RESUMEN
Hexavalent chromium [Cr(VI)] is considered a serious environmental pollutant that possesses a hazardous effect on humans even at low concentrations. Thus, the development of a bifunctional material for ultratrace-selective detection and effective elimination of Cr(VI) from the environment remains highly desirable and scarcely reported. In this work, we explore an imidazolium-appended polyfluorene derivative PF-DBT-Im as a highly sensitive/selective optical probe and a smart adsorbent for Cr(VI) ions with an ultralow detection limit of 1.77 nM and removal efficiency up to 93.7%. In an aqueous medium, PF-DBT-Im displays obvious transformation in its emission color from blue to magenta on exclusively introducing Cr(VI), facilitating naked-eye colorimetric detection. Consequently, a portable sensory device integrated with a smartphone is fabricated for realizing real-time and on-site visual detection of Cr(VI). Besides, the imidazolium groups attached onto side chains of PF-DBT-Im are found to be highly beneficial for achieving selective and efficient elimination of Cr(VI) with capacity as high as 128.71 mg g-1. More interestingly, PF-DBT-Im could be easily regenerated following treatment with KBr and can be recycled at least five times in a row. The main factor behind ultrasensitive response and excellent removal efficiency is found to be anion-exchange-induced formation of a unique ground-state complex between PF-DBT-Im and Cr(VI), as evident by FT-IR, XPS, and simulation studies. Thus, taking advantage of the excellent signal amplification property and rich ion-exchange sites, a dual-functional-conjugated polymer PF-DBT-Im is presented for the concurrent recognition and elimination of Cr(VI) ions proficiently and promptly with great prospects in environmental monitoring and water decontamination.
RESUMEN
Nano zerovalent iron (nZVI) and CaO2 were used to construct a heterogeneous Fenton-like system to degrade α-hexachlorocyclohexane (α-HCH) in soil solution, and the degradation efficiency and mechanism were investigated. The results showed that nZVI/CaO2 can degrade α-HCH in an extensive pH range. When the dosage of nZVI and CaO2 was 1 g·L-1 and pH was 5, the degradation rate of α-HCH reached 93.23%. The degradation process of nZVI, CaO2, and nZVI/CaO2 treatments accorded with the first-order reaction kinetics model. The reaction rate constant of nZVI/CaO2 was greater than the sum of individual treatments, showing that nZVI/CaO2 has a synergistic effect on the degradation of α-HCH. Through quenching free radical experiments, the contribution rate of superoxide radicals was shown to be greater than that of hydroxyl radicals. Intermediates, including trichlorobenzene and chlorobenzene, were detected. The content of trichlorobenzene showed a sharp increase initially, and then decreased quickly. The chlorobenzene content was low and showed little change. The α-HCH in the soil washing solution was first reduced to trichlorobenzene, which was further reduced to chlorobenzene or mineralized into CO2 and water directly.
RESUMEN
Totally 126 samples of windowsill dust were collected from different floors along elevated road in Changzhou. The concentrations of Cu, Zn, Pb, Cd, Ni and Cr were determined, and the vertical distribution and chemical speciation were analyzed. The enrichment factor, bioaccessiblity, potential ecological risk and health risk were evaluated. The results showed that the average contents of Cu, Zn, Pb, Cd, Ni and Cu were 181.95, 709.99, 211.24, 2.76, 101.59 and 257.55 mg·kg-1 respectively, which were all higher than the background value. The enrichment factor of Cd was 33.05, with enrichment degree of strongly enriched. The enrichment degrees of Cu, Pb and Zn were all significantly enriched. These four heavy metals may come not only from transportation source, but also from natural source and regional industrial polluted gas. The enrichment factors of Ni and Cr were low, which may result from natural source. With the elevation of house height, the concentration of Cd increased, the concentrations of Pb and Zn increased first and then decreased, while Cu showed no significant differences. Zn, Cd, Cu and Pb mainly existed in the active form, while Ni and Cr mainly existed in the residual form. The bioaccessiblity of Zn and Cd was high, while that of other heavy metals was low. The modified potential ecology risk evaluation results showed that the risk of Cd was extremely high, and contributed mainly to the potential risk index of multi-element. The Cd from the windowsill of high height showed higher potential ecological risk. The carcinogenic risk of Cr to children was higher than the threshold value, while the carcinogenic risk and non-carcinogenic risk of other metals to children and adults were all below the safety thresholds.
