Lead Paste Pretreatment for Low-Dilution Electrochemical Recovery

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Solution Overview

Problem

Existing lead recycling processes face challenges with lead dioxide accumulation, electrolyte contamination, and dilution, particularly in smelterless recycling of lead acid battery paste, which affects the efficiency and cost of lead recovery.

Innovation Solution

A method involving washing and heating of desulfurized lead paste to reduce residual water and convert lead dioxide to lead oxide, followed by combination with a recycled electrolyte for electrochemical lead recovery, thereby reducing electrolyte loss and lead dioxide build-up, and maintaining electrolyte concentration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If lead paste is leached with aqueous solutions (ammonium chloride, hydrogen peroxide) to reduce lead dioxide, then lead dioxide quantities are substantially reduced, but water requirement is not insignificant and the presence of water dilutes the electrolyte, thereby increasing the need for and cost of electrolyte

Engineering Contradiction:

Improvelead dioxide quantityVSAvoidelectrolyte dilution

Core Design Contradiction:

Quantity of substanceVSLoss of substance

Solution Approach 1:

The patent applies preliminary thermal treatment (heating to 50-150°C) to the desulfurized lead paste before electrolytic leaching. This pre-heating step converts lead dioxide to lead oxide and reduces residual water content, so that when the paste subsequently undergoes aqueous leaching, less water is required and electrolyte dilution is minimized. The preliminary action prepares the material in advance to avoid the harmful effect of excessive water demand during the main process.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If desulfurized lead paste is processed using conventional electrolytic methods, then metallic lead is recovered, but lead dioxide accumulates in the electrolyte and electrolyte contamination occurs

Engineering Contradiction:

Improvemetallic lead recoveryVSAvoidlead dioxide accumulation and electrolyte contamination

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent changes the temperature parameter of the electrolytic leaching process, conducting it at elevated temperatures of 50-150°C rather than at ambient temperature. This temperature parameter change enhances the solubility of lead compounds in the electrolyte, improves lead recovery efficiency, and prevents lead dioxide accumulation by facilitating its reduction and dissolution, thereby reducing electrolyte contamination.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs a composite electrolyte system combining ammonium chloride and hydrogen peroxide. The ammonium chloride provides chloride ions for lead complex formation, while hydrogen peroxide acts as an oxidizing agent to manage lead dioxide. This composite chemical system works synergistically to achieve efficient lead recovery while preventing lead dioxide accumulation and electrolyte contamination.

Inventive Principle:

Principle #40Composite materials

3Productivity

If fluorine containing electrolyte (fluoboric or fluosilic acid) is used for lead recovery, then lead can be recovered in metal form, but the process becomes equally problematic due to electrolyte management issues

Engineering Contradiction:

Improvelead recoveryVSAvoidelectrolyte management complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent replaces expensive and problematic fluorine-containing electrolytes with a cheaper, more manageable ammonium chloride-based electrolyte system. While fluorine-containing electrolytes offer good lead recovery, they create significant management challenges and costs. The ammonium chloride system provides comparable lead recovery performance with simpler, lower-cost electrolyte management, effectively substituting a complex system with a simpler alternative.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 approach effectively recovers metallic lead with high purity while minimizing electrolyte dilution and lead dioxide accumulation, enhancing the efficiency and sustainability of the recycling process.

Implementation Method 1

heating the washed desulfurized lead paste to reduce the residual water to equal or less than 10 wt % and to reduce at least 50% of the lead dioxide to lead oxide

Methodology Applied

Scientific EffectThermal decomposition: Decomposition (biological)

Implementation Method 2

the lead ion enriched electrolyte is subjected to an electrochemical lead recovery operation to thereby recover metallic lead on a cathode

Methodology Applied

Scientific EffectElectrodeposition: Electrodeposition

Data Source

PatentUS20230313400A1Systems And Methods For Aqueous Recovery Of Lead From Lead Acid Batteries With Reduced Electrolyte Demand

Publication Date: 2023.10.05 AQUA METALS INC

AI summary

Lead is recovered from lead paste of a lead acid battery in a continuous and electrochemical lead recovery process. In especially preferred aspects, lead paste is processed to remove residual sulfates, and the so treated lead paste is subjected to a thermal treatment step that removes residual moisture and reduces lead dioxide to lead oxide. Advantageously, such pretreatment will avoid lead dioxide accumulation and electrolyte dilution.