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Omar, R., Ali Rahman, Z., Latif, M.T., Lihan, T. and Adam J.H. (Eds.) Proceedings of the Regional Symposium on Environment and Natural Resources 10-11th April 2002, Hotel Renaissance Kuala Lumpur, Malaysia. Vol. 1: 287-295 ____________________________________________________________________________________________________________

RARE EARTH PROCESSING IN MALAYSIA: CASE STUDY OF ARE AND MAREC PLANTS 1

2

Meor Yusoff M.S. and Latifah A. 1

Malaysian Institute for Nuclear Technology Research (MINT) Bangi, 43000 Kajang, Selangor DE 2 Centre for General Studies, Universiti Kebangsaan Malaysia 43600 Bangi, Selangor DE

E-mail: [email protected]

ABSTRACT Malaysian has an estimated rare earths reserve of 30,000 tons and this mainly comes from the tin by-product minerals. Monazite, (Ce, La, Th) PO 4 , is the more abundance and economic importance, it is made up of mainly the light rare earth elements while the other rare earths mineral xenotime (YPO 4) contains mainly the heavy rare earth elements. Traditionally rare earths are used in its mixed form especially especially as petroleum cracking catalyst. The advancement in material science had lead to many new high technology applications involving the used of highly purified individual elements. In Malaysia, two rare earths processing plants had been operated to utilize these local resources. The paper reviews the plants processes, failure of these plants, the radioactive waste issue and steps required in overcoming these problems.

INTRODUCTION Rare earths and its mineral resources in Malaysia

Rare earths elements comprised of 17 different elements including the lanthanum series, yttrium and scandium. The lanthanum series comprises of 15 elements from lanthanum (atomic number 57) to lutetium (atomic number 71). Classically, this lanthanum group can be categorized into two different categories, the light or cerium group and heavy or yttrium group. The cerium group includes elements from lanthanum through dysprosium (atomic number 66) while the yttrium group comprises holmium (atomic number 67) through lutetium (atomic number 71). The heavy rare earth group is so name as yttrium group even though the element yttrium is not part of the lanthanum series because of its occurrence in nature is always with these elements. Abundance of natural resources is an advantage that Malaysia has over its competitors and mineral resource had played a very important role in nation building especially during its early years. Besides being an important exporter of tin, Malaysia also produces other associated minerals from the tin mining activities. Two of the important rare earths minerals produced is monazite and xenotime. Monazite, (Ce, La, Th) PO4 , is a phosphate mineral comprises mainly of the light rare earth elements especially Ce, La, Nd and Pr. The mineral also contains considerable amount of heavy rare earths element notably yttrium and naturally occurring radioactive elements thorium and uranium. In


Malaysia, monazite is classified as a radioactive mineral and normally contains about 6% thorium and 0.3% uranium. Table 1 shows Malaysian monazite production. Quantity of monazite produced had been decreased with many of the tin mines closing down. But there is a sudden increased in the demand for monazite in 1999 and this is attributed to the supply of the mineral to China. Monazite was initially used for making thorium nitrate filament in gas mantle lamp but with the widely used of electricity, demand for thorium and gas mantle drops. The interest towards thorium increases when in 1946 scientists were able to change Th-232 into the fuel material U-233. But with the abundance availability of uranium and phasing out of nuclear power reactors make thorium as not important. Thus most of the available monazite cracking plants produce rare earths as their most important product. Thorium is now considered as only a by product from the process or at times being placed as the radioactive waste. Table 1: Malaysian monazite production Year 1988 1992 1993 1999

Production (tons) 2920 777 407 1147

Xenotime (YPO4) is also an orthophosphate rare earth mineral. Although obtained as a by-product from the tin mining industry, the mineral is less abundance and is available in certain tin districts in the country. The mineral comprises mainly of heavy rare earth elements especially yttrium. Unlike monazite, xenotime contains higher uranium than thorium and in Malaysia it normally contains 2% uranium and 0.7% thorium. The production of this mineral in 1999 is 22 tons. Rare earths processing in Malaysia

Flow chart of the Malaysian rare earth processing is as that shown in Figure 1 below. Amang is obtained from tin mines after undergoing gravitational separation from other light minerals. The rare earth minerals are then produced after the amang undergoes several stages of gravitational, magnetic and conductivity separation at tin mines or amang plants. Rare earths present in these minerals will then be recovered into concentrates at mineral cracking plant. These concentrates contain mixed rare earths, separated into the light and heavy rare earths groups. Rare earth concentrates are used in petroleum cracking catalyst, metallurgical additives, fertilizers, etc. But the products produced by the Malaysian plants are mainly used as starting material for the rare earths purification plants in Japan. The advancement of material science and technology had also resulted into the applications of very high purity individual rare earths element. The purity of the rare earth is much dependent upon its application and these ranges from 95% to 99.99999%. Multiple stages solvent extraction process had been used to produce element of this high purity. High purity rare earth elements are produced to meet the stringent quality and properties of new and emerging materials such as permanent magnet, electrical ceramic, phosphor, etc

Meor Yusoff M.S. and Latifah A.

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Tin Mine

Amang (Heavy minerals) Tin Ore (Cassiterite) Rare Earth Minerals (Monazite and Xenotime) Cracking plants

Rare Earths Concentrates

Separation/Purification High Purity Rare Earth Element

Figure 1: Flow process of Malaysian rare earth mineral

Applications of rare earths

Rare earths are used both in their mixed concentrate as well as the high purity individual element. Mixed light rare earths concentrates are by tradition mainly used as petroleum cracking catalyst. In recent years, the growing concern over environmental pollution particularly caused by acid rain, petrochemical haze and low-level ozone concentrations have increased the demand for automotive catalytic converter. Rare earths catalytic converter in the form of 95% to 99.9% purity cerium oxide is added to alumina to split the oxygen away from the nitrogen as well to enhance the alumina stability at high temperature. Phosphor is manufactured by introducing small amounts of light emitting products under controlled conditions into a die. Red emitting phosphor uses two rare earths, yttrium and europium. Besides cathode ray tubes for TV and monitors, phosphors are also used for flourescent lamp. About 180 tons of yttrium is consumed annually for the production of colour TV while the fluorescent lamp uses 200 ton. Rare earths are also used in the production of glass, both in the form of additives to stabilize the TV face plates and also for the polishing of the glass surface. Cerium oxide concentrate is used for this purpose. In the context of electronic glass, application includes in the field of communication where lanthanum is used to make high refractive index glass, optical systems and analytical equipment. High purity rare earths elements are used widely in many advanced materials applications. The production of rare earths magnet had added a new dimension in this field. Sm-Co magnet has 8-10 times greater magnetic power compared to traditional ferrite and this had lead to new innovation of miniature and portable electronic


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equipments such as the walkman CD and stereo, mobile phone and notebook computer. Another important milestone in the rare earth magnet is the development of Nd-Fe-B magnet with better magnetic power and cheaper cost than the Sm-Co magnet. It could be used in motors of automobiles, magnetic bearings and ignition, analytical and medical equipment, toys, etc. The total rare earths consumed both as concentrate and high purity in 1989 was 28,000 tons. Analyst had forecast that this value will be increased at a rate of 4% per year to 37,000 tons in 1997. But this figure had also been influenced by the slow demand especially on the electronic sector as a result of the Asian financial crisis in 1997-1998. Rare earths consumption in the US drops to 11,500 tons in 1998 as compared to a previous year high of 19,400 tons. Table 2 below shows the percentage consumption of rare earths in US according to its applications sectors. The amount of rare earths consumed tends to fluctuate especially among the top six applications. In 1998, there is a drastic fall in the petroleum cracking catalyst and permanent magnet usage of rare earths as compared to that of 1996. Table 2: Rare Earths consumption in US according to its application sectors Application Sector

Automotive catalytic converter Petroleum cracking catalysts Permanent magnets Glass and ceramics Alloy Phosphor Miscellaneous

Consumption (%)

1996 46 25 12 7 7 3 1

1998 35 10 5 31 14 3 2

RARE EARTHS MINERAL PROCESSING INDUSTRY IN MALAYSIA Asian rare earth (ARE)

ARE is a monazite cracking plant located at the Bukit Merah Industrial Estate which is about 7 km from Ipoh, the capital city of the tin-rich state of Perak. The company was established as a joint venture between Mitsubishi Chemical Industries Ltd., Japan, BEH Minerals Sdn Bhd and other local companies to produce mixed rare earths products. Besides the light and heavy rare earths, the plant also produces tricalcium phosphate as a by-product from the process. On operating at full capacity, ARE production per annum is 4200 tons of light rare earth, 550 tons of heavy rare earths and 4400 tons of tricalcium phosphate. These rare earths products normally contained 50-55% total rare earths and they are exported to the Mitsubishi purification plant in Japan for further separation and purification. The process involved in the digestion of monazite at this plant is by the caustic soda method (Figure 2).


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MONAZITE

↓ MILLING

↓ DIGESTION

↓ FILTERATION

→

EVAPORATION

↓ PARTIAL DISSOLUTION

→

TRICALCIUM PHOSPHATE

↓ FILTERATION

→

THORIUM CAKE

↓ RARE EARTH SOLUTION

↓ SOLVENT EXTRACTION LIGHT RARE EARTHS

HEAVY RARE EARTHS

Figure 2: Flow chart of monazite cracking process at ARE

Caustic soda is used primarily to separate the phosphate from the rare earths and thorium. At this stage, the rare earths and thorium are converted to their hydroxides as shown in the following reactions: (RE)PO4 + 3NaOH

→

TH3(PO4)4 + 12NaOH

→

(RE)(OH)3 + Na3PO4 3Th(OH)4 + Na3PO4

(I) (II)

The phosphate compound was then separated from the hydroxide by dissolving it water. This is crystallized out and converted to tricalcium phosphate. Thorium and rare earths are separated by the partial dissolution method. Here, rare earths are dissolved in concentrated HCl while the undissolved is filtered and produced as thorium cake waste.


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Separation of light and heavy rare earths is carried out by means of solvent extraction technique using DEHPA diluted in kerosene as its extracting medium. Multistage extraction using counter current mixer settler is use for this purpose. The final stage of this process is the carbonate precipitation of both light and heavy rare earths. A few years after operating, ARE faces protests from nearby residences on its radiation safety. The plant was forced to suspend its operation in the early 90s by a decree from the High Court but later the order was revoke by a higher court. In 1994, a decision was made by the shareholders for the plant to cease its operation. Besides the protests, the closure was primarily attributed to the company operating losses from the effect of global low prices of mixed rare earth products. The responsibility of the radioactive waste produced from this plant becomes the single most important issue after this closure. Malaysian rare earth corporation (MAREC)

MAREC is the xenotime processing plant. Located in the same compound as its sister company, ARE, the plant operated mainly for the production for the production of yttrium oxide concentrate. The capacity of the plant is smaller than that of ARE where at full operational capacity it can only produced 200 tons of yttrium oxide concentrate per year. Yttrium oxide produced from this plant had a yttrium content of about 60% yttrium. Sulphuric acid digestion technique is use in the xenotime cracking process. Here, xenotime is first milled to its required particle size before roasted in a furnace (Fig. 3). XENOTIME ↓

ROASTING ↓

DIGESTION ↓

FILTERATION

→

RADIOACTIVE WASTE

↓

PRECIPITATION (YTTRIUM OXALATE)

→

CALCINATION (YTTRIUM OXIDE)

MAREC Figure 3: Xenotime cracking process at MAREC This is to ensure that good yttrium recovery is obtained in the next stage. In the digestion stage, YPO4 presents in xenotime will be converted to the water-soluble yttrium sulphate. Cold water is use as the leaching medium in the next stage for maximum recovery. Yttrium will then be precipitated as yttrium oxalate by the addition of oxalic acid. The


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final stage involves in the process is the calcinations of yttrium oxalate into yttrium oxide. MAREC was closed down soon after ARE was operated commercially. This was done to consolidate on the monazite cracking process which was carried out at a much bigger scale

WHY THE MALAYSIAN RARE EARTHS PROCESSING INDUSTRY FAILS Radioactive Issue

There are several reasons for the failure of both the MAREC and ARE plants in Malaysia. The most notable reason is the environmental issue especially radioactive resistance due to the proximity of these plants to nearby residents. These resistances comes both from the safety of the process and also the thorium hydroxide waste produced and stored on the plant site. From these complaints, the local radioactive regulatory body, Atomic Energy Licensing Board (AELB) had made studies on the safety of the plant process and from this a stricter safety procedure was imposed. Thorium hydroxide waste contains highly concentrated long-lived radioactive elements thorium and uranium, classified as radioactive waste under Atomic Energy Licensing Act, 1984. This Act also stated that the waste had to be stored or disposed at a safe and suitable location. ARE asked the Perak state government for a long-term radioactive waste storage facility and this was agreed to a 84.2 acres hilltop site in Bukit Kledang. The implementation for a stricter working procedure as well as the construction and transportation of radioactive waste to its new site incurred further financial costs to the company. After the closure of the ARE plant, further expenditure is incurred in the decommissioning and decontamination (D&D) of radioactive contaminated materials. The D&D activities involved includes: a. Dismantling of buildings, equipments and machineries b. Dispose of contaminated materials in engineered cells c. Monitoring of designated area Further financial allocation had to be made to ensure that the radioactive waste stored in the long-term storage facility will be stable and safe in years ahead. Economics

The failure of ARE and MAREC may also be attributed to the joint venture agreement made between Mitsubishi and the local companies. Market price and marketing of rare earths products produced from these companies are solely decided by Mitsubishi. As the rare earths served as feed materials for the purification plants in Japan, Mitsubishi tends to maintain a lower price for these products. Rare earths products produced from these plants are also not directly used by Malaysian companies as they need to be further separated before could be used in the industry. On the other hand, Malaysia imports about


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US$4 million annually of cerium oxide for its electronic and glass industry. Also the large capacity of ARE plant had made its operation not strategic as the demand for rare earths declines in the late 1980s as a result of large production by China. This eventually leads to a higher cost of production by ARE (US$4.30/kg) than the selling cost of light rare earth product (US$2.66/kg). Technology

The present rare earths processing scenario had change compared to that of the 1980s. Besides Malaysia, similar cracking plants in developed countries like USA and France had also closed their operations. On the other hand, new monazite cracking plants are constructed developing countries like Vietnam and Egypt. France was once the biggest producer of rare earths concentrate is now concentrating on producing the high purity rare earths elements from non-radioactive feed materials. Other important rare earths producing countries like China and India are operating both cracking and purification plants. The local rare earths cracking plants have their processing technology based entirely from Mitsubishi patented processes. This technology is only capable at producing mixed rare earths concentrate to be used as radioactive free feed materials for high purity rare earths plants in Japan. Malaysian experienced in rare earths separation and purification technology is only limited to the used of multistage solvent extraction process for the separation of light and heavy rare earths groupings. As prices of mixed rare earths are relatively very cheap compared to the high purity rare earth element, not much money is made from such operation. Table 3 below shows the different prices of rare earths. Table 3: Price of monazite, mixed and high purity rare earths Rare Earths Products

Monazite Light Rare Earth Chloride Cerium Neodymium (99.0% to 99.9%) Yttrium (99.0% to 99.9%)

Market Price (US$/Kg) 1996 1998 0.28 0.40 2.60 1.19 27.14 25.50 22.00 29.50 17.00 22.00

FUTURE OF RARE EARTHS PROCESSING IN MALAYSIA

The experienced in setting up of rare earths cracking plants in Malaysia will deterred any new party in pursuing similar operations. But in view of the importance of rare earths especially as an important and strategic material, the following options should be considered: a. To acquire the rare earths separation and purification (both multistage solvent extraction and ion exchange) technology b. Due to the its radioactive sensitivity, Malaysia should embark on using nonradioactive starting material such as mixed rare earth compounds as feed material


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c. Create industrial linkages between these high purity products and relevant electronic and automobile industries by producing rare earth magnet, automobile catalytic converters and phosphors. CONCLUSION

The local rare earths processing industry only produced low value-added products and Malaysia should move ahead in producing high purity rare earths elements. This could be achieved by acquiring the separation and purification technology.

REFERENCES

Meor Yusoff, M.S. 1991, An overview of the rare earth mineral processing industry in Malaysia, Industrial Minerals Special Review- Rare Earths: Future prospects, Metal Bulletin, Surrey, U. Kingdom. Hendrick, J.B. 1997. Rare Earths, U.S. Geological Survey- Minerals information- 1996 , U.S. Geological Survey, Maryland. Taylor, R.A. 1991, Australian rare earth resources for the electronic industry, Industrial Mineral Special Review: Future prospects, Metal Bulletin , Surrey, U. Kingdom. Meor Yusoff, M.S. 1993, Research and development on effective utilization of radioactive minerals and waste, Proceedings Malaysian Science and Technology Congress `93 , Kuala Lumpur, Aug. 1993. Roskill Information Service Ltd. 1994. The Economics of Rare Earths, 9 th Edition, London. Meor Yusoff, M.S. and Noraishah, P. 1999. The role of hydrometallurgy in the treatment of Malaysian TENORM waste, Presented at 5th Regional Waste Management Seminar , Manila, 9-11 Nov., 1999. Hendrick, J.B. 1999. Yttrium U.S. Geological Survey- Minerals information- 1999 , U.S. Geological Survey, Maryland.


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