Photocatalytic Advanced Oxidation Processes for Neutralizing Free Cyanide in Gold Processing Effluents in Arequipa, Southern Peru

David C. Vuono, Johan Vanneste, Linda A. Figueroa, Vincent Hammer, Fredy N. Aguilar-Huaylla, Aaron Malone, Nicole M. Smith, Pablo A. Garcia-Chevesich, Héctor G. Bolaños-Sosa, Francisco D. Alejo-Zapata, Henry G. Polanco-Cornejo and Christopher Bellona
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David C. Vuono: Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, CO 80401, USA
Johan Vanneste: Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, CO 80401, USA
Linda A. Figueroa: Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, CO 80401, USA
Vincent Hammer: Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, CO 80401, USA
Fredy N. Aguilar-Huaylla: School of Metallurgical Engineering, National University of San Augustín, Arequipa 04000, Peru
Aaron Malone: Department of Mining Engineering, Colorado School of Mines, Golden, CO 80401, USA
Nicole M. Smith: Department of Mining Engineering, Colorado School of Mines, Golden, CO 80401, USA
Pablo A. Garcia-Chevesich: Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, CO 80401, USA
Héctor G. Bolaños-Sosa: School of Chemistry, National University of San Augustín, Arequipa 04000, Peru
Francisco D. Alejo-Zapata: School of Process Engineering, National University of San Augustín, Arequipa 04000, Peru
Henry G. Polanco-Cornejo: School of Chemistry, National University of San Augustín, Arequipa 04000, Peru
Christopher Bellona: Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, CO 80401, USA

Sustainability, 2021, vol. 13, issue 17, 1-15

Abstract: Cyanide (CN − ) from gold processing effluents must be removed to protect human health and the environment. Reducing the use of chemical reagents is desirable for small centralized and decentralized facilities. In this work, we aimed to optimize the use of ultraviolet (UV) radiation coupled with hydrogen peroxide (H 2 O 2 ) to enhance the rate and extent of CN − removal in synthetic and actual gold processing effluents, from one centralized and one decentralized facility in southern Peru. Bench-scale studies conducted using H 2 O 2 and ambient UV showed no significant effects on CN − destruction; however, experiments with higher UV intensity and H 2 O 2 accelerated free CN − degradation. When a 1:1 stoichiometric ratio of CN − :H 2 O 2 was tested, the highly concentrated effluent (1 g CN − /L) had a slower pseudo first-order rate constant (k = 0.0066 min −1 ) and took ~5 h longer to reach 99% destruction, compared with the low concentration effluent (100 mg CN − /L; k = 0.0306 min −1 ). Lastly, a TiO 2 photocatalyst with low stoichiometric CN − :H 2 O 2 ratios (1:0.1 and 1:0.2), in a compound parabolic solar concentrator, was tested to investigate the degradation of a high concentration effluent (1.28 g CN − /L). These results show a significant improvement to degradation rate within a 20 min period, advancing treatment options for mineral processing facilities.

Keywords: cyanide; cyanidation; gold mining; advanced oxidation process; photocatalyst; hydrogen peroxide; titanium dioxide; Arequipa; Peru; mining water treatment (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2021
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