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.
Highlights
Heavy metals are considered as priority inorganic environmental pollutants, and these substances have become one of the most serious environmental problems that must be mitigated to protect humans and the environment [1]
The Environmental Performance Index (EPI) requires the collection of data in the areas of water resources, sustainable agriculture, waste management, threats to biodiversity and heavy metals—different from lead—that are in the list of the thirteen mentioned by the World Health Organization (WHO) [2]
The EPI requires the collection of data in the areas of epidemiological studies of the Global Burden of Disease Study (GBD) Health Assessment, water resources, sustainable waste management, threats to biodiversity and since it is considered one of agriculture, the most important environmental threats to the health of heavy metals—different from lead—that are in the list of the thirteen mentioned by pregnant women and children [2]
Summary
Heavy metals are considered as priority inorganic environmental pollutants, and these substances have become one of the most serious environmental problems that must be mitigated to protect humans and the environment [1]. De Angelis—ranks 180 countries, considering 32 indicators and 11 environmental categories formulated until 2020, regarding two main objectives that go hand in hand with the SDGs: environmental health (with a weight of 40%) and ecosystem vitality (with a weight of 60%) [2] This metric seeks to provide the countries with information about how close they are to the goals set out in their environmental policies, with the aim of improving them to become sustainable leaders. Due to this aspect, the EPI requires the collection of data in the areas of water resources, sustainable agriculture, waste management, threats to biodiversity and heavy metals—different from lead—that are in the list of the thirteen mentioned by the WHO [2].
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