Alkaline Modification of Arabica -Coffee and Theobroma -Cocoa Agroindustrial Waste for Effective Removal of Pb(II) from Aqueous Solutions

• Published in: Molecules (Basel, Switzerland) Vol. 28; no. 2; p. 683
• Main Authors: Lavado-Meza, Carmencita, De la Cruz-Cerrón, Leonel, Asencios, Yvan J O, Marcos, Francielle Candian Firmino, Dávalos-Prado, Juan Z
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 10-01-2023; MDPI
• Subjects: Adsorption; Agricultural wastes; agroindustrial waste; Aqueous solutions; Biomass; biosorption; Cacao; Chemisorption; Cocoa; Coffea; Coffee; heavy metals; Hydrogen-Ion Concentration; Kinetics; Lead; Metals; Pb(II) removal; Sodium hydroxide; Spectroscopy, Fourier Transform Infrared; Structural analysis; Theobroma; Thermodynamics; Wastes; Water - chemistry; Water Pollutants, Chemical - chemistry; agroindustrial waste; heavy metals; biosorption; Pb(II) removal
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules28020683

Arabica-coffee and Theobroma-cocoa agroindustrial wastes were treated with NaOH and characterized to efficiently remove Pb(II) from the aqueous media. The maximum Pb(II) adsorption capacities, qmax, of Arabica-coffee (WCAM) and Theobroma-cocoa (WCTM) biosorbents (qmax = 303.0 and 223.1 mg·g−1, respectively) were almost twice that of the corresponding untreated wastes and were higher than those of other similar agro-industrial biosorbents reported in the literature. Structural, chemical, and morphological characterization were performed by FT-IR, SEM/EDX, and point of zero charge (pHPZC) measurements. Both the WCAM and WCTM biosorbents showed typical uneven and rough cracked surfaces including the OH, C=O, COH, and C-O-C functional adsorbing groups. The optimal Pb(II) adsorption, reaching a high removal efficiency %R (>90%), occurred at a pH between 4 and 5 with a biosorbent dose of 2 g·L−1. The experimental data for Pb(II) adsorption on WACM and WCTM were well fitted with the Langmuir-isotherm and pseudo-second order kinetic models. These indicated that Pb(II) adsorption is a chemisorption process with the presence of a monolayer mechanism. In addition, the deduced thermodynamic parameters showed the endothermic (ΔH0 > 0), feasible, and spontaneous (ΔG0 < 0) nature of the adsorption processes studied.