Removal of Lead From Aqueous Solutions Using Activated Alumina Timothy A. Kramer* Patrick D. Wootton, and Clifford R. Lange Department of Civil Engineering, 238 Harbert Engineering Center Auburn University, Alabama 36849‑5337 (*Corresponding author ph. (334) 844‑6277, fax (334) 844‑6290, e‑mail ‑ tkramer@eng.auburn.edu)

The removal of soluble lead species from aqueous solutions using powdered

activated alumina as a treatment technology was evaluated by equilibrium and kinetic

studies. Variables included pH, alumina particle size, and the presence of competing

background matrices. Solution pH was varied from 2.0 to 12.0, alumina particle sizes

ranged from <74 gm to >1190 gm in diameter, and the addition of the ions of acetic acid

and sodium chloride were explored. Soluble lead was obtained by adding a known amount

of lead nitrate to pure water. Alumina was crushed and sieved 7 ‑phase and subsequent

surface area for each size fraction was determined using the BET isotherm method. Surface

area measurements showed an approximate doubling between the <74 gm and > 1190 p.m

diameter particles, with the smaller particles having the greater surface area per unit mass of

alumina powder (300 m2/gm compared to ‑150 m2/gm).

Results indicated that solution pH was the most significant factor impacting both equilibrium capacity and the rate of lead sorption using activated alumina. Figure 1 displays these data where a pH of less than 7.0 does not remove all of the lead unless large amounts of alumina are added. The data of Fig. 1 was obtained using the small diameter particles (<74 mm diameter) without the presence of a competing matrix.

Surface area as defined by particle size also impacted the sorption capacity and rate of lead removal. Results of the study indicated that sorption rate was most positively influenced by the increase in available surface area, while equilibrium capacity was also increased, though not as significantly as sorption rate.

The influence of the presence of a competing background matrix was surprising, although explainable. The presence of 1.0 mM of acetic acid did not impact the sorption of lead in this study while small concentrations of sodium chloride (0.1 mM) reduced sorption rate. Modeling using surface complexation theory explains this behavior and is presented in the results.

Conclusions of the work indicate that the use of powdered activated alumina (<74 gm in diameter of particle size) is a viable treatment technology for the removal of soluble lead from contaminated waters. Further, the presence of organics, as shown by acetate ion does not negatively impact the removal. However, simple ions and ionic strength, as well as solution pH are the key variables in using this new approach for metals removal.