PurifyMaker

It's a new Air allows purifying and at the same time measuring the level of air pollution present in the environment, alerting the user when the amount of gas exceeds a reference value. Our prototype using filters and photocatalytic processes, completely destroys COVID-19 viruses, microbes, bacteria, and other microorganisms. In addition, it effectively degrades Volatile Organic Compounds, such as formaldehyde, converting them into harmless substances such as carbon dioxide and water, and Particulate Matter, thus obtaining air free of contaminants. Air gives us our existence. Our goal is to establish early prevention of possible high levels of concentration of polluting harmful to humans.

Description video:

Has your time spent indoors increased during the COVID-19 pandemic as a result of stay-at-home and shelter-in-place policies worldwide?

We found this question in social media, but after thinking deeply in the question, it gives us the initial kick to work on developing a system to monitor and/or purify indoor air.

Introduction:

Our project has its first foundations in the investigations carried out by the Wisconsin Center for Space Automation and Robotics, a NASA research partnership center at the University of Wisconsin in Madison, sponsored by Marshall Space Flight Center’s Space Product Development program, produced an ethylene reduction device for a plant growth unit. The ethylene reduction device draws air through tubes coated in thin layers of titanium dioxide. The insides of the tubes are exposed to ultraviolet light, which creates a simple chemical reaction, converting the ethylene into trace amounts of water and carbon dioxide. As time goes by, KES partnered with Akida Holdings, of Jacksonville, Florida, which now markets the NASA-developed technology as AiroCide. Which is one air purifier, and what’s more the device has no filters that need changing and produce no harmful byproducts, such as the ozone created by some filtration systems.

With the vision focused on adapting and designing this technology to be used on Earth, whether in homes, companies, transportation, universities, and schools, to name a few, an air purification system is developed with the capacity to produce more than 99.99% pure air, by killing 98% of airborne pathogens that pass through it, including Bacillus anthracis (anthrax), dust mites, mycotoxins, molds, harmful viruses and bacteria such as Influenza A (flu), Escherichia coli, methicillin-resistant Staphylococcus aureus, Streptococcus pyogenes, and Mycoplasma pneumonia [1]; in addition to the fungi Penicillium and Aspergillus [2], volatile organic compounds (like ethylene), and odors [3].

Air filtration technology:

The air filtration technology to be used, which will be developed in-depth in the next section, consists of the application of:

• 1 pre-filter, which removes the largest particles such as hair, fibers, dust clump;
• 1 HEPA filter, which is nearly 100% efficient at capturing the spectrum of particles down to the very smallest airborne particles, removing particles of the size of 0.3 microns from the air, such as pollen, mold spores, dust. The efficiency is significantly enhanced at very small particle diameters below the most penetrating particle size (MPPS), typically 120 nm for HEPA filters. Therefore, the MPPS for typical HEPA filters varies from 200 to 300 nm, depending on the flow rate.
• 1 Activated Carbon filter, which removes organic and chemical household odors - like tobacco and food odors - and gases from household cleaners, paints, solvents, chlorine, carpets, furniture, and other materials containing chemical substances.
• 1 Photocatalytic Oxidation (PCO) module is made up of 2 components, a UVC bulb, and a catalytic mesh. The catalytic mesh is coated with titanium dioxide (TiO2), and the UVC bulb activates the catalyst on the mesh. Ultraviolet light technology, which attacks the molecular structure of viruses and bacteria, such as SARS-CoV-2 virion, that is 50–200 nanometres in diameter, which are too small to be filtered out by the HEPA filter, thus rendering them harmless, combined with Photocatalytic Oxidation is an important and unique feature of this air purification/filtration system [4].

Submicron and Nanoparticulate matter removal by HEPA-Rated media and Activated Carbon filters:

Particulate matter is a pollutant of special concern. Many studies have demonstrated a direct relationship between exposure to PM and negative health impacts. Smaller-diameter particles (PM2.5 or smaller) are generally more dangerous and ultrafine particles (one micron in diameter or less) can penetrate tissues and organs, posing an even greater risk of systemic health impacts.

Exposure to indoor air pollutants can lead to a wide range of adverse health outcomes in both children and adults, from respiratory illnesses to cancer to eye problems. Members of households that rely on polluting fuels and devices also suffer a higher risk of burns, poisonings, musculoskeletal injuries, and accidents [5]. The nature of the particulate matter pollutants such as their physical, chemical, and biological properties; the concentration level; and the size spectrum are factors that influence the nature of the hazard which can range from a nuisance to acute health [6].

Due to these reasons, it is essential for this project to have high-efficiency media filters. High-efficiency air filtration is unlike any other straining-dependent filtration process. The filter media is usually made up of many layers of submicron diameter fibers. In this structure, particles much smaller than the presumed opening in the filter material are readily captured. High-efficiency particulate air (HEPA) filter media is usually made with borosilicate microfibers with diameters from 2 to 500 nm. Thus, even if there are open spaces in a layer, the layers behind it prevent the further transport of particles. These characteristics of the filtration process lead to three basic flow-related capturing mechanisms known as the inertial impaction, interception, and diffusion mechanisms. Two additional mechanisms, straining and electrostatic attraction between the particle and fiber, only plays a secondary or minor role in HEPA filtration. It should be noted that one thing to keep in mind is that small changes in flow velocities through the media result in large changes in particle penetration through the filter. In other words, a simple HEPA-rated filter will perform as a ULPA-rated or better filter by simply lowering the flow velocity through the media.

Finally, and associated with this, experimental studies have found that granular adsorbent media such as activated carbon removes 0.3-µm-diameter particulate matter and gaseous contaminants by a similar mechanism. The removal occurs primarily in the interstitial space between packed bed granules and, for porous granules, to a very small degree in the granules’ macropores. Besides the particulate matter size, the primary factors influencing the removal are the carrier gas velocity and the diffusion constant of the aerosol. As a result of these studies, in accordance with the project proposal, filtration media effectiveness for removing ultrafine and nanoparticulate materials can be enhanced to a small degree when used in combination with a granular absorbent media located downstream of the filtration media, to effectively remove particulates and volatile components from a gas stream. [6]

Removal of Indoor Volatile Organic Compounds via Photocatalytic Oxidation

Human beings spend >80% of their lifetime indoors, including living and working places such as dwellings, offices, and workshops. Typical indoor air pollutants are particulate matters (PM), nitrogen oxides (NOx), carbon monoxide (CO), and volatile organic compounds (VOCs). Among those, VOCs are one class of prominent and representative indoor pollutants. Inhalation of VOCs can cause irritation, difficulty breathing, and nausea, and damage the central nervous system as well as other organs. A few VOCs are also linked with sick building syndrome (SBS), and formaldehyde is a particularly important VOC as it is even a carcinogen. The removal of VOCs is thus critical to control indoor air quality (IAQ).

The concentrations of common VOCs in a given indoor environment strongly related to the existence of emission sources and the efficiency of ventilation. In some cases, indoor VOCs levels are extremely high owing to low air exchange rates (AER) and poor ventilation. VOCs can be generated from indoor sources and can also penetrate from outdoors via air exchange. For example, some typical VOCs and their potential sources are:

• Formaldehyde: Pesticides, flooring materials, insulating materials, wood-based materials, machines, coatings, and paints.
• Toluene: Pesticides, flooring materials, insulating materials, wood-based materials, paints, adhesives, gasoline, and combustion source.
• Acetaldehyde: Wood-based materials, flooring materials, and HVAC system.

The traditional technologies for VOCs removal include adsorption, membrane separation, liquid absorption, and catalytic combustion. In addition, a single-based removal system may not offer satisfactory purification results due to the complexity of VOCs and variations on their characteristics in the real world. Combinations of the technologies are thus required to achieve the final goal, but both high costs and harsh conditions are limitations for their practical applications. There is a need to develop more economic, effective, and environmental-friendly treatment methods. Photocatalytic oxidation (PCO) has attracted more attention because of its unique characteristics in the removal of chemicals. In recent years, PCO has been perceived as a technology to remove indoor VOCs. The technique is highly-chemical stable, inexpensive, non-toxic, and capable of removing a wide variety of organics under light irradiation. TiO2 has been the dominant photocatalyst because of its superior photocatalytic oxidation ability, high photocorrosion resistance, excellent stability, non-toxic properties, and suitable bandgap structure.

TiO2 immobilized on different substrates can photocatalytically degrade indoor air pollutants in a flow system under UV light irradiation. The basic mechanism of photocatalytic degradation is that organics would be oxidized to H2O, CO2 or any inorganic harmless substances with *OH or superoxide (*O2-) radicals, which are generated on the surface of photocatalyst (e.g., TiO2) under ultra-violet (UV) light irradiation:

• TiO2 + hυ --> eCB- + hVB+
• TiO2 + hVB+ --> *OH + H+
• O2 + eCB- -->*O2-

In the heterogeneous reaction system, TiO2 is excited by the absorption of a photon with energy greater than or equivalent to the bandgap energy of the semiconductor, resulting in the electron transition from the valence band to the conduction band. The radiation could consequently produce electrons and holes (e´/h+) in the conduction band and valence band, respectively. Following the irradiation, the electrons and holes can undergo redox reactions with the adsorbed reactants on the photocatalyst’s surface that lead to the formation of intermediates and products.

It is also necessary to remember that anatase and rutile, two crystalline phases of TiO2, have been shown their feasibilities for PCO of indoor air pollutants under UV light irradiation. The band-gap energies of anatase and rutile are 3.23 and 3.02 eV, respectively. Anatase has shown better performance in PCO processes than that of rutile because of its more favorable conduction band configuration and stable surface peroxide groups. In general, TiO2 is fixed on some substrate, such as hollow tubes, silica gel, beads, and woven fabric.

In running the project it was important to realize that photocatalytic reaction rate, additional with the reaction kinetic and adsorption coefficients, are direct tools to evaluate the efficiency of a photocatalyst in the removal of VOCs. In addition to remembering that there are critical factors such as light source and intensity, pollutant concentration, RH, temperature, and deactivation and reactivation which can control the photocatalytic reaction rate. In short, VOCs are omnipresent and can greatly aggravate indoor air quality. Photocatalysis is considered as one of the most promising technologies for eliminating VOCs due to its high efficiency and stability. However, traditional photocatalytic materials such as TiO2 can only respond to UV irradiation, limiting the light utilization efficiency [7].

It is important to highlight the reason why it was decided to combine PCO technologies and the use of an activated carbon filter. Studies showed that the rate of PCO decreased with decreasing pollutant concentration. In addition, at high humidity levels, water vapor competed with TiO2 for adsorption sites which further decreased the rate of PCO. Thus, in an indoor environment where the pollutant concentration is only parts-per-billion (ppb) levels and under high humidity levels, the rate of PCO is rather low. To improve this situation, Shiraishi et al. (2003) [8], used an adsorbent to adsorb the pollutants to increase the pollutant concentration from the diluted air stream. The use of TiO2/AC not only increased the target pollutant removal efficiency but also reduced the amount of intermediate exiting the system. The removal efficiency of the TiO2/AC filter compared to the TiO2 filter is even higher when the target pollutant is less photoreactive. This study also showed that the enhancement effect of the TiO2/AC shown in the laboratory scale using the photoreactor is also verified by installing it into an air cleaner available in the commercial market [9].

Use of photocatalytic oxidation in the purification and disinfection of indoor atmospheres:

The action of ultraviolet light is based especially on the destruction of the DNA of all microorganisms such as viruses, bacteria, yeasts, and fungi, so friendly to the environment, without the addition of chemical products. The primary target of UVC disinfection is genetic material. Microbes are destroyed by ultraviolet light when it penetrates through the cell and is absorbed by the nucleic acid [10].

The microorganisms are inactivated by UV light as a result of photochemical damage to their nucleic acids. UV radiation is absorbed by the nucleotides, the building blocks of the cell's DNA and RNA, according to wavelength, with the highest values near 200 and 260 nm [11]. Absorbed UV promotes the formation of bonds between adjacent nucleotides, thereby creating double molecules or dimers [12]. Although the formation of thiamine-thiamine dimers are the most common, cytosine-cytosine dimers, cytosinatiamine, and uracil dimerization often occurs as well. The formation of a sufficient number of dimers within a microbe prevents it from replicating it's DNA and RNA, preventing its reproduction. Due to wavelength dependence for UV absorption by DNA, UV inactivation of microbes also is a function of wavelength. The UV dose is defined as the product of the intensity.

Microbial inactivation rates vary depending on the species of microbes, the microbial population, and the wavelength of UV light. Bacteria are generally less resistant to UV at 254nm than viruses, which in turn are less resistant than bacterial spores. Although protozoan cysts and oocytes are considered the most UV resistant microbial pathogens at 254nm, there is some evidence that cysts are more susceptible to inactivation by polychromatic UV light from medium pressure lamps UV by time.

Furthermore, UV does not promote the oxidative decomposition of microbial polymers, which results in the formation of CAO, which can cause the formation of the growth of biological films in distribution systems. As well as the use of UV eliminates the need to transport, store, and handle dangerous chemicals. UV disinfection is effective for a wide variety of viruses and bacteria with a lower dose range than for chlorine or ozone. Since UV disinfection only requires short residence times, the UV systems occupy a smaller area than chemical disinfection systems.

A system to monitor indoor air:

The damage from PM2.5 occurs when pollutant particles are absorbed into the lungs and enter the bloodstream, damaging the lungs and cardiovascular system. Gaseous pollutants such as O3, nitrogen dioxide (NO2), and sulfur dioxide (SO2) also damage health by inflaming and irritating lung tissue and increase the risk of respiratory diseases such as pneumonia and asthma. In May 2018, the World Health Organization reported that air pollution from PM2.5 and O3 is responsible for 7 million deaths per year.

One key difficulty stems from gaps in information about how much air pollution people are exposed to in their neighborhoods, workplaces, and homes. A satellite’s unique advantage is its ability to collect data on air pollutants from vast unmonitored territories such as the African or South American continents, the Middle East, or large portions of rural America. Satellites can also gather valuable information about how pollutants change over time, tracking the impacts of an economic downturn or new regulations. However, satellites don’t measure any pollutants directly. Instead, they infer the abundance of different gases and particles by measuring how molecules deflect, scatter, or absorb electromagnetic radiation. Each has a distinct electromagnetic signature which can be used to identify it, similar to a fingerprint. To detect PM2.5 – tiny particles of dust, smoke, and pollution – scientists use a measure called aerosol optical depth, the extent to which particles block and absorb sunlight as it passes through the atmosphere.

To encourage more interdisciplinary collaborations, NASA decided to form the Health and Air Quality Applied Sciences Team, or HAQAST. HAQAST also aims to create tools to guide and inform decision-makers tasked with air quality policy decisions, by providing information about the health benefits and losses that could result from different paths. But generating such predictions often requires running computationally demanding models that governments and people can’t afford. [14]

Like the ever-improving satellites, Bryan Duncan, an atmospheric scientist at NASA Goddard Space Flight Center and the Aura mission’s Project Scientist, sees the decline in U.S. air pollution since the 1970s as an encouraging success. Air quality controls are working, and nearly everyone in the U.S. is breathing cleaner air than they were 30 years ago, he says. Despite the improvements, however, much more work remains to be done, as air pollution causes nearly 80, 000 premature deaths in the U.S. each year, and more than 7 million worldwide. “We need to continue the trend, ” Duncan says. [14].

In relation to the concerns of the WHO and the governments about the aforementioned and the diseases that are contracted by indoor air pollution, resulting in the users becoming a city pollution mapping tool. This means someone could review the pollution levels across the entire city at one time. It also allows governments to review data to see where consistent high areas of pollution are and may help them to make informed choices about reducing pollution levels within cities.

Electronic sensors used help to monitor air quality and automatically increase the performance of the air purification system to compensate for periods of unusually high chemical activity and increased human activity. Warning lights alert staff to the presence of toxic chemicals and fumes well before they reach dangerous levels or become detectable to the human senses.

How We Developed This Project:

Our inspiration and commitment came from observing the great social, economic, and emotional impact that quarantine has caused in each of our lives. With the fear present at the risk of leaving the house or of trusting being indoors again. Whether they are work offices, schools, universities, friends' houses, restaurants, among others. So we thought: What could we do to reduce the fear of parents, children and each person when they have the need to leave their home? In response New Air.

Bearing in mind, the problem of COVID-19, but without neglecting the existing contamination, we focus on working directly on the purification of the interior air and being able to monitor them.

Data from space agencies formed the basis of our project, on what is currently in the air and its relationship to people's health. Through this information, we were able to select the most efficient way to meet the purposes of the challenge and even more, either in the selection of instruments or in the structure of the device.

Product data sheet:

-- 3D Printed Cylindrical Inner Shell

• Inner / Outer Radius: 104mm / 114mm
• Length: 419mm / Thickness: 5mm
• It presents grooves on the side near the upper and lower covers for inlet and outlet air.
• It is inscribed on the external shell

-- 3D Printed Hexagonal Outer Shell

• Side length: 72mm.
• Length: 429mm / Thickness: 5mm
• It presents grooves on the sides near the top and bottom covers for inlet and outlet air.

-- Turbine Motor

• Diameter: 36mm / Length: 45 mm / Solid Axis: 10mm

-- 3D printed suction fan

• Number of blades: 10 / Diameter: 100mm

-- Black Box (Protective of electronic components)

• Height: 90mm / Width: 70mm / Length: 40mm / Internal Thickness: 5mm

-- Electronics components used:

• ESP32 NodeMCU
• Dust sensor (PM 2.5 Sensor) / CCS811 (VOC Sensor)
• MICS6814 (CO, NH3 and NO2 sensor) / BME280 (Ambient Sensor)
• IC2 Multiplexer
• Display LCD 20x4 I2C
• Mosfet IRF540
• 12V Power Supply / 5V Power Supply
• Input Voltage: AC 110-220V 50/60Hz
• 12 V DC Motor
• 4 Push-button 2 pins.

-- Ultraviolet light lamp:

• Diameter: 45mm / Length: 80 mm

-- Filters (Pre-filter, HEPA, and Activated Carbon)

• Diameter: 104mm / Total Length : 56mm

-- TiO2 Mesh

• Formed by 3 joint hollow cylinders. Thickness: 5mm
• Inner / Outer Diameter: 65mm / 80mm
• Length: 80 mm

Diameter Cylinder Cap: 80mm / Width Cap: 5mm

Device Operation Description:

We have designed a low-cost, low-power air purifier, which incorporates Internet of Things technologies in order to control its speed, sense quality air data, and store those values in a cloud database. The sensors included are a PM2.5, which measure dust concentration; a CCS811, which is a VOC (Volatile Organic Compounds) sensor and detects CO2 and TVOC; a MCIS6814, which detects CO, NH3, and NO2; and a BME280, which detects pressure, temperature and humidity values from the environment. Our prototype has a manual and an automatic mode to control the purification speed, which is achieved by using a PWM signal. In manual mode, the user will have the option of choosing between Normal, Fast, and Night speeds, where the last one prioritizes the motor to be quiet. The LCD will display the data sensored and information such as speed modes and if the purifier is in manual or automatic mode. For the data processing, we are using an ESP32, which includes a Wifi and Bluetooth module, technologies that we are integrating with a mobile app in order to monitor the sensed data remotely. Moreover, we have considered using a GPS module to register the locations where the data is retrieved. On the other hand, while designing this prototype we encountered the problem that we were using multiple I2C devices, however, we could find a solution using an I2C multiplexer. At first instance, we were planning to use an ESP8266, which is a similar microcontroller to the ESP32 but it only includes a Wifi module, nevertheless, this module has the limitation that once a program is uploaded to the microcontroller, it cannot connect to a different server than the one it is already programmed until the program is updated with a new one. That is why we opted for an ESP32 since, besides a Wifi module, it includes a Bluetooth module that can be used to connect to the app if needed. The Arduino programming is not completed yet, however, we managed to implement a functional prototype app using AppInventor (blocks programming), where we could fully control our air purifier and monitor the sensed data communicating with the database, which has been created using Firebase. While at the moment the app only shows values sensed, we can also implement graphics to visualize how the values change through time, including GPS data, which will turn our monitor system into a more powerful asset.

App:

We managed to implement a functional prototype app using AppInventor (blocks programming), where we could fully control our air purifier and monitor the sensed data communicating with the database, which has been created using Firebase. While at the moment the app only shows values sensed, we could also implement graphics to visualize how the values change through time, including GPS data, which will turn our monitor system into a more powerful asset. You can download the apk of the app through this link

Firebase Database:

As mentioned above, we have created a Realtime Database in Firebase. We have distributed the data into childs for every sensor and other parameters such as Mode (0 = Manual Mode, 1 = Automatic Mode), Speed (0 = Normal, 1 = Fast, 2 = Night) and Start (0 = OFF, 1 = ON).

Circuit Diagram:

The sensors included in this project are a PM2.5, which measure dust concentration; a CCS811, which is a VOC (Volatile Organic Compounds) sensor and detects CO2 and TVOC; a MCIS6814, which detects CO, NH3, and NO2; and a BME280, which detects pressure, temperature and humidity values from the environment. For the data processing, we are using an ESP32, which includes a Wifi and Bluetooth module, technologies that we are integrating with a mobile app in order to monitor the sensed data remotely. The LCD will display the data sensored and information such as speed modes and if the purifier is in manual or automatic mode.

Resources:

• 1. https://www.nasa.gov/mission_pages/station/research/advasc.html.
• 2. https://spinoff.nasa.gov/Spinoff2009/ch_2.html.
• 3.https://spinoff.nasa.gov/Spinoff2013/cg_4.html.
• 4.https://www.hamiltonthorne.com/index.php/portable-zandair-100c-for-ivf.
• 5. https://www.who.int/health-topics/air-pollution#tab=tab_3
• 6.https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20170005166.pdf.
• 7.https://www.hamiltonthorne.com/attachments/article/656/molecules-21-00056.pdf.
• 8. Shiraishi, F., Yamaguchi, S., Ohbuchi, Y., 2003. A rapid treatment of formaldehyde in a highly tight room using a photocatalytic reactor combined with a continuous adsorption and desorption apparatus. Chemical Engineering Science 58, 929–934.
• 9.http://www.zn903.com/cesclee/papers/A-20.pdf.
• 10. https://dspace.ups.edu.ec/bitstream/123456789/7256/1/UPS-CT004152.pdf
• 11. Sonntag, C. von and Schuchmann, H-P. UV disinfection of drinking water and byproduct formation-some basic considerations. J Water SRT–Aqua, 1992; vol. 41(2):67-74.
• 12. Jagger, J. Introduction to research in ultraviolet photobiology. Englewood Cliffs, New Jersey: Prentice-Hall Inc., 1967.
• 13. http://usam.salud.gob.sv/archivos/pdf/agua/LUZ_ULTRAVIOLETA.pdf
• 14. https://airquality.gsfc.nasa.gov/health/measuring-air-pollutions-health-impacts-space