改性磁性纳米颗粒固定内生菌Bacillus nealsonii吸附废水中Cd2+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Fe_3O_4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Cd~(2+)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p H=6、吸附时间12 h、吸附剂用量(干重)2.5 g·L-1,在Cd~(2+)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Cd~(2+)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.

Adsorption of Cd2+ in wastewater through modified magnetic nanoparticles immobilizing endogenous bacterium Bacillus nealsonii

The endogenous bacterium Bacillus nealsonii was extracted from hyperaccumulation plant Solanum nigrum. Then a spherical biological adsorbent was prepared using silica modified magnetic Fe₃O₄ nanoparticles and sodium alginate to immobilize the bacterium. Finally the adsorbent was applied for the Cd²⁺ removal from synthetically wastewater. The optimal preparation and adsorption conditions of the adsorbent were determined by designed orthogonal tests, and its adsorption properties were characterized by using SEM and adsorption kinetics. Results show that the best preparation conditions of the adsorbent were under the dosage of magnetic Fe₃O₄ nanoparticles of 0.1%, the dosage of sodium alginate of 8.0%, the volume fraction of microbial inoculation of 0.4%, and crosslinking time of 2 h. The optimal adsorption conditions were pH 6, adsorption time of 12 h, the adsorbent dosage of 2.5 g·L^-1. Under the optimal conditions at the Cd²⁺ concentration of 50 mg·L^-1, the adsorption efficiency was over 96%. The adsorbent has large porosity at both the interior and surface, which is benefit for enhancing the Cd²⁺ adsorption. The adsorption process follows the quasi secondary-order kinetic model (Freundlich isothermal adsorption model), and the highest adsorption capacity could reach 13.02 mg·g^-1. Results also show that this new adsorbent could be well reused.