Desenvolvimento e avaliação de um sistema de baixo custo para caracterização da eficiência fotocatalítica na degradação de corantes orgânicos

Abstract

Organic dyes present in wastewater can be toxic, hazardous, and potentially carcinogenic. Photodegradation is an effective technique for treating these compounds, as it employs photocatalysts capable of degrading pollutants with high efficiency. In this work, a portable, affordable, and cloud-integrated microphotocatalysis reactor, named MicroPhotoReact (MPR), was developed to characterize the real-time photodegradation of organic dyes. Dye concentration is monitored over time using the Beer–Lambert law, which relates light absorbance to concentration. This approach represents an improvement over traditional methods based on UV–Vis spectrophotometers, which require large solution volumes and multiple replicates for each experimental point, in addition to demanding hours of data collection. The developed system uses an ESP32 microcontroller for data acquisition and cloud transmission, along with control and measurement components such as LEDs, TEMT6000 light sensors, a water pump, and flow sensors. Three dyes commonly used as standards in photocatalysis experiments—Methylene Blue, Rhodamine B, and Bromocresol Green—were tested due to their widespread use in the literature and well-established spectroscopic properties. The objective is to monitor the photodegradation reactions of these compounds using the commercial semiconductor titanium dioxide (TiO₂) as a catalyst. The MicroPhotoReact developed in this study demonstrates performance comparable to commercial systems, offering a low-cost solution with high sensitivity and a high acquisition rate. The constructed prototype is capable of detecting minimum concentrations on the order of 10⁻⁵ mol·L⁻¹, performing rapid measurements at intervals of only 8 seconds per data point, and determining the degradation kinetic coefficient (k) with a resolution of 0.002 min⁻¹. These parameters demonstrate that the proposed system enables real-time, highprecision monitoring of photocatalytic processes.