Vol.:(0123456789) 1 3 Applied Nanoscience https://doi.org/10.1007/s13204-020-01607-4 ORIGINAL ARTICLE Enhanced photocatalytic reduction of mercuric cations endorsing fabricated mesoporous BiFeO 3 /g‑C 3 N 4 heterojunction under Vis light irradiation Maha Alhaddad 1  · M. H. H. Mahmoud 2,3 Received: 18 September 2020 / Accepted: 23 October 2020 © King Abdulaziz City for Science and Technology 2020 Abstract In this probe, enhanced photocatalytic reduction of mercuric cations has been achieved endorsing a novel mesoporous BiFeO 3 /g-C 3 N 4 heterojunction accommodating various percentages of BiFeO 3 nanoparticles (NPs) under Vis light irradia- tion. Formic acid was adopted as holes sacrifcial correlated with pure g-C 3 N 4 nanosheet or BiFeO 3 nanoparticles. BiFeO 3 NPs of particle dimension of 4–6 nm were homogeneously spread over the surface of the g-C 3 N 4 nanosheet. The superior photocatalytic reduction of mercuric cations endorsing BiFeO 3 /g-C 3 N 4 heterojunction has been afrmed since enlarging the dopant content (BiFeO 3 NPs) from 1 up to 4% brings about an enhancement in the efcacy of the photocatalytic reduc- tion of mercuric cations(Hg) from 38 up to 88% after 1 h of illumination. Obviously, the rate of the photocatalytic removal of mercuric cations endorsing mesoporous BiFeO 3 /g-C 3 N 4 heterojunction accommodating 4% BiFeO 3 NPs was found to be 5.3 and 7.9 times larger when correlated to those of neat BiFeO 3 NPs and g-C 3 N 4 nanosheet, accordingly. The superior photocatalytic reduction of mercuric cations under Vis light irradiation via adopting the synthesized BiFeO 3 /g-C 3 N 4 hetero- junction could be appropriated to the very fnite particle sizes of BiFeO 3 NPs in addition to their excellent dispersion over the g-C 3 N 4 nanosheet surface. Besides, the extensive area, little band gap, and the excellent crystallinity of the synthesized photocatalyst are considered crucial aspects in the photocatalytic achievement of the synthesized BiFeO 3 /g-C 3 N 4 hetero- junction. Interestingly, the stability of the synthesized BiFeO 3 /g-C 3 N 4 heterojunction towards the photocatalytic reduction of mercuric cations has been afrmed via recycling the photocatalyst up to fve runs without pronounced loss in the photo- catalytic performance towards mercuric cations reduction. In conclusion, the attained data brings about establishing a novel photocatalyst of Z-scheme type that could be successfully applied for photocatalytic remediation of toxic contaminants under Vis light irradiation. Keywords Mercuric cations · Photo-reduction · Vis light · Mesoporous · BiFeO 3  · g-C 3 N 4  · Heterojunction Introduction Particular concern has been paid towards wastewater con- taining mercury (Hg) and its derivatives owing to their sig- nifcant toxicity. Hg species could have emerged in many industries like oil-refining fertilizer, bactericides, phar- maceutical, insecticides, chlorine-alkali, fungicides, pet- rochemical, pesticides, herbicides, etc. (Mohamed et al. 2017; Mohamed 2009). Extensive environmental problems are emerged due to Hg derivatives’ existence in the efu- ent systems (Mohamed and Aazam 2013; Mohamed et al. 2012; Mohamed and Abdel Salam 2014; Ismail et al. 2006; Decreto 2003). Numerous regimes to remediate mercu- ric cations from polluted water have been established like adsorption, membrane fltration, electrodeposition, coagula- tion, precipitation as sulfde, and ion exchange (Mohamed 2009). However, the traditional treatment approaches were not sufciently practical, especially for the systems con- taining a smaller mercuric cations concentration. Accord- ingly, novel and practical approaches to treating such low * Maha Alhaddad mahahaddad101@gmail.com 1 Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80200, Jeddah 21589, Saudi Arabia 2 Department of Chemistry, College of Science, Taif University, P.O. Box 11099, Taif 21944, Saudi Arabia 3 Central Metallurgical Research and Development Institute, P.O. Box 87, Helwan, Cairo, Egypt