Regeneration method and mechanism of phosphorus adsorbent Mg/Al-LDO
WANG Wei-dong, HAO Rui-xia, ZHU Xiao-xia, WAN Jing-jing, ZHONG Li-yan
Key Laboratory of Beijing for Water Quality Science and Water Environment Recovery Engineering, Beijing University of Technology, Beijing 100124, China
In order to improve the reuse of phosphorus adsorbent Mg/Al-LDO, the regeneration effects of roasting one-step regeneration and desorption-roasting two-step regeneration were compared.Based on XRD and FTIR spectrum analysis, the changes of crystal structure and interlayer anionof the adsorbentwere analyzed, and the regeneration mechanism of Mg/Al-LDO and reasons for the declining regenerationratewere then discussed. The results indicated thatdesorption-roasting two-step regeneration was more suitable for the regeneration of Mg/Al-LDO, with the following optimum regeneration condition:desorption solution of NaOH-Na2CO3 mixture, roasting temperature of 550℃ and duration of 6h. It was found that the primary regeneration rate reached 95%, but the regeneration rate dropped to 67% after five regenerations. Thus, a problem of decreased regeneration rate existed. Based on the adsorption mechanism of Mg/Al-LDO and the analysis of XRD and FTIR spectrum, the reasons for the declining regeneration rate include two aspects:(1) incomplete desorption of phosphate due to the chemical adsorptionof Mg/Al-LDO led toun-removed residual phosphate in the crystal under high temperature calcination that still occupy the adsorbent adsorption site; (2) the conversion of Mg/Al-LDO into spinel(MgAl2O4) after several high-temperature calcinationsled to the loss of adsorption capacity.
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