Photophysical effects of TiO2 quantum dots on phytotoxicity, recycling for solar and photocatalytic processes of industrial effluent

[Display omitted] •High purity TQs easily prepared at low calcination temperatures via sol-gel process.•Effective cost for the removal process of 1 Ton of indigo carmine dye in various TQs was evaluated.•Germination and phytotoxicity processes by different TQs samples and TiO2 P25 were studied.•Recycling processes by different TQs samples until 12 and 10 repeat times were studied. Titanium dioxide quantum dots were prepared and studied as a catalyst for studying the photodegradation of indigo carmine dye in aqueous solution and the phytotoxicity of selected seeds. Tomato seeds (Lycopersicon esculentum) germinated in water with different titanium (IV) dioxide quantum dots (TQs) samples (TQ1 and TQ2) and TiO2 P25 did not observe any phytotoxicity influence on the germination process. HRTEM, FE-SEM, EDX, and XRD were used to investigate the size, shape, and structure of the created TQs samples. TQ1 and TQ2 were measured to be exactly 2.6 and 3.4 nm, respectively. The use of these methods has demonstrated and established that TQs do not contain any other phases or contaminants. TQ1 (2.6 nm) and TQ2 (3.4) with highly distinguishable BET-specific surface areas of 474.0 and 298.2 m2/g, respectively, were effectively prepared at different calcination temperatures: 270 and 320 0C for 240 min, respectively, by merely employing the sol–gel technique. The photocatalytic activity of the TQs samples was assessed using a xenon photoreactor for Indigo Carmine dye as a commercial model dye and direct sunlight for actual industrial wastewater samples. They had distinguishable, strong photocatalytic capabilities, which reached 93 to 94 %. Also, their photodegradation rates were still discernible until 12 and 10 repeat times for the photodegradation process in the presence of TQ1 and TQ2, respectively. Also, an investigation of the photocatalytic process of the Indigo Carmine dye has been carried out as a positive influence on the energy consumption ratio (EE/O), which has been done in order to provide price predictions.