looking through this closely, my friend asked me to post a few  questions,  69ron:

1 - Powderize your dried cactus. Mix 100 grams of dried powderized cactus with 25 grams of calcium hydroxide. Add 300 ml water to make it feel wet but not watery. Mix for about 5 minutes.

Fine, I get that, no worries. It'll be like a slurry, right? 

2 - Add 300 ml of d-limonene. Mix well. Let sit a few hours.

So the d-lim, base water, cactus are all stewing.

3 - Pour off the d-limonene through a filter. (It's really cool if you use a French Coffee Press for this. Using a French Coffee Press you press the cactus mix and squeeze out the d-limonene to get every last drop of d-limonene out. Then filter it through a paper coffee filter.)

This is where my friend is confused. Do  you mean to use a French coffee press, like a bodum, with a plunger as your initial mixing vessel? So, you'd have all the ingredients in the coffee pot, leave it for an hour or so to break down, then press it. So then you'd have the cactus captured at the bottom under the plunger, then the 300 ml of basic water, then the d-lim, which you'd pour off, and filter through coffee? 

In short, What happens to the base water if you use the french press to squeeze the mix? 

the rest my friend understands. Thanks in advance.