This paper continues the previous investigations regarding the technology for the Aluminum (Al) recovery as Al sulfate from black Al slag. Leaching is the next compulsory step in the Al extraction process. The paper studies the influence of mother solutions´ (MS) recirculation resulted from the process within the system over the quality of Al sulfate and the siliceous residue (R) and, the aluminum nitride (AlN) hydrolyses in the leaching process. The optimum parameters determined are: *the leaching yield of the slag that registers values between 56÷66 % and for the soluble Al 96-97%; *the quality of the products obtained from this technology which have significant coagulation properties; *the AlN decomposition which continues at the leaching phase but is lower than those achieved in the washing process. Besides, the (R) from the leaching process was inertized employing binder slag-cement or slag-lime into the proportion 7:3 binders: (R) ratio. The flow sheet of entire process is also presented. The experimental results were ultimately the purpose for the feasibility study, the economical analysis and the designing of a pilot plant (600t/year Al slag).

Washing black aluminum (Al) slag to obtain soluble salts is an important stage of the smelting slag treatment at technological process. This process is used to recover Al as a coagulant for water purification. This research aims at establishing the optimal conditions for washing (e.g. temperature (T), solid: liquid ratio (S : L), time, the recirculation waters in the system). The goal of research was to determine: a) the removal with maximum efficiency of the soluble salts from black Al slag; b) to increase the salt content in the washing waters; c) to decrease the water consumption. Besides, experiments were carried out to establish the washing parameters for quantitative recovery of Al sulfate out of acid leaching residue. X-Ray Powder Diffraction Phase Analysis has been performed for monitoring phase's composition of initial and final slag, after the washing process. Metallic Al and Aluminum Nitride (AlN) partially disappear from washed slag, resulting in formation of Al Hydroxides and Oxihydroxides. Also, the washing process, lead to complete removal of Halite and Sylvite. Experiments were carried out at the micro-pilot level. At the end, the flow sheet of the process for quantitative separation of soluble compounds from black Al slag is given.

The purpose of this work is to investigate the secondary Al slag (SAS) relating to its technical and environmental properties and, as consequence, to its compatibility with Portland cement matrix. This study may be a contribution to establish of SAS potential valorization as secondary raw material (SRM) in low strength cement matrix composites, as construction products. DRX mineralogical analyses revealed that SAS includes transition alumina compounds, especial boehmite. The hydration process evolution and the hydration products nature in the Portland cement-SAS systems were studied by measurement of the Ca 2+ concentrations and by DRX investigation. Also, was studied the ability of the Portland cement matrix to immobilize of the heavy metals contained of SAS, by a modified procedure of maximum available fraction-MAF leaching test. Conditioned SAS addition didn't disturb a positive evolution of the mortars compression strengths up to 360 days.

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