Surface Oxidation Of Copper For CuO Nanowires Formation And Their Catalytic Properties

Cr(VI) is toxic heavy metal which has been classified as human carcinogen. Cr(VI) enters into environment from sources such as textile industries wastewater that contains wax, dyes in colouring and heavy metal suspended solids. This study investigated the applicability of CuO nanowires for removal of Cr(VI) form that aqueous solution. The CuO nanowires were synthesized by direct thermal oxidation of copper coils at temperature between 300 and 600 °C. The CuO nanowires were characterized by Field Emission Scanning Electron Microscope (FESEM) and X-Ray Diffraction (XRD). Oxidation parameters investigated were the effect of oxidation temperature, time and presence of potassium hydroxide as catalyst. Within the temperature range of 400-600°C, the nanowires formed have two different morphologies, straight and curved, with lengths between 4 and 12 µm and diameters between 50 and 240 nm. Different oxidation time at 500 °C was conducted to investigate the growth of nanowires on copper coil. A few nanowires with short length in range of 1-2 µm and diameter of 20-40 nm was formed at 20 minutes of oxidation time. While prolonging of the oxidation time to 135 minutes, the development of nanowires become denser with length 5-7 µm with diameter 130-180 nm. Oxidation of copper in the presence of potassium hydroxide resulted that only a few nanowires with short length can be formed at temperature of 500 °C annealed for 45-135 minute. Then, the sample oxidised at 300 °C and 500 °C were tested to reduce Cr(VI) under sunlight. 75% reduction of Cr(VI) was achieved on oxidised copper coil at 500 °C with nanowires length in range of 3-5 µm