-The solar driven photo-Fenton process for treating water containing phenol as a contaminant has been evaluated by means of pilot-scale experiments with a parabolic trough solar reactor (PTR). The effects of Fe(II) (0.04-1.0 mmol L -1 ), H 2 O 2 (7-270 mmol L -1 ), initial phenol concentration (100 and 500 mg C L -1 ), solar radiation, and operation mode (batch and fed-batch) on the process efficiency were investigated. More than 90% of the dissolved organic carbon (DOC) was removed within 3 hours of irradiation or less, a performance equivalent to that of artificially-irradiated reactors, indicating that solar light can be used either as an effective complementary or as an alternative source of photons for the photo-Fenton degradation process. A non-linear multivariable model based on a neural network was fit to the experimental results of batch-mode experiments in order to evaluate the relative importance of the process variables considered on the DOC removal over the reaction time. This included solar radiation, which is not a controlled variable. The observed behavior of the system in batch-mode was compared with fed-batch experiments carried out under similar conditions. The main contribution of the study consists of the results from experiments under different conditions and the discussion of the system behavior. Both constitute important information for the design and scale-up of solar radiation-based photodegradation processes.
Solar reactors can be attractive in photodegradation processes due to lower electrical energy demand. The performance of a solar reactor for two flow configurations, i.e., plug flow and mixed flow, is compared based on experimental results with a pilot‐scale solar reactor. Aqueous solutions of phenol were used as a model for industrial wastewater containing organic contaminants. Batch experiments were carried out under clear sky, resulting in removal rates in the range of 96–100 %. The dissolved organic carbon removal rate was simulated by an empirical model based on neural networks, which was adjusted to the experimental data, resulting in a correlation coefficient of 0.9856. This approach enabled to estimate effects of process variables which could not be evaluated from the experiments. Simulations with different reactor configurations indicated relevant aspects for the design of solar reactors.
Soluble bio-organic substances (SBO) obtained from urban bio-wastes have been investigated as chemical auxiliaries in photochemical processes. For this purpose, photodegradation of the antibiotic sulfadiazine (SDZ) (25 mg L-1) was studied under simulated sunlight. Experiments were performed to check the role of the SBO as additives for the photo-Fenton process ([SBO] 0 = 20 mg L-1 , [H 2 O 2 ] 0 = 244 mg L-1 , [Fe 3+ ] 0 = 5 mg L-1) at pH 3, 5.2 and 7. The results show that in slightly acidic conditions (pH = 5.2) the SBO improve the photo-Fenton process. Organic compounds present in the SBO are able to complex iron cations and hence, iron precipitation could be avoided. Finally, the results of a Doehlert uniform array design were used to fit a neural network model, which was found to be an effective, simple approach to successfully modeling the photo-Fenton degradation using SBO within the range of experimental conditions. This model might be useful in process optimization.
RESUMO -O chorume gerado a partir da lixiviação do lixo descartado em aterros sanitários pode causar grandes danos ambientais por contaminação de solos e águas subterrâneas e superficiais. Devido à variedade de materiais dispensados nos aterros, o lixiviado gerado tem grande variabilidade química contendo compostos químicos complexos e de difícil degradação. Nesta direção os Processos Oxidativos Avançados surgem como possibilidade de tratamento do lixiviado, com a mineralização da matéria orgânica presente no mesmo. Neste trabalho foram verificadas as condições de mineralização via processo Foto-Fenton com o uso do complexo FeIII-oxalato, que evita o processo de coagulação da matéria orgânica e promove a mineralização real e não apenas mudança de fase. O lixiviado utilizado pertence ao Aterro Bandeirantes (SP) que é considerado maduro (metanogênico). Foram variadas as concentrações de H 2 O 2 e do complexo, alcançando-se mineralização de até 70 % em 120 minutos em pH 3 e mineralização de apenas 20 % em pH 6.
INTRODUÇÃOO aterro sanitário é o método mais simples e barato de disposição de resíduos sólidos utilizados em todo o mundo. Apesar dos aterros sanitários serem considerados uma solução segura para a destinação de resíduos, esta técnica gera rejeitos que causam impactos ambientais significativos como por exemplo a geração do chorume, que necessita ser drenado, coletado, conduzido e tratado de forma correta para que não seja disposto no meio ambiente trazendo prejuízo ao solo e às águas subterrâneas e superficiais. O chorume contém grandes quantidades de compostos orgânicos -como os ácidos húmicos -amônia, metais pesados, uma variedade de materiais complexos e muitos outros produtos químicos perigosos. A composição e concentração dos componentes de cada chorume podem variar dependendo do tipo de resíduo depositado, da origem e composição dos resíduos, do clima, da estação do ano, bem como da estrutura e idade do aterro (Lange, Amaral, 2009).A idade do aterro é um dos fatores mais importantes que afetam as características do chorume bem como a eficiência de seu tratamento. Aterros velhos (> 10 anos) produzem chorumes maduros com características estáveis e são também chamados de "estabilizados", sendo relativamente menos biodegradáveis (relação DBO 5 /COT < 0,1) e contendo baixa concentração de COT (carbono orgânico total) em comparação com chorumes novos (Amr et al., 2013).
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