Synergetic interaction of lithium cobalt oxide with sulfite to accelerate the degradation of organic aqueous pollutants

Abstract

Heterogeneous activation of sulfite by synthetic lithium cobalt oxide (LCO) to treat simulated dye wastewater is developed in this study using Rhodamine B (RhB) as the model pollutant. Synergistic, independent and antagonistic interactions between LCO and Na2SO3 were observed under acid (pH = 3), neutral and alkaline (pH = 10) conditions, respectively. A high mineralization rate of 84% was obtained with 200 mg of LCO and 50 mg of Na2SO3 at pH = 3 for 50 mL of 5 mg L−1 RhB substrate. Even hand-shaking with 13 mg of LCO and 3 mg of Na2SO3 for only 30 s could realize full de-colorization. Moreover, one-time dosage of 13 mg of LCO and 3 mg of Na2SO3 worked effectively in twenty consecutive batches only if Na2SO3 was periodically supplemented. The radical-trapping experiments determined the SO3•- radical as the dominant reactive species and oxygen vacancies were responsible for sulfite activation. In addition to RhB, the sulfite-enhanced protocol has been universally demonstrated with methyl blue and methyl orange. This paper reflects well the sustainability concept of reusing “wastes” for pollution control since LCO is a key component in the cathode material of abandoned lithium-ion batteries and sulfites are the byproducts of flue gas desulfuration.