Oxidation of Lindane with Fe(II)-Activated Sodium Persulfate

Lindane or γ-hexachlorocyclohexane (γ-HCH) is a known carcinogen and a notoriously persistent organic pollutant in the environment. Reported herein is a study of lindane oxidation by persulfate (S2O82−) in aqueous solution (22 ± 1°C). Persulfate is quickly activated by ferrous iron, and produces highly potent sulfate radicals (SO4−·) with standard potential at 2.6 V. The rate of lindane oxidation is proportional to the concentration of persulfate, and when the ferrous iron to persulfate concentration ratio is less than 1, the reaction rate is also proportional to the ferrous iron concentration. The reaction rates were substantially higher when the solution pH was less than 1.5 or greater than 11. The final products are chloride and carbon dioxide, suggesting complete lindane oxidation. The reaction half-life of oxidation of 0.0172 mM lindane with 4.2 mM persulfate and 0.108 mM ferrous iron was approximately 27.18 h. Compared to the classical Fenton's reaction, persulfate has relatively longer lifetime in water.