Influence Of Ultrasonic Modification Method On Removal Efficiency Of Algae By Clay And Its Mechanism

In recent years,harmful algal blooms have occurred frequently and have caused serious damage to the coastal ecosystem,fisheries,aquaculture,and the landscape.It has become a worldwide maritime disaster.The modified clay method is an effective method for the emergency treatment of harmful algal blooms.Based on the previous researches on modified clays,the ultrasound was used to modify the clay,to further increase the flocculation efficiency of clay on algal cells and reduce the amount of clay.We explored the algae removal mechanism of ultrasonic modified clay,which provided a reference for further enhancing the removal ability of clay.The main results are as follows(1)Analyzing the algal removal efficiency of clay under different ultrasonic conditions,we found that ultrasonic treatment can effectively improve the removal efficiency of clay,and the effect of ultrasonic treatment is affected by the change of ultrasonic time and ultrasonic power.The increase range of different clays was different.When the Prorocentrum donghaiense was used as the experimental organism,the removal efficiency of bentonite was the most obvious,followed by montmorillonite,followed by kaolin,the PAC-MC and AC-MC had the lowest increase.The magnitude of modified clay is lower than that of the clay,mainly because the removal efficiency of modified clay has reached a relatively high level.In our experiment time,the longer the ultrasonic treatment time is,the better the modification effect is,and the ultrasonic treatment time can be set to 15 min-20 min.With the increase of ultrasonic power,the removal rate generally shows a trend of rising first and then decreasing.The ultrasonic treatment power can be set to 360 W.(2)Analyzing the particle properties of clay under different ultrasonic conditions,we found that ultrasonic treatment can reduce the particle size of the clay and make the clay particles more uniform.The degree of particle size change is affected by the ultrasonic time and ultrasonic power.Different clays have different particle size changes after ultrasonic treatment,which is caused by different clay materials and different particle sizes.Ultrasonic treatment has a significant effect on the sedimentation rate of clay.The sedimentation rate of ultrasonic kaolin,PAC-MC and AC-MC decreased,the sedimentation rate of ultrasonic montmorillonite increased first and then decreased,and the sedimentation rate of ultrasonic bentonite significantly increased.Ultrasonic treatment can lead to changes in clay surface potential,but its effect is affected by many factors,such as the type of clay,the type and concentration of ions in the solution and whether the clay is modified.Ultrasonic treatment also affects the pH of the clay suspension,and changes in pH are also affected by the above factors.(3)Analyzing the correlation between the removal efficiency of algae and the particles properties of the clay,we found that the increase of clay removal efficiency after ultrasonic treatment is mainly affected by the decrease of clay particle size.Ultrasonic treatment can affect the Zeta potential and pH of clay suspensions,which may not have a positive effect on clay removal efficiency.The longer the ultrasonic treatment time is,the more obvious the effect of modification on the five clays are.In general,ultrasonic time is linear with particle size,sedimentation rate and other particle properties.