Physico-chemical characterisations of alum sludges from the drinking water production plant of sinématiali, northen Côte d’Ivoire

In the northern region of Côte d’Ivoire, alum sludges from the Sinématiali drinking water production plantare directlyrejected into the natural environment without any specific treatment.This constitutes a source of pollution and potential health hazards. The aim of this study is to evaluate the potentialvalorisation of these alum sludges in construction materials by carryingout physico-chemical characterisation tests. Chemical, mineralogical, spectral, microscopic and wettability studies were performed on these alum sludges. The results of the chemical composition through inductively coupled plasma optical emission spectrometry (ICP-OES) analysis shows that the most abundant oxides in alum sludges are silica (SiO2), alumina (Al2O3) and iron oxide (Fe2O3) with respective proportions of 50.80%, 36.57% and 10.32%. Potassium oxide (K2O), sodiumoxide (Na2O) and titanium oxide (TiO2) are onlypresent in small quantities. Mineralogical analysis by X-ray diffraction (XRD) reveals that the alum sludges are mainly composed of poorly crystallised kaolinite (78%). Minorphases such as hematite (9.3%), illite (7.2%) and quartz (4.5%) were also detected. Infrared spectroscopy reveals the presence of absorption bands at 688.778 and 743 cm-1, 1007, 1013 and 1077 cm-1 characteristics of clays in kaolinite form. Microscopic observation shows a microporous and amorphous structure of these clayey sludges. The high value of water demand (1133 µL/g) favors a good reactivity of these sludges in aqueous solution. These characterisations indicate that alum sludges of Sinématiali are highly suitable for incorporation with Portland cement in the production of refractory construction bricks, as well as mortars and reinforced concretes.