The agricultural waste of rice husk (RH) has been used as bioadsorbent owing to its easy availability and cost effective removal of toxic pollutants like phenols, pesticides, dyes and heavy metals from the effluents. The surface modification of RH is crucial to improve its adsorptive potential towards removing dyes. This chapter outlines the influencing factors like concentration of initial dye, reaction temperature, adsorbent concentration, pH condition, reaction time, and temperature on the adsorptive elimination of cationic and anionic dyes by using RH as a bioadsorbent for wastewater treatment. The elimination of hazardous dyes using rice husk ash (RHA)-derived zeolite under various experimental conditions is also discussed. The interactive nature between the adsorbent and adsorbate can be understood by analyzing the adsorption data using Freundlich and Langmuir isotherms. The method of evaluating the three important thermodynamic parameters, including Gibb’s free energy, change in entropy and enthalpy is also reviewed which helps to comprehend the dye adsorption mechanism with RH and RH-derived bioadsrobents.