Multi-spectral Photocatalytic Compounds for Water Decontamination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional wastewater treatment processes fail to effectively remove trace amounts of pharmaceuticals, pesticides, and personal-care products due to their persistence and negative environmental and health impacts, particularly in potable water reuse scenarios.
Innovation Solution
Employing a combination of zinc oxide, hematite, and copper oxide photocatalysts with different bandgaps to harness multiple wavelengths of solar radiation, enhancing the degradation of recalcitrant contaminants through heterogeneous photocatalysis, with the photocatalysts being engineered to be larger than 0.1 μm for easier filtration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional wastewater treatment processes are used, then operational simplicity is maintained, but recalcitrant contaminants (pharmaceuticals, pesticides, personal-care products) are not effectively removed
Solution Approach 1:
The patent combines three different metal-oxide photocatalysts (TiO2, ZnO, Fe2O3) with different bandgaps into a composite material system. This composite approach enables the catalyst to absorb multiple wavelengths of solar radiation simultaneously, achieving superior contaminant degradation rates that exceed the sum of individual catalyst performances, thus resolving the contradiction between removal efficiency and process complexity.
Solution Approach 2:
The patent segments the solar spectrum into multiple wavelength ranges (UV, visible, near-IR) and assigns different photocatalyst components to harvest each segment. TiO2 handles UV, ZnO handles visible light, and Fe2O3 handles near-IR radiation. This segmentation allows comprehensive utilization of solar energy for contaminant degradation, improving productivity while maintaining manageable system complexity through modular catalyst design.
2Productivity
If smaller photocatalyst particles are used to increase surface area, then photocatalytic activity is enhanced, but filtration and separation become more difficult
Solution Approach 1:
The patent optimizes the particle size parameter of photocatalysts to a specific range (0.1-10 μm) that balances photocatalytic activity with ease of separation. This parameter optimization ensures sufficient surface area for high degradation rates while maintaining particle sizes that are easily filterable and separable from treated water, resolving the contradiction between productivity and operational ease.
3Use of energy by moving object
If a single photocatalyst with a specific bandgap is used, then the system is simple to design, but only a limited range of solar wavelengths can be harvested
Solution Approach 1:
The patent creates a multi-functional photocatalyst system where each metal-oxide component (TiO2, ZnO, Fe2O3) serves a specific function by harvesting a particular wavelength range of solar radiation. Together, they form a universal catalyst system that can utilize the entire solar spectrum from UV to near-IR, achieving high energy utilization efficiency while maintaining systematic organization that manages design complexity.
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 multi-spectral photocatalytic approach achieves contaminant degradation rates exceeding the sum of individual photocatalyst rates, demonstrating a synergistic effect that effectively breaks down contaminants into benign byproducts, thereby improving water decontamination efficiency.
Implementation Method 1
The cascade of reactions involved in photocatalysis is initiated by the absorption of a photon, which excites an electron from the valence band to the conduction band of the semiconductor thereby generating an electron-hole pair
Implementation Method 2
Heterogeneous photocatalysis (where catalyst and reactant are in different phases) with metal-oxide semiconductors is an emerging technology for the removal of recalcitrant contaminants from wastewater
Implementation Method 3
The electron-hole pair can migrate to the material surface, where it reacts with surrounding water and dissolved oxygen to form reactive oxygen species ('ROS'). It is these ROS that participate in the oxidation of recalcitrant contaminants in solution
Data Source
AI summary
Disclosed are various combinations of three different metal-oxide photocatalysts with three different bandgaps that can be used to harvest multiple wavelengths of incident solar radiation and to thus efficiently degrade recalcitrant contaminants. The photocatalysts are from the class of transition metal oxides and are non-toxic compounds based on earth-abundant materials. In some embodiments, particles of the photocatalysts are formed to be greater in diameter than about 0.1 μm in order to make them easier to filter out after treating the contaminant. In some embodiments, the metal-oxide photocatalysts are zinc oxide which is ultraviolet active, hematite which is active in the visible spectrum, and copper oxide which is active in the near infrared spectrum. Various combinations in various embodiments achieve measured contaminant degradation rates greater than the sum of the degradation rates of the individual photocatalysts that make up the combination.