Slag-based Z-scheme heterojunction visible light-driven photocatalyst for efficient degradation of tetracycline antibiotics in water

Photocatalytic degradation of organic pollutants in water has attracted wide attention in recent years. Titanium-bearing blast furnace slag (Ti-BFS), a kind of bulk industrial solid waste, can be synthesized as photocatalytic materials to degrade organic pollutants in water, which helps to absorb waste, save resources and protect the environment. However, this technology has long been limited by the difficulty of visible light driving and low degradation efficiency. Therefore, in this study, a novel Z-scheme heterojunction (CNTL) was synthesized using graphitic phase carbon nitride (g-C 3 N 4 ) modified Ti-BFS, and applied to the photocatalytic degradation of antibiotics in water. The results show that the degradation rate of tetracycline (TC) reached 96.37 % at 60 min under visible light irradiation, the removal rate of TOC reached 46.31 %. g-C 3 N 4 molecules constructed stable 2D/2D heterojunction on TL surface by chemical bonding, and shorten the distance of electron (e − ) transport. At the same time, the abundant defect structures (Ti 3+ and oxygen vacancies) increased the specific surface area (113.05 m 2 /g) and active sites, promoted the separation and transfer of photoinduced e − and hole ( h + ) pairs between interfaces Therefore, the active species increased and the antibacterial properties were enhanced. CNTL was a novel Z-scheme heterojunction, the bandgap was 2.36 eV, the valence band (VB) was 1.93 eV, the conduction band (CB) was −0.43 eV. When excited by visible light, the VB of g-C 3 N 4 acted as a photoinduced e − trap, trapping e − from the CB of TL, reducing the recombination probability of e − on CB of g-C 3 N 4 and h + under VB of TL, it promoted the accumulation of more e − on CB of g-C 3 N 4 , which can react with O 2 on catalyst surface to generate •O 2 − . Meanwhile, VB of TL also gathered more h + with high oxidation potential, and reacted with OH − on the catalyst surface to generate •OH. Thus, CNTL exhibited excellent REDOX capacity and efficiently removed TC from water. This work has enriched the research system of water pollution control and provided support for improving the recycling level of solid waste resources. • Ti-BFS was modified by g-C 3 N 4 to construct a heterojunction photocatalyst (CNTL). • There was nano 2D/2D heterojunction structure in CNTL. • Active sites as Ti 3+ and Ov were distinctly increased. • •O 2 − was the most active species in the TC photodegradation process of CNTL. • The electron transport path belongs to Z-type heterojunction.