Constructing Z-scheme LaTiO₂N/g-C₃N₄@Fe₃O₄ magnetic nano heterojunctions with promoted charge separation for visible and solar removal of indomethacin

Pharmaceutical effluents in water bodies pose hazards to the ecosystem because of their potent biological toxicity. Focusing on the removal of such toxic complicated pharmaceutical residues, an innovative LaTiO₂N/g-C₃N₄@Fe₃O₄ heterojunction photocatalyst was assembled by a simplistic route for visible and solar light degradation of anti-inflammatory drug indomethacin (IDM). The LCF-20 catalyst (with LaTiO₂N:g-C₃N₄ -0.2:1) shows excellent performance for visible light photodegradation of IDM, as evidenced by 97.3 % removal in just 45 min exposure which is about 13 times faster than bare g-C₃N₄. 83.4 % of total organic carbon removal was achieved by LVF-20 under visible light. Also, with natural sunlight, nearly 80 % of IDM was removed in 90 min irradiation. The heterojunction's extensive intimate interfacial interactions amid LaTiO₂N and g-C₃N₄ reduce the shortcomings of the two for a better photo-activity. The high visible activity, diminished recombination, high charge transfer is attributed to effective Z-scheme transfer facilitated by Fe₃O₄ nanoparticles. Scavenging experiments prove the importance of superoxide radicals as the dominant species responsible for photodegradation reaction. By mass spectrometry and total organic carbon analysis, a reaction mechanism was also reasonably proposed. The photocatalytic mechanism was discussed in light of conventional and Z-scheme transfer for better insight. The catalyst is stable, recyclable and magnetically separable. This investigation offers a new perspective in the rational design and manufacture of organic-inorganic nitrides based magnetically recoverable heterojunctions as LaTiO₂N/g-C₃N₄@Fe₃O₄. Such heterojunctions present a new class of robust hierarchical photocatalytic materials which are capable of remediation of pharmaceutical residues under practical conditions.