Enhanced adsorption and photocatalytic activities of ultrathin graphitic carbon nitride nanosheets: Kinetics and mechanism

Different from most composite structures with a common configuration of adsorbent-catalyst, g-C3N4 thin nanosheets (CNNS) with the thickness of 8-11 nm had more efficient and stable adsorption and photocatalytic activities in the removal of tetracycline (TC) from aqueous solution. In comparison with common g-C3N4 counterparts, the adsorption performance of CNNS increased by at least 10.3 times and that for photocatalytic efficiency increased for more than 4.8 times. The large contact area and delocalized pi bonds provided by CNNS resulted in the enhanced TC adsorption capacity. The efficient separation and prolonged-lifetimes of photo-generated charge carriers, and the strong adsorption brought about a reinforced photocatalytic activity for TC degradation. The adsorption of TC onto CNNS was well followed the pseudo-second-order adsorption kinetics, and the obtained adsorption isotherm was well fitted to the Langmuir isotherm model. Due to the efficient adsorption and photocatalysis of CNNS, the zero-order and first-order kinetics models were presented during the different reaction time for TC photodegradation, the h(+), center dot O-2(-) and center dot OH radicals were confirmed as the major reactive oxidative species, and the degradation products were determined. This study provided a new route for the development of catalysts with efficient adsorption and photocatalytic activity in the purification of organic wastewaters.