Characteristics and mechanism of uranium photocatalytic removal enhanced by chelating hole scavenger citric acid in a TiO2 suspension system

Liu, Mingxue; Luo, Lei; Dong, Faqin; Wei, Hongfu; Nie, Xiaoqin; Zhang, Wei; Hu, Wenyuan; Ding, Congcong; Wang, Pingping

doi:10.1007/s10967-018-6237-y

Cited by 17 publications

(7 citation statements)

References 48 publications

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“…Anatase (TiO 2 ) has attracted a lot of attention because of its low cost, non-toxic and good photocatalytic performance, which can be used as a model mineral [26,27]. It is widely used in the degradation of organic pollutants [28], heavy metals [29], dye-sensitized solar cells [26], biomedical fields [27]. However, anatase (TiO 2 ) particles have defects such as low utilization of visible light and easy recombination of photogenerated electrons and holes [30].…”

Section: Introductionmentioning

confidence: 99%

Adsorption and Mechanism of Glycine on the Anatase with Exposed (001) and (101) Facets

et al. 2022

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As a widely existing mineral types on Earth, semiconductor minerals play an important role in the origin of life and the material geochemical cycle. The first step of peptide formation is amino acid adsorption on the mineral surface, but the role and mechanism of different crystal facets of semiconductor minerals are not well understood. Anatase (TiO2) with exposed (001) facets was synthesized by a hydrothermal method, and then analyzed and compared with the purchased ordinary anatase (TiO2) for the adsorption of glycine, the simplest amino acid. XRD, SEM and TEM results show that the hydrothermally synthesized anatase (TiO2) has a good anatase crystal form, which is micro-nano-scale flake particles and mainly composed of (001) facets. The results of HPLC used in the adsorption experiment showed that under optimal conditions (pH 5 to 6, an adsorption time of 24 h, and an initial concentration of 0.09 mol/L), the adsorption quantity of glycine on anatase (TiO2) with exposed (001) facets may reach 10 mg/m2, which is larger than that for ordinary anatase (TiO2) with exposed (101) facets. Based on a combination of various characterizations and simulation calculations, the results proved that anatase can activate thermodynamically stable γ-glycine to β-glycine. The adsorption of glycine on anatase (TiO2) has two forms, one is the zwitterionic form in which the carboxyl group forms a bridge structure with two Ti atoms connected by surface bridging oxygen, and the dissociated form is in which the amino group forms a bond with the surface Ti atom. Among these, glycine is mainly adsorbed to anatase by dissociative molecules on the anatase (TiO2) with exposed (001) facets and by zwitterion adsorption on the anatase (TiO2) with exposed (101) facets. This research elucidates the conditions and mechanism of amino acid adsorption by semiconductor minerals in weak acidic environment, which is similar to the environmental pH that was beneficial to the formation of life on the early Earth. Therefore, these can provide a reference for the further study of the role of semiconductor minerals in the adsorption and polymerization of small biomolecules in the origin of life.

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Section: Introductionmentioning

confidence: 99%

Adsorption and Mechanism of Glycine on the Anatase with Exposed (001) and (101) Facets

et al. 2022

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“…Kabra et al studied the solar photocatalysis and adsorption of lead (Pb) and reported 22.4 and 43% dark adsorption of lead ions on the catalyst surface with and without using citric acid as a hole scavenger, respectively. Previous studies have shown that the efficiency of metal removal can be improved in the aqueous phase using hole scavengers, so citric acid was used as a hole scavenger for photocatalytic reduction of lead ions (Pb 2+ ) . The lead solution having a concentration of 100 mg L –1 was then irradiated under UV light with 2 g L –1 TiO 2 catalyst at pH 5.3 for 180 min, and Pb 2+ reduction was observed to be 79.6%.…”

Section: Resultsmentioning

confidence: 99%

“…Previous studies have shown that the efficiency of metal removal can be improved in the aqueous phase using hole scavengers, so citric acid was used as a hole scavenger for photocatalytic reduction of lead ions (Pb 2+ ). 33 The lead solution having a concentration of 100 mg L −1 was then irradiated under UV light with 2 g L −1 TiO 2 catalyst at pH 5.3 for 180 min, and Pb 2+ reduction was observed to be 79.6%. The effect of different parameters on the Pb 2+ removal under UV light (35 W m −2 ) was then studied.…”

Section: Resultsmentioning

confidence: 99%

Photocatalytic Reduction and Crystallization Hybrid System for Removal and Recovery of Lead (Pb)

Kumar

Wanchoo

Toor

2021

Ind. Eng. Chem. Res.

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The heavy metal lead (Pb) is toxic to humans, animals, and plants and shows persistence and is nondegradable in aquatic media. A novel method has been proposed using photocatalysis (PC) and reduction crystallization (RC) for efficient removal and recovery of lead (Pb) from the aqueous phase. Using photocatalysis, maximum removal of lead ions (Pb 2+ ) was 79.6% under optimized conditions (2 g L −1 TiO 2 , pH 5.3, and 35 W cm −2 UV light intensity). However, reduction crystallization removed 90% lead ions (Pb 2+ ) using hydrazine hydrate as a reduction agent with optimized parameters (pH 10 and temp 80 °C). To achieve maximum removal as well as recovery of toxic lead, both methods, photocatalysis and reduction crystallization, were combined, removing 98.2% of lead ions (Pb 2+ ) from the aqueous phase. The recovered precipitates and photocatalysts (TiO 2 ) were analyzed using scanning electron microscopy−energy-dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) techniques after applying processes at optimized conditions. The EDS spectrum showed that the recovered precipitates and TiO 2 contained the lead (Pb) element. The XRD peak analysis showed that precipitates contained lead having the crystallite size of around 90 nm, whereas the XRD spectrum of recovered titanium dioxide indicated additional peaks at specific angles, showing lead deposition on the TiO 2 surface. The rate of photocatalytic removal of lead ions (Pb 2+ ) followed the Langmuir−Hinshelwood equation of the first order.

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“…Under the light, AO provides an electron to EY excited species for reduction, which inhibited the EY excited species from obtaining electrons from the electrode and retarded the electrochemical reduction. 54 This phenomenon was only observed in light. Under dark, the reduction peak intensity was almost analogous to EY (Supporting Information, Figure S10).…”

Section: Electrochemical/photo-electrochemical Studiesmentioning

confidence: 98%

Photosensitized Radical-Anion-Driven Metal-Free Selective Reduction of Aldehydes Using Graphene Oxide as an Electron Relay Mediator under Visible Light

Saini

Kumar

Sethi

et al. 2023

ACS Appl. Mater. Interfaces

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Despite the modern boost, developing a new photocatalytic system for the reduction of aldehydes is still challenging due to their high negative reduction potential. Herein, we have used a metal-free photoinduced electron-transfer system based on a cheap and readily available organic dye eosin Y (EY), graphene oxide (GO), and ammonium oxalate (AO) for photocatalytic reduction of structurally diverse aldehydes under sustainable conditions. The protocol shows remarkable selectivity for the photocatalytic reduction of aldehydes over ketones. The decisive interaction of GO and AO with the various states of EY (ground, singlet, triplet, and radical anions), which are responsible for the commencement of the reaction, was examined by various theoretical, optical, electrochemical, and photo-electrochemical studies. The synergetic system of GO, EY, and AO is appropriate for enhancing the separation efficiency of visible-light-induced charge carriers. GO nanosheets act as an electron reservoir to accept and transport photogenerated electrons from the photocatalytic system to the reactant. The reduction of the GO during the process ruled out the back transfer of photoexcited charges. Control experiments explained that the reaction involves two stages: electron transfer and protonation. This process eliminates the necessity of precious-metal-based photocatalysts or detrimental sacrificial agents and overcomes the redox potential limitations for the photoreduction of aldehydes.

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Characteristics and mechanism of uranium photocatalytic removal enhanced by chelating hole scavenger citric acid in a TiO2 suspension system

Cited by 17 publications

References 48 publications

Adsorption and Mechanism of Glycine on the Anatase with Exposed (001) and (101) Facets

Adsorption and Mechanism of Glycine on the Anatase with Exposed (001) and (101) Facets

Photocatalytic Reduction and Crystallization Hybrid System for Removal and Recovery of Lead (Pb)

Photosensitized Radical-Anion-Driven Metal-Free Selective Reduction of Aldehydes Using Graphene Oxide as an Electron Relay Mediator under Visible Light

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