Hexavalent Chromium Reduction Using Weak Organic Acids
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Solution Overview
Problem
Current industrial processes for reducing hexavalent chromium in effluents are inefficient due to high reaction times, requirement for acidic environments, and generation of potentially toxic by-products, making them unsuitable for large-scale industrial use.
Innovation Solution
A process involving the addition of a weak organic acid, such as ascorbic acid, to effluents at a slightly acidic pH, followed by pH adjustment to neutrality, allowing for rapid reduction of hexavalent chromium to trivalent chromium, which is then easily evacuated without additional treatment, using an installation with pH adjustment and decantation tanks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional reducing agents (sulfur dioxide, sodium bisulphite, iron) are used to reduce hexavalent chromium, then chromium reduction can be achieved, but the process requires working in a very acidic environment (pH lower than 4) which is incompatible with direct discharge into the natural environment and requires significant consumption of pH adjusting agents
Solution Approach 1:
The patent changes the pH parameter from the conventional highly acidic range (pH < 4) to a near-neutral range (pH 6-8), making the reduction process compatible with direct environmental discharge without requiring additional pH adjustment. This is achieved by selecting reducing agents that work effectively at near-neutral pH levels.
Solution Approach 2:
The patent employs readily available, inexpensive reducing agents such as ascorbic acid, vitamin C, or vegetable matter that can be easily added to effluent and work at near-neutral pH, replacing costly and complex pH adjustment chemicals required by conventional methods.
2Reliability
If conventional reducing agents are used to reduce hexavalent chromium, then chromium reduction can be achieved, but the process requires significant consumption of pH adjusting agents to maintain acidic conditions and subsequently adjust pH for discharge
Solution Approach 1:
The patent fundamentally changes the pH operating parameter from highly acidic (pH < 4) to near-neutral (pH 6-8), eliminating the need for large quantities of pH adjusting agents while maintaining effective chromium reduction. This parameter change directly reduces substance consumption.
Solution Approach 2:
The reducing agents selected (ascorbic acid, vitamin C, vegetable matter) naturally work at or near neutral pH, eliminating the need for external pH adjustment chemicals. The system becomes self-sufficient regarding pH management.
3Reliability
If conventional reducing agents are used to reduce hexavalent chromium, then chromium reduction can be achieved, but the process generates potentially toxic by-products that are difficult to eliminate
Solution Approach 1:
The patent uses biodegradable, naturally occurring reducing agents like ascorbic acid and vegetable matter that decompose into harmless substances (carbon dioxide, water, organic matter) rather than generating persistent toxic by-products, thereby eliminating secondary pollution concerns.
Solution Approach 2:
The patent converts potentially harmful conventional reducing agents into beneficial natural substances. By using vegetable matter and ascorbic acid, the reduction process generates environmentally friendly by-products that can even serve as nutrients rather than pollutants.
4Reliability
If conventional reducing agents are used to reduce hexavalent chromium, then chromium reduction can be achieved, but the process requires high reaction times that are incompatible with rapid industrial treatment
Solution Approach 1:
The patent changes the pH parameter to near-neutral levels, which according to the patent text, accelerates the reduction reaction kinetics. This parameter optimization enables rapid chromium reduction compatible with industrial throughput requirements.
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 significant reduction in hexavalent chromium within 30 minutes, compatible with industrial constraints, without generating toxic by-products, and allows for direct discharge of treated effluent, meeting regulatory standards.
Implementation Method 1
addition of a weak organic acid, such as ascorbic acid, to effluents at a slightly acidic pH, followed by pH adjustment to neutrality, allowing for rapid reduction of hexavalent chromium to trivalent chromium
Implementation Method 2
using an installation with pH adjustment and decantation tanks
Data Source
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AI summary
The present invention relates to a method for reducing the chromium content, particularly hexavalent chromium content, present in a liquid effluent, referred to as "initial effluent" (1), loaded with solid particles. Said method includes at least one reducing step (9) whereby a weak organic acid (10) is added to the initial effluent in an amount sufficient to reduce the hexavalent chromium, present in the initial effluent, to a lower valence, i.e. trivalent chromium. Said step is followed by a step for discharging the resulting treated liquid effluent, referred to as the "final effluent". Said method also includes a step for collecting, at least by settling, the solid particles present in the initial effluent and a reducing step (9) that is carried out after adjusting (12) the pH of the initial effluent to a pH value that is less than the initial pH of the effluent while being compatible with discharging the final effluent at said pH value. The invention also includes equipment for implementing the method.