Sustainable Management of Salt Slag

Abstract

The management of salt slag, a waste from the secondary aluminum industry, is associated with huge environmental concerns due to the risk of atmospheric pollution (emission of toxic gases), groundwater contamination (high salt content that can percolate and cause an increase in salinity) and soil unavailability (large extensions required for disposal). Therefore, the development of a sustainable process for its treatment and recovery is of the utmost importance. In this work, a two-step process for the valorization of salt slag was developed that rendered zeolite as the main added-value product and NaCl and NH3 as byproducts. First, salt slag was hydrolyzed at 90 °C and at a solid/water ratio of 1/3. More than 90% of salt and ~90% of ammonia were recovered. In a second step, the hydrolyzed slag was completely transformed into a NaP zeolite under mild hydrothermal conditions. The zeolite exhibited specific surface area (17 m2 g−1), cation exchange capacity (2.12 meq g−1) and zeta potential (−52 mV) values that represent good characteristics for use in the removal of metal ions from aqueous effluents. The transformation of salt slag into zeolite can be considered a sustainable process with a high contribution to the circular economy.

High value-added utilization of secondary aluminum ash & carbide slag: preparation of a high-performance adsorbent for rapid removal of fluoride from wastewater

“…Primary aluminum ash usually refers to waste residue generated during raw aluminum electrolysis or aluminum casting, with an elemental aluminum content of up to 80%, which is usually recovered by remelting. 12 The waste generated in this process is named SAA. Even though the aluminum content of secondary aluminum ash is obviously lower than that of primary aluminum ash, the total mass of aluminum containing phases is still more than 50% with a large utilization value.…”

Lca of Recycling Aluminium Incineration Bottom Ash, Dross and Shavings in a Rotary Furnace and Environmental Benefits of Salt-Slag Valorisation

“…An alternative to tackle this issue is to valorise the salt slag residues by crushing and dissolving the salts in water (Delgado Sancho, 2017). Examples of salt-slag valorisation processes have been previously investigated in (Padilla et al, 2022) (Li et al, 2013). The present study considers the industrial valorisation of the salt-slag into, on one side, salts and Al concentrates which can be fed back into the rotary furnace, and on the other side ammonium sulphate with application in fertilizers (Rodrigues et al, 2022) and NMCs which the chemical or construction industries can use.…”