1842 ISSN 1229-9197 (print version) ISSN 1875-0052 (electronic version) Fibers and Polymers 2016, Vol.17, No.11, 1842-1848 Copper Oxide-Carbon Nanotube (CuO/CNT) Nanocomposite: Synthesis and Photocatalytic Dye Degradation from Colored Textile Wastewater Niyaz Mohammad Mahmoodi*, Pardis Rezaei 1 , Cyrus Ghotbei 1 , and Mohammad Kazemeini 1 Department of Environmental Research, Institute for Color Science and Technology, Tehran 1668814811, Iran 1 Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran 11365-11155, Iran (Received June 18, 2016; Revised September 5, 2016; Accepted September 7, 2016) Abstract: In this paper, CuO/CNT nanocomposite was synthesized and its photocatalytic dye degradation ability for colored textile wastewater was studied. The characteristics of the nanocomposite were investigated by XRD, SEM and FTIR. The photodegradation of Direct Red 31 (DR31) and Reactive Red 120 (RR120) by CuO/CNT in presence of H O was investigated. Photocatalytic dye degradation was determined by UV-vis spectrophotometer. Effects of catalyst dosage, initial dye concentration and salt on photodegradation performance were studied. The photocatalytic dye degradation ability of pure CuO and CuO/CNT nanocomposite is 78 % and 89 % for DR31 and 70 % and 87 % for RR120, respectively. The results showed that CNT increased the photocatalytic activity of CuO. The presence of salt decreases dye degradation efficiency. The dye degradation kinetics by nanocomposite followed first-order kinetic model. The reaction rate at 0.005 g catalyst was 0.0137 and 0.0105 min for DR31 and RR120, respectively. It was found that the CuO/CNT nanocomposite as a photocatalyst could be used to degrade dyes from colored wastewater. Keywords: Copper oxide-carbon nanotube nanocomposite, Synthesis, Colored textile wastewater, Photocatalytic dye degradation Introduction About 50-70 % of available dyes are azo compounds which have one or more azo bond (-N=N-) in their structure. A large amount of these dyes (1-20 % of total dye production) flow to environment through wastewater of textile factories and disturb the ecosystem and endanger human health. It has been shown that some of azo dyes are toxic and carcinogenic compounds. Azo dyes are complex and stable compounds and large degree of aromatics exist in their molecular structure. Furthermore, dyes get involve in some undesirable reactions such as oxidation and hydrolysis in the wastewater and produce byproducts more dangerous than themselves [1-6]. Several materials were used to remove pollutants from water. Some materials were used as adsorbents [7-16]. In addition various materials were used as catalysts to degrade pollutants [17-28]. Traditional treatment processes such as biological methods are not able to degrade them. Moreover, stringency of international environmental standards has forced industries to develop the effective methods of wastewater treatment. Therefore, environmental scientists have turned to advanced oxidation processes (AOPs) which use strong oxidants like hydroxyl radical to destruct the organic pollutants such as azo dyes. Photocatalytic degradation process as an AOP is a clean and green Technology and one of the best promising methods because of its perfect mineralization ability of pollutants, low energy consumption and lack of creating the secondary pollutant [1-6,29]. Lately, metal oxide nanoparticles have been used widely in photodegradation of organic pollutant. Copper oxide (CuO) is a p-type semiconductor with interesting characteristics like low cost, direct bond gap (1.2-1.5 eV), photochemical stability, numerous sources, ease of synthesis, non-toxicity and eco-friendly. CuO has been reported as an active photocatalyst in many references. But there are negative aspects with CuO, for example, thin band gap causes (electron and hole come back to each other very quickly) to recombination of photogenerated electron- hole pairs. Hence this defect must be eliminate to improve the photocatalytic efficiency of CuO [4,6,30]. Carbon materials because of their features such as photostability, low cost and eco-friendly, can be used as a suitable co-catalyst to remove the drawbacks of CuO. Among carbon base materials, carbon nanotubes (CNT) due to the exclusivities as morphological, structural and electrical properties, such as ordered structure with a high aspect ratio, large ratio of surface area to mass, ultralight weight, high thermal conductivity, metallic or semi-metallic behavior, high electrical conductivity and remarkable mechanical strength, has got particular importance. CNT can amend the photocatalytic activity of metal oxides in several ways. CNT increase the rate of emigration of photogenerated electrons and in this way, distance the electrons and holes. Also, absorbing of light can induce electrons in CNT and thus enhance the electrons participating in the reactions [2,31]. A literature review shows that photocatalytic dye degradation using CuO/CNT nanophotocatalyst in presence of hydrogen peroxide has not been reported in details. In this work CuO/CNT nanocomposite was synthesized and used as a photocatalyst. The features of CuO/CNT were surveyed by using FTIR, XRD and SEM. Photocatalytic efficiency of CuO/CNT nanocomposite was investigated by degradation *Corresponding author: mahmoodi@icrc.ac.ir DOI 10.1007/s12221-016-6645-y