Mitigating the Environmental Impact by Synthesis of Adsorbents from Aluminium-Containing Waste

Abstract

Purpose To develop effective adsorbents and carriers for removing harmful impurities from waste, due to the shortage of natural bauxite for alumina production. Methods To determine the influence of various impurities present in the waste—spent alumina adsorbent (SAA) on the characteristics of adsorbents for chlorine-containing compounds, samples with a different content of V, Ti and Na have been synthesized. Properties of adsorbents based on a commercial alumina and extensively treated SAA, both types undergoing impregnation with sodium hydroxide and sodium vanadate, have been compared. Alumina adsorbents and alumina-kaolin-borate catalyst carriers with the Ti content of ca. 0.2% were prepared by atomic layer deposition (ALD) of TiCl4 on the ready granules, while introduction of large quantities of titania have been performed by addition of ground alumina-titania carrier waste into the extrusion paste. Adsorption of steam, tetrachloroethylene and hydrochloric acid has been investigated. Results and Conclusions It was found that the adsorption capacity for water vapor reached 43.6 g H2O/100 g SA and 38.9 g H2O/100 g AN-2, while after ALD modification it decreased by ca. 1 and 35%, respectively and with the introduction of SA-Ti(15.0) with the same amount of titanium by ca. 35%. Modification of AN-2 with sodium vanadate at about 0.3% Na and 0.4% V had no effect on water adsorption; while as the concentration of sodium introduced by impregnation with NaOH increased, the adsorption ability deteriorated. Modification of AN-2 and SA using ALD technology sharply diminished efficiency of adsorption of water vapors, tetrachlorethylene and hydrochloric acid. By adsorption of a mixture simulating reforming exhaust gases, formation of chlorinated oligomers on AKB, AN-2 and SA was established. NaOH modification effectively suppressed oligomerization; thus SAA-based adsorbents containing more than 5% Na can be used for drying and purification of reforming exhaust gases, as the most effective, cheapest and resource-saving option. Graphical Abstract