Biochar derived from chicken manure as a green adsorbent for naphthalene removal

In this study, biochar was generated from chicken manure by using a tube furnace under different temperatures (300, 500, and 700 °C), and the treatments were noted as J300, J500, and J700, respectively. In comparison, another type of biochar was prepared under 500 °C with a muffle furnace, and the treatment was noted as JM500. Biochar in treatment group J500 was subsequently modified with HNO₃ and NaOH, and the treatments were noted as J500-HNO₃ and J500-NaOH, respectively. The sorption efficiencies of naphthalene by the above six types of biochar were evaluated. Characteristic results showed that the surface pores of the biochar were improved with the increase of temperature, and biochar under the treatments J300, J500, J700, and JM500 experienced a high speed of adsorption within 1 h after the naphthalene adsorption started. The adsorption capacity of naphthalene increased with the increase of the initial concentration of naphthalene. Treatment J700 exhibited the largest adsorption capacity since its biochar surface pore structure was more fully developed with a crystal structure formed, and its specific surface area was increased by about 20 times compared to the original chicken manure. After biochar modification using HNO₃ and NaOH, the infrared spectrum changed, and the adsorption active sites were increased. The biochar modification by HNO₃ had a high naphthalene adsorption efficiency compared to NaOH. The order of adsorption capacity was as follows: J500 ≈ JM500 < J300 < J500-NaOH < J500-HNO₃ < J700.