To tackle the issue of phosphorus (P) supply, Sewage Sludge Ash (SSA) is a promising secondary source. The goal of this research is the optimization of the wet P extraction process in the view of providing valuable insights for the process scale-up. While most of the studies relied on the “one-variable-changed-at-a-time” approach, this work applied a statistical optimization model based on the Design of Experiments technique for investigating the influence of most relevant operating conditions of extraction process on Phosphorus Extraction Efficiency (PEE) with two types of SSA characterized by different levels of alkalinity. Experimental results highlighted the importance of ash characteristics, making some SSA not suitable for cost-effective phosphorus recovery due to the high acid dosage required in extraction process. Type of acid and contact time become significant factors only for Ca-rich ashes, especially when using HSO as extracting agent. Optimal operating conditions (C = 1.3 N, L/S = 20, t = 2 h and C = 2.0 N, L/S = 10, t = 2 h for Ash#1 and C = 0.8 N, L/S = 10 for Ash#2) resulting in high PEE (80–94%) were identified for extraction performed with HSO and HCl as a function of ash characteristics.

中文翻译：

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从污水污泥灰烬中提取磷湿法酸的优化：通过多变量统计技术了解详细的工艺过程

为了解决磷 (P) 供应问题，污水污泥灰分 (SSA) 是一种很有前景的二次来源。本研究的目标是优化湿法 P 提取工艺，为工艺放大提供有价值的见解。虽然大多数研究依赖于“一次改变一个变量”的方法，但这项工作应用了基于实验设计技术的统计优化模型来研究提取过程中最相关的操作条件对两种具有不同碱度水平的 SSA 的磷提取效率 (PEE)。实验结果强调了灰分特性的重要性，由于提取过程中需要高酸剂量，使得一些SSA不适合具有成本效益的磷回收。仅对于富含钙的灰分，酸的类型和接触时间才成为重要因素，特别是在使用 H2SO4 作为萃取剂时。最佳操作条件（对于 Ash#1，C = 1.3 N，L/S = 20，t = 2 h，C = 2.0 N，L/S = 10，t = 2 h，C = 0.8 N，L/S = 10对于 Ash#2），使用 HSO 和 HCl 进行提取时会产生高 PEE（80-94%），作为灰分特性的函数。