Low-cost eggshell-fly ash adsorbent for phosphate recovery: A potential slow-release phosphate fertilizer

Chengyou Sun; Chao Huang; Ping Wang; Jinglin Yin; Haoran Tian; Zili Liu; Haiyin Xu; Jian Zhu; Xinjiang Hu; Zhiming Liu

doi:10.1016/j.watres.2024.121483

Low-cost eggshell-fly ash adsorbent for phosphate recovery: A potential slow-release phosphate fertilizer

Water Res. 2024 May 15:255:121483. doi: 10.1016/j.watres.2024.121483. Epub 2024 Mar 18.

Authors

Chengyou Sun¹, Chao Huang², Ping Wang³, Jinglin Yin⁴, Haoran Tian¹, Zili Liu¹, Haiyin Xu¹, Jian Zhu¹, Xinjiang Hu¹, Zhiming Liu⁵

Affiliations

¹ College of Environmental Science and Engineering, Central South University of Forestry and Technology, Changsha 410004, China.
² College of Environmental Science and Engineering, Central South University of Forestry and Technology, Changsha 410004, China. Electronic address: huangchao@csuft.edu.cn.
³ College of Environmental Science and Engineering, Central South University of Forestry and Technology, Changsha 410004, China. Electronic address: pingwang@csuft.edu.cn.
⁴ College of Science, Central South University of Forestry and Technology, Changsha 410004, China.
⁵ Department of Biology, Eastern New Mexico University, Portales, NM 88130, USA. Electronic address: zhiming.liu@enmu.edu.

PMID: 38508039
DOI: 10.1016/j.watres.2024.121483

Abstract

Fly ash (FA) and eggshells (ES) are common solid wastes with significant potential for the recovery of phosphorus from water. This study focuses on synthesizing a low-cost and environmental-friendly phosphate adsorbent called eggshell-fly ash geopolymer composite (EFG) using eggshells instead of chemicals. The CaO obtained from the high-temperature pyrolysis of eggshells provides active sites for phosphate adsorption, and CO₂ serves as a pore-forming agent. The phosphate adsorption performance of EFG varied with the eggshell-fly ash ratios and achieved a maximum of 49.92 mg P/g at an eggshell-fly ash ratio of 40 %. The adsorption process was well described by the pseudo-second-order model and the Langmuir model. EFG also exhibited a good regeneration performance through six-cycle experiments and achieved the highest phosphate desorption at pH 4.0. The results of the column experiment showed that EFG can be used as a filter media for phosphorus removal in a real-scale application with low cost. Soil burial test indicated saturated EFG has a good phosphate slow-release performance (maintained for up to 60 days). Overall, EFG has demonstrated to be a promising adsorbent for phosphorus recovery.

Keywords: Adsorbent; Eggshell; Fly ash; Phosphate recovery; Pore-forming agent.