UV-Induced Redox Conversion of Tellurite by Biacetyl

Tellurium (Te) is a rare element of great value, but it exists mainly in the toxic form of tellurite (Te^IV) in water. Effective approaches that are able to reduce the toxicity and recover Te from contaminated water are highly needed. Here, we developed a simple but effective way to reduce toxic Te^IV to widely applicable elemental Te⁰. With the combination of ultraviolet (UV) and biacetyl (BD), the oxidation state of Te could be feasibly changed from IV to 0 or VI. The consumption of dissolved oxygen (DO) was a key factor in the redox conversion of Te^IV. Under UV irradiation, BD was first cleaved to acetyl radicals, which could then combine with water molecules to form more reductive diol radicals or combine with DO to form strongly oxidative peroxide radicals. Even without deoxygenation, the UV/BD system could rapidly change from being oxidative to being reductive because of the fast depletion of DO. Owing to the high quantum yield of the acetyl radical, the reduction efficiency of the UV/BD system was about 1 order of magnitude higher than that of UV/sulfite and was more efficient than the commonly used biological methods. This work provides a proof of concept for the reduction of tellurite, which could have relevant implications for water treatment and resource recovery applications.