Evaluation of the sorptive capacity of sugarcane bagasse and its coal for heavy metals in solution

Recycling of sugarcane bagasse and its coal as metal sorbents to capture metal ions from wastewater is the aim of this study. Thus, stability of sugarcane bagasse and its coal, in addition to the solubilities of metal ions in synthetic solution, were determined in this study at different pH values. Also, sorption of Fe, Mn, Cd, and Pb ions with different concentrations (10-100 mg L-1) on different grain size fractions of sugarcane bagasse (< 150 > mu m) and its coal (< 80 > mu m) was carried out under different pH values (2, 4 and 6), dosage (2, 6, and 10 g L-1), time intervals (15-300 min.) and temperature (20-50 degrees C). The results indicated that the sugarcane bagasse and its coal were more stable at pH 6, and the solubilities of metal ions in the synthetic solution exhibited high values at pH 2 more than pH 4 and 6, respectively. Generally, removal of metal ions using the sorbents increased with the decreasing of grain size fractions and with increasing of pH values (6 > 4 > 2), sorbent doses (10 > 6 > 2 g L-1) and initial concentrations of metal ions (10-100 mg L-1). Coal of sugarcane bagasse was more effective than the sugarcane bagasse for removal of the metal ions from solution. Positive values of Delta H degrees suggest the endothermic nature of sorption in all cases. The negative Gibb's free energy values indicate the feasibility of the process and spontaneous nature of sorption (Fe-bagasse coal system), while the positive value of Delta G degrees suggests the non-spontaneous character of adsorption of all metals. The negative values of entropy change AS' (Pb-bagasse system) indicate the highly ordered adsorption process in this case, while the positive values of Delta S degrees show the increased randomness at solid/solution interface during the sorption metal ion on bagasse. The results of activation energy values indicate the order of sorption feasibility is: Pb > Fe > Cd > Mn in the case of bagasse and Fe > Pb > Cd > Mn in the case of coal. Generally, the results of this study suggest that the sugarcane bagasse and its coal might provide an economical method for the removal of metal ions from wastewater.