Lead ion sorption by perlite and reuse of the exhausted material in the construction field

This paper deals with the possibility of using perlite as a lead ion sorbent from industrial wastewater. Dynamic (laboratory column) operations were carried-out using beads, which were percolated by metals in a 2-10 mg·L-1 concentration range. To this purpose, lead ion solutions were eluted in columns loaded with different amounts of sorbent (2-4 g) within a 1-2 mm bead size range, at 0.15-0.4 L·h-1 flow-rates. Tests were performed to complete sorbent exhaustion (column breakthrough). The highest retention was obtained at 0.3 L·h-1, with 4 g of perlite and 10 mg·L-1 of influent, lead ion concentration. Film diffusion control was the kinetic step of the process in the Nerst stationary film at the solid/liquid interface. At the end of the sorption, perlite beads were used as lightweight aggregates in the construction field (i.e., for the preparation of cement mortars). Specifically, conglomerates showing different weights and consequently different thermal insulating and mechanical properties were obtained, with potential applications in plaster or panels.