Rice husk, as local agricultural waste, was modified by treating it with H2SO4 to obtain a low-cost and an effective adsorbent. This adsorbent was investigated for the removal of basic violet 10 (BV) and basic yellow 28 (BY) dyes from aqueous solutions via batch adsorption procedure. The experiments included the initial concentration of dye, contact time and temperature. Langmuir, Freundlich, and Dubinin–Radushkevich models were studied to follow the adsorption process. The results reveal that the Langmuir model showed a better fit to the equilibrium adsorption data and the adsorption kinetics fit the pseudo-second-order model. Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) were used in the course of characterization. The intraparticle diffusion model via the mass transfer was applied to examine the mechanisms of the rate-controlling step. It was found that intraparticle diffusion was mostly the rate controlling step in the adsorption of BV dye only, while the thermodynamic parameters (ΔH˚, ΔS˚, and ΔG˚) showed that the adsorption process is a typical chemical, spontaneous, and exothermic in nature.