Cerium Dioxide Arsenic Oxidation for Water Treatment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for removing arsenic from water, particularly arsenite, are ineffective and impractical for residential use due to space requirements and the need for dangerous chemicals, and the potential decrease in maximum contaminant levels necessitates new techniques for efficiently reducing arsenic concentrations in drinking water.
Innovation Solution
Treatment of arsenic-containing water with cerium dioxide in the +4 oxidation state to oxidize arsenic from the +3 state to the +5 state, allowing for its removal through precipitation using a precipitating agent, such as alumina, to produce a purified aqueous liquid with reduced arsenic levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional methods (reverse osmosis, activated alumina) are used to remove arsenic from water, then arsenic removal effectiveness is improved, but the need for dangerous chemicals and large space requirements makes them impractical for residential use
Solution Approach 1:
The patent extracts the harmful elements (dangerous chemicals and large equipment) from the arsenic removal process while retaining the core function. The invention uses simple, safe materials (alumina and calcium oxide/hydroxide) that can be obtained from ordinary cement, eliminating the need for hazardous chemicals and complex reverse osmosis systems, making the process practical for residential use.
Solution Approach 2:
The patent changes the chemical parameters of the treatment process by using alkaline conditions (pH 9-11) created by calcium oxide or hydroxide to convert arsenite to arsenate, which then precipitates with alumina. This parameter change enables effective arsenic removal using safe, simple materials instead of dangerous chemicals.
2Reliability
If the maximum contaminant level for arsenic is decreased to below 2.0 ppb, then drinking water safety is improved, but current removal techniques cannot achieve such low concentrations
Solution Approach 1:
The patent uses a composite material system consisting of alumina and calcium oxide/calcium hydroxide (from ordinary cement). The alumina provides arsenate precipitation capability while the calcium compounds maintain alkaline pH conditions, creating a synergistic effect that achieves complete arsenic removal to below 2.0 ppb, meeting the stricter contaminant level requirements.
3Productivity
If arsenite is targeted for removal using adsorption and coagulation techniques, then treatment speed is improved, but removal effectiveness is poor because arsenite remains un-ionized at effective pH ranges
Solution Approach 1:
The patent performs a preliminary chemical transformation by raising the pH to 9-11 using calcium oxide or hydroxide, which converts un-ionized arsenite into ionized arsenate species. This preliminary action enables subsequent effective precipitation with alumina, solving the problem of poor arsenite removal while maintaining treatment efficiency.
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 method efficiently reduces arsenic concentrations in water from above 2.0 ppb to below 2.0 ppb, making it effective for treating various aqueous streams, including drinking water and industrial waters, while avoiding the use of hazardous chemicals and minimizing waste production.
Implementation Method 1
Treatment of arsenic-containing water with cerium dioxide in the +4 oxidation state to oxidize arsenic from the +3 state to the +5 state
Implementation Method 2
the arsenic in the +5 oxidation state is removed from the aqueous liquid by contacting the liquid with a precipitating agent that reacts with the arsenic in the +5 oxidation state to produce insoluble arsenic compounds
Data Source
AI summary
Arsenic is removed from water and other aqueous feeds by (1) treating the feed with a compound containing cerium in the +4 oxidation state, preferably cerium dioxide, to oxidize arsenic in the +3 oxidation state to arsenic in the +5 oxidation state and (2) removing the arsenic in the +5 oxidation state from the aqueous phase, normally by contacting the treated feed with alumina or other precipitating agent containing cations in the +3 oxidation state.