解磷菌改性生物炭去除水中U(Ⅵ)的效能与机理

Efficiency and mechanism of phosphorus solubilizing bacteria modified biochar to fix uranium (Ⅵ) in aqueous solution

摘要:

采用解磷菌(PSB)对猪粪生物炭(PMBC)改性制得改性生物炭(PMBC+PSB)，探讨了其对水中U(Ⅵ)的去除效果与作用机制。研究结果表明， PMBC改性24 h制得生物炭(PMBC+PSB24)的除U(Ⅵ)效果最佳，改性后生物炭内壁孔洞明显增多，BET结果测定PMBC+PSB24比表面积和总孔体积相较改性前分别增加了88.1%和39.7% 。当温度为30 ℃，pH值为4， U(Ⅵ)初始质量浓度10.00 mg/L，PMBC+PSB24投加量0.20 g/L时，其对水中U(Ⅵ)去除率达99.46%。PMBC+PSB24对水中U(Ⅵ)最大吸附容量达555.19 mg/g，相较未改性的提升24.44%，吸附过程符合Freundlich 等温模型与拟二级动力学模型。SEM、TEM表征结果显示，PMBC+PSB24表面和菌体内部均出现放射状晶体，XRD结果表明该晶体为变钾铀云母[K(UO2)(PO4)·3H2O]。FTIR、XPS结果表明，PMBC+PSB24表面官能团丰度提高，参与吸附的主要为羟基和磷酸基团。改性生物炭主要的除U(Ⅵ) 机理为表面络合和矿化沉淀。经过5次吸附-解吸循环后改性生物炭的吸附量仅下降9.4%，具有良好的再生性能。

Abstract:

The modified biochar (PMBC+PSB) was produced by modifying pig manure biochar (PMBC) with phosphorus solubilizing bacteria (PSB), and its effect and mechanism of action on U(Ⅵ) removal in water were investigated. The results showed that the biochar modified with PMBC for 24 h(PMBC+PSB24) had the best effect on U(Ⅵ) removal, and the pores in the inner wall of the modified biochar were significantly increased, and the specific surface area and total pore volume of PMBC+PSB24 increased by 88.1% and 39.7%, respectively, compared with those before modification. The maximum adsorption capacity of PMBC+PSB24 for U(Ⅵ) in water was 555.19 mg/g, which was 24.44% higher than that of unmodified U(Ⅵ). The adsorption process was in accordance with the Freundlich isothermal model and the proposed secondary kinetic model. SEM and TEM characterization results showed that PMBC+PSB24 showed radial crystals on the surface and inside the bacterium, and the XRD results indicated that the crystals were metasuranite [K(UO2)(PO4)·3H2O].FTIR and XPS results showed that the abundance of functional groups on the surface of PMBC+PSB24 increased, and the main groups involved in adsorption were hydroxyl and phosphate groups. The main U(Ⅵ) removal mechanism of modified biochar was surface complexation and mineralization precipitation. After five adsorption-desorption cycles, the adsorption capacity of the modified biochar only decreased by 9.4%, which had good regeneration performance.