Effect of organic matter on cyanide removal by illuminated titanium dioxide or zinc oxide nanoparticles

Abstract

Effect of different type of organic compounds (humic acid, oxalate, ethylenediaminetetraacetic acid, nitrilotriacetic acid, phenol) on the photocatalytic removal of cyanide with TiO2 or ZnO was studied in this work with variation of the solution pH, contact time, initial cyanide concentration and type of organic compounds. Photocatalytic oxidation efficiency of cyanide with TiO2 was greatly affected by the solution pH. It increased as the solution pH decreased. Also maximum removal of cyanide by ZnO was observed near at neutral pH because of the reduced photocatalytic activity of ZnO at exceedingly low and high pH values originated from either acidic/photochemical corrosion of the catalyst and/or surface passivation with Zn(OH)2. Removal efficiency of cyanide greatly decreased in the presence of humic acid, ethylenediaminetetraacetic acid, nitrilotriacetic acid compared to that without presence of organic compound because of the competitive oxidation as well as surface blocking by relatively large organic compounds. The oxidation pattern of cyanide was better described by first-order kinetic model. Finally photocatalytic reaction with TiO2 or ZnO can be effectively applied to treat synthetic wastewater contaminated with cyanide.

Performance enhancement and optimization of photocatalytic cyanide degradation in aqueous solution using Zn (II) and Fe (III) oxides as nanostructure supported on activated carbon

“…Similar results on the effect of individual factors on the cyanide degradation factors have been reported …”

Enhanced destruction of Cu(CN)32− by H2O2 under alkaline conditions in the presence of EDTA/pyrophosphate

“…Similarly, the removal efficiency of cyanide with ZnO photocatalytic oxidation greatly decreased in the presence of organic compounds (e.g. humic acid, oxalate, EDTA, NTA, phenol) due to the competitive oxidation [26]. To the best of our knowledge, the influence of EDTA and pyrophosphate on the H 2 O 2 oxidation of cyanides has not been reported up to date.…”

Photocatalytic Semiconductors

“…Nanoporous crystalline materials of carbon-and sulfur-doped TiO 2 were prepared at room temperature using a sonochemical method (Lee et al 2013). Anionic sulfur doping was demonstrated by XPS.…”

“…It has been postulated that the improved photoactivity of carbon doped TiO 2 materials is a result of the combination of several modifications induced by carbon doping, such as: formation of color centers (including Ti 3+ centers and defects associated with oxygen vacancies that give rise to color centers displaying visible light absorption bands), the introduction of several localized occupied states in the gap, and the higher surface area of the doped materials (Teh and Mohamed 2011). Synthesis of carbon-doped and carbon-co-doped (N, S, F) materials has been conducted via many routes, including simple mixing of a carbon precursor with TiO 2 (Lettmann et al 2001;Lee et al 2013), sol-gel synthesis (Park et al 2009, direct oxidation of Ti metal in a burner flame (Khan et al 2002), hydrothermal synthesis (Dolat et al 2012, and deposition techniques such as MW plasma oxidation, reactive magnetron sputtering, physical vapor deposition (PVD), chemical vapor deposition (CVD) (Dang et al 2012;Hsu et al 2007), and electrophoretic deposition (Macak et al 2007), among others.…”