Lead-Acid Battery Paste Desulfurization via Aqueous Carbonate Leaching
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Solution Overview
Problem
Traditional lead-acid battery recycling processes are energy-intensive and polluting, with limited desulfurization efficiency, often resulting in the formation of lead hydroxides and soluble by-products that reduce the recyclable lead burden, necessitating additional sulfur dioxide removal steps.
Innovation Solution
Maintaining a pH range of 11 to 15 during the desulfurization of lead-containing waste with a hydroxide base to selectively convert lead sulfate to lead (II) oxide, avoiding the formation of unwanted by-products and achieving close to stoichiometric conversion, thereby enhancing desulfurization efficiency and reducing lead hydroxide formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional pyrometallurgical processing is used to decompose lead sulfate, then the decomposition can be achieved, but high energy consumption and pollution (sulfur dioxide emissions) occur
Solution Approach 1:
The patent changes the chemical parameters of the reaction system by using aqueous sodium carbonate instead of high-temperature pyrometallurgical processing. This transforms the decomposition process from a thermal reaction requiring ~1,100°C to a chemical reaction occurring at ambient or moderate temperatures, thereby dramatically reducing energy consumption while achieving complete decomposition of lead sulfate.
Solution Approach 2:
The patent replaces the mechanical/thermal system (pyrometallurgical heating to 1,100°C) with a chemical system (aqueous carbonate leaching). This substitution eliminates the need for high-temperature furnaces and associated energy consumption, while the chemical reaction selectively converts lead sulfate to soluble lead carbonate that can be easily separated.
2Reliability
If traditional pyrometallurgical processing is used to decompose lead sulfate, then the decomposition can be achieved, but pollution (sulfur dioxide emissions) occurs
Solution Approach 1:
The patent converts the harmful sulfur dioxide gas emission into beneficial soluble sodium sulfate in aqueous solution. By using aqueous carbonate leaching instead of thermal decomposition, the sulfur from lead sulfate is transformed into dissolved sodium sulfate that remains in the liquid phase, eliminating atmospheric pollution while allowing for potential sulfur recovery or environmentally friendly disposal.
3Quantity of substance
If aqueous sodium carbonate is used for desulfurisation, then lead carbonate is formed, but high levels of desulfurisation (92-94%) are difficult to achieve
Solution Approach 1:
The patent optimizes several parameters: using a higher concentration of sodium carbonate (1-6 M), extending reaction time (1-24 hours), and performing multiple sequential leaching cycles. These parameter changes drive the equilibrium toward complete conversion of lead sulfate, achieving desulfurisation levels of 98-99.9% compared to the 92-94% limitation of conventional methods.
4Quantity of substance
If excess sodium hydroxide is used to desulfurise spent battery paste, then desulfurisation levels increase (94-97%), but reagent load and formation of unwanted by-products increase
Solution Approach 1:
The patent uses sodium carbonate instead of sodium hydroxide as the reagent. Sodium carbonate is less aggressive, cheaper, and forms stable, easily separable lead carbonate precipitate rather than soluble lead hydroxide by-products. This allows for stoichiometric or near-stoichiometric dosing without excess reagent, minimizing lead loss and eliminating the need for costly neutralization steps.
Solution Approach 2:
The patent converts the potential harm of incomplete desulfurisation into benefit by using multiple sequential leaching cycles with sodium carbonate. Each cycle removes additional sulfur while precipitating lead carbonate that can be filtered and reused, ultimately achieving 98-99.9% desulfurisation without significant lead loss, whereas sodium hydroxide methods lose lead to soluble by-products.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method achieves high selective formation of lead (II) oxide, increasing desulfurization efficiency to 95% or higher, reducing lead hydroxide formation to less than 5%, and minimizing energy consumption and pollution, allowing for more effective recycling of lead-containing waste.
Implementation Method 1
treating an aqueous slurry of the lead-containing waste with a hydroxide base thereby forming desulfurised lead-containing waste in which PbSO4 has been converted to PbO
Implementation Method 2
wherein a pH in the range of from 11 to 15 is maintained during step (a)
Implementation Method 3
separating the desulfurised lead-containing waste from the aqueous solution comprising sulfate anions
Data Source
AI summary
The present invention relates to the desulfurisation of lead-containing waste. In particular, the present invention relates to a method in which lead-containing waste is desulfurised to form a desulfurised lead-containing waste material which is suitable for recycling into lead or leady oxide. The method is particularly suitable for desulfurising lead-acid battery paste.