DEGRADATION OF ORGANIC POLLUTANTS IN FLOCCULATED LIQUID DIGESTATE USING PHOTOCATALYTIC TITANATE NANOFIBERS: MECHANISM AND RESPONSE SURFACE OPTIMIZATION

Abstract

<List> <ListItem> <ItemContent> ● Titanate NFs were synthesized and photodegraded liquid digestate for the first time. </ItemContent> </ListItem> <ListItem> <ItemContent> ● The long titanate NFs (bandgap of 3.16 eV) have a high VFA removal rate of 72.9%. </ItemContent> </ListItem> <ListItem> <ItemContent> ● RSM has been used to optimize the VFA, COD, and color removal rate. </ItemContent> </ListItem> <ListItem> <ItemContent> ● The quadratic model and the effects of photocatalytic dosage were significant. </ItemContent> </ListItem> </List> Titanate nanofibers (TNFs) were synthesized using a hydrothermal method and were employed for the first time in this study to photocatalytically degrade organic pollutants found in flocculated liquid digestate of poultry litter. The photocatalytic performance of TNFs, with a bandgap of 3.16 eV, was tested based on degradation of organic pollutants and removal of color. Five combinations of pollutant concentration and pH were examined (0.2 to 1.3 g·L⁻¹ at pH 4 to 10). Central composite design (CCD) and response surface methodology (RSM) were applied in order to optimize the removal rates of volatile fatty acids (VFA) and chemical oxygen demand (COD), and the decolorization rate. There were no significant differences between the regression models generated by the CCD/RSM and the experimental data. It was found that the optimal values for pH, dosage, VFA removal rate, COD removal rate and decolorization rate were 6.752, 0.767 g·L⁻¹, 72.9%, 59.1% and 66.8%, respectively. These findings indicates that photocatalytic TNFs have potential for the posttreatment of anaerobic digestion effluent, as well as other types of wastewater.