Study On The Efficiency And Mechanism Of Surface Modified Microbubble Enhanced Co-coagulation-DAF

Colloidal particles,algae cells and organic pollutants in surface water source water are the primary solutions in the field of water purification.The dissolved air floatation process(DAF)is one of the most basic separation processes in water treatment.It has high algae and high organic matter water treatment.Significant advantages.In recent years,air flotation technology has made considerable progress abroad.Due to the large influence of pre-coagulation effect and poor adaptability,domestic research has lagged behind.In order to enhance the applicability of the air flotation process,this study added the surface modification technology of microbubbles on the basis of the previous research on the co-coagulation-DAF(CCDAF),and developed the bubble surface positive modification co-coagulationDAF(Posi-CCDAF).A micro-bubble micro-observation system was independently built to study the effect of surface modifiers on micro-bubble characteristics.The feasibility study of Posi-CCDAF process was carried out,and the optimal working parameters were put forward.The decontamination characteristics of the Posi-CCDAF process were investigated and the adhesion process of the chitosan modified bubbles to the floc particles and the scum morphology were observed.The interaction mechanism of colloidal particles.The microbubble characteristic test results show that the size of the microbubble produced by the air floatation device decreases with the increase of the dissolved gas pressure,and the diameter change is no longer obvious after 0.5 Mpa.The dissolved gas pressure of 0.5 Mpa is in line with the application conditions of the microbubble of copolymerized air float.When the CTAB concentration increases in the range of 0-10 mg / L,the diameter of the microbubbles decreases and the probability of adhesion and coalescence between the microbubbles decreases.When the cationic polymer is added,the average diameter of the microbubbles changes weakly.The polymer provides electrostatic and hydrophobic forces,and the coalescence between the microbubbles increases.Surfactants can slightly slow the rising speed of microbubbles,while the effect of cationic polymers can be ignored.The surface of the microbubbles without surface modification is negatively charged,with an average Zeta potential between-48 and-31 mV.The CTAB modified microbubbles have a maximum Zeta potential of 40 ± 5 mV,followed by PDADMAC of 38 ± 9 mV,and The microbubble modified by chitosan had a Zeta potential of only 20 ± 10 mV.Parameter optimization experiments show that CTAB has a poor effect,and the removal effect of chitosan as a microbubble surface modifier is better than that of coagulant,while PDADMAC is just the opposite.After the addition of CTS,the Zeta potential of the air floated out of the water did not rise significantly,and the scum characteristics showed that CTS entered the scum with microbubbles.When PDADMAC is used,the Zeta potential of the effluent rises significantly,which easily affects the subsequent process.Chitosan is environmentally friendly and has a low cost,and is more suitable as a microbubble surface modifier for the process.The PAFC dosage is 5mg / L,the chitosan dosage ratio is 0.4,and the pH of the dissolved gas reflux water is 5.The enhancement effect of the removal effect is the best.Affected by the cost,the optimal pH value of the dissolved gas reflux water is determined.Is 6.The process of removing particulate matter in water is mainly based on large size.Enhanced removal of humic and fulvic acids with high molecular weight and high hydrophobicity.It has a better strengthening effect for removing THMFP,TCM has the highest removal rate,and DBCM and BDCM have similar removal rates.The number of micro-bubbles adhered to the flocs formed by copolymerization of modified micro-bubbles is more and dense.The amino group of chitosan preferentially combines with the negatively charged macromolecular organic matter to form a large attachment network,which provides a bridging effect for the adhesion of the foam.After using chitosan,the surface of the generated flocs becomes "rough".According to the size of the chitosan molecules,electrostatic attraction is also the main mechanism of action to strengthen the adhesion of microbubbles and particles.