Kindly read some basic books on carbon chemistry , the ultimate oxidation of carbon is carbon dioxide and before that the carboxylate group is formed as nitric acid is oxidizing ( if you take wood powder and oxidize it  by concentrated nitric acid you will end up with oxalic acid)  and at high temperature concentrated sulfuric acid is also oxidizing ( Recall that even diamond is oxidized to carbon dioxide on treating with heated concentrated sulfuric acid).  Some carbon compounds ( aliphatic type ) gets nitration on carbon center by nitric acid and these nitro group isomerizes to isonitro group, I mean from C-NO2 to C-ONO  and the later on hydrolysis readily form C-OH . CNTs and related molecules have aromatic properties and also other properties as these are not ideal sp2 hybrid  but have something in between sp3 and sp2 hybridization ( due to curve surface) and  so display  varied chemical reactions  but are difficult to execute because of stability.

In my knowledge, it is not a detailed chemical path to the acid treatment of carbon nanotubes. Furthermore, you should be more precise, because maybe it depends on the acid used. Perhaps, when considering the chemical reaction of carbon nanotubes you should think about the chemistry of aromatic compounds.

Dr Tardani is correct

Acid treatment may introduce structural defects, functional groups, end opening etc.  It depends on the acid and the method of treatment

Acid treatment of CNT can increase their solubility in various solvents due to the result of functionalization at the CNT surfaces.

THank you all

yes i am use mixture of these acids

But still , how carboxylic acid and hydroxyl acid from  ?

thanks

Kindly read some basic books on carbon chemistry , the ultimate oxidation of carbon is carbon dioxide and before that the carboxylate group is formed as nitric acid is oxidizing ( if you take wood powder and oxidize it  by concentrated nitric acid you will end up with oxalic acid)  and at high temperature concentrated sulfuric acid is also oxidizing ( Recall that even diamond is oxidized to carbon dioxide on treating with heated concentrated sulfuric acid).  Some carbon compounds ( aliphatic type ) gets nitration on carbon center by nitric acid and these nitro group isomerizes to isonitro group, I mean from C-NO2 to C-ONO  and the later on hydrolysis readily form C-OH . CNTs and related molecules have aromatic properties and also other properties as these are not ideal sp2 hybrid  but have something in between sp3 and sp2 hybridization ( due to curve surface) and  so display  varied chemical reactions  but are difficult to execute because of stability.

As it was discussed, the reaction of carbon nanotubes depends on the type of acid. Mainly, the principal question is, do you use oxidative acids or other type of acids. If you use acids with oxidative power,  the oxidation of C-C-bonds leads to formation of CO2 or COOH functions, or introducing (addition-like reaction) of some other functions derives from the acids (e.g. sulphonation, nitro group, etc).  Hydrolysis of these groups can lead to form of OH functions.  More detail should be given about your system to give you excta answer.

Thank you all ,

As far as i understand acid treatment may introduce functional groups, structural defects,end opening and may also effect the solubility of CNTs, etc. It depends on the acid and the method of treatment. If you use a mixture of Sulfuric and nitric acid, then either carboxylation or sulfonation takes place.  The product depends on the type of acid used, the oxidation of C-C-bonds leads to formation of CO2 or -COOH group, or introducing (addition-like reaction) of some other functionional groups derive from the acids (e.g. nitro and sulphate group, etc). Hydrolysis of these groups can lead to introduction of -OH group into the CNT matrix. 

Thank you all ,