## 4 Conclusions  
In this study, phytoremediation enhanced by biodegradable chelating agents using _Taraxacum officinal_ and _Gazania_ for Cd and Zn was investigated. The amount of Cd uptake generally increased with the increasing concentration of EDDS in _Taraxacum officinal_, and Cd and Zn could be removed even under the presence of other heavy metals in this plant. By adding a chelating agent, the amount of Cd and Zn absorbed by the shoots generally increased. It is suggested that _Taraxacum officinal_ is rather tolerant against low concentrations of EDDS, as well as against heavy metals (Cd and Zn). Based on the SEM-EDS analysis, it was concluded that highly toxic elements such as Al, Bi, Cd, and Pb were distributed much on the surface of the shoots and roots, whereas the distribution of Zn on the surface of the shoots and roots was lower, since Zn is an essential element for metabolism in plants. In the case of _Gazania_, it was observed to be difficult to translocate Cd from the roots to shoots when EDDS is added, as the concentration of Zn was higher in  
Figure 12: Effect of the solvent on the extraction of (**a**) Cd and (**b**) Zn from _Gazania_ after phytoremediation. Figure 13: Effect of the carbonization temperature on the extraction of (**a**) Cd and (**b**) Zn from the incineration ash of _Gazania_. the shoots than that in the roots. _Gazania_ has low tolerance against Cd and Zn, although it has adequate tolerance against EDDS. As such, _Taraxacum officinal_ is more suitable for the phytoremediation of cadmium than _Gazania_. Our experimental treatments employed in this work were found not to be statistically different by the one-way ANOVAs, meaning that at least two of pot experiments conditions were not so different from one another. Therefore, it may be assumed that the kinds and amounts of biodegradable chelating agents added into each pot did not have such a big influence on the concentration of Cd and Zn and/or the biomass in plants (_Taraxacum officinal_ and _Gazania_) under our experimental conditions. For the effective reuse of absorbent materials, the extraction experiment of Cd and Zn from _Gazania_ after phytoremediation was investigated, showing that Cd and Zn could be extracted well from the plants by using a low concentration of nitric acid. Using the incineration ash of the plants by carbonization was shown to be more effective for the extraction of Cd and Zn. From this work, it is suggested that the biodegradable chelating agents used in this study form stable complex with heavy metal ions and promote the dissolution of these ions to the soil solution. In addition, it can be stated that the two types of plants (_Taraxacum Officiciale_ and _Gazania_) used in this research provided passable results in phytoremediation. The following are available online at [[https://www.mdpi.com/2076-341](https://www.mdpi.com/2076-341)]([https://www.mdpi.com/2076-341](https://www.mdpi.com/2076-341)) 7/11/4/1557/s1, Table S1: Operating conditions of ICP-MS. Table S2: Biomass of _Taracum officinal_. Table S3: Stability constant of EDTA and EDDS (20-25 \({}^{\circ}\)C, pH 10) in common logarithm. Table S4: Biomass of _Gazania_. Table S5. Conditions of the ANOVA, (c1-c15), shown in Figure 11. Figure S1: Effect of the EDDS concentration on the adsorption of (a) Cd and (b) Zn by _Taracum officinal_ (50% humidity). BLK represents the pot for no addition of heavy metals (i.e., Cd and Zn) as well as no addition of EDDS (i.e., Pot No. 1 in Table 1). Figure S2: Effect of the EDDS concentration on the translocation factors (TFs) of Cd and Zn in _Taracum officinal_ (50% humidity). BLK represents the pot for no addition of heavy metals (i.e., Cd and Zn) as well as no addition of EDDS (i.e., Pot No. 1 in Table 1). Figure S3. Effect of the EDDS concentration on the TF in _Taracum officinal_ under the presence of Al, Bi, Ni, and Pb. BLK represents the pot for no addition of heavy metals (i.e., Al, Pb, Bi, and Ni) as well as no addition of EDDS (i.e., Pot No. 1 in Table 2). Figure S4.