N/S-doped carbon embedded with AgNPs as a highly efficient catalyst for the reduction of toxic organic pollutants
Introduction
Water reservoirs contain usually organic and inorganic toxic pollutants [1], [2]. Nitroarenes are one of them and widely used for manufacturing of drugs, dyes and pesticides and need to treat before expose to the environment. However, the catalytic reduction of 4-NP to 4-aminophenol (4-AP) in aqueous medium emanates as an efficient and environmentally friendly technique [3]. Several noble metals nanoparticles such as AuNPs, CuNPs, AgNPs, PtNPs and PdNPs have been used for the reduction of 4-NP to 4-AP, due to their excellent physiochemical properties but limits because of their high-cost [4]. Therefore, the development of low-cost, highly stable and efficient catalyst is highly desirable. Graphite and graphitic carbons are excellent electrical conductors and used for charge transfer, chemical sensors and photocatalysts as well as catalyst support. After doping of heteroatoms into the graphite carbon, its properties such as surface area, adsorption of organic pollutants, charge transfer and many more was increased. Therefore the N/S doped carbon promotes the catalytic activities of the catalyst and reduce the cost of the catalyst. In this study, a reusable, easily retrievable, fast and highly effective novel catalyst has been fabricated using silver polymer complex via hydrothermal and post reduction methods. The fabricated catalyst (AgNPs@NSC) shows excellent catalytic activities for the reduction of 4-NP to 4-AP.
Section snippets
Experimental
AgNPs@NSC was prepared via hydrothermal treatment of the silver polymer complex. The silver polymer complex was prepared via polycondensation of diphenylthiourea and formaldehyde with silver nitrate. In a 100 mL beaker, 6 gm of diphenylthiourea was dissolved in 10 mL distilled water and5 mL formaldehyde (37% aqueous solution) was added to this solution, the pH was controlled 8 using aqueous NaOH solution. The resulting mixture was heated at 60 °C with continues starring for 20 min, after that 2
Results and discussion
The synthetic route of AgNPs@NSC is illustrated schematically in Fig. 1(a). The elemental analysis and ICP results revealed that the nanocomposite contains 48.21% C, 13.24% N and 6.2% sulphur, and 24.21% silver. The FTIR spectra as shows in Fig. 1(b), shows several main peaks at 3422, 3010, 2950–2834, 1632, 1414 and 1120, 542 and 495 cm−1 assigned to OH, CH, CH, CC, CN, OCO, CH2-O and Ag-O vibration respectively. Figure (SF-1), shows the Uv–visible spectrum and a broad high intense band at
Catalytic reduction
The catalytic reduction of 4-NP to 4-AP in the presence of NaBH4 using AgNPs@NSC was carried out at room temperature. No catalytic activity was observed in the case of N/S doped carbon. As shown in figure-3(a), 4-NP shows adsorption peak at 317 nm, and after the addition of the NaBH4, red shift was occurs and the adsorption peak appear at 400 nm, as the color of the solution change bright yellow due to the formation of phenolate ions [9]. The yellow color of phenolate ions was unchanged, even
Conclusion
In this study, we fabricate a novel catalyst via efficient strategy in which the ultrafine Ag NPs (4.0 nm) were embedded in N, S doped graphite carbon matrix via the post-reduction method by NaBH4. The catalyst sow excellent catalytic activities and reaction followed a pseudo first order kinetics with k value of 8.59 × 10−3 min−1. The hybrid AgNPs@NSC showed highly enhanced catalytic activity for the reduction of 4-NP in just 6 min due to its, large surface area, heterojunctions between AgNPs
CRediT authorship contribution statement
Tansir Ahamad: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Visualization, Writing - original draft, Writing - review & editing. Mu. Naushad: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Resources, Software, Supervision, Validation, Visualization, Writing - original draft, Writing - review & editing. Sameerah I.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgement
The authors extend their sincere appreciation to the Deanship of Scientific Research at King Saud University for funding this Research Group (RG-1438-026). This work was also funded by the Deanship of Scientific Research at Princess Nourah Bint Abdulrahman University through the Fast-track Research Funding Program.
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