In situ synthesis of g-C3N4/TiO2 heterojunction by a concentrated absorption process for efficient photocatalytic degradation of tetracycline hydrochloride

Abstract

A facile and feasible method was innovatively evolved to in-situ prepare g-C3N4/TiO2 heterojunctions through a high concentration absorption process, to satisfy the exigent requirements of an efficient, low-cost and environmental-friendly photocatalyst for massive antibiotic effluent treatment. This synthesis method was much easier and more rapid than the traditional routes, which can be primarily depicted as follows: the nitrogen precursors were uniformly dispersed on the amorphous hydrolysis product of titanium precursors (titanic acid or metatitanic acid) driven by a concentration gradient, and then, affording the heterostructure of granular TiO2 coupled with lamellar g-C3N4 through a calcination process. The effects of the one-step synthesis on the characteristics of g-C3N4/TiO2 nanocomposites were investigated by XRD, HRTEM, XPS, UV-vis DRS and PL, and the results demonstrated that the nanocomposites exhibited a well-defined micromorphology and enhanced photoabsorption capacity. For the degradation of tetracycline hydrochloride, the g-C3N4/TiO2 heterojunction displayed remarkably elevated photocatalytic activity over bare g-C3N4 and commercial TiO2 under simulated sunlight and visible light. The sample with 4 g of urea content was optimal, with photodegradation efficiencies 3.9 and 2 times higher than those of pure g-C3N4 and TiO2 respectively. Besides, photodegradation pathways based on the role of active species •O2− and •OH were identified by the trapping experiments, indicating that the substantial increase in photocatalytic efficiency can be credited to the construction of direct Z-scheme heterojunctions. This work has provided a novel in-situ synthesis approach to the heterostructure, which would open up new horizons for the rational design and the wide-scale application of high-performance photocatalysts for the photodegradation of antibiotic-based pollutants.