The preparation of black titanium oxide nanoarray via coking fluorinated wastewater and application on coking...

Coking wastewater is extremely toxic with poor biodegradability owing to the presence of refractory organics. Black titanium oxide nanotube array (BTN), not only photocatalyst but also electrocatalyst, is with definite potentiality in organic wastewater treatment. Here, we firstly developed an electrochemical method, using fluorinated coking wastewater as electrolyte rather than traditional fluorinated ethylene glycol, to prepare titanium oxide nanoarray economically. Unexpectedly, suspended pollutants and ammonia nitrogen in coking wastewater were removed in BTN preparation. Moreover, the as-prepared BTN could be further employed as photocatalyst or electrocatalyst to degrade dissolved organic matter in coking wastewater. As an electrocatalyst, BTN possessed the comparable •OH production activity about 9.9 × 10^-15 M S^-1 to boron-doped diamond, high oxygen evolution potential around 2.75 V, and high selectivity of chlorine production. Moreover, the biodegradability of treated coking wastewater could be effectively improved by using BTN as electrocatalyst in electrochemical oxidation, and the BOD/COD was from 0.19 to above 0.3 in 4 h at current density of 2 mA cm^-2. The energy consumption was about 63-68 kWh kgCOD^-1, lower than that of various reported electrodes. This study provided an economical and environmentally friendly method to prepare BTN, which was with positive application prospect in the field of coking wastewater treatment.