Chemical and electrochemical considerations on the removal process of hexavalent chromium from aqueous media

摘要: Two methods were used to remove Cr(VI) from industrial wastewater. Although both are based in the same general reaction: 3Fe(II)(aq) + Cr(VI)(aq) ⇌; 3Fe(III)(aq) Cr(III)(aq) way which required amount of Fe(II) is added wastewater different for each method. In chemical method, Fe(II)(aq) supplied by dissolving FeSO4 · 7(H2O)(s) into wastewater, while electrochemical process ions formed directly solution anodic dissolution an steel electrode. After this reduction process, resulting and Fe(III)(aq) precipitated as insoluble hydroxide species, cases, changing pH (i.e., adding Ca(OH)2(s)). Based on thermodynamic characteristics systems Cr(VI)–Cr(III)–H2O–e− Fe(III)–Fe(II)–H2O–e− processes optimized. However we show that option, apart providing a better form control, generates significantly less sludge compared with process. Furthermore, it also shown ageing promotes formation soluble polynuclear species Cr(III). Therefore, recommended separate chromium iron-bearing phases once they formed. We propose optimum hydraulic conditions continuous present aqueous media treated plug-flow reactor.