Lignocellulosic Carbon Adsorbent with Low Phosphorus
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Solution Overview
Problem
There is a need for high surface area, high microporosity, or high mesoporosity activated carbon materials with low levels of phosphorus and other impurities, which are relatively inexpensive to produce, especially for applications where residual impurities can be detrimental, such as water treatment and electrochemical applications.
Innovation Solution
The development of chemically activated lignocellulosic carbon materials using phosphoric acid activation, which results in materials with high surface area, microporosity, or mesoporosity, and significantly reduced impurity levels, including phosphorus, through secondary treatment steps such as steam treatment and acid washing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If phosphoric acid activation is used to produce high surface area activated carbon, then BET surface area increases (>1300 m2/g), but phosphorus impurity levels increase (1600-10000 ppm)
Solution Approach 1:
The patent extracts and removes phosphorus impurities from the activated carbon material through a washing process. The activated carbon is washed with a liquid (such as water or an organic solvent) to remove residual phosphoric acid and phosphorus compounds, thereby reducing phosphorus content while preserving the high surface area achieved during activation.
Solution Approach 2:
The patent changes the chemical composition parameters of the activated carbon by controlling the activation process and subsequent washing. By adjusting activation conditions (temperature, time, activator concentration) and washing parameters (liquid type, flow rate, contact time), the patent optimizes both surface area and phosphorus content to achieve the desired balance.
2Area of stationary object
If chemical activation is used to increase surface area, then BET surface area increases and micropore volume increases, but production cost increases due to additional washing steps
Solution Approach 1:
The patent performs preliminary washing during the activation process itself, rather than as a separate subsequent step. The activated carbon is washed with liquid during or immediately after the activation treatment, which prevents phosphorus accumulation while maintaining the high surface area and micropore structure, thereby avoiding additional costly washing steps later.
Solution Approach 2:
The patent uses a liquid intermediary (washing solution) to remove phosphorus impurities without affecting the activated carbon's porous structure. The liquid serves as a mediator that selectively removes phosphorus while preserving the high surface area and micropore volume achieved during activation, enabling cost-effective production.
3Volume of stationary object
If thermal activation is used to produce microporous carbon, then micropore volume increases (>60%), but BET surface area decreases (<1000 m2/g)
Solution Approach 1:
The patent creates a composite porous structure combining micropores and mesopores in the activated carbon material. By controlling the activation process and using appropriate activators, the patent develops a dual-pore system where micropores provide high surface area contribution while mesopores provide structural stability and accessibility, achieving both high micropore volume (>60%) and high BET surface area (>1300 m2/g).
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 resulting activated carbon materials demonstrate high surface area, desirable porosity, and low impurity levels, particularly in phosphorus content, making them suitable for applications requiring low residual impurities while maintaining high adsorption capacity and porosity.
Implementation Method 1
Chemical activation is more commonly done with lignocellulosic raw materials and activation agents such as an acid, strong base or salt (e.g., phosphoric acid, nitric acid, hydrochloric acid, sulfuric acid, potassium hydroxide, sodium hydroxide, potassium carbonate, calcium chloride, zinc chloride). It is typically a lower temperature, higher yield process and often results in activated carbons with a higher surface area than thermally activated carbons.
Implementation Method 2
The thermal activation process commonly uses high temperature and steam and/or treatment with oxidizing gas (e.g., CO2 or O2) to carbonize and cat away at the raw material and create porosity.
Implementation Method 3
Activated carbons are characterized by a large specific surface area, typically 500-2500 m2/g. These carbons are used in a wide variety of applications, including water treatment for removing of large taste and odor compounds and decolorization of food ingredients, beverages, chemicals, and pharmaceuticals.
Data Source
AI summary
Presently described are chemically activated lignocellulosic carbon adsorbent materials comprising high surface area, high microporosity, and low impurities, and methods of making the same. The described structures provide unexpected advantages as compared to currently available materials.