•Ring-opening of BDE209 was realized by the Fe0@Fe3O4 in the reduction-oxidation system.•A two-stage reduction/subsequent oxidation degradation mechanism was proposed.•The reduction ability of nZVI was efficiently supported by Fe3O4 which acted as a catalyst.•OH generated on the composite surface and solution attacked the debromination products.The magnetic Fe0@Fe3O4 nanocomposite was prepared and used to achieve the reductive/subsequent oxidative ring-opening of decabromodiphenyl ether (BDE209) in this work. The characterization results indicated that the structure of the composite consisted of small nanoscale zero-valent iron (nZVI) particles surrounding the surface of Fe3O4 nanoparticle (NP). A 100% removal efficiency and 80% degradation efficiency of BDE209 was reached by the composite accompanied with ultrasound(called NP/US system) for 36 h, which is higher than that obtained with conventional nZVI particles. Furthermore, the enhanced debromination and ring-opening of BDE209 was realized by a Fenton-like degradation process lasting for 12 h after the addition of H2O2 to the NP/US reaction at 36 h. Based on the degradation products identified, a two-stage reduction/oxidation degradation mechanism was proposed. During the first stage, which was reductive debromination, the major reductive activity of nZVI was efficiently enhanced in the presence of nano Fe3O4, which served as a catalyst to improve the stability of the nZVI nanoparticles and accelerate electron transfer, enhancing the degradation efficiency of BDE209. During the second stage, the oxidative ring-opening, the debromination products of BDE209 were proved to be attacked by abundant hydroxyl radicals generated both in the solution and on the surface of the Fe0@Fe3O4 nanoparticles. Thus, this work provides an efficient method to achieve the complete ring-opening of PBDEs using iron-based nanomaterials.Download high-res image (164KB)Download full-size image

•Fe NPs were successfully synthesized using Eichhornia crassipes leaf extracts by single-step.•Fe NPs were used for the removal of Cr(VI).•89.9% of Cr(VI) was removed using Fe NPs.•A removal mechanism for Cr(VI) was proposed which involved adsorption and reduction.Eichhornia crassipes (water hyacinth), a species of invasive weeds has caused serious ecological damage due to its extraordinary fertility and growth rate. However, it has not yet been exploited for use as a resource. This paper reported the synthesis and characterization of amorphous iron nanoparticles (Ec-Fe-NPs) from Fe(III) salts in aqueous extracts of Eichhornia crassipes. The nanoparticles were characterized by SEM, EDS, TEM, XPS, FTIR, DLS and the zeta potential methods. The characterization results confirmed the successful synthesis of amorphous iron nanoparticles with diameters of 20–80 nm. Moreover, the nanoparticles were mainly composed of zero valent iron nanoparticles which were coated with various organic matters in the extracts as a capping or stabilizing agents. Batch experiments showed that 89.9% of Cr(VI) was removed by the Ec-Fe-NPs much higher than by the extracts alone (20.4%) and Fe3O4 nanoparticles (47.3%). Based on the kinetics study and the XPS analysis, a removal mechanism dominated by adsorption and reduction with subsequently co-precipitation was proposed.The green synthetic Fe nanoparticles(Ec-Fe-NPs) were prepared using Eichhornia crassipes (water hyacinth) leaf extracts as reductants and stabilizing agents to reduce iron(III) to form zero-valent iron nanoparticles (Ec-Fe-NPs), and then the mechanism were studied that Cr(VI) were removed by Ec-Fe-NPs.Download high-res image (137KB)Download full-size image

•Biochar-supported iron phosphate nanoparticle was synthesised.•The composite could effectively immobilise Cd in soil.•The composite could inhibit Cd uptake to the cabbage mustard.A type of biochar-supported iron phosphate nanoparticle stabilised by a sodium carboxymethyl cellulose (CMC@BC@ Fe3(PO4)2) composite was synthesised to remediate cadmium (Cd)-polluted soil. The surface morphology and functional groups of the composite were characterised by scanning electron microscopy and Fourier transform infrared spectrometry, respectively. Batch experiments showed that the composite (soil-to-solution ratio 1 g:10 mL) could effectively immobilise Cd in soil. The immobilisation efficiency of Cd was 81.3% after 28 days of remediation, and physiological-based extraction test bioaccessibility was reduced by 80.0%. The results of sequential extraction procedures indicated that the transformation from more easily extractable Cd to the least available form was responsible for the decrease in Cd bioavailability in soils. Plant growth experiments proved that the composite could inhibit Cd uptake to the belowground and aboveground parts of cabbage mustard by 44.8% and 70.2%, respectively, thus promoting cabbage mustard growth and development after remediation.Download high-res image (77KB)Download full-size image

This paper was aimed to study the impact of “ageing” (aged in non-saturated soil for 2 and 4 weeks prior to exposure) nanoscale zero-valent iron (nZVI) on the terrestrial plant. The effects of nZVI on Oryza Sativa germination, seedlings growth, chlorophyll biosynthesis, oxidative stress and the activities of antioxidant enzymes at low (250 mg/kg) and high (1000 mg/kg) concentrations were investigated in this study. The results showed that neither the freshly added nor the “ageing” nZVI to the soil had a significant effect on germination, regardless of concentration. At the low concentration, the freshly added nZVI had no visible toxic effects on the rice seedlings growth, but the rice seedlings exhibited obvious toxic symptoms at the high concentration. At the high concentration, toxicity effects of nZVI were reduced after aging with 2 and 4 weeks in soils compared to fresh nZVI, but the “ageing” nZVI continued to significantly inhibit the rice seedlings growth compared with the control, and the inhibition rates of 2 and 4-week-old nZVI were not significantly different. The mechanism of ageing decreased the phytotoxicity of nZVI was due to nZVI particles incomplete oxidation, and some of which had remained in the soil after 4 weeks aged.

To reduce costs and improve practicability, an ion imprinted magnetic chitosan (IMCS) was synthesized through co-precipitation using steel pickling waste liquor and chitosan and Cu(II) as template ions, which was then characterized by TEM, SEM, EDX, FTIR, XRD and VSM. The batch experiments were carried out for its potential application and high selectivity of Cu(II) removal, which were observed due to the paramagnetic properties and coordination reactions in the imprinted cavities. Kinetic studies revealed that the adsorption process followed a pseudo second-order model and the equilibrium data fit perfectly with the Langmuir isotherm model. The maximum adsorption capacity was 109.89 mg g−1. Negative values for ΔH0 and ΔG0 indicated an exothermic and spontaneous adsorption process. The adsorption process was found to be a chemical reaction and coordination complexes were formed between the metal ions and the groups of chitosan binding mainly in the “bridge model”. Moreover, 0.2 mol L−1 HCl solution was considered as the most appropriate eluent for regeneration. It showed a great performance in the experiments for practical copper wastewater and the process was considerably cost-effective.

As a promising in situ remediation technology, nanoscale zero-valent iron (nZVI) can remove polybrominated diphenyl ethers such as decabromodiphenyl ether (BDE209) effectively, However its use is limited by its high production cost. Using steel pickling waste liquor as a raw material to prepare nanoscale zero-valent metal (nZVM) can overcome this deficiency. It has been shown that humic acid and metal ions have the greatest influence on remediation. The results showed that nZVM and nZVI both can effectively remove BDE209 with little difference in their removal efficiencies, and humic acid inhibited the removal efficiency, whereas metal ions promoted it. The promoting effects followed the order Ni2+>Cu2+>Co2+ and the cumulative effect of the two factors was a combination of the promoting and inhibitory individual effects. The major difference between nZVM and nZVI lies in their crystal form, as nZVI was found to be amorphous while that of nZVM was crystal. However, it was found that both nZVM and nZVI removed BDE209 with similar removal efficiencies. The effects and cumulative effects of humic acid and metal ions on nZVM and nZVI were very similar in terms of the efficiency of the BDE209 removal.

•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 20–50 nm. 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.

•A novel nanocomposite called BC@Fe/Ni was synthesized in cost-effective method.•Nitrate and secondary pollution was completely removed by BC@Fe/Ni.•Biochar can disperse nanoparticles and prevent iron and nickel pollution.In this study, a novel bimetallic iron/nickel nanoparticles supported on biochar (BC@Fe/Ni) was established to degrade nitrate pollution in water. The nanocomposite was prepared from steel pickling waste liquor and sugarcane bagasse, which are made at low cost. The particle sizes of the nanocomposite ranged from about 10 nm to 20 nm and its specific surface area (59.83 m2/g) was about 71% bigger than that of nanoscale zero valent iron prepared from steel pickling waste liquor (S-NZVI), which proved that biochar had an excellent dispersal effect on bimetallic iron/nickel particles. Without controlling the pH, high nitrate removal rates over 93% could be realized in nitrate concentrations below 50 mg/L. The results of batch experiments demonstrated that the kinetics curves fitted the pseudo-first-order reaction well. And it was also found that higher dosages of the nanocomposite, lower initial nitrate concentrations, and acid medium facilitated nitrate degradation. In addition, the observed pseudo-first order rate coefficient in nitrate (20 mg/L) degradation rate by 4 g/L of the bimetallic iron/nickel supported on biochar was 30% faster than that by 2 g/L the bimetallic iron/nickel nanoparticles, due to the existence of biochar. And it was 75% faster than that by 2 g/L the nanoscale zero valent iron due to the existence of both biochar and the nanoscale zero valent nickel catalyst. Furthermore, iron and nickel ion pollution occurred in the denitrification system with bimetallic iron/nickel nanoparticles but not in that with the bimetallic iron/nickel nanoparticles supported on biochar, due to the biochar’s adsorption. After denitrification by the bimetallic iron/nickel nanoparticles supported on biochar, most of nitrate turned into ammonia (17.04 mg/L) and there only was a small amount of nitrite (0.024 mg/L) with high nitrate removal rate (99.5%). And most of ammonia can be absorbed by cation exchange resin with finial ammonia concentration of 0.58 mg/L. At last, the concentrations of nitrate (0.24 mg/L), nitrite (0.021 mg/L), and total nitrogen (0.84 mg/L) were lowest in the nanocomposite system. Overall, the bimetallic iron/nickel nanoparticles supported on biochar exhibited clear advantages over bimetallic iron/nickel nanoparticles and nanoscale zero valent iron with respect to degrading nitrate efficiently, preventing iron and nickel pollution and removing ammonia pollution in combination with cation exchange resin.