Removal of heavy metals such as aluminum and strontium from brine in one step
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This post was last edited by sunjl1981 on 2013-1-6 22:02. How are heavy metals such as aluminum and strontium removed from single-salt water? These heavy metals accumulate in the saltwater cycle; what processes or additives can be used to remove them? # hcbbs
Sr and Ca belong to the same group; by controlling the excess amount of Na2CO3, it is possible to remove them. Resin columns can also be used to remove Sr, but dealing with Al is more complicated, as there are no effective methods for that. . .
Sr2+, as well as aluminum in combination with other elements, are cations that are harmful to membranes. The impact of strontium ions on membranes requires that their mass fraction not exceed 5×10^7. The effects of strontium ions are as follows: ① It reduces current efficiency and exists in the form of Sr(OH)2 deposits on the cathode side. Sr(OH)2 is more soluble than Ca(OH)2, and its impact on current efficiency is smaller than that of Ca(OH)2; at a strontium ion mass fraction of 5×10^-6, the monthly current efficiency decreases by 3%. ②When the mass fraction of strontium ions in the brine fed into the tank is 5×10^-6, the voltage increases by 50 mV per month. The methods for controlling strontium ions include: ① Treatment through reaction, clarification, and filtration ； ②After treatment with ion exchange resin, it is ensured that the relationships among various impurities in the brine are as follows: W(Ba2+ ) > W(Sr2+ ) > W(Ca2+ ) > W(Mg2+ ). Effect of aluminum on the film: The aluminum content is required to be below 10^7. The forms in which aluminum exists are: ① present in salts as clay together with silicon ； ②In a three-effect evaporator, salt brine is evaporated under reduced pressure to produce pure NaCl; aluminum forms precipitates with silicates and sodium, which reduces current efficiency. There are two forms of aluminum accumulation in the membrane: ① It enters the membrane in the form of cations, and converts to anions as the pH increases ； ②It accumulates in the membrane in an anionic form, similar to silicon. The method for controlling aluminum is to remove clay using a clarifying agent or in a filter. For more details, please refer to the 2007 issue No. 7 of \"Chlor-Alkali Industry\": The Influence of Impurity Ions in Brine on Ion Exchange Membranes — Liu Lichu