Novel La(OH)3-integrated sGO-Ag3VO4/Ag nanocomposite as a heterogeneous photocatalyst for fast degradation of agricultural and industrial pollutants

Abstract

La(OH)₃ was integrated with sGO-Ag₃VO₄/Ag photocatalyst in a facile room temperature sonochemical deposition method. 2% (by weight) was found to be the optimal amount of La(OH)₃ for water pollutant degradation. A 20 min sunlight exposure of catalyst-methylene blue solution provided 99.95% degradation of the dye with 6.53 and 2.82 times higher activity than Ag₃VO₄ and sGO-Ag₃VO₄/Ag. Very high mineralization rates of two cationic (98%) and two anionic dyes (96%) were found in 1 h. The novel composite catalysed degradation of 4-chlorophenol and a dithiocarbamate fungicide, thiram, with total organic carbon removal of 78% and 81% in 2–3 h. Degradation products were identified by mass spectroscopy as phenol and thiourea respectively. La(OH)₃ increased and red shifted the absorption and decreased the band gap to generate more charge carriers. Fine distribution of rice-shaped La(OH)₃ over the sGO-Ag₃VO₄/Ag surface remarkably enhanced the carrier transport leading to a reduction in the e⁻–h⁺ recombination, proved by various techniques. Electrons from Ag₃VO₄ and Ag(0) travel through the sGO sheet and reach La(OH)₃ to generate hydroxyl radicals in addition to holes and cause rapid rupture of bonds in pollutants by an advanced oxidation process. The composite was found to be excellent towards real water detoxification with excellent stability, recyclability and photocatalytic activity.