Toxicant Suppression in Co-pyrolysis of Chlorinated Paraffin- Containing Waste and N-Enriched Biomass

Pyrolysis is generally used to recycle and reuse plastic rubber and biomass waste. However, thermal cracking and recombination reactions of coexisting substances, such as chlorinated paraffins and protein, can induce toxic byproducts, including Cl-containing matter and alkali metal cyanides (MCN, e.g., NaCN and KCN). In this study, the simultaneous suppression of Cl volatilization and MCN formation was successfully achieved by the co-pyrolysis of two complementary wastes, including chlorinated paraffin-containing waste and N-enriched biomass. In the low-temperature co-pyrolysis reaction, the Cl atoms in the chlorinated paraffins were seized by the inherent alkali metals (Na or K) in the biomass to form NaCl or KCl in the biochar, leading to the suppression of Cl volatilization. This process simultaneously blocked the N atoms in the protein involved in the complexation reaction, thereby reducing the formation of NaOCN or KOCN (MCN precursor). In the high-temperature co-pyrolysis reaction, the reduction of NaOCN or KOCN and the physical barrier of NaCl or KCl adherence inhibited the formation of NaCN or KCN owing to the weakened carbothermal reduction. This proposed co-pyrolysis method represents a cost-effective technology that simultaneously suppresses Cl volatilization and MCN formation, reducing secondary pollution in the comprehensive utilization of solid wastes.