How to test ion exchange and test steps for cation exchange capacity

Ion exchange method is a method of removing harmful ions in wastewater by exchanging the ions on the ion exchanger and the ions in the wastewater. Ion exchange is a special adsorption process, usually reversible chemisorption; It is characterized by adsorption of ionized substances in water and ion exchange of equal charge.

Ion exchangers are divided into inorganic ion exchangers such as natural zeolite, synthetic zeolite, and organic ion exchangers such as sulfonated coal and various ion exchange resins.

When applying the ion exchange method for water treatment, it is necessary to design the ion exchange equipment according to the performance of the ion exchange resin, and determine the operation cycle and regeneration treatment of the exchange equipment. Through this experiment, the following objectives are achieved:

1) Deepen the understanding of the basic theory of ion exchange; Learn the identification of ion exchange resins;

2) Learn how to operate ion exchange equipment;

3) Learn to use a hand-held salinity meter, and master the calibration and measurement methods of pH meter and conductivity meter.

Second, the content and principle of the experiment.

Since ion exchange resins have exchange genes, the free exchangeable ions in them can be exchanged with homogeneous ions in water in equal amounts. The cations in the water are removed with an acid cation exchange resin and the reaction formula is as follows:

nrh + m+n → rnm + nh+

m – cation n – ionic valence.

r – exchange resin.

Anions are removed from water with alkaline anion exchange resin according to the following reaction formula:

nroh + y−n → rny + noh-

y – anion.

Ion exchange method is a special form of solid adsorption, so it can also be desorbed by desorption method for resin regeneration.

In this experiment, tap water was used as the inlet water for ion exchange treatment. Because tap water contains a large amount of yin and yang.

sub, such as Cl, NH4+, Ca, Mg, Fe, Al, K, Na, etc. These ions need to be removed from the water used in some industrial and agricultural production, scientific research, medical and health work, as well as in the advanced treatment process of some wastewater. Ion exchange resins are a feasible way to achieve the goal.

The adsorption capacity of cation exchange resins for alkali metals increases with the decrease of their hydrate ionic radius. According to the activity coefficient of alkali metals, the order of the adsorption capacity of cation exchange resins is C>Rb>K>NH+

4>na>li。

Some inorganic compounds have selective adsorption of alkali metals and can be used as ion exchangers.

Aluminum phosphate can adsorb rubidium and cesium in aqueous solution, and its separation coefficient is higher than that of synthetic resins. Rubidium and cesium on the exchange column can be eluted with dilute nitric acid and higher than 1mol of LHNO3, respectively.

In nitric acid solution, rubidium and cesium can be adsorbed by ammonium phosphomolybdate, separated from potassium, sodium and lithium, and then eluted with 2mol L and 6mol LNH4NO3 solution. When the potassium oxide content is less than 50mg, the rates of rubidium and cesium** are above 90%.

Under certain conditions, anion exchange resins can be used to separate alkali metals from each other, but in most cases they are used to separate other elements.

In hydrochloric acid solution, cobalt, zinc, iron, cadmium form a stable chloride anion, which can be adsorbed by a strong alkaline anion exchange resin, or after the above elements and vanadium and citric acid react, it can also be adsorbed by the anion exchange resin and separated from alkali metals.

Calcium, magnesium in the ethanol solution of EDTA, or some other bivalent metals in the presence of EDTA or acetate, can be adsorbed by anion exchange resin, so it can be used as a separation of alkali metals and alkaline earth metals.

Ion exchange is the effect or phenomenon of the exchange of ions in the solution with the ions on a certain ion exchanger, which is to exchange the ions in the solid ion exchanger with the ions in the dilute solution to achieve the purpose of extracting or removing some ions in the solution, which is a unit operation belonging to the mass transfer separation process.

Ion exchange is a reversible equivalent exchange reaction. Ion exchange resins are sandwiched between anion and cation exchange membranes to form a single processing unit and form a freshwater chamber. The reliability of ion exchange velocity decreases with the increase of resin crosslinking, and increases with the decrease of particles.

Ion exchange is a liquid-solid phase start-wheel reaction process, which inevitably involves the diffusion process of substances in the liquid residual phase and the solid phase.

After passing through the cation exchange resin, the ammonium thiocyanate solution can be used to wash the moldenum ( ) molybdenum ( ) molybdenum ( ) and rhenium hydroxide sodium solution chain closed through the anion exchange resin, and then 1mol l potassium oxalate solution can be used to wash molybdenum ( ) and then 7mol lhcl rhenium.

Take 4 100 ml centrifuge tubes and weigh them separately (to the nearest g, the same below). Two of them were added to the surface air-dried soil samples of the g-polluted irrigation area, and the remaining two were added to the deep air-dried soil samples of g and labeled. 20 ml of barium chloride solution was added to each tube of Tonggao, stirred with a glass rod for 4 min, and centrifuged at 3000r speed until the lower soil sample was compacted.

Discard the supernatant and add another 20 ml of barium chloride solution and repeat.

Add 20 ml of distilled water to each centrifuge tube, stir with a glass rod for 1 min, centrifuge to settle, and discard the supernatant. Weigh the centrifuge tube along with the weight of the soil sample. Pipette ml mol l sulfuric acid solution into each centrifuge tube, stir for 10 min, place for 20 min, centrifuge and settle, and pour the supernatant into 4 test tubes.

Pipette ml of the supernatant from each tube into four 100 ml Erlenmeyer flasks. In the meantime, pipette ml of mol l sulfuric acid solution into the other 2 Erlenmeyer flasks. In these 6 Erlenmeyer flasks, 10 ml of distilled water and 1 drop of phenolphthalein indicator were added to each of the 6 Erlenmeyer flasks, and the solution turned red and did not fade for several minutes.

A method that uses the difference in the exchange capacity of exchangeable groups in an ion exchanger and various ions in solution to separate them.