Enhanced surface Fenton degradation of BPA in soil with a high pH.

Although the heterogeneous Fenton process of iron-bearing minerals has been widely studied due to its potential use for the removal of organic pollutants, the transformation mediated by Fe species in soil particles remains poorly understood. Here, we compared the removal of bisphenol A (BPA) from soil using a Fenton system at low and high pH values. At low pH value, the BPA removal rate decreased with increasing pH value; this result was consistent with the amount of soluble Fe(II) and surface-bound Fe(II) observed in the soil systems. In contrast, an increased BPA degradation efficiency was observed at high pH, which is different from the traditional Fenton system. The electron spin resonance analysis verified that the high BPA degradation rate was attributed to enhanced ·OH generation. The binding environments of the Fe species in the soil for different reaction pH values were investigated by using Mössbauer spectroscopy combined with selective chemical extraction. A mixed-valence Fe(II) phase was observed at pH 12.0 and accounted for 12% of the total Fe content. The results indicate that in addition to the well-studied soluble Fe(II) and surface-bound Fe(II), structural Fe(II) located in the newly formed secondary precipitates may play a more important role in the generation of ·OH, especially at high pH values. These findings may provide insights into the utilization of Fe-bearing soil minerals as a renewable source for the degradation of organic pollutants over a wide pH range.

[Determination of trace chromium in rock samples by graphite furnace-AAS after microsphere phase separation extraction].

A new method for the determination of trace chromium in geological samples by graphite furnace atomic absorption spectrometry (GFAAS) with microsphere phase separation extraction was developed. With the existence of cosolvent of ethanol and solvent of 1-amylalcohol, the diphenylcarbazide reacted with Cr to form a complex in a homogenous phase. Then the complex was separated out with microsphere from the homogenous phase after a little water was added in the system. The operating conditions for phase separation and the heating program of graphite furnace were experimented and optimized. The interference of co-existent ions was studied. The results indicated that the microsphere phase separation extraction can be used to separate and extract the analyte, and also the microsphere can be used as the matrix modifier in the heating program of graphite furnace. As the cosolvent, the dosage of ethanol was about 0.2-0.5 times of the volume of water with the existence of 0.2-1.5 mL 1-amylalcohol. Under the optimum conditions, the linear range of the method was 0-10 microg x L(-1) and the detection limit was 0.057 microg x L(-1) with the relative standard deviation (RSD) of 3.3% (n=11). The concentration factor was 10 with 15 mL of water and 1.5 mL of 1-amylalcohol. The method has been applied to determine the concentration of Cr in geological samples and the analytical results are in agreement with the certified values.