Photocatalytic reduction of Cr(VI) and Ni(II) in aqueous solution by synthesized nanoparticle ZnO under ultraviolet light irradiation: a kinetic study

Abstract

Photocatalytic removal of Cr(VI) and Ni(II) from aqueous solution using synthesized nanoparticle ZnO under ultraviolet (UV) light irradiation was studied in this work. Firstly, nanoparticle ZnO was prepared by the chemical method with an organic chemical inhibitor. Then removal efficiency of Cr(VI) and Ni(II) by nanoparticle ZnO was investigated with variation of the solution pH, ZnO dosage, contact time and initial Cr(VI) and Ni(II) concentration. Maximum removal of Cr(VI) and Ni(II) was observed at near-neutral pH because the reduced photocatalytic activity of ZnO at exceedingly low and high pH values originates from either acidic/photochemical corrosion of the catalyst and/or surface passivation with Zn(OH)2. As the ZnO dosage increased, the removal efficiency of Cr(VI) and Ni(II) was continuously enhanced, but was gradually decreased above 1.25 g/l due to the increased blockage of the incident UV light used for the photocatalytic reaction. The optimum ZnO dosage was determined as 1 g/l. Removal efficiencies of Cr(VI) and Ni(II) decreased as initial Cr(VI) and Ni(II) concentration increased, due to an increased inhibition effect on the surface of ZnO resulting from the decreased reaction sites on the surface of ZnO required for the further photocatalytic reaction.

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

“…HA, oxalate, EDTA, NTA and phenol were used as organic matter. TiO 2 and ZnO dosage equal to 1 g/L was used for all experiments because this dosage was identified as an optimum dosage from our previous paper [2,17]. The initial solution pH was adjusted by adding 0.1 M NaOH and HCl.…”

“…The most important properties of ZnO are non-toxic in itself, providing attractive photocatalytic efficiency [16]. Photocatalytic reaction using ZnO/UV can simultaneously treat organic compounds and metallic elements in addition to change non-biodegradable to biodegradable organic compounds [17,18]. ZnO is used as an effective, inexpensive and nontoxic photocatalyst for the degradation of synthetic dyes, oxidation cyanide and reduction of Cr(VI) [17,19,20].…”

ZnO-PLLA Nanofiber Nanocomposite for Continuous Flow Mode Purification of Water from Cr(VI)

“…Also, in the alkaline regime, the surface charge of ZnO is negative. Metal recovery and reuse of the adsorbent can become economically viable in the overall process [ 44 ].…”

Application of Semiconductor Photocatalytic Materials for the Removal of Inorganic Compounds from Wastewater

“…Both the activity and stability of ZnO could be affected by changing its morphology (Guo et al 2011). Thus, ZnO synthesized by precipitation (Liu et al 2012a) (Qamar et al 2011;Siboni et al 2011a) has been evaluated for Cr (VI) removal. The prepared catalysts of nanometer size were evaluated at neutral or slightly alkaline pH values using an aqueous ZnO suspension and applying UV light as the irradiation source.…”