Study of the Biosorptive Capacity of Avocado Seed (Persea americana) for the Removal of Lead (II) from Aqueous Solutions

Abstract

Ground avocado seeds (Persea americana) were evaluated as an adsorbent material for lead (II) ions present in contaminated water. An experimental study was conducted using a 4² factorial design to determine how particle diameters (425 and 125 μm) and the initial metal concentrations (48.8, 195.8, 346.3, and 494.5 mg/L) affect the retention capacities of the biosorbent. Through FTIR spectroscopy, several chemical groups (–OH, –C=O, –NH₂, and –COOH) were identified in the biomass. The adsorption capacity was 74.4 mg/g at an initial concentration of 494.5 mg/L, a pH of 4.5, and a particle size diameter of 125 μm, whereas the results obtained with a diameter of 425 μm were lower. The data fitted to the Langmuir model with an R² value of 0.9904. This is consistent with an equilibrium description based on homogeneous sites, with a maximum capacity of 73.0 mg/g. Regarding the process rate, the pseudo-second-order kinetic model produced an R² value of 0.9474, providing the best fit. It was concluded that avocado seeds constitute a low-cost biosorbent with suitable performance for the removal of lead (II) from contaminated water, representing a sustainable technique for the treatment of heavy-metal containing effluents.