# Development of a Low-Cost Microphotoreactor from Recycled Materials: Application to Nb2O5@H2TPP-Catalyzed Methylene Blue Degradation

## TL;DR

Researchers built a low-cost photoreactor from recycled materials and used it to degrade methylene blue using a new catalyst.

## Contribution

A low-cost, DIY photoreactor using recycled materials and a novel Nb2O5@H2TPP photocatalyst for methylene blue degradation.

## Key findings

- Red light showed the highest irradiance and luminous flux compared to blue and green.
- The photoreactor cost US$41.50, much cheaper than commercial alternatives.
- MB degradation was highest under red light (44%) and lowest under white light (32%).

## Abstract

A low-cost, robust, and easy-to-operate photoreactor
with automatic
temperature control, achieved through heat sinks, cooling fans, a
temperature sensor, and a microcontroller (Arduino Nano), was manually
constructed using predominantly discarded materials, without the need
for sophisticated instrumentation. The light source employed was a
3 W RGB LED lamp with infrared (IR) remote control. The electromagnetic
radiation spectra (white, blue, green, and red) were determined by
UV–vis spectroscopy; additionally, the irradiance and luminous
flux of these radiations were evaluated. For luminous flux determination,
a lux meter was developed based on a BH1750-FVI sensor coupled to
the Arduino Nano. The characterizations indicated that red radiation
exhibits the highest irradiance and luminous flux values when compared
to blue and green radiations. The estimated cost for constructing
the photoreactor was US$ 41.50, which is significantly lower than
that of commercially available photoreactors, whose prices typically
exceed US$ 3000.00. To validate the performance of the photoreactor,
the photocatalytic degradation of methylene blue (MB) was carried
out using a novel Nb2O5@H2TPP material
as the photocatalyst. This material was synthesized by physical mixing
of niobium pentoxide (Nb2O5) and 5,10,15,20-tetraphenylporphyrin
(H2TPP). The resulting photocatalyst was comprehensively
characterized by X-ray diffraction, UV–vis diffuse reflectance
spectroscopy (UV–vis/DRS), scanning electron microscopy, zeta
potential measurements, infrared spectroscopy, and thermogravimetric
analysis. The MB degradation reactions were initially conducted following
a factorial experimental design. This analysis identified MB concentration
as a negative factor in the degradation percentage, catalyst mass
as a positive factor, and reaction time as a nonsignificant variable
within the time range explored. Based on these findings, MB degradation
reactions were performed under different ranges of incident light
wavelengths (white, blue, green, and red). The MB degradation percentages
observed were 32% under white light, 34% under blue light, 42% under
green light, and 44% under red light exposure.