Abstract:

In order to efficiently utilize the spent bleaching earth produced by the edible oil industry, a novel adsorbent was prepared by transforming spent bleaching earth into BE500 and BE700 to remove the copper ions (Cu²⁺) and tetracycline (TC) that commonly existed in livestock and poultry wastewater. The effects of adsorbent dosage, pH, ionic strength, and competition adsorption under the binary system was investigated. The results showed that BE700 was more suitable for Cu²⁺ adsorption, while BE500 exhibited higher removal efficiency for TC. Compared with Cu²⁺, the adsorption capacity of TC was less sensitive to the changes in the pH of the reacted solution. The results of kinetic models pointed out that the adsorption of BE500 and BE700 for Cu²⁺ and TC could be mainly attributed to the chemical reaction, and the liquid-film diffusion controlled the whole adsorption rate. The adsorption isotherms and thermodynamics model indicated that Cu²⁺ and TC were multi-layered immobilized on the surface of BE500 and BE700, and the adsorption was spontaneous with an endothermic process. In addition, the ion interference experiment showed that the co-existed of Cl^- and Na⁺ posed an insignificant role in influencing the adsorption performance for Cu²⁺ and TC. The Cu²⁺ and TC adsorption capacity of BE500 and BE700 was significantly enhanced under the binary system compared to that in the single system, which meant that the Cu²⁺ and TC presented a synergistic effect due to the reaction between Cu²⁺ and TC. The characterizations suggested that the pore-filling, ion exchange, complexation, hydrogen bond and π-π electron donor-acceptor interaction might participated in the removal mechanism of Cu²⁺ and TC.

Key words: spent bleaching earth, adsorbent, tetracycline, copper, synergistic removal

摘要：

为有效利用食用油行业产生的白土废弃物，以及解决畜禽养殖废水中的重金属及抗生素残留问题。本研究通过热解的方式将废白土转化为新型吸附剂BE500和BE700，用于水中铜离子（Cu²⁺）和四环素（TC）的去除，并考察了吸附剂投加量、反应pH、离子干扰和竞争条件下的吸附效果。结果显示，BE700更适合于Cu²⁺的吸附，而BE500对TC的去除效率更高。相比于Cu²⁺，TC吸附量对溶液pH变化的敏感度更低。动力学模型拟合结果显示，BE500和BE700对Cu²⁺和TC的吸附主要是发生了化学反应，且吸附速率主要受到液膜扩散的控制。等温吸附和热力学模型拟合结果则表明BE500和BE700与Cu²⁺和TC之间主要发生了多层吸附，且吸附是自发的吸热过程。此外，离子干扰实验显示，Cl^-和Na⁺对吸附效果的影响较小。而竞争吸附实验显示了在二元体系中BE500和BE700对Cu²⁺和TC的吸附量较一元体系显著增加，即Cu²⁺和TC之间的反应促进了Cu²⁺和TC的协同去除。表征结果显示孔隙填充、离子交换、络合反应、氢键和π-π相互作用均参与了对Cu²⁺和TC的去除机制。

关键词: 废白土, 吸附剂, 四环素, 铜, 协同去除