电化学沉淀/复合黏土吸附法回收黄水中的营养盐

Recovery of Nutrients from Yellow Water by Electrochemical Deposition/Composite Clay Adsorption Method

为了回收黄水中的氮、磷营养盐,构建电化学鸟粪石沉淀反应装置,试验结果表明,当电流密度为2.5 mA/cm^2时,磷回收速率及总回收率都为最高,反应4 h时磷回收率达到97.2%,沉淀产物中鸟粪石晶体的纯度为95.7%;氨氮去除率随电流密度的升高而增加,但电化学沉淀法对氨氮的最大去除率仅为21.6%。利用改性凹凸棒-膨润土复合黏土对电化学沉淀后黄水中的氨氮进行吸附,发现其对氨氮的吸附过程更符合拟二级动力学模型,对氨氮的平衡吸附量可达到15.30 mg/g。扫描电子能谱分散显微镜(SEM-EDS)分析表明,从实际黄水中回收的产物多为棱柱状晶体,晶体表面杂质较多,且含有一定量的钾型鸟粪石。

An electrochemical struvite reaction device was constructed to recover nitrogen and phosphorus nutrients from the yellow water. When the current density was 2. 5 mA/cm2,the recovery efficiency of phosphorus was the highest,and the recovery rate of phosphorus was 97. 2% and the purity of struvite was 95. 7% after 4 h reaction. The removal rate of NH4+ -N increased with the increase of current density,while the maximum removal rate of NH4+ -N by the electrochemical deposition was only 21. 6%. The modified attapulgite-bentonite composite clay was used to adsorb NH4+ -N in yellow water after the precipitation of struvite. The adsorption process of NH4+ -N was more consistent with the pseudo-second-order kinetic model,and the equilibrium adsorption capacity of NH4+ -N was up to 15. 30 mg/g. SEM-EDS analysis showed that recovered products from real yellow water were mostly prismatic crystals,and the crystal surface had many impurities and contained certain potassium struvite.