The treatment of industrial wastewater containing Cr(VI)–organic compounds is a long-term concern in the field of environment. In order to realize the high-efficient reduction of Cr(VI) and solve the problem of Cr(III) residue in water environment, a novel catalytic chemical reduction/membrane filtration method was developed for the removal of total Cr (TCr) in a system with coexisting Cr(VI) and oxalate (Ox). The effects of the concentrations of Ox, Fe(III), and Al(III), the dosage of NaBH 4 , and sedimentation time on the removal of Cr(VI) containing Ox by NaBH 4 were investigated. Additionally, the simultaneous removal of turbidity and TCr using a microfiltration membrane was investigated, and the reason for the enhanced TCr removal was clarified. The results of ion chromatography (IC), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) suggested that when Cr(VI) and Ox coexist, low concentrations (0.3 mM) of Fe(III) or Al(III) contributed significantly to the high turbidity caused by the formation of suspended solids (SS) following the reduction of Cr(VI) by NaBH 4 . However, almost all the Cr(III) could be removed by a 1-μm microfiltration membrane. The high turbidity system formed by Ox and Cr(III) is unstable, and some Ox will gradually release their binding sites with Cr(III) with the extension of the natural settling time. For 24 h, 53.75% of Ox was involved in the formation of SS, while in the presence of Fe(III) or Al(III), only 11.28% and 6.30% of Ox were involved, respectively. High concentrations of Fe(III) and Al(III) enhanced the reduction of Cr(VI) by NaBH 4 . The removal of TCr was close to 100% after natural sedimentation for 15 min and combined with a microfiltration membrane. This result is caused because Fe(III)–Cr(III) or Al(III)–Cr(III) can form larger SS, which is easily intercepted by the microfiltration membrane. The development of a novel combined method of catalytic chemical reduction and membrane filtration will be beneficial for reducing the retention of TCr in the environment.
An Yingying,Wang Wan,Lv Qing,Zhang Qing,Wang Xiayan
A paper-based analytical device (PAD) is presented with colorimetric/electrochemical dual readouts for the simultaneous sensing of total chromium (Cr) and hexavalent chromium (Cr(VI)). This device consists of a homemade three-electrode system and a patterned paper chip, integrating multiple functions including electrochemical detection, fluid driving, online oxidation, and colorimetric detection. The fiberglass filter paper with a hydrophilic microchannel was used to achieve self-driving fluidics without external equipment. One end of the microchannel was integrated with a homemade three-electrode system to achieve sample loading and electrochemical detection. The middle region on the microchannel was modified with oxidizing reagents to perform online pretreatment, and the yield of Cr(III) oxidation can reach 97.9%, ensuring reliable colorimetric detection of total Cr at another end of the microchannel modified with chromogenic agents. With this device, the signals of Cr(VI) (the signal peak at 0.29 V vs. Ag/AgCl) and total Cr can be obtained in one single injection. After optimization, the limit of detection (LOD) of Cr(VI) and total Cr were 0.01 mg L −1 and 0.06 mg L −1 and the linear ranges were 0.05–3.0 mg L −1 and 0.2–3.0 mg L −1 , respectively. The relative standard deviations (RSD) of the electrochemical testing of Cr(VI) results were in a range 1.3%–8.7% ( n = 3), and the RSD values of the colorimetric testing of total Cr were between 0.7–9.2% ( n = 3). The device’s reliability was demonstrated by performing the practical speciation of Cr in tap water, river water, and electroplating wastewater while the recoveries obtained using the present method were in the range 93.5–106%. Overall, the proposed device provides high application prospect in the on-site rapid Cr speciation. Graphical abstract
Heavy metal contamination in water bodies poses a severe threat to ecosystems and human health, thereby necessitating the development of rapid and highly sensitive detection methods. Traditional laboratory detection techniques are limited in their widespread application due to expensive equipment and complex operational procedures. To address this issue, we developed a rapid detection technique based on AuAgPd trimetallic nanoparticles(TNPs)-modified filter paper combined with laser-induced breakdown spectroscopy (LIBS) for the determination of total chromium (Cr) in water. AuAgPdTNPs-modified filter paper efficiently enriches Cr of different valence states, while LIBS quantifies total Cr from its characteristic emission lines. Experimental results demonstrate that the limit of detection (LOD) of total Cr is 0.21 μg/L (4 nM), showing good linearity in the ranges of 0–50 μg/L and 50–1000 μg/L. In tests with actual water samples, the method showed high reliability, with recovery rates ranging from 95.24 % to 106.15 %. This technology provides a novel solution for the rapid detection of heavy metal pollution in water bodies and holds broad application prospects.
危险品化学品经营许可证（带存储）