Novel approaches based on hydrodynamic cavitation for treatment of wastewater containing potassium thiocyanate

Significant development in the industrial technologies and applications based on the use of cyanide derivatives has also led to significant environmental problems critically needing research in developing new technologies for effluent treatment. Present study investigates the use of novel treatment approach of hydrodynamic cavitation (HC) combined with chemical oxidation and catalyst for the degradation of Potassium Thiocyante (KSCN) for the first time. The effect of operating pressure (over the range of 2-5 bar) and initial pH (over the range of 2-7.1) on the degradation has been studied initially. Effect of combination of HC with H₂O₂ (varying KSCN:H₂O₂ ratios as 1:0.5-1:3), HC + O₃ (varying ozone mass flow rate over the range of 200-400 mg/h), HC + O₃ + catalyst (TiO₂/ZnO/CuO at fixed loading of 0.1 g/L at optimized ozone flow rate) as process intensifying approaches on the KSCN degradation has also been studied. Combination of HC + O₃ + CuO at different loadings of CuO has also been investigated. Use of combination of HC with H₂O₂ and HC with Ozone resulted in extent of KSCN degradation as 73% and 71.1% respectively. Among the different combinations of HC + O₃ + Catalysts (TiO₂/ZnO/CuO), HC + O₃ + CuO (at loading of 0.15 g/l) resulted in highest KSCN degradation as 86.5%. Combination of HC + H₂O₂ + O₃ + CuO was established to be the best approach yielding complete degradation with synergistic index of 2.98 and 92.9% as the COD removal. The study also focused on establishing kinetic rate constants which revealed that all the approaches followed first order mechanism with higher rate constants for the combination approaches as compared to individual approach. Overall, it has been conclusively established that hydrodynamic cavitation based combined treatment schemes are very effective for the treatment of biorefractory wastewaters containing cyanide derivatives.