Achieving ultrafast and highly selective capture of radiotoxic tellurite ions on iron-based metal-organic frameworks through coordination bond-dominated conversion.

Chemically durable and effective adsorbents for radiotoxic TeOx2- (TeIV and TeVI) anions remain in great demand for contamination remediation. Herein, a low-cost iron-based metal-organic framework (MIL-101(Fe)) was used as an adsorbent to capture TeOx2- anions from contaminated solution with ultrafast kinetics and record-high adsorption capacity of 645 mg g-1 for TeO32- and 337 mg g-1 for TeO42-, outperforming previously reported adsorbents. Extended X-ray absorption fine structure (EXAFS) and density functional theory (DFT) calculations confirmed that the capture of TeOx2- by MIL-101(Fe) was mediated by the unique C-O-Te and Fe-O-Te coordination bonds at corresponding optimal adsorption sites, which enabled the selective adsorption of TeOx2- from solution and further irreversible immobilization under the geological environment. Meanwhile, MIL-101(Fe) works steadily over a wide pH range of 4-10 and at high concentrations of competing ions, and it is stable under ß-irradiation even at high dose of 200 kGy. Moreover, the MIL-101(Fe) membrane was fabricated to efficiently remove TeO32- ions from seawater for practical use, overcoming the secondary contamination and recovery problems in powder adsorption. Finally, the good sustainability of MIL-101(Fe) was evaluated from three perspectives of technology, environment, and society. Our strategy provides an alternative to traditional removal methods that should be attractive for Te contamination remediation.

A rice-chicory rotation pattern ensures safe grain production and phytoremediation of cadmium-contaminated paddy fields: A four-year field experiment in southern China.

Cadmium (Cd) contamination in paddy systems is a serious problem, and a strategy must be devised that ensures safe grain production and rapid remediation of soil Cd contamination. To investigate the remediation potential of crop rotation and its effect on Cd accumulation in rice, a four-year (seven-season) rice-chicory rotation field trial was conducted on a moderately acidic Cd-contaminated paddy soil. Rice was planted in summers, followed by straw removal, and chicory, a Cd-enrichment plant, was planted during winter fallows. Rotation effects were compared with those with rice only (control). Rice yields between the rotation and control were not significantly different, whereas Cd concentrations in rice tissues decreased in the rotation. Cd concentration in brown rice of the low-Cd variety decreased to less than 0.2 mg/kg (national food safety standard) from the third season onward, whereas in the high-Cd variety, it decreased from 0.43 mg/kg in the first season to 0.24 mg/kg in the fourth season. The highest Cd concentration in chicory aboveground parts was 24.47 mg/kg, with an enrichment factor of 27.81. Chicory had high regenerative capacity and was repeatedly harvested for biomass in multiple mowings, with average aboveground biomass over 2000 kg/ha in a single mowing. Theoretical phytoextraction efficiency (TPE) of one rice season with straw removal was 0.84%-2.44%, whereas the highest TPE of one chicory season reached 8.07%. The seven seasons of rice-chicory rotation extracted up to 407 g/ha Cd from soil with a TPE exceeding 20%. Therefore, rice-chicory rotation and straw removal can effectively reduce Cd accumulation in subsequent rice crops, without interrupting production and simultaneously rapidly remediating Cd-contaminated soil. Thus, the production potential of light to moderately Cd-contaminated paddy fields can be realized with crop rotation.

Cichorium intybus L. is a potential Cd-accumulator for phytoremediation of agricultural soil with strong tolerance and detoxification to Cd.

Identifying suitable plants for phytoremediation of Cd (cadmium) contaminated agricultural soil is critical. In this study, whether chicory (Cichorium intybus L.) qualified as an ideal accumulator for phytoremediation was investigated. The hydroponic and pot experiments showed that Cd concentration in chicory leaves exceeded 100 mg kg-1 (BCF >1, TF >1) with 40 mg kg-1 Cd in pot; No significant effects on chicory growth, leaf protein and physiological and biochemical aspects when treated with ≤ 20 µM or 40 mg kg-1 Cd, because chicory could relieve Cd toxicity by increasing activities of photoprotection mechanisms, the reactive oxygen species scavenging system and concentrations of functional groups in plant tissues. In field experiment, 16.2 and 26.6 t ha-1 of chicory leaves was harvested in winter and summer, respectively. The highest Cd concentration in leaves was close to 25.0 mg kg-1 (BCF >1, TF >1) from the acid soil with 0.980 mg kg-1 Cd. Over 320 g ha-1 Cd was extracted from soil by harvesting chicory leaves both in winter and summer, with 9.24% and 12.9% of theoretical phytoremediation efficiency. Therefore, chicory can be as an ideal Cd-accumulator for phytoremediation of slight-to-moderate Cd-contaminated agricultural soil in any season.

Revealing the role of oxygen-containing functional groups on graphene oxide for the highly efficient adsorption of thorium ions.

Oxygen-containing functional groups on the surface of carbon materials can promote the adsorption capacity of radioactive thorium ions (Th(IV)), but their effect on the adsorption of Th(IV) has not been systematically revealed. Herein, to elucidate the nature of oxygen-containing group-mediated Th(IV) adsorption, a series of graphene oxide nanoflakes (GONFs) with different contents of oxygen-containing groups on the surface were prepared. The experimental results showed that the high adsorption of Th(IV) not only resulted from the oxygen content, but also was related to the type of oxygen-containing functional groups on GONFs. Subsequent density functional theory (DFT) calculations revealed that the high adsorption capacity for Th(IV) originated from the oxygen-containing groups and their adjacent activated sp2 carbon atoms. More importantly, the coordination of Th(IV) with oxygen functional groups induced the aggregation of GONFs, leading to the sedimentation of GONFs, which facilitated the separation of adsorbents and enabled the GONFs to be a more practical adsorbent for Th(IV). This work deepens our understanding of the role of oxygen-containing groups on Th(IV) adsorption and provides a new strategy for the design and synthesis of high-performance surface oxygen-containing carbon-based adsorbents with practical application potential.