Huosheng Li

Simultaneous removal of thallium and chloride from a highly saline industrial wastewater using modified anion exchange resins

Simultaneous removal of thallium (Tl) and chloride from a highly saline industrial wastewater was investigated using modified anion ion exchange resins. The removal of thallium was mainly driven by the exchange of Tl-chlorocomplex (TlCl4-) formed in the oxidation of thallous (Tl (I)) to thallic ion (Tl (III)) by hydrogen peroxide (H2O2) under saline conditions. Over 97% of thallium and chloride removal was achieved using the modified resins, with a wide optimal conditions found to be H2O2 dosage 1.0-25.0mL/L, pH 1.6-4.3, and flow rate 0.5-4.7mL/L. The modified resins had an exchange capacity of 4.771mg Tl/g dry resins for thallium and 1800mg Cl/g dry resins for chloride. Stable regeneration could be achieved with the modified resins: over 97% of thallium and 90% of chloride can be eluted using Na2SO3 solution and alternating hot (60°C) H2SO4 and cold (25°C) water, and over 98% removal of thallium and chloride was achieved after five consecutive regeneration cycles.

Removal of thallium from aqueous solutions using Fe-Mn binary oxides

In this study, Fe-Mn binary oxides, which harbor the strong oxidative power of manganese dioxide and the high adsorption capacity of iron oxides, were synthesized for Tl(I) removal using a concurrent chemical oxidation and precipitation method. The adsorption of Tl onto the Fe-Mn adsorbent was fast, effective, and selective, with equilibrium sorption reaching over 95% under a broad operating pH (3-12), and high ionic strength (0.1-0.5mol/L). The adsorption can be well fitted with both Langmuir and Freundlich isotherms, and the kinetics can be well described by the pseudo-second-order model. Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) spectra suggest that surface complexation, oxidation and precipitation were the main mechanisms for the removal of Tl. This study shows that the Fe-Mn binary oxides could be a promising adsorbent for Tl removal.

Historical trends and ecological risks of polybrominated diphenyl ethers (PBDEs) and alternative halogenated flame retardants (AHFRs) in a mangrove in South China

While the production of polybrominated diphenyl ethers (PBDEs) was gradually phased out in the last decade, they may still pose hidden danger to the environment due to their toxicity and persistence. On the other hand, alternative halogenated flame retardants (AHFRs) have been increasingly used as substitutes for PBDEs and may further worsen environmental health. To determine the environmental impact of PBDEs and AHFRs, we examined the historical trends and ecological risks of PBDEs and AHFRs in a typical industrialized city in South China by measuring their concentrations in mangrove sediment. Results showed that the concentrations of PBDEs increased abruptly from 1997 to 2009 due to the use of commercial deca-BDE mixture, but were stabilized in recent years. The concentrations of AHFRs, mainly contributed by decabromodiphenyl ethane (DBDPE), kept increasing from 1997 onwards. Based on the temporal trends, DBDPE is predicted to be predominant over BDE 209 in future. Despite the observed similar concentration between BDE 209 and DBDPE, the former posed a high ecological risk, while the ecological risk of the latter was negligible. Therefore, more attention is required to manage the contamination of BDE 209 in the environment.

Simultaneous Removal of Thallium and EDTA by Fenton Process

The wastewater containing heavy metals and organic pollutants is widely discharged from industries. Because of the coexistence of heavy metals and organic pollutants, the treatment of such wastewater is very difficult. Fenton process is considered to be one of the most effective approaches for the degradation of organic pollutants in aqueous solution due to the strong oxidative ability of hydroxyl radical which generated from the Fenton process. Apart from this, heavy metals are able to be removed during Fenton process owning to the synergic effect of coagulation and precipitation. In this work, pollutants of thallium and EDTA were successfully removed via the Fenton process. A series of single-factor experiments were designed and performed to achieve an optimal reaction conditions for the removal of both thallium and EDTA. Results showed that the removal efficiencies of thallium and TOC could be as high as 96.54% and 70.42%, respectively. The outcomes from our study demonstrate that Fenton process is a promising method for the purification of wastewater containing thallium and EDTA.

Preliminary results of spatial distribution of uranium and thorium in soil profi les near a uranium industrial site, Guangdong province, China

Abstract Four soil profiles were collected from locations with different distances (5, 50, 250 and 1000 m) from a uranium mill tailings dam, Guangdong province, China, to investigate the pollution status of the soil in mining/milling-related areas based on the contents of uranium (U) and thorium (Th), thus to understand the impacts of uranium industrial activities to the surroundings. The U and Th concentrations were determined by inductively coupled plasma mass spectrometry (ICP-MS) after conventional HF-HNO3-HClO4 digestion procedures. The results indicate that the soils within 50 m from uranium tailing were severely contaminated; those in 250 and 1000 m soil samples were observed to be with local background level even though these in 250 m had slightly higher U/Th ratios. Uranium concentrations varied from 5.50 ± 0.27 to 160.55 ± 8.03 mg/kg, with maximum values recorded in an intermediate layer of the 5-m distance soil profile. In comparison, the concentration of Th ranged from 6.02 ± 0.30 to 84.71 ± 4.24 mg/kg, with maximum values observed in the top layer of the 1000-m distance soil profile. The U/Th ratio varied from 0.15 to 11.99 compared with 0.20, 0.22 and 0.26 of the average for Guangdong province, national China and the world, respectively. The mean U/Th of four soil profiles showed a reduction with distance from the uranium mill tailing dam, suggesting the relatively large magnitude of uranium elevation in soils within limited distances.