Removal of high concentration chlorides and organic pollutants from incineration fly ash and sewage sludge hydrothermal liquid by Friedel's salt preparation

Hao Yu; Zhiwei Li; Di Yu; Jingxin Huang; Xiaoyan Zou; Yin Wang

doi:10.1016/j.jenvman.2025.124383

Removal of high concentration chlorides and organic pollutants from incineration fly ash and sewage sludge hydrothermal liquid by Friedel's salt preparation

J Environ Manage. 2025 Feb 2:375:124383. doi: 10.1016/j.jenvman.2025.124383. Online ahead of print.

Authors

Hao Yu¹, Zhiwei Li², Di Yu³, Jingxin Huang¹, Xiaoyan Zou³, Yin Wang⁴

Affiliations

¹ Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China; College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
² Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China; University of Chinese Academy of Sciences, Beijing, 100049, China. Electronic address: zwli@iue.ac.cn.
³ Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China.
⁴ Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China; Ningbo (Beilun) Zhongke Haixi Industrial Technology Innovation Center, Ningbo, 315000, China. Electronic address: yinwang@iue.ac.cn.

PMID: 39899921
DOI: 10.1016/j.jenvman.2025.124383

Abstract

Hydrothermal liquid, produced in the process of coordinated hydrothermal harmless disposal of incineration fly ash (IFA) and sewage sludge (SS), contains a large number of organic pollutants and chloride. There is no report on the treatment of wastewater produced by hydrothermal treatment. To address the aforementioned issue, this study employs Friedel's salt precipitation for the dechlorination of the hydrothermal liquid. Experimental results show that the application of a reagent ratio of n(Al):n(Ca):n(Cl) = 4:8:1 effectively removed 76.77% of Cl^- and 99.76% of SO₄^2- from the hydrothermal liquid at an optimized temperature of 25 °C. Additionally, not only a 36.85% reduction of total organic carbon (TOC) was achieved through flocculation with sodium aluminate (NaAlO₂), but also merely 1% of Al³⁺ from the original dosage remained in the filtrate. Moreover, combined with the analysis of the phase structure of the precipitate, Friedel's salt precipitation primarily removes Cl^- via interlayer ion exchange and charge balance adsorption, providing insights into the operational mechanisms and the influence of interference factors. This work provides technical support for the application of synergistic hydrothermal treatment technology of IFA and SS, also has reference value for the treatment of other high chlorine-containing organic wastewater.

Keywords: Coagulation; Dechlorination; Friedel's salt; Hydrothermal liquid; Incineration fly ash; Sewage sludge.