Cerium(III) Electrooxidation in Nitric Acid Solutions of Rare-earth Elements

Abstract

The electrochemical behavior of cerium(III) in nitric acid solutions of rare-earth elements was studied. The activation energy and reaction order of cerium(III) oxidation were determined for various levels of anodic polarization.Published data [13 6] on cerium(III) recovery from a mixture of rare-earth elements (REEs) and preparation of its pure compounds show that the method of preliminary electrochemical oxidation of Ce(III) to Ce(IV), followed by separation by precipitation or extraction, is the most promising. The comparative simplicity of separation is based on the substantial difference in the chemical properties of REE(III) and Ce(IV). The advantages of the electrochemical oxidation are the absence of chemical oxidants, possibility of preparation of stable Ce(IV) solutions, feasibility of a continuous process, higher equipment productivity, and smaller working area. However, this method has been insufficiently developed for industrial application [7]. The high yield of Ce(III) oxidation is achieved at a low current efficiency.In this study, we examined how the electrochemical oxidation of Ce(III) in nitric acid solutions depends on the current density i, Ce(III) concentration, and electrolyte stirring intensity (characterized by the Reynolds number Re). The conditions ensuring complete Ce(III) oxidation with a current efficiency exceeding 92% were determined.

Mediated electrochemical oxidation of phenol in continuous feeding mode using Ag (II) and Ce (IV) mediator ions in nitric acid: A comparative study

“…Horbez and Storck [26] have reported that for cerium oxidation in sulfuric acid medium with platinum coated titanium electrode if the operating cell voltage is above 1.1 V vs. SCE (saturated calomel electrode) then the evolution of oxygen is inevitable and occurs parallel to cerium oxidation. Considering the above fact, the activation energy reported in this work may taken to be representing the combined process of Ce (III) oxidation and oxygen evolution under the applied cell voltage of 2.5 V. The calculated activation energy is in agreement with the one reported by Wei et al [21] (16.3 kJ mol −1 ) and Sedneva [27] (32.2 kJ mol −1 ) for Ce (III) oxidation in nitric acid using cyclic voltammetric data. Also the current efficiencies were increased with increase in the temperature.…”

Cerium oxide based active catalyst for hydroxylammonium nitrate (HAN) fueled monopropellant thrusters

“…5 Based on the reported reaction of cerium ions with hydroxylamine the following redox mechanism can be assumed to play an intermediary role in deciding the extreme reactivity of these catalysed systems. [39][40][41][42][43] Ce 4+ + NH 3 OH + / Ce 3+ + 1 2 N 2 + 2H + + H 2 O…”

Electrochemical redox processes involving soluble cerium species

“…Previously, the separation of Ce(IV) from La(II) and Y(II) in nitric acid solutions was demonstrated by using polyvinyl pyridine anion exchangers for spent nuclear fuels [144]. The oxidation of Ce(III) in rare earth mixtures in nitric acid has also been investigated [200]. The possibility of taking advantage of electrochemical driven conversion and of the high solubility of cerium (and other lanthanides) in MSA in new applications deserves more research.…”