ABSTRACTSpent rooibos (Aspalathus linearis) tea biomass can be used as an inexpensive biosorbent for xenobiotic removal. Seventeen dyes have been tested for their affinity to spent rooibos tea biomass. Eight dyes were used to study the adsorption process in detail. The dye adsorption has been described with the Langmuir isotherm. The calculated maximum adsorption capacities reached the value of over 200 mg of dye per gram of dried rooibos biomass for Bismarck brown Y. Spent rooibos tea biomass was also magnetically modified by contact with microwave-synthesized magnetic iron oxide nano- and microparticles. This new type of magnetically responsive biocomposite material can be easily separated by means of strong permanent magnets. Both native and magnetically modified spent rooibos biomass have shown excellent adsorption capacities for various types of organic dyes, so they are highly promising adsorbents in environmental technologies for selected xenobiotic removal.