Yu Guanlong

Numerical simulation for volatile organic compound removal in rotating drum biofilter

Rotating drum biofilters (RDBs) could effectively remove volatile organic compounds (VOCs) from waste gas streams. A mathematical model was developed on the basis of mass transport and mass balance equations in an RDB, the two-film theory, and the Monod kinetics. This model took account of mass transfer and biodegradation of VOC in the gas-water-biofilm three-phase system in the biofilter, and could simulate variations of VOC removal efficiency with a changing specific surface area and porosity of the media due to the increasing of biofilm thickness in the biofilter. Toluene was used as a model VOC. This model was further simplified by introducing a coefficient of the gas velocity and neglecting the water phase due to the complexity of operating conditions. The equations for the biofilm phase, gas phase, and biofilm accumulation in this model were solved using colloction method, analytic method, and the Runge-Kutta method separately. A computer program was written down as MATLAB to solve this model. Results of numerical solutions showed that toluene removal efficiency in the RDB increased and reached the maximum values of 97% on day 4 after the startup, and then decreased the remained at 90% after 5 more days of operation. Toluene concentration was high at the outermost layer where more than 70% toluene was removed, and was low at the innermost layer where less than 10% toluene was removed. The dynamic removal efficiencies from this model correlated reasonably well with experimental results for toluene removal in a multi-layered RDB.

改性磁性纳米颗粒固定内生菌 Bacillus nealsonii 吸附废水中Cd 2+ 的特性研究

从重金属超累积植物龙葵体内提取内生菌Bacillus nealsonii，采用二氧化硅改性纳米Fe3O4颗粒与海藻酸钠将其包埋交联进行固定化，制得一种新型球状生物吸附剂，并应用于废水中Cd2+的吸附处理.同时，通过正交实验研究了该球状生物吸附剂的最佳制备条件和吸附处理条件，并采用扫描电镜等表征手段与构建吸附动力学考察了其吸附特征.结果表明，球状生物吸附剂的最佳制备条件为：改性纳米Fe3O4颗粒质量分数为0.1%，海藻酸钠质量分数为8.0%，菌液接种量为0.4%，交联时间为2 h；其最佳吸附处理条件为pH=6、吸附时间12 h、吸附剂用量（干重）2.5 g·L-1，在Cd2+初始浓度为50 mg·L-1时的吸附率可达96%以上.研究发现，球状生物吸附剂的内外部结构孔隙率较大，有利于促进Cd2+的吸附.该吸附过程遵循准二级反应动力学，以化学吸附为主，符合Freundlich等温吸附模型，最大单分子吸附量可达13.02 mg·g-1.解吸实验结果表明，该吸附剂具有较好的可重复利用性.