Study On The Synthesis Of Modyfied G-C₃N₄ And Its Photocatalytic Reduction Of Cr（Ⅵ）

Cr（Ⅵ） pollution is a serious environment problem in China, it’s of great importance to developing photocatalysts for Cr（Ⅵ） reduction. However, most of the photocatalysts for Cr（Ⅵ） reduction contain heavy metal and can not be excited by visible light. So developing a photocatalyst which contains no heavy metal and can be excited by visible light is necessary. g-C₃N₄ is a new photocatalytic material which contains no heavy matals and can be excited under visible light. However some drawbacks appear, such as the easy recombination of photogenerated holes and electrons, low ultization of visible light. The work of this paper was focused on the modification of g-C₃N₄ by iron oxides, the effects of pesticide and humic acid on Cr（Ⅵ） reduction were also studied. The main research contents and conclusions as follows:1) α-Fe₂O₃/g-C₃N₄ was synthesized by hydrothermal method, the best content of α-Fe₂O₃ was confirmed and α-Fe₂O₃/g-C₃N₄ heterojunction was successfully fabricated. The heterojunction could facilitate the separation of photogenerated electrons and holes, promote the photocatalytic activity. The Cr（Ⅵ） reduction ability of α-Fe₂O₃/g-C₃N₄ was almost 2.4 times higher than g-C₃N₄. The effects of pH and hole scavenger were also studied. The reduction rate of Cr（Ⅵ） decreased with the increase of pH and the hole scavenger could facilitate Cr（Ⅵ） reduction.2) α-Fe₃O₄/g-C₃N₄/C was synthesized with the existence of glucose, the glucose not only acted as surfactant, it could transform to hydrothermal carbon, hydrothermal carbon could facilitate the transfer of electrons and promote the photocatalytic activity. α-Fe₃O₄/g-C₃N₄/C showed well Cr（Ⅵ） reduction and dimethoate degradation ability. The coexistence of Cr（Ⅵ） and dimethoate could facilitate the reduction and degradation of each other.3) The reduction of Cr（Ⅵ） by humic acid/g-C₃N₄ system was studied, g-C₃N₄ performed normal Cr（Ⅵ） reduction ability, however after the introduction of humic acid the reduction rate of Cr（Ⅵ） was greatly promoted and the reduction rate increased with the increase of humic acid. The best content of humic acid was 80 mg/L. Humic acid/g-C₃N₄ system showed better Cr（Ⅵ） reduction ability in acid condition than neutral and alkaline condition.