In this work, pineapple peel (PP) was reused as a precursor in biochar (BC) production at elevated temperatures (i.e., 500–900 °C) for residence times of 0–60 min. The findings showed that pyrolysis temperature and residence time played a vital role in pore development. As pyrolysis temperature increased from 800 to 900 °C for residence times of 20 and 60 min, the data on the Brunauer–Emmett–Teller (BET) surface area of the resulting biochar products significantly jumped from 11.98–32.34 to 119.43–133.40 m²/g. In addition, there was a significant increase in the BET surface area from 1.02 to 133.40 m²/g with the residence time of 0 to 20 min at 900 °C. From the data of the nitrogen adsorption–desorption isotherms and the pore size distribution, both micropores (pore diameters of <2.0 nm) and mesopores (pore diameters of 2.0–50.0 nm) are present in the PP-based biochar products. Due to its good fittings in the pseudo-second-order model and its hydrophilic nature, as seen in the Fourier transform infrared spectroscopy (FTIR), the resulting biochar could be a porous material to be used for the effective removal of cationic compounds (i.e., methylene blue (MB)) from liquid phases.