TY - GEN
T1 - Ambient temperature precipitation of heavy metal ions from aqueous solutions as ferrite-type compounds
AU - Perez, Oscar Perales
AU - Tohji, Kazuyuki
AU - Kasuya, Atsuo
AU - Umetsu, Yoshiaki
PY - 2000/12/1
Y1 - 2000/12/1
N2 - The removal of iron and various heavy-metal ions by their incorporation into stable ferrite-type precipitates at 25°C is a promising alternative to clean up large volumes of polluted aqueous effluents. Our research work investigated the conditions to produce magnetite and various M-bearing ferrites (where M: Zn, Cu, Co, Ni, Cd, etc...) directly from aqueous solutions at 25°C by simultaneous control of the oxidizing conditions and pH. The formation of the solids was followed by monitoring the oxidation-reduction potential (ORP) and rate of proton release during the aerial oxidation of the suspensions at constant pH (contact stage). Only mildly oxidizing conditions, represented by ORP values between -110 mV and -150 mV and a moderate oxidation rate of Fe(II) species were conducive to well-crystallized ferrites at ambient temperature. It was also found that increasing the Fe/M mole ratio in starting solutions enhanced the stability of the M-bearing ferrites at ambient temperature. When the formation of the ferrite was incomplete, aging of the sludges in their mother liquors at 25°C promoted the crystallinity of the precipitates. The mentioned conditions favored the suitable progress of the ferrite-forming reaction involving the oxidation of Fe(II) entities, subsequent hydrolysis of produced Fe(III) species and de-hydration of the intermediate. Furthermore, the ferrite formation at low temperature permits the elimination of iron and co-existing heavy metal ions to sufficiently concentration. In turn, the characterization of the precipitates evidenced their magnetic nature (room-temperature saturation magnetization above 60 emu/g) as well as the effective incorporation of target metal ions into the ferrite structure.
AB - The removal of iron and various heavy-metal ions by their incorporation into stable ferrite-type precipitates at 25°C is a promising alternative to clean up large volumes of polluted aqueous effluents. Our research work investigated the conditions to produce magnetite and various M-bearing ferrites (where M: Zn, Cu, Co, Ni, Cd, etc...) directly from aqueous solutions at 25°C by simultaneous control of the oxidizing conditions and pH. The formation of the solids was followed by monitoring the oxidation-reduction potential (ORP) and rate of proton release during the aerial oxidation of the suspensions at constant pH (contact stage). Only mildly oxidizing conditions, represented by ORP values between -110 mV and -150 mV and a moderate oxidation rate of Fe(II) species were conducive to well-crystallized ferrites at ambient temperature. It was also found that increasing the Fe/M mole ratio in starting solutions enhanced the stability of the M-bearing ferrites at ambient temperature. When the formation of the ferrite was incomplete, aging of the sludges in their mother liquors at 25°C promoted the crystallinity of the precipitates. The mentioned conditions favored the suitable progress of the ferrite-forming reaction involving the oxidation of Fe(II) entities, subsequent hydrolysis of produced Fe(III) species and de-hydration of the intermediate. Furthermore, the ferrite formation at low temperature permits the elimination of iron and co-existing heavy metal ions to sufficiently concentration. In turn, the characterization of the precipitates evidenced their magnetic nature (room-temperature saturation magnetization above 60 emu/g) as well as the effective incorporation of target metal ions into the ferrite structure.
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M3 - Conference contribution
AN - SCOPUS:0034592568
SN - 087339495X
T3 - Proceedings of the Second International Conference on Processing Materials for Properties
SP - 985
EP - 988
BT - Proceedings of the Second International Conference on Processing Materials for Properties
A2 - Mishra, B.
A2 - Yamauchi, C,
A2 - Mishra, B.
A2 - Yamauchi, C.
T2 - Proceedings of the Second International Conference on Processing Materials for Properties
Y2 - 5 November 2000 through 8 November 2000
ER -