Fibril Cellulose Dewatering via pH Adjustment
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Solution Overview
Problem
Fibril cellulose hydrogels have high water retention due to hydrogen bonds, making conventional water removal methods like filtration and evaporation inefficient, and the dried material is non-redispersible, limiting its transport and application in desired concentrations.
Innovation Solution
Lowering the pH of anionically charged fibril cellulose gels to pH 2-3 converts dissociated acid moieties to their acid form, reducing water retention and enabling mechanical dewatering through pressure filtration, while maintaining redispersability by controlling the drying process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional filtration or evaporation is used to remove water from fibril cellulose hydrogel, then water content is reduced, but the process becomes extremely slow due to dense nanoscale membrane formation that blocks water diffusion
Solution Approach 1:
The patent applies parameter changes by modifying the chemical state of acid moieties through pH control. By lowering pH below the pKa value, dissociated acid moieties are converted to their protonated form, which fundamentally changes the water retention capacity of the fibril cellulose, enabling efficient mechanical dewatering that was previously impossible.
Solution Approach 2:
The patent employs preliminary action by adjusting the pH of the fibril cellulose suspension before the dewatering process. This pre-treatment step converts acid moieties to their acid form, reducing water retention capacity in advance, which enables subsequent rapid mechanical separation through pressure filtration without the slow diffusion-limited processes.
2Quantity of substance
If fibril cellulose is dried to high concentration, then transport costs decrease, but the material becomes non-redispersible due to permanent fibril aggregation
Solution Approach 1:
The patent maintains redispersibility by controlling the pH parameter throughout the concentration and drying process. By keeping pH below the pKa value, the acid moieties remain in their protonated form, preventing permanent aggregation. This parameter control allows the material to be concentrated to high levels while retaining the ability to redisperse when needed.
Solution Approach 2:
The patent replaces conventional drying methods that cause permanent aggregation with a controlled pH-based concentration process followed by mechanical dewatering through pressure filtration. This substitution of the dewatering mechanism, combined with pH control, achieves high concentration while preserving redispersibility that would otherwise be lost in traditional drying processes.
3Quantity of substance
If pH is lowered to convert dissociated acid moieties to acid form, then water retention capacity is reduced and dewatering becomes feasible, but additional processing steps are required
Solution Approach 1:
The patent merges the pH adjustment step with the existing fibril cellulose production process. By integrating the acidification step into the manufacturing workflow and using the same equipment for both production and pH adjustment, the process complexity is minimized while achieving the desired reduction in water retention capacity.
Solution Approach 2:
The patent employs self-service by using the fibril cellulose production process itself to facilitate the pH adjustment and dewatering. The system leverages its own operational framework, requiring minimal additional external equipment or complex interventions, thereby reducing overall process complexity while achieving effective water retention control.
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 effectively concentrates fibril cellulose to 10-30 wt-% dry substance content, allowing for efficient transport and redispersability, overcoming the challenges of water retention and non-redispersibility in fibril cellulose processing.
Implementation Method 1
lowering the pH of the aqueous fibril cellulose gel below the pKa value of the anionically charged fibril cellulose to pH 2-3
Implementation Method 2
the anionic charge comprises dissociated acid moieties... lowering the pH... such that the dissociated acid moieties are converted to acid form
Implementation Method 3
dewatering the aqueous fibril cellulose gel of reduced water retention capacity in a pressure filtration step where positive pressure is applied
Implementation Method 4
Strong water retention is typical for fibril cellulose since water is bound to the fibrils through numerous hydrogen bonds
Data Source
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AI summary
Method for processing fibril cellulose which is in the form of aqueous fibril cellulose gel comprises - lowering the pH of the aqueous fibril cellulose gel to provide aqueous fibril cellulose gel of reduced water retention capacity, and - dewatering the aqueous fibril cellulose gel of reduced water retention capacity to provide dewatered fibril cellulose. The dewatering is performed by pressure filtration.