tailieunhanh - Ozone Reaction Kinetics for Water and Wastewater Systems - Chapter 10

Không đồng nhất xúc tác Ozonation Chất xúc tác là chất được sử dụng để đẩy nhanh tốc độ của các phản ứng hóa học khác nhau. Những phản ứng này thường gặp phải trong công nghiệp hóa chất, nơi nhiệt độ và áp suất cao được áp dụng. Những điều kiện này, đặc biệt là nhiệt độ, hành vi trên bề mặt của vật liệu nhất định (các oxit kim loại, than hoạt tính, zeolit , vv), sau khi hấp thụ các phân tử chất phản ứng, nâng cao tỷ lệ các phản ứng nhiều. Trong xử lý nước, phản ứng. | 10 Heterogeneous Catalytic Ozonation Catalysts are substances used to accelerate the rate of different chemical reactions. These reactions are typically those encountered in the chemical industry where high temperatures and pressure are applied. These conditions especially temperature act on the surface of certain materials metal oxides activated carbon zeolites etc. which after adsorption of reactant molecules improve the rate of numerous reactions. In water treatment the high reactivity of ozone and the active surface of some materials can also be used to increase the ozonation rate. In the mid-1990s in an attempt to improve the performance of advanced oxidation of water contaminants with the use of ozone numerous research studies focused on the combined application of ozone and solid catalysts. These systems constituted the catalytic ozonation of water At that time however catalytic ozonation was not a new process since the use of ozone and catalysts date back from the 3 In the first studies however attention was mainly paid to the use of transition metal salts such as nitrates sulfates etc. which are soluble in When dealing with catalytic ozonation one should distinguish the homogeneous HoCO and the heterogeneous HeCO processes depending on the water solubility of the catalyst. As far as the knowledge of this author is concerned however one of the first studies on this matter was by Hill4 5 who observed the homogeneous decomposition of ozone catalyzed by Co2 in acid media acetic acid or perchloric acid . He proposed a mechanism of reactions with the formation and participation of hydroxyl free radicals formed in a first step from the direct oxidation of Co2 2 k 37M 1min 1 2 O3 CO H2O----- ---- HO CoOh O2 O2 The fact that hydroxyl radicals were formed allowed the appearance of a new advanced oxidation technology. Nonetheless the first work on the catalytic ozonation of water pollutants seems to be due to Hewes and Davidson2 .