Physicochemical, crystalline and morphological characteristics of bricks used for ground waters purification in Bangui region (Central African Republic)

The development and improvement of natural water and wastewater purification technologies utilizing low-cost raw materials like bricks are necessary to make possible easy application in poor countries. The present work concerns the detailed studies on a soil which is commonly used to make bricks by craftsmen in Bangui region (Central African Republic). The chemical and mineralogical composition of this soil before and after thermal transformation, and its crystalline, morphological and surface properties were determined by combining several techniques: X-ray Diffraction (XRD), ThermoGravimetric Analyses (TGA), Differential Thermal (DTA) Analyses, TGA/Mass Spectrometry (MS), 27Al and 29Si NMR spectroscopy, and Environmental Scanning Electron Microscopy (ESEM; an apparatus equipped with an Energy Dispersive X-ray Spectrometer, EDS). The basic brick making led to an interesting mesoporous material that was found to be a good adsorbent for Fe(II) removal from contaminated natural waters. Column experiments further revealed significant improvement of the sorption capacity of this brick when its surface was coated with iron oxy-hydroxide. ESEM/EDS micro-analyses revealed that FeOOH was preferentially deposited onto brick clays (mainly disordered metakaolinite), thus showing the key role played by these minerals in the study water treatment when compared to the sorption performances obtained with raw sand and FeOOH-coated sand.