A new process for degradation of Auramine O dye and heat generation based on orifice plate hydrodynamic cavitation (HC): Parameter optimization and performance analyses

Hydrodynamic cavitation (HC) is not only a promising wastewater treatment technology but also an efficient heat generation method. In this work, the HC degradation of several organic dyes was carried out and the related heat generation was studied. The effects of geometrical parameters (orifice angles (α = 0 ° and± 45 °) and orifice numbers (n = 3–9)) and experimental parameters (2.0–4.0 bar pressures, 30–60 °C temperatures and 5.0–15 mg/L concentrations) on Auramine O degradation and heat generation in orifice plate HC system are investigated. TOC analysis is performed to determine the mineralization degree of Auramine O solution. The generated intermediates are detected by LC-MS. In addition, the produced free radicals in HC process are identified by adding some trapping agents. The results showed that the HC technology has high mineralization and strong heat generation abilities in degradation processes of organic pollutants. For 6-orifice plate, 4.0 bar pressure, 5.0 L solution volume and 10 mg/L concentration, 81.39% degradation ratio of AO was achieved at 90 min cycle moment. And that, 1082.52 kJ heat energy with 40.09% thermal efficiency was obtained during 30 min cycle time. Perhaps, this work may provide a new strategy for simultaneous large-scale organic wastewater treatment and effective heat production recycle.