Pratt Chris, Shilton Andy, Pratt Steven, Haverkamp Richard G, Bolan Nanthi S
Centre for Environmental Technology and Engineering, Massey University, Palmerston North, Turitea Campus, New Zealand.
Environ Sci Technol. 2007 May 1;41(9):3296-301. doi: 10.1021/es062496b.
Phosphorus (P) removal mechanisms from waste stabilization pond effluent by a melter slag filter were investigated. The studied filter had treated pond effluent for a decade, but lost its P removal efficiency after 5 years. The P distribution in the slag was examined by scanning electron microscopy (SEM), electron dispersive spectrometry (EDS), X-ray fluorescence (XRF), X-ray diffraction (XRD), and chemical fractionation. The results showed the slag to be covered by a film comprising metal oxides/oxyhydroxides, organic resin, and Fe-phosphate precipitates. The slag porous matrix beneath this film hosted lower P concentrations and consisted of metal oxides/oxyhydroxides and calcmagnesium silicates. The study revealed the following mechanisms for P removal from effluent by the melter slag: (1) P adsorption onto metal oxides/oxyhydroxides which are ubiquitous throughout the porous slag matrix and its surface film; (2) P precipitation, mainly as Fe-phosphates (determined by SEM/EDS) on the surface film, derived from the release of metal ions into the solution phase; and (3) P sequestration by an amorphous organic resin that comprises a substantial proportion of the surface film, which was deduced by SEM/EDS and XRF. Results of chemical extractions performed on the slag demonstrated that 1 M HCl, which has been used to determine Ca-associated P in previous studies, is an unreliable Ca-P marker. By contrast, the citrate-dithionite reagent was shown to be a good indicator of Fe/Al-associated P and revealed that adsorption onto metal oxides/oxyhydroxides, in the porous matrix as well as its surface film, is the most significant P removal mechanism achieved by the slag filter.
研究了熔渣过滤器对稳定塘废水的除磷机制。所研究的过滤器处理塘水已有十年，但在运行五年后失去了除磷效率。通过扫描电子显微镜（SEM）、电子能谱（EDS）、X射线荧光光谱（XRF）、X射线衍射（XRD）和化学分级分析等方法研究了熔渣中的磷分布情况。结果表明，熔渣表面覆盖着一层由金属氧化物/羟基氧化物、有机树脂和铁磷酸盐沉淀组成的薄膜。该薄膜下方的熔渣多孔基质中磷浓度较低，主要由金属氧化物/羟基氧化物和钙镁硅酸盐组成。研究揭示了熔渣过滤器对废水中磷的去除机制如下：（1）磷吸附在多孔熔渣基质及其表面薄膜中普遍存在的金属氧化物/羟基氧化物上；（2）磷沉淀，主要以铁磷酸盐的形式（由扫描电子显微镜/能谱测定）沉淀在表面薄膜上，这是由于金属离子释放到溶液相中导致的；（3）磷被一种无定形有机树脂固定，该树脂在表面薄膜中占很大比例，这是通过扫描电子显微镜/能谱和X射线荧光光谱推断得出的。对熔渣进行化学萃取的结果表明，在以往研究中用于测定与钙结合的磷的1 M盐酸，并不是可靠的钙磷标记物。相比之下，柠檬酸盐-连二亚硫酸盐试剂被证明是与铁/铝结合的磷的良好指示剂，并且表明吸附在多孔基质及其表面薄膜中的金属氧化物/羟基氧化物上是熔渣过滤器实现的最重要的除磷机制。
