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为提高磷吸附剂Mg/Al-LDO的重复利用性,比较了焙烧一步再生法和解吸-焙烧两步再生法的再生效果;基于XRD、FTIR谱图分析再生过程中吸附剂的晶体结构及层间阴离子的变化,探讨了Mg/Al-LDO的再生机制及再生率下降的原因.结果表明,解吸-焙烧两步再生法更适合作为Mg/Al-LDO的再生方法,最佳再生条件为:解吸液为Na OH-Na_2CO_3混合液,焙烧条件为温度550℃、时间6h;首次再生率可达到95%,经过5次再生后,再生率降为67%,存在再生率下降问题.根据Mg/Al-LDO吸附磷酸根的吸附机制和XRD、FTIR谱图分析,再生率下降的原因包括两方面:一是由于吸附剂的化学吸附作用导致磷酸根解吸不彻底,高温焙烧后晶体中残存的磷酸根仍占据着吸附剂的吸附位点;二是经多次高温焙烧后部分Mg/Al-LDO转化为尖晶石MgAl_2O_4,失去吸附能力.
In order to improve the reusability of phosphorus adsorbent Mg / Al-LDO, the regenerative effects of one-step calcination and desorption-calcination two-step regeneration were compared. The crystal structure and layer of adsorbent during regeneration were analyzed based on XRD and FTIR spectra The results showed that the desorption-roasting two-step regeneration method is more suitable for the regeneration of Mg / Al-LDO. The optimum regeneration conditions are as follows: The desorption solution was Na OH-Na 2 CO 3 mixture, the calcination temperature was 550 ℃ and time was 6h, the first regeneration rate could reach 95%, and after 5 times of regeneration, the regeneration rate decreased to 67% Al-LDO adsorption of phosphate adsorption mechanism and XRD, FTIR spectroscopy analysis, the regeneration rate decreased for two reasons: First, due to chemical adsorption of adsorbents led to the desorption of phosphate is not complete, high temperature calcined crystal remaining phosphoric acid The root still occupies the adsorption site of the adsorbent; the second is the conversion of some Mg / Al-LDO to spinel MgAl 2 O 4 after repeated calcination at high temperature, losing the adsorption capacity.