Preparation of sludge-based hydrochar at different temperatures and adsorption of BPA

This study sought a new way to utilize sludge as a low cost and efficient adsorbent. Preparation of sludge adsorbent by hydrothermal carbonization was done at different temperatures (160-250 °C). Various characterization techniques were used in this study including elemental analysis, Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). The adsorption performance of the organic matter was analyzed by adsorption experiments with the endocrine disruptor bisphenol A (BPA). Results showed that as the hydrothermal temperature increased, the solid yield of hydrochar decreased from 84.73% to 55.19%, and the maximum specific surface area was 11.9 m²/g. Elemental analysis showed that the hydrochar contains more aromatic carbon than the raw sludge. It was found using the FT-IR and XPS that the hydrochar retains a large amount of oxygen-containing functional groups on the surface after hydrothermal treatment. Hydrochar can be used as an organic-pollutant adsorbent in water; it has a good adsorption effect on BPA and the removal rate can reach 96%. The adsorbed hydrochar can be hydrothermally retreated and returned to the sewage treatment plant for reuse.