Peishan Li,Hui Ma,Sijia Qian,Yi Chen,Bo Lai,Shengyan Pu
Ferric sulfide is an appealing activator in persulfate (PS) activation process for degrading pollutants from aqueous environment, but the drawback of easy-agglomeration lead to a low utilization efficiency. In this study, we modified nFeS with sodium carboxymethyl cellulose (CMC) to improve its stability, and the performance for PS activation and p -nitrophenol (PNP) degradation is tested. After modification, the size further decreased from 23.8 to 18.4 nm, but with higher stability and catalytic reactivity. The CMC and nFeS is bonded by bidentate bridging of Fe-O bond. The degradation performance increased ∼7 times. The PS activation with CMC-nFeS activator shows higher reaction rate constant (0.093 min -1 ) with ∼90% of PNP removed compared to the pure nFeS with ∼80% of PNP removal at a low rate (0.014 min -1 ) with the same condition of 0.6 g/L activator, 8 mM PS, room temperature and initial pH in 90 min. Acidic condition and high temperature were more favorable for releasing Fe(II) to activate PS and produce active radicals. SO 4 - ·and HO·radicals played critical roles to attack on PNP. Detailed XPS analysis of the activator before and after reaction described the removal pathway as heterogeneous and homogeneous systems. Density Functional Theory (DFT) simulation results confirmed that CMC addition effectively decreased the interaction energy and improved adsorption ability of PS onto the activator surface.
Jinxue Cheng,Qinglin Huang,Yan Huang,Shiwen Yu,Changfa Xiao,Quan Hu
In this research, a novel poly(tetrafluoroethylene) (PTFE) membrane with regular geometric pore structure fabricated by near-field electrospinning (NFES) method was firstly utilized in the preparation of water-in-oil (W/O) emulsion through membrane emulsification process. Effects of NFES PTFE membranes’ pore aspect ratio (length-width ratio of rectangle pore structure) on the water-in-oil droplet size, droplet size distribution, and uniformity of water-in-oil emulsion was investigated respectively. Results showed that the increase of pore aspect ratio would bring about a smaller water-in-oil droplet size. The average water-in-oil droplet size decreased from 234.9 nm (M-1) to 167.8 nm (M-4) when the pore aspect ratio increased from 1 to 4. Compared with conventional mechanical agitation, the water-in-oil emulsion formed by membrane emulsification process showed not only more uniform water-in-oil droplet size, but also higher long-term stability (remained homogeneous after 30 days). In addition to showing the excellent membrane emulsification performance in harsh environment, the NFES PTFE membrane also exhibited excellent water-in-oil emulsion separation performance. Compared with other NFES PTFE membranes, M-1 membrane showed the highest oil flux (33.4 L m -2 h -1 , -0.02 MPa) and water rejection rate (94.4%) in the separation of water-in-oil emulsion formed by membrane emulsification process.
Efficient removal and recovery of heavy metals (HMs) from acid mine drainage (AMD) is crucial for both protecting mine ecosystems and reclaiming valuable HMs resources. In this study, biohybrid with ferrous sulfide nanoparticles ( n FeS@GS) were biosynthesized via Geobacter sulfurreducens (GS) and employed for the removal and recovery of HMs from AMD. Initially, n FeS@GS were successfully synthesized as confirmed by TEM and exhibited high efficiencies in removing Cu 2+ and Pb 2+ in solution, respectively. This occurred because bio- n FeS and GS cells synergistically enhanced the removal of Cu 2+ and Pb 2+ . What is more, the removal efficiencies of various HMs from real AMD using n FeS@GS remained high, with documented rates of 87.9 % for Cu 2+ , 96.2 % for Pb 2+ , 95.1 % for Cd 2+ , 81.4 % for Ni 2+ , 80.9 % for Mn 2+ , and 91.9 % for Zn 2+ . Subsequent characterization of the removal function through 3D-EEM, Bio-TEM, XRD, FTIR and XPS analyses revealed substantial organic capping agents derived from GS adhering to the bio- n FeS, forming surface complexes with Cu 2+ and Pb 2+ , and Cu 2+ was reduced to Cu + /Cu 0 . Zeta potential measurements, adsorption kinetics and reduction kinetics supported that the removal mechanism involved electrostatic interactions, surface complexation, ion exchange and reduction. Finally, n FeS@GS desorption rates of HMs exceeded 90.7 %, highlighting the efficacy of n FeS@GS for recovering HMs from AMD. These findings provide valuable and practical insights into the removal and recovery of HMs from AMD using biomaterials synthesized from microorganisms.
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