Sorption of sulfathiazole in the soil treated with giant Miscanthus-derived biochar: effect of biochar pyrolysis temperature, soil pH, and aging period

Abstract

Agricultural soil was treated with biochar (5% w/w) produced from two pyrolysis temperatures (400 and 700°C) of giant Miscanthus (GMC-400 and GMC-700, respectively), and the subsequent sorption of sulfathiazole (STZ) was evaluated as a function of pH (2, 5, and 7) and aging period (0, 3, and 6months). Because sorption was nonlinear, with 0.51<N<0.75, the linearized sorption coefficient (K d*) was used for the comparison across samples. The K d* of GMC-400 treatment (3.96-9.96Lkg-1) was higher than that of GMC-700 treatment (1.27-3.38Lkg-1). In laps of aging period over 6months, the sorption of GMC-400-treated soil had gradually increased to be 3.3 times higher than that of untreated soil, whereas there was no statistical difference for GMC-700 treatment. Results of FTIR and SEM analyses revealed that the number of O-containing functional groups in the GMC-400 treatment increases and the micropores of GMC-700 are deformed over time. Sorption was also pH-dependent in the order of pH2>pH5>pH7. The sorption hysteresis (H) index for the GMC-400 treatment was higher at pH7 (3.99) than at pH5(2.53), and both values had increased after 6months (4.18 and 3.17, respectively). The results of this study clearly demonstrate that the sorption of STZ on GMC-treated soils is greatly enhanced, mainly through the greater micropore surfaces, the abundance of hydrophilic functional groups over time, and π+-π electron donor-acceptor interaction at low pH.