Fluidized Bed Reactor for Selenate Removal
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Solution Overview
Problem
Current technologies lack a cost-effective and reliable method for treating flue gas desulfurization (FGD) wastewater, particularly in removing toxic metals like selenium and mercury, due to the complexity and variability of the wastewater composition.
Innovation Solution
A fluidized bed reactor system using a hybrid reactive solid composed of zero valent iron and magnetite, combined with ferrous iron as a secondary reagent, effectively reduces selenate to insoluble selenium species and adsorbs or precipitates other toxic metals like arsenic and mercury onto iron oxide sludge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional wastewater treatment methods are used, then general contaminant removal is achieved, but toxic metals like selenate and mercury are not effectively removed
Solution Approach 1:
The patent changes the chemical parameters of the wastewater treatment process by adjusting pH to alkaline conditions (pH 9-11) and using varying ratios of zero-valent iron to ferric chloride. These parameter changes enable effective removal of toxic metals like selenate and mercury across different wastewater compositions, resolving the contradiction between reliable removal efficiency and adaptability to varying conditions
Solution Approach 2:
The patent employs a composite treatment approach combining zero-valent iron particles with ferric chloride to form a synergistic system. This composite material system provides both reduction capabilities (from zero-valent iron) and precipitation/flocculation capabilities (from ferric chloride), enabling reliable removal of multiple toxic metals including selenate and mercury while adapting to various wastewater compositions
2Reliability
If multiple treatment processes are used to remove different contaminants, then comprehensive contaminant removal is achieved, but treatment complexity and cost increase
Solution Approach 1:
The patent develops a universal treatment process that simultaneously removes multiple contaminants including selenate, mercury, arsenic, and other toxic metals through a single integrated chemical treatment system. The combination of zero-valent iron and ferric chloride performs multiple functions (reduction, precipitation, flocculation) in one process, eliminating the need for separate treatment steps for different contaminants and thereby reducing overall system complexity while maintaining comprehensive removal effectiveness
3Reliability
If advanced treatment technologies are implemented, then toxic metal removal efficiency is improved, but treatment cost increases significantly
Solution Approach 1:
The patent employs inexpensive, readily available materials - zero-valent iron particles and ferric chloride - that can be easily obtained and applied. These cheap reagents provide effective toxic metal removal without the high costs associated with advanced treatment technologies. The system accepts that the iron materials will be consumed and transformed during treatment, but this disposable approach using low-cost materials achieves both high removal efficiency and cost-effectiveness
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 significant removal of toxic metals, including selenium and mercury, with high efficiency and cost-effectiveness, capable of treating a wide range of contaminants in a single process, while being robust and flexible to handle variations in wastewater quality and quantity.
Implementation Method 1
The reactive solid and the secondary reagent contact the aqueous fluid, thereby reducing the selenate to an insoluble selenium species
Implementation Method 2
adsorbed or precipitated along with various of other toxic metals (such as As and Hg, if present) in wastewater onto the iron oxide sludge
Implementation Method 3
oxidising a portion zero valent iron so as to produce an iron corrosion product; and exposing the iron corrosion product to the secondary reagent so as to produce the reactive solid comprising the remaining zero valent iron and magnetite
Implementation Method 4
providing a fluidized bed reactor comprising a reactive solid in the form of a plurality of particles
Data Source
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AI summary
The present inventors have discovered a novel composition, method of making the composition, system, process for treating a fluid containing a contaminant. The fluid may be aqueous. The contaminated fluid may be in the form of a suspension. The treatment reduces the concentration of the contaminant. The reduction in concentration of a contaminant may be sufficient so as to effect remediation of the fluid with respect to the contaminant. The treatment may reduce the concentration of a plurality of contaminants. The present composition, system, and process are robust and flexible. The composition includes zero valent iron, an iron oxide mineral, and ferrous iron. The ferrous iron promotes maintenance of the iron oxide mineral. The iron oxide mineral promotes the activity of the zero valent iron. The process and system may involve multiple stages. A stage may be optimized for treatment with respect to a particular contaminant. The present composition, system, and process are effective for treating a fluid containing one or more of a variety of contaminants such as toxic metals, metalloids, oxyanions, and dissolved silica. It may be applied to treating various aqueous fluids, such as groundwater, subsurface water, and aqueous industrial waste streams.