AuPd nanoalloy and nanopalladium with a diameter of 5 nm were prepared, using sodium citrate as the stabilizing agent and NaBH(4) as the reductant. The nanocatalyst containing palladium on the surface exhibited a strong catalytic effect on the slow NiP particle reaction between NiCl(2) and NaH(2)PO(2), and the NiP particle system showed a resonance scattering (RS) peak at 508 nm. The RS results showed that the Pd atom on AuPd nanoalloy surface is the catalytic center. Combining the aptamer cracking reaction of double-stranded DNA (dsDNA)-UO(2)(2+), AuPd nanoalloy aggregation, and AuPd nanoalloy catalysis, both AuPd nanoalloy RS probe and AuPd nanoalloy catalytic RS assays were developed for the determination of 40-250 pmol L(-1) UO(2)(2+) and 5.0-50 pmol L(-1) UO(2)(2+), respectively.
A new resonance scattering method, based on resonance scattering (RS) effect, for the respective determination of ClO2 and Cl2 in water samples was developed. In HCl-NaAc buffer solutions with the pH value of 1.42, chlorine dioxide, or chlorine, oxidizes I- to form 12, which then reacts with the excess I- to form I3-. The resulting 13- would combine, respectively, with four rhodamine(Rh) dyes, including rhodamine B (RhB), butyl rhodamine B (b-RhB), rhodamine 6G (RhG), and rhodamine S (RhS), to form association particles which exhibit a stronger resonance scattering (RS) effect at 420 nm. For four systems of RhB, bRhB, RhG, and RhS, chlorine dioxide was, respectively, determined in the concentration range of 0.0056 to approximately 0.787 mg/L, 0.0034 to approximately 0.396 mg/L, 0.0057 to approximately 0.795 mg/L, and 0.0052 to approximately 0.313 mg/L, with the detection limits of 0.0011 mg/L, 0.006 mg/L, 0.0054 mg/ L, and 0.0023 mg/L ClO2, respectively. At the same experimental conditions as those for the determination of ClO2, chlorine was, respectively, determined in the concentration range of 0.013 to approximately 0.784 mg/L, 0.0136 to approximately 0.522 mg/ L, 0.014 to approximately 0.81 mg/L, and 0.014 to approximately 0.42 mg/L, with the detection limits of 0.0016 mg/L, 0.0104 mg/L, 0.0079 mg/L, and 0.0037 mg/L Cl2, respectively. The total RS value originally from ClO2 and Cl2 was recorded in the buffer solution, while the RS value from ClO2 was obtained by using dimethyl sulfoxide to mask chlorine. Thus the RS value of chlorine was calculated by deducting the RS value of chlorine dioxide from the total RS value. The RhB RS method was chosen for the determination of ClO2 and Cl2 in drinking water, with advantages of high sensitivity, good selectivity, simplicity, rapidity, and convenience.
Low-cost banana stalk (Musa nana Lour.) biochar was prepared using oxygen-limited pyrolysis (at 500 °C and used), to remove heavy metal ions (including Zn(II), Mn(II) and Cu(II)) from aqueous solution. Adsorption experiments showed that the initial solution pH affected the ability of the biochar to adsorb heavy metal ions in single- and polymetal systems. Compared to Mn(II) and Zn(II), the biochar exhibited highly selective Cu(II) adsorption. The adsorption kinetics of all three metal ions followed the pseudo-second-order kinetic equation. The isotherm data demonstrated the Langmuir model fit for Zn(II), Mn(II) and Cu(II). The results showed that the chemical adsorption of single molecules was the main heavy metal removal mechanism. The maximum adsorption capacities (mg·g−1) were ranked as Cu(II) (134.88) > Mn(II) (109.10) > Zn(II) (108.10)) by the single-metal adsorption isotherms at 298 K. Moreover, characterization analysis was performed using Fourier transform infrared spectroscopy, the Brunauer-Emmett-Teller method, scanning electron microscopy with energy-dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results revealed that ion exchange was likely crucial in Mn(II) and Zn(II) removal, while C-O, O-H and C = O possibly were key to Cu(II) removal by complexing or other reactions.
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