FR3137082A1 - METHOD FOR TREATMENT OF WASTEWATER CONTAINING MANGANESE - Google Patents

Abstract

METHOD FOR TREATING MANGANESE-CONTAINING WASTEWATER A process for treating manganese-containing wastewater is disclosed, which method comprises the steps of: adjusting the pH of manganese-containing wastewater to alkalinity with an alkaline solution to obtain a mixing, oxidizing the mixture in an air oxidation tower; and achieving solid-liquid separation; where the air oxidation tower has a height-diameter ratio ranging from 4 to 8, the air oxidation tower is provided with a packing, the packing has a density ranging from 0.9 to 1 .2 g/ml, and sterile solution wastewater includes soluble manganese, soluble nickel and soluble cobalt. The manganese-containing wastewater treatment method according to the present disclosure enables precious metals to be recycled without introducing other chemicals, and enables sterile solution wastewater to meet discharge standards. The process is simple and cost-effective, eliminates the introduction of other impurity ions and generates no waste or by-products, avoiding secondary pollution of the environment.

Description

METHOD FOR TREATMENT OF WASTEWATER CONTAINING MANGANESE DOMAIN

The present disclosure belongs to the field of wastewater treatment, and relates specifically to a process for treating wastewater containing manganese.

BACKGROUND

About 60% of continental nickel resources are in the form of lateritic nickel ore. With the increasing demand for nickel for stainless steel and renewable energy, lateritic nickel ore has gradually become the main supply form of nickel resources thanks to its relatively abundant reserves and low mining difficulty. The lateritic nickel ore smelting process includes pyrometallurgical process and hydrometallurgical process. Generally, the pyrometallurgical process is suitable for silicon-magnesium type nickel ore with relatively high nickel content, and the hydrometallurgical process is suitable for limonite type nickel ore with relatively low nickel content. Among hydrometallurgical processes, high pressure acid leaching (HPAL) gives higher nickel and cobalt recovery rate than ammonia leaching and atmospheric pressure acid leaching, and thus dominates the process development direction hydrometallurgical. However, high-pressure acid leaching (HPAL) is complicated, and the sterile solution wastewater produced from such a process also requires complicated treatment.

The process of producing nickel-cobalt hydroxide (MHP) through high-pressure acid leaching (HPAL) of lateritic nickel ore will generate sterile solution wastewater. Sterile solution wastewater is conventionally treated by processes including milk of lime precipitation process, microelectronic adsorption process and oxidation process with oxidants. Precipitation of milk of lime produces a large amount of calcium sulfate and manganese hydroxide mixture which is difficult to recycle. The oxidation process with oxidants and the microelectronic adsorption process introduce impurity ions, increasing the cost of water treatment, and the extraction using extractants causes secondary pollution.

Therefore, the development of a treatment process for manganese-containing wastewater without introducing other impurity ions is an urgent task at present.

SUMMARY

The present disclosure aims to resolve at least one of the technical problems of existing techniques. To this end, the present disclosure provides a method for treating manganese-containing wastewater, which can recover precious metals without introducing impurity ions, thereby reducing the cost of water treatment and achieving the standards of discharge of wastewater.

The present disclosure further provides the use of the process described above for treating manganese-containing wastewater in sterile solution wastewater from the high-pressure acid leaching of lateritic nickel ore to produce manganese hydroxide. nickel-cobalt.

According to the first aspect of the present disclosure, the process for treating wastewater containing manganese comprises the steps:

adjusting the pH of manganese-containing wastewater to alkalinity with an alkaline solution to obtain a mixture, oxidizing the mixture in an air oxidation tower; and carrying out a solid-liquid separation;

where the air oxidation tower has a height-diameter ratio ranging from 4 to 8,

the air oxidation tower is equipped with a lining,

the filling has a density ranging from 0.9 to 1.2 g/ml, and

Sterile solution wastewater includes soluble manganese, soluble nickel and soluble cobalt.

According to one embodiment of the present disclosure, the method of treating manganese-containing wastewater has at least the following beneficial effects.

1. The air oxidation tower of the present disclosure can replace an oxidizing additive for oxidation. The air oxidation tower can make full use of the oxygen in the air with height-diameter ratio ranging from 4 to 8; improves oxidation efficiency and reduces oxidation cost; allowing the recovery of metallic manganese and residual metallic nickel and cobalt without introducing any other impurity ions except an alkaline solution.

2. The packing loaded in the tower with a density close to that of water rolls with the fluctuation of water when flowing manganese-containing wastewater, which can greatly increase the contact area between the air and water, and can also avoid the failure of stirring the sediment in the packing, which would cause the sediment to gradually block the packing and further cause the failure of water flow to remove the tower sediments.

3. This disclosure maximizes the recycling of precious metals without introducing other chemicals, and allows sterile solution wastewater to reach discharge standards. The process is efficient, simple and cost-effective, eliminates the introduction of other impurity ions and generates no waste or by-products, thereby maximizing the recovery of precious metals and allowing wastewater to meet discharge standards at the same time. time, which helps avoid secondary pollution of the environment.

According to some embodiments of the present disclosure, the manganese-containing wastewater includes sterile solution wastewater from the high-pressure acid leaching of lateritic nickel ore to produce nickel-cobalt hydroxide.

According to certain embodiments of the present disclosure, the pH is between 8.5 and 9.

In the sterile solution with such pH, the elements including manganese, nickel and cobalt are precipitated into hydroxide, which is convenient for recovery and avoids the waste of alkaline solution.

According to some embodiments of the present disclosure, the alkaline solution comprises a sodium hydroxide solution.

According to some embodiments of the present disclosure, the volume ratio of the aeration rate of the air oxidation tower to the flow rate of the manganese-containing wastewater is 15 to 20:1.

Such aeration rate guarantees the occurrence of the oxidation reaction and avoids the reduction in reaction efficiency.

According to certain embodiments of the present disclosure, the oxidation is carried out for 30 to 60 min.

The condition described above allows for the oxidation of manganese ions to a manganese metahydroxide and precipitation of manganese dioxide.

According to certain embodiments of the present disclosure, the solid-liquid separation is carried out in a settling basin.

According to some embodiments of the present disclosure, the process includes recovering metals after solid-liquid separation.

According to some embodiments of the present disclosure, solid-liquid separation is achieved with a combination of a sedimentation tank, a sand filtration tank and a microporous filter.

According to some embodiments of the present disclosure, the microporous filter includes a filter element having a pore size ≤ 0.5 μm.

The fine filtration device consisting of the sand filtration basin and the microporous filter further separates the flocs that have not settled in the wastewater.

According to some embodiments of the present disclosure, the filtration further comprises backwashing the sand filtration basin and the microporous filter.

The sand filtration basin and microporous filter will have increased pressure after a period of filtration, and thus will require backwashing. The substances removed by backwashing are mainly precipitates containing metal salts, and the backwashing water is sent to a metal recovery system.

The mechanism of the manganese-containing wastewater treatment process provided by the present disclosure is as follows:

The sterile solution wastewater is adjusted with an alkaline solution to a pH in the range of 8.5 to 9, to allow elements such as nickel and cobalt in the sterile solution to precipitate into hydroxide.

The pH-adjusted wastewater is oxidized through an air oxidation tower.

After the wastewater is oxidized through the air oxidation tower, the manganese ions in the wastewater are precipitated into manganese metahydroxide and manganese dioxide. The oxidized wastewater is subjected to liquid-solid separation, with the precipitates pumped into the metal recovery system for recycling.

Mn ²⁺ +2OH ^- = Mn(OH) ₂ ↓

4Mn(OH) ₂ +O ₂ = 4MnO(OH)+2H ₂ O

The supernatant from the solid-liquid separation passes successively through the fine filtration device composed of the sand filtration basin and the microporous filter, to further separate the floccules that have not settled in the wastewater.

The sand filtration basin and microporous filter will have increased pressure after a period of filtration, and thus will require backwashing. The substances removed by backwashing are mainly precipitates containing metal salts, and the backwashing water is sent to a metal recovery system.

Sterile solution wastewater treated as above can be discharged according to standards.

The use of the manganese-containing wastewater treatment method according to one embodiment of the present disclosure, in sterile solution wastewater from the high-pressure acid leaching of lateritic nickel ore to produce manganese hydroxide nickel-cobalt, has at least the following beneficial effects.

The sterile solution from high pressure acid leaching (HPAL) of lateritic nickel ore for MHP production contains the elements at the levels shown in Table 1. Compositions and Contents of Sterile Solution Wastewater
from High Pressure Acid Leaching (HPAL)
of Lateritic Nickel Ore for MHP Production Compositions Neither Co Mn Zn N / A Mg SO ₄ ^2- SS COD PH Content,
mg/L 3-10 0.3-1.0 500-2000 <50 <20 <6 <50 <100 <50 8-9 Table 1 Element Content in the Sterile Solution

It can be seen from the table above that the element with the highest content in sterile solution wastewater is Mn.

The above and/or additional aspects and advantages of the present disclosure will become apparent and easily understood from the following description of the examples in conjunction with the accompanying drawings, in which:

is a flowchart showing a precious metal recovery process in Example 1 according to the present disclosure.

is a schematic drawing of the air oxidation tower in Example 1 of the present disclosure.

DETAILED DESCRIPTION

Below, the examples of the present disclosure will be described in detail. These examples are illustrated in the accompanying drawings where the same or similar reference numerals refer to the same or similar elements, or to elements having the same or similar functions. These examples with reference to the accompanying drawings are given by way of example and solely for the explanation of this disclosure, and should not be construed as a limitation of this disclosure.

Example 1

This example discloses a process for treating manganese-containing wastewater, which includes the following steps.

S1: 2000 mL of a crude solution (sterile solution wastewater), with an element Mn content of 1980 mg/L and a pH = 6.85, was adjusted with sodium hydroxide to a pH of 8.5, and oxidized through a 5 L air oxidation tower with a height-diameter ratio of 5 loaded with packing (PE packing), at an aeration rate of 15 to 20 times that of the water worn for an aeration time of 30 min.

S2: The raw solution wastewater oxidized in step S1 was subjected to sedimentation. Then, the supernatant was successively passed through a sand filtration basin and a microporous filter. As a result, the concentration of Mn in the solution decreased to 0.5 mg/L (the removal rate was 99.97%), which reached the wastewater discharge standards.

The precipitate was filtered and dried to obtain 6.1 g of dry slag, which can be used to recover metals such as Mn.

The flowchart showing the manganese-containing wastewater treatment process is shown in the .

The schematic drawing of the air oxidation tower is shown in the .

Example 2

This example discloses a process for treating manganese-containing wastewater that includes the same steps as Example 1, except that the packing in this example was volcanic gravel.

S1: 2000 mL of a crude solution (sterile solution wastewater), with an element Mn content of 1980 mg/L and a pH = 6.85, was adjusted with sodium hydroxide to a pH of 8.5, and oxidized through a 5 L air oxidation tower with a height-diameter ratio of 5 loaded with packing (volcanic gravel), at an aeration rate of 15 to 20 times that of the water worn for an aeration time of 30 min.

S2: The raw solution wastewater oxidized in step S1 was subjected to sedimentation. Then, the supernatant was successively passed through a sand filtration basin and a microporous filter. As a result, the concentration of Mn in the solution decreased to 0.51 mg/L (the removal rate was 99.97%), which reached the wastewater discharge standards.

The precipitate was filtered and dried to obtain 6.2 g of dry slag, which can be used to recover metals such as Mn.

Example 3

This example discloses a process for treating manganese-containing wastewater that includes the same steps as Example 1, except that the height-to-diameter ratio in this example was 8.

S1: 2000 mL of a crude solution (sterile solution wastewater), with an element Mn content of 1980 mg/L and a pH = 6.85, was adjusted with sodium hydroxide to a pH of 8.5, and oxidized through a 5 L air oxidation tower with a height-diameter ratio of 8 loaded with packing (PE packing), at an aeration rate of 15 to 20 times that of the water worn for an aeration time of 30 min.

S2: The raw solution wastewater oxidized in step S1 was subjected to sedimentation. Then, the supernatant was successively passed through a sand filtration basin and a microporous filter. As a result, the concentration of Mn in the solution decreased to 0.49 mg/L (the removal rate was 99.97%), which reached the wastewater discharge standards.

The precipitate was filtered and dried to obtain 6 g of dry slag, which can be used to recover metals such as Mn.

Example 4

This example discloses a process for treating manganese-containing wastewater that includes the same steps as Example 1, except that the height-to-diameter ratio of this example was 4.

S1: 2000 mL of a crude solution (sterile solution wastewater), with an element Mn content of 1980 mg/L and a pH = 6.85, was adjusted with sodium hydroxide to a pH of 8.5, and oxidized through a 5 L air oxidation tower with a height-diameter ratio of 4 loaded with packing (PE packing), at an aeration rate of 15 to 20 times that of the water worn for an aeration time of 30 min.

S2: The raw solution wastewater oxidized in step S1 was subjected to sedimentation. Then, the supernatant was successively passed through a sand filtration basin and a microporous filter. As a result, the concentration of Mn in the solution decreased to 0.51 mg/L (the removal rate was 99.97%), which reached the wastewater discharge standards.

The precipitate was filtered and dried to obtain 6 g of dry slag, which can be used to recover metals such as Mn.

Comparative example 1

This comparative example discloses a process for treating manganese-containing wastewater which differs from Example 1 by reducing the height-to-diameter ratio of the reaction tower (the height-to-diameter ratio was reduced from 5 to 1.5) . The process includes the following steps.

S1: 2000 mL of a crude solution (sterile solution wastewater), containing an element Mn at 1980 mg/L and with a pH = 6.85, was adjusted with sodium hydroxide to a pH of 8 .5, and oxidized through a 5 L air oxidation tower loaded with packing (PE packing), at an aeration rate of 15 to 20 times that of the wastewater for an aeration time of 30 min.

S2: The raw solution wastewater oxidized in step S1 was subjected to sedimentation. Then, the supernatant was successively passed through a sand filtration basin and a microporous filter. As a result, the concentration of Mn in the solution decreased to 311 mg/L (the removal rate was 85.33%), which did not meet the wastewater discharge standards.

Comparative example 2

This comparative example discloses a process for treating wastewater containing manganese which differs from Example 1 in that the packing was quartz sands. The process includes the following steps.

S1: 2000 mL of a crude solution, containing an element Mn at 1980 mg/L and with a pH = 6.85, was adjusted with sodium hydroxide to a pH of 8.5, and oxidized through a 5 L air oxidation tower with a height-diameter ratio of 5 loaded with packing (quartz sands), at an aeration rate of 15 to 20 times that of the wastewater for an aeration time of 30 min.

S2: The oxidized wastewater was subjected to sedimentation. Then, the supernatant was successively passed through a sand filtration basin and a microporous filter. As a result, the concentration of Mn in the solution was 2 mg/L.

The precipitate was filtered and dried to obtain 2.8 g of dry slag.

Compared to Example 1, Comparative Example 2 used quartz sands which were a heavier packing, resulting in a higher Mn removal rate, but the dry slag produced was 2.8 g which was much less than 6.1 g in Example 1, as most of the precipitate was left inside the air oxidation tower due to filtration by the quartz sands, which increased the risk of clogging of the air oxidation tower and was not conducive to Mn recovery.

Comparative example 3

This comparative example discloses a process for treating wastewater containing manganese which differs from example 1 by the absence of addition of packing. The process includes the following steps.

S1: 2000 mL of a crude solution, containing an element Mn at 1980 mg/L and with a pH = 6.85, were placed in a 5 L tank with a height-diameter ratio of 5, adjusted with l sodium hydroxide at a pH of 8.5, and oxidized at an aeration rate of 15 to 20 times that of the wastewater for an aeration time of 30 min.

S2: The oxidized wastewater was subjected to sedimentation. Then, the supernatant was successively passed through a sand filtration basin and a microporous filter. As a result, the concentration of Mn in the solution was 420 mg/L (the removal rate was 78.79%), which did not meet the wastewater discharge standards.

Compared to Example 1, the tank used in Comparative Example 3 was free of packing. Such direct aeration had poor effects, resulting in less amount of slag, and some metal was not oxidized into precipitates, so the wastewater did not meet the wastewater discharge standards.

Embodiments of the present disclosure have been described in detail above in conjunction with the drawings. However, the present disclosure is not limited to the aforementioned embodiments, and various modifications may be made without departing from the purpose of the present disclosure within the scope of knowledge possessed by those skilled in the art.

Claims (8)

Process for treating wastewater containing manganese, comprising:
adjusting the pH of manganese-containing wastewater to alkalinity with an alkaline solution to obtain a mixture, oxidizing the mixture in an air oxidation tower; and achieving solid-liquid separation;
in which the air oxidation tower has a height-diameter ratio ranging from 4 to 8,
the air oxidation tower is provided with a lining,
the filling has a density ranging from 0.9 to 1.2 g/ml, and
manganese-containing wastewater includes soluble manganese, soluble nickel and soluble cobalt. A method according to claim 1, wherein the manganese-containing wastewater comprises sterile solution wastewater from the high-pressure acid leaching of lateritic nickel ore to produce nickel-cobalt hydroxide. Process according to claim 1, in which the pH is between 8.5 and 9. A method according to claim 1, wherein the alkaline solution comprises a sodium hydroxide solution. A method according to claim 1, wherein a volume ratio of the aeration rate of the air oxidation tower to the flow rate of manganese-containing wastewater is 15 to 20:1. Process according to claim 1, in which the oxidation is carried out for 30 to 60 min. A method according to claim 1, wherein the solid-liquid separation is carried out with a combination of a sedimentation tank, a sand filtration tank and a microporous filter. A method according to claim 7, wherein the microporous filter comprises a filter element having a pore size ≤ 0.5 μm.