Tannic acid promotes the activation of persulfate with Fe(ii) for highly efficient trichloroethylene removal.

Trichloroethylene (TCE) is an Environmental Protection Agency (EPA) priority pollutant that is difficult to be removed by some remediation methods. For instance, TCE removal using persulfate (PS) activated by ferrous iron (Fe(ii)) has been tested but is limited by the unstable Fe(ii) concentration and the initial pH of contaminated water samples. Here we reported a new TCE removal system, in which tannic acid (TA) promoted the activation of PS with Fe(ii) (TA-Fe(ii)-PS system). The effect of initial pH, temperature, and concentrations of PS, Fe(ii), TA, inorganic anions and humic acid on TCE removal was investigated. We found that the TA-Fe(ii)-PS system with 80 mg L-1 of TA, 1.5 mM of Fe(ii) and 15 mM of PS yielded about 96.2-99.1% TCE removal in the pH range of 1.5-11.0. Radical quenching experiments were performed to identify active species. Results showed that SO4˙- and ˙OH were primarily responsible for TCE removal in the TA-Fe(ii)-PS system. In the presence of TA, the Fe-TA chelation and the reduction of TA could regulate Fe(ii) concentration and activate persulfate for continuously releasing reactive species under alkaline conditions. Based on the excellent removal performance for TCE, the TA-Fe(ii)-PS system becomes a promising candidate for controlling TCE in groundwater.

[Ecological Risk Assessment and Source Apportionment of Heavy Metals in Mineral Resource Base Based on Soil Parent Materials].

Mineral resource bases have dual properties, e.g., mineral resources and environmental pollution. The latter could be classified into natural and anthropogenic pollution based on identifying the spatial distribution characteristics and sources of heavy metals in the soil. The Hongqi vanadium titano-magnetite mineral resources base in Luanping County, Luanhe watershed, was taken as the research object. The geo-accumulation index (Igeo), Nemerow comprehensive pollution index (PN), and potential ecological risk (Ei) were utilized to assess the soil heavy metal pollution characteristics, and redundancy analysis (RDA) and positive determinate matrix factorization (PMF) were employed to identify sources of the soil heavy metals. The results revealed that the mean contents of Cr, Cu, and Ni in the parent material of medium-basic hornblende metamorphic rock and medium-basic gneisses metamorphic rock were 1-2 times that in other parent materials in the concentrated area of mineral resources. However, the mean contents of Pb and As were lower. Fluvial alluvial-proluvial parent materials had the highest mean content of Hg, and the mean content of Cd was higher in the parent materials of medium-basic gneisses metamorphic rocks, acid rhyolite volcanic rocks, and fluvial alluvial-proluvial facies. The Igeodecreased in the following order:Cd>Cu>Pb>Ni>Zn>Cr>Hg>As. PN ranged from 0.61 to 18.99, and the sample proportion of moderate and severe pollution reached 10.00% and 8.08% respectively. Pishowed that the contents of Cu, Cd, Cr, and Ni were relatively higher in the parent material of intermediate-basic hornblende metamorphic rocks and intermediate-basic gneiss metamorphic rocks. Ei decreased in the order of Hg(58.06)>Cd(39.72)>As(10.98)>Cu(6.56) >Pb(5.60)>Ni(5.43)>Cr(2.01)>Zn(1.10). Samples whose RI was lower than 150 accounted for 84.27%, showing that the research area was predominantly at a slight potential ecological risk level. The sources of soil heavy metals were dominated by parent material weathering, followed by the mixed sources of agricultural activities and transportation, the exploitation of mining, and fossil burning, which accounted for 41.44%, 31.83%, 22.01%, and 4.73%, respectively. The risks of heavy metal pollution in the mineral resource base were characterized as multi-source instead of the single source from the mining industry. These research results provide the scientific basis for regional green mining development and eco-environmental protection.