类水滑石对污泥焚烧飞灰浸出液中磷的纯化

采用Mg-Fe型类水滑石（LDH）吸附剂提纯污泥焚烧飞灰（ISSA）浸出液中的磷，探究了吸附剂煅烧对磷吸附效果的影响及磷吸附和脱附机理.研究发现，在高浓度磷溶液（>1000mg/L）中，未煅烧的类水滑石（LDHu）磷吸附容量高于煅烧后的类水滑石（LDHc）.LDHu具有典型的层状结构，磷的吸附与脱附主要通过磷和金属离子沉淀-溶解、静电吸附-排斥、配位作用和离子交换实现.而LDHc层状结构消失，形成双金属氧化物，不存在明显的阴离子交换作用.经LDHu或LDHc吸附和NaOH溶液脱附后，ISSA浸出液均具有良好的磷纯化效果，磷相对纯度从36%分别上升至77%和69%，磷回收率分别为84%和57%.纯化后的溶液适合制备高值含磷产物.

Purification of phosphorus in the incinerated sewage sludge ashleachate by layered double hydroxides

Phosphorus is an essential and limited resource. Incinerated sewage sludge ash (ISSA), which is phosphorus-enriched, shows a valuable potential for phosphorus recovery. Wet chemical method can effectively leach phosphorus from ISSA, but the major metals and heavy metals are leached at the same time, which influence the subsequent phosphorus recovery. In this study, Mg-Fe layered double hydroxides (LDH) is used to selectively adsorb and desorb phosphate. The phosphorus adsorption effects of uncalcined (LDHu) and calcined LDH (LDHc) as well as the mechanism of phosphorus adsorption and desorption were investigated. At high phosphorus concentrations (>1000mg/L), the phosphorus adsorption capacity of the LDHu was higher than that of the LDHc. The LDHu has a typical double layered structure. Phosphorus adsorption and desorption was achieved mainly by the phosphate precipitation-dissolution, electrostatic adsorption-repulsion, ligand interaction and ion exchange. After calcination, LDHc lost the layered structure, and was transformed into double metal oxide. There was no significant anion exchange process for the calcined LDH during adsorption and desorption. After LDHu or LDHc adsorption and alkaline desorption, the ISSA leachate could achieve good phosphorus purification effects, with the relative phosphorus purity increased from 36% to 77% and 69%, as well as a phosphorus recovery of 84% and 57%, respectively. The purified ISSA leachate is suitable for the subsequent valorization of high-value phosphorus-containing product.