The invention relates to a process for obtaining material of value from a bauxite residue which is obtainable or has been obtained by the Bayer process. This process comprises the steps of a) providing an aqueous suspension of the bauxite residue, b) setting a pH of the suspension to a value between 7.2 and 12.2, c) at least partly deagglomerating suspended mineral agglomerates of the bauxite residue, and d) separating the resulting mixture into an iron-rich fraction and into at least one further, preferably silicate-rich fraction. The invention further relates to an apparatus (10) for carrying out the process.

The invention relates to the metallurgical industry, specifically to the acid treatment of red mud obtained in the process of producing alumina, and can be used in technologies for recycling waste from alumina refinery holding ponds. The method for the acid treatment of red mud involves leaching using a leaching agent comprised of water-soluable aliphatic carbonic acids having fewer than 3 carbon atoms per molecule, filtering the solution, and separating the recoverable end products. To ensure a high level of recovery of valuable components and the increased productivity of the process, leaching is conducted with the addition of red mud in portions and with the control of pH values, and when a target pH value of between 2.3 and 3.8 is reached, no more red mud is added, and once leaching is complete, the solution is kept at a given leaching temperature for no less than one hour.

Methods and compositions for improving performance of flocculants in an industrial production process. Methods include pH triggered cross-linking reaction between a flocculating agent, such as dextran, and a composition comprising a boronic acid-containing polymer. The pH trigger can be provided by a fluid having a pH of 8 or more. The production process can be a Bayer Process and the fluid is caustic liquor or slurry in the fluid circuit of the Bayer, wherein the reaction time is reduced over conventional methods and the cross-linked dextran composition effectuates improved flocculation of the trihydrate particles.

The present invention discloses a method for aluminum-enhanced dealkalization of red mud and separation and recovery of aluminum and iron. The method includes: dissolving red mud in water, introducing excessive SO.sub.2, introducing O.sub.2 for aeration, and refluxing part of alkaline leachate after filtering; when pH of a red mud mixture decreases to below 3, washing and filtering the red mud mixture, adding NaOH to acidic leachate to adjust its pH to a strongly alkaline level, aging and filtering the leachate, treating filter residue to recover Fe.sub.2O.sub.3, and refluxing part of alkaline leachate after filtering to the red mud mixture; and adjusting pH of the remaining alkaline leachate after filtering to a weakly acidic level, and conducting filtering to recover aluminum.

A process disclosed herein is related to the isolation and purification of substantially pure chemicals, including silica gel, sodium silicate, aluminum silicate, iron oxide, and rare earth elements (or rare earth metals, REEs), from massive industrial waste coal ash. In one embodiment, the process includes a plurality of caustic extractions of coal ash at an elevated temperature, followed by an acidic treatment to dissolve aluminum silicate and REEs. The dissolved aluminum silicate is precipitated out by pH adjustment as a solid product while REEs remain in the solution. REEs are captured and enriched using an ion exchange column. Alternatively, the solution containing aluminum silicate and REEs is heated to produce silica gel, which is easily separated from the enriched REEs solution. REEs are then isolated and purified from the enriched solution to afford substantially pure individual REE by a ligand-assisted chromatography. Additionally, a simplified process using one caustic extraction and one acidic extraction with an ion exchange process was also investigated and optimized to afford a comparable efficiency.

Described herein is a method of adding one or more boronic acid functional compounds to a mineral ore to result in a treated mineral ore. Where the mineral ore is a bauxite ore, and the ore is subsequently processed according to the Bayer process to obtain alumina, adding a boronic acid functional compound to the bauxite ore or a Bayer product followed by processing the treated bauxite ore or treated Bayer product using one or more processes associated with the Bayer process results in an increased yield of alumina product, increased alumina content (purity) in the alumina product obtained, or both when compared to the same bauxite ore or Bayer product subjected to the same process(es) but in the absence of a boronic acid functional compound.

Disclosed is an accuracy compensation method for discharge caustic alkali concentration measuring device in evaporation process, comprising following steps: step 1. collecting process data of instrument values and laboratory values of alkali liquor diopter, temperature and caustic alkali concentration in the evaporation process; step 2. performing sliding average filtering, time series matching and normalization on the process data collected in step 1 to obtain preprocessed process data; step 3. inputting the preprocessed process data into an accuracy compensation model of the caustic alkali concentration measuring device to obtain compensation values; step 4. adding the compensation values of the caustic alkali concentration to the instrument values to realize on-line compensation of the caustic alkali concentration. The disclosed can accurately compensate the concentration value measured by the on-line instrument, and the compensated concentration value can follow the actual change trend; moreover, the measurement accuracy can meet the needs of actual production.

A tribo-electrostatic separation process for beneficiation of bauxite minerals is disclosed. The process may include one or more steps of grinding, drying, de-agglomeration, air classification and electrostatic separation.

The alunite ore processing method consists of crushing, grinding and flotation of raw alunite ore. The enriched alunite ore is roasted at 520 to 620 C., the roasting time is 1 to 3 hours. The roasted alunite is leached with 5 to 20% sodium carbonate solution, which is in 100 to 110% of the stoichiometric amount required to bond the SO.sub.3 aluminum sulfate in the alunite with leaching conditions of 70-100 C. for 0.5-2.0 hours. The obtained slurry contains all of the potassium sulfate from the alunite and all of the sodium sulfate obtained from sodium carbonate. In the insoluble residue remains all aluminium oxide and residual rock. The sulfate solution is separated from the insoluble residue and is converted with potassium chloride to potassium sulphate (fertilizer) and kitchen salt. The insoluble residue is treated by the Bayer method without the use of an autoclave and results in aluminium oxide (alumina) and quartz sand.

A settler for decanting mineral slurries includes a tank having a side wall, a bottom and a top, an outlet for a thickened slurry at the bottom of the tank, a first overflow outlet for withdrawing an overflow stream of a clarified liquid, a slurry inlet means for introducing fresh slurry into the tank, the slurry inlet means having a slurry opening through which fresh slurry joins a body of slurry in the tank, and a stirrer having a vertical axis around which the stirrer rotates or reciprocates, in said settler the slurry opening is displaced laterally relative to said vertical axis of the stirrer and said slurry inlet means comprises mixing means. A separation installation includes the above settler and a method for separating a clarified liquid from a thickened slurry of a mineral slurry.