Activated carbons are known to be an efficient way to remove impurities, such as unwanted colors, odors, and precious metal catalysts.

Since they are not as selective as SiliaMetS metal scavengers for metal removal, they are most often used as a pre-treatment to reduce the overall quantities of impurities, which helps achieving desired levels of residual impurities.

The low cost of activated carbons makes them very attractive. However, using charcoal in a lab can become very messy, especially when used in large amounts. I said it before and I will say it again, nobody likes to handle bulk charcoal. The best way to use activated carbons without having to handle it, is to have somebody else handle it for you. And if you do not have an intern for that, a SiliaCarb E-PAK cartridge can do the job.

Yes, someone at SiliCycle did it for you. Since E-PAK is extruded with activated carbon, it is completely clean when it arrives in your lab. And fully scalable too. Once the lab-scale conditions are determined, it can be linearly transferred to a larger scale, like with any other E-PAK cartridges. You can now keep the dirty talk out of your lab.

And just like any other scavengers, the first step is to screen activated carbons for your application.

  • SiliaCarb C-CA is a Chemically Activated wood-based carbon with high adsorptive capacity for high molecular weight organics. Its high surface area and large volume of meso pores allow it to rapidly remove color, taste, and odor compounds from solution.
  • SiliaCarb C-HA is a High-Activity wood-based powdered activated carbon with unusually high adsorptive capacity for a wide range of organic compounds. SiliaCarb C-HA is specially processed to produce a high-purity product with low ash content, low soluble iron, and a pore structure that is optimum for a wide range of applications.
  • SiliaCarb C-VA is a Vegetable Activated carbon produced from pine wood with a controlled pH, a high level of purity and excellent adsorptive capacity. It can be used for the decolorization and purification of a large variety of agro-food products, especially saccharose (cane and beet sugar) and liquid sugar as well as the removal of color and its precursors.
  • SiliaCarb C-VW is a Virgin Wood-based activated carbon with superior catalytic activity and ultra-high purity for water purification. Highly effective for removing chloramine and chlorine.

Activated Carbon Compared to Chromatography

You can also avoid handling bulk activated carbon by using chromatography instead. It often is the first thing that comes to the mind of an organic chemist (like me) trying to purify a crude product.

Activated carbon was compared to silica gel chromatography in the clean-up of a cycloisomerisation reaction in the Application Note Appn_SM009-0 Different Ways of Removing Rhodium.

The quantity of sorbent and solvent used was significantly reduced with activated carbon compared to bare silica gel. And the final rhodium concentration was smaller with activated carbon, and even smaller with an activated carbon E-PAK cartridge.

While the experiment time was longer for activated carbon than with chromatography, this time is expected to stay the same when scaling up the purification. On the other hand, you know as much as I do that scaling up a silica gel column can exponentially increase the experiment time. And the pain.

More than that, when it comes to setting up the large-scale experiment, using E-PAK cartridges is faster than bulk. Apart from not needing to handle bulk material, you also save time with the cartridges.

Preliminary Clean-Up of Residual Metals with Activated Carbon

Activated carbons might not be as selective as metal scavengers to remove residual metals, but they can be used as a pre-treatment that significantly reduces the quantity of metal in the crude product before a SiliaMetS treatment, reducing the overall cost of the purification.

With E-PAK cartridges connected in series, the activated carbon pre-treatment can be done directly.

Moreover, in the clean-up of a Sonogashira coupling, with the crude product contaminated with both copper and palladium, presented in the Application Note Appn_EP007 Scaling up a Sonogashira Reaction with E-PAK, the activated carbon pre-treatment was sufficient to reduce residual copper concentration from 895 ppm to less than 5 ppm using SiliaCarb

C-VW, 50 % loading, at room temperature in ethyl acetate, corresponding to 99 % scavenging. This experiment was later scaled-up to a pilot scale 12.5 x 16.5 cm cartridges.

And this is one of the many examples (Appn_EP002, Appn_EP004, Appn_EP005 and Appn_EP008) in which a SiliaCarb pre-treatment helped reduce the impurities before the usual scavenger treatment.

Removing Color from a Biomass Sample

Activated carbons can be used to remove unwanted colors. In the Application Note Appn_EP006-0 Using E-PAK technology to remove chlorophyll in a biomass sample, chlorophyll was causing a green hue to the biomass sample.

The different activated carbons were tested, and SiliaCarb C-HA cartridges were the best at removing chlorophyll, and hence unwanted color, from the product of interest. Each cuvette in the picture above corresponds to 350 mL of extract (15 g/L solutes) passed through a SiliaCarb C-HA activated carbon E-PAK cartridge.

With SiliaCarb E-PAK cartridges, no need to handle bulk activated carbon. A win-win situation.

How to Use Activated Carbons

SiliaCarb activated carbons are somewhat like SiliaMetS metal scavengers. We already mentioned the need to screen them, then the same optimization procedure (from Application note Appn_SM001-1 Experimental Procedure Optimization for SiliaMetS Metal Scavengers) can be followed. Both are transferable to E-PAK and adaptable to large scales.

Activated carbons are stable in a wide range of solvents and in pH from 1 to 13 when in aqueous solvents.

Unlike metal scavengers, a molar equivalent cannot be calculated for activated carbons, so of the two methods presented in this video, you should calculate the amount of activated carbons using the weight/weight method. The E-PAK cartridge is then selected based on the weight of activated carbon required.

Activated carbons are often used as a pre-treatment to scavengers but can also be used on their own for odor, color, or metal removal.

In short, you can save yourself (and your unlucky intern) from handling bulk charcoal with SiliaCarb E-PAK cartridges. You can get better yields, scalable results and save time in the process.

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