Improving zinc electrodeposition in ammoniacal electrolytes with the saturated dissolved methyltrioctylammonium chloride

The effect of saturated dissolved methyltrioctylammonium chloride (TOAC) in ammoniacal electrolytes on zinc electrodeposition was investigated in a membrane electrolytic cell. Furthermore, cationic surfactant cetyltrimethylammonium bromide (CTAB), nonionic surfactant polyethylene glycol (PEG) and anionic surfactant sodium dodecylsulphate (SDS) are respectively added into the electrolytes with saturated TOAC to explore the combined effect of two organic additives on zinc deposits. The addition of hydrophobic TOAC can not only completely inhibit the formation of mossy zinc but also refine the grain size. The current efficiency (CE) exceeds 96%, indicating that the TOAC does not deteriorate zinc electrodeposition process. The inhibition mechanism of TOAC on mossy zinc deposits was revealed by cyclic voltammetry, cathodic polarization and Tafel tests. When adding CTAB and PEG into the electrolytes with saturated TOAC, a synergistic effect on improving the smoothness of zinc deposits can be observed, whereas the presence of SDS will weaken the inhibition effect of TOAC on mossy zinc. Therefore, the saturated dissolved TOAC in the electrolytes does not need to be removed before electrodeposition. These results are helpful for zinc recovery from the non-traditional resources.