1.
Adsorption and oxidation of elemental mercury from coal-fired flue gas over activated coke loaded with Mn-Ni oxides.
Zeng, Q, Li, C, Li, S, Liu, M, Du, X, Gao, L, Zhai, Y
Environmental science and pollution research international. 2019;(15):15420-15435
Abstract
A series of Mn-Ni/AC (AC, activated coke) catalysts were synthesized by the impregnation method for the removal of elemental mercury (Hg0) from simulated flue gas. The samples were characterized by BET, ICP-OES, SEM, XRD, XPS, H2-TPR, FT-IR, and TGA. Mn6Ni0.75/AC exhibited optimal removal efficiency of 96.6% in the condition of 6% O2 and balanced in N2 at 150 °C. The experimental results showed that both O2 and NO facilitated Hg0 removal. SO2 could restrain the Hg0 removal in the absence of O2, while the inhibitory effect of SO2 was weakened with the aid of 6% O2. In addition, H2O exhibited a slightly negative influence on Hg0 removal. The characterization of the samples indicated that Mn6Ni0.75/AC possessed larger specific surface area, higher dispersion of metal oxides, and stronger redox ability. In the meantime, the results of XPS and FT-IR demonstrated that the lattice oxygen and chemisorbed oxygen made contributions to Hg0 removal and the consumed oxygen could be compensated by the redox cycle of metal oxides and gas-phase O2. Meanwhile, the mechanisms of Hg0 removal were proposed based on the above studies.
2.
Enhancing selectivity in spectrofluorimetric determination of tryptophan by using graphene oxide nanosheets.
Othman, AM, Li, S, Leblanc, RM
Analytica chimica acta. 2013;:226-32
Abstract
Reaction of formaldehyde with amino acids followed by oxidation with hydrogen peroxide to produce a fluorophore Norharman product is well known and was used for the spectrofluorimetric determination of l-tryptophan (Trp). This study aimed to use graphene oxide (GO) to enhance the selectivity and sensitivity of Trp in presence of other amino acids and possible interfering compounds. Different parameters such as pH, temperature, incubation time, and concentrations of formaldehyde, H2O2 and GO were studied to optimize the condition of determination. Experimental data showed that the maximum fluorescence intensity was achieved in pH 7.0-9.0 phosphate buffer mixed with 7-10% (v/v) formaldehyde and 1-2% (v/v) H2O2 as oxidizing agent at 60°C for 1h. On the basis of calibration curve of various concentrations of Trp in the presence of 20 μg mL(-1) GO, the lower limit of detection (LOD) of Trp was determined as 0.092 nmol mL(-1) and the lower limit of quantification (LOQ) was 0.3 nmol mL(-1). The selectivity of Trp in presence of other amino acids and possible interfering compounds were studied with and without GO. The data obtained after inner filter effect corrections revealed that the selectivity of Trp in presence of amino acids and other possible interfering agents was improved in the range of 76-96%, compared with that in absence of GO. The enhancement of selectivity in the presence of GO indicates that the Trp and other amino acid and possible interfering compounds were adsorbed by GO, and the selective uptaking of Trp-by the reaction with formaldehyde followed by oxidation with H2O2 at 60°C with high selectivity and sensitivity was achieved successfully.