The physical and chemical properties and preparation methods of zeolite (2)

(1) Activation treatment

The activation methods of zeolite generally include high temperature incineration and inorganic acid treatment
.

After the natural zeolite is dried, it is roasted at a high temperature.

(2) Surface modification

Covering the surface of the zeolite with a porous modifier with high isoelectric point can enable the modified zeolite to obtain new functions while maintaining the original advantages
.

The Na-type zeolite prepared by modifying natural clinoptilolite with NaCl solution has a good removal effect on phenol in water

①P-type zeolite P-type zeolite can be formed by treating natural zeolite with NaOH solution.
For example, add 3910-200 mesh natural clinoptilolite into 10mL 5mol/L NaOH solution and heat it at (95±5)℃ for 70h to obtain P-type zeolite
.

② When Cu ²⁺ exchange is used to prepare copper zeolite from Cu type zeolite, the Cu2+ exchange is often hindered due to the H+ contained in the zeolite
.

Because the zeolite needs to be immersed in concentrated ammonia water before the exchange, NH ₄ ⁺ first replaces the H ⁺ in the zeolite

③H-type zeolite treat natural mordenite with dilute mineral acid (HCl, H ₂ SO ₄ , HNO ₃ , HClO ₄ ) to make the H ⁺ exchange rate at least 20% or more.
After molding, dry it at 90～110℃, and finally use 350 ～600℃ temperature heating activation Serve
.

H-type zeolite has high adsorption speed and cation exchange capacity

④Na-type zeolite: Treat natural mordenite with excess sodium salt solution (NaCl, Na ₂ SO ₄ , NaNO _3, etc.
) to make the Na ⁺ exchange rate at least 75%.
After molding, dry at 90～110℃, and finally at 350 It is made by heating and activating at a temperature of ~600℃
.

The Na-type zeolite will greatly increase its gas adsorption capacity, even larger than the adsorption capacity of the synthesized 5A molecular sieve

⑤NH ₄ ⁺ type zeolite Treat natural zeolite with 2mol/L NH ₄ C1 solution, and then use 2mol/L KCI solution as stripping agent, which can make the cation exchange capacity reach 145mmol/100g
.

⑥Ca-type zeolite: Treat natural zeolite with 2mol/L CaCl ₂ solution, and then use 2mol/L NH ₄ Cl solution as stripping agent, and its cation exchange capacity can reach 59mmol/100g
.

⑦Faujasite zeolite At present, most of the proven zeolite mines in China are clinoptilolite, and its fatal weakness is its small specific surface area and small pore size
.

If the clinoptilolite is transformed into faujasite zeolite, it can be widely used in chemical industry, oil refining and other fields, greatly improving the use value of this rich and cheap mineral

⑧Organized zeolite In recent years, the research on the organic modification of zeolite has been on the rise
.

It has been reported that using cetyltrimethylamine bromide as a modifier, the obtained modified clinoptilolite has a removal rate of up to 90% for 2,4-DCP

It should be pointed out that when zeolite is processed, the control of temperature and pH is very important, and they will directly affect its ion exchange capacity
.

Experiments show that the ion exchange capacity of zeolite changes slightly below 600°C, drops sharply above 600°C, and basically loses its exchange performance above 900°C

Related links: physicochemical properties and preparation methods of zeolite (1)