Photochemical behavior of dissolved organic matter in process water from hydrogen peroxide assisted hydrothermal carbonization of sludge

In this study, HTC and 4% H2O2-assisted HTC were used to treat dewatered sludge. Based on the determination of the basic physicochemical properties of the two process-water DOMs, we focused on comparing the photobleaching behaviors of the two DOMs and the generation of photogenerated species. The results showed that DOM derived from H2O2-assisted HTC process water had lower pH, higher conductivity, TOC, humic-like substance content, aromatic functional groups, molecular weight, and degree of humification, and exhibited greater photosensitivity compared to DOM form HTC process water. Under the simulated natural light irradiation conditions, the aromaticity and humicity of DOM decreased with the prolongation of light exposure, and the content of fluorescent components in DOM decreased significantly, with the humic-like components decreasing most significantly. During the irradiation process, more singlet oxygen (1O2) and triplet excited state (3DOM*) were generated, which can significantly promote the photodegradation of tetracycline (93.22%), and 3DOM* played a leading role. This study clarifies the photochemical behavior of DOM derived from H2O2-assisted HTC, which can provide a theoretical basis for the further treatment and utilization of process water produced by HTC of sludge. © 2024 Chinese Society for Environmental Sciences. All rights reserved.