Liu Zhe-Nan,Liu Lv-Cheng,Xue Jin-Peng,Li Shi-Gang,Li Xing
In this work, we employed L-methionine (L-M) as the functionalized reagent of AuNPs for the colorimetric and UV–vis dual-mode detection of As 3+ , Cd 2+ , and Hg 2+ ions with excellent selectivity and anti-interference. After adding the target ions, the functionalized AuNPs can be cross-linked together due to the As 3+ /Cd 2+ /Hg 2+ ions reacting with amino N, carbonyl or hydroxyl O of L-methionine to form the coordination bonds, resulting in the aggregation of functionalized AuNPs and cause the different red-shifts of the SPR absorption peak and color changes of functionalized AuNPs solutions. The LODs of the colorimetric sensor are 10 ppb/13 ppb/4 ppb by naked eyes and 2.35 ppb/1.68 ppb/0.32 ppb by UV–vis spectroscopy with good linear relationships between the absorbance ratios (A 633nm /A 519nm , A 645nm /A 519nm and A 665nm /A 519nm ) and As 3+ , Cd 2+ and Hg 2+ concentrations, which can be successfully applied to sense and detect As 3+ /Cd 2+ /Hg 2+ pollutants in tap water, pond water, well water, and other domestic water sources. Graphical Abstract
In this study, iron oxide (Fe3O4) was coated with ZrO2, and doped with three rare earth elements((Y/La/Ce), and a multi-staged rare earth doped zirconia adsorbent was prepared by using uniform design U14, Response Surface methodology, and orthogonal design, to remove As3+and As5+from the aqueous solution. Based on the results of TEM, EDS, XRD, FTIR, and N2-adsorption desorption test, the best molar ratio of Fe3O4:TMAOH:Zirconium butoxide:Y:La:Ce was selected as 1:12:11:1:0.02:0.08. The specific surface area and porosity was 263 m2/g, and 0.156 cm3/g, respectively. The isothermal curves and fitting equation parameters show that Langmuir model, and Redlich Peterson model fitted well. As per calculations of the Langmuir model, the highest adsorption capacities for As3+and As5+ions were recorded as 68.33 mg/g, 84.23 mg/g, respectively. The fitting curves and equations of the kinetic models favors the quasi second order kinetic model. Material regeneration was very effective, and even in the last cycle the regeneration capacities of both As3+and As5+were 75.15%, and 77.59%, respectively. Adsorption and regeneration results suggest that adsorbent has easy synthesis method, and reusable, so it can be used as a potential adsorbent for the removal of arsenic from aqueous solution.Keywords:magnetic Fe3O4;uniform design;surface response methodology;multi-staged doping;arsenic (III & V) removal
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