The present work deals with the optimization of basic fuchsin dye removal from an aqueous solution using the ultraviolet UV/H2O2 process. Response Surface Modeling (RSM) based on Box-Behnken experimental design (BBD) was applied as a tool for the optimization of operating conditions such as initial dye concentration (10-50 ppm), hydrogen peroxide dosage (H2O2) (10-20 mM/L) and irradiation time (60-180 min), at pH = 7.4 under ultra-violet irradiation (254 nm and 25 W intensity). Chemical oxygen demand (COD abatement) was used as a response variable. The Box-Behnken Design can be employed to develop a mathematical model for predicting UV/H2O2 performance for COD abatement. COD abatement is sensitive to the concentration of hydrogen peroxide and irradiation time. Statistical analyses indicate a high correlation between observed and predicted values (R2 > 0.98). In the BBD predictions, the optimal conditions in the UV/H2O2 process for removing 99.3% of COD were found to be low levels of pollutant concentration (10 ppm), a high concentration of hydrogen peroxide dosage (20 mM/L), and an irradiation time of 80 min.

Wastewater decontamination in pharmaceuticals is crucial to prevent environmental and health risks from API residues and other contaminants. Advanced oxidation processes (AOPs) combined with cavitational treatments offer effective solutions. Challenges include designing reactors on a large scale and monitoring the effectiveness and synergies of the hybrid technology. In the present work, pilot-scale treatment of a real high COD (485 g/L) pharmaceutical wastewater (PW) was investigated using hydrodynamic cavitation (HC) operated individually at 330 L/h or in combination with oxidants and electrical discharge (ED) with cold plasma (15 kV and 48 kHz). The first approach consisted of PW cavitational treatment alone of 7 L of 1:100 diluted PW at a HC-induced pressure of 60 bar and a flow rate of 330 L/h. However, this strategy did not provide satisfactory results for COD (∼15% less), and only when HC treatment was extended to more than 30 min in a recirculation mode, encouraging results were obtained (∼45% COD reduction). Consequently, a hybrid approach combining HC with ED-cold plasma was chosen to treat this high-COD PW. Aiming to establish an efficient flow-through hybrid process, after optimising all cavitation and electrical discharge parameters (45 bar HC pressure and 10 kHz ED frequency), the best COD abatement of ∼50 % was recorded with a 1:50 diluted PW. However, a subsequent adsorption step over activated carbon was required to achieve an almost quantitative COD reduction (95%+). Our integrated physicochemical process proved to be extremely efficient in treating high-COD industrial wastewater and resulted in a remarkable reduction of the COD value. In addition, the residual surfactants content in the PW were also drastically reduced (98%+) when a small amount of oxidants was added in the hybrid HC/ED treatment.