Maggetti C, Pinelli D, Di Federico V, Sisti L, Tabanelli T, Cavani F, Frascari D
Department of Civil, Chemical, Environmental and Materials Engineering (DICAM), Alma Mater Studiorum -, University of Bologna, via Terracini 28, 40131 Bologna, Italy.
Dipartimento di Chimica Industriale "Toso Montanari", Alma Mater Studiorum -, University of Bologna, Viale Risorgimento 4, 40136, Bologna, Italy.
Sci Total Environ. 2024 Nov 15;951:175509. doi: 10.1016/j.scitotenv.2024.175509. Epub 2024 Aug 13.
In the current international context characterized by the tendency to stricter limits for P concentration in treated wastewater and a strong drive towards phosphate recovery, it is crucial to develop cost-effective technologies to remove and recover phosphate from municipal wastewater (MWW). In this study, an initial screening of the phosphate adsorption performances of 9 sorbents including several hydrotalcites led to the selection of calcined pyroaurite - an innovative material composed of mixed Mg/Fe oxides - as the best-performing one. The assessment of calcined pyroaurite by means of isotherms and continuous-flow adsorption/desorption tests conducted with actual MWW resulted in a high P sorption capacity (12 mg g at the typical phosphate concentration in MWW), the capacity to treat 730 BVs at the 1 mg L breakpoint imposed by the current EU legislation, and a 93 % phosphate recovery. Calcined pyroaurite resulted in satisfactory performances also in a test conducted with a saline MWW deriving from a hotspot of seawater intrusion, a rapidly increasing phenomenon as a result of climate change. Five consecutive adsorption/desorption cycles conducted in a 20-cm column at a 5-min empty bed contact time resulted stable in terms of P adsorption/recovery performances, specific surface area and chemical structure of calcined pyroaurite. In the perspective to apply phosphate recovery with calcined pyroaurite at full scale, the process scale-up to a 60-cm packed bed - close to the column heights of industrial applications - resulted in stable performances. Calcium phosphate, widely used to produce phosphate-based fertilizers, can be obtained from the desorbed product by precipitation with Ca(OH). These results point to calcined pyroaurite as a very promising material for phosphate removal and recovery from MWW and from other P-rich effluents in a circular economy perspective.
在当前国际背景下，对处理后废水中磷浓度的限制趋于严格，且对磷回收的推动力度很大，因此开发具有成本效益的技术以从城市污水（MWW）中去除和回收磷至关重要。在本研究中，对包括几种水滑石在内的9种吸附剂的磷吸附性能进行了初步筛选，结果选择了煅烧镁铁水滑石——一种由混合镁/铁氧化物组成的创新材料——作为性能最佳的吸附剂。通过等温线以及用实际城市污水进行的连续流吸附/解吸试验对煅烧镁铁水滑石进行评估，结果表明其具有高磷吸附容量（在城市污水中典型磷浓度下为12 mg/g），在当前欧盟法规规定的1 mg/L突破点下能够处理730倍床体积的污水，且磷回收率达93%。在一项针对因海水入侵热点地区产生的含盐城市污水进行的试验中，煅烧镁铁水滑石也表现出令人满意的性能，海水入侵是气候变化导致的迅速增加的现象。在20厘米长的柱子中以5分钟空床接触时间进行的五个连续吸附/解吸循环，在磷吸附/回收性能、煅烧镁铁水滑石的比表面积和化学结构方面表现稳定。从大规模应用煅烧镁铁水滑石进行磷回收的角度来看，将工艺放大至60厘米填充床——接近工业应用中的柱高——性能稳定。广泛用于生产磷肥的磷酸钙可通过用Ca(OH)₂沉淀从解吸产物中获得。从循环经济的角度来看，这些结果表明煅烧镁铁水滑石是一种从城市污水和其他富含磷的废水中去除和回收磷的非常有前景的材料。
