TY - JOUR
T1 - Determination of iron and chromium fluorides solubility for the treatment of wastes from stainless steel mills
AU - Gálvez, José L.
AU - Dufour, Javier
AU - Negro, Carlos
AU - López-Mateos, Federico
PY - 2008/3/1
Y1 - 2008/3/1
N2 - Stainless steel pickling waste bath is one of the most important environmental problems in stainless steel mills because of its high toxicity and economic losses due to conventional neutralization treatment of this waste. Nitric and hydrofluoric acids reclamation solves only a part of the problem while metals still are considered as a waste and the whole content of hydrofluoric acid is not recovered because fluoride forms very stable complexes with metals. In this work metal-fluoride complexes solubility is determined in order to design a process for metals recovery, consisting of separating iron and chromium, precipitated as K2FeF5(s) and CrF3(s), from nickel that remains in solution. Iron and chromium would be further hydrolyzed for oxides recovery, while fluoride release to solution and is recycled to selective precipitation stage. Results are obtained by the application of a novel equilibrium model for spent pickling liquors (SPL) called in this work "UCM-Model". Its applicability is evaluated by comparison with other literature models and it is used in the determination of thermodynamic solubility products. Obtained values are Ks, K2FeF5(s) = exp(-4.1 ± 0.5 - (1400 ± 200)/T (K)) and Ks, CrF3(s) = exp(-7.8 ± 1.0 - (5800 ± 500)/T (K)).
AB - Stainless steel pickling waste bath is one of the most important environmental problems in stainless steel mills because of its high toxicity and economic losses due to conventional neutralization treatment of this waste. Nitric and hydrofluoric acids reclamation solves only a part of the problem while metals still are considered as a waste and the whole content of hydrofluoric acid is not recovered because fluoride forms very stable complexes with metals. In this work metal-fluoride complexes solubility is determined in order to design a process for metals recovery, consisting of separating iron and chromium, precipitated as K2FeF5(s) and CrF3(s), from nickel that remains in solution. Iron and chromium would be further hydrolyzed for oxides recovery, while fluoride release to solution and is recycled to selective precipitation stage. Results are obtained by the application of a novel equilibrium model for spent pickling liquors (SPL) called in this work "UCM-Model". Its applicability is evaluated by comparison with other literature models and it is used in the determination of thermodynamic solubility products. Obtained values are Ks, K2FeF5(s) = exp(-4.1 ± 0.5 - (1400 ± 200)/T (K)) and Ks, CrF3(s) = exp(-7.8 ± 1.0 - (5800 ± 500)/T (K)).
KW - Chromium
KW - Iron
KW - Solid fluorides
KW - Solubility
KW - Spent pickling liquor
KW - Stainless steel
UR - https://www.scopus.com/pages/publications/38649094842
U2 - 10.1016/j.cej.2007.03.014
DO - 10.1016/j.cej.2007.03.014
M3 - Article
AN - SCOPUS:38649094842
SN - 1385-8947
VL - 136
SP - 116
EP - 125
JO - Chemical Engineering Journal
JF - Chemical Engineering Journal
IS - 2-3
ER -