Ground Calcium Carbonate Brightening via Persulfate Oxidation
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Solution Overview
Problem
Existing methods for brightening ground calcium carbonate (GCC) are ineffective, as they either require acidic conditions that damage the mineral or achieve only modest improvements in brightness, limiting the availability of high-brightness calcium carbonate for industrial use.
Innovation Solution
A chemical processing method involving the use of persulfate under basic conditions, combined with heating and mixing, to increase the GE brightness of GCC by 8 points, from less than 80 to above 80, by creating a basic slurry with a hydroxide and deionized water, agitating, filtering, washing, and drying the calcium carbonate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If traditional chemical treatment methods are used to brighten GCC, then some brightness improvement may be achieved, but the mineral structure is damaged due to acidic conditions
Solution Approach 1:
The patent changes the pH parameter from acidic (traditional method) to basic (pH 9-11 using sodium hydroxide), which allows brightness improvement while preserving the calcium carbonate mineral structure. This parameter inversion resolves the contradiction by finding a basic condition range that achieves both brightness enhancement and structural integrity.
Solution Approach 2:
The patent uses persulfate as a strong oxidizing agent under basic conditions to remove color bodies and brighten the GCC. The persulfate oxidizes organic and inorganic color impurities without damaging the calcium carbonate structure when used in the basic pH range, thereby achieving brightness improvement while maintaining mineral integrity.
2Illumination intensity
If PCC is used instead of GCC to achieve high brightness, then brightness level is improved, but manufacturing cost increases due to additional processing steps
Solution Approach 1:
The patent applies parameter changes (pH 9-11, temperature 40-80°C, persulfate concentration) to GCC to achieve high brightness (≥90 GE scale) without requiring the additional processing steps needed for PCC production. This allows GCC to reach PCC-level brightness while maintaining lower manufacturing costs associated with simpler processing.
Solution Approach 2:
The patent effectively creates a PCC-like brightness result using GCC as the starting material. By applying the basic persulfate treatment, the GCC achieves brightness levels comparable to PCC, copying the desirable optical property without requiring the complex precipitation process used to manufacture PCC.
3Illumination intensity
If flotation or magnetic separation is used to remove color bodies, then some brightness improvement is achieved, but the process complexity increases
Solution Approach 1:
The patent replaces mechanical separation methods (flotation and magnetic separation) with a chemical treatment process using persulfate under basic conditions. This chemical approach achieves brightness improvement through oxidation of color bodies in a simpler, more direct process that does not require complex mechanical separation equipment or multiple processing stages.
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
The method effectively increases the GE brightness of GCC from light grey to white, achieving a significant improvement in whiteness, making the process more economically viable for producing high-brightness calcium carbonate.
Implementation Method 1
adding a persulfate to the slurry to form an intermediate slurry
Implementation Method 2
heating the basic slurry to a temperature of between 60° C. and about 85° C.
Implementation Method 3
mixing the calcium carbonate with a base and deionized water of about 1 to 3 by weight to produce a basic (pH>7) slurry
Data Source
AI summary
A chemical processing method to increase the brightness of a naturally sourced GCC. The process described herein employs a persulfate under certain heating and stirring conditions to effect a brightness change which can be on the order of about 8 points on the GE brightness scale and can move a GCC which is under a GE level of 80 to above a GE level of 80.