Waste Water from the Production of Titanium Products as a Raw Material for the Ti(OH)4, NaOH and HCl Production

The study of the spent acidic pickling solution (SAPS) processing is presented. The solution is formed in the process of etching titanium products with hydrochloric acid. The processing includes the stages of neutralizing the SAPS with alkali, filtration and drying of the titanium hydroxide precipitate, electrochemical processing of the filtrate containing sodium chloride in an electrolyzer with ion-exchange membranes. The electrolysis process produces sodium hydroxide and hydrochloric acid. The proposed scheme for processing the SAPS makes it possible to obtain titanium hydroxide, sodium hydroxide and hydrochloric acid. Titanium hydroxide can be used in various industries. Alkali can be used in the SAPS neutralization process. Hydrochloric acid after the adjustment is suitable for use in the etching of titanium products.

Comparative Technical-and-Economical Evaluation of Production Costs of Coagulant from Technical-Grade Aluminum Hydroxide and Hydroxide Sluge

A comparative techno-economic estimate of the cost of HOAC producing from technical aluminum hydroxide and hydroxide sludge showed that the cost of HOAC would be decreased by 11% by using a hydroxide precipitate. The cost of operation on the hydroxide precipitate will decrease by 17.3% provided the storage vessel is converted into a reactor to neutralize the acid solution of HOAC. This is possible due to doubling the production of HOAC, moreover production volumes will amount to 7178.2 thousand rubles. The calculated payback period for capital investments for retrofitting is 1 month. Keywords: coagulant, aluminum hydroxychloride, hydroxide precipitate, aluminum- containing waste

Recovery of Cobalt from the Residues of an Industrial Zinc Refinery

The electrolytic production of metallic zinc from processing zinc sulfide concentrates generates a residue containing cadmium, copper, and cobalt that need to be removed from the electrolytic zinc solution because they are harmful to the zinc electro-winning process. This residue is commonly sent to other parties that partly recover the contained elements. These elements can generate revenues if recovered at the zinc plant site. A series of laboratory tests were conducted to evaluate a method to process a zinc plant residue with the objective of recovering cobalt into a salable product. The proposed process comprises washing, selective leaching, purifying and precipitation of cobalt following its oxidation. The process allows the production of a cobalt rich hydroxide precipitate assaying 45 ± 4% Co, 0.8 ± 0.2% Zn, 4.4 ± 0.7% Cu, and 0.120 ± 0.004% Cd at a 61 ± 14% Co recovery. Replicating the whole process with different feed samples allowed the identification of the critical steps in the production of the cobalt product; one of these critical steps being the control of the oxidation conditions for the selective precipitation step.

Synergistic effect of organic acid on the dissolution of mixed nickel-cobalt hydroxide precipitate in sulphuric acid solution

The synergistic effect of an organic acid on the dissolution of nickel and cobalt from a mixed nickel-cobalt hydroxide precipitate (MHP) in sulphuric acid solution was studied. The effects of sulphuric acid concentration, the type of organic acid, leaching time, leaching temperature and stirring speed on the dissolution of the metals were experimentally investigated. It was observed that there is no beneficial effect of leaching temperature and stirring speed on the dissolution of the metals from the used MHP product which contains 37.7% Ni, 2.1% Co and 5.6% Mn. It was found that citric acid was more effective than oxalic acid for the dissolution of nickel and manganese, whereas oxalic acid was more effective than citric acid for the dissolution of cobalt. The addition of oxalic acid into the leaching system, however, affected the dissolution of nickel negatively because nickel precipitate as nickel oxalate. Therefore, the use of citric acid as synergist for sulphuric acid leaching of MHP product is more promising. After 60 min of leaching, 90.9% Ni, 84.2% Co and 98.1% Mn were dissolved under the following conditions: 0.75 M sulphuric acid, 2 g citric acid, 1/10 solid-to-liquid ratio, 400 rpm stirring speed and 30 °C temperature. The experimental results demonstrate that the addition of citric acid as a synergist for sulphuric acid leaching of a MHP product provides beneficial effect for the dissolution of nickel, cobalt and manganese.

Fabrication of α-alumina by a combination of a hydrothermal process and a seeding technique

This paper describes a method for producing [Formula: see text]-Al2O3 at low temperatures by a combination of a hydrothermal process and a seeding technique. White aluminum hydroxide precipitate was prepared by a homogeneous precipitation method using aluminum nitrate and urea in aqueous solution. Peptization of the precipitate by acetic acid at room temperature transformed it into a transparent alumina sol. The alumina sol was treated with a hydrothermal process. [Formula: see text]-Al2O3 particles serving as seeds were added to the hydrothermally treated alumina sol. The sol containing the [Formula: see text]-Al2O3 particles was transformed into an [Formula: see text]-Al2O3-seeded alumina gel by drying at room temperature. The non-seeded alumina gel was amorphous or showed fine crystallites and began to crystallize into [Formula: see text]-Al2O3 at 900[Formula: see text]C. The [Formula: see text]-Al2O3-seeding promoted the crystallization of the alumina gel to [Formula: see text]-Al2O3. A remarkable [Formula: see text]-Al2O3 crystallinity was achieved with an increase in [Formula: see text]-Al2O3 particle content by weight in the final seeded alumina gel. For an [Formula: see text]-Al2O3 particle content of 5%, the seeded alumina gel was partially crystallized to [Formula: see text]-Al2O3 by annealing at temperatures as low as 600[Formula: see text]C.