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M e t a l E x t r a c t i o n P r o d u c t s

CYANEX® 600 Molybdenum Extractant

Introduction Cytec has developed a novel solvent extraction (SX) process to recover molybdenum from acidic solutions using CYANEX® 600 extractant. CYANEX 600 is a highly selective, stable phosphinic acid based reagent.

This new technology will allow various operations to produce an additional profit stream.

Background

As a valuable, high demand by-product, molybdenum is of significant interest for many operations. Traditionally, molybdenum has been recovered through flotation and roasting; however, significant amounts of molybdenum are also found in smelter dusts, spent catalysts, roaster off-gases and recycled alloys. Many operations are implementing leaching processes to increase molybdenum recovery, improving the overall operation and process economics. In some cases, such as copper SX, molybdenum is already present as dissolved species in the raffinates and it is not commonly recovered.

CYANEX 600 SX technology allows molybdenum recovery from acidic solutions originating from both low grade (e.g. copper SX raffinates, smelter dusts and slags) and high grade (molybdenite) sources.

CYANEX 600 Advantages

• Highly selective for molybdenum• High selectivity against anionic species,

including sulfate, chloride, arsenic and metals like iron, aluminum, manganese, copper, cobalt, nickel, chromium, and rhenium

• Fast kinetics• Excellent stability• Good phase disengagement properties• High solubility• No rich strip liquor purification required

Chemical and Physical Properties

• Appearance: colorless to light amber liquid • Specific Gravity 0.92 @ 24°C• Viscosity, Brookfield

o <150 cP @ 25°C o <50 cP @ 50°C

• Boiling Point >300°C • Flash Point, closed cup >108°C

Selectivity

CYANEX 600 is highly selective for molybdenum at low pH. Figure 1 shows the extraction behavior of common metals at pH <2.0.

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Figure 1: CYANEX 600 extraction curves from sulfate

solution

Minor impurities that may also be extracted at pH <2.0 include uranium, titanium, hafnium and zirconium. These impurity metals can be efficiently scrubbed from the circuit using different acids or bases.

Typical Molybdenum Recovery Flowsheet

Figure 2 shows a molybdenum recovery flowsheet incorporating CYANEX 600 SX. In the extraction stage, organic recirculation can be used for low molybdenum feed solutions, allowing the molybdenum concentration in the organic phase to be significantly increased. The loaded organic phase can be scrubbed to minimize impurity transfer to the rich strip liquor due to aqueous entrainment or chemical transfer. Stripping is then carried out under basic conditions to concentrate the molybdenum followed by crystallization of a molybdate product.

Figure 2: Typical molybdenum recovery flowsheet

Crystallization / Final product

Various molybdate products can be produced from the rich liquor by crystallization. Common crystallization methods include: evaporation and acidification. Ammonium tetramolybdate (ATM) can be crystallized from the strip liquor by adjusting the pH of the solution using sulfuric acid. The crystalline quality of ATM is shown in Figure 3 (photo) and Figure 4 (Scanning Electron Microscopy (SEM) image).

Process

Wash

Stripping

Process

Rich Liquor Tank

PLS

AmmoniumTetramolybdate

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Figure 3: Ammonium tetramolybdate

Figure 4: SEM image of ammonium tetramolybdate

platy and acicular crystals, showing a highly crystalline

product

The final product has a high purity and can be sold using existing market outlets. Table 1 shows the typical analysis of ammonium tetramolybdate produced using the CYANEX 600 process. The yield for the crystallization process is typically greater than 90%.

Ammonium tetramolybdate crystallization can be performed as a batch process, by continuously taking a bleed stream from the aqueous strip liquor.

Table 1: Ammonium tetramolybdate purity, ppm unless

otherwise noted

Testing and Trial Support

A number of trials ranging from lab scale to larger on-site pilot scale trials have been completed to demonstrate the feasibility of the technology, including SX and crystallization. Raffinate streams, smelter dusts, and molybdenite have been proven to be economical sources of molybdenum from these studies.

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• Email: custinfo@cytec.com Worldwide Contact Info: www.cytec.com US Toll Free: 800-652-6013 Tel: (+1) 973-357-3193 •

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Results from one example using a smelter dust source are summarized below.

• Average molybdenum recovery of 87% from a PLS containing 260 ppm molybdenum and 80 g/L sulfuric acid.

• High selectivity achieved. Co-extracted impurities such as iron, arsenic and zirconium (<20 ppm) were efficiently scrubbed in the wash stage.

• Molybdenum was concentrated in the strip stage to 90 g/L.

• Crystallization by acidification yielded a high purity ammonium tetramolybdate salt containing more than 56% molybdenum.

• 2 – 3 minute phase break times in the extract/scrub stages and 3 – 5 minute phase break times in the strip stages were achieved.

• Minimal organic and aqueous entrainment, dispersion bands, and crud formation was observed.

Contact your Cytec sales representative for more information on CYANEX 600 technology. Our technical experts will work with you to maximize molybdenum recovery from your acidic aqueous streams.