“Physicochemical processing of low grade ferruginous manganese ores”

•Leaching studies have been carried out to selectively leach out the Fe from ferruginous Mn Ores.•Ferrous oxalate dihydrate of > 75% purity was recovered using 1 molarity solution of oxalic acid at 60O C treatment for 2 hours.•The proposed process can recover 12-25% iron oxalate and 33 to 50 % ore concentrate for manganese ferroalloy.•Ore concentrate (Mn: 42-55 %, Mn/Fe: 2.91-4.5) can be recovered from the low grade ores.

This study is focused on the develop of a cost effective physicochemical beneficiation process for low grade ferruginous manganese ores to recover a valuable iron bearing by-product (Fe Oxalate or Mn Ferrite) and manganese ore concentrate. It was found the one molarity solution of oxalic acid can leach five times more Fe than Mn from ferruginous manganese ores during treatment at temperature 333 K for 2 h. Photoreduction of the leached solution with sunlight for four hours provided ferrous oxalate dihydrate of > 75 % purity which was further converted into Mn ferrite by roasting it at 773 K for 4 h. Residue samples were roasted in a controlled atmosphere tubular furnace (temperature: 573 - 973 K; time: 1, 3, 5 h) and muffle furnace (temperature: 523- 773 K; time: 2, 4, 12 h) to study the formation of maghemite coating on the surface of iron bearing particles. Chemical analysis, XRD, SEM, magnetometer tests were carried out to characterize the products recovered at different stages of the process. Davis tube magnetic separation tests were conducted using different current intensity (0.5, 1, 2 A) to establish grade and yield of the ore concentrate. The proposed process can recover 0.12-0.25 tons of iron oxalate and 0.33-0.50 tons of manganese ore concentrate (Mn: 42-55 % and Mn/Fe: 2.91-4.5) by processing of one ton of low grade ferruginous manganese ore (Mn: 19.3-31.3 % and Mn/Fe: 0.48-1.16).

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