Efficient catalytic photodegradation of methylene blue from medical lab wastewater using MgO nanoparticles synthesized by direct precipitation method

Abstract

Methylene blue is the main component of several stains such as Wright–Giemsa and Leishman stain that are used in histology and hematology laboratories. 97.8% of methylene blue from medical laboratory wastewater were photodegraded with the aid of MgO nanoparticles as photocatalysts and direct solar irradiation as a renewable source. The rate of photodegradation was 0.0184 min−1. The direct precipitation method was used as a simple and low cost method to synthesize MgO nanoparticles in the size range of 2.5–11.3 nm as estimated from X–ray diffraction peaks. The optical band gap energy was reduced to 4.25 eV. The photoluminescence spectra of MgO nanoparticles show four bands corresponding to F and F+ oxygen vacancy defects. The effects of the operational parameters (MgO dose, initial pH, irradiation source energy, initial concentration of the dye and temperature) were evaluated on the efficiency and rate of the photodegradation. The efficiency of the synthesized MgO nanoparticles was compared with TiO2 and ZnO nanoparticles as well.