Kinetics of pressure leaching of niobium ore by sulfuric acid

Niobium and tantalum recovery from the primary source and from tin slag, an industrial challenge: A review

“…[ 1 ] Moreover, studies have reported the possibility of applying diluted H 2 SO 4 to Nb extraction. [ 7,11,35 ]…”

Valuable Metals—Recovery Processes, Current Trends, and Recycling Strategies

“…[161] Three methods are applicable Fort he extraction of niobium metal:1 )fused-salt electrolysis of K 2 [NbOF 5 ]/NaCl, 2) by reduction with sodium, and 3) by an aluminothermic process. [159] Further processes are,f or example,p ressure digestion with sulfuric acid (10 mol L À1 ,98% Nb yield), [163] as well as roasting at 400 8 8Cin the presence of KOHa nd subsequent water leaching (98 % Nb yield). It is carried out by aluminothermic processing of Fe 2 O 3 and Nb 2 O 5 with aluminum.…”

“…Ap romising approach is the chlorination and subsequent fractional distillation of NbCl 5 and TaCl 5 . [159] Further processes are,f or example,p ressure digestion with sulfuric acid (10 mol L À1 ,98% Nb yield), [163] as well as roasting at 400 8 8Cin the presence of KOHa nd subsequent water leaching (98 % Nb yield). [164] Despite the higher Nb yield, both methods have significant drawbacks,which up to now have prevented them from replacing the H 2 SO 4 /HF digestion process.The pressure digestion with sulfuric acid is hardly justifiable economically and the roasting process consumes prohibitively high amounts of KOH.…”

Wertmetalle – Gewinnungsverfahren, aktuelle Trends und Recyclingstrategien

“…Von diesen stellt die Chlorierung und anschließende fraktionierende Destillation von NbCl 5 und TaCl 5 ein wichtiges Verfahren dar . Weitere Ansätze umfassen unter anderem den Druckaufschluss mit 10 m Schwefelsäure (98 % Nb‐Aufschlussrate) sowie einen Röstprozess bei 400 °C in Gegenwart von KOH mit anschließender wässriger Laugung (95 % Nb‐Aufschlussrate) . Beide Verfahren weisen jedoch erhebliche Nachteile auf, die einer Verdrängung des H 2 SO 4 /HF‐Aufschlusses trotz höherer Laugungsraten bisher entgegenstehen.…”