Effects of pyrolysis temperature on the physicochemical properties of biochar derived from vermicompost and its potential use as an environmental amendment

Abstract

The physicochemical properties of biochars, produced from vermicompost and subject to pyrolysis at temperatures between 400–700 °C, were investigated, as well as their potential application as an environmental absorbent. Results indicated that the biochar yields were relatively high throughout this temperature range, but it decreased from 78.1% to 70.6% as the pyrolysis temperature increased to 700 °C. The mineral nutrients and heavy metals in the biochars were also condensed as the pyrolysis temperature increased. Additionally, the pyrolysis temperature also positively affected the formation of total basic functional groups (TBFGs) and pore development. The biochars generated from vermicompost were characterized by alkalinity, high stability, high buffering ability and high apparent density. When the biochars were employed as an adsorbent for removing heavy metal ions, dyes and organic contaminants, the biochars generated at higher temperatures possessed better adsorption abilities of these contaminants, and the maximum adsorption capacity of the biochar at 700 °C was 36.4 mg g⁻¹, 29.5 mg g⁻¹, 12.4 mg g⁻¹, 12.3 mg g⁻¹, 17.8 mg g⁻¹, and 8.2 mg g⁻¹ for Cu²⁺, Cd²⁺, methyl orange, rhodamine B, naphthalene, and nitrobenzene, respectively.