The Chemistry of Perchlorate in the Environment

On the stability of perchlorate ions against reductive attacks in electrochemical systems and in the environment

“…However, evidence for the occurrence of the reduction process has been reported for Rh [1][2][3][4][5], Pt [6][7][8][9], WC [10], Al [11], Ti [12], Ir [13], Ru [14], Re [15], Tc [16], and Sn [17] electrodes. A survey of the literature can be found in recent reviews [18][19][20][21]. These observations prompt us to keep in mind the possibility of the occurrence of the reduction process at any electrode used in an aqueous acid medium containing perchlorate ions.…”

“…− [13,20,21,[61][62][63]65,67], namely the mechanism (A) involving protons and/or adsorbed hydrogen, the serial mechanism (B) and the mechanism (C) involving free-metal sites.…”

Redox potential (Eh) and anion effects of pyrite (FeS2) leaching at pH 1

“…This may be due to the beneficial effects of Cl À anion in preventing S 0 buildup or due to conversion of Cl À to ClO À 4 under highly oxidising conditions at 900 mV Eh. It is known that any conversion between these two species will occur through intermediates such as chlorate (ClO À 4 ), chlorite (ClO À 3 ) and hypochlorite (ClO À ) (Brown and Gu, 2006). For the leach experiments reported here high performance ion chromatography (HPIC) analysis of replica leach solutions failed to show presence of any intermediate Cl species (data not provided), hence this proposition is unlikely.…”

Utilization of heavy alkali dopants as a beacon to study the cathode electrolyte decomposition layer in lithium-ion batteries

“…The reduced chloride product could exist near the surface of the nLiCoO 2 particles from small water impurities in the aqueous slurry and solvent and/or trapped by the hygroscopic Li/Cs perchlorate electrolytes. Further breakdown could be initiated under acidic conditions [44]. The overall chloride signal continues to decrease with depth which is mirrored by the Cs 3d scans (Fig.…”

“…The higher energy peak arises from the Cl 2p 3/2 and 2p 1/2 core levels which represent ClO 4 − at 208.4 eV [37] and 209.2 eV [43] and perchlorate breakdown to ClO 3 − at 206.3 eV [37], with the lower energy peak splitting being closely associated with Cs/LiCl [37]. While the perchlorate ion, ClO 4 − , is among the most stable of counter ions, due to the delocalization of electron density across all four oxygen species surrounding the chloride (VII), mechanisms do exist which facilitate its breakdown with chloride reduction through activated oxygen vacancy complexes in metal centers under slightly acidic conditions [44]. The reduced chloride product could exist near the surface of the nLiCoO 2 particles from small water impurities in the aqueous slurry and solvent and/or trapped by the hygroscopic Li/Cs perchlorate electrolytes.…”