An iron-bearing material deriving from surface finishing operations in
the manufacturing of cast-iron components demonstrates potential for
removal of heavy metals from aqueous waste streams. Batch isotherm and
rate experiments were conducted for uptake of cadmium, zinc, and lead
. In the pH range of 4-7, the iron sorbent had the highest capacity, o
n a mass-per-mass basis, for lead followed by zinc and cadmium. As ant
icipated, solution pH has a notable impact on metal removal, while ion
ic background and initial metal concentration exhibited a lesser impac
t on adsorptive behavior. Metal surface complexation with a developing
oxide layer is postulated as the principal mechanism of heavy metal r
emoval. Batch adsorption kinetics are quite rapid, with 90% or more of
metal uptake occurring within the first 5-10 h of reaction for powder
ed fines. Larger, granular-sized particles exhibited a longer, slower
approach toward the equilibrium position. Surface complexation as well
as semi-empirical equilibrium and rate models provided a useful descr
iption of experimental phenomena in that conditional trends were refle
cted in the estimated values of the model coefficients. Given the avai
lability and comparable metal uptake capacity of the recycled iron sor
bent to natural metal oxides and some commercial adsorbents, use of th
e iron-bearing material offers potential environmental and economic be
nefit for certain industrial pretreatment applications. Copyright (C)
1996 Elsevier Science Ltd