聚磷菌协同生物炭对水中U(VI)的去除特性及机理研究

Performance and mechanism of U(VI) adsorption via the phosphorus-accumulating bacteria burdened biochar

低浓度含铀废水中铀的高效去除是铀矿冶安全生产过程中亟待解决的问题。生物吸附法是处理较低浓度重金属废水的高效廉价的方法之一。采用生物炭负载聚磷菌,制备了一种新型吸附剂,通过对比分析普通生物炭与负载聚磷菌生物炭对水中U（VI）的去除特性,结合BET、SEM及XPS等检测手段,考察聚磷菌对生物炭去除水中U（VI）的协同作用,探究低浓度铀废水处理新方法。结果表明,通过负载聚磷菌,生物炭能够快速降低水中U（VI）的浓度,去除率可达99.86%。BET及SEM表征手段表明,聚磷菌被固定在生物炭表面,负载聚磷菌的生物炭比表面积大大减小,但对铀的去除率反而增加。结合XPS结果可知,吸附后沉淀产物为四价铀和六价铀的混合物,表明聚磷菌对水中铀进行了还原、微沉淀,具有协同生物炭除铀作用。吸附动力学试验表明,该吸附过程符合准二级动力学模型;Freundlich吸附等温线模型能更好地描述吸附剂对铀的吸附行为。

The present paper is concerned about the treatment of low concentration uranium water,which remains a great bottleneck of the uranium mining safety and operation. To solve the bottleneck problem,the author of this paper seeks to prepare for a novel bio-trapping agent in hoping to find a new approach to treating the sewage of uranium with low content concentration rate of the bio-absorption by means of biological materials as adsorbents,especially,for those with low content concentration rate of uranium. For the said purpose,it is necessary to make an investigation of the influence of the p H value,temperature,adsorbent dosage,and the contact time on the U（ VI） adsorption via the static testing. Moreover,we have also made a penetrating analysis of the synergetic effect of uranium under the aerobic conditions via the purified indigenous bacteria through comparison. And,simultaneously,we have also expounded the adsorption mechanism by means of BET,SEM,and XPS. Thus,the comparison we have made above proves that the maximum removal rate of U（ VI） over the treatment ranges as has been found through the investigation of the phosphorus-accumulating bacteria biochar can be made to reach high up to 99. 86%,on the condition that,when the initial concentration of U（ VI） remains 10 mg/L,with the p H value being 3. 5（ range 2. 5 to 7. 5） at the temperature of 30 °C（ 15-45 °C）. It implies that the adsorption rate of U（ VI） can be enhanced at presence of the phosphorus-accumulating bacteria,whereas the adsorption mechanism can be elucidated by means of the application of BET and SEM and XPS. Besides,the adoption of SEM helps to gain the effect of the phosphorus-accumulative bacteria on the surface of the biochar. In addition,there can be existing bigsized round precipitates away from the cells,with most of the small particles distributed on the cell surfaces. To the phenomenon,a plausible explanation as is supported by BET,is that the cell surface of the microorganisms plays a significant role in the precipitation process not only as a carrier of the functional groups but also as a substrate inducing the nucleation of the phosphate nanoparticles. As is shown in the XPS measurements,the content rate of U（ IV） and U（ VI） through U（ VI） adsorption by the phosphorus-accumulating bacteria burdened biochar may account for 13% and 87%,respectively,which suggests that the uranium content has been removed through reduction and precipitation. In addition,kinetics analysis also suggests that the adsorption rate of U（ VI） upon the synthesized bio-charcoal can be regarded as a pseudo-second order equation with the adsorption isotherm well represented by the Freundlich isotherm model.