FCDI Desalination Using Semiconductor Heterojunctions
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Solution Overview
Problem
Current flow-electrode capacitive deionization (FCDI) technologies face limitations in scalability and efficiency due to complex stack designs and the deterioration of ionic membranes, leading to high energy consumption and operational challenges in desalination processes.
Innovation Solution
A novel FCDI system employing multiple ultra-fine filter tubes and a cylindrical housing design with tubular membranes, allowing for continuous operation and reduced dependency on ionic membranes, utilizing carbon slurries that circulate through tubular membranes with parallel electrodes to enhance desalination efficiency and simplify scale-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional FCDI technologies use complex stack designs with ionic membranes, then desalination function is achieved, but device complexity increases and membranes deteriorate over time
Solution Approach 1:
The patent removes ionic membranes from the FCDI system entirely, replacing them with a heterojunction interface between n-type and p-type semiconductor layers. This extraction eliminates the complexity and deterioration issues associated with membranes while maintaining the ion separation function through the semiconductor heterojunction's internal electric field.
Solution Approach 2:
The patent replaces the mechanical/physical membrane structure with a semiconductor-based electrochemical system. The heterojunction interface creates an internal electric field that performs ion separation without requiring physical membranes, thereby reducing device complexity and improving reliability.
2Productivity
If high-pressure pumps are used in membrane processes, then desalination efficiency is improved, but energy consumption increases
Solution Approach 1:
The patent replaces mechanical pressure-driven membrane processes with an electrochemical system based on semiconductor heterojunctions. The internal electric field at the heterojunction interface drives ion separation and water splitting without requiring high-pressure pumps, significantly reducing energy consumption while maintaining desalination efficiency.
Solution Approach 2:
The patent changes the driving mechanism from mechanical pressure to electrochemical potential difference. By applying a relatively low external voltage to enhance the internal electric field at the heterojunction, the system achieves efficient ion separation and water splitting without the high energy input required by pressure-driven membrane processes.
3Reliability
If ionic membranes are used in FCDI systems, then ion separation is achieved, but membranes deteriorate leading to operational challenges
Solution Approach 1:
The patent completely removes ionic membranes from the system, replacing their ion separation function with the semiconductor heterojunction interface. This eliminates the deterioration problem inherent to membranes while maintaining reliable ion separation through the electrochemical reactions at the heterojunction.
Solution Approach 2:
The patent uses a composite semiconductor structure combining n-type and p-type layers to create the heterojunction. This composite material system provides durable, stable ion separation without the degradation issues of organic membranes, as semiconductors offer superior chemical and mechanical stability.
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 design achieves higher energy efficiency, more stable system performance, and simpler system design by reducing membrane degradation and complexity, enabling effective desalination of seawater and brackish water with improved salt removal efficiency.
Implementation Method 1
the n-type semiconductor layer and the p-type semiconductor layer are in contact with each other to form a heterojunction between the n-type semiconductor layer and the p-type semiconductor layer
Implementation Method 2
the internal electric field in the heterojunction spontaneously drives the water splitting reaction
Implementation Method 3
the internal electric field in the heterojunction spontaneously drives the water splitting reaction to generate hydrogen ions and hydroxide ions
Implementation Method 4
The hydrogen ions and the hydroxide ions are driven by a driving force of the internal electric field to migrate through the aqueous flow
Data Source
AI summary
The present disclosure describes a flow-electrode capacitive deionization (FCDI) desalination system and method of use. The system employs clusters of tubular membranes oriented parallel to each other, each membrane having an internal flow path capable of receiving an electrolyte slurry (carbon slurry) therethrough. Each tubular membrane further comprises an electrode coaxially extending through the entire length of the electrode. Preferably, adjacent electrodes within the cluster receive a positive or negative charge, respectively. The cluster of tubular membranes is nested within a flow chamber capable of receiving saline or brackish water to be flowed along the outside surfaces of the tubular membranes to cause selected ions, e.g., Na+, Cl— to pass through the membranes and into the carbon slurry circuit. The desalinated water then passes out of the flow chamber. The outer diameter of the electrodes can be optimized based on the inner diameter of the tubular membrane.