Adsorption of cadmium by iron-modified cassava residue biochar

Abstract

Soil is the foundation of human development, but with more and more development activities, a large number of heavy metal elements are deposited in the soil, which destroys the ecological environment balance. Heavy metal is an important factor causing soil pollution in China. Among them, cadmium (Cd), as one of the most toxic heavy metal elements, is easily absorbed by plants and has strong mobility, so it is difficult to degrade in the environment. Under the sustained development of industry and agriculture, some areas of China's land have been polluted by Cd. Currently, in situ remediation of Cd in soil using BC can reduce the bioavailability of such heavy metals, showing a good development trend in heavy metal remediation. In this study, cassava residue was used as raw material to produce BC at 400 ℃, and then modified with nanoscale Fe (NO3) 3 to produce five types of iron modified BC (BC-Fe) with a carbon iron mass ratio of 1:0.05, 1:0.075, 1:0.1, 1:0.125, and 1:0.15. Finally, Cd2+adsorption experiments and characterization analysis were conducted. The following results were obtained: When the conditions were consistent, BC-Fe had a higher ability to adsorb Cd compared to the original BC, especially BC-Fe (1:0.125) performed the best, achieving adsorption equilibrium after 240 minutes, while BC needed 480 minutes to achieve. At the same time, its adsorption rate was significantly lower than BC-Fe (1:0.125). The characterization analysis results show that BC-Fe (1:0.125) exhibits a rough layered structure, and the surface of BC gradually loses regularity, which helps to fully volatilize the organic substances contained in BC; In terms of pH value, BC-Fe (1:0.125) is higher than BC, and an increase in pH value is helpful for adsorbing Cd; In terms of ash content, BC and BC-Fe (1:0.125) each account for 42% and 49%, respectively. The latter belongs to high ash BC and is beneficial for adsorbing heavy metals.