RESOURCE RECOVERY FROM WASTEWATER, SOLID WASTE AND WASTE GAS: ENGINEERING AND MANAGEMENT ASPECTS Surfactant-assisted synthesis of copper oxide nanorods for the enhanced photocatalytic degradation of Reactive Black 5 dye in wastewater Martha Purna Chander Rao 1 & Kaviyarasan Kulandaivelu 1 & Vinoth Kumar Ponnusamy 2,3 & Jerry J. Wu 4 & Anandan Sambandam 1 Received: 1 February 2019 /Accepted: 9 May 2019 # Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract In this study, copper oxide nanorods were synthesized via surfactant-assisted chemical precipitation method and characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and UV- Visible spectrometer. XRD result reveals that CuO nanorods were structured in the monoclinic phase. SEM image suggested that synthesized CuO were shaped like nanorod with approximately 20–40 nm width and 500–800 nm length. The observed band gap calculated from UV-Visible absorption studies is 1.45 eV. As-prepared CuO nanorods were applied as a photocatalyst for the degradation of textile dye Reactive Black 5 (RB-5) in aqueous solution under the presence of visible light. The result exhibited that an enhanced degradation of RB-5 was achieved around 98% within 300 min and the experimental values were well matched with the linear fit model (R 2 = 0.97) and the observed rate constant found to be 5 × 10 -3 min -1 . Therefore, as-synthesized CuO nanorods can be applied as a potential photocatalyst material for the degradation of organic pollutants in the wastewater. Keywords Copper oxide . Nanorods . Photocatalyst . Degradation . Reactive Black 5 dye . Wastewater Introduction In recent years, synthesis of one-dimensional (1D) nanostruc- tures has gained tremendous attention owing to their practice in different applications such as supercapacitors, gas sensors, lithium-ion battery electrode materials, catalysis, and photocatalysis (Wang et al. 2011; Bai et al. 2012; Jiang et al. 2012; Zhang et al. 2012; Yang et al. 2018). Many researchers prepared MnO 2 nanorods for electrode material for supercapacitor applications (Aghazadeh et al. 2016; Tehseen et al. 2018; Kamran et al. 2019). Maaza et al. demonstrated the synthesis of rod shape NiO nanostructures by a sol-gel method for optoelectronic applications (Kaviyarasu et al. 2016). Li and his coworkers reported that the Ag 3 PO 4 nanorods shown excellent photocatalytic activities towards the degradation of dyes (Li et al. 2014). Different hazardous organic textile azo dyes were disposed into the rivers, lakes, and oceans leading to the contaminations of water bodies, thereby damaging the aquatic flora and fauna and living system. Reactive Black 5 “RB-5” or Remazol Black 5 is a bis (azo (–N=N–) compound with two aryldiazenyl moi- eties reactive dye (molecular weight, 991.789 g/mol; molecular formula, C 26 H 21 N 5 O 19 S 6 Na 4 ; water solubility, 89 g/L at 293 K) containing two vinyl sulfone groups and aromatic rings, and it is widely employed in textile industry (Wang et al. 2003). RB-5 may cause respiratory difficulties and asthma symptoms and if contact with skin causes an allergic skin reaction (Meric et al., 2003; Dursun et al. 2013). It is a more stable azo dye and highly resistant to biodegradation owing to its complex molecular structure. However, various methods have been widely used Responsible editor: Suresh Pillai * Vinoth Kumar Ponnusamy kumar@kmu.edu.tw * Anandan Sambandam sanand@nitt.edu; sanand99@yahoo.com 1 Nanomaterials and Solar Energy Conversion Lab, Department of Chemistry, National Institute of Technology, Trichy 620015, India 2 Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung 807, Taiwan 3 Research Center for Environmental Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan 4 Department of Environmental Engineering and Science, Feng Chia University, Taichung 407, Taiwan Environmental Science and Pollution Research https://doi.org/10.1007/s11356-019-05434-1