# US 11,028,000 B2 · Method for preparing eridite rod-shaped particles for water treatment by utilizing wastewater

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- Number: US 11,028,000 B2
- Document ID: US11028000B2
- Status: Granted
- Kind: B2
- Application number: 16/392,269
- Filed: 2019-04-23
- Published: 2020-05-07
- Granted: 2021-06-08
- Earliest claimed: 2018-11-07
- Assignees: Northeast Normal University
- Applicants: Northeast Normal University
- Inventors: Suiyi Zhu; Ge Dong; Mingxin Huo; Zhan Qu; Dejun Bian
- Web page: https://patentgrep.com/patent/US11028000B2

## CPC

- C02F 9/00: Multistage treatment of water, waste water or sewage
- C02F 11/127: by centrifugation
- C02F 1/281: {using inorganic sorbents}
- C02F 1/722: {Oxidation by peroxides}
- C02F 1/725: {by catalytic oxidation}
- C02F 11/143: using inorganic substances (C02F11/148 takes precedence)
- C02F 1/5245: {using basic salts, e.g. of aluminium and iron}
- C02F 11/13: by heating
- C02F 2101/30: Organic compounds
- C02F 2103/10: from quarries or from mining activities
- C02F 2305/026: Fenton's reagent
- C02F: TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE (separation in general B01D; special arrangements on waterborne vessels of installations for treating water, waste water or sewage, e.g. for producing fresh water, B63J; adding materials to water to prevent corrosion C23F; treating radioactively-contaminated liquids G21F9/04; regeneration of reactants for recirculation into processes, see the relevant places for the processes)

## Abstract

The present invention discloses a method for preparing Erdite rod-shaped particles for water treatment by utilizing iron-containing waste mud in an underground water plant. In the method, aqueous iron mud is subjected to mechanical dehydration to obtain a first aqueous iron mud; sodium sulfide is added to the first aqueous iron mud to obtain a first mixture, wherein the ratio of the weight of the first aqueous iron mud to the volume of sodium sulfide is between 3% and 15%; water of an equal volume is added to the first mixture, and the obtained solution is heated in an airtight manner to 140° C.-270° C.; centrifugal treatment is performed to obtain a supernatant and a solid, and the solid is subjected to vacuum drying at 40° C.-60° C. for 24 h to obtain Erdite rod-shaped particles. In the method, aqueous iron mud formed after precipitation of backwash wastewater is directly used, no drying treatment is needed, and silicon and aluminum and other impurities do not need to be removed, thereby saving costs; Na2S is directly added to iron mud which is subjected to mechanical dehydration, and adjustment of pH value is not needed, therefore, the preparation method is convenient; and a supernatant can be recycled, thereby lowering preparation cost, and expanding an application range of the method.

## Claims

### Claim 1

A method for preparing Erdite rod-shaped particles for water treatment by utilizing iron-containing waste mud in an underground water plant, said method comprising the following steps:
A. performing mechanical dehydration on aqueous iron mud, controlling a moisture content of the aqueous iron mud to be between 20% and 50%, to obtain a first aqueous iron mud;
B. adding sodium sulfide to the first aqueous iron mud to obtain a first mixture, wherein a weight of the first aqueous iron mud to a volume of sodium sulfide is between 3% and 15%;
C. adding to the first mixture a volume of water equal to a volume of the first mixture, airtight heating the first mixture with the added water at a constant temperature of 140° C.-270° C. for 0.5 hr to 4 hr; and
D. centrifuging the solution from step C to obtain a supernatant and a solid, and vacuum drying the solid at 40° C.-60° C. for 24 hr to obtain Erdite rod-shaped particles, wherein the Erdite is NaFeS2.2H2O; and recycling the supernatant for standby applications.

### Claim 2 (depends on 1)

The method of claim 1, further comprising a step E: mixing the supernatant with corresponding sodium sulfide to obtain a mixed liquor, wherein the weight of the supernatant to the volume of the sodium sulfide is between 0.8% and 9.5%; mixing a same volume of the mixed liquor with a same volume of the first aqueous iron mud obtained in step A, and then proceeding according to step D; circularly proceeding until a Mn content in the supernatant is lower than 0.5 mg/L.

### Claim 3 (depends on 2)

The method of claim 2, wherein when the Mn content in underground water treated by the underground water plant is lower than 0.5 mg/L, adding Mn at a concentration of 0.5%-5% to the first aqueous iron mud obtained in step A, stirring uniformly after Mn is added, and then performing step C.

### Claim 4 (depends on 1)

The method of claim 1, wherein step A further specifically comprises: aqueous iron mud is aqueous iron mud which is generated after direct precipitation of backwash wastewater in the underground water plant, or is aqueous iron mud which is generated after precipitation of the backwash wastewater in the underground water plant in which a coagulant is added.

### Claim 5 (depends on 4)

The method of claim 4, wherein the coagulant is inorganic coagulant containing iron, manganese, silicon and aluminium; and the dose of the coagulant added to the backwash wastewater should not exceed a concentration of 5 mg/L.

### Claim 6 (depends on 1)

The method of claim 1, comprising: adding Erdite rod-shaped particles obtained in step D to wastewater containing tetracycline hydrochloride, adjusting pH to be less than 6, stirring for 1 hr, letting stand until particles are separated from water to remove tetracycline hydrochloride in water.

### Claim 7 (depends on 1)

The method of claim 1, comprising: adding Erdite rod-shaped particles obtained in step D to organic wastewater, and adding persulphate, wherein a pH value of the wastewater need not to be adjusted, stirring for 10 min, and letting stand for 30 min to rapidly remove organic matter in water.