Is there an easy, at-home method to separate the protein from sweet whey powder?
While it is not possible to conclusively say something cannot be done&mdash;and perhaps someone will come along who can offer additional insight&mdash;I don't think it is practical to separate the protein from sweet whey powder at home.

It is highly likely that the reason the concentrated protein is considerably more expensive per unit weight is because it is difficult and energy intensive to separate from the whey, and doing so requires expensive capital equipment that must be paid for.



In researching how this is done, I found the following sources:

See this transcript from NPR, which explains the industrial process required to separate the protein from the sugars in whey.  It involves industrial type filters, and considerable equipment.  Admittedly, some of that is due to the scale of the plant which would not apply at home, but the process is only feasible due to the scale of the plant.

According to NIH, a centrifuge is nearly always required, which is not typical home equipment:


  The first step in a typical protein-purification scheme is
  centrifugation. The principle behind centrifugation is that two
  particles in suspension (cells, organelles, or molecules), having
  different masses or densities will settle to the bottom of a tube at
  different rates. Remember, mass is the weight of a sample (measured in
  grams), whereas density is the ratio of its weight to volume
  (grams/liter). Proteins vary greatly in mass but not in density. The
  average density of a protein is 1.37 g/cm3. Unless a protein has an
  attached lipid or carbohydrate, its density will not vary by more than
  15 percent from this value.