Visualizing stimulus-responsive dual-ligand fluorescent probes for hypochlorite: A novel strategy for real application in tap water.

As an effective ingredient of disinfectants, ClO- inevitably remains in water, which induces potential health hazards such as lung damage and kidney disease. In this study, we synthesized stimulus-responsive dual-ligand luminol-Tb-GMP coordination polymer nanoparticles (luminol-Tb-GMP CPNPs) as highly selective fluorescent probes for the real-time and visual detection of ClO- . CPNPs consist of Tb3+ , a nuclear metal, that coordinates with GMP and luminol, an auxiliary ligand. GMP can be oxidized by ClO- and damage its structure, resulting in fluorescence quenching of CPNPs. The two-ligand CPNPs sensor has a rapid fluorescent response, significant fluorescent color change, and high sensitivity, with a linear range of 2-18 µM and a detection limit of 0.14 µM. It has been successfully used to detect ClO- in tap water, fountain water, and drinking water. Simultaneously, the portable filter paper strip was prepared to expand the range of applications outside the laboratory, which will provide a promising application for the real-time and semiquantitative analysis of ClO- .

Extraction of extracellular polymeric substances (EPS) from indigenous bacteria of rare earth tailings and application to removal of thorium ions (Th4+).

Thorium, as an important radioactive element, is widely present in nature, and its accompanying environmental pollution is also serious. Extracellular polymeric substances (EPS) are commonly found on the surface of microbial bodies and have strong adsorption capacity for metal ions. In this study, four methods were used to extract EPS from indigenous bacteria of rare earth tailings and to determine the best extraction method. The extracted EPS was applied to treat Th4+, and the changes in functional groups and composition of EPS were investigated. The results showed that the ultrasonic method was more efficient than other methods. The best removal efficiency was observed at pH 3.5, Th4+ concentration of 20 mg/L, and EPS dosage of 30 mL at 25 °C. After 9 h, the adsorption process reached equilibrium with a maximum removal efficiency of 75.93% and a maximum theoretical adsorption capacity of 25.96 mg/g. The Th4+ removal process was consistent with the Langmuir and Freundlich adsorption isotherms and the kinetic data were consistent with the pseudo-second-order kinetic model, which is mainly based on chemisorption. Amide I and amide II of proteins, C-H from aliphatic, as well as O-H and C = O from carboxylic acid play important roles in the adsorption process.

Adsorption of Pb2+ from aqueous solutions using Fe-Mn binary oxides-loaded biochar: kinetics, isotherm and thermodynamic studies.

This study evaluated the removal of Pb2+ in aqueous solution using Fe-Mn binary oxides-loaded biochar (BFMs). The characteristics of BFM were obtained using a scanning electron microscopy, an energy dispersive spectrometer (EDS), Brunauer-Emmett-Teller, a X-ray diffraction (XRD), and a X-ray photoelectron spectroscopy (XPS). The effects of pH, adsorbent dose, contact time, initial Pb2+ concentration, and temperature in the batch sorption experiments were investigated. Adsorption was evaluated by adsorption kinetics, isotherm models, and thermodynamics. With the initial Pb2+ concentration of 200 mg/L, pH 4, and 298.15 K, the optimum adsorption of BFM was obtained at a reaction time of 300 min, adsorbent dose of 2 g/L, and maximum adsorption capacity of 113.715 mg/g. Furthermore, the kinetics was best fitted to the pseudo-second-order model, whereas the adsorption equilibrium was best described by the Langmuir isotherm model. This result indicated that Pb2+ was adsorbed onto BFM by chemical interactions through the monolayer. The adsorption was spontaneous (ΔG < 0) and endothermic (ΔH > 0).

Functionalized biochar-supported magnetic MnFe2O4 nanocomposite for the removal of Pb(ii) and Cd(ii).

In this study, a novel magnetic biochar-MnFe2O4 nanocomposite (BC/FM) was prepared using low-cost corn straw and MnFe2O4 by sol-gel/pyrolyzing route using egg white, which has abundant functional groups (-NH2 and -COOH). Following that, its composition, morphology and structure was characterized by various techniques including SEM-EDX, BET, XRD, and VSM. Batch experiment of the adsorption for Pb(ii) and Cd(ii) including influence of pH, kinetics, isotherm and thermodynamics was also studied. The results demonstrated that biochar could effectively support MnFe2O4, which displayed high dispersion on the surface of the biochar and possessed abundant functional groups and high surface area contributing to superior performance on Pb(ii) and Cd(ii) removal. Therein, MnFe2O4 with high magnetism is convenient for separating the magnetic BC/FM from an aqueous medium. Adsorption experiment results indicate that Pb(ii) and Cd(ii) removal by BC/FM was closely related to pH with the best value of pH 5.0, and the process reached equilibrium in 2 h. The adsorption process is well-described by the pseudo-second-order kinetic model and Sips (Freundlich-Langmuir) model. Thermodynamic studies suggest that the adsorption process is spontaneous and exothermic. The maximum experimental adsorption capacity of BC/FM is 154.94 and 127.83 mg g-1 for Pb(ii) and Cd(ii), respectively, in single-solute system, which is higher than that of some of the other adsorbents of biochar or biochar-based composites. In bi-solute system, the preferential adsorption order of BC/FM for the two metals is Pb(ii) prior to Cd(ii). Finally, FTIR and XPS analysis verified that the main mechanism of Pb(ii) and Cd(ii) removal by BC/FM is by forming Pb/Cd-O or complexation of carboxyl and hydroxyl and ion exchange. Therefore, the prepared magnetic BC/FM composite, as an excellent adsorbent, exhibited potential applications for the removal of Pb(ii) and Cd(ii) from wastewater.

[Soil Heavy Metal Spatial Distribution and Source Analysis Around an Aluminum Plant in Baotou].

The soil with 500 m distance from an aluminum plant in Baotou was studied. A total of 64 soil samples were taken from the 0-5 cm, 5-20 cm, 20-40 cm and 40-60 cm layers, and the contents of Cu, Pb, Zn, Cr, Cd, Ni and Mn were tested, respectively. The correlation analysis and principal component analysis were used to identify the sources of these heavy metals in soils. The results suggested that the contents of Cu, Pb, Zn, Cr, Cd, Ni and Mn in study area were 32.9, 50.35, 69.92, 43.78, 0.54, 554.42 and 36.65 mg · kg⁻¹ respectively. All seven heavy metals tested were overweight compared with the background values of soil in Inner Mongolia. The spatial distribution of heavy metals showed that the horizontal distribution of heavy metals was obviously enriched in the southwest, while in vertical distribution, the heavy metal content (0 to 5 cm) was highest in the surface soil, and the heavy metal content decreased with increasing depth and tended to be stabilized when the depth was over 20 cm. Source analysis showed that the source of Cu, Zn, Cr and Mn might be influenced by the aluminum plant and the surrounding industrial activity. The source of Pb and Cd might be mainly related to road transportation. The source of Ni may be affected by agricultural activities and soil parent material together.