Exploring N/S-Based Polymers for Synergistic Inhibition of Multiple Unintentional Persistent Organic Pollutants during Iron Ore Sintering

Abstract

The iron ore sintering process is a major source of unintentional persistent organic pollutants (UP-POPs). Although challenging, it is important to develop effective and economical methods suitable for practical application to control these highly toxic pollutants. In this study, three novel N/S-based macromolecular compounds, i.e., urea-formaldehyde resin (UFR), thiosemicarbazone-formaldehyde resin (TSCFR), and thiourea-formaldehyde resin (TUFR), were synthesized and investigated for their inhibitory effects on chlorinated benzene (CBz), polychlorinated biphenyl (PCB), and polychlorinated dibenzo-p-dioxin/dibenzofuran (PCDD/F) formation in iron sintering fly ash. TUFR exhibited the highest inhibitory efficiency among the three inhibitors for CBzs (97.6%), PCBs (97.1%), and international toxic equivalent quantity PCDD/Fs (99.9%) with 2.0 wt % addition. Variation of UP-POP homolog profiles indicated that the reaction of N and Cl mainly occurs in the gas phase, while S acts mainly in the solid phase during the inhibition process. The gas–solid phase homolog distribution of UP-POPs indicates that sulfur compounds were the dominant inhibitor and were easily reacted with copper chloride, which was confirmed by density functional theory calculations. TUFR showed 46.9% CBz, 82.9% PCB, and 58.8% PCDD/F reduction efficiencies in a pilot-scale sintering system, indicating that TUFR is an appropriate technique for reducing UP-POP emissions in a full-scale iron ore sintering process.

Br-to-Cl Transformation Guided the Formation of Polyhalogenated Dibenzo-p-dioxins/Dibenzofurans

“…With the increase in Br content, the percentage of CBzs in the gas phase increases from 47.1 to 57.2%. This can be attributed to the increasing trend of the dichlorobenzene (DiCBz) fraction (Figure S1a), which is primarily collected in the gas phase (Figure b). , …”

“…This can be attributed to the increasing trend of the dichlorobenzene (DiCBz) fraction (Figure S1a), which is primarily collected in the gas phase (Figure 1b). 22,26 3.1.2. Congener Patterns of PCDD/Fs and PBDD/Fs.…”