Ferrate(VI) Oxidation of Aqueous Cyanide

Abstract

The rates of oxidation of cyanide with Fe(VI) were measured as a function of pH (8.0-12) and temperature (15-30 °C). The reaction was found to be first order for each reactant. The rates decrease with increasing pH. The energy of activation was found to be 38.9 ( 1.0 kJ mol -1 at pH 9.0. The removal of cyanide by oxidation with Fe-(VI) was studied at pH 7.5, 9.0, and 12.0. Fe(VI) removal efficiency was greater at pH 9.0 than at pH 7.5 and 12.0. At pH 9.0, Fe(VI) molar consumption was nearly equal to that of oxidized cyanide. Cyanate and nitrite ions were identified as the products of the reaction at pH 7.5. The experiments indicated 1:1 stoichiometric conversion of cyanide to nitrite ion at pH 9.0 and 12.0. Experiments were conducted to test the Fe(VI) removal efficiency of cyanide in electroplating rinsewater. The results indicate that Fe(VI) has the potential to serve as a reliable and safe oxidative treatment for removing cyanide in wastewater effluent.

Ferrate(VI) in the Treatment of Wastewaters: A New Generation Green Chemical

“…demonstrated to be one electron process whereas, the oxy compounds of arsenic, selenium, nitrogen and sulphur are possessed with the two-electron mechanism while these are reacted/degraded with Fe(VI). The reactions of ferrate(VI) with a series of inorganic compounds such as iodide, cyanide, superoxide, sulfide, hydrazine, ammonia, azide and oxy-compounds of nitrogen, sulphur, selenium and arsenite possessed with seconds-order kinetics [38,47,49,51,[57][58][59][60][61][62][63][64][65]. In general, similar to the organic compounds the reaction with inorganic compounds (P) may be demonstrated as equation (26): where k P is the second-order rate constant for the reaction.…”

Cyanide oxidation by singlet oxygen generated via reaction between H 2 O 2 from cathodic reduction and OCl − from anodic oxidation

“…However, these processes could generate highly concentrated products in which toxic cyanides still exist, which need additional treatments. Recently into less harmful products via oxidation methods have been reported, which include ozonation [6], electrochemical oxidation [7], photocatalysis [8], ferrate oxidation [9], wet oxidation [10] and alkaline chlorination [11]. Among them, alkaline chlorination is a practical method due to its low operation cost and stable treatment effect.…”

Enhanced destruction of Cu(CN)32− by H2O2 under alkaline conditions in the presence of EDTA/pyrophosphate

“…However, these processes could generate highly concentrated products in which toxic cyanides still exist, which need additional treatments. By contrast, cyanides could be directly converted into less harmful products by employing oxidation methods, such as ozonation [7], electrochemical oxidation [8,9], photocatalysis [10,11], ferrate oxidation [12,13] and wet oxidation [14]. The most practical method was thought to be alkaline chlorination, but it has many disadvantages such as formation of toxic cyanogens chloride [15] and chloride disinfection by-products [16].…”