This article presents two prototypes of laboratory magnetic separators that generate high gradient magnetic fields. Such a field is created in a separation cell via steel wool. The efficiency of separators was tested on a water suspension containing weakly magnetic Fe2O3 nano/micro-particles, prepared in three size fractions in a size range of 60 nm - 10 m. The separation process was evaluated via optical transmittance of the suspension before and after sequential separation processes. Repeated separations on the same sample exhibit an asymptotic trend that results in the conclusion that it is not possible to trap all solid content. According to the decrease of solid particles concentrations during cyclic separation we set the efficiency of the process. It is maximally 46% for fine fraction, 65% for medium fraction, and 40% for coarse fraction after infinity separation cycles.