Surface chemistry and structure evaluation of Mg/Al and Mg/Fe LDH derived from magnesite and dolomite in comparison to LDH obtained from chemicals

Multiple attempts have been made to lower the cost of the adsorbents for the wastewater treatment. This work investigated the possibility of obtaining Mg/Al and Mg/Fe LDH without excessive use of chemical reagents, by replacing them with cheaper substrates. Magnesite and dolomite were used as Mg-sources in a facile co -precipitation synthesis at room temperature. Several variants of LDHs were studied regarding their chemical composition, M-II/M-III molar ratio and the synthesis time. Their comprehensive characterization was provided and compared to the reference materials obtained from chemical reagents. Depending on the molar ratio the reference samples exhibited a clear shift of the XRD basal reflections, and different species of interlayer carbonates were identified by spectroscopic methods. The LDHs derived from minerals had similar structural features as compared to the reference samples. However, the synthesis of mineral-based LDHs resulted in the formation of additional phases. The formation of LDH from minerals with a molar ratio higher than 2:1 was impossible in the applied conditions. The 2 h ageing time was enough to enable the LDH formation. The transformation procedure of magnesite and dolomite to LDH via simplified synthesis procedure may significantly reduce the final cost of the adsorbents by excluding expensive chemical reagents.

Automated summary

The study explored the possibility of obtaining Mg/Al and Mg/Fe LDHs without excessive use of chemical reagents by using cheaper substrates through a simplified co-precipitation synthesis at room temperature. The LDHs derived from minerals showed similar structural features as compared to the reference samples, but resulted in the formation of additional phases. The transformation procedure via simplified synthesis may significantly reduce the final cost of the adsorbents by excluding expensive chemical reagents.