Abstract: A supporting web of synthetic fibers in which a permanently magnetic powder s embedded is used to hold fine magnetic particles in a matrix for interaction with dissolved or dispersed substances present in a liquid or gas flowing through the matrix. The magnetic force in the supporting web produced by the embedded powder lends flow resistance to the adhering particle matrix making it possible to use smaller particles effectively. Catalytic effects can be produced if the magnetic particles are coated with a nonmagnetic material having a catalytic effect for the dissolved or suspended substance, as the coating does not interfere with the tenacity of the magnetically supported matrix. A matrix with particles of a ferrimagnetic compound are useful for removal of metal ions and metal complex ions from water solution as for example uranium.