Sunlight mediated degradation of spent wash using hydrothermally synthesized orthorhombic shaped Cu–TiO2 nanoparticles

Abstract

Degradation of spent wash waste is a very essential but challenging task in the indian sugarcane distillery industry because of its awfully acidic pH, and intense brown colour with a strong unpleasant odour. Prior to discharge in the environment, its degradation using an efficient and cost effective method is important. A photo-catalytic degradation route could be a simple, cost effective alternative to conventional degradation processes. Cu-doped TiO₂ was synthesised using a facile sol gel assisted hydrothermal method at various temperatures such as 120, 150 and 180 °C. Cu–TiO₂ with doping concentrations of 0.5 to 5% were synthesized using the hydrothermal method. The physico-chemical properties of the synthesised Cu–TiO₂ were investigated by using various characterization techniques. UV-visible analysis shows a red shift in the absorption wavelength in the case of Cu–TiO₂ as compared with bare TiO₂. Structural and morphological analysis confirms the formation of anatase TiO₂ with a nano-orthorhomb like morphology. The photocatalytic performance of the TiO₂ and Cu doped TiO₂ samples was evaluated for degradation of spent wash colour under natural solar light irradiation. Among all the Cu–TiO₂ samples, 1% Cu–TiO₂ synthesized at 150 °C exhibited the maximum degradation efficiency with almost 59% degradation of the spent wash in 5 h. The molecular weight of the colour compounds after degradation was monitored using gel permeation chromatography (GPC). The GPC fractions show low, medium, and high molecular weight coloured compounds with a strong hypsochromic shift. Identification of the compounds in each of the GPC fractions was studied using liquid chromatography mass spectrometry quadrupole time of flight (LC-MS Q-TOF).