Surface characteristics of the iron-oxyhydroxide layer formed during brick coatings by ESEM/EDS, 23Na and 1H MAS NMR, and ToF-SIMS

• HCl-activated brick was coated at different Fe(III)-precipitation pH.
• Surface properties were determined by ESEM, NMR and ToF-SIMS.
• Al- and Si-bearing ferrihydrite and different Na environments were detected.
• The pH used for modified-brick synthesis influenced metal uptake from water.

Brick made locally by craftsmen in Bangui (Central African Republic) was modified first by HCl activation and second by iron-oxyhydroxide impregnation through the precipitation of ferric ions by NaOH at various fixed pH values (ranging from 3 to 13). The elemental analyses of synthesized compounds were performed using ICP-AES, and their surface chemistry/properties were investigated by environmental scanning electron microscopy (ESEM/EDS), 1H and 23Na MAS NMR spectroscopy, and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The evidence of different 23Na chemical environments and the coexistence of Si and Al bound to ferrihydrite were made. The surface properties of this material which was found to be dependent upon synthesis pH, contributed to enhance metal uptake from water.

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