Synthesis of Diatomite/g-C$lt;inf$gt;3$lt;/inf$gt;N$lt;inf$gt;4$lt;/inf$gt; Composite with Enhanced Visible-light-responsive Photocatalytic Activity

Novel visible-light-responsive diatomite/g-C 3 N 4 composite was successfully synthesized via a facile impregnation-calcination method.The sample was characterized by TG, XRD, FE-SEM, HR-TEM, FT-IR, XPS, UV-Vis-DRS, and PL spectra.The photocatalytic activities of samples were evaluated by degradation of RhB under visible light irradiation.Experimental results indicated that 2.32wt% diatomite/g-C 3 N 4 composite exhibits high efficiency for the degradation of RhB.The photoreaction kinetics constant value is about 1.9 times as high as that of g-C 3 N 4 under visible light irradiation.The radical trap experiments indicate that •O 2 -serves as the main active species for the photodegradation of RhB over 2.32wt% diatomite/g-C 3 N 4 under visible light irradiation.The enhanced photoactivity is mainly attributed to the electrostatic interaction between g-C 3 N 4 and negatively charged diatomite, synergistic effect lead to the efficient migration of the photogenerated electrons and holes of g-C 3 N 4 .Key words: diatomite/g-C 3 N 4 composite; impregnation-calcination method; visible-light-irradiation; electrostatic interactionUp to now, it is still a difficult problem to treat dyes wastewater due to its high stability and complicated compositions.The conventional treatment methods, such as absorption, ultrafiltration, reverse osmosis, coagulation, etc. are ineffective for its decolorization and mineralization [1] .In order to cope with the growing environmental problems, new efficient environment purification technologies have been developed, such as advanced oxidation processes [2] .Photocatalytic technology is an efficient means which is applicable on completely degrading organic pollutants in waste water but very challenging process to convert solar energy into chemical energy [3] .So, it is urgent and indispensable to utilize sunlight efficiently, development of more efficient, sustainable, visible-lightresponsive photocatalytic materials.Recently, graphitic carbon nitride (g-C 3 N 4 ) which is a metal-free polymeric photocatalyst, have attracted extensive attention because of its good photocatalytic performance for hydrogen or oxygen production via water splitting under visible light irradiation [4] .In general, the preparation of g-C 3 N 4 obtained by heating low-cost melamine was investigated by Zou's group [5] .The metal free g-C 3 N 4 photocatalyst possesses very high thermal, optical, chemical