Optimisation of a photocatalytic water treatment using response surface methodology and quality by design Approach

Many water treatment methods have been developed to remove organic pollutants from contaminated waters. Their efficiency is usually assessed by removal measurements, and the effect of operational factors on the process is rarely explored. To bridge this gap, an experimental design methodology has been applied to optimise an advanced oxidation process combining adsorption and photocatalysis, using AZURAD (R) software. This approach was applied to the removal of carbamazepine (CBZ) in aqueous solution by a bio-sourced activated carbon and TiO2 composite material under light exposure. Two experimental designs were performed considering three quantitative factors (pH, catalyst dose and temperature) and one qualitative factor (dissolved oxygen concentration). From the response surface methodology (RSM), the optimised operational factors for CBZ adsorption and degradation were independently determined. Using desirability function approach, commonly optimised conditions for both processes were assessed with a catalyst dose of 0.13 g.L-1, oxygen saturated medium and either pH = 9.5 and T = 40 degrees C or pH = 7.8 and T = 10 degrees C. The Quality by Design approach showed that the experimental conditions could vary maintaining the adsorption and photocatalysis process removal efficiency (with more than 70% and 80%, respectively) with a high probability of 80%. This highlights the robustness of the treatment process and its potential upscaling.