Destruction of Cyanide Wastes by Electrolytic Chlorination

Abstract

By combining the principles of the well‐known processes of alkaline chlorination and electrolytic oxidation it has been demonstrated that it is possible to obtain more effective treatment of concentrated cyanide wastes. Rock salt is added to the waste solution and hypochlorite is produced by electrolysis in the solution. Complete destruction of cyanide and destruction of most of the cyanate formed results at the rate of about 0.1 lb cyanide/kwhr. Plating metals can be recovered by cathodic deposition. During the course of the electrolysis, the discharge of cadmium ions at the cathode results in a lowering of the pH until the optimum value for cyanate oxidation is reached. Safety hazards are minimized since there is never more than a slight excess of chlorine present. A graphite anode can be used with no overvoltage problems and with a long life expectancy.

Rotating Ring‐Disk Electrode Studies of Cyanocuprous Ion Oxidation on Platinum

“…Manuscript submitted Nov. 9, 1990; revised manuscript received Feb. 20, 1991. K2 v Pi {T1, 0" 2 surface concentration of species i, mol/cm 2 reaction order of species i in reaction [9] reaction order of species i in reaction [8] diffusion layer thickness, cm dimensionless boundary condition constants dimensionless heterogeneous reaction rate constant electrolyte kinematic viscosity, cm2/s stoichiometric coefficient dimensionless velocity distribution constants intercept, cm sl/2/molm RRDE angular velocity, rad/s Packed bed electrodes are attracting increasing interest for use in electrochemical reactors (1)(2)(3)(4)(5)(6)(7). Interpretation of experimental data from these electrodes is complicated by the fact that ohmic resistance to the flow of ionic current through the electrolyte contained in the packed bed can cause significant potential drop at moderate to high current densities.…”

“…Ohm's law for this one-dimensional case takes the form i = -KOCJOx [2] where K is the effective conductivity of the electrolyte in the pores of the electrode. Differentiating and combining equations Using the dimensionless variables y = x/L and P = aaF(aP0 -Cx)/(RT), where L is the electrode thickness, the remaining constants can be combined in a parameter, "hR," called the "ohmic modulus" here hR = L x/[aioaaF/(2KRT)] exp [aaF(~Pa -r [4]…”

“…The electrochemical oxidation of cyanide can be catalyzed by the addition of ions which oxidize at less anodic potentials to form chemical oxidants in situ. Chloride is often used in this manner to generate chlorine and hypochlorite (1,(3)(4)(5). Unfortunately, the chloride concentration must be relatively high to obtain economical current efficiencies.…”

Comportamento eletroquímico de eletrodos a base de dióxido de estanho e sua aplicação na oxidação do cianeto

“…et aI [55]. sugere que a temperatura do eletrólito deve ser de 40-50 oCo Khun[45] menciona que Nagendran verificou, após medidas em várias densidades de corrente e concentrações de cloreto de sódio, que a decomposição do cianeto é proporcional à corrente até o valor de 120 mA cm-2 .…”

“…produção de hipoclorito a partir da oxidação eletroquímica de cloretos em soluções alcalinas contendo cianetos, apresenta um custo de energia elétrica e reagentes alcalinos, de cerca de 50% menor que o da cloração direta.Apesar das vantagens da geração "in situ" de CI 2 /CIO-no tratamento de resíduos contendo CN-, este processo não é efetivo para alguns complexos de cianetos metálicos, com alta estabilidade química[45,55].…”