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Tham khảo tài liệu 'waste water treatment and reutilization part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Purification of Waste Water Using Alumina as Catalysts Support and as an Adsorbent 289 palladium adsorption decreased below that of alumina dissolution. The amount of PdCl42-on alumina is limited by the i strong electric forces of adsorbed species and ii dissolution of alumina. However it is clear that some amount of the adsorbed PdCl42- is detached together with Al3 during the dissolution process. Therefore it can be assumed that one important consequence of alumina dissolution in addition to the effect of ionic strength is the retardation of PdCl42- adsorption. Time I h Time I h Fig. 7. Time course of a proton consumption and b adsorption density of PdCl42- on alumina during the impregnation of y-Al2O3 with PdCl42- at pH 3.5 x and pH 4 . To find out whether the proton consumption is affected by PdCl42- adsorption the ratio between H cons. and Al3 sol. is analyzed in Table 1. From Table 1 it is clear that PdCl42-does not promote alumina dissolution because the rate between H cons. and Al3 sol. remained practically constant 4.2 regardless of whether PdCl42- was present or not in the solution. If PdCl42- would promote alumina dissolution the proton consumption should decrease significantly in comparison to the amount of Al3 formed. In practice only the rate of alumina dissolution was affected by PdCl42-. It is likely that one of the reasons for the retardation of PdCl42- adsorption is alumina dissolution. H cons. Al3 sol. experiment time h pH system 3.99 72 3.5 AI2O3 H 4.24 74 3.5 A12o3 H PdCl42- 4.23 70 4.0 A12o3 H 4.19 50.5 4.0 A12o3 H PdCl42- Table 1. Influence of PdCl42- on H cons. Al3 sol. ratio at pH 3.5 and 4 In the course of PdCl42- impregntion three types of simultaneous process could be analyzed I alumina dissolution II proton consumption and III adsorption density of PdCl42- on the surface of alumina. It was observed that some amount of support was mobilized in the liquid phase during impregnation. The amount of dissolved alumina depends on the pH of the
