Two Highly Water-Stable Imidazole-Based Ln-MOFs for Sensing Fe3+,Cr2O72-/CrO42- in a Water Environment.

Developing highly stable materials for harmful ion detection in a water environment is of much importance and challenging. Here, two three-dimensional porous structures (termed as Eu-MOF and Tb-MOF) were successfully constructed by the strategy of anchoring Eu3+/Tb3+ and rigid 1,2,4,5-benzenetetracarboxylic acid (H4BTEC) imidazole units (H3ICA) onto its frameworks. The obtained Eu-MOF and Tb-MOF display high water stability and fluorescence stability up to 30 days. Furthermore, luminescent studies reveal that Eu-MOF and Tb-MOF show rapid, recursive, and simultaneous sensing Fe3+ and Cr2O72-/CrO42- ions in water. In addition, the sensing function possesses remarkable cyclicity and selectivity even with the existence of other analogous ions.

HKUST-1 modified ultrastability cellulose/chitosan composite aerogel for highly efficient removal of methylene blue.

A novel composite HKUST-1/cellulose/chitosan aerogel (HKUST-1/CCSA) as an efficient adsorbent with hierarchical pores was prepared through a facile in situ growth way combining covalent cross-linking, vacuum freeze-drying, and solvothermal methods. By incorporating with cellulose (CE), covalently cross-linked cellulose (CE)/chitosan (CS) composite aerogel exhibits good stability, maintaining fine morphology and structures in acidic solutions under solvothermal conditions. Meantime, a high content of CS is beneficial to enhancing the growth of HKUST-1. Finally, the mass loading ratio of HKUST-1 is as high as 42.54 % in HKUST-1/CCSA. The BET specific surface area of HKUST-1/CCSA reaches 457.75 m2 g-1, which is much larger than that of CCSA (9.74 m2 g-1). HKUST-1/CCSA was applied to remove methylene blue with high adsorption capacity (526.3 mg g-1) and good recycling capability. This strategy can provide an effective and facile pathway to prepare ultra-stable polysaccharide-based composite aerogel with high specific surface area and hierarchical pores, branching out more applications in pollutant treatment fields.

Covalently crosslinked zirconium-based metal-organic framework aerogel monolith with ultralow-density and highly efficient Pb(II) removal.

Composites of MOFs and aerogels (MOFACs), as a new class of nanostructured materials, attract increasing attention due to their favorable adsorption properties. Herein, UiO-66-NH2-CS aerogel monolith (UNCAM) was synthesized by covalent crosslinking with hierarchical structure, exhibiting effective and stable adsorption of Pb(II) ions. The aerogel monolith containing 50% MOF particles possesses a ultra-low density of 15.8 mg·cm-3, which is mainly attributed to the highly porous structure. Meantime, UNCAM can be described more suitable by the pseudo-second-order model and shows a higher mass transfer rate. The highest Pb(II) adsorption capacity of aerogel monolith is up to 102.03 mg·g-1 (1.612 × 106 mg·m-3), which is comparable to literature reports. The adsorption of Pb(II) by UNCAM is an endothermic and spontaneous process and consistent with the Langmuir model, indicating that the adsorption process belongs to monolayer adsorption and chemisorption. Furthermore, the adsorption mechanisms of coordination interaction between N and Pb (II) were confirmed, and the O also played a synergistic role in adsorption on a certain degree. Lastly, The UNCAM retained 90.12% adsorption ability after three cycles. This strategy may provide an effective and versatile pathway to convert the bulk MOF particles into a shapeable form and sequentially branch out their applications in pollutant treatment fields.

Polyaniline as interface layers promoting the in-situ growth of zeolite imidazole skeleton on regenerated cellulose aerogel for efficient removal of tetracycline.

Antibiotics as newly emerging organic pollutants are arousing more and more serious environmental issues. Meantime, metal-organic frameworks (MOFs) are considered as promising adsorbents to remove antibiotics. To overcome the limitations of large-scale applications for MOFs in the powder form, herein, we proposed a strategy of in-situ growth ZIF-67 onto polyaniline (PANI) modified regenerated cellulose aerogel (RCA). First, RCA was obtained by chemical cross-linking and physical cross-linking method. Then, PANI played the role of metal chelated layers, which were coated on RCA by in-situ polymerization. Finally, ZIF-67 nanocrystals were in-situ growth on the surface of the PANI coated regenerated cellulose aerogel to synthesise the composite adsorbent ZIF-67/PANI/RCA. The loading mass ratios of ZIF-67 on RCA and PANI/RCA were 25.39% and 42.38%, respectively, which indicates that PANI as interface layers can effectively promote the in-situ growth of ZIF-67 compared with pure RCA. The obtained composite adsorbent (ZIF-67/PANI/RCA) was applied for the adsorption of tetracycline (TC) with high adsorption capacity (409.55 mg·g-1) and good recycling ability. After six cycles of adsorption-desorption, the removal efficiency toward TC was still over 94%. This strategy may provide an effective and versatile pathway to increase MOF loading mass on aerogel and sequentially branch out their applications in pollutant treatment fields.

Stratification structure of polysaccharides and proteins in activated sludge with different aeration in membrane bioreactor.

The effect of distribution pattern of polysaccharides (PS) and proteins (PN) in activated sludge (AS) stratification with different aeration rates on membrane fouling and rejection efficiency were investigated. During high aeration, PN and PS concentrations increased in supernatant, the dominant fraction (84% of PN and 73% of PS) was small molecules (<1 kDa). Less slime and loose bound extracellular polymeric substances (LB-EPS), more tight bound EPS (TB-EPS) were observed compared with low aeration. The decrease in PN/PS ratio and Ca(2+) concentration within EPS deteriorated AS flocculation ability. At slow trans-membrane pressure (TMP) rise stage, fouling rate under high aeration was 41% lower than low aeration due to lower PN within EPS outer. Low PS rejection rate (about 23%) leaded to higher PS in effluent at this stage. High PS rejection rate (about 94%) at rapid TMP rise stage resulted in about 2.2-time higher fouling rate than that low aeration.