Investigating the potential of structurally defective UiO-66 for Sb (V) removal from tailing wastewater.

Antimony contamination of tailings from the mining process remain attracted a great amount of concern. In this study, defective UiO-66-X crystal materials are rationally constructed using trifluoroacetic acid and hydrochloric acid as modulators for the removal of Sb(V) from actual tailing sand leachates. XRD and TG characterizations reveal that the number and kind of defects in UiO-66 are influenced by the type of modulators and the addition of trifluoroacetic acid makes UiO-66-TFA contain both cluster and ligand defects. Adsorption experiments show that UiO-66 and UiO-66-HCl achieve 100% removal of Sb(V) at pH 7.5 of the tailing sand leachate, and up to 90% removal of Sb(V) by the three materials at pH 2.5. It is noteworthy that the removal rate of Sb(V) by UiO-66-HCl is still satisfactory even under strongly acidic conditions at pH 0.5, with good potential for practical applications. Four kinetic models are used to fit the adsorption data and the analysis shows that the mechanism of Sb(V) adsorption by three adsorbent is all pseudo-second order and chemisorption acts as an important role in the adsorption process. In addition, the fixed bed adsorption experiments show that the material exhibit good prospects for practical applications.

Perfluorinated conjugated microporous polymer for targeted capture of Ag(I) from contaminated water.

The maximum targeted capture silver from contaminated water is urgently necessary for sustainable development. Herein, the perfluorination conjugated microporous polymer adsorbent (F-CMP) has been fabricated by Sonogashira-Hagihara coupling reaction and employed to remove Ag(I) ions. Characterizations of NMR, XPS and FT-IR indicate the successful synthesis of F-CMP adsorbent. The influence factors of F-CMP on Ag(I) adsorption behavior are studied, and the adsorption capacity of Ag(I) reaches 251.3 mg/g. The experimental results of isothermal adsorption and kinetic adsorption are consistent with the Freundlich model and pseudo-second-order isothermal adsorption model, which follows a multilayer adsorption behavior on the uniform surface of the adsorbent, and the chemical adsorption becomes the main rate-limiting step. Combined with DFT calculation, the adsorption mechanism of Ag(I) by F-CMP is elucidated. The peaks shift of sp before and after adsorption is larger than that of F1s, suggesting that the -CC- on the F-CMP becomes the dominant chelation site of Ag(I). Furthermore, F-CMP exhibits specific adsorption for Ag(I) in polymetallic complex water, with the maximum selectivity coefficient of 31.5. Our study may provide a new possibility of perfluorinated CMPs for effective capture of Ag(I) ions to address environmental issues.

Theoretical analysis of naproxen reaction with sulfate and hydroxyl radicals in the aqueous phase: Investigating reactive sites and reaction kinetics.

In this study, we have utilized theoretical calculations to predict the reaction active sites of naproxen when reacting with radicals and to further study the thermodynamics and kinetics of the reactions with ·OH and SO4-·. The evidence, derived from the average local ionization energy and electrostatic potential, points to the naphthalene ring as the preferred site of attack, especially for the C2, C6, C9, and C10 sites. The changes in Gibbs free energy and enthalpy of the reactions initiated by ·OH and SO4-· ranged between -19.6 kcal/mol - 26.3 kcal/mol and -22.3 kcal/mol -18.5 kcal/mol, respectively. More in-depth investigation revealed that RA2 pathway for ·OH exhibited the lowest free energy of activation, suggesting this reaction is more inclined to proceed. The second-order rate constant results indicate the ·OH attacking reaction is faster than reactions initiated by SO4·-, yet controlled by diffusion. The consistency between theoretical findings and experimental data underscores the validity of this computational method for our study.

Lattice-Defect-Enhanced Adsorption of Arsenic on Zirconia Nanospheres: A Combined Experimental and Theoretical Study.

Zirconium oxide (ZrO2) nanoadsorbents exhibit great potential in the remediation of arsenic-polluted water. However, physicochemical structure-adsorption performance relationship is not well-understood, which retards further development of high-performance ZrO2 nanoadsorbents. Herein, a facile-controlled crystallization strategy was developed to synthesize defective ZrO2 with the assistance of organic ligands. Systematic characterizations showed that this proposed synthesis strategy can be exploited to regulate the defective density of ZrO2, whereas other structural properties remain almost unchanged. Batch adsorption experiments exhibited that UiO-66-SH-A with a higher lattice defect possessed a larger capacity and a faster rate for the uptake of As(III)/As(V). The maximum capacities of UiO-66-SH-A to uptake As(III) and As(V) were up to 90.7 and 98.8 mg/g, respectively, which are 12.3 and 11.5 times larger than those of UiO-66-A. These results from the structure-performance analysis and theoretical calculations further reveal that lattice defect plays a key role in the enhancement of arsenic adsorption on ZrO2. We hope this new understanding of the structure-dependent adsorption performance will provide a valuable insight for designing Zr-based nanoadsorbents to capture arsenic.

New insight on the adsorption capacity of metallogels for antimonite and antimonate removal: From experimental to theoretical study.

Development of high capacity material for antimonite (Sb(III)) and antimonate (Sb(V)) removal is the key to solving water antimony contamination. Three-dimensional Cu(II)-specific metallogels (Cu-MG), which are considered to have high density adsorption sites for antimony (Sb), were first applied to adsorb Sb(III) and Sb(V). Batch assays resulted in adsorption capacities of Cu-MG for Sb(III) and Sb(V) at 102.4 mg/g and 264.1 mg/g, respectively. In addition, the adsorption capacity for Sb(III) was up to 225.7 mg/g using in situ oxidation. Kinetic assays resulted in more than 90% removal of Sb in 30 min. X-ray photoelectron spectroscopy (XPS) revealed the adsorption of Sb depended mainly on coordination interactions of vacant orbitals of the Cu atom with the lone-pairs of the O atom of Sb(OH)3 or Sb(OH)6-. Adsorption energy based on density functional theory (DFT) confirmed that Sb(III) adsorbed as a single layer whereas Sb(V) adsorbed as a multi-layer. These findings are consistent with experimental results. In addition, DFT calculations revealed that the Cu-MG theoretical capacity for Sb(V) adsorption is higher than for Sb(III). Cu-MG is a new and promising class of adsorbents for the removal of Sb(III) and Sb(V) from contaminated water.

n-Butylidenephthalide exhibits protection against neurotoxicity through regulation of tryptophan 2, 3 dioxygenase in spinocerebellar ataxia type 3.

Spinocerebellar ataxia type 3 or Machado-Joseph disease (SCA3/MJD) is characterized by the repetition of a CAG codon in the ataxin-3 gene (ATXN3), which leads to the formation of an elongated mutant ATXN3 protein that can neither be denatured nor undergo proteolysis in the normal manner. This abnormal proteolysis leads to the accumulation of cleaved fragments, which have been identified as toxic and further they act as a seed for more aggregate formation, thereby increasing toxicity in neuronal cells. To date, there have been few studies or treatment strategies that have focused on controlling toxic fragment formation. The aim of this study is to develop a potential treatment strategy for addressing the complications of toxic fragment formation and to provide an alternative treatment strategy for SCA3. Our preliminary data on anti-aggregation and toxic fragment formation using an HEK (human embryonic kidney cells) 293T-84Q-eGFP (green fluorescent protein) cell model identified n-butylidenephthalide (n-BP) as a potential drug treatment for SCA3. n-BP decreased toxic fragment formation in both SCA3 cell and animal models. Moreover, results showed that n-BP can improve gait, motor coordination, and activity in SCA3 mice. To comprehend the molecular basis behind the control of toxic fragment formation, we used microarray analysis to identify tryptophan metabolism as a major player in controlling the fate of mutant ATXN3 aggregates. We also demonstrated that n-BP functions by regulating the early part of the kynurenine pathway through the downregulation of tryptophan 2, 3-dioxygenase (TDO2), which decreases the downstream neurotoxic product, quinolinic acid (QA). In addition, through the control of TDO2, n-BP also decreases active calpain levels, an important enzyme involved in the proteolysis of mutant ATXN3, thereby decreasing toxic fragment formation and associated neurotoxicity. Collectively, these findings indicate a correlation between n-BP, TDO2, QA, calpain, and toxic fragment formation. Thus, this study contributes to a better understanding of the molecular interactions involved in SCA3, and provides a novel potential treatment strategy for this neurodegenerative disease.