RESUMO
Layered double hydroxides (LDHs) have garnered significant attention from researchers in the field of adsorption due to their unique laminated structures and ion exchange properties. LDHs with various anion intercalation showed different adsorption effects on adsorbing ions, but the corresponding adsorption mechanisms are ambiguous. In this study, three types of NiAl-LDHs were synthesized, utilizing NO3-, CO32-, or Cl- as the interlayer anions. Batch tests were conducted to study their adsorption performances for Br-. Among them, the LDH with a NO3- intercalation layer exhibited the highest adsorption capacity for Br-, reaching up to 1.40 mmol g-1. The adsorption kinetics, mechanism, and renewability of these NiAl-LDHs were systematically compared. As a result, the type of Br- adsorption by all three materials was single molecular layer chemisorption. Moreover, the thermodynamic results of adsorption suggested that the adsorption of Br- was a spontaneous exothermic process. X-ray photoelectron spectroscopy, X-ray diffraction, and point of zero charge analysis collectively indicated that the adsorption of Br- by LDHs primarily occurred through interlayer ion exchange and electrostatic interactions. Structural characterizations of the adsorbents revealed that Br- entered the interlayers of the three LDHs, causing varying degrees of reduction in the interlayer spacing. Density functional theory calculations indicated that the interlayer binding energy of LDH with NO3- intercalation was the lowest, thereby making it more susceptible NO3- to be exchanged with Br-. Finally, the stability of the NiAl-LDHs was studied. The NiAl-LDHs retains a high removal efficiency of Br- even after 5 cycles of adsorption and desorption.
RESUMO
Rubidium (Rb) and cesium (Cs) have important applications in highly technical fields. Salt lakes contain huge reserves of Rb and Cs with industrial significance, which can be utilized after extraction. In this study, a composite magnetic adsorbent (Fe3O4@ZIF-8@AMP, AMP = ammonium phosphomolybdate) was prepared and its adsorption properties for Rb+ and Cs+ were studied in simulated and practical brine. The structure of the adsorbent was characterized by SEM, XRD, N2 adsorption-desorption, FT-IR, and vibrating sample magnetometer (VSM). The adsorbent had good adsorption affinity for Rb+ and Cs+. The Langmuir model and pseudo-second-order dynamics described the adsorbing isotherm and kinetic dates, respectively. The adsorption capacity and adsorption rate of Fe3O4@ZIF-8@AMP were increased by 1.86- and 2.5-fold compared with those of powdered crystal AMP, owing to the large specific surface area and high dispersibility of the adsorbent in the solution. The adsorbent was rapidly separated from the solution within 17 s using an applied magnetic field owing to the good magnetic properties. The composite adsorbent selectively adsorbed Rb+ and Cs+ from the practical brine even in the presence of a large number of coexisting ions. The promising adsorbent can be used to extract Rb+ and Cs+ from aqueous solutions.
RESUMO
Carcinoembryonic antigen (CEA) is regarded as a promising broad spectrum tumor biomarker for clinical diagnosis, progression, and prognosis. Surface plasmon resonance imaging (SPRi) was considered as one of the powerful tools for immunoassay with advantages of label-free, real-time detection with high-throughput. Herein, wavy gold-silver alloy nanoplates functionalized with anti-CEA antibodies providing high protein loading capacity and high mass are used as signal enhancers for CEA detection through SPRi sandwich assay. The present method exhibits a dynamic range for CEA determination from 0.1 to 312.5 ng mL-1 and a detection limit of 0.55 ng mL-1, well below normal physiological levels. This biosensing approach demonstrates the advantages of wavy gold-silver alloy nanoplates compared to conventional gold nanoparticles as a signal amplifier to enhance the SPRi signal, which is expected to become a new prospect for detection of cancer markers in biomedical research and clinical diagnosis.