UV–Vis spectroscopy and desorption/ionization mass spectrometry as the tools for investigation of adsorbed dye photodegradation

Photocatalytic degradation of MB by TiO2: studies on recycle and reuse of photocatalyst and treated water for seed germination

Photocatalysis is an effective way for treatment of wastewater and degradation of dyes. It is important to assess the reusability of photocatalyst and treated water after the treatment process. In this study, the photocatalytic activity of TiO₂ (titanium dioxide) and TiO₂-TMAOH (titanium dioxide-tetramethylammonium hydroxide) was analyzed for degradation of methylene blue dye. Enhanced degradation of methylene blue is observed while treated with TiO₂-TMAOH with photodegradation efficiency (PDE) 80% within 20 min. A further study shows the reusability of TiO₂ for degradation of dye for six cycles with a decrease in photodegradation efficiency from 90% (cycle-1) to 50% (cycle-2). Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDX), and cyclic voltammetry (CV) analysis were carried out to identify the functional groups in treated water, traces of titanium, and TMAOH, respectively. Seed germination of Vigna radiata using TiO₂- and TiO₂-TMAOH-treated water shows equivalent and consistent growth. Water quality analysis of treated water shows improved biochemical oxygen demand (BOD) level (1.5 mg L^-1), which is suitable for reusability of water for many applications. The outcomes suggest treated water can be used for irrigation and plantation purposes.