Hollow spheric Ag–Ag2S/TiO2 composite and its application for photocatalytic reduction of Cr(VI)

Zhang, Dandan; Xu, Gang‐Ming; Chen, Feng

doi:10.1016/j.apsusc.2015.06.044

Cited by 36 publications

(13 citation statements)

References 36 publications

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“…Photoreduced Ag acted as a bridge that transferred the electrons from Co 3 O 4 to TiO 2 for simultaneous Cr(VI) reduction and pollutant oxidation. Hollow spherical Ag–Ag 2 S–TiO 2 was prepared through in situ chemical transformation of sacrificial Cu 2 S templates with AgNO 3 solution [219]. The enhanced photoreduction of Cr(VI) is attributed to the synergetic effect of the heterojunction and Schottky barrier that transfer the photogenerated electrons more efficiently.…”

Section: Reviewmentioning

confidence: 99%

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

Acharya

Naik

Parida

2018

Beilstein J. Nanotechnol.

112

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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%

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

Acharya

Naik

Parida

2018

Beilstein J. Nanotechnol.

112

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“…19 Therefore, reductive transformation of Cr(VI) to Cr(III) is a widely used approach to eliminate the pollution of Cr(VI). [28][29][30] Few studies focused on the Cr(VI) reduction by HCOOH with the catalysis of Agbased materials, since there is no report that Ag can catalyze the dehydrogenation of HCOOH to produce H2. 23 In the catalytic process, the HCOOH undergoes a dehydrogenation reaction to produce H2 and CO2 (HCOOH→CO2+H2), 24,25 then the H2 is adsorbed on the surface of Pt or Pd, to form active H species, which are further transferred to the Cr(VI), finally reducing Cr(VI) to Cr(III) (CrO4 2-+ 10H + + 6H → 2Cr 3+ + 8H2O).…”

Section: Introductionmentioning

confidence: 99%

One-pot high yield synthesis of Ag nanoparticle-embedded biochar hybrid materials from waste biomass for catalytic Cr(vi) reduction

Liu

Ling

Wang

et al. 2016

Environ. Sci.: Nano

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Disposal of heavy metals contaminated biomass obtained from phytoremediation or biosorption by environmentally benign methods is a big challenge. In this study, we proposed a win-win strategy to recycle the Ag contaminated biomass by fast pyrolysis to obtain renewable bio-oil and catalytic reduction of Cr(VI) with the Ag-embedded biochar. We herein focused on the one-pot preparation of Ag nanoparticles embedded biochar hybrid material (Ag@biochar) by fast pyrolysis of the Ag preloaded biomass and their catalytic effect on Cr(VI) reduction. The results show that Ag@biochar can totally catalytic reduce the Cr(VI) in aqueous solution within 20 min using formic acid as a reducing agent at 323 K. The particle size of AgNPs on biochar was found as pyrolysis-temperature dependent and played an important role in the reduction of Cr(VI). We found the reduction of Cr(VI) catalyzed by Ag@biochar follows a CO (produced from HCOOH decomposition) reduction mechanism which is quite different from H2 reduction mechanism with the catalysis of some noble metal based catalysts (e.g., Pd and Pt). This study offered a sustainable approach for simultaneous disposal of the biomass waste and synthesis of functional materials, and might be expanded in the recycle of other metals contaminated biomass (e.g., Cu, Ni, Co, Zn, and Fe).The catalytic activity of the Ag@biochar was evaluated in the catalytic reduction of Cr(VI) with HCOOH, which was monitored by UV-vis spectroscopy. As shown in Fig. 5a, the intensity of the characteristic absorption peak of Cr(VI) at 353 nm decreases significantly with the increase of reaction time, suggesting that the Cr(VI) can be effectively converted by HCOOH with the catalysis of Ag@biochar. For comparison, the concentrations of Cr(VI) in two control experiments which employed only Ag@biochar or HCOOH (Fig. 5b), suggesting that the reduction of Cr(VI) cannot proceed without catalyst or HCOOH. When the raw biochar without Ag NPs was used for catalyst (Fig. 5b), the concentration of Cr(VI) only slightly decreased within 20 min, indicating that the activity of the Ag@biochar in the reduction of the Cr(VI) was mainly related to the excellent catalytic properties of the Ag NPs.The catalytic activity of the Ag@biochar is related to the particle size of Ag NPs, which is influenced by the pyrolysis temperature. Fig. 5c shows the Cr(VI) reduction with the catalysis of Ag@biochar formed in different temperatures. It can be seen that the catalytic activities of Ag@biochar-500 (average Ag particle size 7.6 nm) and Ag@biochar-600 (average Ag particle size 7.1 nm) are very similar, and both of them are much higher than that of Ag@biochar-400 (average Ag particle size 9.7 nm), suggesting that small Ag particles is favorable for catalyzing the Cr(VI) reduction with HCOOH. It can be explained as follows: firstly, there are more active sites in the Ag NPs with smaller size under the same conditions, offering more catalytic sites for the reactions; secondly, smaller particles may present a higher proportion of

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“…For example, Zhang, D. et al synthesized Ag-Ag 2 S/ TiO 2 hollow spheres, which took 180 minutes to photoreduce the ∼ 97 % of Cr(VI) by utilizing high energy UV light. [38] Ghafoor, S. et al reported TNFs embedded with g-C 3 N 4 nanosheets and decorated them with Ag NPs which exhibited 0.031 min À 1 pseudo-first order rate constant with almost 100 % photoreduction in 150 minutes. [11] Hence, it can be concluded that Ag deposition on P-doped TNFs showed excellent photoreduction of Cr(VI) under solar light illumination due to the synergistic effects discussed earlier.…”

Section: Photocatalytic Reduction Of Cr(vi)mentioning

confidence: 99%

P‐doped TiO₂ Nanofibers Decorated with Ag Nanoparticles for Enhanced Photocatalytic Activity under Simulated Solar Light

et al. 2020

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We report the synthesis of titania nanofibers (TNF) of ∼ 195 nm mean diameter doped with phosphorus through one-pot electrospinning followed by decoration of Ag nanoparticles (NPs). The Ag NPs of ∼ 8 nm size on 2 % P-doped TNFs (Ag-PTNFs) showed excellent photocatalytic activity for the reduction of Cr(VI), under simulated solar light, with ∼ 100 % conversion to Cr(III) in 90 min at pH 3 with a pseudo-first order rate constant of 0.085 min À 1 that is 96.5 % higher than TNFs. The Ag-PTNFs also exhibited excellent photodegradation of methylene blue with pseudo-first order rate constant of 0.052 min À 1 which is 82.7 % better than TNFs. The enhanced photocatalytic performance of Ag-PTNFs is attributed to the reduced band-gap, increased charge separation and reduced recombination rates. A proposed photocatalytic mechanism based on the synergistic effect of both Ag and P doping is presented which highlights the potential of these composite materials for water remediation.

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Hollow spheric Ag–Ag2S/TiO2 composite and its application for photocatalytic reduction of Cr(VI)

Cited by 36 publications

References 36 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

One-pot high yield synthesis of Ag nanoparticle-embedded biochar hybrid materials from waste biomass for catalytic Cr(vi) reduction

P‐doped TiO₂ Nanofibers Decorated with Ag Nanoparticles for Enhanced Photocatalytic Activity under Simulated Solar Light

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Hollow spheric Ag–Ag2S/TiO2 composite and its application for photocatalytic reduction of Cr(VI)

Cited by 36 publications

References 36 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

One-pot high yield synthesis of Ag nanoparticle-embedded biochar hybrid materials from waste biomass for catalytic Cr(vi) reduction

P‐doped TiO2 Nanofibers Decorated with Ag Nanoparticles for Enhanced Photocatalytic Activity under Simulated Solar Light

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Product

Resources

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

P‐doped TiO₂ Nanofibers Decorated with Ag Nanoparticles for Enhanced Photocatalytic Activity under Simulated Solar Light