Regenerating actived carbon with NaOh

[Cory]

Im attepting to regenerate rox .8 with sodium hydroxide pellets. I added hot water and a few tablespoons of NaOh. It bubbles a lot then the water gradually turns brown. I think its working.

Question: would it be safe to rinse it in ro water after treatment and use it? My concern is ph.

Abstract
Spent activated carbon (SAC) must either be disposed of at a landfill or regenerated and reused in industries. Regeneration of SAC is a more preferable option as it can cut down replacement and disposal cost as well as reduce secondary pollution. Chemical regeneration is more suitable and economically feasible option for small-scale industrial application as compared to thermal regeneration. In this study, SAC is regenerated using sodium hydroxide (NaOH) solution and hot water. The aim of this study is to evaluate the effectiveness of NaOH and hot water regeneration of SAC. The optimal regeneration condition for SAC was determined and the regeneration performance was assessed by iodine and methylene blue (MB) adsorption test. Finding shows the optimal regeneration condition of carbon regeneration is 15 mL of 6 N of NaOH solution per g of carbon with 30 min of contact time. The estimated surface area, micropore volume, and total pore volume of batch and column regenerated SAC were 899.1 m2/g, 0.8702 cm3/g, 0.9521 cm3/g; and 849.0 m2/g, 0.8519 cm3/g, and 0.9450 cm3/g, respectively. The regeneration efficiency of regenerated SAC is comparable to fresh activated carbon with regeneration efficiency more than 90% in iodine adsorption test and 98% in MB adsorption test.

 

[Randy Holmes-Farley Verified Community Expert]

I don’t think this type of regeneration will work well for aquarium GAC.

 

[Randy Holmes-Farley Verified Community Expert]

Lots of rinsing will lower the pH, and some vinegar or baking soda will help.

 

[Cory]

I don’t think this type of regeneration will work well for aquarium GAC.

What are your thoughts about it?

 

[Cory]

Lots of rinsing will lower the pH, and some vinegar or baking soda will help.

Vinegar will absorb into the carbon? I mean will it redice its effectiveness?Can i use muriatic acid as a more effective way?

 

[taricha]

It bubbles a lot then the water gradually turns brown.

Can you describe anything about the brown that presumably came off the GAC?

@Dan_P I wonder if something like this is a way to concentrate the material that GAC removes.

 

[Cory]

Can you describe anything about the brown that presumably came off the GAC?

@Dan_P I wonder if something like this is a way to concentrate the material that GAC removes.

Just a brown liquid but its like yellow aquarium water.

Like this pic

 

[Dan_P]

Can you describe anything about the brown that presumably came off the GAC?

@Dan_P I wonder if something like this is a way to concentrate the material that GAC removes.

It certainly seems like it would but contaminated with all the biomass growing on the carbon. You might have to first clean the GAC surface before the base treatment. On small scale, sonication should be investigated, though it might reduce GAC to dust.

I wonder if new GAC washed with hydroxide also produced a brown liquid. The color level of the wash might be indicative of how spent the GAC is. Not as straightforward a diagnostic as methylene blue adsorption or iodine number.

It would be very convenient if ammonium hydroxide worked because the excess base would be removed by evaporation.

 

[Randy Holmes-Farley Verified Community Expert]

Vinegar will absorb into the carbon? I mean will it redice its effectiveness?Can i use muriatic acid as a more effective way?

No, it is too small and hydrophilic to remain attached to GAC once in aquarium water.

 

[Randy Holmes-Farley Verified Community Expert]

What are your thoughts about it?

There are lots and lots of papers that claim to show regeneration of GAC with all sorts of chemicals that are designed to displace certain things attached to GAC.

And they certainly have "some" effectiveness at removing some types of bound absorbants.

But none of these chemical treatments are widely used.

Let's look at the paper you posted and what it is trying to remove:

"SAC and FAC samples in this study were charcoal-type AC. The SAC sample was supplied by Meridian World Sdn. Bhd., an industrial waste management company located at Sungai Petani, Kedah, Malaysia. The SAC was previously used in industrial applications for odor removal "

So what is being removed are specific small molecule odorants. This process is not shown to remove bacteria and proteins and other large hydrophobic molecules that may attach to the GAC and remain essentially permanently.

While I think very hot and strong hydroxide will eventually remove proteins by hydrolyzing them into amino acids, that is not a simple and quick process, and might possibly damage the GAC.