Zero valent iron or Fe3O4-loaded biochar for remediation of Pb contaminated sandy soil: Sequential extraction, magnetic separation, XAFS and ryegrass growth.

In this study, the feasibility of using zero-valent iron (ZVI) and Fe3O4-loaded biochar for Pb immobilization in contaminated sandy soil was investigated. A 180-day incubation study, combined with dry magnetic separation, chemical extraction, mineralogical characterization, and model plant (ryegrass, namely the Lilium perenne L.) growth experiment was conducted to verify the performance of these two materials. The results showed that both amendments significantly transferred the available Pb (the exchangeable and carbonates fraction) into more stable fractions (mainly Fe/Mn oxides-bound Pb), and ZVI alone showed a better performance than the magnetic biochar alone. The magnetic separation and extended X-ray absorption fine structure (EXAFS) analysis proved that Fe (oxyhydr)oxides on aged ZVI particles were the major scavengers of Pb in ZVI-amended soils. In comparison, the reduced Pb availability in magnetic biochar-amended soil could be explained by the association of Pb with Fe/Mn (oxyhydr)oxides in aged magnetic biochar, also the possible precipitation of soil Pb with soluble anions (e.g. OH-, PO43-, and SO42-) released from magnetic biochar. ZVI increased ryegrass production while Fe3O4-loaded biochar had a negative effect on the ryegrass growth. Moreover, both markedly decreased the Pb accumulation in aboveground and root tissues. The simple dry magnetic separation presents opportunities for the removal of Pb from soils, even though the efficiencies were not high (17.5% and 12.9% of total Pb from ZVI and biochar-treated soils, respectively). However, it should be noted that the ageing process easily result in the loss of magnetism of ZVI while the magnetic biochar tends to be more stable and has high retrievability during the dry magnetic separation application.

Effect of Different Lead and Cadmium Salts on the Photolytic Degradation of Two Typical Fluoroquinolones under Natural Sunlight Irradiation.

This study investigated the effects of different lead and cadmium salts (Pb(NO3)2, Cd(NO3)2, PbCl2, and CdCl2) on the photolytic degradation of two typical fluoroquinolones (levofloxacin (LVF) and norfloxacin (NOR)) under natural sunlight irradiation. Their half-life time and photolytic kinetic constants (k) were calculated at different molar ratios. The results indicated that the photolytic degradation curves of LVF and NOR followed apparent first-order kinetics. After 42 days of sunlight irradiation, approximately 48.3-69.4% of NOR was decomposed when the initial concentration increased from 0.006 to 0.06 mmol/L. In comparison, only 9.8-43.4% of LVF was decomposed. The k of NOR ranged from 0.79 × 10-3 to 1.30 × 10-3 h-1, and the k of LVF increased from 6.82 × 10-4 to 1.61 × 10-4 h-1. Compared with the control, the Pb2+ and Cd2+ participation tended to enhance the LVF and NOR photodegradation. The effects of Cd2+ on the photodegradation efficiency were more significant than those of Pb2+. It was inferred that the presence of aqueous NO3- obviously suppressed the NOR degradation, but Cl- had slight effects on these two fluoroquinolones' photodegradation. These results are of importance toward the understanding of the persistence of FQs under natural sunlight irradiation in surface waters.

[Photodegradation of Ciprofloxacin Hydrochloride in the Aqueous Solution Under UV].

Effects of ciprofloxacin hydrochloride (CIP) initial concentration, Pb (NO3) 2, Cd (NO3) 2, PbCl2 and CdCl2 on the photodegradation of CIP using UV irradiation were investigated. The experiments results showed that UV irradiation could lead to effective removal of CIP, but there was no CIP degradation in dark. The photodegradation rate of CIP reduced with increasing initial concentration under UV irradiation. Pb(NO3)2 and Cd(NO3)2 (except for the experiment group of 0.006 mmol x L(-1)) could enhance CIP photodegradation, and the half-life of CIP gradually increased with increasing molar ratio between heavy metal and CIP ( with the decreasing concentration of nitrate). With increasing molar ratio (with the decreasing concentration of chlorate), PbCl2 and CdCl2 first promoted and then inhibited the CIP photodegradation.

Adsorptive Removal and Adsorption Kinetics of Fluoroquinolone by Nano-Hydroxyapatite.

Various kinds of antibiotics, especially fluoroquinolone antibiotics (FQs) have been widely used for the therapy of infectious diseases in human and livestock. For their poorly absorbed by living organisms, large-scale misuse or abuse of FQs will foster drug resistance among pathogenic bacteria, as well as a variety of environmental problems when they were released in the environment. In this work, the adsorption properties of two FQs, namely norfloxacin (NOR) and ciprofloxacin (CIP), by nano-hydroxyapatite (n-HAP) were studied by batch adsorption experiments. The adsorption curves of FQs by n-HAP were simulated by Langmuir and Freundlich isotherms. The results shown that NOR and CIP can be adsorbed effectively by the adsorbent of n-HAP, and the adsorption capacity of FQs increase with increasing dosage of n-HAP. The optimum dosage of n-HAP for FQs removal was 20 g · L(-1), in which the removal efficiencies is 51.6% and 47.3%, and an adsorption equilibrium time is 20 min. The maximum removal efficiency occurred when pH is 6 for both FQs. The adsorption isotherm of FQs fits well for both Langmuir and Freundlich equations. The adsorption of both FQs by n-HAP follows second-order kinetics.

[Natural attenuation of tetracycline in the water of Taihu Lake under different environmental conditions].

Tetracycline (TC) has been widely used in veterinary medicines and disease treatments, and has been discharged into nature system due to manure application. To know the harmfulness of TC residues, and to investigate the natural attenuation of TC under different environmental conditions, simulated attenuation experiments in the presence of light, sediment, Cd (NO3) 2 and Pb(NO3)2 were performed. Results showed that the natural attenuation of TC was not obvious under the sunlight, and the natural attenuation rate of TC in water with unsterilized sediment was greater than that with sterilized sediment. The natural attenuation of TC in water with Pb(NO3)2 was slow at the first stage of the experiment, and progressively speeded up as time went on. However, the natural attenuation of TC in water with Cd(NO3)2 was more rapid at the beginning, and significantly faster than that of Pb(NO3)2. The natural attenuation rates of 0.08 mmol x L(-1) TC under different conditions follow the sequence: unsterilized sediment (87.2%) > sterilized sediment (70.37%) > Cd(NO3)2 (64.2%) > Pb(NO3)2 (32.3%) > blank (6.6%), suggesting that all these factors can promote the natural attenuation of TC. Though the natural attenuation trend under different conditions in the dark is similar to that under the sunlight, the natural attenuation rate is less than that under the sunlight, which implicates that sunlight may promote the natural attenuation of TC.