Question

Let's take a piece of wood and put it in water and get it out after a minute. What kind of adsorption do you think would be at play here?

• A. Positive adsorption
• B. Negative adsorption
• C. Desorption
• D. None

Answer 1

The correct option is A Positive adsorption

If we remove the wood piece out, we will see that most of the water is just sticking to the surface but hasn't seeped in significantly. If we had kept the wood in for longer, you can be sure that the water would be absorbed more.
In this case however, it is safe to say that the adsorption is positive adsorption since a major portion would be on the surface only.
For a refresher, let's look at the definition of positive adsorption again.
When the concentration of the adsorbate is more on the surface of adsorbent relative to its concentration in the bulk, it is called positive adsorption.