Beneficiation refers to processes which concentrate desired materials out of collected ore. In a lunar context, the ore proposed is most commonly the finely powdered lunar regolith. Many of processes suggested for lunar use are adaptations of those used terrestrially.
Materials that are at least weakly magnetic can be concentrated by use of a magnetic field. This is most commonly accomplished terrestrially by use of a drum-shaped electromagnet, which rotates as the input material is poured over it. Magnetic materials stick to the drum and are scraped off the other side, while the non-magnetic materials fall straight down.
Another method is to let the material fall through a chamber with magnet one side. Magnetic materials will be deflected by different amounts depending on the how magnetic they are, falling into multiple bins below. The low gravity (1/6 that of earth) and vacuum environment found on the moon greatly enhance this process. Low gravity allows even small chambers to provide large separation, as the material falls much more slowly then on earth. Lack of atmosphere eliminates turbulence that can remix the separated components, as well as removing air resistance, making each grain fall at the same rate regardless of its density or size.
Electrostatic beneficiation is similar to magnetic beneficiation, except that instead of using magnetic attraction, electrostatic attraction/repulsion is used. The material gathered is electrically charged by either running it over a charged surface, or using an electron beam. This charged material is then separated using a charged plate, either as a drum or in a gravitationally assisted separation chamber, as is done in magnetic beneficiation.
This process has the advantage of being useable on a wider range of minerals than by using magnets, as all minerals have some propensity to absorb electric charge, and most lunar materials have very different values from each other.
Electrostatic beneficiation could be utilized in conjunction with magnetic beneficiation, the magnetic materials removed first, followed by electrostatic separation of any additional minerals desired.