MATERIALS

FIELD OF THE INVENTION [0001] The present invention relates to a method for treating manganese-containing

materials, such as oxides, carbonates, and ores by utilizing an ammonia gas. The invention is well suited to treating polymetallic manganese-containing nodules recovered by undersea mining, and particularly to methods for recovering valuable constituents from such nodules, especially manganese, cobalt, nickel, copper, and iron. BACKGROUND OF THE INVENTION [0002] Polymetallic or manganese nodules, are rock concretions formed of concentric layers of iron and manganese hydroxides around a core. [0003] Seafloor nodules on the ocean floor include manganese (Mn) in their composition, and usually contain Ni, Co, Cu, Zn, and Fe, with minor amounts of titanium, vanadium,

molybdenum, and cerium. Often present in addition are one or more of the following metals: magnesium, aluminum, calcium, cadmium, potassium, sodium, zirconium, titanium, lead, phosphorus, and barium. Deep sea nodules generally contain about 28% Mn, about 10% FeO, about 1 % Cu, and about 1.2% Ni.

[0004] Most of the desired valuable metals in manganese nodules are tied up with insoluble oxidized manganese, such as Mn0 ₂ . Less than 10% of the manganese contained in the nodules is acid soluble. Thus it is necessary to reduce the Mn0 ₂ by a suitable reducing agent as a first step in order to recover the metal constituents. Historically, S0 ₂ has been used for this purpose, and carbon monoxide (CO) has been used in copper recovery processes.

However such prior art processes often do not recover a suitable manganese product and are capable of recovering only from about 80 to about 92% of the primary metal values, and often produce large quantities of waste, which may include metal components that are not completely removed. SUMMARY OF THE INVENTION [0005] Manganese-containing material treated by the invention can include not only ores or deepsea nodules, but also manganese oxide bearing batteries such as zinc-carbon, alkaline, and lithium (LMO or LiMn ₂ 0 ₄ ) batteries, or other manganese-containing minerals or materials in any form. [0006] The present invention is a process for recovering manganese, and if present, other metal values ("pay metals") from seafloor manganese containing material including deep sea manganese nodules by treating manganese-containing material with ammonia. Gaseous NH ₃ reacts with the ore

7Mn0 ₂ (s) + 2NH ₃ (g) -> 7MnO (s) + 3H ₂ 0 (1) + 2N0 ₂ (g)

liberating the trapped desired valuable metals. One ton of NH ₃ is more effective than 8 tons of S0 ₂ . [0007] After reduction of the Mn0 ₂ with ammonia gas, any mineral acid can be used to leach and recover the manganese and other metals from the starting manganese-containing materials. Nitric acid is the preferred leach material, because some nitric is formed in the ammonia reaction from the H ₂ 0 and N0 ₂ . [0008] The present invention is particularly useful for making nitrate products, such as explosives, fertilizer or other nitrates. OBJECTS OF THE INVENTION [0009] The principal object of the present invention is to provide an improved method of recovering manganese from manganese-bearing materials, including from seafloor manganese nodules. [0010] Another object of the invention is to provide an effective method for recovering metal values from manganese-bearing materials, including, if present, any nickel, cobalt, copper, magnesium, aluminum, iron, calcium, cadmium, potassium, sodium, zirconium, titanium, zinc, lead, cerium, molybdenum, phosphorus, barium, and vanadium. [0011] Another object of the invention is to provide an effective method of recovering other metal values from seafloor manganese-containing materials, including deepsea manganese nodules. [0012] Another object of the invention is to produce nitrate products. BRIEF DESCRIPTION OF THE DRAWING [0013] The foregoing and other objects will become more readily apparent by referring to the following detailed description and the appended drawing, in which: [0014] The single figure is a diagrammatic flowsheet of a preferred embodiment of the invented process. DETAILED DESCRIPTION [0015] Referring now to the Figure, the process begins with manganese-containing materials 10 such as deepsea manganese nodules, which may be obtained from an ocean, sea, or other body of water. Sometimes such nodules are found in large lakes. The deepsea nodules contain in excess of 20 percent manganese, usually about 28 percent. [0016] In addition to manganese, such deepsea nodules may contain at least one of the following metals: nickel, cobalt, copper, magnesium, aluminum, iron, calcium, cadmium, potassium, sodium, zirconium, titanium, zinc, cerium, molybdenum, phosphorus, barium, lead, and vanadium. The invented process includes the efficient leaching and recovery of many of these metal values. [0017] Optionally, the nodules, or other manganese-containing materials, are crushed or ground to increase the surface area for the later reactions. Advantageously, any chlorides in the nodules are removed by any convenient method, such as washing, preferably with water. This step may be done before, during or after any crushing but preferably after. [0018] The nodules are reacted at elevated temperature with ammonia at 12. Gaseous NH ₃ reacts with the manganese oxide ore according to the following equation:

7Mn0 ₂ + 2NH ₃ -> 7MnO + 3H ₂ 0 + 2N0 ₂ [0019] The NH ₃ reacts with Mn0 ₂ to form MnO, water, and N0 ₂ , and to release the other metals from the nodules at step 14. The N0 ₂ can be removed as a gas or reacted to form nitric acid. [0020] After reduction of the Mn0 ₂ with ammonia, any mineral acid can be used in the leach step 16 to leach and recover the manganese and other metal salts 18 from the starting manganese-containing materials. Nitric acid is the preferred leach material, because some nitric is formed in the ammonia reaction. [0021] Pay metals are precipitated and recovered at 20 from metal salts formed in the leaching step. Following the leach, the pH of the solution is then changed to about 2.2 - 2.3 to precipitate hydrated iron oxide (FeOOFT H ₂ 0). The precipitated iron values are removed by filtration of the solution. This pH change may be achieved in various ways, including the addition to the solution of ammonia or alkaline earth hydroxides, such as Mg(OH) ₂ or Ca(OH) ₂ , alkaline earth oxides such as MgO or CaO, or alkaline earth carbonates such as Mg(C0 ₃ ) ₂ or Ca(C0 ₃ ) ₂ . [0022] Any copper, lead, cadmium, and zinc present in the solution is also removed therefrom. Once in solution the metal values may be precipitated as oxides or sulfides.

Preferably, the solution is adjusted to a low pH, hydrogen sulfide (H ₂ S) or NaHS is introduced into the solution to precipitate as sulfides any copper, lead, cadmium, and zinc which is present in the solution, and the precipitated metal values are removed by filtration. [0023] The pH of the solution is then raised, hydrogen sulfide or NaHS is again added to the solution to precipitate cobalt and nickel as sulfides. Aluminum and some remaining zinc may also be precipitated as sulfides in this step. [0024] Preferably, the pH of the solution is then raised to about 9 to precipitate and recover manganese oxides and hydroxides at 22. After filtering the residue, the remaining solution is a nitrate product 26 which can be used as fertilizer, or as a source of nitrates for reuse in the process. ALTERNATIVE EMBODIMENTS [0025] Alternatively, the manganese-containing material can be derived from industrial waste or chemical processing, or ores from land mining operations, which ores contain manganese, or manganese-containing materials resulting from processing such ores. The

manganese-containing materials can be obtained by the prior chemical or metallurgical treatment of polymetallic nodules obtained from any body of water. [0026] Either the NH ₃ or the manganese-containing material, or both, may be heated to enhance the reaction. Further, liquid ammonia may be used in the process, but gaseous ammonia is preferred. SUMMARY OF THE ACHIEVEMENT OF THE OBJECTS OF THE INVENTION [0027] From the foregoing, it is readily apparent that we have invented an improved method for treating manganese-containing material including the treatment of seafloor manganese nodules recovered by undersea mining, to effectively react the material with ammonia to produce a manganese oxide product and release any valuable metals, and for recovering the metal values contained in the nodules efficiently. We have also invented an improved method of recovering manganese from manganese-bearing materials, including recovering other metal values from manganese-bearing materials, such metal values including, if present, nickel, cobalt, copper, magnesium, aluminum, iron, calcium, cadmium, potassium, sodium, zirconium, titanium, zinc, lead, cerium, molybdenum, phosphorus, barium, and vanadium; as well as an effective method of recovering metal values from seafloor manganese-containing materials including deepsea manganese nodules, and for producing a nitrate product. [0028] It is to be understood that the foregoing description and specific embodiments are merely illustrative of the best mode of the invention and the principles thereof, and that various modifications and additions may be made to the apparatus by those skilled in the art, without departing from the spirit and scope of this invention.