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Phytoremediation of Heavy Metals-Polluted Soil
Published in Pankaj Chowdhary, Abhay Raj, Contaminants and Clean Technologies, 2020
Amjad Ali, Di Guo, Amanullah Mahar, Fazli Wahid, Parimala Gnana Soundari Arockiam Jeyasundar, Muhammad Azeem, Ronghua Li, Zengqiang Zhang
Natural chelating agents such as EDDS and nitrilotriacetic acid (NTA) are alternatives to EDTA. But they also have leaching and toxicity effects on plants. Thus, proper care should be taken when practicing induced phytoremediation (Evangelou et al., 2008; Song et al., 2012). At the phytotoxic level of metals in the soil, lime and organic matter can be the best choice for delaying solubility. The use of citric acid as a chelating agent could be promising because it has a natural origin and is easily biodegradable in soil. Furthermore, citric acid is nontoxic to plants, and therefore, plant growth is not restricted (Smolińska and Cedzyńska, 2007). Chelates can be particularly useful in mobilizing HMs at high soil pH as the stability of metal–organic complex increases with increasing pH. The common chelates used for enhancing the HMs (Cd, Pb) phytoremediation are presented in Table 13.3.
Water Chemistry
Published in Louis Theodore, R. Ryan Dupont, Water Resource Management Issues, 2019
Louis Theodore, R. Ryan Dupont
Chelating agents, or chelators for short, are a class of SOCs that are used in chemical analysis as water softeners and are ingredients in many commercial products such as shampoos and food preservatives. The most commonly used synthetic chelating agents are NTA and EDTA (Grundler et al. 2004). Because of its inability to be broken down in many wastewater treatment plants, significant concentrations of EDTA have been found in the environment. Long-term accumulation of chelating agents is not a concern, however, because they are eventually broken down by bacteria (Grundler et al. 2004). Their presence in surface waters is more of a concern because of their ability to solubilize heavy metals, thereby making them mobile.
Water Chemistry
Published in Mary K. Theodore, Louis Theodore, Introduction to Environmental Management, 2021
Mary K. Theodore, Louis Theodore
Chelating agents, or chelators for short, are a class of SOCs that are used in chemical analysis as water softeners and are ingredients in many commercial products such as shampoos and food preservatives. The most commonly used synthetic chelating agents are NTA and EDTA [8]. Due to its inability to be broken down in many wastewater treatment plants, significant concentrations of EDTA have been found in the environment. Long-term accumulation of chelating agents is not a concern, however, because they are eventually broken down by bacteria [8]. Their presence in surface waters is more of a concern due to their ability to solubilize heavy metals, thereby making them mobile.
Preparation and in vivo pharmacokinetic evaluation of stable microemulsion system of cholecalciferol
Published in Journal of Dispersion Science and Technology, 2020
Myoung J. Ho, Sung H. Im, Hoe T. Jeong, Hyung T. Kim, Jeong E. Lee, Dong H. Won, Sun W. Jang, Myung J. Kang
The influence of pharmaceutical additives on chemical stability of Vit D3 was further evaluated at the concentration of 0.02 w/v% (Figure 1c). EDTA is commonly included in liquid preparations as a chelating agent and/or stabilizer to prevent catalytic oxidative reaction by forming complex with metal ions in solution.[29] CDs, cyclic oligosaccharides composed of α-(1,4) linked glucopyranose, were additionally employed to Vit D3 liquid preparations to prevent drug precipitation. They are known to contribute to chemical stabilization of Vit D3 by forming inclusion complex with the prohormone located in external phase.[24] However, the addition of EDTA or CDs markedly deteriorated drug stability in ME formulation. After 10 days of storage at 60 °C, drug contents in preparations containing EDTA, α-CD, β-CD and γ-CD were decreased to 91, 75, 67, and 74%, respectively. In particular, drug contents in liquid formulations were markedly lowered when CDs were employed. The complexation agent might have promoted drug partitioning to the external aqueous phase by forming hydrophilic inclusion compound, thus boosting aqueous solubility of Vit D3. From these findings, liquid formulation consisted of 0.14 mg of Vit D3, 225 mg of Captex 355, 45 mg of Capryol 90, and 180 mg of Solutol HS15 (pH 7) was selected as the optimized ME formulation for further evaluations.
Phytoextraction of cadmium-contaminated soils: comparison of plant species and low molecular weight organic acids
Published in International Journal of Phytoremediation, 2020
Guo Yu, Jie Liu, Yumei Long, Zhe Chen, Geoffrey I. Sunahara, Pingping Jiang, Shaohong You, Hua Lin, He Xiao
Metal bioavailability is often a limiting factor for the phytoextraction process (Agnello et al.2014). Heavy metals in the soil are stored in different forms and only the forms that are bioavailable to the plants can be absorbed. Various studies have shown that synthetic chelates and low molecular weight organic acids (LMWOAs) can increase the bioavailability of heavy metals in soils by forming water-soluble complexes with the metals. (Wu et al.2012; Agnello et al.2014; Chaturvedi et al.2015). Ethylene diamine tetraacetic acid (EDTA) is a widely studied synthetic chelate to increase (e.g., up to 200 times) the removal of heavy metals (Saifullah et al.2009). Despite its high efficiency, EDTA has become an environmental concern because of its toxicity, low degradation rate, and potential to leach into groundwater (Neugschwandtner et al.2012; Yu et al.2014). Compared with synthetic chelates, naturally occurring LMWOAs such as tartaric acid (TA), malic acid (MA), oxalic acid (OA), and citric acid (CA) are more biodegradable and are thereby more easily accepted by the public (Agnello et al.2014). These LMWOAs were promising alternatives to synthetic chelates, based on previous studies showing that LMWOAs are effective in enhancing phytoextraction efficiencies (Wang et al.2012; Chen et al.2018; Farid et al 2019). However, the enhancement of LMWOAs in Cd phytoextraction is species-specific (Agnello et al.2014), so the right LMWOAs must be identified after the selection of suitable hyperaccumulator species.
Extraction of rare earth elements from a contaminated cropland soil using nitric acid, citric acid, and EDTA
Published in Environmental Technology, 2017
Hailong Tang, Weitao Shuai, Xiaojing Wang, Yangsheng Liu
Various extraction agents, including acids and salts, as well as chelating agents have been employed for soil washing [9]. Inorganic acid is able to decrease the soil pH and promotes the desorption of the metals. However, the low pH condition may have an adverse effect on the soil nutrients and the living organisms [10]. Ethylene diamine tetraacetic acid (EDTA) is more commonly used in researches and applications, and usually achieved efficient extraction of the metals [8,11]. However, EDTA may have some adverse effect when applied in the field. EDTA might decline the biomass and the contents of photosynthetic pigments of the plants [12–13]. Biodegradable chelates, organic acids for instance, are good substitute for EDTA. Citric acid was found to have a good performance of heavy metal extractions [14–15].