Determination of stannous chloride and stannic bromide speciation in concentrated Cl- and Br- media by cyclic voltammetry

Abstract

The speciation of Sn(N)-Br- and Sn(II)-Cl- in concentrated Br and Cr media were investigated by cyclic voltammetry, which is the continuous study from the previously reported Sn(II)-Br- speciation Park and Chang (2016). We first determined the speciation of Sn(IV)-Br- in concentrated Br- acidic aqueous solutions with ionic strength of 6. SnBrj4-j complexes with 1 5 and their corresponding fractional diagrams were determined based on their estimated stability constants, iln(IV) Br-. In acidic aqueous solutions where the concentration of Br- was less than 2 M, both SnBr3+ and SnBr22+ were estimated to be the main Sn(IV)-Br- species. Meanwhile, as the Br- concentration increased ˃2 M, the fraction of SnBr5- was significantly increased and became the main species among Sn(IV)-Br- complexes. For the Sn(II)-Cl- speciation, SnClk2-k complexes with 1 ˂= k ˂= 7 were determined as the concentration of Cl- increased to 6 M in acidic aqueous solutions. The fractional diagrams of SnClk2-k complexes were obtained from the estimated beta(sn(II)-Cl-)(k). Based on the fractions of Sn(11)-Cl- species, SnCl+ was the main species as the concentration of Cl- was less than 1 M. As the Cl- concentration increased from 1 to 6 M, SnCl75- became dominant among Sn(II)-Cl- complexes. We tried to determine the speciation of Sn(IV)-Cl- by cyclic voltammetry. However, the determination of Sn(IV)-Cl- speciation was experimentally limited because of the potential inversion of electrochemical reduction between Sn(IV)-Cl- /Sn(II)-Cl- and Sn(II)-Cl-/Sn.