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Sulfate radical anion activated agro-industrial residues for Cr(VI) adsorption: is this activation process technically and economically feasible?

Author:
Rangel, Aldair Vergel, Becerra, Mariana Guerrero, Guerrero-Amaya, Hernando, Ballesteros, Luz M., Mercado, D. Fabio
Source:
Journal of cleaner production 2021 v.289 pp. 125793
ISSN:
0959-6526
Subject:
activated carbon, adsorbents, adsorption, avocados, behavior, blackberries, chromium, correlation, economic feasibility, electrophoresis, moieties, oxidation, pH, particles, seeds, solids, sulfates, surface area, texture, yields
Abstract:
Three low-cost and abundant agro-industrial residues have been used as hexavalent chromium adsorbents. Blackberry residues and spent ground coffee were the most efficient adsorbents with 10.6 ± 5.9 and 9.7 ± 3.0 mg g⁻¹ maximum adsorption uptake, respectively. With a capacity of 1.4 ± 0.1 mg g⁻¹, avocado seeds showed the lowest adsorption efficiency, all at pH = 5.5. These three solids were treated with a new sulfate radical anion and low temperature-based oxidation process. The particles’ characterization showed no modification in the surface area nor the textural properties but the surface chemistry changes.The electrophoretic mobility, infrared, and energy-dispersive X-ray spectroscopies showed modifications in the surface charge and functional groups due to the oxidation-mediated activation process. Upon activation, not all materials increase their adsorption capacity, and experimental correlations were made to understand this behavior. However, the activated avocado seeds have a maximum adsorption uptake of (31.6 ± 7.4) mg g⁻¹, comparable to activated carbons’ adsorption efficiency. Regardless of the material used, experimental confirmation of the reduction-complexation Cr(VI) adsorption mechanism at pH = 5.5 was made.Finally, the technical-economic parameter ϕ is introduced to facilitate a proposed activation method’s economic feasibility evaluation. Interestingly, raw and activated avocado seeds under some studied scenarios showed similar maximum adsorption uptake values but with different ϕ values of 1.55 and 27.2 g Cr(VI)/USD. Thus, although the processes obtain similar yields, there are dissimilar regarding their economic feasibility.
Agid:
7234453