Utilizing Artocarpus altilis (breadfruit) skin for the removal of malachite green: isotherm, kinetics, regeneration, and column studies

Tropical fruit waste, breadfruit skin (BS), demonstrates great potential as a low-cost adsorbent for the removal of toxic malachite green (MG) dye. The optimum values of shaking time, settling time, and pH for the interaction of MG on BS are determined to be 3.5 h, 1 h, and pH 4.58, respectively. Further, adsorption of MG by BS is ionic strength dependent. Six isotherm models analyzed using adsorption equilibrium data indicate that the MG-BS adsorbate-adsorbent system can be best described by the Langmuir model with the maximum adsorption capacity (q(max)) of 55.2 mg g(-1), which is further confirmed by six different error functions. This adsorption system follows the pseudo-second-order kinetics, and the intraparticle diffusion could be the rate-determining step. Regeneration studies using NaOH washing illustrate the ability of BS to retain its high adsorption capacity of >90% even after 5 consecutive cycles. Column study reveals that more than 1,200 mL of 100 mg L-1 MG solution can be introduced to the column for up to 95% dye removal.