The Protein Adsorption On The Surfaces Of Minerals/Water

The protein adsorption on the surfaces of minerals/water in environment is an important process, which affects many proteinic properties such as concentration, migration, transformation, bioavailability and biological toxicity. On the other hand, protein adsorption also affects the physicochemical characteristics of mineral particles. So it has great significance in environmental science and ecology.Some kinds of Mn oxides and Fe oxides with different structure were prepared used by chemical method. Using the bovine serum albumin and lysozyme as model protein, we studied the protein adsorption on surfaces of five kinds of minerals, i.e.,α-MnO₂,δ-MnO₂,γ-MnOOH,α-Fe₂O₃ andα-FeOOH. FTIR and XRD were also used to investigate experimental samples. We hope to supply some theory evidence on forecasting migration and transformation of proteins in natural environments. The main results are illustrated as follows:1. Made five kinds of experimental minertals by chemical method. The results showed that the diffraction peaks of prepared minerals, i.e.,α-Mn02,δ-Mn02 andγ-MnOOH, accorded with standard samples, but their crystal degree was not ideal. Particles ofα-MnO₂ andγ-MnOOH were acicular crystal, which specific area of BET was 94.22 m2/g and 36.34 m2/g, respectively; particle ofδ-MnO₂ was global with specific area of BET of 94.22 m2/g; The particles ofα-Fe₂O₃ andα-FeOOH have narrow and sharp peaks of XRD, suggesting a better crystal.α-Fe₂O₃ was global with specific area of BET of 19 m2/g, andα-FeOOH was fusiform with specific area of BET of 80 m2/g.2. Adsorption was investigated. The results showed that the BSA /LSZ adsorption onto the experimental minerals,α-Mn02,δ-Mn02,γ-MnOOH,α-Fe₂O₃ andα-FeOOH, was affected differently by pH value.3. Different ions strength had different effect on BSA/LSZ adsorption on the experimental minerals. With increasing NaCl concentration, the percentages of BSA adsorption on many surfaces of minerals includingα-MnO₂,δ-MnO₂,α-Fe₂O₃ andα-FeOOH decreased, which was as the same as the case of LSZ onα-Fe₂O₃, however, the percentages of LSZ adsorption on theα-MnO₂ andα-FeOOH increased. Although the percentage of BSA/LSZ adsorption onγ-MnOOH increased when the NaCl concentration was 0.03mol/L, the protein percentages was equal to that when the NaCl concentration was 0.2mol/L, to which case the LSZ adsorption onδ-MnO₂ also belonged. Different kinds of ions had different effect on BSA/LSZ adsorption on the tested minerals. Both Ca2+ and Mg2+ increased BSA adsorption on the minerals, except on the surface of Fe₂O₃.They also improved LSZ adsorption onγ-MnOOH andα-Fe₂O₃, but decreased LSZ adsorption onδ-MnO₂ andα-FeOOH. Na+,Ca2+ and Mg2+ had the same effect on LSZ adsorption onα-MnO₂.4. BSA/LSZ adsorption was highly irreversible, except BSA dsorption from the surface ofα-FeOOH.5. The adsorption equilibrium of BSA/LSZ on the experimental minerals belonged to L type, except that of LSZ on theα-Fe₂O₃ andα-FeOOH which was fit to C type. Langmuir and Frendlich equation were used to fit the experimental data. The results showed that the Langmuir equation predicted well the BSA adsorption on theα-MnO₂,δ-MnO₂,γ-MnOOH andα-Fe₂O₃, and was also fit well to LSZ adsorption onα-MnO₂ andγ-MnOOH. Frendlich equation accorded with LSZ adsorption onα-Fe₂O₃ andα-FeOOH.6. The results of XRD suggested that BSA molecules was bound to the external surface and the edges of theα-MnO₂ andδ-MnO₂, and could not intercalate the layers of minerals.7. The results of FTIR showed that BSA/LSZ was adsorbed to theα-MnO₂ and the structure of adsorbed BSA changed after adsorption, which led to the increasing of entropy.