alkaline leaching - biominewiki,alkaline leaching. from biominewiki. jump to: navigation, search. the process of dissolving soluble minerals from a solid ore or concentrate by means of an alkaline solvent. e.g. sodium hydroxide is used for dissolving aluminium from bauxite and leaching wolframite and scheelite ores..methods for alkaline recovery of aluminum from bauxite,this process is based on the alkaline leaching of aluminum-bearing ores (mostly bauxite) with sodium hydroxide solution. at this high ph value and elevated temperature and pressure, aluminum hydroxides from bauxite dissolve selectively as following eq..
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alkali leaching (e.g. bauxite ore) acid leaching (e.g. sulfide ore) chemistry. leaching is done in long pressure vessels which are cylindrical (horizontal or vertical) or of horizontal tube form known as autoclaves. a good example of the autoclave leach process can also be found in the metallurgy of zinc.
bauxite is the main ore of aluminum (al) and worldwide, more 95% of alumina is produced through traditional bayer process from bauxite. to produce one ton of alumina, it needs four metric tons of bauxite and consequently generate more than two metric tons of a highly saline and alkaline bauxite residue called “red mud”.
the separation of the alumina from the impurities in the bauxite ore is usually accomplished by the bayer process. in this process the ground bauxite is leached with caustic soda (naoh) to produce soluble sodium aluminate (naalo2), leaving the impurities in the insoluble residue. the aluminate solution is then decomposed producing al (oh)3
processing of bauxite to extract alumina produces a strongly alkaline waste, bauxite refining residue, which is commonly stored in engineered structures. once full, these waste dumps must be revegetated. in many alumina refineries, the waste is separated into
bauxite residue is a by-product of the bayer process. it is primarily composed of the insoluble fraction of the bauxite ore that remains after extraction of the aluminium-containing components. iron oxides (10 – 30%), titanium dioxide (2 – 15%), silicon oxide (5 – 20%) and undissolved alumina (0 – 20%) make up the residue, together with
alkali leaching generally, alkaline leaching works more selectively. in addition, it is considered cost-effective, quick and fast to operate and handle the extraction of zinc from oxidised zinc ores or waste, it can hardly be leached out in alkaline media for impurities such as fe, cu, cd, co , ni, etc. and its lower energy usage in the electrowinning process compared to acidic electrowinning
almost all commercial bauxite has alkali feldspar charnockite (afch) content 50-55% . depending on the type and nature of the solid material as well as the reaction conditions during the leaching process of bauxite ore with sulfuric acid the following reactions may occur .
a series of column leaching tests were performed to evaluate the behavior of reactive mine tailings amended with alkaline-additions under dynamic conditions. column tests were conducted of oxidized mine tailings combined with cement kiln dust, red mud bauxite, and mixtures of cement kiln dust with red mud bauxite.
leaching assessment methodologies for disposal and use of bauxite residues. bauxite residue, or red mud, is the largest environmental concern of alumina refineries because of the production rate of the waste stream and its alkaline nature. therefore, the aluminum
non-oxidative leaching involves a chemical dissolution process using water, acid or an alkali as reagent. some examples are the dissolution of oxidized copper ore (cusio 3.2h 2 o) or zinc calcine (zno) using sulfuric acid (h 2 so 4) as reagent and the leaching of bauxite with sodium hydroxide (naoh):
minium hydroxide and hydrated silicate in bauxite during alkali leaching, used in the bayer process.1,2,15,16 by compar-ison, in the kaolinite structure, silica is also present as [sio 4] 4− units, which replaces some of the [alo 3] 3− units. for each of these substitutions in
(1) leaching of bauxite using concentrated naoh solution gives sodium aluminate and sodium silicate (2) the hall-heroult process is used for the production of aluminium and iron (3) pig iron is obtained from cast iron (4) the blistered appearance of copper during the metallurgical process is due to the evolution of co 2
processing of bauxite to extract alumina produces a strongly alkaline waste, bauxite refining residue, which is commonly stored in engineered structures. once full, these waste dumps must be revegetated. in many alumina refineries, the waste is separated into fine-textured red mud and coarse-textured residue sand (rs).
processing of bauxite to extract alumina produces a strongly alkaline waste, bauxite refining residue, which is commonly stored in engineered structures. once full, these waste dumps must be revegetated. in many alumina refineries, the waste is separated into fine-textured red mud and coarse-textured residue sand (rs). the sand component has physical characteristics that make it a suitable
bauxite a1,03 31120(0+201-1-(aq) 2a102-(aq)+41-120 alkali leaching (bayer process) 18 steam washing calcanatatm 14111221' fli&wag sand preparnaort fine residue separaion _761 cooling vs area water sand mashing is at: residue ,washing realdue
water-soluble alkali in leachate directly affects the physical and chemical properties of bauxite residue and suppresses plants growth (xue et al., 2016). as can be seen from fig. 3 a , for ck, ar, and pva treatments, the concentration of oh − in leachates decreased sharply from day 3 to 9, slowly decreasing from day 15 to 21, and then becoming relatively stable from day 21 to 30.
cite this article as: hong-fei wu, jun-qi li, chao-yi chen, fei-long xia, and zhen-shan xie, suspension calcination and alkali leaching of low-grade high-sulfur bauxite: desulfurization, mineralogical evolution and desilication, int. j. miner.metall.
increasing volumes of bauxite residues and their associated leachates represent a significant environmental challenge to the alumina industry. constructed wetlands have been proposed as a potential approach for leachate treatment, but there is limited
the known method (a.s. ussr №1188101) leaching of bauxite, which eliminated this disadvantage. this is achieved by the fact that, since approximately a fifth of the autoclave battery during pulp (just the battery 8-10 connected in series autoclaves), is preheated slurry steam chp (the pressure of 25-30 mpa) in the capacitors installed in the upper part perechodnik pipes between the reaction
a column leaching experiment was used to investigate the efficacy of amendments on their ability to remove alkaline anions and metal ions from bauxite residue leachates. treatments included, simulated acid rain (ar), phosphogypsum + vermicompost (pvc), phosphogypsum + vermicompost + simulated acid rain (pva), and biosolids + microorganisms (bsm) together with controls (ck).
yi-wei li, jun jiang, sheng-guo xue, graeme j. millar, xiang-feng kong, xiao-fei li, meng li and chu-xuan li, effect of ammonium chloride on leaching behavior of alkaline anion and sodium ion in bauxite residue, transactions of nonferrous metals society of china, 10.1016/s1003-6326(18)64857-5, 28, 10, (2125-2134), (2018).
in the leaching method, bauxite ore is digested with a concentrated solution of naoh that produces 'x'. when c o 2 gas is passed through the aqueous solution of 'x', a hydrated compound 'y' is precipitated.
red mud, formally termed bauxite residue, is an industrial waste generated during the processing of bauxite into alumina using the bayer process.it is composed of various oxide compounds, including the iron oxides which give its red colour. over 95% of the alumina produced globally is through the bayer process; for every tonne of alumina produced, approximately 1 to 1.5 tonnes of red mud are
leaching of rare earths from bauxite residue (red mud) the alkali fusion was carried out by mixing 0.5 g of bauxite residue with 1.5 g of sodium carbonate and 1.5 g of sodium tetraborate decahydrate, followed by heating the mixture in a platinum crucible at 1100 c for 30 min.