Study On Adsorption Efficiencies And Mechanisms Of Typical Heavy Metals On Microplastics In Water

Due to the characteristics of small particle size,large specific surface area and porous structure,microplastics are easy to adsorb pollutants in water,which become the transport carrier of pollutants in the environment and have a significant impact on the water environment.Manganese and lead,a kind of common heavy metal pollutants in water sources,can be combined with microplastics at lower concentrations to cause compound pollution,and the heavy metal pollutants adsorbed on microplastics will have a greater impact on human health along with the water flowing.Therefore,to carry out the microplastic for heavy metal manganese(Ⅱ)and lead(Ⅱ)adsorption behavior research,a research on the microplastic water heavy metal manganese(Ⅱ)and lead(Ⅱ)change over time in different stage of the adsorption capacity,adsorption and combining different adsorption equation model fitting and analysis of various experimental conditions,the micro plastic for heavy metal manganese(Ⅱ)and lead(Ⅱ)adsorption process,discussed its adsorption efficiency and mechanism,and micro plastic compound pollutants to explore heavy metal pollutants in the transition and transform rule of water treatment process is of great significance.The results showed that adsorption capacity of microplastics to manganese(Ⅱ)was polystyrene(PS)> polypropylene(PP)> polyethylene(PE).The effect of particle size on adsorption ability of manganese(Ⅱ)was showed that the smaller the particle size,the larger the adsorption capacity and the adsorption rate.The increase of humic acid concentration led to the decrease of adsorption capacity of microplastics to manganese(Ⅱ).Adsorption capacity of PS particles to manganese(Ⅱ)increased with the increase of p H value.The temperature increase had a significant effect on the rapid adsorption stage.At288 K,the adsorption capacity and average adsorption rate of microplastics for manganese(Ⅱ)were the lowest,and at 308 K,the adsorption capacity and average adsorption rate of microplastics to manganese(Ⅱ)were the highest The increase of the initial concentration of manganese(Ⅱ)ions increased the contact probability between microplastic particles and metal ions,and could increase the adsorption capacity of PS particles to manganese(Ⅱ).The experimental results showed that adsorption capacity of microplastics to lead(Ⅱ)was polystyrene(PS)> polypropylene(PP)> polyethylene(PE).The ability of particle size to adsorb lead(Ⅱ)was shown as the smaller the particle size,the larger the adsorption capacity and the larger the adsorption rate.The increase of humic acid concentration will promote the adsorption of lead(Ⅱ)on microplastics.Adsorption capacity of PS particles to lead(Ⅱ)increased with the increase of p H value.The temperature increase will have a significant impact on the rapid adsorption stage.At 288 K,the adsorption capacity and average adsorption rate of microplastics for lead(Ⅱ)were the lowest,while at308 K,the adsorption capacity and average adsorption rate of microplastics to lead(Ⅱ)were the highest.The increase of the initial concentration of lead(Ⅱ)ions will increase the contact probability between microplastic particles and metal ions,and can increase the adsorption capacity of PS particles to lead(Ⅱ).Compared with the experimental results of adsorption of manganese(Ⅱ)on microplastics,adsorption capacity of microplastics to lead(Ⅱ)can be improved with the increase of humic acid concentration,which was due to dominant hydrophobicity of humic acid in the process of manganese ion adsorption on microplastics,while the negative electricity of humic acid plays a major role in the process of lead(Ⅱ)on PS particles.The adsorption kinetics and adsorption isothermal model were used to fit the experimental data of adsorption of manganese(Ⅱ)and lead(Ⅱ)on·microplastics.According to the results,it could be concluded that adsorption of manganese(Ⅱ)and lead(Ⅱ)on microplastics and their particle sizes all conformed to the pseudo-second-order kinetic equation.The diffusion of particle diameter was the main control step in adsorption of manganese(Ⅱ)and lead(Ⅱ)on PS particles.Adsorption to manganese(Ⅱ)and lead(Ⅱ)on PS particles under different water sample conditions(humic acid concentration and p H value)conformed to pseudo-second-order kinetics,and the main control step of adsorption was microplastics surface adsorption,and the adsorption capacity would be increased with the increase of temperature.PS particles absorbed manganese(Ⅱ)and lead(Ⅱ)endothermically.The adsorption isotherms of PS particles,manganese(Ⅱ)and lead(Ⅱ)at different initial ion concentrations were different.With increasing temperature,the adsorption of manganese(Ⅱ)on PS particles at different initial ion concentrations was more conformed to Langmuir model,which indicated that the adsorption of manganese(Ⅱ)on microplastics was monolayer adsorption with fixed adsorption sites.The adsorption of lead(Ⅱ)on PS particles at different initial ion concentrations with the increase of temperature conformed to Freundlich equation,which indicated that the adsorption of lead(Ⅱ)on microplastics conformed to heterogeneous adsorption.The functional groups of some elements in microplastics might coordinate with metal ions,resulting in changes in element content.Electrostatic adsorption and complexation reactions between functional groups and manganese(Ⅱ)and lead(Ⅱ)were the dominant mechanisms in the adsorption process.