Abstract
The removal of Acid Black 1 dye was investigated by acid treated pumice stone as a low cost adsorbent, since acidic
modifications were expected to improve the sorption capacity. The main components of the considered adsorbent were SiO2 and
Al2O3 and acid treated pumice shows irregular structure. The effect of various parameters such as the initial dye concentration,
the contact time, the temperature and the pH were studied. An increase of the contact time, the initial dye concentration or an
acidification of the medium had a positive impact of dye removal. Among the tested isotherms, linear regression analysis showed
that the removal of Acid Black 1 dye follows a Temkin model (r2>0.93). The value of the separation factor (RL) was 0.17,
showing a favorable adsorption. Despite a low specific area (54m2/g), pumice stone displayed a high sorption capacity (72.46
mg/g), which should be related to its high porosity (85 %). The fitting of experimental time-course data showed that kinetics
followed a pseudo-second order model (r2>0.99). Mass transfer coefficient was determined at various initial dye concentrations
and showed external mass transfer cofficient values in the range of 10-3-10-4 (cm/s), namely in agreement with the values
reported in the available literature. Thermodynamic study demonstrated an exothermic adsorption, which however was not
spontaneous. pH and heating methods were tested for dye desorption and confirmed the relevance of pumice stone for dye
removal, since the heating method led to 83 % pumice regeneration.