## 3 Results and Discussions
### Effect of Operating Variables
#### 3.2.3 Effect of Temperature and Sediment Solid-Liquid Ratio on Mn(II) Sorption  
Temperature is an important factor affecting the stability constants of heavy metal conditions. Figure 4 show the sorption capacity and removal rate of DX on heavy metal Mn(II) at different temperature conditions (25 \({}^{\circ}\)C, 30 \({}^{\circ}\)C and 40 \({}^{\circ}\)C). The results show that the increase of temperature is favorable to promote the sorption of heavy metal Mn(II) by sediment DX. Both the sorption amount and removal rate of Mn(II) reached the maximum at the reaction temperature of 40 \({}^{\circ}\)C. When the initial dosage was g\(\cdot\)L\({}^{-1}\), the sorption and removal rates of Mn(II) at 25 \({}^{\circ}\)C were 7.07 mg\(\cdot\)g\({}^{-1}\) and 50.16%, respectively, while they were increased by 1.30 and 1.26 times at 40 \({}^{\circ}\)C. Temperature affects the sorption process in two main ways. From the kinetic point of view, the increase in temperature contributes to the decrease in solution viscosity, which accelerates the diffusion rate of adsorbent molecules through the external boundary layer and the internal pores of the adsorbent particles. On the other hand, the enhancement in sorption capacity of the adsorbent with increasing temperature is facilitated by the rise in Mn(II) mobility, which makes the diffusing ions less hindered [37]. Changes in soil properties (pore size and carbon activity) by elevated temperature may also be important in promoting heavy metal sorption capacity and efficiency [38].  
The amount of sediment dosing directly determined the number of total sorption sites and the amount of cation exchange in the solution. The effect of sediment solid-liquid ratio was adjusted to 4-12 g\(\cdot\)L\({}^{-1}\) by varying the DX dosage, and its effect on the sorption of Mn(II) was investigated (Figure 4). With the increase of sediment dosage, the removal of Mn(II) increased significantly from 50.16-62.47% to 95.37-98.93%. However, the sorption of Mn(II) basically reached saturation when the sediment dosage was 10 g\(\cdot\)L\({}^{-1}\). The removal rate of Mn(II) from the solution by DX was more than 95%, and almost no longer changed significantly with the increase of the solid-liquid ratio. Nevertheless, the sorption of Mn(II) showed a linear decrease with an increasing solid-liquid ratio. At 25 \({}^{\circ}\)C, the sorption of Mn(II) decreased from 7.07 mg\(\cdot\)g\({}^{-1}\) to 4.70 mg\(\cdot\)g\({}^{-1}\) by the increasing solid-liquid ratio. The elevated adsorbent concentration contributes to the increase of surface-active exchange  
Figure 3: Effect of initial concentration of solution on the sorption effect of manganese.  
sorption sites with total surface cation exchange, which promotes the sorption of DX on Mn(II). Due to the interference caused by the interaction between the active sites of the adsorbents, the solute sorption per unit weight of adsorbent decreases with increasing adsorbent concentration [39]. It is noteworthy that the increase in solid-liquid ratio did not significantly improve the removal rate when Mn(II) was largely removed from the solution, but the sorption amount continued to decrease. When the sediment dosing was increased from 10 g\(\cdot\)L\({}^{-1}\) to 12 g\(\cdot\)L\({}^{-1}\) at 40 \({}^{\circ}\)C, the removal rate basically did not change significantly, but the sorption amount decreased significantly from 5.74 mg\(\cdot\)g\({}^{-1}\) to 4.87 mg\(\cdot\)g\({}^{-1}\), which is consistent with the results of [PERSON] and [PERSON] et al. [40; 41].