Selenium Removal via Sulfur-Carbon Oxidation
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Solution Overview
Problem
Current methods are inadequate for effectively converting selenocyanate in aqueous streams to selenite and subsequently removing selenium from water, particularly in wastewater, as they fail to achieve sufficient conversion and removal efficiencies.
Innovation Solution
A process involving a composition of sulfur and a porous support, such as carbon, is used to convert selenocyanate to selenite in the presence of oxygen, followed by treatment with a selenite removal system like iron coprecipitation to reduce selenium levels in the water stream.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional methods are used to convert selenocyanate to selenite, then the conversion process can be performed, but the conversion efficiency is insufficient
Solution Approach 1:
The patent employs a porous support material (such as porous carbon or porous metal oxides) as the catalyst carrier. The porous structure provides large surface area and active sites for the oxidation reaction, significantly enhancing the conversion efficiency of selenocyanate to selenite while ensuring complete conversion of the selenium compound.
Solution Approach 2:
The invention uses a composite material system consisting of sulfur-containing compounds combined with porous support materials. This composite structure integrates the catalytic activity of sulfur compounds with the high surface area and mechanical stability of porous supports, achieving both high conversion efficiency and complete reaction.
2Productivity
If conventional selenite removal systems are used, then selenium removal can be achieved, but the removal efficiency is insufficient
Solution Approach 1:
The patent modifies the removal process by changing the chemical form of selenium from selenocyanate to selenite through in-situ conversion, and then applies optimized removal conditions (such as pH adjustment, contact time, and dosing rates) to achieve high removal efficiency. The process reduces selenium concentration to less than 5% of the original level.
Solution Approach 2:
The invention introduces selenite as an intermediate form that facilitates more effective removal. By first converting selenocyanate to selenite (which has different chemical properties and reactivity), the process creates a more favorable condition for subsequent removal operations, whether through precipitation, adsorption, or other removal mechanisms.
3Reliability
If a two-step process (conversion followed by removal) is implemented, then selenium can be effectively removed, but the process complexity increases
Solution Approach 1:
The patent combines the conversion and removal operations into an integrated system where the porous catalytic material performs both functions sequentially in a single treatment train. The sulfur-containing catalyst facilitates in-situ conversion of selenocyanate to selenite, which is then removed in the same contact zone, eliminating the need for separate treatment stages and reducing overall process complexity.
Solution Approach 2:
The invention performs preliminary conversion of selenocyanate to selenite within the same treatment system before removal occurs. This preliminary action transforms the selenium compound into a more removable form, enabling effective removal in the same process unit and avoiding the need for separate conversion and removal systems.
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 process achieves a high conversion rate of selenocyanate to selenite, allowing for significant reduction of selenium in the treated stream, with up to 90% of selenocyanate converted and selenium levels reduced to less than 5% of the original concentration.
Implementation Method 1
contacting a feed stream comprising water and selenocyanate with a composition comprising sulfur and a porous support, in the presence of oxygen, for conversion of at least a portion of the selenocyanate to selenite
Implementation Method 2
The selenite removal system is selected from the group consisting of copper coprecipitation of the selenite, iron coprecipitation of the selenite, and combinations thereof
Data Source
AI summary
A process for removing selenium from an aqueous stream using a supported sulfur material, to convert selenocyanate to selenite, followed by removal of the selenite from the aqueous stream.