Combined treatment based on synergism between hydrodynamic cavitation and H2O2 for degradation of cyanide in effluents

Abstract

The main purpose of this research has been to evaluate and optimize the application of hydrodynamic cavitation (HC), combined with hydrogen peroxide, as a promising process for the effective degradation of cyanide in aqueous effluents. The experimental work was carried out using cavitation equipment with a venturi device connected to a tubular circuit which allowed a closed-cycle flow to run for 120 min, in which the effect of control parameters as inlet pressure, H2O2:CN─ ratio, pH, and temperature have been evaluated for the treatment of solutions with initial cyanide concentration in range 100 to 550 mg L─1.The results showed that in optimal conditions cyanide degradation using only HC reached 70% and, using solely H2O2 as oxidizing agent it reached 63%. Efficiency of the combined treatment process was evaluated on the basis of their synergetic effect as it turned out to be more effective showing a 99.9 % cyanide degradation in less than 120 min. The optimum set of conditions that produced the highest degradation rate and efficiency was: inlet pressure 4 bar; pH 9.5; and H2O2:CN─ ratio = 1.5:1. The process was also evaluated on the basis of cavitational yield and in terms of energy and chemical treatment costs. The results have demonstrated that the combined treatment technology of HC + H2O2 can be effectively used as a fast and highly efficient treatment of wastewater containing cyanide.