Study On The Adsorption-desorption Of Triclosan On Polyhydroxybutyrate Microplastics

In recent years,the environmental effects of microplastics and triclosan(TCS)have attracted extensive attention from researchers.However,there are still not many studies on the combined pollution of microplastics and TCS,and the scope of research is still not broad enough.At the same time,biodegradable plastics are increasingly being used to address plastic pollution.However,there has been little research on the ecological risks of biodegradable microplastics.Therefore,this paper hope to further study the adsorption-desorption of triclosan on biodegradable microplastics to better understand the environmental risks of biodegradable microplastics.The conclusions of this paper are as follows:(1)In order to study the carrier effect of biodegradable microplastics to TCS,the adsorption and desorption processes of triclosan on a kind of biodegradable plastics-polyhydroxybutyrate(PHB)were investigated and also compared with one conventional plastic type-polyethylene(PE).The adsorption kinetics in ultrapure water showed that the adsorption rate and adsorption equilibrium capacity of TCS on PHB microplastics were significantly higher than that of PE microplastics and activated carbon.The study of adsorption and desorption models showed that physical adsorption,heterogeneous surface,and distribution were the important factors for TCS adsorption of PHB and PE microplastics.The results of desorption hysteretic indexes showed that TCS was easily desorbed from PHB and PE microplastics under physiological conditions and real seawater environment.(2)In order to study the influencing factors for TCS adsorption of biodegradable microplastics,the influences of microplastics characteristics(plastic size,plastic shape,aging degree)and the chemical properties of the solution(p H,salinity,coexisting heavy metals,dissolved organic matter)on the adsorption behavior of PHB microplastics were investigated in this study.The results showed that the particle size and shape of PHB microplastics had a significant influence on the adsorption behavior due to their specific surface area.The smaller the particle size of PHB microplastics,the larger its specific surface area,the stronger the adsorption capacity.After aging,the adsorption capacity of microplastics was also significantly enhanced.As for the influences of the chemical properties of the solution,the adsorption capacity of TCS on PHB microplastics was reduced by the solution at high p H value,which was related to the electrostatic interaction between PHB microplastics and TCS at different p H values.In addition,solution salinity,coexistence of heavy metals and dissolved organic matter had little influence on the adsorption behavior of PHB microplastics,indicating that PHB microplastics could accumulate TCS in various water environments.(3)In order to study the migration behavior of TCS in the real seawater environment,the distribution behavior of TCS among seawater,PHB and PE microplastics was investigated in this study.The adsorption kinetics of PHB and PE microplastics in seawater showed that the adsorption rate and adsorption equilibrium quantity of TCS on PHB microplastics were also significantly higher than that of PE microplastics.In addition,the adsorption capacity of TCS on PHB microplastics in seawater was basically the same as that in ultrapure water,while the adsorption capacity of TCS on PE microplastics in seawater was significantly weaker than that in ultrapure water.The distribution experiment indicated that PHB microplastics could significantly reduce the adsorption capacity of TCS on PE microplastics in seawater environment.Moreover,TCS was the most distributed in PHB microplastics,followed by seawater and PE microplastics.In addition,PHB microplastics could take away 64.3% of the total TCS that had been adsorbed on PE microplastics,resulting in TCS redistribution.