Rabin Desalination Laboratory, Grand Water Research Institute, Department of Chemical Engineering, Technion, Haifa, Israel.
J Colloid Interface Sci. 2011 Nov 15;363(2):608-14. doi: 10.1016/j.jcis.2011.07.062. Epub 2011 Jul 27.
Phosphate adsorption mechanism by a homogenous porous layer of nano-sized magnetite particles immobilized onto granular activated carbon (nFe-GAC) was studied for both interface and bulk structures. X-ray Photoelectron Spectroscopy (XPS) analysis revealed phosphate bonding to the nFe-GAC predominantly through bidentate surface complexes. It was established that phosphate was adsorbed to the magnetite surface mainly via ligand exchange mechanism. Initially, phosphate was adsorbed by the active sites on the magnetite surface, after which it diffused into the interior of the nano-magnetite layer, as indicated by intraparticle diffusion model. This diffusion process continues regardless of interface interactions, revealing some of the outer magnetite binding sites for further phosphate uptake. Desorption, using NaOH solution, was found to be predominantly a surface reaction, at which hydroxyl ions replace the adsorbed phosphate ions only at the surface outer biding sites. Five successive fix-bed adsorption/regeneration cycles were successfully applied, without significant reduction in the nFe-GAC adsorption capacity and at high regeneration efficiency.
采用固定在颗粒状活性炭（nFe-GAC）上的纳米尺寸磁铁矿均匀多孔层研究了磷酸盐的吸附机理，包括界面和体相结构。X 射线光电子能谱（XPS）分析表明，磷酸盐主要通过双齿表面络合物与 nFe-GAC 键合。确定磷酸盐主要通过配体交换机制吸附到磁铁矿表面。最初，磷酸盐通过磁铁矿表面的活性位点被吸附，之后它通过内扩散模型扩散到纳米磁铁矿层的内部。该扩散过程持续进行，与界面相互作用无关，这表明外层磁铁矿结合位点可以进一步吸附磷酸盐。使用 NaOH 溶液进行解吸被发现主要是一个表面反应，其中只有在表面外层结合位上，羟基离子才会取代吸附的磷酸盐离子。成功应用了五个连续的固定床吸附/再生循环，nFe-GAC 的吸附容量没有明显降低，且再生效率很高。
