the adsorption capacity of biochar for Cu2+and DEP increased significantly when the environmental pH changed from 3.0 to 5.0,indicating that alkaline environment might contribute to the immobilization of Cu2+and DEP in soil.Long-term oxidative ageing was simulated using 5%H2O2 Our results showed that the oxidative ageing process on biochar would slightly decrease Cu2+and DEP adsorption capacity by reducing its microporous structure and surface functional groups.Freeze-thaw cycles process destroyed the microporous structure of nano-particle biochar and thus decreased DEP adsorption capacity.However,it increased millimeter biochar adsorption capacity of DEP by introducing more pores on biochar surface.The soil column experiments showed that cinnamon soil had higher Cu2+sorption capacity than laterite soil.Biochar addition could dramatically increase Cu2+sorption capacity in laterite soil,whereas,it was not effective in cinnamon soils.In addition,nano-scale biochar was most efficient in Cu2+ immobilization in laterite soil.Thus,biochar addition in acidic laterite soil in southern China might be effective for Cu2+ immobilization.However,the Cu2+adsorption capacity in laterite soil decreased by adding freeze-thaw cycle aged biochar,indicating under freeze-thaw cycle environment,biochar might release fixed metal in laterite soil during long-term acCu2+mulation,the secondary pollution would bring risks to the environment.