Influence of the Pyrolytic Temperature and Feedstock on the Characteristics and Naphthalene Adsorption of Crop Straw-derived Biochars

The feedstock type and pyrolytic temperature used in producing biochar influence the characteristics of the obtained product and affect the adsorption behavior of naphthalene. In this study, different biochars were pyrolyzed from wheat straw, soybean straw, and corn straw at four temperatures (400 °C to 700 °C). Analyses of the elemental composition, pH, ash content, and specific surface area, scanning electron microscopy, and Fourier transform infrared spectroscopy were performed. The adsorption variations of the naphthalene for the different biochars were evaluated. The results showed that as the pyrolytic temperature increased, the carbon content, ash content, and pH of the biochars increased, the hydrophilicity, aromaticity, and polarity decreased, and the naphthalene adsorption was enhanced. The pseudo-second-order model fit the naphthalene adsorption kinetics better. Both the Langmuir and Freundlich isotherm models confirmed that naphthalene adsorption by all of the produced biochars were effective. Under moderate pyrolytic temperatures, the soybean straw-derived biochar showed a greater naphthalene adsorption capacity and faster adsorption rate than the wheat straw- and corn straw-derived biochars. This study provides a theoretical basis for selecting crop residues and optimizing the pyrolytic temperature with a high efficiency of naphthalene removal from water.