AU2020102183A4

AU2020102183A4 - Preparation of zeolite 4a from tailings and method for treatment of pb-containing wastewater

Info

Publication number: AU2020102183A4
Application number: AU2020102183A
Authority: AU
Inventors: Dandan CAO; Suqin LI; Guohong Xiong
Original assignee: University of Science and Technology Beijing USTB
Current assignee: University of Science and Technology Beijing USTB
Priority date: 2020-09-09
Filing date: 2020-09-09
Publication date: 2020-10-15
Anticipated expiration: 2028-09-09

Abstract

The invention belongs to the field of high value utilization of secondary resources, in particular to a method for preparing zeolite 4A from tailings and its application. The synthetic steps of zeolite 4A are as follows: high temperature alkali melting of sodium carbonate, aging with water, heating crystallization, washing and drying. When tailings are used as raw materials, Al (OH) 3 should be added before alkali melting at high temperature to form zeolite in the process of alkali melting to synthesize NaAlSiO4. The results showed that the optimum pH range was 4-8, the treatment time was within 10s, the treatment effect reached the national discharge standard, and the adsorption capacity was 150mg / G-200 mg/g. The zeolite can be reused after treatment. The overall recovery rate is more than 90%, in which the recovery rate of the first time is more than 92% and the second time is more than 93%. The beneficial effect of the invention is to use high silicon tailings to synthesize zeolite, which realizes high value utilization of tailings secondary resources. Comprehensive utilization of tailings not only solves environmental problems but also creates huge economic benefits from preparation of zeolite 4A. -1/5 Goldflotation gs Lead containing wastewater Ranlminlgrmding A1(OH)3,Na2CO3 Ion enge reacin High-temperature alkalimeltinn filter Essence I wastewater Water aging molecular siev Heating and crystallization Waing|and Molecularsieveaanasyhi dryingfilter zPeolite 4A molecular Filtering wastewaterNa Dry : Pb pre cipitat on reacti on Rccemolecular sieve and Filter and recover Pb S r1 eusye t recover bS Fig. 1

Description

-1/5

Goldflotation gs Lead containing wastewater

Ranlminlgrmding

A1(OH) 3,Na2 CO 3 Ion enge reacin

High-temperature alkalimeltinn filter Essence

Water aging I wastewater

molecular siev

Heating and crystallization

Waing|and Molecularsieveaanasyhi dryingfilter

zPeolite 4A

molecular Filtering wastewaterNa

on Pb pre cipitat on reacti Dry :

Rccemolecular sieve and Filter and recover Pb S

r1 eusye t

recover bS

Fig. 1

AUSTRALIA

PATENTS ACT 1990

PATENT SPECIFICATION FOR THE INVENTION ENTITLED:

PREPARATION OF ZEOLITE 4A FROM TAILINGS AND METHOD FOR

TREATMENT OF PB-CONTAINING WASTEWATER

The invention is described in the following statement:-

PREPARATION OF ZEOLITE 4A FROM TAILINGS AND METHOD

FOR TREATMENT OF PB-CONTAINING WASTEWATER TECHNICAL FIELD

[0001] The invention belongs to the field of high value utilization of secondary resources

and relates to a method for preparing zeolite 4A from tailings and its application.

BACKGROUND

[0002] Zeolite 4A is a kind of alkali metal aluminosilicate with cubic crystal structure. The

porous material with pore and cavity is formed by connecting silicon oxygen tetrahedron

and aluminum oxygen tetrahedron through oxygen bridge bond. The special framework

structure is often negatively charged, and metal cations are balanced charges, which are

distributed in the channels and cages of the framework structure and have greater mobility.

In the solution, cation exchange can be carried out to reduce the content of harmful heavy

metals in water. In the Pb smelting industry, a large number of Pb-containing wastewater

is produced. The Pb in wastewater is teratogenic, mutagenic and carcinogenic. The

treatment of Pb-containing wastewater by zeolite will be a new development direction.

[0003] The raw materials for synthesis of zeolite 4A are mostly chemical pure sodium

silicate and aluminum hydroxide, which are expensive. Most of the elements needed in the

synthesis of zeolite 4A are the components of tailings and lean ore, such as SiO2 and A1203,

which are the main raw materials for the synthesis of zeolites. At present, the reports on

the synthesis of zeolites using kaolin and fly ash have gradually come into people's view.

The output and accumulation of tailings in China is huge, which poses a serious threat to

the environment and safety. The effective utilization of tailings to synthesize zeolite will bring environmental and economic benefits. The synthetic zeolite was used to treat the wastewater that containing Pb.

SUMMARY

[0004] In order to solve the above problems, the object of the invention is to prepare zeolite

4A from tailings, which was used as adsorbent to treat Pb-containing wastewater and

recycle the treated zeolite. It is necessary to make full use of tailings resources, realize the

resource utilization of wastes, reduce production costs, and treat Pb-containing wastewater

with synthetic zeolites. The invention aims to prepare zeolite from tailings containing

silicon, treat wastewater containing Pb with synthetic zeolite, and recover zeolite, and

prepare zeolite 4A from tailings, as well as application and recovery process.

[0005] The technical scheme of the invention is: a method for preparing zeolite 4A from

tailings. In the method, the tailings are ground to below 325 mesh, and then mixed with a

certain amount of solid Na2CO3 and solid Al(OH)3, after high temperature alkali melting,

water aging, heating crystallization, washing and drying, zeolite 4A with cubic crystal

structure and uniform particle distribution is obtained.

[0006] The method includes the following steps:

[0007] Step 1: high temperature alkali melting: grind a certain number of tailings to below

325 mesh, mix with certain solid Na2CO3 and solid Al (OH) 3 , put it in a crucible, and then

heat it at high temperature for reaction. The heating temperature is 840-860°C, and the heat

preservation is 1.8-2.2h to obtain the ore sample for standby use;

[0008] Step 2: water aging: the ore sample obtained in step 1 is aged for 25-35min with

water, and the mass ratio of ore sample to water is 1:5-1:10;

[0009] Step 3: heating crystallization: the ore sample is placed in a reaction kettle, the

temperature is 100°C - 120°C, and the time is 3-5h;

[0010] Step 4: washing and drying: the ore sample after the above steps is washed and

filtered with water and dried at 45-60°C for 5h to obtain zeolite 4A with cubic crystal

structure and uniform particle distribution.

[0011] Furthermore, in the step 1, the mass ratio of sodium carbonate to silica in tailings is

1:0.8-1:1.2 and the molar ratio of silica and alumina in tailings is 1.5-2.5.

[0012] Furthermore, the tailings contain more than 50% SiO 2 , 5% - 20% A1203, Fe203 and

other minor impurities of K20, Cao, MgO, Ti, P, Zn and other trace elements.

[0013] Furthermore, the adsorption capacity of zeolite 4A with cubic crystal structure and

uniform particle distribution is 100 mg/g-200 mg/g.

[0014] Zeolite 4A prepared by the above method is applied in the treatment of Pb

containing wastewater. The optimum conditions for the treatment of Pb-containing

wastewater are pH 4.6, treatment time is within 10s, and the adsorption capacity is 150

200mg/g. The treatment process is as follows: 200ml of 100mg/L Pb-containing

wastewater is treated by 0.12g zeolite, and the concentration of Pb ion is determined after

lh. The concentration of Pb ion drops below 0.5mg/, meeting the national discharge

standard.

[0015] The recovery method of synthetic zeolite after treatment of Pb-containing

wastewater is as follows: the zeolite is analysed by saturated NaCl solution, and then

filtered and dried to recover the zeolite. The treated zeolite can be reused, with the

recovery rate of more than 92% for the first time, and 93% for the second and third times

(the overall recovery rate is more than 90%); the heavy metal Pb can be recovered by the reaction of saturated NAS solution and filtrate. The conditions of zeolite analysis were as follows: ig zeolite was separated by 500ml saturated NaCl solution at room temperature for 30min.

[0016] XRD, SEM and other characterization methods were used to characterize the

synthesized zeolites. The results show that the synthesized zeolites have good crystallinity

and the morphology is tetrahedral micron zeolite 4A. ICP was used to detect the Pb

containing wastewater, showing a good Pb ions removal effect. The synthetic zeolite has

strong ion exchange ability and good reuse rate.

[0017] The advantages of the present invention are as follows: (1) the main raw material for

the synthesis of zeolite is tailings with high silicon content, and the composition and content

of many tailings are similar to the tailings, so the synthetic zeolite realizes the purpose of

treating waste with waste; (2) the synthesized zeolite 4A has good ion exchange

performance, The results show that it has a good treatment effect on the wastewater

containing Pb, the Pb ion can be quickly removed within 10 seconds, which can meet the

requirements of the national discharge standard, and PBS can be recovered; (3) the zeolite

4A synthesized has good reuse effect and good reusability; (4) in the synthesis process,

Al(0H)3 is added before high temperature alkali fusion, NaAlSiO4, the raw material for the

synthesis of zeolite, can be produced in the alkali melting process, which is beneficial to

reduce the hydrolysis time and water consumption.

BRIEF DESCRIPTION OF THE FIGURES

[0018] Figure 1: Process chart for treatment and recovery of Pb-containing wastewater with zeolite

4A prepared from tailings.

[0019] Figure 2: XRD patterns of zeolite 4A prepared from tailings.

[0020] Figure 3: SEM image of zeolite 4A prepared from tailings.

[0021] Figure 4: Particle size analysis of zeolite 4A prepared from tailings.

[0022] Figure 5: Effect of reuse of synthetic zeolite.

DESCRIPTION OF THE INVENTION

[0023] In the following, the technical solution of the present invention is further described with

reference to specific embodiments.

[0024] Example 1:

[0025] The raw material is tailings, mainly containing SiO2 , A1203, a small amount of Fe, K, Ca,

Mg, Ti, P, Zn and other elements, and the main chemical components are as follows (% wt):

[0026]

SiO 2 A1 2 0 3 Fe 2O 3 K2 0 CaO MgO

71.38 12.80 3.96 3.44 2.78 2.66

[0027] Synthesis of zeolite 4A from tailings:

[0028] High-temperature alkali melting: Grind the tailings to 325 meshes, mix them with solid

Na2CO3 and solid Al (OH) 3, and place them in the crucible for high-temperature heating and

reaction. The heating temperature is 855°C and hold it for 2h. That mass ratio of sodium carbonate

to silicon dioxide is 1: 1.2, and the molar ratio of silicon dioxide to aluminum oxide is 2.

[0029] Water aging: The mineral samples after the above steps were aged by adding water and

stirring for 20h. The ratio of ore to water is 1: 8.

[0030] Heating and crystallization: The above-mentioned ore samples are placed in a reaction

kettle, heated and kept for a certain period of time. The temperature is 100°C and the time is 5h.

[0031] Washing and drying: The ore sample after the above steps was washed with water and

filtered and dried at 50°C for 5h.

[0032] The synthesized zeolite was examined by XRD, SEM and particle size analysis. XRD

results showed that it was zeolite 4A with high purity. SEM shows that the synthesized zeolite is

mainly cubic crystal structure, and the crystal effect and particle distribution are uniform. The

results of particle size test showed that the particle size of the synthesized zeolite was micron, and

the average particle size was 5[m.

[0033] The optimal conditions for the treatment of wastewater containing Pb by the zeolite

synthesized above are pH 4.6, treatment time within 1Os, and adsorption capacity of 150mg/g. The

treatment process is as follows: 0.12g zeolite is used to treat 200 ml of wastewater containing

100mg/L Pb, after lh, the concentration of Pb ion is measured, which is reduced to less than

0.5mg/L.

[0034] Resolve and recover the treated zeolite, the steps are as follows:

[0035] Take 0.24 g synthetic zeolite to treat 200mg/L Pb-containing wastewater with 200 ml, and

adsorb for 10min, measure the concentration of the solution. Filter the wastewater added with

zeolite, take appropriate amount of NaCl saturated solution, wash the zeolite and then filter and

wash it again, and dry it at 60°C for 5h.

[0036] After washing the saturated NaCl solution, the filtrate was added with sufficient NaS solids

to form a black precipitate, and the PbS solids were recovered by filtration.

[0037] The zeolite was treated with the same concentration and volume of divalent Pb, and the

concentration of the solution was measured after adsorption for 1h, which was repeated 4 times.

[0038] The washing solution was washed with NaS solution and filtered to recover PbS solids.

[0039] The content of Pb ions in the solution was determined by ICP, and the results showed that

the first zeolite reuse effect was 91.2%, the second zeolite recycle effect was 99.9% of the first

one, the third time was 93.8% of the second time, showing a good effect of reuse.

[0040] Example 2:

[0041] The raw material is tailings, mainly containing SiO2 and A1203, and a small amount of Fe,

K, Ca, Mg, Ti, P, Zn and other elements, and the main chemical components are as follows (%

wt):

[0042]

SiO 2 A1 2 0 3 Fe2 0 3 K2 0 CaO MgO

70.48 13.02 2.98 3.78 2.97 2.45

[0043] Synthesis of zeolite 4A from tailings:

[0044] High-temperature alkali melting: Grind the tailings to 325 meshes, mix them with solid

Na2CO3 and solid Al (OH)3, and place them in the crucible for high-temperature heating and

reaction. Heating with heat temperature 855°C and holding for 2h. The mass ratio of sodium

carbonate to silicon dioxide is 1: 1.2, and molar ratio of silicon dioxide to aluminum oxide is 2.

[0045] Water aging: The mineral samples after the above steps were aged by adding water and

stirring for 20h. The ratio of ore to water is 1: 8.

[0046] Heated crystallization: The above-mentioned samples were placed in a reaction kettle,

heated and kept warm for a certain period of time. The temperature is 100°C and the time is 5h.

[0047] Washing and drying: The ore sample after the above steps was washed with water,

filtered, and dried at 50°C for 5h.

[0048] The synthesized zeolite was examined by XRD, SEM and particle size analysis. XRD

results showed that it was zeolite 4A with high purity. SEM shows that the synthesized zeolite

is mainly cubic crystal structure, and the crystal effect and particle distribution are uniform. The

results of particle size test showed that the particle size of the synthesized zeolite was micron,

and the average particle size was 5[m.

[0049] The optimal conditions for the treatment of Pb-containing wastewater by the zeolite

synthesized above are pH 4.6, treatment time within 1Os, and adsorption capacity of 200mg / g.

The treatment process is as follows: 0.12g zeolite is used to treat 200ml of wastewater

containing 100mg/L Pb, after 1h, the concentration of Pb ion is measured, which is reduced to

less than 0.5mg / L.

[0050] Resolve and recover the treated zeolite, the steps are as follows:

[0051] Take 0.24g of synthetic zeolite to treat 200mg/L Pb-containing wastewater with 200ml,

and adsorb for 10min, measure the solution concentration. Filter the wastewater added with

wash it, and dry it at 60°C for 5h.

[0052] After washing with saturated NaCl solution, the filtrate was added with sufficient NaS

solids to form a black precipitate, and the PbS solids were recovered by filtration.

[0053] After treating the zeolite with the same concentration and volume of divalent Pb, and

adsorbing for 1h, measure the concentration of the solution, and repeat 4 times in total.

[0054] The washing solution was washed with NaS solution and filtered to recover PbS solids.

[0055] The content of Pb ions in the solution was determined by ICP, and the results showed

that the reuse effect of the first zeolite was 72.8% of the original one, and that of the second

one was 99.9%. The third time was 93.6% of the second time, showing a good effect of reuse.

[0056] Example 3:

[0057] The raw material is tailings, mainly containing SiO2 and A1203, and a small amount of

Fe, K, Ca, Mg, Ti, P, Zn and other elements, and the main chemical components are as follows

(% wt):

[0058]

SiO 2 A1 2 0 3 Fe 20 3 K 20 CaO MgO

71.56 13.20 3.86 3.22 2.17 2.05

[0059] Synthesis of zeolite 4A from tailings:

[0060] High-temperature alkali melting: Grind the tailings to 325 meshes, mix them with solid

reaction. Heating in temperature 855°C, and holding for 2h, and that mass ratio of sodium

carbonate to silicon dioxide is 1: 1.2, and the molar ratio of silicon dioxide to aluminum oxide

is 2.

[0061] Water aging: The mineral samples after the above steps were aged by adding water and

stirring for 20h. The ratio of ore to water is 1: 8.

[0062] Heating and crystallization: The above-mentioned ore samples are placed in a reaction

kettle, heated and kept for a certain period of time. The temperature is 100°C and the time is

h.

[0063] Washing and drying: The ore sample after the above steps was washed with water,

filtered, and dried at 50°C for 5h.

[0064] The synthesized zeolite was characterized by XRD, SEM and particle size analysis.

XRD results showed that the zeolite was zeolite 4A with high purity. SEM shows that the

synthesized zeolite is mainly cubic crystal structure, and the crystal effect and particle distribution are uniform. The results of particle size test showed that the particle size of the synthesized zeolite was micron, and the average particle size was 5[m.

[0065] The optimal conditions for the treatment of Pb-containing wastewater by the zeolite

synthesized above are pH 4.6, treatment time within 10s, and adsorption capacity of 198 mg/g.

The treatment process is as follows: 0.12g zeolite is used to treat 200 ml of wastewater

containing Pb (100mg/L), after lh, the concentration of Pb ion is measured, which is reduced

to less than 0.5mg/L that meets the national emission standards.

[0066] Resolve and recover the treated zeolite, the steps are as follows:

[0067] Take 0.24g of synthetic zeolite, treat 200mg/L Pb-containing wastewater with 200 ml,

adsorb for 10 min, and measure the solution concentration. Filter the wastewater added with

wash it again, and dry it at 60°C for 5h.

[0068] After washing with saturated NaCl solution, the filtrate was added with sufficient NaS

[0069] The analysed zeolite was treated with the same concentration and volume of divalent

Pb, and the concentration of the solution was measured after adsorption for lh, which was

repeated 4 times.

[0070] The washing solution was washed with NaS solution and filtered to recover PbS solids.

[0071] The content of Pb ions in the solution was determined by ICP, and the results showed

that the reuse effect of the first zeolite was 93.2%, the second one was 99.9%, the third one was

92.9% of the second one, which showing a good effect of reuse.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A method for preparing zeolite 4A from tailings is characterized in that the method grinds silicon

containing tailings (containing more than 60% SiO 2) to below 325 mesh, and then mixes them with

a certain amount of solid Na2CO3 and solid A(OH)3, After high-temperature alkali fusion-water

aging-heating crystallization-washing and drying, a zeolite 4A with a cubic crystal structure and

uniform particle distribution is obtained.

2.The method according to claim 1 is characterized in that the method specifically comprises the

following steps:

Step 1. High temperature alkali fusion: grind a certain number of tailings to below 325 mesh, mix

with certain solidNa2CO3 and solid Al(OH)3, put it in a crucible, and then heat it at high temperature

for reaction. The heating temperature is 840-860 °C, and the heat preservation is 1.8-2.2 h. the ore

sample is obtained for standby use.

Step 2: Adding water and aging: the ore sample obtained in step 1 is aged by adding water and

stirring for 25-35 min, and the ore sample is separated; the mass ratio of ore sample to water is 1:5

1:10;

Step 3: Heat and crystallizing: put that ore sample treat in the step 2 into a reaction kettle at a

temperature of 100-120 DEG C for 3-5h;

Step 4: Washing and drying: the mineral samples treated in step 3 were washed andfiltered with

water and dried at 45-60 °C for 5h to obtain zeolite 4A with cubic crystal structure and uniform

particle distribution.

3. The method according to claim 1 is characterized in that the mass ratio of sodium carbonate to silica

in tailings is 1:0.8-1:1.2, and the molar ratio of silica and alumina in tailings is 1.5-2.5.

4. The method according to claim 1 is characterized in that the content of SiO 2 and A1203 in the tailings is more than 60% and 5% - 20%, respectively.

5. The method according to claim 1 is characterized in that the prepared zeolite 4A has cubic crystal

structure, uniform particle distribution, and adsorption capacity of100mg/g-200mg/g.

6. The application of zeolite 4A according to any one of claims 1-5 is characterized in that the zeolite

4A is applied in the treatment of Pb-containing wastewater, and the treatment effect meets the

requirements of national emission standard.

7. A recovery method for treating Pd-containing wastewater by zeolite 4A according to any one of

claims 1-5 is characterized in that it specifically comprises the following steps: using saturated NaCl

solution to analyse zeolite 4A, then filtering and drying to recover zeolite 4A. After treatment, the

zeolite can be reused that the recovery rate ofmore than 92% for the first time, and 93% for the second

and third times The results show that the total recovery is more than 90%; the heavy metal Pb (PBS)

is recovered by the reaction of saturated sodium sulphide solution and filtrate; the analytical

conditions are as follows: 1g of zeolite 4A is resolved with 500ml saturated NaCl solution at room

temperature, and the analysis time is 30 min.

-1/5-

Fig. 1

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Fig. 2

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Fig. 3

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Fig. 4

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Fig. 5