A proof-of-concept study on green mining of seawater calcium via biochar interfaces for fluoride removal and carbon dioxide capture
Journal
Journal of Environmental Chemical Engineering
Journal Volume
14
Journal Issue
2
Start Page
121228
ISSN
22132929
Date Issued
2026-04
Author(s)
Abstract
Seawater represents an abundant but underutilized source of calcium; however, conventional Ca recovery relies on energy-intensive separation and purification processes that limit its sustainability. In this proof-of-concept study, we demonstrate that introducing additional biochar interfaces can promote the preferential deposition of seawater-derived Ca under solar-driven evaporation conditions, enabling its subsequent utilization for fluoride removal and carbon dioxide capture. Correlation analyses reveal that Ca deposition is primarily governed by accessible surface area and surface hydrophobicity, which enhance localized supersaturation and heterogeneous nucleation at the biochar–brine interface. In contrast, Mg deposition remains consistently suppressed due to its higher hydration energy. As a result, Ca/Mg molar selectivity spans from 2.52 to 56.66, and seawater-derived Ca loadings reach 0.27–3.44 mmol/g (1.1–13.7 wt%). The resulting Ca-loaded biochars exhibit effective fluoride removal through CaF2 precipitation at surface-accessible Ca domains, while CO2 capture proceeds through carbonation of a limited fraction of reactive Ca-bearing species. Importantly, Ca utilization in both cases is controlled by interfacial accessibility rather than total Ca inventory. This study further proposes a boundary-condition framework in which Ca/Mg-loaded biochars are directly valorized as green supplemental fuels and mineral feedstocks. Under an optimistic dual-substitution scenario, Ca/Mg-loaded biochar enables an estimated ∼14 % reduction in CO2 emissions for the cement production. Overall, selective mining of seawater calcium provides a feasible pathway to repurpose traditional solar salterns into suppliers of green raw materials, supporting resource circularity and advancing the United Nations Sustainable Development Goal 11: Sustainable Cities and Communities.
Subjects
Biochar
CO2 capture
Fluoride removal
Seawater mineral mining
Sustainable development
Publisher
Elsevier Ltd
Description
Article number 121228
Type
journal article