| Dissolved Ozone Flotation has been used for many years in wastewater treatment,but many researchers have focused on the theory of dissolved ozone flotation,the reactor improvement,and the improvement of water purification,and due to the limitations of technical equipment,dissolved ozone flotation has not more microscopic exploration.So,based on the research about dissolved ozone flotation theory and technology,this study proposes a microscopic observation of the surface physicochemical properties of flocs and the mechanism of microbubbles action.In order to explore the relationship between the efficiency of water purification and the microbubble-flocs,we study the optimal conditions for the formation of microbubbles and the best form of microbubble-flocs after the addition of coagulants,and a microscopic observing system for dissolved ozone flotation was established.Bubbles,floc fluids and recorded in the form of images to evaluate and characterize multiphase mixing systems?water/floc/bubble systems?.Kaolin as a research system,polyaluminum chloride?PAC?as a coagulant,at a flow rate of0.1m3·h-1,residence time 30min,adjustment of pressure?0.30 MPa,0.40 MPa and 0.50 MPa?and recycle ratio?30%,40%and 50%?formed 9 kinds of working conditions by arranging and combining,observing airborne flocs and microbubbles under 9 working conditions and compare its morphological characteristics with the turbidity removal rate under the corresponding conditions to achieve the purpose of microscopic investigation of air flotation.The results show that within a certain limit,the microbubble size decreases as the dissolved pressure increases and the recycle ratio decreases.When the pressure is 0.40 MPa,the recycle ratio is 30%,and the dosage of coagulant is60 mg·L-1,the average particle size of the microbubbles is the smallest and the size distribution is uniform,and the rise of bubbles will not generate water flow.Large disturbance,the best combination of bubbles and flocs.The average particle size of airborne floe is the largest,the size distribution is between 0.45mm and 0.95mm,the two-dimensional fractal dimension is the smallest,the microbubble-flocs structure is loose and large,the turbidity removal rate is the highest,and the treatment effect is the best.In addition,the results also show that the influence of Zeta potential on airborne flocculation is different from that of traditional coagulation.In traditional coagulation,flocs are easily formed at the isoelectric point,and in the flotation reaction,the surface of the bubble is negatively charged.Therefore,when the Zeta potential is positive,it is more conducive to the formation of an optimal microbubble-flocs.When the Zeta potential is 17mV,the equilibrium contact angle reaches a maximum value,and the formed microbubble-flocs is the most ideal.Based on this,the polymer flocculant conditioning floc surface characteristics were added,and the combination of bubbles and flocs was enhanced. |
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