UV-visible Spectroscopy Was Used To Study The Interaction Of Zinc, Nickel Ions And Dissolved Organic Matter In Water Environment

In this thesis, differential absorbance spectra and differential log- transformed absorbance spectra were used to study DOM binding of zinc ion and nickel ion at varying conditions, as well as competitive binding of calcium ion, megnesium ion and zinc ion, nickel ion, and competitive binding of zinc ion and nickel ion at pH 6.0 and ionic strength 0.01 mol L-1.The binding of zinc ion and DOM, nickel ion and DOM in varying systems, as well as the competition between calcium ion, megnesium ion and zinc ion, nickel ion for the binding sites in DOM and competitive binding of zinc ion and nickel ion for the binding sites in DOM were tracked by examining the intensity and shapes of the differential absorbance spectra generated for the Zn²⁺- DOM, Ca²⁺- Zn²⁺- DOM, Mg²⁺- Zn²⁺- DOM, Ca²⁺- Ni²⁺- DOM, Mg²⁺- Ni²⁺-DOM, Zn²⁺- Ni²⁺- DOM systems, or by examining the intensity and shapes of the differential log- transformed absorbance spectra generated for the Ni²⁺- DOM system. The extent of metal binding by DOM was quantified by calculating the changes of log- transformed absorbance spectra slopes（denote as DS350- 400） in the range of wavelength 350 nm to 400 nm and by comparing the data with predictions made using the NICA- Donnan Model. The results was followed:1) Compared the characteristic peaks of the Zn- differential absorbance spectra of DOM and Ni- differential absorbance spectra of DOM with pH- differential spectra of DOM at the same condition, the effect showed that the location of the features was very close to that of the peaks seen in the pH- differential spectra of DOM. Therefore, the conclusion can be obtained that the binding of Zn²⁺ and Ni²⁺ by DOM was accompanied by the replacement of protons bound by carboxylic and phenolic functional groups.2) Compared the locations, intensities and shapes of the characteristic peaks of Zn-differential spectras of DOM at varying pHs, ionic strengths, we can know the intensities of Zn- differential spectras of DOM increased with the increasing of pHs, ionic strengths. The characteristic peaks of these were particularly apparent in alkaline conditions.3) Study the effects of pHs and ionic strengths on Ni- differential log- transformed absorbance spectra of DOM, it can be found that the intensities of Ni- differential log-transformed absorbance of SRHA increased with the increasing of pHs, Ni- differential log-transformed absorbance of SRFA increased with the increasing of pHs in acid condition, but decreased with increasing of increased with the increasing of pHs in alkaline condition, Ni-differential log- transformed absorbance of DOM decreased with increasing of ionic strengths, however, location and shapes of the characteristic peaks without changing, there were no characteristic peaks found at low and high pH, the strongest peak emerged at 400 nm in the range of pH 5,0 to 10.0.4) Study the effects of Ca²⁺ and Mg²⁺ on the locations, intensities and shapes of the characteristic peaks of Zn- differential spectras of DOM and Ni- differential spectras of DOM. It can be found Ca²⁺, Mg²⁺ just reduced intensities of Zn- differential absorbance spectra of DOM and Ni- differential absorbance spectra of DOM, rather than affect the locations and shapes. The stronger impact will emerged with higher concentration of Ca²⁺,Mg²⁺.5) Compared locations, intensities and shapes of the characteristic peaks of Zn-differential spectras of SRHA with or without Ni²⁺ and Ni- differential spectras of SRHA with or without Zn²⁺, the co- existence of Zn²⁺ and Ni²⁺ would change the locations, and intensities of Zn- differential spectras and Ni- differential spectras, an assumption was made that the binding of Zn²⁺ and Ni²⁺ onto DOM was competed for the same sites of carboxylic and phenolic functional groups in DOM. Detailed reasons need more study.6) The correlations between DS350- 400 and the datas with predictions of using the NICA- Donnan Model in all the Men+- DOM systems at varying conditions, we can know that the DS350- 400 of Men+- DOM in a wide range of pH values and ionic strength values, as well as varying Men+ concentration in the work were strongly correlated with the concentration of DOM- bound Zn²⁺ and Ni²⁺ at Zn²⁺ concentration from 0.0 mol L-1 to 7.4′ 10- 6 mol L-1 or at Ni²⁺ concentration from 0.0 mol L-1 to 8.4′ 10- 6 mol L-1, Which made quantify the extent of metal binding by DOM become possible.