Monitoring graphene oxide's efficiency for removing Re(VII) and Cr(VI) with fluorescent silica hydrogels. (July 2020)

• Record Type: Journal Article
• Authors: Tang, Chuanqi; Zhang, Yiming; Han, Jiangang; Tian, Ziqi; Chen, Liang; Chen, Jianqiang
• Is Part Of: Environmental pollution. Volume 262(2020)
• Publication Date: 2020-07
• Subjects: Nitrogen-doped carbon quantum dots -- Re(VII) and Cr(VI) detection -- Graphene oxide -- Silica hydrogels -- Density functional theory; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2020.114246
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: Supported carbon quantum dots (CQDs), used as fluorescent sensors for the detection of metal ions, have rarely been used to remove heavy metals from water. Nitrogen-doped CQDs immobilized in hydrophilic silica hydrogels exhibited a more superior sensitivity and selectivity for the detection of Re(VII) and Cr(VI) than other metal ions, including Fe(III), Fe(II), Zn(II), Cu(II) and Mn(II). For the first time, low limits of detection (LOD) of 2.3 μM for Re(VII) detection and 65 nM for Cr(VI) detection were reported by a facile method. Based on the high selectivity of fluorescent silica hydrogels for Re(VII) and Cr(VI) detection, the removal of Re(VII) and Cr(VI) by graphene oxide (GO) in water was monitored with the hydrogels used as a turn-off fluorescent sensing platform. The consistent results of the sorption isotherms of each metal on GO, which were obtained from the fluorescence spectra and by UV absorption, further verified the possibility of monitoring metal removal by fluorescence detection. Remarkably, GO removed 1186 mg/g of Re(VII) but only 178 mg/g of Cr(VI). The density functional theory (DFT) calculations indicated that both Re(VII) and Cr(VI) formed stable bonds with silica hydrogels, confirming that the interactions between the metal ions and the substrate would promote the fluorescence quenching of the supported CQDs. On the other hand, Re(VII) interacted more strongly with the carboxyl groups of GO than Cr(VI). In addition, a real-time detection system was designed to alarm the service life of a GO filter used for Re(VII) removal. Graphical abstract: Image 1 Highlights: Detection of Re(VII) by CQDs@silica hydrogels was studied for the first time. CQDs@silica hydrogels with good selectivity for Re(VII) and Cr(VI) detection. GO displayed highly efficient in removing Re(VII). Real-time detection system for alarming service life of a GO filter. Abstract : Re(VII) and Cr(VI) absorption by GO was monitored by the fluorescence quenching of CQDs@silica hydrogels with a high sensitivity for metal detection.