One-pot synthesis of Mn-doped TiO 2 grown on graphene and the mechanism for removal of Cr(VI) and Cr(III)

Chen, Zengping; Li, Yaru; Guo, Meng; Xu, Fengyun; Wang, Peng; Du, Yu; Na, Ping

doi:10.1016/j.jhazmat.2016.02.034

Cited by 112 publications

(25 citation statements)

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“…The high photocatalytic activity is attributed to the Mn doping and synergetic effect of adsorption and photocatalysis by the RGO support. The photogenerated electrons are transported from the Mn-doped TiO 2 through RGO and were found to reduce the adsorbed Cr(VI) [137]. A Ti–SBA-15–g-C 3 N 4 material was also shown to exhibit higher Cr(VI) photoreduction under visible light illumination.…”

Section: Reviewmentioning

confidence: 99%

“…Even after five cycles, there was no decrease of the performance of the catalyst, showing its high photostability [134]. RGO–Mn–TiO 2 exhibited excellent stability with the high Cr(VI) removal efficiency of 96.61%, even after three cycles [137]. Wang and co-workers reported that graphene foam/TiO 2 nanosheet hybrids could be promising in practical water treatment applications for removal of both Cr(VI) ions and organic dyes as these exhibited excellent recycle stability and easy recoverability [232].…”

Section: Reviewmentioning

confidence: 99%

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Cr(VI) remediation from aqueous environment through modified-TiO₂-mediated photocatalytic reduction

Acharya

Naik

Parida

2018

Beilstein J. Nanotechnol.

108

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Cr(VI) exhibits cytotoxic, mutagenic and carcinogenic properties; hence, effluents containing Cr(VI) from various industrial processes pose threat to aquatic life and downstream users. Various treatment techniques, such as chemical reduction, ion exchange, bacterial degradation, adsorption and photocatalysis, have been exploited for remediation of Cr(VI) from wastewater. Among these, photocatalysis has recently gained considerable attention. The applications of photocatalysis, such as water splitting, CO2 reduction, pollutant degradation, organic transformation reactions, N2 fixation, etc., towards solving the energy crisis and environmental issues are briefly discussed in the Introduction of this review. The advantages of TiO2 as a photocatalyst and the importance of its modification for photocatalytic reduction of Cr(VI) has also been addressed. In this review, the photocatalytic activity of TiO2 after modification with carbon-based advanced materials, metal oxides, metal sulfides and noble metals towards reduction of Cr(VI) was evaluated and compared with that of bare TiO2. The photoactivity of dye-sensitized TiO2 for reduction of Cr(VI) was also discussed. The mechanism for enhanced photocatalytic activity was highlighted and attributed to the resultant properties, namely, effective separation of photoinduced charge carriers, extension of the light absorption range and intensity, increase of the surface active sites, and higher photostability. Advantages and limitations for photoreduction of Cr(VI) over modified TiO2 are depicted in the Conclusion. The various challenges that restrict the technology from practical applications in remediation of Cr(VI) from wastewater were addressed in the Conclusion section as well. The future perspectives of the field presented in this review are focused on the development of whole-solar-spectrum responsive, TiO2-coupled photocatalysts which provide efficient photocatalytic reduction of Cr(VI) along with their good recoverability and recyclability.

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Section: Reviewmentioning

confidence: 99%

Section: Reviewmentioning

confidence: 99%

Cr(VI) remediation from aqueous environment through modified-TiO₂-mediated photocatalytic reduction

Acharya

Naik

Parida

2018

Beilstein J. Nanotechnol.

108

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“…TiO2 has a band gap (Eg) of~3.2 eV and the CB energy edge position is ~−4.4 eV with respect to the absolute vacuum scale or− 0.29 eV with respect to NHE, which is considerably above the reduction potential of Cr(VI)/Cr(III). Several groups have reported the photocatalytic reduction of Cr(VI) using TiO2 as photocatalyst [20][21][22]. However, the poor harvesting of solar energy and charge carrier separation limit its photoreduction rate for Cr(VI).…”

Section: Introductionmentioning

confidence: 99%

Multicycle photocatalytic reduction of Cr(VI) over transparent PVA/TiO2 nanocomposite films under visible light

et al. 2017

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Photocatalytic reduction of hexavalent chromium in wastewater has been widely investigated as an attractive treatment method. In this work, we reported an efficient method for photocatalytic reduction of Cr(VI) over transparent polyvinyl alcohol/titanium dioxide (PVA/TiO2) nanocomposite films under sunlight irradiation. The transparent PVA/TiO2 nanocomposite films were prepared by a simple hydrothermal method combined with a solution casting process. The results revealed that the anatase TiO2 nanoparticles with size less than 10 nm were in-situ generated in PVA matrix, which endowed the films with high transparency. Photocatalytic reduction of Cr(VI) over PVA/TiO2 nanocomposite films exhibited superior visible light photocatalytic activity. Mechanism investigation demonstrated that the PVA acted not only as a transparent support for TiO2 nanoparticles, but also as holes scavengers simultaneously to improve the separation of photogenerated holes and electrons. Meanwhile, the transparent PVA/TiO2 nanocomposite films displayed remarkable stability and excellent recyclability during multicycle Cr(VI) photoreduction. Furthermore, the PVA/TiO2 nanocomposite films showed selective adsorption ability for Cr(III), and thus totally removal of Cr(VI) was achieved after photoreduction process.

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“…Generally, the majority of these pollutants cannot degrade by themselves, such as hexavalent chromium Cr(VI) and divalent lead Pb(II). Hexavalent chromium is a kind of strong oxidant and highly soluble heavy metal with carcinogenic, mutagenic and teratogenic substance for human [1,2]. Based on its long-term impact, Cr(VI) has been listed as the first-class A toxic pollutant by the U.S. Environmental Protection Agency [3].…”

Section: Introductionmentioning

confidence: 99%

Different Insights into Silicate Rectorite Modification and Its Role in Removal of Heavy Metal Ions from Wastewater

Gao¹,

Jiang²,

Li³

et al. 2020

Minerals

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In the field of water management, the separation of metal contaminants from wastewater is very important and challenging. This study systematically investigated the effect and underlying mechanism of silicate rectorite (REC) on the removal of heavy metal ions (Cr(VI) and Pb(II)) from wastewater. The adsorption and removal capacity of REC was further improved by its novel modification with ferric chloride hexahydrate. Compared to natural REC, the modified rectorite (Fe-REC) showed comparatively superior adsorption efficiency for both Cr(VI) and Pb(II) due to the chemisorption of Fe 3+ on the REC surface as its oxidation state (Fe-O, Fe-OH, Fe-OOH). Adsorption on Cr(VI) attributed to the reaction between iron hydroxy complexes (FeOH 2+ , Fe(OH) 2 + and Fe(OH) 3 (aq)) and Cr(VI) species (HCrO 4 − and CrO 4 2− ) in the aqueous solution. This reaction was perfectly consistent with the binding energy shifts in O 1s and Fe 2p species, as reflected by XPS analysis. While, the existence of -Al-OH and -Si-OH in silicate REC slurry reacted with PbOH + colloids produced from lead ions hydrolysis to promote Pb(II) adsorption. Zeta potential after modification and removal occurred to shift positively or negatively to testify the adsorption of Fe 3+ and heavy metal ions. Freundlich and Langmuir isotherms conformed adsorption process for Cr(VI) and Pb(II), respectively.Minerals 2020, 10, 176 2 of 16 and economical approach that is widely used in wastewater treatment procedures. In adsorption, a variety of adsorbent including activated carbons, clay mineral, biomasses and synthetic polymers was employed [8,[10][11][12][13]. However, common adsorbents such as activated carbon are expensive, thus some natural resources such as polysaccharides, fly ash and clay have attracted much attention due to their low cost and easy access. In this series of materials, rectorite (REC) was applied more and more in pollutant adsorption from sewage owing to its low cost, high ion exchange capacity and relatively large specific area [14][15][16][17]. It is a sort of rare regularly interstratified silicate and similar to kaolinite. Its special structure is alternate pairs of dioctahedral mica-like layer (non-expansible) and dioctahedral smectite-like layer (expansible) existing in 1:1 ratio. There are some cations (Na + , K + and Ca 2+ ) and hydrated cations with exchangeability, which can enlarge its interlayer distance by intercalating cations or polar molecules existing in the interlayer regions.Over several decades, there are more and more investigations on the adsorption of metal ions by REC or its synthesis [17][18][19][20][21]. For example, Mei et al. [17] and Zhao et al. [22] studied separately the adsorption behaviors of Pb(II) by Ca-rectorite and Sr(II) by Na-rectorite as a function of different environmental parameters including the influence of pH, temperature, ionic strength and humic acid (HA) under ambient conditions. Both of them found that the adsorption results of heavy metals were intensely decided by pH and ionic strength and the...

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One-pot synthesis of Mn-doped TiO 2 grown on graphene and the mechanism for removal of Cr(VI) and Cr(III)

Cited by 112 publications

References 50 publications

Cr(VI) remediation from aqueous environment through modified-TiO₂-mediated photocatalytic reduction

Cr(VI) remediation from aqueous environment through modified-TiO₂-mediated photocatalytic reduction

Multicycle photocatalytic reduction of Cr(VI) over transparent PVA/TiO2 nanocomposite films under visible light

Different Insights into Silicate Rectorite Modification and Its Role in Removal of Heavy Metal Ions from Wastewater

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One-pot synthesis of Mn-doped TiO 2 grown on graphene and the mechanism for removal of Cr(VI) and Cr(III)

Cited by 112 publications

References 50 publications

Cr(VI) remediation from aqueous environment through modified-TiO2-mediated photocatalytic reduction

Cr(VI) remediation from aqueous environment through modified-TiO2-mediated photocatalytic reduction

Multicycle photocatalytic reduction of Cr(VI) over transparent PVA/TiO2 nanocomposite films under visible light

Different Insights into Silicate Rectorite Modification and Its Role in Removal of Heavy Metal Ions from Wastewater

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About

Cr(VI) remediation from aqueous environment through modified-TiO₂-mediated photocatalytic reduction

Cr(VI) remediation from aqueous environment through modified-TiO₂-mediated photocatalytic reduction