The invention relates to a process for the production of silicon and alumina Aluminium is contacted with a molten slag of a calcium oxide and SiO.sub.2 under conditions facilitating an aluminothermic reaction, thereby forming silicon and an aluminate slag in two phases which are separated. The aluminate slag is converted to alumina and calcium oxide, which is re-fed in the reaction. The aluminium is provided by melting of aluminium scrap or a combination of different aluminium alloys at a temperature of 700 to 1000° C. The primary aluminium melt is adjusted to a content of 8 to 14% of silicon and then cooled to below 660° C., whereby precipitates are formed, and high purity aluminium is obtained to be introduced into the reaction.

A method for treatment of an industrial effluent with aluminum, comprising: the effluent to be treated is carried to a first zone constituted by a tank having a pH of less than 9.5, so as to promote precipitation of the aluminum in aluminum hydroxide form and to facilitate its removal; a second zone is available and the recirculation of a part of a medium located in the zone 1 to the zone 2 and then return to the zone 1, and the injection of gaseous CO.sub.2 into the recirculated medium, are arranged; the solid particles formed in the zone 1 are separated and discharged; wherein in view of the recirculation of the medium where CO.sub.2 has been injected, the amount of dissolved CO.sub.2 available in the zone 1 is 0.5 to 3 times greater than the requirement necessary for the precipitation of the incoming effluent.

A method for the production of aluminium hydroxide (Al(OH)3) is described wherein in a first tank a first aqueous solution of sodium aluminate (NaAl(OH)4) is provided and carbon dioxide (CO2) gas is added to the first tank to form a first aluminium hydroxide precipitate, and wherein a second tank containing a second aqueous solution of sodium aluminate is provided, wherein the sodium aluminate solution in the second tank is supersaturated and seed crystals are added to the second tank to form a second aluminium hydroxide precipitate. At least a fraction of the first aluminium hydroxide precipitate obtained from the first solution in the first tank is seeded into the second tank and/or at least a fraction of the second aluminium hydroxide precipitate obtained from the second solution in the second tank is seeded into the first tank.

A method for treatment of an industrial effluent with aluminum, comprising: the effluent to be treated is carried to a first zone constituted by a tank having a pH of less than 9.5, so as to promote precipitation of the aluminum in aluminum hydroxide form and to facilitate its removal; a second zone is available and the recirculation of a part of a medium located in the zone 1 to the zone 2 and then return to the zone 1, and the injection of gaseous CO.sub.2 into the recirculated medium, are arranged; the solid particles formed in the zone 1 are separated and discharged; wherein in view of the recirculation of the medium where CO.sub.2 has been injected, the amount of dissolved CO.sub.2 available in the zone 1 is 0.5 to 3 times greater than the requirement necessary for the precipitation of the incoming effluent.

A method for treatment of an industrial effluent with aluminum, comprising: the effluent to be treated is carried to a first zone constituted by a tank having a pH of less than 9.5, so as to promote precipitation of the aluminum in aluminum hydroxide form and to facilitate its removal; a second zone is available and the recirculation of a part of a medium located in the zone 1 to the zone 2 and then return to the zone 1, and the injection of gaseous CO.sub.2 into the recirculated medium, are arranged; the solid particles formed in the zone 1 are separated and discharged; wherein in view of the recirculation of the medium where CO.sub.2 has been injected, the amount of dissolved CO.sub.2 available in the zone 1 is 0.5 to 3 times greater than the requirement necessary for the precipitation of the incoming effluent.

A pseudo-boehmite has a ratio of crystalline sizes D.sub.(130) and D.sub.(020) at a ratio of D.sub.(130)/D.sub.(020)=1.0-1.5, preferably, 1.1-1.3. A preparation method of the pseudo-boehmite, a catalytic cracking catalyst containing the pseudo-boehmite, and a preparation method and application of the catalytic cracking catalyst are provided. The pseudo-boehmite is applied to a catalytic cracking catalyst, and can produce a significant mesopore distribution in case that the catalyst strength is qualified, significantly improving the pore structure of the catalyst, which is of great significance for promoting the efficient diffusion of heavy oil macromolecules, reaction intermediates and product molecules in the catalyst, reducing the coke yield, and optimizing the product distribution.

A pseudo-boehmite has a ratio of crystalline sizes D.sub.(130) and D.sub.(020) at a ratio of D.sub.(130)/D.sub.(020)=1.0-1.5, preferably, 1.1-1.3. A preparation method of the pseudo-boehmite, a catalytic cracking catalyst containing the pseudo-boehmite, and a preparation method and application of the catalytic cracking catalyst are provided. The pseudo-boehmite is applied to a catalytic cracking catalyst, and can produce a significant mesopore distribution in case that the catalyst strength is qualified, significantly improving the pore structure of the catalyst, which is of great significance for promoting the efficient diffusion of heavy oil macromolecules, reaction intermediates and product molecules in the catalyst, reducing the coke yield, and optimizing the product distribution.

A mesoporous pseudo-boehmite rich in surface hydroxyl groups and a preparation method thereof are provided. A catalytic cracking catalyst contains the mesoporous pseudo-boehmite is prepared and used in catalytic reactions. The pseudo-boehmite has a most probable pore size greater than 4.5 nm and not more than 12 nm.

A mesoporous pseudo-boehmite rich in surface hydroxyl groups and a preparation method thereof are provided. A catalytic cracking catalyst contains the mesoporous pseudo-boehmite is prepared and used in catalytic reactions. The pseudo-boehmite has a most probable pore size greater than 4.5 nm and not more than 12 nm.