Cr(VI) removal during cotransport of nano-iron-particles combined with iron sulfides in groundwater: Effects of D. vulgaris and S. putrefaciens.

Iron-based materials such as nanoscale zerovalent iron (nZVI) are effective candidates to in situ remediate hexachromium (Cr(VI))-contaminated groundwater. The anaerobic bacteria could influence the remediation efficiency of Cr(VI) during its cotransport with nZVI in porous media. To address this issue, the present study investigated the adsorption and reduction of Cr(VI) during its cotransport with green tea (GT) modified nZVI (nZVI@GT) and iron sulfides (FeS and FeS2) in the presence of D. vulgaris or S. putrefaciens in water-saturated sand columns. Experimental results showed that the nZVI@GT preferred to heteroaggregate with FeS2 rather than FeS, forming nZVI@GT-FeS2 heteroaggregates. Although the presence of D. vulgaris further induced nZVI@GT-FeS2 heteroaggregates to form larger clusters, it pronouncedly improved the dissolution of FeS and FeS2 for more Cr(VI) reduction associated with lower Cr(VI) flux through sand. In contrast, S. putrefaciens could promote the dispersion of the heteroaggregates of nZVI@GT-FeS2 and the homoaggregates of nZVI@GT or FeS by adsorption on the extracellular polymeric substances, leading to the improved transport of Fe-based materials for a much higher Cr(VI) immobilization in sand media. Overall, our study provides the essential perspectives into a chem-biological remediation technique through the synergistic removal of Cr(VI) by nZVI@GT and FeS in contaminated groundwater. ENVIRONMENTAL IMPLICATION: The green-synthesized nano-zero-valent iron particles (nZVI@GT) using plant extracts (or iron sulfides) have been used for in situ remediation of Cr(VI) contaminated groundwater. Nevertheless, the removal of Cr(VI) (including Cr(VI) adsorption and Cr(III) generation) could be influenced by the anaerobic bacteria governing the transport of engineered nanoparticles in groundwater. This study aims to reveal the inherent mechanisms of D. vulgaris and S. putrefaciens governing the cotransport of nZVI@GT combined with FeS (or FeS2) to further influence the Cr(VI) removal in simulated complex groundwater media. Our findings provides a chemical and biological synergistic remediation strategy for nZVI@GT application in Cr(VI)-contaminated groundwater.

Synthesis and Properties of Dithiafulvenyl Functionalized Spiro[fluorene-9,9'-xanthene] Molecules.

Two spiroannulated molecular structures with dithiafulvenyl units functionalized at the 2,2',7,7'- (SFX-DTF1) and 2,3',6,'7- (SFX-DTF2) positions of a spiro[fluorene-9,9'-xanthene] core were synthesized. Studies revealed the hole mobility was significantly influenced by the dithiafulvenyl functionalized positions in the molecular structure. To explore their primary applications as hole-transporting materials in perovskite solar cells, SFX-DTF1-based devices exhibited a power conversion efficiency of 10.67% without the use of p-type dopants, yielding good air stability.

Effect of nanoscale zero-valent iron confined in mesostructure on Escherichia coli.

Nanoscale zero-valent iron particles (NZVIs) confined in the mesochannels of SBA-15 have superabilities in the remediation of contaminated groundwater. As a new kind of remediation nanomaterials, it is necessary to investigate the ecotoxicity of NZVIs/SBA-15 composites during their applications. In this study, we evaluated the toxicity of NZVIs/SBA-15 on Escherichia coli and proposed a possible mechanism. Compared with the bare NZVIs and SBA-15 surface-supported NZVIs at the same equivalent concentration of NZVIs (0.42 or 0.84 g/L), NZVIs/SBA-15 composites had a minimal cytotoxicity on E. coli, though they had the smallest iron nanoparticle size, the largest zeta potential, and the best stability in water. The mechanism may be attributed to the protection of the mesochannels and the electrostatic hindrance resulting from the silica host that could keep NZVIs from directly contacting with the cell. Thus, NZVIs confined in the mesostructures can be safely used in the remediation of contaminated natural water.

[Bioavailability of nickel and its complexes during anaerobic digestion].

The biouptake of nickel and its complexes for methanogenic enrichment in the presence of different chelators during batch methane fermentation were investigated in this paper. The results showed that the chelators had obvious effects on anaerobic digestion. At sodium acetate concentration of 85 mmol/L, sulfides concentration of 1 mmol/L, nickel concentration of 200 micromol/L and temperature was 35 degrees C, methane production in the NTA added system were 15% and 9% which was higher than that in CA and EDTA amended ones. While nickel concentration was 100 micromol/L, methane production in NTA added system were 43% and 57% which was higher than that in CA and EDTA amended ones. The biouptake of nickel for methanogenic enrichment related to the species of nickel complexes. NTA was the best chelator for stimulating nickel biouptake in the anaerobic reactors, and EDTA was the better one. The biouptake of Ni-CA complexes was the minimum for the methanogenic enrichment.