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Adsorption Characteristics of Spent Coffee Grounds as an Alternative Adsorbent for Cadmium in Solution

by Min-Suk Kim 1 and Jeong-Gyu Kim 1,2,*
1
O-Jeong Eco-Resilience Institute, Korea University, Seoul 02841, Korea
2
Division of Environmental Science and Ecological Engineering, College of Life Science and Biotechnology, Korea University, Seoul 02841, Korea
*
Author to whom correspondence should be addressed.
Environments 2020, 7(4), 24; https://doi.org/10.3390/environments7040024
Received: 11 March 2020 / Revised: 25 March 2020 / Accepted: 26 March 2020 / Published: 27 March 2020
The present study was conducted to ascertain the potential of spent coffee grounds (SCGs) as an alternative adsorbent for the removal of cadmium (Cd) from aqueous solutions. Therefore, Cd adsorption batch tests, using SCGs that had not undergone any chemical pretreatment, were conducted using Cd solutions with a wide concentration range (i.e., 0.1–120 mM) under various adsorption conditions, e.g., ion strength, pH, and solid/solution ratio. For comparison, zeolite, as a well-known common representative adsorbent, was included to determine the adsorption efficiency. The adsorption capacity of the SCGs increased with the decreasing ionic strength of the test solution from 200 to 0 mM of Ca(NO3)2 and the increasing solid:solution ratio from 1:4 to 1:400. The most significant factor influencing the adsorption capacity of the SCGs was the pH of the test solution, with increases in the adsorption capacity as the initial solution pH was increased from 2 to 10. However, the rate for Cd removal remained constant, at 71.19%, when the initial solution pH was between 4 and 8 due to the buffer capacity of SCGs. The obtained data were fitted with the Freundlich, Langmuir, and Dubinin-Radushkevich isotherm models. The Langmuir isotherm provided the best correlation for Cd adsorption onto SCGs (R2 = 0.96) and zeolite (R2 = 0.92), and the maximum Cd adsorption capacity of the SCGs was 19.32 mg g-1, which was higher than that of zeolite (13.91 mg g−1). These results mean that the SCGs can be utilized as alternative low-cost biosorbents to replace conventional adsorption materials. View Full-Text
Keywords: adsorption isotherm; biosorption; coffee grounds; organic residue; zeolite adsorption isotherm; biosorption; coffee grounds; organic residue; zeolite
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Kim, M.-S.; Kim, J.-G. Adsorption Characteristics of Spent Coffee Grounds as an Alternative Adsorbent for Cadmium in Solution. Environments 2020, 7, 24.

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