Polymer-derived ceramic components (SiOC, sample W) were produced from preceramic polymer mixture and a catalyst. After curing and pyrolysis, some of the samples etched by hydrofluoric acid to obtain carbonaceous SiOC (C-rich SiOC, sample W-HF). W and W-HF were tested as an adsorbent material to remove both heavy-metal ions (Cr (III), Pb (III), and Cd (II)) and cationic dyes (Methylene Blue (MB), Rhodamine B (RB), and Crystal Violet (CV)) from aqueous solutions. HF-treated high surface area SiOC samples had quite high adsorption affinity for cationic dyes. According the Langmuir isotherm model the maximum dye uptake values were found to be around to 50 mg/g for sample W, whereas those for sample W-HF ranged from 104 to 186 mg/g. Regeneration studies were conducted both by heat treatment and leaching, high recovery yields (always above 97%) of MB adsorption were obtained.