电活性镍钴双金属氧化物高选择性去除/回收水中磷酸盐离子

Potential Induced Reversible Removal/Recovery of Phosphate Anions with High Selectivity Using an Electroactive NiCo-layered Double Oxide Film

磷是植物体生长的重要营养素,也是引发水体富营养化的重要因素,因此废水中磷酸盐的去除与回收均至关重要。本研究采用单极脉冲电沉积法在炭布上制备镍钴双氢氧化物,并于管式炉中原位焙烧制得镍钴双金属氧化物(NiCo-Layered Double Oxide,NiCo-LDO),将其用于电控离子交换(Electrochemically Switched Ion Exchange,ESIX)过程实现PO_(4)^(3-)的去除与回收。实验对比了ESIX与离子交换(Ion Exchange,IX)过程中NiCo-LDO对PO_(4)^(3-)的去除性能,并考察了其选择性及循环稳定性。结果表明,在(10.00±0.05)mg/L的PO_(4)^(3-)溶液中,ESIX过程中膜对PO_(4)^(3-)的离子交换量约为IX的2倍;NiCo-LDO对PO_(4)^(3-)具有高选择性,且经过5次循环后,离子交换量仍可达到初始值的92%以上;结合XPS分析,发现NiCo-LDO对PO_(4)^(3-)的ESIX过程包括一个不可逆的"记忆效应"结构恢复过程及两个可逆的层板金属离子氧化/还原和PO_(4)^(3-)与O-H基团的配体交换过程。

Phosphorus is an essential nutrient for organisms growth and a major cause of eutrophication in water bodies.Thus,it is crucial for both of the removal and recovery of phosphate from wastewater.In this work,the NiCo-layered double oxide(NiCo-LDO)was successfully fabricated on carbon cloth conductive substrate via the in-situ calcination of the NiCo-layered double hydroxide(NiCo-LDH)and served as the electrochemically switched ion exchange(ESIX)film electrode for the removal and recovery of PO_(4)^(3-).The performance of NiCo-LDO for PO_(4)^(3-)removal by ESIX and ion exchange(IX)was compared,while the selectivity and stability of NiCo-LDO for PO_(4)^(3-)removal were also investigated.The results revealed that,in(10.00±0.05)mg/L PO_(4)^(3-)solution,the ion exchange quantity of the NiCo-LDO for PO_(4)^(3-)removal by ESIX process was about twice over that by IX.Moreover,compared with Cl-,NO_(3)-,SO_(4)2-and I-,the NiCo-LDO exhibited much higher selectivity towards PO_(4)^(3-).In addition,the ion exchange quantity still retained 92%of its initial value after 5 uptake and release cycles.Coupled with XPS analysis,it was found that ESIX process of NiCo-LDO film electrode for PO_(4)^(3-)removal and recovery mainly consisted of 3 steps,which were an irreversible"memory effect"structure recovery process,the redox reaction of metal ion in lamellar and the ligand exchange between PO_(4)^(3-)and O-H groups.