Co-incineration of medical waste in municipal solid waste incineration increased emission of chlorine/brominated organic pollutants.

Co-incineration of medical waste (MW) in municipal solid waste incinerators (MSWIs) is a crucial disposal method for emergency disposal of MW and the management of MW in small and medium-sized towns. This study aims to analyze and compare the levels and distribution patterns of chlorine/brominated dioxins and their precursors in fly ash from MSWIs and medical waste incinerators (MWIs) while also focusing on identifying the new pollution concerns that may arise from the co-incineration of municipal solid waste (MSW) mixed with MW (MSW/MW). The concentration of chlorobenzene (CBzs), polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) in fly ash from co-incineration of MSW/MW are 887.4, 134.4 and 27.6 µg/kg, respectively, which are 5.1, 2.0 and 2.9 times higher than that from MSWIs. The levels of polybrominated dibenzo-p-dioxins/dibenzofurans (PBDD/Fs) are about three orders of magnitude lower than that of PCDD/Fs. For the fly ash from MSWIs, the predominant PCDD/Fs congener is OCDD, which prefers synthesis and adsorption on fine-grained fly ash. For fly ash from MWIs, the major PCDD/Fs congeners are 1, 2, 3, 4, 6,7, 8-HpCDF, and OCDF, which prefer synthesis and adsorption on coarse-grained fly ash. Correlation analysis exhibited that both 1,2,3-TriCBz and 1,2,4-TriCBz in fly ash have a markedly linear correlation with PCDD/Fs and PCBs, but PBDD/Fs shows a poor negative correlation with PCDD/Fs.

Degradation and mechanism of PAHs by Fe-based activated persulfate: Effect of temperature and noble metal.

The accumulation of contaminants like PAHs in soil due to industrialization, urbanization, and intensified agriculture poses environmental challenges, owing to their persistence, hydrophobic nature, and toxicity. Thus, the degradation of PAHs has attracted worldwide attention in soil remediation. This study explored the effect of noble metal and temperature on the degradation of various polycyclic aromatic hydrocarbons (PAHs) in soil, as well as the types of reactive radicals generated and mechanism. The Fe-Pd/AC and Fe-Pt/AC activated persulfate exhibited high removal efficiency of 19 kinds of PAHs, about 79.95 % and 83.36 %, respectively. Fe-Pt/AC-activated persulfate exhibits superior degradation efficiency than that on Fe-Pd/AC-activated persulfate, due to the higher specific surface area and dispersity of Pt particles, thereby resulting in increased reactive radicals (·OH, SO4-· and ·OOH). Additionally, thermal activation enhances the degradation of PAHs, with initial efficiencies of 64.20 % and 55.49 % on Fe-Pd/AC- and Fe-Pt/AC-activated persulfate systems respectively, increasing to 76.05 % and 73.14 % with elevated temperatures from 21.5 to 50 °C. Metal and thermal activation facilitate S2O82- activation, generating reactive radicals, crucial for the degradation of PAHs via ring opening and oxygen hydrogenation reactions, yielding low-ring oxygen-containing derivatives such as organic acids, keto compounds, ethers, and esters. Furthermore, understanding the impact of parameters such as activation temperature and the types of noble metals on the degradation of PAHs within the activated persulfate system provides a theoretical foundation for the remediation of PAH-contaminated soil.