TiO2/MSB Photocatalysis and Photo-Fenton for the Degradation of Sago Wastewater

The direct discharge of improperly treated sago effluent poses a great threat to water bodies due to the high amount of organic matter. Advanced Oxidation Processes, namely titanium dioxide (TiO2)-mediated photocatalysis and photo-Fenton have emerged as state-of-the-art treatment tools for water purification. This work investigated the efficiency of TiO2 photocatalysis and photo-Fenton treatment as possible means for the degradation of sago wastewater, particularly in removing chemical oxygen demand (COD) by employing Response Surface Methodology (RSM). In the case of TiO2 photocatalysis, sago bark (SB), a solid waste material generated from sago industry was acid treated prior to the preparation of TiO2/modified sago bark (TiO2/MSB) mixture. To prepare the TiO2/MSB mixtures, concentrations of TiO2 and MSB was varied from 0.2 g/L to 0.8 g/L and 1 w/w% to 3 w/w%, respectively. Among six TiO2/MSB mixtures, sample prepared by combining 0.2 g/L TiO2 and 1 w/w% MSB demonstrated the highest COD removal 64.92%. Given that the highest removal was produced using this mixture sample, further optimisation of sago wastewater treatment was carried out by varying the independent variables, dosage and contact time. Under optimum condition, 0.10 g of 0.2 g/L TiO2/1% MSB reduced 52.83% COD in 120 min contact time. Characterisations in term of surface morphology, functional groups, and elemental analysis supported the ability of TiO2/MSB mixture to remove COD. For photo-Fenton treatment, three operating parameters namely, initial pH, H2O2 and Fe2+ ion concentrations were fixed for optimisation. A maximum COD removal of 90.00% was obtained when sago wastewater sample was treated at pH 2.66 in the presence of 4.01 g/L of H2O2 and 5.07 g/L Fe2+ ion. Photo-Fenton treatment resulted in better COD removal compared to dark Fenton which only produced 56.25%. Despite the high COD removal, the total organic carbon (TOC) removal under the same optimised condition was considerably low, 48.00% only suggesting incomplete mineralisation of stable intermediates or degradation products present in the treatment solution. Toxicity assessment on the photo-Fenton treated sago wastewater solution revealed that the mortality of Artemia salina was less than 50%. This evidence concluded the non-toxic nature of the treated sago wastewater. The regression value (R2 >0.99) of the polynomial models for both TiO2 photocatalytic and photo-Fenton treatments indicated a high degree of correlation between the parameters evaluated. The findings obtained signify the feasibility of TiO2 photocatalysis and photo-Fenton as appealing alternative protocols for sago wastewater treatment