Charge distribution multi-site complexation (CD-MUSIC) modeling of Pb(II) adsorption on gibbsite

Lead adsorption on gibbsite was examined in batch experiments as a function of pH, adsorption density (ΓPb 0.01–3.0 μmolm−2), initial Pb(II) concentration (0.77–78 μM), electrolyte type and its concentration. The pHzpc of gibbsite in NaCl was 8.35. The Pb(II) and H+ adsorption data on gibbsite were interpreted in terms of surface complexation using charge-distribution multi-site complexation (CD-MUSIC) model. Intrinsic equilibrium constants were determined by numerical optimization using ECOSAT-FIT utility resulting in the following data:>AlOH2 s1/2+Cls−=>AlOH2+1/2 Cl− log K−=−0.592(>AlOH−1/2)+Pb2+=[(>AlOH).20.2 Pb0.8]+CD-MUSIC — three-plane model (TPM): log KNaCl=9.38 or log KNaNO3=10.07CD-MUSIC — basic Stern-layer model (BSM): log KNaCl=9.70 or log KNaNO3=10.07.The binding constant of the [(>AlOH)x2Pby]2+surface complex (x+y=2) was determined independently using Pb(II) adsorption data in NaNO3, and NaCl differed only by 0.0.23 log units when the CD-MUSIC/BSM model combination was used.