Preparation of Nanofibrous Membranes Containing Carbon Dots Composited With TiO₂ Photocatalyst and Their Removal Rate of Methylene Blue Under Visible Light

As the industrialization is improving by way of science and technology in society, water pollution has become increasingly serious. Non-degradable organic matter exists in wastewater, which causes environmental deterioration. In order to solve this problem, we select titanium dioxide (TiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>) as the photocatalyst material with high activity, chemical stability and low cost. However, pure TiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> has a large band gap (3.2 eV) and can only be activated under ultraviolet (UV) light. Therefore, TiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> has to be modified to fit our requirement. Carbon dots (CDs) have up-conversion and down-conversion photoluminescence and inhibit the recombination of electron-hole pairs, Adding CDs can reduce the band gap width of TiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>, and increase the absorption of visible light significantly, thereby improving photocatalytic efficiency. We use citric acid as the carbon source and urea as the nitrogen source to prepare CDs by using the hydrothermal method, and prepare the CDs/TiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> composite photocatalyst through the sol-gel method. The CDs/TiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> composite photocatalyst shows stable and efficient photocatalytic performance for removal of methylene blue (MB), with a removal rate of 95.34%. In order to reuse the CDs/TiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> composite photocatalyst powder, we use electrospinning technology to combine CDs/TiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> composite photocatalyst with nylon 6,6 nanofibrous membranes. After three cycle tests, we confirm that it is recyclable and practical, and its removal rate is also increased to 99.39%.