Solar Photo-Assisted Degradation of Bipyridinium Herbicides at Circumneutral pH: A Life Cycle Assessment Approach

Processes

Alejandra Teutli-Sequeira¹  JorgeG. Ibanez²  Ruben Vasquez-Medrano²  Dorian Prato-Garcia³ 

[1] Catedras CONACYT, Instituto Interamericano de Tecnología y Ciencias del Agua, Universidad Autónoma del Estado de México, Carretera Toluca-Atlacomulco Km. 14.5 Unidad San Cayetano, Toluca de Lerdo 50200, Mexico;Departamento de Ingeniería Química, Industrial y de Alimentos, Universidad Iberoamericana Ciudad de México, Prolongación Paseo de la Reforma 880, Lomas de Santa Fe 01219, Mexico;Facultad de Ingeniería y Administración, Universidad Nacional de Colombia, Sede Palmira, Carrera 32 No. 12-00, Chapinero, Vía Candelaria, Palmira 76520000, Colombia;

关键词: carbon footprint;    circumneutral pH;    diquat;    ferrioxalate complexes;    life cycle assessment;    paraquat;   

DOI  :  10.3390/pr8091117

来源: DOAJ

【 摘 要 】

This study investigated the degradation of the herbicides diquat (DQ) and paraquat (PQ) by a solar photo-Fenton process that is mediated by Fe(III)-oxalate complexes at circumneutral pH = 6.5 in compound parabolic collectors (CPC)-type reactors. The photo-Fenton process operates efficiently at acidic pH; however, circumneutral operation was key to overcome drawbacks, such as acidification and neutralization steps, reagent costs, and the environmental footprint of chemical auxiliaries. This work revealed a remarkable reduction of total organic carbon for PQ (87%) and DQ (80%) after 300 min (at ca. 875 kJ L⁻¹). Phytotoxicity assays confirmed that the treatment led to a considerable increase in the germination index for DQ (i.e., from 4.7% to 55.8%) and PQ (i.e., from 16.5% to 59.7%) using Cucumis sativus seeds. Importantly, treatment costs (DQ = $8.05 and PQ = $7.72) and the carbon footprint of the process (DQ = 7.37 and PQ = 6.29 kg CO₂-Eqv/m³) were within the ranges that were reported for the treatment of recalcitrant substances at acidic conditions in CPC-type reactors. Life cycle assessment (LCA) evidenced that H₂O₂ and electricity consumption are the variables with the highest environmental impact because they contribute with ca. 70% of the carbon footprint of the process. Under the studied conditions, a further reduction in H₂O₂ use is counterproductive, because it could impact process performance and effluent quality. On the other hand, the main drawback of the process (i.e., energy consumption) can be reduced by using renewable energies. The sensitivity study evidenced that carbon footprint is dependent on the energy share of the local electricity mix; therefore, the use of more renewable electrical energy sources, such as wind-power and photovoltaic, can reduce greenhouse gases emissions of the process an average of 26.4% (DQ = 5.57 and PQ = 4.51 kg CO₂-Eqv/m³) and 78.4% (DQ = 3.72 and PQ = 2.65 kg CO₂-Eqv/m³), respectively. Finally, from the economic and environmental points of view, the experimental results evidenced that photo-assisted treatment at circumneutral pH is an efficient alternative to deal with quaternary bipyridinium compounds.

【 授权许可】

Unknown