Biosorption of Pb(II) Using Coffee Pulp as a Sustainable Alternative for Wastewater Treatment

The present research shows the results obtained from the biosorption process of Pb, using coffee pulp as a biosorbent in synthetic waters. To do this, the lignin and cellulose content and the percentage of removal of Pb²⁺ ions was determined; additionally, the sorption’s optimal variables, such as the optimum pH, the point of zero charge (pHpzc), the kinetics and the adsorption isotherm, were determined. A comparison was made with other by-products derived from coffee crops. According to the results obtained in this research, the cellulose percentage was 29.12 ± 0.22% and the lignin percentage was 19.25 ± 0.16% in the coffee pulp, the optimum pH was 2.0 units and the kinetic model, which adjusted to the biosorption’s process, was the pseudo-second order of Ho and McKay, presenting an isotherm of Langmuir’s model and pHpzc of 3.95 units. Lastly, the removal of the pollutant was 86.45%, with a capacity of maximum adsorption of 24.10 mg·g⁻¹ obtained with a particle size of 180 µm, time of contact of 105 min and at 100 RPM. Finally, we express that (a) the coffee pulp can be used as a sustainable alternative for the removal of the pollutant mentioned in synthetic and/or industrial wastewater matrices, to meet goals 3.9 and 6.9 of the Sustainable Development Goals of the 2030 agenda, and (b) the novelty of this research is the use of an agricultural waste of easy acquisition as a sorbent, without chemical modification, since it presented a high percentage of efficiency in the removal of Pb²⁺ ions. In turn, the challenge of this research is implementing this green technology on a pilot, semi-industrial and/or industrial scale in wastewater treatment systems.