## 3 Results and Discussion
### Incubation Study  
The findings of the incubation study revealed a similar trend of removal of Cd and Pb by tested zeolite sediments. The highest removal efficiency of Cd was found in the LDH-N sediment, suggesting complete removal (\(\sim\)100%) after an 8-week incubation period, whereas for the NZ-N and HCl-N sediments, the removal efficiency of Cd after 8 weeks was 91.80% and 94.26%, respectively, and it reached 100% removal after the 16-week incubation period (Figure 8A). Similarly, LDH-N recorded the highest removal efficiency for Pb, suggesting 92.26% removal after 8 weeks of incubation and 100% removal after the 16-week incubation period, whereas HCl-N and NZ-N removed 89.56% and 87.20% Pb, respectively, after the 8-week incubation period and showed a 100% removal after the completion of the 16-week incubation period (Figure 8B). Additionally, during the incubation period, soil samples were taken at regular incubation times and were extracted with ammonium acetate (AA) extractant to assess the ability of sediments to hold and fix heavy metals in soil. Our findings indicate that all utilized sediments demonstrated credible potential in fixing and stabilizing heavy metals, and very low contents of heavy metals were extracted in the AA solution, while control soil treatment with no added sediments showed higher extracted concentrations of heavy metals than soil with added sediments (Figure 9A,B). It was found that extracted Cd contents were 88.4% higher in the control soil (CK) compared to its concentration in the best-performing NZ sediment (LDH-N), which recorded only 0.029 mg kg\({}^{-1}\) of Cd extracted after the first week of incubation. A trend of gradual decrease in the extracted quantity of Cd was noted, indicating the exhaustion of Cd contents in CK soil and the excellent ability of sediments to hold and fix Cd contents in active sites. At the end of the incubation period, CK soil still showed  
Figure 7: Kinetics of Cd (**A**,**C**) and Pb (**B**,**D**) adsorption and removal by natural and modified zeolite adsorbents. NZ-N, natural zeolite with nanoparticle size; LDH-N, LDH-zeolite with nanoparticle size; HCl-N, HCl-zeolite with nanoparticle size. 0.044 mg kg\({}^{-1}\) extractable Cd contents, while LDH-N sediment-treated soil showed zero extractable Cd contents after 8 weeks of incubation (Figure 9A). For the HCl-N and NZ-N treated soil samples, no AA extractable Cd contents were found in the soil after the 16 th week of incubation. In the same manner, the extraction of Pb with AA indicated the highest Pb quantity in CK soil samples and recorded 3.63 mg kg\({}^{-1}\) of AA extractable Pb contents at the first week of incubation. By the end of the 16 th week of incubation, the concentration of AA extractable Pb in the CK soil was decreased to 1.31 mg kg\({}^{-1}\). In contrast, the soil treated with LDH-N indicated a maximum decrease in Pb extractable contents (0.77 mg kg\({}^{-1}\)) after the first week of incubation. AA extractable Pb contents for soils treated with NZ-N (1.1 mg kg\({}^{-1}\)) and HCL-N (1.01 mg kg\({}^{-1}\)) were also found to be lower than that in the CK soil after the first week of incubation (Figure 9B). A similar trend of reduction in Pb extraction with AA was observed with time, with all tested sediments recording zero extractable Pb contents at the 16 th week of incubation. Overall, all tested sediments recorded excellent removal and metal stabilizing ability against CK soil, while among employed sediments, LDH-N showed significantly better performance in removing and fixing heavy metals in soil. The higher removal efficiency of LDH-N sediments clearly indicated its excellent ability to stabilize heavy metals, fixing heavy metals on its surface and making complexation with surface functional groups. The higher efficiency of LDH-N sediment for removal of heavy metals over other tested sediments could be due to the higher surface area (Table 4) and presence of additional surface functional groups [26]. In this regard, [PERSON] et al.