Mechanochemical Processing of Blast Furnace Slag for its Reuse as Adsorbent

Mechanochemistry is a very interesting branch of chemistry for its potentiality in processes of environmental relevance. In this work, an innovative application has been proposed, namely to mechanochemically treat a blast furnace slag to be reused as a low-cost adsorbent. In particular, the adsorptive properties of this industrial waste towards methylene blue present in aqueous solutions have been considered. To this end, the slag has been treated in a planetary mill at different charge ratios, rotational speeds and milling times, and then characterized by laser granulometry, porosimetric and XRD analyses. These investigations allowed to shed light on the interrelationships between milling conditions and slag physico-chemical characteristics, and to choose the most interesting samples to submit to the following adsorption equilibrium and kinetic tests. These runs have been conducted at different dye initial concentration and adsorption times, and results have been interpreted according to the previously-analyzed slag characteristics. Furthermore, adsorption data have been post-processed to give values for the equilibrium and kinetic constants, the removal efficiency and the characteristic adsorption times.