title: Regeneration of Ce(IV) in simulated spent Cr-etching solutions using an undivided cell.
abstract: This study investigated regeneration of Ce(IV) from Ce(III) oxidation at 0.05-0.5Acm(-2) in 4M HNO(3) with/without anion impurities (SO(4)(2-) (0.01-0.2M), Cl(-) (0.01-0.08M), and/or Cr(2)O(7)(2-) (0.005-0.016M)) in an undivided cell. Both Ce(IV) yield and current efficiency (CE) were significantly lower in 0.1M than in 1-4M HNO(3) and different on anode materials (in order Pt>IrO(2)/Ti>glassy carbon). The apparent rate constants for Ce(III) oxidation on the Pt anode (k(1)) and for Ce(IV) reduction on a stainless steel cathode (k(2)) were (0.40-1.80)x10(-4) and (0.08-1.01)x10(-4)s(-1), respectively, corresponding to the apparent mass transfer coefficients of (2.0-9.0)x10(-3) and (0.4-5.1)x10(-3)cms(-1), respectively. For Ce(III) oxidation at 0.3Acm(-2) in 4M HNO(3) containing multi-impurity (0.025M SO(4)(2-)+0.08M Cl(-)+0.016M Cr(2)O(7)(2-)), the k(1) was lowered by one order of magnitude although the k(2) remained unchanged, and both Ce(IV) yield and CE were reduced by approximately 89%. The decrease of Ce(IV) yield and CE by the uni-impurity was in order Cl(-)>Cr(2)O(7)(2-)>SO(4)(2-). The obtained parameters are useful to design undivided batch reactors for the Ce(IV) electro-regeneration in spent Cr-etching solutions.
authors.affiliation: Department of Environmental Engineering and Science, National Pingtung University of Science and Technology, Pingtung 91201, Taiwan. huangkL@mail.npust.edu.tw
authors.forename: Kuo-Lin
authors.initials: KL
authors.lastname: Huang
authors.forename: Te-San
authors.initials: TS
authors.lastname: Chen
authors.forename: Kuei-Jyum C
authors.initials: KJ
authors.lastname: Yeh
mesh_terms: D000838:Anions; D002586:Cesium / Q000737:chemistry*; D002621:Chemistry / Q000379:methods; D002857:Chromium / Q000737:chemistry*; D004563:Electrochemistry / Q000379:methods*; D004566:Electrodes; D017942:Nitric Acid / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D012996:Solutions; D013193:Stainless Steel; D013997:Time Factors
chemical_list: D000838:Anions; D012996:Solutions; D002857:Chromium; D013193:Stainless Steel; D002586:Cesium; D017942:Nitric Acid; D010100:Oxygen