Development of biochar from crofton weed & relationship between biochar properties and its applicability as a heavy metal removal activity

Biochar is a pyrogenic black carbon produced from thermal degradation of carbon-rich biomass (<700°C) in an oxygen-limited environment, and usually has a porous structure, a surface rich in oxygenated functional groups, strong adsorption capacity, and a certain degree of surface area and stability. Biochar has multiple uses, including agricultural applications for soil remediation and pollution control in water and soil. Biochar has several significant socioeconomic and environmental benefits such as carbon sequestration, pollutant removal, and soil improvement. Pyrolysis temperature affects biochar properties, which in turn determines its application potential. The collected Crofton weed (except for the roots) was washed, air-dried at room temperature, and crushed for passage through a 10-mesh sieve. Here, we examined the properties of Crofton weed biochar (C-BC) produced at different pyrolysis temperatures of 300°C, 400°C, 500°C, and 600°C. We measured the yield, ash content, pH, iodine sorption value (ISV), and elemental composition of C-BC. We also characterized C-BC using scanning electron microscopy (SEM), as well as its ability to remove Pb2+and Cd2+contaminantsfrom an aqueous solution. C- BC yield decreased with increasing pyrolysis temperature, whereas ash content and pH increased. ISV first increased at 300–400°C and decreased at 500–600°C. For C-BC produced at pyrolysis temperatures 300–600°C (C-BC300 to C-BC600, respectively), H, N, and O content decreased, but C, Ca, Mg, P, and K content in- creased with increasing temperature. All C-BCs had a certain number of pore structures. Increasing pyrolysis temperatures decreased the amount of -OH, -COOH, aliphatic C-H, and polar C-O on the C-BC surface. The percentage of Pb2+and Cd2+removed increased with increasing pyrolysis temperatures. Overall, for C-BC, a low pyrolysis temperature was beneficial for producing a more porous biochar and increased content of water-soluble calcium, magnesium, nitrogen, and phosphorus, whereas high pyrolysis temperatures yield biochar that had high alkalinity, aromaticity, and stability, as well as heavy metal removal activity