Study of diatomite efficiency in removing of lead and cadmium from aqueous solutions in batch system

The presence of heavy metals in the environment, especially in water creates environmental problems. Effective technology to remove metals are using of adsorbents and some of adsorbents that economically, availability and high power to extract heavy metals better than others. In this study, sorption of Cd and Pb by diatomite (Iranian diatomite and French diatomite) from aqueous solutions, a batch experiment were conducted with various metal concentration (0 to 200 mg L-1) and 0.03M NaNO3 were applied as a background solution. Scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray Fluorescence (XRF) were used to characterize the adsorbents. The cation exchange capacity (CEC) values for Iranian diatomite and French diatomite were 80 and 15 cmol kg-1, respectively and surface area of diatomites were calculated as 55 and 23 (m2 g-1) , respectively. Adsorption data were fitted to Langmuir (R2=0.89-0.99), Freundlich (R2=0.81-0.98), Temkin (R2=0.80-0.98), Dubinin-Radushkevich (R2=0.83-0.97) and Elovich (R2=0.26-0.90) isotherm models. The results showed that the sorption affinity of Pb onto both adsorbents was greater than that of Cd. Also Iranian diatomite can adsorb more Pb and Cd than French diatomite. The maximum adsorption capacity (qmax) of Pb was 65.8 and 41.23 (mg g-1) for Iranian diatomite and French diatomite, respectively, and the maximum adsorption capacity (qmax) of Cd was 47.30 and 35.56 (mg g-1) for adsorbents, respectively. According to the results, abundant, locally available cheap minerals of Iranian diatomite showed a greater efficiency for removal of Cd and Pb from the aqueous solution, also can be used for water pollutants.