In this study, a biochar-supported nanoscale zero-valent iron (nZVI@BC) material was used for in situ remediation of hexavalent chromium-contaminated soil. Sedimentation tests and column experiments ...were used to compare the stability and mobility of nZVI@BC and bare-nZVI. The immobilisation efficiency of chromium, toxic effect of chromium and the content of iron were assessed through leaching tests and pot experiments. Sedimentation tests and transport experiments indicated that nZVI@BC with nZVI to BC mass ratio of 1:1 exhibited better stability and mobility than that of bare-nZVI. The immobilisation efficiency of Cr(VI) and Crtotal was 100% and 92.9%, respectively, when the soil was treated with 8 g/kg of nZVI@BC for 15 days. Moreover, such remediation effectively reduced the leachability of Fe caused by bare-nZVI. In addition, pot experiments showed that such remediation reduced the phytotoxicity of Cr and the leachable Fe and was favourable for plant growth.
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•Biochar-supported nanoscale zero-valent iron composite (nZVI@BC) was synthesised.•nZVI@BC exhibited better stability and mobility than that of bare-nZVI.•nZVI@BC reduced the leachability and bioavailability of Cr in soil.•nZVI@BC decreased the phytotoxicity of Cr and leachable Fe caused by bare-nZVI.
nZVI@BC exhibited better stability and mobility than that of bare-nZVI, and reduced the phytotoxicity of Cr and leachable Fe caused by bare-nZVI.
► Fe3O4 MNPs synthesized by facile coprecipitation method were characterized roundly. ► Bisphenol A can be effectively eliminated in US+Fe3O4+H2O2 system in neutral pH. ► Fe3O4 MNPs performed similar ...good activity within a wide pH range from 3 to 9. ► Fe3O4 remained good stability and activity even after several recycles.
In this study, the Fe3O4 magnetic nanoparticles (MNPs) were synthesized as heterogeneous catalysts to effectively degrade bisphenol A (BPA). The properties of the synthesized catalysts were characterized by Brunnaer–Emmett–Teller (BET), X-ray powder diffraction (XRD), X-ray photoelectron spectrometry (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The results indicated that the Fe3O4 MNPs appeared to be roughly spherical shapes and their average size was 10–20nm. The catalytic capacity of MNPs in US+Fe3O4+H2O2 system with different pH conditions, H2O2 concentrations and MNPs doses was investigated. It was found that the OH radicals were promptly generated due to the catalysis of the Fe3O4 MNPs. BPA could be degraded within a wide pH range from 3 to 9, and the degradation efficiencies were remarkably enhanced by ultrasound. The apparent rate constants were 8.31×10−3, 7.96×10−3 and 5.64×10−3min−1, respectively, when the pH values were 3, 7 and 9, respectively. The removal efficiencies of BPA were all over 95%. About half total organic carbon (TOC) in solution was eliminated under neutral condition by sono-Fenton process. Furthermore, the results of stability and reusability demonstrated that the Fe3O4 MNPS were promising in the treatment of wastewater with refractory organics.
In this study, the effects of concentrations 0, 100, 250, 500, 750 and 1000 mg kg−1 of nanoscale zero-valent iron (nZVI) on germination, seedlings growth, physiology and toxicity mechanisms were ...investigated. The results showed that nZVI had no effect on germination, but inhibited the rice seedlings growth in higher concentrations (>500 mg kg−1 nZVI). The highest suppression rate of the length of roots and shoots reached 46.9% and 57.5%, respectively. The 1000mg kg−1 nZVI caused the highest suppression rates for chlorophyll and carotenoids, at 91.6% and 85.2%, respectively. In addition, the activity of antioxidant enzymes was altered by the translocation of nanoparticles and changes in active iron content. Visible symptoms of iron deficiency were observed at higher concentrations, at which the active iron content decreased 61.02% in the shoots, but the active iron content not decreased in roots. Interestingly, the total and available amounts of iron in the soil were not less than those in the control. Therefore, the plants iron deficiency was not caused by (i) deficiency of available iron in the soil and (ii) restraint of the absorption that plant takes in the available iron, while induced by (ⅲ) the transport of active iron from the root to the shoot was blocked. The cortex tissues were seriously damaged by nZVI which was transported from soil to the root, these were proved by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). This current study shows that the mechanism of iron deficiency in rice seedling was due to transport of active iron from the root to the shoot blocked, which was caused by the uptake of nZVI.
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•Higher concentrations of nZVI induced iron deficiency in rice seedlings visibly.•nZVI was taken in rice seedlings and transported form root to shoot.•The pathway of active iron transport from root to shoot was inhibited.•The cortex tissues in root were damaged seriously by nZVI.
Higher concentrations nZVI induced symptoms of iron deficiency in the shoot of rice seedlings due to the inhibition of active iron transporting from root to shoot.
Polybrominated diphenyl ethers have been identified as a new class of organic pollutants with ecological risk due to their toxicity, bioaccumulation, and global distribution. Proper remediation ...technologies are needed to remove them from the environment. In this paper, Ni/Fe bimetallic nanoparticles were synthesized by chemical deposition and used to degrade decabromodiphenyl ether (BDE209). The characteristics of Ni/Fe nanoparticles were analyzed by transmission electron microscopy, X-ray diffractometry, X-ray photoelectron spectroscopy, and Brunnaer–Emmett–Teller surface area analysis. Ni/Fe bimetallic nanoparticles with diameters in the order of 20–50
nm could effectively degrade BDE209 in the solvent (tetrahydrofuran/water). Influence factors, such as Ni/Fe nanoparticle dosage, initial BDE209 concentration, and Ni loading, on the removal of BDE209 were studied. The results indicated that the degradation of BDE209 followed pseudo-first-order kinetics, and the degradation rate of BDE209 increased with increasing the amount of nano Ni/Fe particles, Ni/Fe ratio, and decreasing the initial concentration of BDE209. Through analyzed the mass balance of the BDE209 removal, degradation was the main process of BDE209 removal. The mechanism of debromination was deduced by analyzing the reaction products using gas chromatography–mass spectrometry, the bromide ion in the solution and varying the solvent conditions. Stepwise hydrogen reduction is the main process of debromination, and the hydrion play an important role in the reaction. Moreover, the experiment of long term performance and leaching of Ni were also carried out to test the stability and durability of Ni/Fe nanoparticles in BDE209 degradation.
Due to the rapid development of modern industry, the coexistence of antibiotics and inorganic heavy metals pollutants in wastewater has become a universal phenomenon. Therefore, developing efficient ...and eco-friendly photocatalyst for mixed pollutants degradation is significant. In this work, a well-designed phosphorus and sulfur co-doped g-C3N4 with feeble N vacancies catalyst (P/S-g-C3Nx) was fabricated by supramolecular self-assembly method, and was applied to remove berberine hydrochloride (BH) and Cr(VI) simultaneously with the synergy of adsorption-photocatalysis. A series of experiments was conducted to unveil the synergistic mechanism. The kinetic models indicated that the adsorption of P/S-g-C3Nx improved the BH removal process by accelerating the photo-degradation, because the adsorption rate > surface degradation rate > bulk degradation rate. Besides, the photo-degradation process improved the BH removal rate by regenerating the adsorption sites of P/S-g-C3Nx. Moreover, from the experiments in BH-Cr(VI) mixed solution system, the existence of BH also enhanced the surface adsorption of Cr(VI) in P/S-g-C3Nx sample, and the reduction rate of Cr(VI) was also promoted with the existence of BH. Overall, the results of this investigation suggest that the adsorption-photocatalysis synergy method is an efficient way to eliminate organic pollutant and Cr(VI) simultaneously.
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•P and S doped g-C3N4 with N defects was fabricated via supramolecular self-assembly.•P/S-g-C3Nx showed adsorption-photocatalysis synergy in berberine(BH)-Cr(VI) removal.•The adsorption process improved the BH removal rate by accelerating photodegradation.•The existence of BH enhanced the P/S-g-C3Nx surface adsorption to Cr(VI).•A synergistic mechanism to remove mixed pollutants was proposed.
•Fate and ecotoxicity of Cr species in nZVI-amended soil are reported originally.•CMC-nZVI can significantly reduce the leachability and bioavailability of Cr.•Fe sorption by plants can be enhanced ...by fresh CMC-nZVI but inhibited by aged one.•Complete oxidation of nZVI after use is proposed to improve plants cultivation.
The toxic effect of Cr(VI)-contaminated soil remediated by sodium carboxymethyl cellulose stabilized nanoscale zero-valent iron (CMC-stabilized nZVI) was assessed through in vitro toxicity and phytotoxicity tests. In vitro tests showed that 0.09gL−1 of Fe0 nanoparticles (soil-to-solution ratio was 1g:5mL) significantly reduced the toxicity characteristic leaching procedure (TCLP) leachability and physiological based extraction test (PBET) bioaccessibility of Cr by 82% and 58%, respectively. Sequential extraction procedures (SEP) revealed that exchangeable (EX) Cr was completely converted to Fe–Mn oxides (OX) and organic matter (OM). Accordingly, phytotoxicity tests indicated that after 72-h remediation, Cr uptakes by edible rape and Chinese cabbage were suppressed by 61% and 36%, respectively. Moreover, no significant increase in Cr uptake was observed for either species after a 1-month static period for the amended soil. Regarding Fe absorption, germination and seedling growth, both plant species were significantly affected by CMC-nZVI-exposed soils. However, similar phytotoxicity tests conducted after 1 month showed an improvement in cultivation for both plants. Overall, this study demonstrated that CMC-nZVI could significantly enhance Cr immobilization, which reduced its leachability, bioavailability and bioaccumulation by plants. From a detoxification perspective, such remediation is technologically feasible and shows great potential in field applications.
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•Fe3O4 NPs were synthesized by simple method using steel pickling waste liquor.•Roundly compare characterization study with the Fe3O4 NPs prepared by the well-known method was ...conducted.•Bisphenol A can be effectively eliminated in US+Fe3O4+H2O2 system in neutral pH.•Fe3O4 NPs prepared from waste liquor performed similar good activity and stability with that prepared by reagent.
In this study, Fe3O4 NPs (named as Fe3O4 NPs-PO) were prepared by steel pickling waste liquor to reduce the cost of preparation, and were compared with those obtained by the common co-precipitation method (named as Fe3O4 NPs-CP) which prepared from chemical reagent using BET, XRD, XPS, TEM and SEM techniques. The results indicated that Fe3O4 NPs-PO nanoparticles mainly existed in the form of Fe3O4 and appeared to be roughly spherical in shape with a size range of 20–50nm. The heterogeneous Fenton-like catalytic capacity of Fe3O4 NPs-PO in US+Fe3O4+H2O2 system was comprehensively investigated. BPA could be degraded within a wide pH range of 7–10. The removal efficiencies of BPA were close to 100% and about 45% total organic carbon (TOC) in solution was eliminated at the optimized conditions. It was found that·OH radicals which mainly caused the degradation of BPA were promptly generated due to the catalysis of the Fe3O4 NPs-PO. Furthermore, the comparative study of catalytic activity, stability and reusability between Fe3O4 NPs-PO and Fe3O4 NPs-CP showed that the two catalysts both remained good activity after several reaction cycles and no significant change in composition and structure was observed, the loss of catalyst was negligible, which demonstrated that Fe3O4 NPs-PO were promising in ultrasonic Fenton-like process to treat refractory organics.
The removal of antibiotic metronidazole (MNZ) in aqueous solution by nanoscale zero-valent iron (NZVI) particles was investigated. The experimental results showed that MNZ was completely removed by ...NZVI, MNZ solution at 80
mg L
−
1
was rapidly removed by NZVI within 5
min, at initial solution pH 5.60, NZVI dose of 0.1
g L
−
1
. Influencing factors such as NZVI dosage, initial MNZ concentration and initial solution pH were systematically studied, and the removal process of MNZ followed a pseudo-first order kinetics model. The removal efficiency was enhanced with increasing NZVI dosage while it was decreased with the increase of initial MNZ concentration and initial solution pH. The removal of MNZ in a nitrogen bubbling system (NZVI/N
2 process) and in an air bubbling system (NZVI/air process) was compared, and the results showed that the removal rate in the NZVI/air process was slightly higher than that in the NZVI/N
2 process. The removal efficiencies of MNZ by using NZVI and commercial iron powder were investigated as well, indicating that MNZ removal efficiency by NZVI was about 49 times higher than that by commercial iron powder under the same dosages. This study demonstrates that the NZVI technology could be a promising approach for antibiotic wastewater treatment.
►Antibiotic metronidazole (MNZ) is effectively and rapidly removed by nanoscale Fe
0. ►Dissolved oxygen is probable a key factor for the enhancement of MNZ removal. ►MNZ removal by nanoscale Fe
0 fits well the pseudo-first order kinetics model. ►MNZ removal depends on initial pH value and the dosage of nanoscale Fe
0.
The problem of low adsorption capacity of pristine magnetic biochar for organic pollutants always occurs. It is of great significance to select a suitable method to improve the adsorption performance ...of magnetic biochar. In this study, magnetic biochar was treated by ball milling and tested for its fluconazole adsorption capacity. The maximum adsorption capacity of ball-milled magnetic biochar (BMBC) for fluconazole reached nearly 15.90 mg/g, which was approximately five times higher than that of pristine magnetic biochar (MBC). Fluconazole adsorption by BMBC was mainly attributed to
π
–
π
interactions, hydrogen bonding, and surface complexation with oxygen-containing functional groups. The enhancement in fluconazole adsorption by BMBC was attributed to an increase in oxygen-containing functional groups. Batch adsorption experiments also illustrated that BMBC could be successfully applied in a wide range of pH values. The high efficiency of fluconazole removal confirmed that ball milling was an effective strategy to enhance the adsorptive performance of magnetic biochar.
Polybrominated diphenyl ethers (PBDEs) are commonly used as additive flame retardants in all kinds of electronic products. PBDEs are now ubiquitous in the environment, with soil as a major sink, ...especially in e-waste recycling sites. This study investigated the degradation of decabromodiphenyl ether (BDE209) in a spiked soil using Ni/Fe bimetallic nanoparticles. The results indicated that Ni/Fe bimetallic nanoparticles are able to degrade BDE209 in soil at ambient temperature and the removal efficiency can reach 72% when an initial pH of 5.6 and at a Ni/Fe dosage of 0.03 g/g. A declining trend in degradation was noticed with decreasing Ni loading and increasing of initial BDE209 concentration. The degradation products of BDE209 were analyzed by GC-MS, which showed that the degradation of BDE209 was a process of stepwise debromination from nBr to (n-1)Br. And a possible debromination pathway was proposed. At last, the degradation process was analyzed as two-step mechanism, mass transfer and reaction. This current study shows the potential ability of Ni/Fe nanoparticles to be used for removal of PBDEs in contaminated soil.
