Sodium aluminate liquor

Recovery from Bayer Liquor. The significant amount of primary gallium is recovered from the alumina industry. The main source is the sodium aluminate liquor from Bayer-process plants that produce large quantities of alumina. Several methods have been developed to recover gallium from Bayer liquor. 

Tankwater, Bright dip acid (phosphoric), Cyanide rinse bath, Pickle Liquor, Sodium Aluminate Liquor, N.S.S.C. Liquor, Kraft Liquor, Soda Liquor, Sulfite Liquor, Stillage, Corn Syrup, Gelatin, Salt, Soybean Oil, Steepwater, Sugar, Whey, Mercerizing Caustic, Nylon Salt, Rayon Spin Bath, and Sodium Sulfate. 

Slaked lime is also added to the sodium aluminate liquor to control carbonate levels by eausticising sodium earbonate (31.16). It also helps to control the level of phosphates by precipitating hydroxyapatite (31.17) — phosphates can interfere with the subsequent precipitation of aluminium hydroxide. 

Precipitation. The clear sodium aluminate liquor is cooled down, diluted with the water from the red-mud wash, and acidified by bubbling carbon dioxide (CO ) gas through the solution. Carbon dioxide forms a weak acid solution of carbonic acid, which neutralizes the sodium hydroxide from the first treatment. This neutralization selectively precipitates the aluminum hydroxide [AlfOH),] but leaves the remaining traces of silica in solution the precipitation or the crystallization of the hydrate is also called decomposition. The liquor is... 

Chemical recovery ia sodium-based sulfite pulpiag is more complicated, and a large number of processes have been proposed. The most common process iavolves liquor iaciaeration under reduciag conditions to give a smelt, which is dissolved to produce a kraft-type green liquor. Sulfide is stripped from the liquor as H2S after the pH is lowered by CO2. The H2S is oxidized to sulfur ia a separate stream by reaction with SO2, and the sulfur is subsequendy burned to reform SO2. Alternatively, ia a pyrolysis process such as SCA-Bidemd, the H2S gas is burned direcdy to SO2. A rather novel approach is the Sonoco process, ia which alumina is added to the spent liquors which are then burned ia a kiln to form sodium aluminate. In anther method, used particulady ia neutral sulfite semichemical processes, fluidized-bed combustion is employed to give a mixture of sodium carbonate and sodium sulfate, which can be sold to kraft mills as makeup chemical. 

The product was digested with warm water, which dissolved the sodium aluminate and left the other materials as an insoluble residue. Passage of carbon dioxide through the clarified liquor precipitated aluminum as hydroxide ... 

To effectively remove carbonyl sulfide from a gas stream, special alkaline scrubbing liquors are used. These contain sodium aluminate or sodium plumbite, or they are made of alkalies with a hydrolysis catalyst based on Zn, Fe, Ni, or Cu. Diethanolamine, diglycolamine, or other alkanolamines (qv) mixed with water remove carbonyl sulfide from sour, ie, acid-gas-containing, gas streams (25,26) (see Carbon dioxide). 

In the process to produce alumina (Fig. 1), bauxite is crushed and wet ground to 100-mesh, dissolved under pressure and heated in digesters with concentrated spent caustic soda solution from a previous cycle and sufficient lime and soda ash. Sodium aluminate is formed, and the dissolved silica is precipitated as sodium aluminum silicate. The undissolved residue (red mud) is separated from the alumina solution by filtration and washing and sent to recovery. Thickeners and Kelly or drum filters are used. The filtered solution of sodium aluminate is hydrolyzed to precipitate aluminum hydroxide by cooling. The precipitate is filtered from the liquor, washed, and heated to 980°C in a rotary kiln to calcine the aluminum hydroxide. 

The cooled product is ground and extracted with water. The soluble sodium aluminate is removed as a filtrate from the dicalcium silicate and insoluble matter. Injection of carbon dioxide into the filtrate produces a precipitate of aluminium hydroxide and sodium carbonate liquor (11.10), which is recycled to the initial stage. The aluminium hydroxide is heated to above 300 °C to produce pure alumina which is dissolved in fused cryolite (NaAIp4) at about 900 °C and electrolysed between carbon electrodes to produce molten aluminium. 

Liquor Preparation. The aluminate solutions (synthetic Bayer liquors) were prepared using gibbsite (C31 Alcoa Chemical Division, Arkansas), sodium hydroxide pellets (AR Grade) and sodium carbonate (AR Grade) for sodium aluminate or with potassium hydroxide (AR Grade) and potassium carbonate (AR Grade) for potassium aluminate solutions. 

This represents a specialty filler which contributes to paper brightness, ink receptivity and acts as a flame retardant. The effect on flame retardancy can be explained by the 35% of bound water based on material weight. The bound water is released at temperatures above 150 °C. The raw material source for the production of aluminum trihydrate (ATH) is bauxite. Bauxite is a blend of AI2O3, Fc203, Si02, H2O, Ti02 and other minerals. To produce ATH it is necessary to stabilize the alumina content and to separate out the other minerals. This is done by the so-called Bayer process. After final filtration, the clear liquor of sodium aluminate is seeded with specially prepared fine crystals of ATH. This seeding causes the sodium aluminate to decompose to ATH or Al(OH)3 which forms a precipitate. 

The uranium anion present in carbonate solutions is [U02(C03)8] and this is associated with few other impurity anions. Absorption capacities as high as 100 to 200 mg/g of dried resin have been obtained on Amberlite IRA-400 2 and Dowex I , under conditions where competing anionic impurities such as phosphate and aluminate ions have only absorbed to an insignificant extent. The resin capacity, in both cases, is greatest at low sodium carbonate concentrations. Vanadate ion absorption can take place to an appreciable extent when vanadium is present in the carbonate leach liquor from the ore. It is, however, readily separated from the uranium, e.g. by a preliminary elution with a saturated solution of sulphur dioxide. This removes the vanadium from the resin by reducing it to a lower valency state. 

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