Abstract
The presence of selenocyanate (SeCN-) species in some specific industrial wastewater streams including those from the crude oil refineries and mining industries, pose a risk to human and animal health. The present work thus investigated the treatment of selenocyanate contaminated water using combined TiO2 photocatalysis and 2 line ferrihydrite (2LFh) adsorption system. The X-ray diffraction findings indicated the synthesized 2LFh to be in the amorphous state, whereas the Fourier transform infrared results showed several Fe- and O-based groups onto the 2LFh surface. During selenocyanate removal using the above- mentioned combined system, the TiO2 photocatalysis initiated the selenocyanate complex degradation with selenite and selenate species appearing over 360 min reaction time. This was followed by the adsorption of released selenium species onto 2LFh. Results from the respective TiO2 photocatalysis and 2LFh adsorption studies showed that the combination of the two systems through efficient, but was affected by the process control variables including pH. A complete selenium removal was noted at pH 5, whereas the selenium removal decreased significantly with an increase in the process pH. This was attributed to lower adsorption of released selenium species onto 2LFh. The response surface methodology (RSM) modeling also showed reasonable estimates for the aqueous phase selenocyanate removal under a varying set of operational conditions.