Calcium carbonate based phosphogypsum: A sustainable solution for thermochemical energy storage

¹ College of Chemical Sciences and Engineering (CCSE), Laboratory of Inorganic Materials for Sustainable Energy Technologies (LIMSET), University Mohammed VI Polytechnic (UM6P), Benguerir, 43150, Morocco
² Laboratory of Physical Chemistry of Applied Materials (LCPMA), Chemistry Department, Hassan II University of Casablanca, Faculty of Science Ben M’sik, Bd Commandant Driss Al Harti, Casablanca 20670

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Published online: 22 May 2026

Abstract

The large number of stockpiles of phosphogypsum (PG), an abundant by-product during the process of producing phosphoric acid, is accompanied by many challenges owing to the toxicity of certain substances contained within PG. In this work, we investigate the transformation of PG into calcium carbonate (CaCO₃) as an appropriate thermochemical energy storage (TCES) agent using the reversible reaction CaCO₃ ↔ CaO+CO₂. For the transformation of PG into CaCO₃₍₁₎ and CaCO₃₍₂₎, PG was reacted with Na₂CO₃ and K₂CO₃ in a proper aqueous medium, respectively. The composition and crystal structures of the resulting products have been confirmed by XRF and XRD to be highly pure (> 97%) with about 2% SiO₂ in situ in CaCO₃ obtained from PG. SEM-EDS analysis demonstrates that rhombohedra with homogeneous element distribution have been obtained successfully. STA tests in the temperature range from 550-800 °C within 10 decarbonation and carbonation cycles demonstrate the stability and reversibility of CO₂ capture and release for both types of CaCO₃ with CaCO3(1) having higher retention (>23% after 10 cycles) compared to CaCO₃₍₂₎ (~19%). The above results confirm that CaCO₃ obtained from PG, especially CaCO₃₍₁₎, is a suitable choice for TCES.