Lead Oxide Recovery via Redox Slurry Purification
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Solution Overview
Problem
Current methods for recovering high purity lead oxides from impure lead compounds, such as those found in lead acid battery pastes, are energy intensive and polluting, requiring smelting and acid fluxing processes that are costly and environmentally detrimental.
Innovation Solution
A process involving the slurry of waste lead products in an acidic medium with the addition of alkali metal halide salts to reduce lead to a +2 valence state, followed by filtration, washing, and treatment with alkali hydroxide to produce high purity lead oxide, effectively removing contaminants like antimony, arsenic, and barium without smelting or fluxing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If smelting and acid fluxing processes are used to recover lead oxide, then high purity lead oxide can be produced, but energy consumption increases and environmental pollution worsens
Solution Approach 1:
The patent changes the chemical parameters by using controlled oxidation-reduction reactions with specific reagents (halide salts, alkali hydroxide) at moderate temperatures, replacing the high-temperature smelting process. This transforms the recovery process from energy-intensive thermal processing to chemically-controlled transformation, achieving high purity PbO with reduced energy consumption.
Solution Approach 2:
The patent replaces the mechanical/thermal smelting system with a chemical reaction system. Instead of using high temperature and physical separation methods, the invention employs sequential chemical reactions (reduction with halide salts, followed by oxidation with alkali hydroxide) to transform lead compounds, substituting mechanical energy input with chemical transformation.
2Manufacturing precision
If smelting and acid fluxing processes are used to recover lead oxide, then high purity lead oxide can be produced, but environmental pollution increases
Solution Approach 1:
The patent converts the harmful impurities (sulfates, halides, metal contaminants) present in waste battery paste into beneficial elements of the purification process. The halide salts used in reduction step and alkali hydroxide in oxidation step systematically transform impurities into soluble forms that can be removed, converting the waste material's harmful characteristics into a controlled chemical transformation process that yields high purity product.
Solution Approach 2:
The patent introduces intermediary substances (halide salts as reducing agents, alkali hydroxide as oxidizing agent) that mediate the transformation of lead compounds. These intermediaries enable controlled oxidation-reduction reactions that selectively transform lead compounds to the desired oxidation state while allowing impurities to be systematically removed through filtration and washing, avoiding direct smelting pollution.
3Quantity of substance
If conventional smelting processes are used, then lead can be recovered, but the process becomes costly and requires hazardous waste disposal
Solution Approach 1:
The patent employs a self-service approach where the waste battery paste itself serves as the raw material for the chemical transformation. The process uses readily available reagents (halide salts, alkali hydroxide) that can be easily obtained, and the transformation occurs in a simple sequential manner without requiring complex smelting equipment or hazardous waste disposal infrastructure, making the process more cost-effective.
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 process achieves high purity lead oxide (>99.7%) with reduced energy consumption and minimal environmental impact by directly converting mixed lead compounds into lead oxide, removing difficult-to-remove contaminants, and recycling chlorine gas as bleach.
Implementation Method 1
adding sufficient alkali metal halide salt to reduce all lead to a valence of +2
Implementation Method 2
treating the filter cake from Step D with an alkali hydroxide solution, preferably sodium hydroxide or potassium hydroxide
Data Source
AI summary
A process for producing high purity lead oxide from impure lead compounds particularly from waste lead battery paste which includes an oxidation-reduction step. The process results in a reduction of impure lead compounds to the +2 valence state and metal particle contaminants are oxidized to the +2 state.