# Tag Info

41

It's much easier to assemble a system that's safe under external pressure than one that's safe under internal pressure. Convex flasks and tubes resist external pressure better than internal pressure. If something leaks or breaks, you have air rushing into the system, rather than reactants and products blasting out. For that matter, if you've put things ...

17

I think the term describing the initial process of separation of the solid phase (dust particles) from the gas phase via bubbling is a wet scrubbing process. On an industrial scale, it's more efficient to spray liquid phase, whereas on a laboratory scale bubbling in a compact glass gas scrubber or a gas washing bottle is more convenient. In order to ...

11

The short answer to your question "What's the science behind the N95 filter?" is that it is what's called a tortuous path filter, removing particulates from a flow of contaminated air by impact and absorption of the particulate onto the filter material or by trapping particles of sufficient size between the fibers constituting the filter. The term N95 ...

10

Pressure filtration is commonly used in industrial applications outside of the lab. In this case vessels and process lines are usually made from metal or plastic and can be easily designed to operate at a given pressure. From an engineering standpoint, pressure filtration offers the ability to have a higher driving force and allows you to limit the required ...

8

From official 3M Q&A brochure (emphasis mine): Can N95 respirators filter particles that are really small like smoke, soot and ash? Yes. Particulate filters employ multiple mechanisms that are effective at filtering a range of particles that include those so small you cannot see them. In fact, as part of their certification process, NIOSH tests ...

8

This answer applies to carbon filtration of water. According to most of the sources I found, activated carbon binds to most substances through London dispersion forces (from the Wikipedia article). This should mean that it adsorbs larger molecules and non-polar molecules preferentially since they would have larger dispersion forces. As your quote indicates, ...

7

Precipitation won't work Nitrate removal is a very tough problem in wastewater treatment. One of the reasons is that nitrate salts of nearly every common cation are highly water soluble. Unfortunately, I can't think of a way to precipitate nitrate from your water sample. How commercial nitrate removal processes work Nitrate is removed from wastewater ...

7

It appears that there is some validity to this technology. Not surprisingly, the published journal literature available is basically non-existent, except for a handful of patent applications describing something along those lines. The title of one journal publication "Preparation of a filtering material using nanomaterials for removal of a heavy metals ...

7

I'd like to expand on some points that have been mentioned in the comments by @IvanNeretin, @Karl and @electronpusher, but IMHO deserve some more attention: As @electronpusher commented, aspirator (Venturi) pumps are cheap and easily available. They are also super robust: each pump is usually made from a single material, and a range of materials (brass, ...

6

The principle on which they depend isn't that different. This does not mean, however, that you can wear a dust mask instead of an N95. From the Review article of "Respiratory Protection" from the New England Journal of Medicine: The most commonly recommended respirator in the health care setting is the N95: “N” means “not oil-proof,” and “95” means that ...

6

Positive pressure filtration is extremely common, probably even more common than vacuum filtration. source: https://andyjconnelly.wordpress.com/2016/09/28/syringe-filters/

5

Altered properties (band gap, Stokes shift) of cristalline nanoparticles as compared to bulk have been demonstated for various semiconductors, namely CdS, CdSe, TiO2, etc. They result from a significantly different surface-to-volume ratio and the fact that atoms at the crystal surfaces simply lack the proper number of neighbours. Where the crystal ends, ...

5

I worked as a grad student in organic chemistry labs and both vaccuum lines and compressed air are very common. The reason most filtering setups uses vaccuum (especially for gross extraction after recristallization) is that glassware does not tolerate pressure very well. We do use air pressure to speed up purification with manually-packed silica gel ...

4

It looks like ion exchange resin, it is used to specifically capture ions from water and replace them by others (either $\ce{H^+}$ or alkali metal ions. As such, it is probably also part of the filter.

4

Try to get some clay and shake it vigorously with water. Let it settle for a several hours. Test your filter with the supernatant water and collect the filtrate in a very clean glass tumbler. Colloids have an interesting property of scattering light. In a dark room, try to shine light (ordinary flashlight might work or perhaps an ordinary pointer used in ...

3

If the high efficiency particle air (HEPA) filter says it blocks PM 2.5 that's good as pm 2.5 particles are the ones your lungs cannot easily dispel and cause haze. Unfortunately sulfur oxides and nitrogen oxides are gasses, so no particle filter will remove them.

3

First of all and I want to clarify something that it often misunderstood, which is that charcoal has carbon but it is NOT carbon. Charcoal actually have a bit of residual Hydrogen and oxygen in it and is again NOT carbon. Carbon is a pure element that occurs naturally in a variety of allotropes. Charcoal is the charred product from pyrolyzing wood. ...

3

Citric acid is relatively soluble in ethanol (62g/100g) whereas sucrose is relatively insoluble in ethanol (1g/170ml). There are many different kinds of sugars and sucrose is probably not the primary one in this extract; branched sugars... oligosaccharides (which have generally higher solubilities than sucrose) are likely, and I'm sure there are a few other ...

2

While the idea of filtering formaldehyde from food might sound naive, the motivation is understandable and the problem apparently real. I've found at least one publication on the topic: T Yeasmin, *M S Reza, M N A Khan, F H Shikha and M Kamal PRESENT STATUS OF MARKETING OF FORMALIN TREATED FISHES IN DOMESTIC MARKETS AT MYMENSINGH DISTRICT IN BANGLADESH ...

2

A combination of osmosis and Gibbs-Donnan effect is the correct explanation. With a semi-permeable membrane such as the one you are using, or a cell membrane, or in dialysis, water can move freely as can chloride and other small ions, however large molecules such as proteins cannot. A simplified explanation is this: in osmosis, the tendency is for the ...

2

Your question is about as broad as chemistry itself. Like you said, you may try dissolving them in water, if one is soluble and the other is not. If it's not working with water, chances are it will work with ethanol, or acetone, or... see, there are many solvents on the shelf. No luck? Maybe by now you've found something that dissolves them both, so you may ...

2

Aluminum is remarkable safe for human consumption, also considering that it is present in high concentration essentially everywhere, and it is not known to have any significant specific biological roles. Wikipedia happens to have a nice well researcher section on aluminum's possible effects on human and animal health: Aluminium: health concerns. Alum is also ...

2

You are not wrong in your understanding of a water softener, nor are you wrong in your understanding of a reverse osmosis filtration system. Does the RO filter care whether the supply water is salty or hard? I would like to make the point that your RO filter is incapable of caring about the hardness of the water. This is more about carefully choosing ...

2

Activated carbon's forte is vapor adsorption of hydrocarbons due to the activated carbon's high surface area, and this mask is probably very good at adsorbing fumes from hot parafin. However, activated carbon does not tend to make a good material for filtering out the most harmful components of that kind of smoke, namely particulates smaller than 2.5 ...

2

Rig up a column that you can fill with granular activated carbon (GAC). Throw batting on either end to prevent carbon fines from entering your dissolution chamber. Replace the carbon when you reckon it is no longer working. If you can afford the heat, throw a cooling coil in front of the filter. Another method is indicated in this patent: US4078129. They ...

2

The first thing that comes to my mind is Reverse Osmosis, since it can exclude large molecules dissolved in water. I don't think that a typical filter (eg: paper filters for buchner apparatus) would work if the polymer is actually dissolved in water and it's not a precipitate. An alternative (maybe cheaper) idea is the following: since your mixture is ...

2

Activated carbon is usually of higher quality than activated charcoal, but the words are often used interchangably.

2

Cations and anions of water-soluble salts cannot be removed from water using only mechanical filters (which rely on particle size) such as coffee filters. In order to remove such ions, ion exchange resins can be used. These resins consist of an insoluble matrix, e.g. polystyrene that is crosslinked with divinylbenzene to vary the porosity of the resin. To ...

2

To separate hydrogen, a warmed Pd membrane is very effective... except that Pd catalytically ignites the $\ce{H2 - O2}$ mixture. oops A carbon nanotube membrane might work... but would be a bit pricey. Various organic polymers have been used as hydrogen-permeable membranes, though some are poisoned by $\ce{CO2}$. Actually, for a demonstration, $\ce{H2}$ ...

2

Just add your gas mix in a container with NaOH solution and shake well or bubble it continuously through the solution. SO2 dissolves in water to form H2SO3 (and H2SO4 in the atmosphere when it rains resulting in what we call acid rain) which will be neutalized by NaOH to give dissolved Na2SO3. Your air should be freed of most SO2. This is how it is done in ...

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