Photocatalytic degradation of 2,4-dichlorophenol using bio-green assisted TiO2-CeO2 nanocomposite system.

In recent times, cost effective synthesis of semiconductor materials has been a subject of concern for the day to today applications. In this work, novelty has been made on the facile synthesis of metal oxides (TiO2 and CeO2) and nanocomposites (TiO2-CeO2) through sol-gel and precipitation methods of imparting lemon extract. The synthesized materials behave as the functional catalysts which has been further carried out for the photocatalytic degradation against 2,4-Dichlorophenol (2,4-DCP). The materials are then valued for the structural and optical properties. The lemon extract used in synthesis has played a premier role in upgrading the charge carrier separation, bandgap, and size reduction of the composite system. Further, the CeO2 supported TiO2 sample acts as the better visible light catalyst, due to the prevention of aggregation and existence of line dislocation that supported to access the additional electron trap sites.

Desenvolvimento e validação de método analítico para análise de 2,4-D, 2,4-DCP e 2,4,5-T para monitoramento em água de abastecimento público / Development and validation of analytical method for analysis of 2,4-D, 2,4-DCP and 2,4,5-T for monitoring of public water supply

RESUMO O ácido 2,4-diclorofenoxiacético (2,4-D) é o segundo herbicida mais consumido no Brasil e seus efeitos na contaminação dos recursos hídricos e consequente risco sanitário para abastecimento público são conhecidos. O 2,4-D e seu principal produto de degradação, o 2,4-diclorofenol (2,4-DCP), apresentam potencial de desregulação endócrina, e o ácido 2,4,5-triclorofenoxiacético (2,4,5-T) é tóxico e persistente no meio ambiente. A inexistência de uma metodologia para quantificação simultânea desses compostos motivou o desenvolvimento e a validação do método de extração e concentração de amostras ambientais e a quantificação em cromatografia líquida de alta eficiência com detector de arranjo de diodos (CLAE-DAD) para análise de 2,4-D, 2,4-DCP e 2,4,5-T em água filtrada produzida em estação de tratamento de água e água de manancial superficial. Os resultados de extração em fase sólida e a concentração da amostra demonstraram recuperação de 89 a 119%, e desvio padrão entre 0,9 e 11,4%. Para os ensaios de identificação e quantificação, os limites de detecção variaram entre 0,17 e 0,51 µg.L-1 e limite de quantificação de 1,0 µg.L-1. Os resultados mostraram que é possível empregar esse método na quantificação do 2,4-D, do 2,4-DCP e do 2,4,5-T em monitoramento ambiental e em sistemas de abastecimento de água atendendo às legislações brasileiras.

ABSTRACT The 2,4-dichlorophenoxyacetic acid (2,4-D) is the second most consumed herbicide in Brazil and their effects in the contamination of the water resources and consequent sanitary risk for public supply are known. The 2,4-D and its main degradation product, 2,4-dichlorophenol (2,4-DCP), have the potential for endocrine disruption and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) is toxic and persistent in the environment. The absence of a methodology that simultaneously determines these compounds led to the development and validation of the solid phase extraction method, environmental samples concentrations, identification and quantification in HPLC-DAD for 2,4-D, 2,4-DCP and 2,4,5-T analysisin filtered water, produced at water treatment plants, and surface water. The extraction essay and samples concentration showed recovery from 85 to 119%, standard deviation between 0.9 and 11.4%. For identification and quantification essays, detection limits ranged between 0.17 and 0.51 µg.L-1 and the quantification limit was 1.0 µg.L-1. The results showed that it is possible to employ this method for the quantification of 2,4-D, 2,4-DCP and 2,4,5-T in environmental monitoring and in water supply systems taking account of Brazilian regulatory agencies

Typha latifolia as potential phytoremediator of 2,4-dichlorophenol: Analysis of tolerance, uptake and possible transformation processes.

2,4-Dichlorophenol (2,4-DCP) is considered a priority pollutant due to its high toxicity. Therefore, it is urgent to develop technologies for the disposal of this pollutant. Various remediation processes have been proposed for the elimination of 2,4-DCP in contaminated water, however, most of them involve high costs of operation and maintenance. This study aimed to determine the capacity of remediation of 2,4-DCP in water by Typha latifolia L. wild plants. For that, the tolerance, removal, accumulation and biotransformation of 2,4-DCP by T. latifolia were investigated. The plants were exposed to 2,4-DCP solutions with a concentration range from 1.5 to 300 mgL-1 for 10 days. They exhibited a reduction in chlorophyll levels and growth rate when 2,4-DCP solutions were ≥30 mgL-1 and ≥50 mgL-1, respectively. The removal of contaminant was dose-depended, being 99.7% at 1.5-3 mgL-1, 59-70% at 10-70 mgL-1 and 35-42% at 100-300 mgL-1 of 2,4-DCP in the solution. Studies indicated that 2,4-DCP was mainly accumulated in root tissue rather than in shoot tissue. Acid hydrolysis of biomass extracts suggests 2,4-DCP bioconjugates formation in root tissue as a response mechanism. Additionally, an increment in glutathione S-transferase (GST) activity could indicate a 2,4-DCP conjugation with glutathione as a detoxification mechanism of T. latifolia.

Biodegradation of 2, 4 dichlorophenol by Pleurotus ostreatus DSM 1833

This work aimed to investigate the capacity of Pleurotus ostreatus DSM 1833 to degrade 2,4-dichlorophenol, important pollutant found in the wastewaters of the paper and cellulose industry. Using a factorial design 2², the concentrations of glucose and 2,4-dichlorophenol varied between 0 and 10g.L-1 and 5 and 30mg.L-1, respectively. The best global biodegradation rate was obtained using 30 mg.L-1 of 2,4- dichlorophenol in the absence of glucose. This culture medium was used for scaling up the process, resulting in a global biodegradation rate of 0.47mg.L-1.h-1. A comparative test between an inoculated medium and an abiotic control demonstrated that 54.1 percent of 2,4- dichlorophenol degradation could be attributed to the presence of P. ostreatus.

A indústria de papel e celulose contribui para a contaminação ambiental devido aos resíduos gerados, especialmente, no processo de branqueamento da polpa Kraft, realizada com cloro. Basideomicetos saprófitas têm a capacidade de degradar compostos organoclorados como cloroligninas e clorofenóis. Este trabalho teve como objetivo investigar a capacidade de Pleurotus ostreatus DSM 1833 em degradar 2,4-diclorofenol, importante poluente encontrado nos efluentes da indústria de papel e celulose. Utilizando um planejamento fatorial 2², as concentrações de glicose e de 2,4-diclorofenol variaram entre 0 e 10 g.L-1 e 5 e 30 mg.L-1, respectivamente. A melhor taxa global de degradação foi obtida usando-se 30 mg.L-1 de 2,4-diclorofenol na ausência de glicose. Este meio de cultura foi utilizado para a ampliação da escala do processo, resultando em uma taxa global de biodegradação de 0,47 mg.L-1.h-1. Um teste comparativo entre o meio inoculado e o controle abiótico demonstrou que 54,1 por cento da degradação do 2,4-diclorofenol pode ser atribuída à presença de Pleurotus ostreatus.