Cyanometallate framework templated synthesis of hierarchically porous La(OH)3 for High-Efficient and stable phosphorus removal from tailwater

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2023-06, Vol.465, p.142789, Article 142789
• Main Authors: Jing, Xiaoxu, Zhang, Jing, Li, Yungui, Li, Qingqing, Shen, Yi, Liu, Jining, Zhang, Suorong, Fang, Qile
• Format: Article
• Language: English
• Subjects: Aquaculture tailwater; Hierarchically porous structure; Lanthanum hydroxide; Phosphorus removal
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2023.142789

[Display omitted] •A hierarchically porous La(OH)3 is derived from LaFe cyanometalate precursor.•The porous La(OH)3 microsphere shows excellent structure stability.•The high selectivity makes it a favorable adsorbent in aquaculture tailwater treatment.•It can rapidly reduce the dissolved inorganic phosphorus below 0.05 mg P/L.•It shows excellent environmental adaptability in a wide range of salinities and temperatures. Lanthanum (La)-based hydroxides have been recognized as promising candidates for dephosphorization due to their high affinity and selectivity for phosphate adsorption. However, the development of porous La(OH)3 materials with enriching active sites and high structural stability remains a challenge in tailwater treatment. Here we developed a novel self-templating method based on an ion-exchange mechanism to construct hierarchically porous La(OH)3, where the OH− of an alkali conversion reagent replaces the [Fe(CN)6]4− cluster within the LaFe cyanometalate (CM) precursor, simultaneously completing the hydroxide conversion and pore-creating processes. The obtained hierarchically porous La(OH)3 shows excellent structural stability with no ion leaching and can maintain its primary microsphere structure and secondary nanoneedle morphology after multiple cycles of application. Due to the abundant micropores/mesopores, there are fully exposed active sites inside and outside the porous La(OH)3 microsphere, giving it an excellent phosphate adsorption capacity (maximum capacity of 163.6 mg P/g). Its high selectivity and environmental adaptability make it a favorable adsorbent for aquaculture tailwater treatment that can rapidly reduce the dissolved inorganic phosphorus level to below 0.05 mg P/L to meet the mariculture tailwater discharge standard in a wide range of salinities and temperatures. The information gleaned in this study provides valuable guidance for the materials design of porous La-based hydroxides for phosphorus removal.