The removal of toxic Cr(VI) is a hot topic in the environmental remediation field. In this work, a Ti-based metal− organic framework (MOF) (MIL-125(Ti)-NH 2 ) was successfully functionalized by introducing amidoxime groups for the first time. The functionalized material (MIL-125(Ti)-AO) exhibited excellent Cr(VI) adsorption performance with a maximum adsorption capacity of 271 mg•g −1 according to Langmuir fitting. More importantly, during the adsorption process, Cr(VI) could be simultaneously reduced to less toxic Cr(III) species, and the residual concentration of chromium in the treated water was below the drinking water limit (0.05 mg•L −1 ) recommended by WHO. The effects of initial pH, contact time, and the initial concentration of Cr(VI) and the presence of competitive ions on the Cr(VI) adsorption performance of MIL-125(Ti)-AO were systematically investigated. The excellent Cr(VI) removal performance of MIL-125(Ti)-AO was attributed to the synergistic effects of simultaneous adsorption of Cr(VI) and Cr(III) by a [Ti−O] bond when Cr(VI) was reduced to Cr(III) by amidoxime groups.
It is important to investigate the different impact factors on the establishment of investment portfolio. In order to maximize the profit of a portfolio, this research selects six stocks: Adobe (ADBE), International Business Machines Corp (IBM), Bank of America Corporation (BAC), Citigroup (C), Southwest Airlines Co (LUV) and Alaska Air Group Inc. (ALK) as an empirical case to conduct investment decision. This research compares different results of two models (Markowitz model and Index Model) by analyzing the data of the portfolio such as minimum risk portfolio and maximum Sharpe Ratio portfolio. This research finds that the Markowitz Model is more appropriate to the portfolio establishment, which is presented by its sharper efficient frontier. Under all the conditions the study considered, the Markowitz Model always gets more returns than the Index Model when the risk increases by the same amount. Therefore, this research concludes that the Markowitz Model is more suitable for this portfolio. By analyzing the portfolio in two models, the study has found a better model for this portfolio, thus make more rational investments.
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