From technical HCH residues to industrial relevant vicinal dichlorinated compounds: Electrochemical chlorine transfer as a strategy for waste valorisation

For over 70 years, the remains of Lindane production have contributed to tremendous global environmental problems. The manufacturing process of 1,2,3,4,5,6-hexachlorocyclohexane (HCH) yields approximately 15% of the insecticidal γ -isomer, which is called Lindane. This has led to the accumulation of estimated 7.4 million tons of waste worldwide that have in most cases not been properly disposed. In addition, the HCH has carcinogenic, genotoxic, mutagenic, and teratogenic effects. The large quantities of this persistent residue, which continue to spread into the environment, highlight the urgent need for remediation. Although numerous processes for water treatment have been extensively described, all the established methods currently rely on incineration. In this context, electrosynthesis represents a promising and sustainable approach to transform HCH into benzene, while simultaneously enabling the released chlorine to upcycle terminal alkenes into vicinal dichloro products. Since this process must be economically competitive with conventional incineration, the present study investigates the key characteristics of the proposed e-shuttle reaction. Several industrially relevant chloro compounds are optimized in terms of their molar yields related to HCH input. Additionally, the kinetics of the reaction are studied using a representative substrate, and the potential for chlorine upcycling is assessed. Finally, an economic feasibility analysis is conducted for a plant designed to upcycle annually 5 000 metric tons of HCH. • The e-shuttle approach enables the selective upcycling for all isomers of HCH to benzene, using graphite electrodes and propylene carbonate as solvent. • Electron-rich polar unsaturated bonds are particularly well suited for halogenation in propylene carbonate. • Kinetic measurements of technical HCH degradation on dichloro product formation were obtained using a sample substrate. • Various process development experiments demonstrated the feasibility of scale up the electrolyser and down streaming of the process. • Monte Carlo modelling quantifies the economic and ecological viability of this process.