Ion exchange method

Ion exchange method for silica sol precision casting. The cation exchange resin uses strong acid styrene cation exchange resin; the anion exchange tree refers to the weak basic styrene anion exchange resin.


Ion exchange is an equilibrium reaction. The process of the reaction is that when a silicic acid solution containing Na + is passed through the exchange tree finger, Ma + replaces H + on the cation exchange resin. Therefore, NAa + in the water glass has been removed, and H + cations, silicon ions and SiO3 in sodium silicate form an active dilute solution of silica sol and flow out.


      The ion exchange quality of silica sol is related to the following factors: degree of resin regeneration, balance properties, resin height, inflow depth, ion size, etc. The silica sol passed through the cation exchange column is diluted and then passed through the weakly basic anion resin exchange column to remove the anion CL- in the liquid to achieve a more stable state. The dilute silicon deep gum flowing out of the exchange column has a very low concentration and needs to be concentrated. In order to prevent gelation during concentration, a stabilizer must be added quickly before concentration. The stabilizer is often MOH (M is L, Na, K, Rb, Cs, NH4.NH2, etc.). The amount of stabilizer should be appropriate. If it is less than 1% of the moles of SiO2, it is difficult to play a stabilizing role; if it exceeds 5% It will reduce the purity of the product. Take 5kg of the above silica sol and adjust the PH value to 78 with 10% NAOH solution. Take 900 g of adjustment liquid and fill it into a pressure reducer to carry out the concentration under reduced pressure. And on the principle of keeping the liquid level in the container constant, slowly add the remaining 4100g of adjustment liquid. The concentration temperature was maintained at 78 ° C, and 900 g of silica sol containing SiO220% and Na200.33% PH of 9.6 was prepared, and the average particle size was about 16 mum.


The ion exchange resin has lost its exchange capacity after ion exchange. Need to wash with dilute hydrochloric acid and replace Na + on the resin with H9 + in HCL. The active groups of the ion exchange resin are oxidized to regenerate the resin and restore the exchange capacity. After regeneration, the ion exchange tree means that it must be rinsed with distilled water to the specified PH value for the next use.

Technical performance of silica sol: SiO2 content 20% 30% (H2SiO3 content> 26%) moisture 70% 80% specific gravity 1.141.21 Na2O content 0.4% 0.5% viscosity (coating 4) 10.9S can be stored for one year


Post time: Apr-20-2020
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