Coffee is one of the most consumed beverages worldwide. Its production generates a large amount of waste, and its use is of vital importance to prevent it from becoming a source of environmental pollution. Cuba is a country with a well-known coffee-growing tradition. Although coffee production has decreased, it is vitally important to use the waste generated in these productions to reduce environmental pollution. To know the possible use or application of coffee waste, it is necessary to know its composition. In this article, three Cuban Arabica coffee wastes (husk, parchment and spent coffee grounds) were characterized using chemical, physical and physicochemical methods. In the characterization of these wastes, SEM and EDX were used to determine their microscopic form and chemical composition. The Chesson–Datta method, ATR and TGA were used to determine whether these materials were lignocellulosic. Ash, pH and density of the waste were determined as characterization methods. The extractive content was determined and a phytochemical screening was performed to determine the groups of the secondary metabolites present.

Intensive agricultural production generates significant lignocellulosic waste while contributing to heavy metal pollution, particularly copper (Cu(II)). Synthesizing low-cost nanocomposites from agricultural by-products offers a sustainable circular-economy strategy for water remediation. Here, lignin–silica nanocomposites (LSNCs) were synthesized via a sol–gel method using two abundant Cuban agro-industrial wastes: rice husk and coffee parchment. Physico-chemical characterization (FT-IR, TEM, and TGA) revealed spherical particles (50–60 nm) whose silica contents reflected their parent materials (52% for rice husk vs. 11% for coffee parchment). Batch adsorption experiments showed rapid Cu(II) uptake, with the dissolved Cu(II) concentration exhibiting an apparent plateau from the first sampling point at 10 min onward. The Sips isotherm model best described the process, yielding model-predicted maximum apparent sorption capacity (q_m) of 15 mg/g for rice husk-derived LSNC and 12 mg/g for coffee parchment-derived LSNC. These findings demonstrate that valorizing local agricultural waste into functional nanocomposites provides a low-cost platform for heavy metal adsorption. Coffee parchment and rice husk were successfully used as precursors for lignin/silica nanocomposites that reduced dissolved Cu(II) concentrations in batch aqueous experiments; however, the contribution of adsorption could not be separated from possible precipitation.

Intensive agricultural production generates large volumes of lignocellulosic residues and contributes to heavy metal pollution, particularly copper (Cu). The valorization of these by-products as low-cost adsorbents offers a promising strategy for circular economy implementation and environmental remediation. In this study, lignin–silica nanocomposites were synthesized via a sol–gel process from two abundantly available agricultural wastes in Cuba: rice husk and coffee parchment. The nanocomposites were characterized by FT-IR, TEM and TGA methods. The nanocomposites showed a spherical shape and a diameter between 50 and 60 nm and their silica composition depended on the composition of the starting material. The nanocomposite obtained from rice husk had a silica ratio of 52 % while in the one prepared from coffee parchment it was 11 %. Adsorption capacities and adsorption behaviors with Cu(II) in water of the nanocomposites were studied. The adsorbents reached equilibrium within 10 minutes and the estimated maximum sorption capacities were 15 mg/g using rice husk as the starting material and 12 mg/g for the one prepared from coffee parchment. Nanocomposite synthesis is a promising route for lignocellulosic biomass revalorization as heavy metal adsorbents for environmental sanitation.