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Formation of needle‐like lepidocrocite fine particles by oxidation of an aqueous suspension of ferrous hydroxide in a bubble column
Author(s) -
Cho HaeMan,
Kawasaki Hiroyuki,
Kumazawa Hidehiro
Publication year - 2000
Publication title -
the canadian journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.404
H-Index - 67
eISSN - 1939-019X
pISSN - 0008-4034
DOI - 10.1002/cjce.5450780429
Subject(s) - lepidocrocite , ferrous , aqueous solution , chemistry , sodium hydroxide , oxygen , hydroxide , particle size , bubble , particle (ecology) , inorganic chemistry , analytical chemistry (journal) , chromatography , organic chemistry , goethite , geology , oceanography , adsorption , parallel computing , computer science
Fine particles of needle‐like lepidocrocite (γ‐FeOOH) were synthesized by the oxidation of aqueous suspensions of ferrous hydroxide using a bubble column with draft tube at a constant temperature ranging from 20°C to 30°C. The oxidation steps leading to green rust (an intermediate) and lepidocrocite (final product), termed Step I and II, respectively, could be described apparently as first order, with respect to oxygen, and zero order, with respect to total ferrous species. When the concentration of oxygen in the feed stream was varied under a constant gas velocity, the mean size based on the major axis of needle‐like particle decreased from 0.60 to 0.35 μm with increasing oxidation rate. When the gas velocity was varied under a constant oxygen concentration, the particle size was almost independent of the oxidation rate and was equal to ca. 0.6 μm. By the addition of a small amount of sodium dihydrogenphosphate (NaH 2 PO 4 ), the major axis could be reduced to 0.2 μm with the minor axis and the oxidation rate almost unchanged.