Simultaneous adsorption of Cd, Cr, Cu, Pb, and Zn by an iron-coated Australian zeolite in batch and fixed-bed column studies

•Iron-coated zeolite (ICZ) had higher adsorption than zeolite for Cd, Cr, Cu, Pb, Zn.•Adsorption capacity for Cu, Cd, Zn, Cr decreased at high mixed metals concentration.•Adsorption capacity in batch and column studies: Pb > Cu, Cd > Zn, Cr.•0.1 M HCl efficiently desorbed metals from ICZ with a small % Fe dissolution.•Data fitted to Langmuir, pseudo-first order, pseudo-second order, and Thomas models.

Excessive levels of heavy metals in water are an environmental hazard. An Australian zeolite with (ICZ) and without (Z) iron-coating, was used to remove five heavy metals from aqueous solutions using adsorption in batch and column experiments. The batch study showed that the Langmuir adsorption capacities of heavy metals on Z and ICZ at pH 6.5 and ionic strength 10−3 M NaNO3 were in the order Pb > Cu > Cd > Cr, Zn for single metal (5.0–11.2 mg/g) and for mixed metals solution (3.7–7.6 mg/g). The data for the kinetics of adsorption satisfactory fitted to both the pseudo-first and second order models with fits slightly better for the latter model. Data fitted to a diffusion model revealed that adsorption took place in two or more than two different stages: a fast external surface adsorption, and a gradual adsorption controlled by both film diffusion and intra-particle diffusion. The column adsorption data were fairly well described by Thomas model, with the order of Thomas adsorption capacity following a similar trend as in the batch study. In both batch and column experiments, the adsorption capacities were higher for ICZ than for Z and were generally lower in mixed metals system than in single metals system. Leaching of used ICZ columns with 0.1 M HCl, resulted in 64–93% of adsorbed metals being desorbed, and 10% of Fe being dissolved from the ICZ.