Alkaline Rinse Water Tin Removal via pH Adjustment and Filtration
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Solution Overview
Problem
Current methods for treating alkaline rinsing water from circuit board production with high levels of dissolved and/or undissolved tin are costly and inefficient, often requiring frequent regeneration of ion exchangers and failing to meet strict wastewater regulations due to limited solubility and separability of precipitates.
Innovation Solution
A method involving acidification of the rinsing water to a pH of 4.5 to 6.5 to precipitate tin hydroxide, followed by mechanical filtration and subsequent ion exchange using a cellulose matrix ion exchanger to reduce tin content below 2 mg/l, effectively addressing the inefficiencies and high costs of existing technologies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ion exchangers are used to remove tin from rinsing water, then tin content can be reduced below limit values, but service life of ion exchangers is short due to tin complexes
Solution Approach 1:
The patent applies preliminary action by adjusting the pH of rinsing water to 4.5-6.5 before the ion exchange process. This pre-treatment step converts tin complexes into tin hydroxide precipitates, which are then removed by coagulation and filtration. By performing this preparation in advance, the ion exchangers are protected from rapid degradation by tin complexes, thereby extending their service life while maintaining effective tin removal capability.
2Ease of operation
If precipitation reactions are used to remove heavy metals, then neutralization can be achieved, but purification is insufficient due to limited solubility and separability of precipitates
Solution Approach 1:
The patent merges multiple treatment steps into a integrated process: pH adjustment to 4.5-6.5, coagulation aid addition, precipitation, and filtration are combined in sequence. This combination allows the precipitates to be formed under optimized conditions and then efficiently separated, achieving both easy operation and high purification efficiency that neither step could achieve alone.
3Manufacturing precision
If strict wastewater regulations are complied with, then discharge requirements are met, but treatment costs are great
Solution Approach 1:
The patent applies parameter changes by optimizing the pH range to 4.5-6.5, which is specifically designed to maximize tin hydroxide precipitation while minimizing costs. This precise parameter control ensures that tin is effectively removed to meet the 2 mg/l discharge limit without requiring excessive chemical additives or multiple treatment stages, thereby achieving compliance at reduced cost.
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 allows for cost-effective treatment of alkaline rinsing water, meeting stringent wastewater requirements by significantly extending the service life of ion exchangers and reducing total tin and other heavy metal content, thereby enabling indirect discharge into public sewage systems.
Implementation Method 1
the rinse water (a) in a first step to a pH in the range from 4.5 to 6.5 to precipitate a tin hydroxide by adding an inorganic non-oxidizing acid sets
Implementation Method 2
the according to step (a) coagulate the tin hydroxide precipitate obtained
Implementation Method 3
the tin hydroxide precipitated according to step (b) with a me mechanical filter cascade separates and (c)
Implementation Method 4
subjecting the filtrate to an ion exchange process with an ion exchange with a cellulose matrix and fixing groupsto eliminate the total tin content
Data Source
AI summary
The method comprises adjusting pH value of dish water to 5.0-6.0 by the supply of phosphoric acid for precipitating tin hydroxide, coagulating the tin-hydroxide precipitation, separating the tin hydroxide by a mechanical filter cascade and subjecting the filtrate to ions exchange process for eliminating total content of tin up to 2 mg/liter. The dish water is prepared from the printed circuit board- production, fabrication and/or mounting. The coagulation is carried out for 15 minutes at room temperature. The iron exchanger uses with a cellulose matrix and fixing groups.