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

Abstract

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.

Desorption of Coffee Pulp Used as an Adsorbent Material for Cr(III and VI) Ions in Synthetic Wastewater: A Preliminary Study

“…Heavy metals (also known as environmentally priority pollutants, Potentially Toxic Elements (PTE), Persistent Bio-accumulative Toxics (PBT), and Unitary Potentially Toxic Residues (UPTR)) [ 3 , 4 , 5 ], are among the pollutants, produced by industrial wastewater, particularly those of an inorganic nature. These pollutants are not removed in conventional wastewater treatment plants (pretreatment, primary, secondary, and tertiary treatment stages) [ 6 ].…”

“…Particularly for the biosorption method, important findings have been reported in the literature regarding the use of sorbents derived from agro-industrial by-products (coffee bagasse, coffee pulp, agave, maguey, sugar cane, organic waste from fruits and vegetables) [ 2 , 5 , 12 ]; solid materials from tannery industrial activities (chrome shavings, leather trimmings, fly ash, and hair) [ 13 , 14 ]; by-products of the incineration of municipal sewage sludge, such as fly ash and slag (chitosan, waste-to-energy power plant, sunflower wood, pine nut shells) [ 15 , 16 , 17 , 18 ]. Additionally, fruit and vegetable waste from the processing of the food industry, as well as the use of γ-polyglutamic acid, elderberries, pine biomass, and mushroom biomass [ 19 , 20 , 21 , 22 ].…”

“…This is favorable because, in this way, it will be more accessible to users who implement this technology and with it, the maximum number of cycles in which the biosorbent can be reused is established. On the other hand, it is relevant to say that if organic and inorganic contaminants remain in solution, they can be reincorporated into the production cycle or life cycle of industrial processes, allowing companies to incorporate a circular economy and at the same time being sustainable, since they will favor environmental, economic, and social factors [ 2 , 5 , 7 , 26 ].…”

“…Regarding the evaluation of agro-industrial by-products in the context of industrial wastewater treatment, which incorporates pollutants such as the aforementioned, coffee pulp (CP) has been investigated in previous studies [ 2 , 5 , 27 ]. This lignocellulosic material generated from the pulping process represents 29% dry-weight of the coffee fruit; 2 tons of this residue are generated for each ton of coffee [ 35 ].…”

Scientometric Overview of Coffee By-Products and Their Applications

“…The pericarp includes the skin (exocarp), mucilage (mesocarp), parchment (endocarp), and the two seeds of the coffee cherry consisting of a peripheral spermoderm or "silverskin", an endosperm (responsible for taste and aroma), and the embryo. Upon harvesting and processing, two main by-products are generated, coffee husk (CH) or coffee pulp (CP), which depends on the post-harvest method to transform the cherry into a green bean [4]. CH is obtained through the dry or semi-dry method (unwashed) and comprises all the pericarp layers, while CP is generated by the wet method (washed) and contains the mucilage and the skin of the cherry.…”