School of Environmental Science and Engineering, Key Laboratory of Thin Film and Microfabrication Technology (Ministry of Education), Shanghai Jiao Tong University, Shanghai 200240, China.
Student Innovation Center, Shanghai Jiao Tong University, Shanghai 200240, China.
Water Res. 2024 Feb 1;249:120969. doi: 10.1016/j.watres.2023.120969. Epub 2023 Dec 3.
Excessive phosphate loading leads to eutrophication problems in rivers or lakes and causes serious environmental and economic damages, urging new technologies to reduce effluent phosphate at ultra-low levels. As a promising candidate, adsorption over metal oxides is restricted by the released hydroxide anions (OH) through ligand exchange, which elevates pH and suppresses further adsorption. In this contribution, we found ferrous ions (Fe) significantly enhance phosphate removal over hydrated ferric oxide (HFO) in a wide pH range via a cooperation of adsorption and precipitation, and clarified the synergistic mechanism by a series of characterizations and the modified models of adsorption isotherms and pseudo second-order kinetics. The combination of Feand HFO removed up to 51.7 mg/g of phosphate at pH 4.0, with 43.6 and 8.1 mg/g attributing to adsorption and precipitation, respectively. In comparison to HFO alone, HFO/Fe system achieved 2.2-fold increase in phosphate removal, 1.9-fold increase in phosphate adsorption capacity, and 3.4-fold increase in phosphate removal rate. The enhancement is understood by that hydroxide anions released from ligand exchange over HFO are neutralized by protons produced from the oxidative precipitation of ferrous ions. The HFO/Fe combining system is promising to realize advanced removal of low concentration phosphate containing wastewater, and these findings bring new insights for the development of novel phosphate removal technologies through a rational design of a combination process.
过量的磷酸盐负荷会导致河流或湖泊富营养化问题，并造成严重的环境和经济损失，因此需要开发新技术以超低水平去除废水中的磷酸盐。作为一种很有前途的方法，金属氧化物吸附法受到通过配体交换释放的氢氧根阴离子（OH）的限制，这会升高 pH 值并抑制进一步的吸附。在本研究中，我们发现亚铁离子（Fe）通过吸附和沉淀的协同作用，在很宽的 pH 范围内显著提高了水合氧化铁（HFO）对磷酸盐的去除率，通过一系列的表征和吸附等温线及拟二级动力学模型的修正，阐明了协同作用的机制。在 pH 值为 4.0 时，Fe 和 HFO 的组合可去除高达 51.7mg/g 的磷酸盐，其中 43.6 和 8.1mg/g 分别归因于吸附和沉淀。与单独的 HFO 相比，HFO/Fe 体系的磷酸盐去除率提高了 2.2 倍，磷酸盐吸附容量提高了 1.9 倍，磷酸盐去除率提高了 3.4 倍。这是由于 HFO 上的配体交换释放的氢氧根阴离子被亚铁离子氧化沉淀产生的质子中和。HFO/Fe 组合系统有望实现低浓度含磷废水的深度去除，这些发现为通过组合工艺的合理设计开发新型除磷技术提供了新的见解。
