Abstract Municipal solid waste compost, the circular economy's closed-loop product often contains excessive amounts of toxic heavy metals, leading to market rejection and disposal as waste material. ...To address this issue, the study develops a novel approach based on: (i) utilizing plant-based biodegradable chelating agent, l -glutamic acid, N , N -diacetic acid (GLDA) to remediate heavy metals from contaminated MSW compost, (ii) comparative assessment of GLDA removal efficiency at optimal conditions with conventional nonbiodegradable chelator EDTA, and (iii) enhanced pre- and post-leaching to evaluate the mobility, toxicity, and bioavailability of heavy metals. The impact of treatment variables, such as GLDA concentration, pH, and retention time, on the removal of heavy metals was investigated. The process was optimized using response surface methodology to achieve the highest removal effectiveness. The findings indicated that under optimal conditions (GLDA concentration of 150 mM, pH of 2.9, retention time for 120 min), the maximum removal efficiencies were as follows: Cd-90.32%, Cu-81.96%, Pb-91.62%, and Zn-80.34%. This process followed a pseudo-second-order kinetic equation. Following GLDA-assisted leaching, the geochemical fractions were studied and the distribution highlighted Cd, Cu, and Pb's potential remobilization in exchangeable fractions, while Zn displayed integration with the compost matrix. GLDA-assisted leaching and subsequent fractions illustrated transformation and stability. Therefore, this process could be a sustainable alternative for industrial applications (agricultural fertilizers and bioenergy) and social benefits (waste reduction, urban landscaping, and carbon sequestration) as it has controlled environmental footprints. Hence, the proposed remediation strategy, chemically assisted leaching, could be a practical option for extracting heavy metals from MSW compost, thereby boosting circular economy.
Soil washing with biodegradable chelator is a promising technique for treating metal-contaminated soil. However, limited information is available on the effects of such treatments on plant growth and ...the accumulation of residual metals from remediated soil. Four biodegradable chelators including glutamate–N,N–diacetic acid (GLDA), iminodisuccinic acid (ISA), polyaspartic acid (PASP), and glucomonocarbonic acid (GCA) were employed to remove Cd, Pb, and Zn from polluted soils, and two common vegetables (Brassica bara and Lactuca sativa) were used to verify the fitness of plants grown on the washed soil. The ISA and GLDA demonstrated excellent Cd, Pb, and Zn removal efficiencies (25–85%) compared with GCA and PASP. Moreover, the phytoavailability of soil Cd, Pb, and Zn decreased after washing, and this effect was more pronounced for GLDA than ISA. B. bara and L. sativa grew well in the washed soils but considerably less biomass was produced than by plants grown in unwashed soil. Their photosynthetic capacities, oxidation defense abilities, and nutritional qualities were improved, compared with plants cultivated in the original soils. The ISA and GLDA treatments decreased the Cd, Pb, and Zn concentrations in B. bara and L. sativa shoots but the GCA and PASP treatments had no effect or increased the metal concentrations. B. bara and L. sativa grown in remediated soils were unacceptable for human consumption because the Cd and Pb concentrations in the edible parts were higher than the European legal limits. Soil washing with biodegradable chelators especially ISA and GLDA successfully removed toxic metals and allowed the plants to grow well while decreasing the uptake of metals remaining in the remediated soil.
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•The performance of soil washing with biodegradable chelators was evaluated.•The biomass of B. bara and L. sativa was lower in the washed soil.•Physiological factors implied similar fitness of B. bara and L. sativa on washed soil.•Plant growth on washed soil showed a reduction of metal uptake in shoots by 7–90%.
The determination of aminopolycarboxylate chelators in environmental samples has remained an analytical challenge due to the structural similarities of these species and their minute concentrations ...in such matrices. Herein, we report a fast and sensitive technique for the determination of multiple chelator complexes in an aqueous matrix using ultra-performance liquid chromatography-quadrupole/time-of-flight mass spectrometry (UPLC-Q-TOF-MS). Eight chelators, including non-biodegradable (EDTA, EDTAOH, GEDTA, DPTAOH and DTPA) and biodegradable (EDDS, GLDA, and MGDA) variants were examined after complexation with CuII. The detection of these species using reverse-phase chromatography was compared with that achieved with hydrophilic interaction chromatography based on the corresponding peak resolution and retention time. The effect of varying the composition and pH of the mobile phase on the corresponding peak profiles and intensities for the chelator complexes was also evaluated. The CuII-derivatives of the chelators were individually detected under the optimized operating conditions. Relative to high-performance liquid chromatography equipped with a photodiode array detector, the developed UPLC-Q-TOF-MS technique provides rapid determination of chelator complexes in aqueous matrices with high sensitivity and superior peak resolution. The limit of detection ranged from 1.7–36 nmol L–1, and the limit of quantification ranged from 5.7–120 nmol L–1 for the eight chelator complexes in solution. The coefficients of determination (R2) were 0.962–0.999 for the chelators with an average relative uncertainty of 2.2%. The method was validated using a simulated mixed matrix and river water by standard addition (recovery: 83−100%).
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•A new technique for the determination of metal-chelator complexes by UPLC-Q-TOF-MS.•Fast separation and better retention achieved using HILIC amide column.•Direct measurement of CuII-chelator complexes without pretreatment steps.•UPLC-Q-TOF-MS method has high sensitivity and peak quality over conventional HPLC-PDA.
Heavy-metal ions are common pollutants in wastewater and are thus attracting considerable attention. Herein, an eco-friendly biodegradable adsorbent, iminodisuccinic acid (IDS) modified attapulgite ...(ATP) is prepared by graft-polymerization to reduce Cu(II) in water, referred as IDS-ATP. The equilibrium adsorption capacity of IDS-ATP for Cu(II) is increased by 329.5% and 272% compared with raw ATP and non-degradable chelator ethylenediaminetetraacetic acid-modified ATP (EDTA-ATP), respectively. Moreover, the adsorption capacities for Cu(II) in combined system increased by 186% compared with in single system. The structure and surface properties of IDS-ATP are characterized, demonstrating that the IDS moieties are anchored on the surface of ATP without structural damage. In the aqueous Cu(II) (64 mg /L), the best adsorption pH is 5.0, the best dosage is 800 mg/L, and the adsorption equilibrium time is 4 h. The adsorption of IDS-ATP is chemical adsorption and regenerated adsorbent still exhibits high adsorption capacity. The adsorption mechanism includes the coordination of amino groups with Cu(II), the chelation of -COOH on heavy metals (HMs), and the ion exchange. Taking Cu(II) as an example to study the process of IDS-ATP in water, it is beneficial to apply this degradable material to reduce the other HMs.
Excavated debris (soil and rock) contaminated with geogenic arsenic (As) is an increasing concern for regulatory organizations and construction stakeholders. Chelator-assisted soil flushing is a ...promising method for practical on-site remediation of As-contaminated soil, offering technical, economic, and environmental benefits. Ethylenediaminetetraacetic acid (EDTA) is the most prevalent chelator used for remediating As-contaminated soil. However, the extensive environmental persistence and potential toxicity of EDTA necessitate the exploration of eco-compliant alternatives. In this study, the feasibility of the conventional flushing method
pump-and-treat
and two newly designed
immersion and sprinkling
techniques were evaluated at the laboratory scale (small-scale laboratory experiments) for the on-site treatment of As-contaminated excavated debris. Two biodegradable chelators, L-glutamic acid-N,N′-diacetic acid (GLDA) and 3-hydroxy-2,2′-iminodisuccinic acid (HIDS), were examined as eco-friendly substitutes for EDTA. Additionally, this study highlights a useful post-treatment measure to ensure minimal mobility of residual As in the chelator-treated debris residues. The pump-and-treat method displayed rapid As-remediation (
t
, 3 h), but it required a substantial volume of washing solution (100 mL g
−1
). Conversely, the immersion technique demonstrated an excellent As-extraction rate using a relatively smaller washing solution (0.33 mL g
−1
) and shorter immersion time (
t
, 3 h). In contrast, the sprinkling technique showed an increased As-extraction rate over an extended period (
t
, 48 h). Among the chelators employed, the biodegradable chelator HIDS (10 mmol L
−1
; pH, 3) exhibited the highest As-extraction efficiency. Furthermore, the post-treatment of chelator-treated debris with FeCl
3
and CaO successfully reduced the leachable As content below the permissible limit.
The extraction efficiency of heavy metals from soils using three forms of gamma poly-glutamic acid (γ-PGA) as the washing agents was investigated. Controlling factors including agent concentrations, ...extraction time, pH, and liquid to soil ratio were evaluated to determine the optimum operational conditions. The distribution of heavy metal species in soils before and after extraction processes was analyzed. Up to 46 and 74% of heavy metal removal efficiencies were achieved with one round and a sequential extraction process using H-bonding form of γ-PGA (200 mM) with washing time of 40 min, liquid to solid ratio of 10 to 1, and pH of 6. Major heavy metal removal mechanisms were (1) γ-PGA-promoted dissolution and (2) complexation of heavy metal with free carboxyl groups in γ-PGA, which resulted in heavy metal desorption from soils. Metal species on soils were redistributed after washing, and soils were remediated without destruction of soil structures and productivity.
Excavated soils from construction activities contaminated with geogenic arsenic (As) are increasing concerns owing to after disposal impact on ecosystem and human health. Washing remediation with ...chelators, e.g., ethylenediaminetetraacetic acid (EDTA), has been evaluated widely to treat contaminated soil. However, prolonged persistence and noxiousness of EDTA and its homologs evoke eco-concerns. Herein, the efficiency of ethylenediamine N,N'-disuccinic acid (EDDS) and 3-hydroxy-2,2'-imino disuccinic acid (HIDS) was evaluated to treat As-contaminated excavated soil as eco-compliant alternatives to EDTA. Besides, the post-treatment preferences for the chelator-washed suspension and soil residue were also assessed to immobilize eluted-As and suppress subsequent As-leaching, respectively. The efficiency of chelators toward the extraction of As was positively correlated with washing variables (e.g., washing time, solution pH, chelator concentration, liquid-to-soil ratio, and shaking speed) and optimized for maximum As-removal. Biodegradable chelator, HIDS (10 mmol L
–1
, pH 11) showed better washing effectiveness among the tested chelators (duration, 12 h). The eluted-As in chelator-washed suspension was better immobilized with combined Fe
III
and Ca
II
salt application blended with organic coagulant and polymer flocculant. Stabilization/solidification (S/S) of As-content in soil residues with cement-based binders was examined with or without the addition of Fe
III
. The cement amendments, except the ordinary Portland cement, Tuff-rock ace, and GS225, showed superior As-stabilization capability without Fe
III
-additives. The proposed combined remediation approach can be a green solution to recycle As-contaminated surplus soils for extensive geotechnical applications.
Highlights
Biodegradable chelators are used to remediate As-contaminated excavated soil.
As-extraction efficiency significantly correlated with the washing variables.
Comparative extraction performance of chelators toward other PTEs was evaluated.
Suppression of As-leaching below the regulatory standard was achieved.
An efficient and eco-friendly process without post-use toxic effects is designed.
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