Publication:
Adsorption of pollutants by spent-coffee-grounds composite beads

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Authors
Torres Cabán, Roberto José
Embargoed Until
Advisor
Vega Olivencia, Carmen A.
College
College of Arts and Sciences - Sciences
Department
Department of Chemistry
Degree Level
Ph.D.
Publisher
Date
2020-05-19
Abstract
The use of heavy metals in technological applications has led to detrimental effects on the environment. Activated carbon is commonly used to remove pollutants but it is expensive. Therefore, the research of low-cost alternatives derived from organic wastes is being considered. This study considers the use of Calcium Alginate/Spent Coffee Grounds (CA–SCGs) composite beads to adsorb heavy metals from aqueous solutions. The studied metals were Cu2+, Ni2+ and Cd2+ at concentrations from 10 ppm to 100 ppm. CA–SCGs beads were made of alginate and spent coffee grounds. They were compared with calcium alginate beads (CA beads) and spent coffee grounds (SCGs) in terms of capacity and rate of adsorption. Three cycles of adsorption/desorption were done for Cd2+ and Ni2+. The beads were characterized by Scanning Electron Microscopy coupled with an energy-dispersive X-ray spectroscopy (SEM–EDX), Fourier-transform infrared spectroscopy (FT–IR), Raman spectroscopy, and point of zero charge. Langmuir, Freundlich, and Sips models and a pseudo-second-order kinetic equation were used. Sips model showed the best correlation with the adsorption of CA–SCGs beads with capacities of adsorption of 91.18 mg/g for cadmium, 42.06 mg/g for copper and 20.96 mg/g for nickel. The major advantage of SCGs and CA-SCGs beads versus CA beads is that the adsorption sites of SCGs showed faster adsorption and larger percentages of removal, especially in the lower range of concentrations (10 ppm to 30 ppm). Ion exchange of divalent metals is the main mechanism of adsorption of CA but adsorption onto deprotonated carboxyl and phenolic sites can be the dominant mechanism of SCGs. Paracetamol is one of the most often detected pharmaceutical products in surface water. Paracetamol in the environment can have potential harmful effects. Activated carbon is also an effective adsorbent of paracetamol but it is expensive. Chitosan-Spent Coffee Grounds beads (Chitosan–SCGs beads) were studied to remove paracetamol from an aqueous solution. Cyclic Voltammetry technique was used due its good signal for paracetamol and the wider range of concentrations than can be used without any further process of the sample. The maximum adsorption capacity predicted by the Sips model was 12.71 mg/g.

El uso de metales pesados en aplicaciones tecnológicas ha provocado efectos perjudiciales para el ambiente. Carbón activado es usado para eliminar contaminantes, pero es costoso. Se está considerando alternativas de bajo costo derivadas de desechos orgánicos. Se usó esferas (“beads”) de alginato de calcio y borra de café (CA–SCGs) para adsorber metales pesados de soluciones acuosas. Fueron estudiados Cu2 +, Ni2 + y Cd2 +, a concentraciones de 10 ppm a 100 ppm. CASCGs beads estaban hechos de alginato y borra de café. Se compararon con beads de alginato de calcio (“CA beads”) y borra de café (“SCGs”) en capacidad y rapidez de adsorción. Se realizaron tres ciclos de adsorción/desorción para Cd2+ y Ni2+. Los beads se caracterizaron por microscopía electrónica de barrido con espectroscopia de rayos X de dispersión de energía (SEM-EDX), espectroscopia infrarroja con transformada de Fourier (FT-IR), espectroscopia Raman y punto de carga cero. Se utilizaron los modelos Langmuir, Freundlich y Sips, y una ecuación cinética de pseudo-segundo orden. Sips mostró la mejor correlación con la adsorción de CA-SCGs beads con capacidades de adsorción de 91.18 mg/g para cadmio, 42.06 mg/g para cobre y 20.96 mg/g para níquel. La principal ventaja de SCGs y CA-SCG beads frente a CA beads es que los sitios de adsorción de SCGs mostraron una adsorción más rápida y mayores porcentajes de eliminación, especialmente en el rango más bajo de concentraciones (10 ppm a 30 ppm). El intercambio iónico de metales divalentes es el mecanismo de adsorción de CA, pero la adsorción en sitios carboxilo y fenólicos desprotonados puede ser el mecanismo dominante de SCGs. Paracetamol es uno de los productos farmacéuticos más detectados en aguas superficiales. Paracetamol en el ambiente puede tener efectos nocivos. Carbón activado también es un adsorbente efectivo y costoso de paracetamol. Se estudió borra de café con quitosano (Chitosan- SCGs) para remover paracetamol en solución acuosa. Se utilizó la técnica de voltametria cíclica por su buena señal para paracetamol y amplio rango de concentraciones con que puede usarse sin ningún proceso adicional de la muestra. Capacidad de adsorción máxima por el modelo Sips fue de 12.71 mg/g.
Keywords
Removal of heavy metals,
Water pollution,
Spent coffee grounds,
Low-cost adsorbent
Usage Rights
Except where otherwise noted, this item’s license is described as Attribution-NonCommercial 4.0 International
Cite
Torres Cabán, R. J. (2020). Adsorption of pollutants by spent-coffee-grounds composite beads [Dissertation]. Retrieved from https://hdl.handle.net/20.500.11801/2650