This research used leftover pineapple peel from a fruit shop to adsorb Basic Red 9 dye and Direct Red 83 dye. Pineapple peel was modified with 1.25 M calcium chloride before conducting adsorption experiments. The studied parameters that affect adsorption efficiency included time, pH, adsorbent quantity, dye concentration in the wastewater, and temperature. Both dyes showed the best adsorption at pH 7. Basic Red 9 and Direct Red 83 took 60 and 90 min, respectively, to reach equilibrium reactions. As the quantity of pineapple peel increased, the adsorption capacity increased. Temperature slightly affected the dye adsorption. The adsorption isotherms of Basic Red 9 and Direct Red 83 followed the Temkin and Freundlichad sorption models, whereas the adsorption kinetics of the two were consistent with the pseudo-second-order equation. The adsorption was endothermic and spontaneous.
