The adsorption performance of multiwalled carbon nanotubes (MWCNTs), resorcinol-formaldehyde xerogel/CNTs (RFX/MWCNTs), and its hydrothermally carbonized sample (C-RFX/MWCNTs) towards the removal of crystal violet dye using a fixed bed column is investigated. The produced samples were characterized with TEM, FTIR, and N2 adsorption tests. In terms of CV adsorption performance, the impact of flow rate, bed height, and intake concentration on breakthrough curves was evaluated. To forecast column performance, the Wolborska, Adam-Bohart, and Clark models were being used. MWCNTs have typical sizes ranging from 30 to 60 nm, according to TEM analysis. C-RFX/MWCNTs displayed more oxygenated functional groups as well as an increase in internal porosity after hydrothermal carbonization. The capacity of the adsorption bed increased with increasing bed height, reducing flow rate, and decreasing initial dye concentration, according to the results of the column. The findings of the experiments revealed that the hydrothermally carbonized sample (C- RFX/MWCNTs) is a quite effective adsorbent for uptaking the crystal violet dye.