Synergistic effect of the presence of suspended and dissolved matter on the removal of cyanide from coking wastewater by TiO₂ photocatalysis

ABSTRACT

This study assesses the influence of the presence of suspended and dissolved matter on the efficiency of TiO₂ photocatalysis for the removal of cyanide from coking wastewater. Photocatalytic processes were carried out at basic pH (pH 9) with titanium dioxide (1 g/L), artificial radiation (290–800 nm) and during different time periods (20–100 min). The first assays applied in aqueous solutions achieved promising results in terms of removing cyanide. The maximum cyanide removal obtained in coking wastewater was 89% after 80 min of irradiation in the presence of suspended and dissolved matter. The presence of suspended matter composed of coal improves the efficiency of the photocatalytic process due to the synergistic effect between carbon and TiO₂. The absence of dissolved matter also improves the process due to the minimization of the hydroxyl radical scavenging effect produced by carbonate and bicarbonate ions. On the other hand, the presence of certain species in the real matrix such as silicon increases the activity of the titanium dioxide catalyst. In consequence, the improvement achieved by the photocatalytic process for the removal of cyanide in the absence of dissolved matter is counteracted.

KEYWORDS:

• Activated carbon
• coking effluent
• cyanide
• inorganic anions
• photocatalysis
• titanium dioxide

Funding

This work was funded by the DGA-FSE Research Team T33 and the JIUZ2014-TEC-11 Project: ‘Eliminación de cianuros en aguas mediante procesos de oxidación avanzada’ funded by the University of Zaragoza.