解磷菌改性生物炭去除水中铀(Ⅵ)的效能与机理

Efficiency and mechanism of phosphorus solubilizing bacteria modified biochar for uranium(Ⅵ)removal from aqueous solution

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。采用SEM、EDS、TEM、XRD、FTIR、XPS、BET对样品进行了表征。结果表明,PMBC改性24 h制得的生物炭(PMBC+PSB24)去除U(Ⅵ)效果最佳,其内壁孔洞明显增多,其比表面积和总孔体积相较PMBC分别增加了88.1%和40.8%。当温度为30℃、pH为4、U(Ⅵ)初始质量浓度10 mg/L、PMBC+PSB24投加量0.02 g/L时,PMBC+PSB24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533.078 mg/g,相较PMBC对水中U(Ⅵ)去除率提升26.97%,吸附过程符合Freundlich等温模型与拟二级动力学模型。PMBC+PSB24表面和菌体内部均出现放射状晶体,该晶体为变钾铀云母[K(UO_(2))(PO_(4))·3H_(2)O],其表面官能团丰度较PMBC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较新鲜改性生物炭仅下降8.90%,具有良好的再生性能。

Modified biochar(PMBC+PSB)was synthesized from phosphorus solubilizing bacteria(PSB)modification of pig manure biochar(PMBC),and its performance and mechanism on U(Ⅵ)removal from water were analyzed.The samples obtained were characterized by SEM,EDS,TEM,XRD,FTIR,XPS and BET.The results showed that the biochar(PMBC+PSB24),prepared with 24 h of PMBC modification,displayed the best U(Ⅵ)removal effect.Compared with PMBC,biochar(PMBC+PSB24)exhibited significantly increased pore structure in its inner wall and an increment in the specific surface area as well as total pore volume by 88.1%and 40.8%,respectively.Under the conditions of temperature 30℃,pH 4,U(Ⅵ)initial mass concentration 10 mg/L,and dosage of PMBC+PSB240.02 g/L,the removal rate of U(Ⅵ)in water by PMBC+PSB24 could reach 99.46%,and the maximum adsorption capacity of PMBC+PSB24 for U(Ⅵ)in water was 533.078 mg/g,26.97%higher than that of PMBC.The adsorption process was in accordance with the Freundlich isothermal model and the proposed secondary kinetic model.Radial crystals,which were metasuranite[K(UO_(2))(PO_(4))•3H_(2)O],were found on the surface and inside the bacterium of PMBC+PSB24.The abundance of surface functional group was higher than that of PMBC,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 8.90%,showing good regeneration performance.