Performance of Continuous heterogeneous Fenton-type and hydrodynamic cavitation reactors in series

S. NAPOLEONE; G. SALIERNO; M. MAISTERRENA; M. PELLASIO; L. I. DOUMIC; M.A. AYUDE; M. C. CASSANELLO

Nápoles

Conferencia; 15th International Conference On Chemical And Process Engineering (ICHEAP 15); 2021

AIDIC

Extensive studies have been conducted on heterogeneous Fenton-type advanced oxidation processes to remove pollutants from wastewaters during the last years; however, most works were mainly carried out in batch reactors1. Due to large volumes of effluents, treatment processes generally need to be continuous, requiring stable catalysts, hydrogen peroxide efficient consumption, and fast conversion. The continuous heterogeneous Fenton type (CHFT) process performed in a fixed bed reactor allows the treatment of large volumes of wastewaters with straightforward separation and recovery of the catalyst. Prussian blue nanoparticles supported on alumina (PBNP/γ-Al2O3) demonstrated to be a suitable catalyst for the peroxidation of Orange G (OG) in batch2. Besides, the use of hydrodynamic cavitation (HC) is recognized as a cost-effective strategy to intensify HFT processes3,4. In this research, the performance of the CHFT oxidation of OG in an up-flow fixed bed reactor formed by 20g of PBNP supported on γ-Al2O3 spheres is investigated. For certain conditions, the CHFT collected outlet is subjected to HC; alternatively, the HC reactor is connected directly to operate in series in continuous mode. The HC reactor, procured from Vivira Process Technology Ltd. (India), was operated at 50°C and 3.5 bar pressure. The influence of the flow rate, oxidant concentration, and fixed bed reactor temperature was examined. The dye and oxidant concentrations at the CHFT reactor outlet were determined every 20 minutes for at least one hour. Steady-state was generally attained after 10-20 minutes. The residual total organic carbon (TOC) was determined periodically every 60 minutes during the 5-7 h continuous runs, whereas, the distribution of organic acids formed was assessed after 5 h. Total iron concentration in the outlet was measured to quantify the extent of iron leaching. Results were compared to those attained using CHFT or HC alone. For given operating conditions, the fixed bed reactor outlet stream was collected in a reservoir covered from light, to analyze if the reaction continues in the tank and to compare with the results of using the fixed bed and the HC reactor in series.An increase in oxidant concentration and/or temperature promoted OG conversion at the outlet of the fixed bed reactor. An increase in temperature in the fixed bed reactor enhanced the efficiency ofoxidant consumption. Iron leaching was generally low, representing an hourly loss of around 0.1 -0.2% of the iron load. The flow rate significantly affects the output of the in-series of reactors system. When both reactors operate in series, complete discoloration is attained faster at the higher flow rate despite the lower residence time. A high residence time in the CHFT reactor apparently leads to high conversion of the oxidant decreasing the relative influence of cavitation. Therefore, there would be a liquid flow rate that optimizes the efficiency in consumption of hydrogen peroxide leading to fast discoloration and higher TOC removal for the continuous in series operation.A comprehensive model is proposed and employed to interpret the experimental trends attained in the continuous reactor system.