I

Overview

Stabilizing Toxic Metal Concentrates by Using SMITE

Tim White and Irfan Toor

Synthetic mineral immobilization tech­nology is an approach for the treatment of heavy-metal concentrates. Although the no­tion of using synthetic mineral analogs for the stabilization and consolidation of nuclear waste has been discussed for more than 40 years, its application to inorganic hazardous waste, in general, is only now being realized. The advantage of this technology is that high-waste-Ioaded and high-density waste forms can be fabricated while maintaining excellent chemical durability. These proper­ties translate into considerable savings dur­ing transport and disposal.

INTRODUCTION

Synthetic mineral immobilization technology (SMITE) is emerging as an important methodology for the treat­ment of hazardous inorganic wastes. The first significant research program began in the 1970s at Pennsylvania State Uni­versityl,2 to develop materials for the stabilization of high-level and defense nuclear wastes. The success of this work spawned a host of similar efforts3--5 based upon different classes of mineral ana­logs (excellent reviews of these strate­gies are given by Lutze and Ewing6); however, these studies were curtailed in 1982 after vitrified waste forms were selected as the preferred stabilization media? Nonetheless, persistent doubts concerning the suitability of glasses for all nuclear waste types remained, lead­ing to a resurgence of interest in syn­thetic mineral waste forms, particularly for the immobilization of both mixed waste8,9 and weapons-grade uranium and plutonium.1o

The treatment of nonnuclear hazard-

High

ous wastes by SMITE is less developed, Traditionally, hazardous waste concen­trates have been stabilized by cementa­tion processes, usually by blending Port­land cements and pozolanic materials, and large volumes of contaminated soil and sludges have been treated using a variety of in-situ and ex-situ processes. However, this approach has a number of drawbacks, Perhaps the most serious is that many inorganic salts are encapsu­lated in the cement rather than incorpo­rated in insoluble phases, and these may release catastrophically through the in­gress of ground water or because of physical disturbance. This limitation can often be addressed through the dilution of waste in the concrete or by the intro­duction of additives (e.g., clays and zeo­lites), although this adds substantially to the cost of stabilization, Furthermore, the use of high chemical doses increases bulking factors considerably, which, in tum, translates into uneconomic landfill charges. ll

Neither is the development of new cementitious treatment regimes a simple matter. The hydration mechanisms in ordinary Portland cement continue to be a subject for debate, and the mecha­nisms by which inorganic salts interfere with and retard setting processes are difficult to define. More seriously per­haps, the chemical and microstructural complexity of these systems makes it virtually impossible to routinely vali­date the speciation and fixation of all the components in a real waste system-the continuing discussion concerning the nature of arsenical phases in cement re­flects this uncertainty.12-14 In combina­

High tion, these factors mean that the economics of ce­ment stabilization are not always viable and the long-term stability of Portland cements cannot be reliably predicted.

System Low~ ______ ~ __ ~ __ ~~ ____ ~ Low Type 3

Just as the limitations of cementitious systems are being tested, the cri­teria for materials that are to be classified as land­fill-compliant are becom­ing increasingly strin­gent. Internationally, the waste management in­dustry is confronted with meeting not only current

Type 1 Type 2 Hydramelallurgy Hydrametallurgy Pyrametallurgy

+ Pyrametallurgy

Figure 1. Properties and processing regimes for SMITE types.

54

Type 2 SMITE

Figure 2. General flow sheet for type two SMITE stabilization of toxic metal concen­trates.

disposal criteria but also those criteria likely to be enshrined in legislation be­fore the tum of the century. In some instances, this uncertainty has paralyzed waste management programs, resulting in waste stockpiles on industrial sites­a scenario that arguably increases the chances of accidental releases. There­fore, alternative strategies for the treat­ment of hazardous inorganic wastes are urgently needed.

THE SMITE APPROACH

Synthetic mineral immobilization technology is defined as follows:

"Upon the basis of established geologi­cal principles, a mineral or group of mutually compatible minerals is selected whose crystal structures can incorpo­rate all the species of a given waste stream, and which, by the addition of certain chemicals, may be prepared eco­nomically without the generation of sec­ondary waste streams, to produce a du­rable waste form."l5

All SMITE types are fundamentally two-stage preprocessing and consolida­tion procedures (Figure 1), In stage one, the waste may be purified, redox ad­justed, or prestabilized. In stage two, the intermediate product is converted into the final waste form, Type one SMITEs require multiple hydrometallurgical stages, which are low-cost, often techno­logically straightforward, and suitable for application in the field, In contrast, type three processes (e.g., as applied to high-level nuclear waste) are based on technically complex pyrometallurgical treatments and undertaken at central waste treatment facilities, The interme-

JOM • March 1996

diate type two approach, which is the major focus here, combines the best fea­tures of these pre-existing applications so that hazardous waste disposal is opti­mized in terms of cost, portability of plant, and durability of waste forms.I6

icsY Nevertheless, true vitrification of waste so­lutions can achieve sub­stantial volume reduc­tions.I8 In contrast to vit­rification, SMITE meth­ods routipely achieve waste loadings that are in excess of 20 wt. % with systems tailored to maxi-

~ ____ I,~j:I ___ I __ w_M~;R I \/\/\/

L SL.;R_.R •• ~1 .. , I NITROGEN I

In type two SMITEs, the waste is first reacted with acidic or basic initiators that either precipitate the toxic metals from solution and/ or convert them into nonvolatile substances. Tailoringchemi­cals are also introduced at this point so that they are intimately combined with the waste and are available during the second pyrometallurgical reaction to produce compositions appropriate for the desired synthetic mineral assem­blage. The fired product may be formed as a powder, gravel, or monolith suit­able for future extraction of valuable components, direct disposal in landfills, or fabrication of concrete waste forms. A general flow sheet for stabilization is shown in Figure 2.

mize this parameter. A potential problem asso­ciated with glass manu­facture is that it is not inherently suited to mini­mizing sublimation of waste species, particu­larly if highly volatile compounds are abun­dant. For example, even though cesium isotopes are introduced at less than 3 wt. % during high­level nuclear waste glass fabrication, losses from the melt must be cap­

OPTION 1,.c-1 FIRE ... t """' ...... ""1· OPTION 2

\/ 'v'

\/\1 _ ..

LANDFILL

DISPOSAL

CEMENT

!tis important to differentiate between type two SMITE procedures and vitrifi­cation. Although both use high-tempera­ture processes to achieve consolidation, the general approach as well as the form of the final products are quite different. Glasses immobilize waste to a dilute limit, which, depending on composition, will not usually exceed 15 wt.% and in many cases is considerably less. Al­though claims are made for vitrification at higher waste loadings, close examina­tion usually reveals that significant crys­tallization has occurred, and many prod­ucts are best described as glass ceram-

Figure 4. Flow sheet for SMITE stabilization of thallium chro­mate sludge.

tured and recycled,t9 or alternatively, cesium is ion-exchanged onto zeolite and introduced to the melter with the glass frit.2° Many metals and oxides sublime even more easily than cesium. During experiments to prepare glassy slags for arsenic stabilization, it was found that more than 90 percent of the arsenic sub­limed.21 SMITE is not generally limited in this way, provided that a low vapor pressure precursor can be prepared by hydrometallurgical reaction. Energy costs also differ as SMITE products rarely

::::::~:;::::::~;:;:::~~::::::~::::::l requiretreatrnentabove I 1,100°C and lower tem-

I As<5ppm I~

TCLP < 0.5 ppm As loading - 22

L..-.----::----'

OVEN DRY

FIRE

Figure 3. Flow sheet of SMITE stabilization of arsenical flue dust.

1996 March • JOM

peratures are often satis­factory,22 whereas vitri­ficationis usually carried out at temperatures greater than 1,150°C.23

ARSENIC TRIOXIDE FLUE

DUST

Design Arsenic trioxide (ar­

senolite) is a voluminous by-product generated by roasting arsenopyritic ores of base and precious metals to reduce sulfur levels sufficiently for smelting. Flue dust of­ten occurs as nearly pure arsenolite, although it commonly coexists with antimony, lead, or cad­mium oxides. Extensive experimentation has shown that the most du­rable mineral currently recognized for incorpo­rating arsenic at high concentrations is an apa­tite-type (known as sva-

bite), which has the ideal stoichiometry of Cas(AsO 4)3F. The overall stabilization reaction, which is promoted by the addi­tion of lime (the initiator) and calcium fluoride (the tailoring chemical), can be written thus:

3AsP3 + 9CaO + CaF2 + 30) ~ 2Cas(As04)3F (1)

There are two important points con­cerning this reaction. First, for apatite to crystallize the arsenic must be oxidized to the pentavalent state. This has impor­tant waste management implications as the trivalent form is generally consid­ered more soluble and toxic. During SMITE processing, oxidation is achieved by firing in air, and complete conversion to apatite is readily monitored by pow­der x-ray diffraction (hydrogen perox­ide or manganese oxide is often used to achieve the same effect in cementitious waste forms). Second, if a perfectly sto­ichiometric waste form were fabricated, an arsenic loading of 35.4 wt. % would be produced although, in practice, either lime or calcium fluoride are added in slight excess to accommodate fluctua­tions in flue-dust composition.

Solidification

A basic process for stabilizing arsenic is shown in Figure 3. Slacked lime and calcium fluoride are slurried together

Table I. TCLP Test Results from Arsenical Waste

Waste Form

Smelter Flue Dust Cement Encapsulation SMITE Ceramic SMITE Concrete

Arsenic TCLP Loading Results (wt.%) (As ppm)

60 20 22 18

4520 790 0.4

<0.1

55

ppm

6 7 8

Extraction Number 9 10

concrete. The cement acts as a secondary barrier to dissolution and can be used to pump the waste into landfills.

Testing

tain TP+ and Cr3+ rather than TP+ and Cr6+, as these latter species display higher toxicity. One compound that satisfies these requirements is a thallium analog of the mineral redledgeite having the ideal formula of TlzCrzTi6016.z7

Solidification Powder x-ray diffrac­tion confirmed that apa­tite was the dominant product while micro­analysis using energy dispersive x-ray spec­troscopy showed that calcium and arsenic ap­peared in the expected Figure 5. Multiple extraction TCLP data for thallium chromate­

bearing SMITE concrete. ratio of 5:3; fluorine can­not be detected using this technique. A small amount of silica, probably intro­duced with the lime, is also present and partially replaces arsenic by the coupled substitution

The SMITE waste form was prepared on the benchscale by solid-state reaction of TlzCrp7 and TiOz (Figure 4). Ingredi­ents of appropriate proportions were weighed into a beaker and slurried for two hours with water using a solid:liquid ratio of about 1 :2. The suspension liquor was filtered using a Buchner apparatus and Whatman paper, which generally collected all solids although some finely divided material passed through the fil­ter paper until a filter bed built up. The filtercake was warmed in an oven (110°C) until dry, then fired at 700-1,150°C for one hour under a stream of nitrogen. Using this regime, neutral conditions were maintained and the reduction of Cr(VI) to Cr(Ill) accelerated. The overall reaction was:

Table II. TCLP Test Results for Thallium-Chromate Products

Waste Loading TCLP

TI+Cr (ppm)

Waste Form (wt.%) TI Cr

Original Sludge 82 130 21 SMITE Concrete 30 0.7 0.08

with the arsenolite at room temperature for periods of 30 minutes for up to sev­eral hours. The reaction is regarded as complete when arsenolite can no longer be detected by x-ray diffraction. During this hydrometallurgical reaction, a fin­nemanite-like compound (probably con­taining water of crystallization) precipi­tates according to the reaction believed to approximate the following:

3AsP3 + 4.5CaO ~ 2Ca4S(As03)3 (2)

Fluorspar does not participate in this reaction, but is intimately mixed with the finnemanite precursor so that it will be available during firing. The precipi­tate is separated from the liquor by vacuum filtration until a solid contain­ing less than 10 wt.% water remains. (In full-scale production the liquor that con­tains <5 ppm arsenic is recycled.) The filtercake is oven-dried at 80-100°C to reduce water content to less than 5 wt.% and produce a robust gravel, which is sometimes reduced to centimeter frag­ments by light milling.

The gravel is converted into the stabi­lized waste form by firing in air for 30-60 minutes at l,OOO-l,100°C. A rapid-rise time of one hour is appropriate if suffi­cient oxygen is available to ensure the oxidation of arsenic. The second reac­tion is:

2Ca4S(As03)3 + CaF2 + 30) ~ 2Cas(As04)l (3)

The final product approaches theoreti­cal density (3.5 g/ cm3). This procedure (including deliberate addition of excess lime and/or calcium fluorite) yields a final waste loading of ",22 wt. % arsenic, which may be disposed of directly or used as aggregate to produce a SMITE

56

AsS+ + F- f-7 Si4+ + n. The durability of the waste form was

tested using the toxicity characteristic leach procedure (TCLP) method de­scribed elsewhere.z4,zs Typical results for the SMITE products are summarized in Table I, together with data for the un­treated flue dust and direct cement en­capsulation. As a guide, arsenical-so­lidified products are usually classified as suitable for secure or municipal land­fill disposal when the total arsenic ex­tracted in a single TCLP experiment does not exceed 5 ppm and 0.5 ppm, respec­tively. Both the SMITE ceramic and SMITE concrete easily meet the require­ments for landfill disposal while main­taining high waste loading.

THALLIUM CHROMATE SLUDGE

Design Thallium chromate (TlzCrp7) precipi­

tation is used in several industrial pro­cesses for reducing thallium levels. Al­though this compound is sparingly soluble, it does not meet regulatory cri­teria for landfill disposal and new meth­ods are required for treating this resi­due. The problem is nontrivial as thal­lium salts are almost uniformly soluble and chromate (VI) is not readily incor­porated in cement-hydrate phases.z6 Ide­ally, any stabilization matrix will con-

35 38 25 A

TlzCrp7 + 6TiOz ~ TlzCrzTip16 + 1.50z1 (4)

The fired powder was mixed with ce­ment in a redledgeite:cement ratio of 3:1 and allowed to cure for one month in a sealed plastic bag. The final product con­tained greater than 30 wt.% Tl + Cr.

Testing

Within the detection limit of powder x-ray diffraction, TlzCrzTi6016 was the only product present, suggesting that thallium volatilization was minimaL In actual use, titania would be added in excess to serve as a buffer against varia­tion in solids content of the sludge. En­ergy dispersive x-ray analyses were con­sistent with the expected stoichiometry, while scanning electron microscopy con­firmed complete encapsulation of the redledgeite by cement.

The cement-encapsulated redledgeite was tested by TCLP. For the first extrac­tion, an unbuffered acetic acid extractant (pH 2.88) was used, while for subse­quent extractions the buffered solution (pH 4.95) was employed. The data are presented in Table II and Figure 5. Losses of thallium and chromium are low and

22 28 J.8

D Apatite II Spinel II Anhydrite Figure 6. Powder x-ray diffraction pattern of SMITE stabilized municipal incinerator fly ash.

JOM • March 1996

Table 1111. TCLP Results for Incinerator Fly Ash and SMITE Ceramic (ppm)

Arsenic Chromium Cadmium Lead 0.60 0.25

Zinc Sulfur 21,285

34 Untreated Fly Ash Treated Fly Ash

4 0.20

0.22 0.006

within regulatory limits. Significantly, the losses continue to fall during succes­sive extractions, giving a high level of confidence that the waste form will dis­play long-term durability. It is expected that even lower leach rates could be achieved if greater attention were given to modifying the surface properties of the redledgeite to match those of the hydrating cement phases.

MUNICIPAL INCINERATOR ASH Design

In this test work, fly ash produced by a municipal incinerator was studied. Unlike the two previous wastes, ashes are chemically diverse, containing a range of toxic metals, and (as Kirby and RimstidF8 recently described) a wide range of compounds of various reac­tivities are usually present. For the ash used here, conclusively identified phases included anhydrite (CaS04), halite (NaCl), sylvite (KCl), and calcium sili­cate (Ca2SiOJ29 Such is the complexity of the ash that a polyphase synthetic mineral assemblage is required to stabi­lize all of its components. This assem­blage would normally consist of apatite, spinel, olivine, and anhydrite structure types.3D

Solidification

NaCl in the as-delivered fly ash had been introduced as a volatilization suppressant. Because the formation of soluble toxic-metal compounds such as NaAs03 is unavoidable, excess salt was partly removed by cold-water washing. For this washed material, a mineral as­semblage was designed to accommo­date the remaining toxic metals. In se­lecting the stabilization minerals, care was taken to exploit the presence of domi­nant species in the waste (particularly calcium, aluminum, and sulfur) and to enhance the propensity of the waste to form sparingly soluble refractories such as apatite. The major synthetic minerals and the waste-element partitioning in­cluded: Spinel ABp4,where A = Cu, Zn, and Ti and B = Fe, Cr, AI, and Mn; Apatite As(B04)3Cl, where A = Ga, Pb, Cd, Ba, Sr, and Na and B = As and P; and

Table IV. Physical Property and Cost Comparisons for Arsenic Stabilization

Cement Property SMITE Encapsulation As Loading 20-30wt.% 5-10wt.% Costs

Stabilization $241-437 $750-1,500 Disposal $490-754 $2,695-5,145

Vol. Increase 0-2x 5-10x Wt. Increase 2-2.5x 5-20x

1996 March • JOM

9 0.045

310 0.188

Anhydrite AB04, where A = Ca, Sr, and Ba and B = S.

To promote the formation of these minerals, the washed fly ash was slur­ried in a controlled manner with dilute phosphoric acid (supplying phospho­rus for apatite stabilization), lime (pro­viding calcium to react with sulfate and ensure apatite crystallization), and alu­minum hydroxide (capturing transition metals in aluminate spinel). The propor­tions of additives were determined on the basis of stoichiometric requirements and introduced in slight excess to ac­commodate ash nonhomogeneity. The precursor was then filtered, dried, and fired at 1,100°C to stabilize the final as­semblage at a loading of 54 wt.% ash.

Testing

X-ray diffraction confirmed that the desired mineral assemblage had crystal­lized (Figure 6). The predominance of apatite was to be expected as calcium and the majority of minor metals en­tered this phase. The apatites showed complex and variable chemistries reflect­ing the flexibility and adaptability of the structure. Stoichiometries ranged from near prototype CaS(P04)3Cl to apatites dominated by waste constituents includ­ing Si, P, AI, and S. TCLP tests confirmed that losses oftoxic metals from the SMITE waste met with the regulatory criteria for landfill disposal (Table III).

Although the direct treatment of in­cinerator ash is feasible, it seems more likely that SMITE will be applied to the treatment of heavy metal evaporates that will be removed from ash to render it nonhazardous and suitable for use as a construction material or roadfill.31

COMMERCIAL PROSPECTS

The commercial viability of adopting SMITE is presently undergoing detailed assessment; however, a single example will serve to illustrate the potential sav­ings. The quantity of arsenic released annually by smelting and other activi­ties has been estimated to approach 2.5 million tonnes per annum.32 Present prac­tice is to solidify arsenic in cement or store it as a dilute slurry in tailings dams.33

Neither of these approaches will prove satisfactory in the long term. In the case of cement encapsulation, arsenic load­ings must be maintained at below 5 wt. % to maintain the chemical and physical integrity of the solid (see Table 1).34,35 In tailings dams, arsenic trioxide is first slurried with iron chloride and lime (Fe:As ratio 1-4:1) to achieve overall ar­senic loadings of -5 Wt.%.36 Alternate stabilization strategies such as glassy

slags retain even lower waste loadings. In comparing the bulking factors of

arsenical waste forms, iron-arsenate tail­ings dams increase waste volume by more than 25 times while cement en­capsulation results in at least a six-fold volume increase because SMITE waste forms (even as concrete) yield loadings in excess of 20 wt. %. As this technology offers considerable savings when the cost of transport and landfill is considered, recent cost estimates suggest that, de­pending on local conditions, SMITE treat­ment of arsenical fumes can reduce sta­bilization and disposal charges by 5-10 times (Table IV).

CONCLUSIONS

The primary technical advances of SMITE over conventional technologies are the ability to predetermine and force metals into their least toxic states; the capacity to cope with wastes containing high concentrations of volatile inor­ganics; and the potential for achieving waste loadings at least double those pres­ently realized. This last property is par­ticularly important as it opens the way for adopting more cost-effective and flexible hazardous waste management strategies. In particular, because the waste is immobilized in a compact and durable form, it may, on occasion, be reasonable to store waste above ground if it is believed that a metal may become valuable in the future and extracted. An example would be antimony, whose price during the past two years has risen several fold. 37 If antimonical residues were diluted and dispersed in cement, it would be impossible to extract antimony economically; however, when incorpo­rated in a SMITE mineral (in this case Ca2Sb20l pyrochlore1S) interim storage may be feasible until extraction using established mineral processing tech­niques became viable. A second conse­quence of adopting high-density and high-waste loaded solids is that lifetime landfills could be extended significantly to yield social and political dividends.

References

1. G.J.McCarthyeta1.,"CrystaIChemistryoftheSupercalcine Minerals in Current Supercalcine-Ceramics," Ceramics in Nuclear Waste Management, DOE CONF-790420 (1979), pp. 315-320. 2. B.E. Scheetz et aI., Waste Mange., 14 (1994), pp. 489-505. 3. P.ED. Morgan et aI., J. Am. Ceram. Soc., 64 (1981), pp. 249-258. 4. A.E. Ringwood et aI., Nature, 278 (1979), pp. 219-223. 5. P.J. Haywood and E. V. Cecchetto, "Development of Sphene­Based Glass Ceramics Tailored for Canadian Waste Disposal Conditions," Scientific Basis for Nuclear Waste Management V, ed. S.V. Topp (New York: Elsevier, 1982), pp. 91-98. 6. W. Lutze and RC. Ewing, Radioactive Waste Forms for the Future (Amsterdam, Netherlands: North Holland Physics Publishing, 1988). 7. TD. Bemadzikowski et aI., Ceram. Bull., 62 (1983), pp. 1364-1390. 8. V.M. Oversby et al., "Imrnobilisation in Ceramic Waste Forms of the Residues from Treatment of Mixed Waste," Scientific Basis for Nuclear Waste Management XVII (Pitts­burgh, PA: MRS, 1994), pp. 285-292. 9. M. Genet et aI., "Thorium and Uranium Phosphatte Syn­theses and Lixiviation Tests for Their Use as Hosts for Radwastes," in Ref. 8, pp. 799-806. 10. A. Jostons et aI., "Synroc for lmmobilising Excess Weap­ORS Plutonium," in Ref. 8, pp. 775-782. 11. Anonymous, "Turn Hazardous Wastes into Nonhazard-

57

ous Wastes," Modern Metals, (May, 1995), pp. 54-56. 12. M. Carter et aI., "Inunobilisation of Arsenic Trioxide in Cementitious Materials," 6th AusIMM Extractive Metallurgy ConJerence (Melbourne, Australia: AusIMM, 1994), pp. 275-280. 13. J.5. Forrester, J.H. Kyle, and T.J. White, "Stabilization of Arsenic Trioxide Waste in Cement," Ceramics Adding Value, vol. 2 (Sydney, Australia: Australian Ceramic Society, 1992), pp. 104G-1046. 14. V. Dutre and e. Vandecasteele, Waste Manage., 15 (1995), pp.55-62. 15. T.J. White et aI., "Xtaltite-A Mineralogical Approach to the Disposal of Mercury and Arsenic Wastes," Extraction and Processing for the Treatment and Minimization of Wastes (Warrendale, PA: TMS, 1993), pp. 217-227. 16. T.J. White, Environ. Intern. (1995). 17. E. Wang et aI., "Effect of Fluoride on Crystallization in High Calcium and Magnesium Glasses," in Ref. 8, pp. 473-479. 18. e.M. Jantzen, Ceram. Bull., 74 (1995), p. 11. 19. J.P. Giraud, J.P. Conord, and P.M. Saverot, "Conceptual Design for Vitrification of HLW at West Valley Using a Rotary Calciner/Metallic Melter," Nuclear Waste Manage­ment, Advances in Ceramics, vol. 8 (Columbus, OH: ACerS, 19B4), pp. 132-142. 20. N.E. Bibler et aI., "Initial Demonstration of the Vitrifica­tion of High-Level Nuclear Waste Sludge Containing an Organic Cs-Loaded Ion-Exchange Resin," Scientific Basis Jor Nuclear Waste Management XVI (Pittsburgh, P A: MRS, 1993), pp.81-86. 21. F.RA. Jorgensen et aI., "The Safe Disposal of Arsenic in Metallurgical Slags," 2nd National Hazardous & Solid Waste Convention and Trade Exhibition-Achievements and Challenges (Sydney, Australia: Australian Water and Wastewater Asso­ciation, 1994), pp. 405-412.

Process-Oriented Topics

22. T.J. White et aI., "Xtaltite-An Advance Ceramic System for Immobilisation of Arsenical and Heavy Metal Wastes," Innovative Solutions for Contaminated Site Management (Alex­andria, VA: Water Environment Federation, 1994), pp. 437-448. 23. J.F. Sproull, S.L. Marra, and e.M. Jantzen, "High Level Radioactive Waste Glass Production and Product Descrip­tion," in Ref. 8, pp. 15-25. 24. J.R Conner, Chemical Fixation and Solidification oJHazard­ous Wastes (New York: Van Nostrand Reinhold, 1990), pp. 639-{;51. 25. T.J. White, "Design, Testing and Economics of Xtaltite Toxic MetaICeramics," Proceedingsofl00thAnnualNorthwest Mining Association Convention (Spokane, WA: Northwest Mining Association, 1994). 26. A. Kindness, A. Macias, and F.P. Glasser, Waste Manage., 14 (1995), pp. 3-11. 27. T.J. White et aI., "Xtaltite-Ecologically Sustainable Dis­posal of Heavy Metal Smelting and Refinery Waste," Interna­tional Symposium on the Treatment and Minimization of Heavy Metal Containing Waste (Warrendale, PA: TMS, 1995). 28. e.S. Kirby and J.D. Rimstidt, Environ. Sci. Techno!., 27 (1993), pp. 652-{;60. 29. T.J. White, "Synthetic Mineral Immobilization Technol­ogy for the Ultimate Disposal of Hazardous Inorganic Waste," (Paper presented at the International Congress of Waste Solidification-Stabilization Processes, Nancy, France, 28 November-1 December 1995). 30. T.J. White and I.A. Toor, "Synthetic Mineral Immobiliza­tion Technology for the Stabilization of Incinerator Ashes," (Paper presented at the Fourteenth International Incinera­tion Conference, Seattle, WA, 8-12 May 1995). 31. A. Jakob, s. Stucki, and P. Kuhn, Environmental Sci. Technol., 29 (1995), pp. 2429-2436. 32. R Frost, Search, 23 (1992), pp. 164-165.

UPCOMING EDITORIAL TOPICS

April 1996 1996 Review of Extraction and Processing

Materials-Oriented Topics

Nitrogen-Strengthened Powder Metanurgy Alloys .

May 1996 The Coating of Materials Recent Advances for for Corrosion Resistance Electrical Interconnects

PLUS: Quarterly Coverage of the Aluminum ProceSSing Industry

June 1996 The ThermQplasma Aluminum AllQys fQr Packaging Processing of Materials

July 1996

August 1996

The Cost-Effective Synthesis of High-Performance Materials

ReCent Developments in Copper Hydrometallurgy

Car Wars-Steel Strikes Back (Steel vs. Competitive Materials)

Semiconductors: The Nanoscale CharacterizatiOn of Heterostnwture Devices and thE! Comparison of Wide-Bandgap Structures

PLUS: Quarterly Coverage of the Aluminum Processing Industry

September 1996 Emerging Sensor Technologies for the Intelligent Processing of Materials

October 1996 The Processing and Application of Reactive Metals

PLUS: CeramicS in Micro-electro-mechanical Systems

November 1996

December 1996

Developments in the Primary Aluminum Industry

Innovations in Pyrometallurgy

Micromechanical Composite Materials

Materials for the Bulk Application of High-To Superconductors

High-Temperature Materials: Environmental Effects, Degradation, Failure, and Solutions

The Computer Simulation of Structllre/Property RelationShips in Irradiated Materials

PLUS: The Application of MathematicS to Problems in-Materials Science and Engineering

SUBMITIING PAPERS TO JOM

33. RG. Reddy, J.L. Hendrix, and P.B. Queneau, Arsenic Meta/lurgy~Fundamentals and Applications (Warrendale, P A: TMS,1988). 34. T.J. White, Search, 26 (1995), pp. 148-151. 35. A. Samarin, Waste Management and Environment (April 1995), p. 39. 36. G.P. Demopoulos, D.J. Dropper!, and G. Van Weert, Hydrometallurgy, 38 (1995), pp. 245-261. 37. P. Crowson, Minerals Yearbook (New York: Stockton Press, 1994).

ABOUT THE AUTHORS

Tim White earned his Ph.D. in solid-state chemistry at the Australian National Univer­sity in 1982. He is currently a professor of environmental technology at University of South Australia and project manager of SM ITE International Pty. Ltd. Dr. White is also a member of TMS.

Irfan Toor earned his Ph.D. in chemical engi­neering at the University of Florida in 1985. He is currently president of Texilla Environ­mental. Dr. Toor is also a member of TMS.

For more information, contact T. White, the Ian Wark Research Institute, University of South Australia, the Levels, SA 5095, Australia; tele­phone 61-8-302-3694; fax 61-8-302-3683.

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Manuscript Preparation

Scheduling The above publication deadlines allow approximately 12-14 weeks for review,

editing, proofing, typesetting, design, and printing. Since each issue carries a number of articles that must fit within topical and size constraints, author cooperation is expected. Minor delays can be very disruptive to the production process, and the editors should be quickly notified of problems.

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In brief, a correctly prepared manuscript is typed, double spaced, on 8.5 x 11 inch (22 x 28 cm) paper. Manuscripts (text and graphics) prepared on computer diskettes are not only welcome, but encouraged. The editorial office can handle a variety of formats. Papers must include: a title, a byline, a summary, an introduction, appropriate sub­heads, a conclusion, author biographies, references, glossy prints and/or high-quality artwork, and the address, telephone, and fax numbers of the designated contact author. All units must be in metric; SI is preferred.

To Receive an Author Kit, Call or Write: JOM, 420 Commonwealth Drive, Warrendale, Pennsylvania 15086; telephone (412)

776-9000, ext. 224; fax (412) 776-3770; e-mail jom@tms.org

James J. Robinson, Editor

JOM • March 1996