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A Pproject partially founded by the European Union within the “GROWTH PROGRAMME”. This three year Pproject had a duration of three years, and it has been was successfully completed in accomplished on April 2004.





Técnicas Reunidas S.A. (ES), Britannia Refined Metals Ltd (UK), Orzel Bialy S.A. (PL), Instytut Metali Niezelaznych (PL), Coventry University (UK), Lafarge Plasterboard Ltd (UK), Faculdade de Ciéncias da Universidade de Lisboa (P), Netherlands Organisation for Applied Scientific Research (NL), Magneto Special Anodes B.V. (NL), Membraan Applicatie Centrum Twente (NL), Kovohute Prĭbram A.S. (CZ), Institute for Nonferrous and Rare Metals (RO)




Secondary lead consumption is certain bound to raise due to an ever increasing demand for lead acid batteries for the demand for automotive industry, and also related to new uses such as the electric vehicles andor hybrid vehicles, solar and renewable energy storage and, portable and auxiliary batteries in emergency systems, etc.


The lead battery recycling industry currently faces the challenge of improving the conventional processes aiming to avoid toxic wastes generation (slags, mattes, etc) generation and  trying to complying with the more stricter environmental regulations.


The CLEANLEAD pProcess provides a new, low energy cost, zero-waste generation sustainable option which can substantially improve substantially the current lead smelting operations. The new process has been developed to deal efficiently with the whole batteriesy components, includinge.g. drained acid treatment, optimisation of the smelting stage and hydrometallurgical treatment of the battery pastes.



Cleanlead Process Conceptual Diagram





The CLEANLEAD Process for drained acid treatment not only prevents the current production of sludge for disposal from being produced, but also turns the acid into reusable products. Depending on the applied process option, commercial synthetic gypsum, or acid for new batteries may be produced refilling or biotreatment may be used on theof effluents can be performed. This wide range of purposes options makes the described technology applicable suitable for to many different cases applications and industrial problems.


Commercial Gypsum Production




Detail of the gypsum product


Current processes turn the drained acid containing metallic impurities into a waste sludge for disposal by adding lime or sodium hydroxide. This treatment has severeimplies associated environmental costs. The CLEANLEAD Process makes commercial synthetic gypsum through drained acid purification by means of membrane techniques such as diffusion dialysis and nanofiltration or chemical  precipitation prior to lime addition. The CLEANLEAD synthetic gypsum fits complies with the specifications to be used asfor feed material in the plasterboard industry, as an additive in the cement industry and also in floorscreeds manufacturing since the process can be conducted adjusted to get different gypsum products. Besides environmental advantages, producing commercial gypsum versus in place of an acid sludge is economically attractive.



Obtaining reusable battery acid


presents attractive economic revenue.


Membrane Electrolysis cell


The Ddeveloped electrochemical process allows obtaining can produce a clean and concentrated sulphuric acid (30% w/w) suitable for filling new batteries refilling through . This is achieved with electrodialysis technology, yielding efficient removal of the metallic impurities.


Biological treatment




The CLEANLEAD Process also provides includes biotreatment of drained acid blended with other industrial alkaline effluents (landfill leachates, etc) by means of biologically produced H2S to remove the impurities and yield getting finally a non non-polluting final productstream.





Improved Operation


Rotary Furnace


Desulphurised battery paste smelting methods were developed within the CLEANLEAD project as an alternative to conventional raw paste smelting. Very positive results have been obtained in trials performed in a 500 kg rotary furnace, which are summarised as follows:



Ddecreaseding smelting temperature up down to 900 ºC

• 3-4 times shorter smelting time

Sslag amount reduction by 65-75%

Sstable silica slag type being produced

Rreducedtion consumption of fluxes and reductants consumption

Llead bullion yield up to 75% of the charge mass

Ddusts volume reduction and low SO2 emission


Producing Stable Slag














            Electric Furnace                                                            Isasmelt Furnace


Further achievements on preventing unstable slag from being produced are available within the CLEANLEAD technology.  Conventional unstable sodium-based slag can be re-smelted in an electric arc furnace. Tests carried out in a 80 kVA pilot unit confirm that re-smelting of soda slag in the presence of iron oxides and sand produces non-toxic stable ferrosilicate slag. In addition, some matte is generated, which reduces SO2 emissions.

Another way developed process uses deals with using the sodium sulphate slag from an Isasmelt furnace as flux in athe rotary furnace. In tests Tthis slag performed as well as the currently used sodium carbonate flux and therefore can replace it, thus reducing the operating cost.




The technological innovations described above have been integrated in the CLEANLEAD optimised smelting process, which providespresents great flexibility and important improvements to suit local operating requirements. The gathered benefits of the optimised smelting processes are:


·        ØStable ferrosilicate slag is produced complying withwithin current and future environmental regulations is produced, avoiding the current generation of unstable and toxic sodium-based slag.

·        ØElimination or substantial reduction of SO2 gas emission.

·        ØDecreaseding energy consumption and total operating costs.

·        Ø Improveding process performance and environmental aspects impact of furnace operations.




A Novel Process as an Advantegous Optiona Preferred Alternative to Smelting




Lead Electrowinning Pilot Cell


A novel process under in the CLEANLEAD technology deals with the hydrometallurgical treatment of battery paste to obtain pure Pb. This approach stands as is an advantageous superior alternative option to smelting and offers zero waste and low cost sustainable technology.



An Eco-efficient and Low Cost Technology


In this process, battery paste is reduced and desulphurised to render it suitable for feeding a low energy lead electrolytic process. Reduction is carried out by adding drained battery drained acid together with a small amount of lead bearing sulphides such as mattes, concentrates, fumes, etc., as reducing agents, which givesinvolve lower costs and an extra amount of improved lead recovery eventually recovered. The desulphurisation is performed with sodium hydroxide, which is regenerated in a subsequent step. This saves consumable the cost of consumables and produces valuable gypsum. Desulphurised paste is leached with sodium hydroxide at 60 ºC, and then the pregnant solution containing dissolved lead passes to lead electrowinning in alkaline media, having an energy requirement of 0.5 kWh/kg Pb and current efficiencies close to 100%. The developed electrolytic process shows important technical and environmental advantages, and offers present lower operating costs than conventional lead smelting technology.



Vesatility of Products


As an alternative to lead electrowinning, the CLEANLEAD pProcess also allows pure Lead Oxide production at very competitive cost, which is suitable for new pastes the manufacturing of new pastes or other industrial applications.


The CLEANLEAD Process represents a radical innovation and definitive solution to the current problems the secondary lead industry is presently facing in Europe and worldwide.

The new technologies deal efficiently with all battery components, e.g. drained acid, metallic lead, and pastes, proposing providing the best solution infor every case.


Sustainability is a must for is fundamental to the developed CLEANLEAD process, by pursuing zero-waste emissions, getting obtaining substantial savings in operating and environmental costs, and producing reusable valuable products instead of toxic wastes or slags generated by conventional smelting processes.


High quality and diversified products can be obtained, such as pure lead oxide, pure electrolytic lead, commercial gypsum, etc.


The Pprocess provides versatility and flexibility, which can be implemented as a whole or step by step, and easy to be easily adapted to local industrialy conditions and requirements.



Calle Sierra Nevada, 16 - San Fernando de Henares - 28830 Madrid (SPAIN)

Phone: 34 91 6558780; Fax: 34 91 6558789; E-mail: