Recovery of phosphate from aqueous solutions via vivianite crystallization: Thermodynamics and influence of pH
Recovery of phosphate from aqueous solutions via vivianite crystallization: Thermodynamics and influence of pH
复制标题
通过绿铁矿结晶从水溶液中回收磷酸盐：热力学和 pH 值的影响
DOI：
10.1016/j.cej.2018.05.064
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发表时间：
2018-10-01
影响因子：
15.1
通讯作者：
Qu, Dan
中科院分区：
文献类型：
--
作者：
Liu, Jiaqi;Cheng, Xiang;Qu, Dan
Vivianite 介导的磷酸盐固定化已在自然环境中得到广泛报道，并且可能是从污水中回收磷的一种有前途的措施。本文从热力学角度研究了污水处理厂（STP）厌氧污泥消化池中绿铁矿结晶的相容性，其中污水中的磷被浓缩，并研究了pH作为主要影响因素的影响。不同条件下的斑铁矿结晶也通过批量测定和连续反应器进行。通过 MINTEQ 3.0 软件包评估化学平衡和规格，并通过 X 射线衍射、显微镜和激光衍射粒度分析仪分析反应产物。结果表明，在25~55℃温度范围内，蓝铁矿的pKsp为39.8~40.7，温度影响不显着。菱铁矿的介稳区为SI（过饱和指数）0-11，但当SI高于4时，结晶作用大大增强。在pH 7时观察到了菱铁矿的有效结晶； pH 6 时的 SI 水平不足以引发晶体成核，而 pH 8 时，简单的沉淀而非结晶成为主导。添加石英颗粒作为晶种通过加速反应和降低过饱和需求来促进紫铁矿结晶。总之，本研究表明，磷矿回收的磷酸盐回收途径在热力学上与富磷厌氧消化系统相容。由于磷酸盐和 Fe(II) 离子的形式都依赖于 pH 值，因此蓝铁矿结晶会受到系统 pH 值的决定性影响。显然，其他物理化学和微生物条件（例如悬浮固体）也会影响复杂污泥混合物中蓝铁矿的形成，并需要对工艺优化进行更多研究。
Vivianite mediating phosphate immobilization has been widely reported in natural environments and could be a promising measure for phosphorus recovery from sewage. This paper investigated the compatibility of vivianite crystallization in anaerobic sludge digesters at sewage treatment plants (STPs), where P in the sewage is concentrated, from a thermodynamic perspective and the effect of pH as a major influencing factor was studied. Vivianite crystallization under different conditions was performed by batch assays and in a continuous reactor as well. Chemical equilibriums and specification were evaluated by a MINTEQ 3.0 package, and the reaction products were analyzed by X-ray diffraction, microscopy and a laser diffraction particle size analyzer. The results show that the pKsp of vivianite was 39.8-40.7 at temperatures from 25 to 55 degrees C, and the temperature effect was insignificant. The metastable zone for vivianite was SI (supersaturated index) 0-11, but crystallization was greatly enhanced when SI was higher than 4. Effective crystallization of vivianite was observed at pH 7; the SI level at pH 6 was insufficient to trigger crystal nucleation and at pH 8 simple precipitation became dominant rather than crystallization. Adding quartz grains as seeds promoted vivianite crystallization by accelerating the reactions and lowering the supersaturation demand. In summary, this study demonstrated that vivianite pathway of phosphate recovery was thermodynamically compatible with P-rich anaerobic digestion systems. Because the forms of both phosphate and Fe(II) ions are pH-dependent, vivianite crystallization can be determinatively affected by the pH level of the system. Apparently, other physico-chemical and microbiological conditions, e.g., suspended solids, would also influence vivianite formation in the complex sludge mixture and warrants more research for process optimization.