Flow Electrode Capacitive Deionization for Phosphorus Recovery
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Solution Overview
Problem
Current methods for treating phosphogypsum leachate are inefficient, requiring large amounts of chemical agents, resulting in high treatment costs, significant waste residue generation, and low phosphorus recovery efficiency.
Innovation Solution
A flow electrode capacitive deionization system is developed, comprising a phosphorus recovery electrodeionization module and a desalination electrodeionization module, which selectively separates phosphorus from phosphogypsum leachate and rapidly desalines brine, reducing the need for chemical reagents and minimizing waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If chemical precipitation method is used to treat phosphogypsum leachate, then phosphorus can be recovered, but large amounts of chemical reagents (lime, sulfuric acid) are consumed and treatment costs increase
Solution Approach 1:
The patent replaces the chemical precipitation method with a flow electrode capacitive deionization system that uses electrostatic fields instead of chemical reagents. The system employs ion exchange membranes and electrical energy to selectively remove phosphorus and other ions from the leachate, eliminating the need for large amounts of lime and sulfuric acid reagents while maintaining high phosphorus recovery efficiency
Solution Approach 2:
The patent changes the treatment mechanism from chemical parameter adjustment (pH control using lime and sulfuric acid) to physical-electrical parameter control. By applying voltage across ion exchange membranes, the system controls ion migration through electrical fields, achieving phosphorus removal without chemical reagent consumption and reducing treatment costs
2Quantity of substance
If membrane filtration process is used to remove ammonia nitrogen, then ammonia can be removed, but membranes are easy to clog and operation and maintenance costs are high
Solution Approach 1:
The patent replaces membrane filtration with a flow electrode capacitive deionization system that uses electrical fields and ion exchange membranes. The system removes ammonia nitrogen through electrostatic attraction and ion migration, avoiding the mechanical filtration process that causes membrane clogging. The flow electrode design allows for easier maintenance and lower operation costs while maintaining effective ammonia removal
3Quantity of substance
If coagulation pretreatment and ultrafiltration are used to concentrate phosphorus and fluorine, then resources can be concentrated, but fluorine and heavy metals continuously enrich and this is not conducive to phosphoric acid production
Solution Approach 1:
The patent uses flow electrode capacitive deionization to control the concentration of multiple ions simultaneously. By applying electrical fields across selectively permeable membranes, the system can concentrate phosphorus while controlling the enrichment of fluorine and heavy metals. The electrical parameter control allows for selective ion migration, preventing harmful enrichment while maintaining resource concentration for phosphoric acid production
4Quantity of substance
If pH adjustment range of 3 to 12 is used for selective precipitation, then multiple resources can be recovered, but large amounts of acid and alkali reagents are consumed and operating costs increase
Solution Approach 1:
The patent replaces chemical pH adjustment with electrical field control in the flow electrode capacitive deionization system. Instead of using acid and alkali reagents to adjust pH for selective precipitation, the system uses electrical fields to control ion migration and precipitation. This substitution eliminates the consumption of large amounts of chemical reagents while maintaining the ability to selectively recover multiple resources from the leachate
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 system achieves over 97% removal of phosphate from phosphogypsum leachate, converting it into high-purity vivianite products, while significantly reducing chemical reagent usage, waste generation, and energy consumption, thereby providing economic and environmental benefits.
Implementation Method 1
Flow electrode capacitive deionization (FCDI) is a desalination technology based on the principle of supercapacitors
Implementation Method 2
A first anion exchange membrane is provided between the phosphorus recovery electrodeionization module anode flow electrode chamber and the phosphorus recovery electrodeionization module deionization chamber. A first cation exchange membrane is provided between the phosphorus recovery electrodeionization module cathode flow electrode chamber and the phosphorus recovery electrodeionization module deionization chamber.
Implementation Method 3
The positively charged nitrogen and negatively charged phosphorus in the wastewater enter the nitrogen recovery chamber and phosphorus recovery chamber respectively through the cation and anion ion exchange membranes under the action of the electric field
Data Source
AI summary
A flow electrode capacitive deionization system and a method for recovering phosphorus in phosphogypsum leachate and synchronous performing brine desalination belong to the technical field of wastewater treatment and recycling. The flow electrode capacitive deionization system includes a phosphorus recovery electrodeionization module and a desalination electrodeionization module. A first flow electrode solution reservoir, a phosphorus recovery electrodeionization module cathode flow electrode chamber, and a desalination electrodeionization module anode flow electrode chamber are interconnected in a circulation. A second flow electrode solution reservoir, a phosphorus recovery electrodeionization module anode flow electrode chamber, and a desalination electrodeionization module cathode flow electrode chamber are interconnected in a circulation. Two independent flow electrode solution circulation loops are formed. The phosphogypsum leachate enters the phosphorus recovery electrodeionization module and phosphorus is enriched into a flow electrode solution. A phosphorus-rich solution is reacted with a ferrous solution under an oxygen-free condition to generate vivianite [Fe3(PO4)2·8H2O].