Sensor de Demanda Química de Oxigênio: abordagem verde e de baixo custo baseada em papel funcionalizado com nanopartículas de prata e processamento de imagens

• Autor(a) principal: Nóbrega, Eryka Thamyris Damascena
• Data de Publicação: 2018
• Tipo de documento: Trabalho de conclusão de curso
• Idioma: por
• Título da fonte: Repositório Institucional da UFRN
• Texto Completo: https://repositorio.ufrn.br/handle/123456789/38371
• topic: Demanda química de oxigênio. Nanopartículas de prata. Método colorimétrico. Imagens RGB. Análise de componentes principais

Chemical Oxygen Demand (COD) is a quality parameter of superficial water and wastewater that provides information on chemically degradable fractions of organic (and inorganic) pollutants. Although firmly established, standard method require time for its diagnosis, indiscriminate use of toxic chemical reagents, and a UV-VIS spectrophotometer that is not always available, especially in developing countries. In this report we showed the use of 9,10-epoxy-12-hydroxytetradecanoate (SEAR) with dual role, simultaneously functioned as reducing and stabilizing agents in the synthesis of AgNPs, as well as a study of the nanomaterial behavior against a real raw sewage (COD = 920 mg L-1 ). Energy-Dispersive X-Ray Spectroscopy conducted on AgNPs that reacted with raw sewage revealed the presence of sulfur, confirming that sulfidation took place. The UV-VIS signal change indicates that AgNPs may be an interesting sensor in determining COD. In this sense, we report the development of a paper-based sensor functionalized with AgNPs for the colorimetric detection of COD. The influence of the control factors in the sensors functionalization process was evaluated using a full 23 factorial design. Investigation of sensor use to detect organic pollutant was carried out on samples of real effluents with COD varying from 66 to 1160 mg L-1 . The results revealed that the sensor can be able to detect the presence of organic matter instantly, even without the use of analytical instrumentation. Optical intensity variation of the AgNPs in the sensory layer device, depending on the organic matter content, allows the color variation captured by digital images to be related to COD. Thus, digital image processing was used to extract the channels from the RGB (Red-Green-Blue) color system and the resulting dataset evaluated with Principal Component Analysis. 99.3% of the total variability of the data was explained the first two components, evidencing a differentiation pattern of the sensors in groupings by COD measurement, especially due to variable “channel B”, and indicating that the sensor can be used as a promising alternative tool.