S Wayne Rosenbaum Recontek

The recycling of F006 metal hydroxide sludges can be viewed as a sinple problem in extractive metallurgy. Extractive metallurgy is the science of extracting and purifying metals frcm ore bodies.

The field of extractive metallurgy can be divided into two major branches, hydrcnetallurgy and pyrcmetallurgy.

Pyranetallurgy enccnpasses the high temperature technologies such as smelting, sweating, melting, and incineration. It is the oldest branch of extractive metallurgy, dating frctn before 2000 BC. Pyranetallurgy has shewn itself to be hic^ily cost effective when applied to very large and chemically consistent ore bodies. This is particularly true when the ore bodies are chemically exothermic at high temperatures such as metal sulfide cctrpounds.

Unfortunately, pyrcmetallurgy has several distinct disadvantages. Greatest among these aire the environmental concerns regarding air quality and the disposal of potentially hazardous slags and residues. Further, pyrcmetallurgy has not been demonstrated to be particularly successful where the feed streams vary widely in chemical ccnposition or where more than a few metals are to be extracted for conmercial application.

Hydrcmetallurgy is a much newer branch of extractive metallurgy. Its earliest ccnmercial applications date to the late 19th century with the extraction of gold and silver fran ore bodies using sodium cyanide dissolved in water. By the early 20th century, hydrometallurgical extraction of many transition metals frcm complex ores was being practiced throughout the United States and Europe.

With the advent of economical sources of direct current electrical pewer during the early 20th century, refineries which combined extractive hydrcmetallurgy using sulfuric acid or hydrochloric acid as the solvent with electrcwiiming of copper, zinc, and nickel sprang up throughout Europe and the United States.

Hie First World War resulted in American economic dominance in extracting metallurgy and refining also provided pyronetadlurgy with a dominant market position over the carpeting hydranetallurgical techniques. This was primarily due to America's abundant sources of cheap fossil fuels.

Most of the techniques required for the successful recycling of F006 sludges had been fully developed by 1920. REOONIEK has applied those techniques to a grcwing market as an alternative to landfill disposal.


The REOONIEK process relies on sulfate extraction and separation as the heart of its technology. Sulfuric acid was chosen as the extraction solvent for severed, reasons. Among those are:

1) Predictability

2) Environmental Concerns

3) Eccncmics

In order to demonstrate the process, a hypothetical lot of twenty tons will be discussed. The carpositions of this lot was based upon the average ccmposition of lots submitted to REOONIEK by potential customers for RECONTEK's Illinois facility, between July 1988 and November 1988. The constituents are as follows:

Metals 6.7%

Hydroxides (CH) 3.8%

Inert Materials 5.7%

TOTAL 100.0%

The projected metals contained are as follows:


1.69 %


1.29 %


.15 %


.43 %


.93 %


.32 %


1.60 %


.25 %


80 FEW





The first step in the REOONIEK process is to digest the sludge in sulfuric acid. Under good agitation the sulfuric acid converts the metal hydroxides to sulfates.

The sulfate insolubles, consisting primarily of lead, sulfate, calcium sulfate, precious metals and other inert materials are filtered off in a filter press and dried. After drying, the insoluble residue consists of:

Lead Sulfate

Calcium Sulfate and Inerts





2630 lbs

This material has an intrinsic value of approximately $1,300 per ton and is actively sought after by lead refiners.

The filtrate frcm sludge digestion is then distilled to remove any chlorides, borates, or nitrates which might be present. In this process the nitrates are deccnposed to nitrogen gas. The chlorides and borates are recovered as magnesium salts for sale as magnesium chloride, used in ccnditioning boiled water, dust control, and magnesium production.

The residue in the distillation reactor is then reconstituted with water, refiltered and sent on for ircn removal. The iron is removed by conversion to jarosite (NaFe3 (S04) 2 (CH) 6). The jarosite is filtered away and converted back to ferrous sulfate (FeS04) for sale to the fertilizer and water treatment industries. Approximately 1000 lbs of FeS04*7H20 are generated frcm each 20 ten batch.

The filtrate frcm the jarosite process is now ready for copper electrowinning. In this step, copper is extracted frcm the sulfate electrolyte down to a concentration of 500 pprn. While leaving the nickel, tin, chrcme, cadmium and zinc in solution. Each batch produces 679 lbs of cathode copper of 99% purity.

Cnce the copper has been depleted frcm the electrolyte, the cadmium and tin are removed by zinc cementation. That is, powdered zinc is added to the solution and tin and cadmium are precipitated in metallic form. The tin/cadmium residue is then filtered dried and sold to cadmium refiners.

At a slightly higher pH more zinc powder is added to the electrolyte to precipitate the nickel. This precipitate is then filtered and redissolved in sulfuric acid. This solution is sent to the nickel crystallizer where each batch then produces 1680 Iks NiS04'2H20. the residual concentrated acid is used to dissolve the next batch of inarming sludge.

A final pH adjustment and filtering are used to remove the chrctnium as chrcme hydroxide. Two hundred fifty pounds of chrcme hydroxide are produced by each twenty ten batch.

The zinc-rich electrolyte is now electrowon for zinc which can amount to as much as 1300 lbs. per 20 ten batch. Six hundred fifty pounds of zinc are extracted firm the waste stream while the balance ccnes frcm cementation zinc which was added to remove cadmium, tin, and nickel.

After the zinc has been removed, the sulfuric acid rich solution is returned to dissolve the next batch of sludge. Over time, the sodium concentrations will read unacceptable levels in the electrolyte. A bleed stream frcm the zinc cells is constantly being neutralized arid filtered. The saturated sodium sulfate solution thus created is crystallized out as sodium sulfate anhydrous for sale to the pulp and paper industry. Table one shows a complete mass balance for a typical batch.


One. important consideration when evaluating a new technology for waste disposal is its economic viability. In the past, hydrcmetallurgy could not ccrrpete with landfill disposal. In the past two years this has changed as a result of higher metal prices coupled with more stringent environmental regulations on land fills. Today, the economics of recycling are better than those for landfills as shewn by the following analysis.

Figure 1

Comparisons of Disposal Costs/Ton Hydranetallurgical Land

Figure 1

Comparisons of Disposal Costs/Ton Hydranetallurgical Land



Treatment Costs






Contingent Liability



Metal Recovery Credits






1. land Disposal tax costs vary fran state to state fron $40 to $130/ton. A mean of $85.00 per ten was used for this exanple.

2. Contingent liability under Superfund is assured to be no more than original disposal cost.

3. Metal recovery credits are based on average lot data with an assumption of no precious metal values (see Figure 2).

Figure 2

Economic Analysis of Average lot

Assume a 20 Ten lot. Processing fee per ton $300.

Discharge fee Analysis fee













•10/lb = $ 38.00 1.00/lb = 129.00 2.00/lb = 206.00

Recovered Metal Credits








$ 485















$ .45








$ .40


Net Cost to Customer for the lot Net Cost to Customer per ton

It is clear frcm this analysis that hydrcmetallurgical recycling as practiced by REOCNIEK is new cost competitive with land fill disposal. Further, as regulations cn land fills, such as leachate collection and treatment, become more stringent the cost of land fill Hjgpntai can cnly go up. Recycling costs should remain stable and will only rise with inflation and traditional siçply demand factors.


REOCNIEK has operated a pilot facility at San Diego, California since 1986 under the auspices of its wholly owned subsidiary, Pure Metals Corporation.

During this time, REOCNIEK has demonstrated each of the major components of the processes at 1/10 (2 ten) batch scale. Included in the processes tested were:

1) Sludge Digestion

2) Electrolyte Preparation

3) Electrowinning

4) Cementation

5) Product Filtration and Drying

The pilot facility did not conduct scale models of neutral salt crystallization or sodium sulfate manufacture. However, these are well known and clearly demonstrated technologies which can be handled with "off the shelf" packaged crystallizer units.

The major goal of the pilot plant program was to demonstrate that the process steps could be effectively downscaled as each step represents a technology which currently exists in a much larger scale somewhere in the U.S. or Europe.

The best exanple of this problem is the cell house operations. Similar copper cell houses of much greater size can be found in every major copper or zinc refinery in the world. The technical challenge for REOCNIEK was to reduce the scale of that technology to the appropriate size for the waste recycling industry without major losses in electrical or manpower efficiencies.


REOCNIEK has completed the licensing process for its first full scale facility in Newman, Illinois. With the assistance of its corporate parent PS Group, REOONTEK has sold $15 million in industrial revenue bends and will begin construction on or about July 1, 1989. We expect this facility to begin operation during the first quarter of 1990.

REOCNIEK has executed siting agreements for its seoend facility in Calhcun County, Florida. The Florida EER has placed special priorities on this project and expect to complete the permitting process within six months. Construction is expected to begin during the first quarter of 1990.

It would be noted that once siting was achieved, permitting could be expedited because the permit was identical to the one previously approved by the Illinois EPA and because of Florida's desperate need for such a facility, having been shut out of South Carolina and Alabama.

Soottsburg, Indiana is presently completing its siting process and REOCNIEK expects a siting agreement by July 15, 1989 and a permit within twelve months thereafter.

This will make Scottsburg the third of the REOCNTEK plants in operation with an expected start up date of July 1991.

REOCNTEK is in the final stages of site selection for its Arizona facility. We expect to occplete this siting agreement by September of 1989 with a facility start up to follow twenty-four months thereafter.


During the past two years, REOCNTEK has made two attenpts to site a facility in California. In both instances, the NIMBY (Not In My Backyard) syndrcme outweighed rational decision making by local ccranunities. REOCNIEK believes, however, that several factors nay lead to changes in the outlook for a recycling facility in California.

Other states, such as Arizona and Nevada are beginning to pass legislation which will make the recycling or disposal of waste by-products from out-of-state ocmpanies prohibitively expensive through differential taxation. If this legislation is successful, it may cause the plating and printed circuit board industries to either emigrate to those states where recycling is available or to force changes in California's social and legislative attitudes towards the siting of recycling facilities.

Recent federal court rulings have supported the ocnoept of recycling over local land use authorities (see Ogden Vs. city of San Diego). Such rulings may require the California legislature to re-think the efficiency of the Tanner Act as a means of siting recycling facilities.

In the interim it is our experience and reocnmendaticn that manufacturing industries re-think their need to locate in California.


F006 Sludges are the inevitable by-products of the plating and printed circuit board industries. Hydrcmetallurgy can provide an environmentally acceptable, eccncmically feasible means of recycling these by-products.

Those states which actively embrace the siting of such recycling facilities will provide for both healthier economies and envircrmerrts new arid in the future.

Treatment Opportunities

Going Green For More Cash

Going Green For More Cash

Stop Wasting Resources And Money And Finnally Learn Easy Ideas For Recycling Even If You’ve Tried Everything Before! I Easily Found Easy Solutions For  Recycling Instead Of Buying New And Started Enjoying Savings As Well As Helping The Earth And I'll Show You How YOU Can, Too! Are you sick to death of living with the fact that you feel like you are wasting resources and money?

Get My Free Ebook

Post a comment