Dolomite powder from Ouled Mimoun, Tlemcen (western region of Algeria) was thermally treated within
the temperature range 450–1000 °C. The modifications undergone by dolomite, inherent to thermal
treatment, were investigated from X-ray diffraction patterns. The results were also discussed using scanning
electronic microscopy and nitrogen adsorption. The XRD data, analysed from X Pert Plus program, showed
that the dolomite phase ceases at 700 °C and is relayed by the formation of in situ calcite and periclase. The
crystallographic parameters of these two phases tend towards that of pure periclase and calcite at 1000 and
900 °C, respectively. SEM analysis indicated that the morphological properties were profoundly affected.
SEM images of D-1000 (sample treated at 1000 °C) indicated that the original particle shape of dolomite
(presence of discrete grains having sharp edges with presence of cleavages) was totally destroyed, leading to
small spherical particles with a diameter of 0.1 μm. The specific surface area value of D-1000 increased more
than 6 times against that of the raw dolomite. Adsorption of azo-dye Orange I from aqueous solutions onto
untreated and treated dolomites was also reported. The isotherms were of L-type. The interaction was
explained by electrostatic considerations between sulfonate groups of the dye (D-SO3Na), which are
dissociated in the aqueous system, and positively charged adsorption sites. The affinity of orange I for the
dolomitic solids follows the sequence D-900 N D-1000 N D-800 N N D-600 N raw dolomite. The maximum
retention capacity shown by D-900 was explained and correlated with its crystallographic properties.
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