Carbon dioxide  has become a major escalating problem that has caused global warming. CO2 capture & storage (CCS) is feasible and it can proceed at high speed. Many chemical compounds can "arrest"  CO2 & thus prevent its harmful contribution to life on earth (such as CaO, LiOH, and many active oxides & hydroxides).

But "prevention is better than cure" , so it would be much better to reduce the world's dependence on fossil fuels especially in the transportation sector. This means a major shift into energy alternatives & this shift is "really" hindered by evil powerful forces who built their wealth by the present trends of energy usage.

As far as science & technology is concerned, CO2 levels in the atmosphere could be decreased dramatically. But the scientists do not have the "political muscles" to implement their ideas & procedures. 

Hi dear Nizar Matar

I think the best way for your aim is following the photosynthesis cycle.

Simply look at the equation:

C + O2 -> CO2

The enthalpy change here is around - 393.5 KJ/mole which means that the reaction is exothermic.  Thus the reverse reaction (carbon dioxide to carbon and oxygen) is endothermic and the production of oxygen will require a huge input of energy which no nanomaterial on its own can supply - even as a catalyst as the reaction is not favorable thermodynamically.

Dear Nizar,

Thanks for responding. I really appreciate it.

I completely agree with you that prevention is better than cure. But I think we have already disturbed the climate, now its time to cure it. According to BBC news globally this summer was the hottest summer.

It will be of a great help if you could explain how chemicals like CaO, LiOH etcs can arrest CO2.

Thanks again.

Nothing can replace a plant for that purpose. I would say planting more trees will come with added advantages, whereas producing an alternative will require chemicals and non- self sustaining materials creating another problem of waste management.

Dear Alan,

Thanks for responding. I really appreciate it.

I understand that conversion of CO2 into O2 will need lot of energy but is there any other way.

@ Ketaki Deshmukh    As Scotty in Star Trek stated: "You cannae change the laws of physics".  I recommend: https://www.youtube.com/watch?v=7ZS2-4-iUJ4

Answering the question of my RG colleague Ketaki Deshmukh:

CO2 reacts with CaO in a favorable reaction to give limestone: CaO+CO2 →CaCO3 & therefore CO2 is captured or “arrested” since the reverse reaction is endothermic .

For astronauts who stay for long in spaceships, accumulation of CO2 that is released upon the process of exhale will harm them, so a tube receives the breath out & sends it to a container in which there is an aqueous solution of LiOH. The following favorable reaction occurs: LiOH+ CO2→ LiHCO3. Upon return to earth, the valuable lithium bicarbonate is utilized. In this example, CO2 is also captured or “arrested”.

I agree that planting too many trees in various parts of this earth will help in removing lot of CO2 but there is  worldwide "laziness" in this respect.

Dear Colleague,

Thanks a lot for your kind invitation, but this topic is out of my field domain, so I have no idea. Hope you more success.

Accept my regards,

Emad

@ Nizar Matar     CaO is manufactured by heating limestone, CaCO3:

CaCO3 -> CaO + CO2

How is this CO2 disposed of?  We're back to the cycle again...

@Nizar, Thanks for your suggestion and recommendation. Could you please explain me  approximately how much CO2 can be absorbed on LiOH? I mean what is the ratio.

Thanks

Thanks Artur. Your articles is really valuable. However if we need to make it for a large scale CO2 conversion, how much space it will need and what will be the efficiency? Because in big cities space is the problem, I was thinking using nanotechnology if we could make some portable devices which we can easily carry. What is your opinion about it?

Thanks again for your response and recommendation. I really appreciate it.

@ Artur Braun    I have never said that there's anything 'wrong' with inputting energy.  I have simply stated that the thermodynamics (which everyone, including Ketaki Deshmukh, seems to have conveniently ignored) tells you that the reaction (production of O2 from CO2) is only feasible with large energy input. I have also pointed out that the production of CaO involves release of CO2 so there's no gain in using that CaO to absorb CO2...

@ Ketaki Deshmukh Are you a chemist?  Two moles of LiOH will absorb one mole of CO2 to form the carbonate: 2LiOH + CO2 -> Li2CO3 + H2O

Lithium salts are useful for their lightness (hence use in space). See: https://www.nasa.gov/pdf/519341main_AP_ED_CO2Removal_Therm.pdf

LiOH is often made from the carbonate: Li2CO3 + Ca(OH)2 → 2 LiOH + CaCO3 again showing that we can't get away from CO2 or carbonates...    Ca(OH)2 - slaked lime - is made from hydrating lime (CaO) - made from heating of limestone (CaCO3) with evolution of CO2..  The CO2 eventually ends up in the atmosphere (or in fizzy drinks!)...

Dear Ketaki,Answering your question:One gram of anhydrous lithium hydroxide can remove 450 cm3 of carbon dioxide gas.

There is lot of information about your topic & some of it is "classified". Upon looking at Stine's book "Applied Chemistry", you can easily see a mixture of science, technology, economics, and politics. 

I taught applied chemistry as a course for 10 years but the course was cancelled for reasons that I cannot reveal now but I shall do that in the future. Another course which I taught for about 15 years "Chemistry & Society" was also cancelled for the same reason.

@ Alan, I think we can use CaCO3 for many purposes. We really dont need to make CaO from CaCO3.

I understand that plant is the best option, but if there is no place to plant the trees then what people will do. China is buying oxygen cylinders from Canada because cities are highly populated and polluted. In such case we need to find solution. 

Thanks for your response

@Nizar Thanks for the information. It will surely help me.

@ Ketaki Deshmukh  So, tell me how we make CaO economically without the involvement of CaCO3........?  Yes, you are correct CaCO3 is used for many purposes...

@ Nizar 'One gram of anhydrous lithium hydroxide can remove 450 cm3 of carbon dioxide gas. There is lot of information about your topic & some of it is "classified".' 

The equation 2 LiOH + CO2 -> Li2CO3 + H2O is not classified and provides all the information needed to calculate masses and cm3 of gas (pV = nRT) that can be (theoretically) absorbed.

Hi Alan,

Please check this. I think another way could be dissolving  CaCl2 in water and adding little H3PO4 subsequently heating the mixture could give you CaO.

http://pubs.acs.org/doi/abs/10.1021/ef5010896?journalCode=enfuem

 Dear Ketaki Deshmukh,

My previous comment came out with a wrong format in one place. I rectified the error so that the information becomes properly presented. Best wishes.

OK, Ketaki.  Where does the CaCl2 come from?  Dissolving CaCO3 in HCl....with release of CO2......

@ Alan and Kenneth, The whole point of discussion and my question is to find out the solution for increased global warming. Not to discuss that how it is not possible. If its not possible by one way then what could be another way. Beacuse I dnt think anything is impossible. Many scientist are working on artifical photosynthesis and m sure there must be another technologies also which could reduce CO2 from atmosphere.

question already asked 20 year ago without the new nano hype

https://www.osti.gov/scitech/servlets/purl/658219

@Ketaki Deshmukh    You state above 'The whole point of discussion and my question is to find out the solution for increased global warming' but your question asks 'Do you think, can nanomaterials be used to convert CO2 into O2? If yes what is the feasibility?'

No-one questions the laudability of somehow trapping the CO2 in the atmosphere (as Kenneth correctly hints - we must trap the 'O2' part as well as the 'C' part).  My entire thesis was that the reaction you propose (CO2 -> C + O2) is thermodynamically unfeasible and no amount of nanomaterial in catalyst form will accelerate or aid this reaction. If there is some selective absorption on a high specific surface area material (and nanomaterials have high SSA) and then some route of sequestrating the CO2 permanently, then maybe such a huge scale project could be contemplated.  We then have to consider the subdivision of material to nanoform constantly making new surface or the bottom up approach.  As Kenneth states, the scale of the problem is close to impossible to contemplate.

So, back to my first paragraph.  Your question hints at something else, but you do not state this.  Your actual  question has been answered correctly but you had a hidden meaning behind it.....

On a pedantic point, it seems that the difference between 'lose' and 'loose' can be easily corrected in text above - a simple typo?

Dear Ketaki,

 You've received a lot of sensible answers already. For me, these summarize to: look what products naturally occur, and can still react with CO2. If you do not have it as a natural source, you'll find yourself running around in circles (producing what you need), and/or hunt for more CO2-zero-energy than we currently need.

 And as has been hinted by others: only basic chemistry and physics is needed to do a basic reality check of most solutions.

 Concretely:

CaO does not occur in nature, because it is too reactive. Same goes for the other examples that were listed.

 You would therefore look for minerals in rocks that are not in equilibrium with the atmosphere. Basalts are a typical example, but about any mafic rock will work.

 When such rocks weather, they will take up CO2. It is claimed that theoretically you can mine and grind enough fresh rocks, in order for them to react fast enough to take up all anthropogenic CO2 without further effort. After hearing a presentation on this, I did the math: the volumes required did not make it a very really realistic option...

 What does e.g. seem to work is using basalt reservoirs to inject CO2, and thus trigger fast mineralisation reactions. First test were I believe in the US, currently projects in Iceland seem to be promising. But you need to be sitting on the right geology.

We do indeed have moved away quite a bit from your original question.

Dear Kenneth,

 Just the reaction as a geologist on some of your statements. In spite to what I advised to Ketaki regarding 'basic chemistry and physics', your '44 pounds back into a 12 pound geological bag' does not hold true.

 A geological reservoir is not a container with a fixed volume or mass constraint. It is pressure that constraints its limits. That is why:

• CO2 can be injected in aquifers where nothing was extracted from. The demonstration projects are out there.
• According to calculations, a CO2-EOR project (Enhanced Oil Recovery) may store more CO2 than is released from burning the produced oil. 

This is true even without considering extensive reservoir engineering (pressure management) or longer-term effects such as CO2 moving into solution.

With this, I do not claim that different types of CCS can solve climate change, but they can play a significant role, also when considering negative-emissions.

When it comes to biomass, I do share your concerns: this is not sequestration, rather a buffer with a life time of decades to centuries.

@ Kris Piessens  I think you may be misinterpreting Kenneth's '44 pounds into a 12 pound geological bag'.  I believe that he is referring to the atomic masses of CO2 (44) and carbon (12) indicating that the oxygen within CO2 will need to be 'buried' along with the carbon.  I'm sure he (as well as I) understand that burial (of CO2) under pressure is an option.

Dear Alan, 

Had to think about your answer for a couple of minutes, because you explain the remark of Kenneth exactly the way I read it (I think): one needs to take into account an increase of mass/quantity of the order or 44/12 when (re-)injecting CO2 that was produced as (H)C. If I understand well, this is put forward as a main reservation/limitation of CCS. 

Therefore, after wondering a bit, I believe there may be some 'interdisciplinary' confusion in play. The point I wanted to make, is not that the CO2 is injected under pressure (compressed to a liquid like density if in equilibrium with prevailing fluid pressures at those depths). Although of course this is true and important. 

The point I wanted to make is that a geological reservoir strictly speaking does not have a 'given volume'. Injecting at (slight) over-pressure, will in suited locations have a footprint that is large in volume, but small in magnitude: the saline groundwater will move just enough to make room for the CO2, but the pressure is redistributed over a much larger area/volume until a large-scale new equilibrium is reached. 

The same may happen in the opposite case as well, when producing oil or gas: if the initial reservoir pressure is restored, then this indicates good communication with other reservoirs. Of course this is not always the case, and discussing these situations would lead a bit far. Nevertheless, as an example, incorrect injection of CO2 would not necessarily lead to the escape of CO2, but can equally at a significant distance of the injection point cause the expulsion of brine into a shallower aquifer that is maybe used as groundwater resource. 

Looking at injection of CO2 strictly as a volume problem is of course also possible: volumes need to be respected. At these scales, the compressibility of the rock matrix and the fluids (also the aqueous ones) become important. Pressure increase also leads to absidence (as the opposite of subsidence), which may be, but often is not, detectable. However, again very minor amounts correspond to large volumes. 

And lastly, the part of the subsurface occupied by HC-reservoirs is minor compared to the one occupied by deep aquifers. CO2 geological storage can happen in both, so it is not simple replacing HC by CO2 at the same location. 

Hope I interpreted your remark correctly. And again, I'm not proposing CCS as an easy, sole or complete solution, but do not like to see it put aside, especially not for the wrong reasons. 

Hello Kris   Thanks for your helpful comments.  Perhaps we are talking at cross purposes here.  I'm simply concerned with the poster's original question. One has to 'get rid of' CO2 not C.  And there are 44 units of the former in relation to 12 units of the latter.  We can't (practically) convert the CO2 to C (coal, graphite, or diamond?!).   In terms of underground reservoirs then I can understand that these would operate under pressure to keep the CO2 as (densified - liquid or, more likely, solid) CO2 (avoiding leaks etc).  The scale of the problem is immense as Kenneth tells us.

 How about artificial photosynthesis, carried out using nanomaterials. So the efficiency will be more and space required to create set up for artificial photosynthesis will be less. I dont know what nanomaterial will be feasible to use or is this possible or not? 

I know I am not eligible enough to comment on this topic infront of topic experts like you but I have studied somewhere that direct molecular oxygen production in CO2 photodissociation is possible. Please refer article: DOI: 10.1126/science.1257156

Unfortunately, completely uneconomic, impractical, and still no CO2 'balance' is shown:

https://lnkd.in/dWDzvwa