## 5 Factors Affecting the Adsorption of Microl plastics
### Effects of Solubility, Concentration and Dosage  
The different solubilities of pollutants produced different adsorption results. For example, the results of the adsorption experiment on chloromethane by plastic indicated that the adsorption amount of trichloromethane by plastic was greater than the adsorption amount of carbon tetrachloride, which is the reason for the solubility [85], and the adsorption of lead and cadmium in intertidal sediments by facial scrub beads [86].  
In the adsorption of 2,4,6-nitrotoluene by functionalized polystyrene nanospheres, the adsorption amount initially increased and then flattened because the high solubility of KH-570 obstructs the phosphorus-phosphorus accumulation interaction between the adsorbent and pollutant [87]. However, hydrophobic substances were more easily removed from an aqueous solution than hydrophilic substances, with different solubility and adsorption results [85].  
In different experiments, the concentration altered the effects on the adsorption process of microplastics. As in the adsorption of three triazole fungicides by polystyrene microplastics, the concentration promoted the adsorption capacity of polystyrene [50]. Polystyrene can enhance the migration of nonpolar (pyrene) and weakly polar (2,2,4,4-tetrabromodiphenyl) ethers) compounds in saturated soils. However, in the adsorption of 5-sodium disulfoisphthalic acid by acrylate polymer YWB-7 resin, the methanol content had a hindrance effect on the performance of the adsorbent [88].  
High levels of microplastics can absorb more pollutants. For example, with the increase in polystyrene nanofiber sorbent, the adsorption efficiency of cadmium and nickel ions can reach more than 90% [58]. The IRN-77 cation exchange resin for Co(II), Ni(II), and Cr(III), three kinds of ion adsorption efficiencies, is very high, and the increase in IRN-77 cation exchange resin dosage can reach 100% [89]. The same effect was observed with modified polyethyleneimine Cr(III) and Fe(III) adsorption [56].  
The adsorption of Co(II), Cr(III), and Ni(II) on IRN-77 cation exchange resin followed the same principle [61]. The adsorption efficiency of phenanthrene and its mono hydroxyl derivatives increased with the amount of adsorbent [90]. In addition, some reagents can also affect the adsorption efficiency of microplastics. For example, in the adsorption of 5-sodium disulfoisylphthalic acid by acrylate polymer YWB-7 resin, the amount of methanol can seriously hinder the efficiency of the adsorbent [88].  
On the other hand, the pore size of the adsorbent also followed the same principle, such as poly(ethylimide) adsorption of lead and mercury. The larger pore size of the adsorbent can provide better adsorption effect [57]. Thus, the difference in the amount of pollutants adsorbed by these plastics was due to the influence of solubility, concentration, and dosage on the adsorption performance of microplastics.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Adsorbent** & **Surface Area** & **Pollutants** & **Influencing Factors** & **Reference** \\ \hline polystyrene (MP\({}_{\text{S}}\)) & — & \
\begin{tabular}{c} nanometer oxide \\ (CeNPs) \\ \end{tabular} & heavy metals (HM) & [46] \\  & & &
\begin{tabular}{c} Sc(III), Y(III), La(III), \\ Fe(III), Al(III), Ga(III), \\ \end{tabular} & pH & [55] \\  & & & In(III) & pH, adsorbent dosage, \\  & & & & temperature \\