The removal of contaminated dyes in wastewater via Activated Carbon (AC) technology is a promising alternative to current conventional pollution-free technologies. Herein, the commercial AC with enhanced adsorption performance capacity were comprehensively investigated via modulating with the alkali-acid treatment. The removal of a highly concentrated methylene blue solution was evaluated via a commercial AC treated with deionized water (AC-DI), potassium hydroxide (AC-KOH) and nitric acid (AC-HNO3). The physicochemical properties of the modified AC were characterized using Fourier Transform Infra-Red (FTIR), X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM) and Surface area analyzer and Porosity analysis (SAP). The AC modified with deionized water (AC-DI) exhibited superior adsorption performance with 99 of methylene blue removal within 8 hours. Gratifyingly, the AC-DI has the fastest adsorption uptake within 2 hours in comparison to AC, AC-KOH and AC-HNO3 samples. The superior methylene blue removal performance of AC-DI was attributed to the enhanced surface group functionalization over the surface of AC evidenced from the FTIR analysis. In addition, the better crystallinity of AC-DI sample as shown in XRD and FESEM micrograph analysis does help to improve the adsorption of contaminated dye molecules onto the surface complex of AC, results in a superior rate of methylene blue removal. These results suggest that the alkali-acid treatment shows promises in enhancing the adsorption rate capabilities of commercial AC for the removal of basic dyes from wastewater. © 2019 Author(s).