Zirconium-organic framework as a novel adsorbent for arsenate remediation from aqueous solutions

Customizable Zr-MOF nanoantidote-based multieffective arsenic detoxification and its extended low-toxic therapy

Arsenic (As) poisoning has become a global public problem threatening human health. Chelation therapy (CT) is the preferred treatment for arsenic poisoning. Nevertheless, efficient and safe arsenic removal in vivo remains a daunting challenge due to the limitations of chelators, including weak affinity, poor cell membrane penetration, and short half-life. Herein, a mercapto-functionalized and size-tunable hierarchical porous Zr-MOF (UiO-66-TC-SH) is developed, which possesses abundant arsenic chemisorption sites, effective cell uptake ability, and long half-life, thereby efficiently removing toxic arsenic in vivo. Moreover, the strong binding affinity of UiO-66-TC-SH for arsenic reduces systemic toxicity caused by off-target effects. In animal trials, UiO-66-TC-SH decreases the blood arsenic levels of acute arsenic poisoning mice to a normal value within 48 h, and the efficacy is superior to clinical drugs 2,3-dimercaptopropanesulfonic acid sodium salt (DMPS). Meanwhile, UiO-66-TC-SH also significantly mitigates the arsenic accumulation in the metabolic organs of chronic arsenic poisoning mice. Surprisingly, UiO-66-TC-SH also accelerates the metabolism of arsenic in organs of tumor-bearing mice and alleviates the side effects of arsenic drugs antitumor therapy. STATEMENT OF SIGNIFICANCE: Arsenic (As) contamination has become a global problem threatening public health. The present clinical chelation therapy (CT) still has some limitations, including the weak affinity, poor cell membrane permeability and short half-life of hydrophilic chelators. Herein, a metal-organic framework (MOF)-based multieffective arsenic removal strategy in vivo is proposed for the first time. Mercapto-functionalized and size-tunable hierarchical porous Zr-MOF nanoantidote (denoted as UiO-66-TC-SH) is accordingly designed and synthesized. After injection, UiO-66-TC-SH can form Zr-O-As bonds and As-S bonds with arsenic, thus enhancing arsenic adsorption capacity, cycling stability and systemic safety simultaneously. The acute arsenic poisoning model results indicate that UiO-66-TC-SH shows superior efficacy to the clinical drug sodium dimercaptopropanesulfonate (DMPS). More meaningfully, we find that UiO-66-TC-SH also accelerates the metabolism of arsenic in organs of tumor-bearing mice and alleviates side effects of arsenic drugs anti-tumor therapy.

Synthesis of fenugreek gum-based metal-organic framework (FG/Zr-AIPA MOF) composite beads for sequestration of heavy metal ions from aqueous solution

Metal-organic frameworks (MOFs) are a prominent class of materials due to their large surface area and customized structures. This gives them specificity and high adsorption capacity while they lack mechanical strength and reusability. Integrating MOFs with polysaccharide matrix may retain MOF characteristics along with imparting structural integrity. In the present study, zirconium MOF-based fenugreek composite (FG/Zr-AIPA) beads were synthesised by a single droplet method and utilised for removal of Cr(VI), Pb(II) and Fe(III) from aqueous solution. The structure, morphology and composition of beads were evaluated by FTIR, XRD, TGA, BET, FESEM, EDX, XPS and zeta potential analysis. Adsorption isotherm, kinetics and thermodynamics were studied for Cr(VI), Pb(II) and Fe(III) adsorption. Adsorption kinetics and isotherm study revealed that all the metal ions were adsorbed through a monolayer chemisorption process. The maximum adsorption capacity was 344.43, 270.02 and 223.21 mg g-1 for Cr(VI), Pb(II) and Fe(III), respectively, based on the Langmuir isotherm study. The thermodynamics study revealed that the interaction between the metal ions and the composite beads was spontaneous and endothermic. The FG/Zr-AIPA composite beads exhibited good reusability for the removal of Cr(VI), Pb(II) and Fe(III). The results open new possibilities for the preparation of polysaccharide MOF-based composite beads which exhibit substantial potential for water treatment applications.

Removal of copper by Azolla filiculoides and Lemna minor: phytoremediation potential, adsorption kinetics and isotherms

Phytoremediation is an eco-friendly biotechnology with low costs. The removal of copper (Cu) from polluted water by the two floating plant species Azolla filiculoides and Lemna minor was observed and recorded. Plants were exposed to different Cu (II) concentration (0.25–1.00 mg/L) and sampling time (Days 0, 1, 2, 5 and 7). Both plants can remove Cu at 1.00 mg Cu/L water, with the highest removal rates of 100% for A. filiculoides and 74% for L. minor on the fifth day of exposure. At the end of the exposure period (Day 7), the growth of A. filiculoides exposed to 1.00 mg Cu/L was inhibited by Cu, but the structure of the inner cells of A. filiculoides was well organized as compared to the initial treatment period. Regarding L. minor, Cu at 1.00 mg/L negatively impacted both the growth and morphology (shrinking of its inner structure) of this plant. This is due to the higher accumulation of Cu in L. minor (2.86 mg/g) than in A. filiculoides (1.49 mg/g). Additionally, the rate of Cu removal per dry mass of plant fitted a pseudo-second order model for both plants, whereas the adsorption equilibrium data fitted the Freundlich isotherm, indicating that Cu adsorption occurs in multiple layers. Based on the results, both species can be applied in the phytoremediation of Cu-polluted water.