Removing Silicon from Aqueous Streams in Mineral Processing Facilities

Abstract

The present invention provides a method for removing soluble and / or colloidal silicon compounds from an aqueous stream (100, 200a, 300a, 400b) of a mineral processing facility. The method comprises: adding a coagulant and / or a flocculant and / or a flotation chemical to the aqueous stream (100, 200a, 300a, 400b) to promote the formation of flocs containing at least some silicon compounds and forming a treated aqueous stream (101, 201, 301, 401); subjecting the treated aqueous stream (101, 201, 301, 401) to clean flotation to separate at least some silicon compounds as a clean flotation overflow (103, 203, 303, 403); and removing the clean flotation overflow (103, 203, 303, 403). The clean flotation comprises bubbles, at least 90% of which have a diameter of 0.2 to 250 μm.

Description

Technical Field

[0001] The present application relates to a method and apparatus for removing Si from an aqueous stream of a mineral processing facility. In particular, the present application relates to a method and apparatus for removing soluble and / or colloidal silicon compounds from an aqueous stream of a mineral processing facility. Background Art

[0002] During the different stages of mineral processing, the pH of the slurry tends to decrease due to the oxidation of sulfide minerals and the lack of carbonate minerals to effectively buffer the pH. During tailings processing, the sulfur oxidation and the accompanying pH drop also continue, resulting in the accumulation of dissolved ions (such as SO 4 , Mg, Fe, Ni, Ca, K, Na) concentrations increase. In addition, Si and Al are released into the liquid phase as (alumino) silicate minerals dissolve under low pH conditions.

[0003] Water from tailings disposal operations and other feed water streams (e.g. water from waste rock areas or open pit mines) may contain high concentrations of dissolved species such as silica and metals. When different water streams mix and enter the flotation process with high pH values, the solubility of various compounds changes. Therefore, depending on the incoming concentration of dissolved silica and the pH profile of the process, dissolved silicates may begin to aggregate and form gels and colloids either by polymerization or by reaction with different metal ions or solid surfaces.

[0004] Gels and colloids formed by silicates can cause various problems that may ultimately lead to the loss of valuable metals and reduced recovery and quality of the final product.

[0005] Therefore, there is a need to find a solution for removing silicon compounds from aqueous streams of mineral processing plants. In particular, there is a need for a solution that removes soluble and / or colloidal silicon compounds from aqueous streams of mineral processing plants, thereby preventing the formation of silicate-containing gels and colloids, and the problems caused by them. Summary of the invention

[0006] The object of the present application is to provide a method and apparatus for removing soluble and / or colloidal silicon compounds from an aqueous stream of a mineral processing plant, thereby improving the recovery rate and quality of the recovered product and thus improving the performance of the entire plant.

[0007] According to one embodiment, a method for removing soluble and / or colloidal silicon compounds from an aqueous stream of a mineral processing facility is provided. The method comprises: adding a coagulant and / or a flocculant and / or a flotation chemical to the aqueous stream to promote the formation of flocs containing at least some silicon compounds and forming a treated aqueous stream; subjecting the treated aqueous stream to clean flotation to separate at least some of the silicon compounds as a clean flotation overflow; and removing the clean flotation overflow. The clean flotation contains bubbles, at least 90% of which have a diameter of 0.2 to 250 μm.

[0008] According to one embodiment, there is provided an apparatus for removing soluble and / or colloidal silicon compounds from an aqueous stream of a mineral processing facility. The apparatus comprises: a mixing system arranged to provide a coagulant and / or a flocculant and / or a flotation chemical to the aqueous stream; and a clean flotation cell arranged to separate at least some of the silicon compounds from the aqueous stream as a clean flotation overflow and to form residual process water as a clean flotation underflow.

[0009] BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 illustrates a schematic process flow diagram according to one embodiment,

[0011] Figure 2 illustrates a schematic process flow diagram according to one embodiment,

[0012] Figure 3 illustrates a schematic process flow diagram according to one embodiment, and

[0013] Figure 4 A schematic process flow diagram according to one embodiment is illustrated.

[0014] The drawings are schematic and are not to any particular scale. DETAILED DESCRIPTION

[0015] The above solution is described in more detail below in conjunction with some implementation schemes, but it should not be considered as limiting.

[0016] In this specification and claims, the term "comprising" may be used as an open term, but it also includes the closed term "consisting of."

[0017] The following reference numerals are used in this application:

[0018] 100 Water Flow

[0019] 101 Treated Aqueous Stream

[0020] 102 Cleaning flotation cells

[0021] 103 Clean flotation overflow

[0022] 104 Clean flotation underflow

[0023] 105 Dehydration equipment

[0024] 200a Watery flow

[0025] 201 Treated aqueous stream

[0026] 202 Cleaning flotation cells

[0027] 203 Clean flotation overflow

[0028] 204 Clean flotation underflow

[0029] 205a Tailings Thickener

[0030] 211 Mineral flotation circuit

[0031] 212 Slurry

[0032] 213 Underflow of mineral flotation circuit

[0033] 214 Overflow of mineral flotation circuit

[0034] 215 Tailings Thickener Underflow

[0035] 216 Flotation Device

[0036] 300a Watery flow

[0037] 301 Treated Aqueous Stream

[0038] 302 Cleaning flotation cells

[0039] 303 Clean Flotation Overflow

[0040] 304 Clean flotation underflow

[0041] 305a Tailings Thickener

[0042] 311a First mineral flotation circuit

[0043] 311b Second mineral flotation circuit

[0044] 312 Slurry

[0045] 313a Underflow of the first mineral flotation circuit

[0046] 313b Underflow of the Second Mineral Flotation Circuit

[0047] 314a Overflow of the first mineral flotation circuit

[0048] 314b Overflow of the Second Mineral Flotation Circuit

[0049] 315 Tailings Thickener Underflow

[0050] 316 Flotation Device

[0051] 400b Watery Stream

[0052] 401 Treated Aqueous Stream

[0053] 402 Cleaning flotation cells

[0054] 403 Clean Flotation Overflow

[0055] 404 Clean Flotation Underflow

[0056] 405b Concentrate Thickener

[0057] 411 Mineral Flotation Circuit

[0058] 412 Slurry

[0059] 413 Underflow of mineral flotation circuit

[0060] 414 Overflow of mineral flotation circuit

[0061] 416 Flotation Device

[0062] 425 Concentrate Thickener Underflow

[0063] In the mining industry, mineral processing refers to the process of improving the economic value of an ore by removing gangue minerals, which produces a higher grade product (concentrate) and a waste stream, i.e., tailings. Examples of mineral processing include, for example, froth flotation and gravity separation. The term "gangue" refers to material of no commercial value that surrounds or is intimately mixed with the desired mineral in a ore deposit.

[0064] Ore beneficiation by froth flotation is commonly used for the recovery and upgrading of sulfide ores. Froth flotation is a process that separates the valuable minerals from the gangue by exploiting the difference in hydrophobicity between the two. The difference in hydrophobicity between the valuable minerals and the gangue is increased by the use of surfactants and wetting agents. The flotation process is used to separate a wide range of sulfides, carbonates and oxides prior to further refining.

[0065] For froth flotation, ground ore is mixed with water to form a slurry, and the desired mineral is made hydrophobic by adding surfactant or collector chemicals. The specific chemicals depend on the nature of the mineral to be recovered and often on the nature of the undesirable mineral. The slurry containing the hydrophobic and hydrophilic particles is introduced into a tank called a flotation cell, which is aerated to produce bubbles. The hydrophobic particles attach to the bubbles, which rise to the surface, forming froth. The froth is removed from the tank to produce a concentrate of the target mineral. Froth flotation is usually carried out in several stages to maximize the recovery of the target mineral and the concentration of these minerals in the concentrate.

[0066] The amount of gangue in the ore is increasing. Among the gangue minerals, the amount of silicon-containing minerals is increasing. Most of these silicon-containing minerals can be found in the form of feldspar (KAlSi 3 O 8 –NaAlSi 3 O 8 –CaAl 2 Si 2 O 8 ) and quartz (SiO 4 / SiO 2 ), which are two of the most abundant minerals in the Earth's continental crust. The framework of these minerals mainly consists of a continuous framework of silicon-oxygen tetrahedrons, and the structure usually contains iron, aluminum, manganese or magnesium as impurities. Due to the impurities, the structure, which is otherwise very rigid, may be easily affected by external conditions, such as changes in pH. As a result, the structure may break up into smaller parts. When this happens in the process, the silicates may become dissolved or become colloidal. If the pH increases, the silicon-containing particles may react with different compounds, forming new structures. As the silicates rebuild their structure, this may lead to the formation of, for example, banded structures. These structures may cause an increase in viscosity, which can lead to problems in mineral processing / concentration.

[0067] Typically, the gangue removed during the beneficiation process is sent to a tailings dam where it is expected to have a long residence time, typically 20-40 days, to settle and separate the solids and break down the residual flotation chemicals from the collected reusable process water. The collected process water can then be recycled back to the beneficiation process. The quality of the recycled process water plays an important role in achieving the target recovery and quality of the final product.

[0068] Currently, water shortages, ecological requirements imposed by legislation and public pressure, costs and large space requirements of conventional tailings methods for process water treatment are exerting increasing pressure on the recycling of process water, since the main processes in mineral processing become at least partially closed-loop systems in terms of water use. In closed-loop systems, process water sometimes becomes supersaturated with silicates. It has been shown that the main part of the total silicon is present in colloidal form, rather than in the form of soluble compounds.

[0069] As mentioned above, gels and colloids formed by silicates can cause various problems that can ultimately lead to the loss of valuable metals and reduced recovery and quality of the final product. For example, problems can occur by adsorbing the colloids to the mineral surface, thereby preventing the collector from adsorbing on the mineral surface. Adsorption of collectors into colloids prevents the collector from adsorbing on the mineral surface (which is essential to promote flotation), resulting in decreased flotation kinetics. In addition, valuable metals may be trapped in the gel matrix, resulting in reduced metal recovery. In addition, gels and colloids can cause thickening problems (unsettled colloids that are recycled back into the flotation process) or even concentrate filtration problems (higher cake moisture due to aqueous gels). It is well known that silicates form a hydrophilic layer on the surface of valuable minerals, making them less floatable.

[0070] In addition, Si in aqueous solution tends to form complexes with Fe. The complexes formed may be fine colloidal particles. Fine colloidal particles containing Si and Fe may result in excessive fine powder loading, which may have a negative impact on froth flotation. Si and Fe together may form a coating / layer on the surface of the ore, thereby changing the flotation properties of the ore and ultimately leading to reduced ore recovery. Complexes containing Si and Fe may cause changes in the redox properties of the ore, thereby changing the foaming properties of the ore. For example, pentlandite (an iron-nickel sulfide) may be oxidized by the influence of complexes containing Si and Fe. The foaming properties of oxidized pentlandite are different from those of unoxidized pentlandite, which may have a negative impact on ore recovery.

[0071] Fe itself can particularly affect the recovery of Ni by flotation. Excessive iron contained in process water can lead to the formation of iron hydroxide-based coatings on the pentlandite used for nickel recovery, resulting in reduced nickel recovery.

[0072] The amount of soluble and / or colloidal silicon compounds in mineral processing water may exceed 100 ppm, and is often even as high as 300-400 ppm. Soluble silicon compounds may also be referred to as dissolved silicon compounds. In general, the presence of soluble and / or colloidal silicon compounds in aqueous streams of mineral processing facilities has not previously been found. For water analysis, it is common practice to filter the water sample before performing an elemental analysis. A typical filter with a pore size of 0.45 μm filters the colloidal silicon compounds out of the sample. Furthermore, the disadvantages of soluble and / or colloidal silicon for mineral processing discussed above were not understood.

[0073] The present description aims to provide a method and apparatus for removing soluble and / or colloidal silicon compounds from aqueous streams of mineral processing equipment, thereby preventing the formation of gels and colloids containing silicon compounds, and the problems caused by them. In addition, since aqueous streams typically contain Fe complexed with Si, the method also provides a way to remove at least some of the iron contained in aqueous streams of mineral processing equipment.

[0074] In the context of this specification, silicon compounds refer to compounds containing silicon and occurring in materials associated with mineral processing. Silicon compounds include silicates. The term silicate may refer to any member of the family of anions consisting of silicon and oxygen, any salt of such anions or any ester of such anions. The term silicate also includes compounds containing SiO 4 Those anions that form a continuous framework of tetrahedra with a metal (usually Fe, Al, Mn or Mg) as an impurity in the structure. The term silicate also includes silicate minerals and rock types that predominantly contain such minerals. Quartz (SiO 2 ) may also be included in silicates. Silicates also include minerals in which aluminum or other tetravalent atoms replace some of the silicon atoms, such as aluminosilicates.

[0075] In the context of this specification, a colloidal suspension or colloid is a mixture in which a substance in the form of microscopically dispersed insoluble or soluble particles is suspended throughout another substance. To qualify as a colloid, the insoluble or soluble particles do not settle, or require a long time to settle significantly. Thus, the term colloidal silicon compound herein refers to a silicon-containing compound suspended in water to form a mixture in which the insoluble or soluble particles do not settle, or require a long time to settle.

[0076] In the context of the present specification, "removal" or "removing" of soluble and / or colloidal silicon compounds may refer to a process of complete removal of said compounds or to a process in which the amount of said compounds is reduced, i.e. the amount of silicon compounds in the aqueous stream to be treated is higher than the amount of said compounds in the stream obtained after carrying out the process disclosed herein.

[0077] In accordance with one embodiment and as Figure 1 In the method shown, coagulants and / or flocculants and / or flotation chemicals are added to an aqueous stream 100 of a mineral processing facility. As a result, colloidal particles and suspended solids become unstable and combine into even larger aggregates that can be separated from the aqueous solution. A treated aqueous stream 101 is formed.

[0078] The treated aqueous stream 101 is subjected to clean flotation in a clean flotation unit 102. The clean flotation comprises gas bubbles, wherein at least 90% of the gas bubbles have a diameter of 0.2 to 250 μm. At least some of the soluble and / or colloidal silicon compounds are arranged to be separated as a clean flotation overflow 103. The clean flotation underflow 104 comprises residual process water. The clean flotation overflow 103 comprising at least some of the soluble and / or colloidal silicon compounds can be removed as tailings. The clean flotation underflow 104 can be recycled back into the process for use as process water.

[0079] The aqueous stream from which soluble and / or colloidal silicon compounds are to be removed may include water from a dewatering device 105. The dewatering device 105 may include a settling device or a filter. The settling device may be, for example, a thickener or a clarifier. The aqueous stream 100 to be treated may include at least a portion of a stream obtained from the dewatering device 105. Alternatively or additionally, the aqueous stream 100 may include mine drainage or water collected from a tailings dam.

[0080] According to one embodiment and Figure 2 As shown, an aqueous stream 200a obtained from a dewatering plant, here a tailings thickener 205a, originates from a flotation apparatus 216 comprising a mineral flotation circuit 211 arranged to process ore particles suspended in a slurry 212 by flotation to recover the ore.

[0081] The mineral flotation circuit 211 is arranged to separate the mineral slurry 212 into a mineral flotation circuit underflow 213 and a mineral flotation circuit overflow 214. The mineral flotation circuit overflow 214 contains the recovered material.

[0082] The flotation device 216 may be arranged to recover Ni and / or Cu. Figure 3 As shown, the flotation apparatus 316 may include a first mineral flotation circuit 311a arranged to recover Cu and a second mineral flotation circuit 311b arranged to recover Ni. The first and second mineral flotation circuits may have common or separate water circuits.

[0083] According to one embodiment, the dewatering apparatus comprises a settling device, which is a thickener. The thickener is configured to act as a solid-liquid separator to separate a sediment (i.e., a thickener underflow) from a supernatant (i.e., a thickener overflow). The thickener underflow contains particles having a higher density than one liquid, so the particles eventually enter the sediment.

[0084] The thickener may be a so-called concentrate thickener 405b, such as Figure 4 As shown. The overflow 414 of the mineral flotation circuit can be directed to the concentrate thickener 405b. In the concentrate thickener 405b, water absorbed by the particles and increasing the density of the recovered ore can be removed to enable the concentrate to be easily transported and allow further processing thereof. In the concentrate thickener 405b, the overflow 414 of the mineral flotation circuit is dewatered to produce a concentrate thickener overflow 400b and a concentrate thickener underflow 425. The concentrate thickener underflow 425 contains the recovered ore, i.e., the concentrate, and is taken out of the concentrate thickener 405b for further processing. The concentrate thickener overflow 400b can be processed according to the method disclosed herein.

[0085] Alternatively, the thickener may be a so-called tailings thickener 205a, 305a, such as Figure 2 and Figure 3 As shown. The underflow 213, 313b of the mineral flotation circuit can be directed to the tailings thickener 205a, 305a. In the tailings thickener 205a, 305a, the underflow 213, 313b of the mineral flotation circuit is dewatered to produce the tailings thickener overflow 200a, 300a and the tailings thickener underflow 215, 315. The tailings thickener overflow 200a, 300a can be processed according to the method disclosed herein. The tailings thickener underflow 215, 315 is removed from the tailings thickener 205a, 305a. The tailings thickener underflow 215, 315 is typically removed from the thickener as tailings. The solid content of the tailings thickener underflow 215, 315 can be at least 80wt.%.

[0086] According to one embodiment, the aqueous stream 100, 200a, 300a, 400b from which soluble and / or colloidal silicon compounds are removed comprises a thickener overflow. The thickener overflow may originate from a concentrate thickener 405b and / or a tailings thickener 205a, 305a. The thickener overflow comprises process water and soluble and / or colloidal silicon compounds. The thickener overflow may also comprise silicon-containing particles suspended and / or dissolved in the process water and other undesirable, harmful or unrecovered materials or compounds, such as fine particles and larger particles, starch-based inhibitors, microorganisms, etc.

[0087] Before the thickener overflow is allowed to proceed to clean flotation, it may be directed to a thickener overflow tank to stabilize the thickener overflow.

[0088] The coagulant and / or flocculant may be added to the aqueous stream 100, 200a, 300a, 400b in any suitable manner as long as proper mixing of the coagulant and / or flocculant with the aqueous stream 100, 200a, 300a, 400b is ensured. For example, the coagulant and / or flocculant may be added in a mixing unit.

[0089] According to one embodiment, the cleaning flotation is dissolved air flotation (DAF). DAF is a flotation process used in various applications for water or sewage purification. Solid particles are separated from liquids by using small flotation bubbles (which may be referred to as microbubbles). Microbubbles can be generated, for example, by dissolving air or other flotation gases into a liquid under pressure. When the dispersion is released, bubbles are formed in the pressure drop. Particles in solid form attach to the bubbles and rise to the surface. The floating sludge formed can be removed from the surface of the liquid as DAF overflow using a sludge drum.

[0090] Thanks to the described method, the turbidity of an aqueous stream can be reduced by 50-99%. Turbidity refers to the cloudiness or haziness of a fluid caused by a large number of individual particles that are generally not visible to the naked eye. Turbidity is caused by suspended solid matter in the form of very small particles that settle only very slowly or not at all or by colloidal particles.

[0091] According to one embodiment, the clean flotation underflow 104, 204, 304, 404 or at least a portion thereof is recycled back to the flotation process or a process prior to flotation.The clean flotation underflow 104, 204, 304, 404 or at least a portion thereof may be recycled to flotation, for example by grinding. Figure 3 A device is shown in which the clean flotation underflow 104, 204, 304, 404 or at least a portion thereof is recycled back to the flotation device 216, 316, 416 for mineral flotation. In the case where the water used for flotation or a process before flotation (e.g. grinding) is taken from the tailings area, the pH value of the water taken is relatively low because the pH value of the tailings water decreases over time. The metals contained in the tailings are more easily dissolved in water with a low pH value. For the flotation process, the pH value of the slurry must be increased, which causes the precipitation of the metals that were once dissolved. On the one hand, the precipitate can cause problems in the flotation process. The metals and other impurities contained in the water used may also cause the quality of the mineral surface that is already in grinding to deteriorate. Therefore, by recycling the clean flotation underflow back to flotation or even back to the process before flotation (e.g. grinding), the above problems can be avoided.

[0092] The coagulant may be selected from: inorganic coagulants, aluminium salts, iron salts, organic coagulants. Preferably, the coagulant is an aluminium salt or an iron salt. The coagulant is arranged to produce coagulation. Coagulation refers to the process by which colloidal particles and suspended solids become unstable, forming "microflocs" which can begin to coagulate if conditions are right. Coagulation is a chemical process involving charge neutralization. Coagulation is affected by the type of coagulant used, its dosage and quality; the pH and initial turbidity of the water to be treated; and the nature of the unwanted substances present.

[0093] In a colloidal suspension, particles settle very slowly or not at all because the colloidal particles carry surface charges that repel each other. This surface charge can be assessed using the zeta potential. To induce coagulation, a coagulant with an opposite charge is added to the water to overcome the repulsive charges and destabilize the suspension. Once the repulsive charges have been neutralized, van der Waals forces will cause the particles to aggregate and form flocs.

[0094] Flocculants can be synthetic polymers or natural polymers or their derivatives. Flocculants are agents that promote flocculation by causing colloids and other suspended particles in a liquid to aggregate to form flocs. Flocculation refers to a process in which particles that have become unstable actually combine into even larger aggregates (called flocs) so that they can be separated from the water by sedimentation or flotation. Many flocculants contain multivalent cations, such as aluminum, iron, calcium or magnesium. These positively charged molecules can interact with negatively charged particles and molecules to reduce obstacles to aggregation. Some flocculants may react with water and form insoluble hydroxides that, after precipitation, link together to form long chains or webs that physically capture small particles into larger flocs. Natural polymers or their derivatives can include, for example, starch or modified starch, or polysaccharides. Examples of synthetic polymers include, for example, high molecular weight (above 500,000) flocculants such as polyacrylamide (negatively or positively charged, or neutral), or Mannich products (positively charged); and low molecular weight (below 500,000) flocculants such as polyamine (positively charged), polyepiamine (positively charged), polyDADMAC (positively charged), poly(ethylene)imine (positively charged) or polyethylene oxide (neutral).

[0095] In order to promote the formation of flocs containing at least some silicon compounds and form a treated aqueous stream, flotation chemicals can be added to the aqueous stream. The flotation chemicals can include at least one of the following: a collector, an activator, a depressant, a frother, a modifier. The collector can include a surface active organic agent, such as a mercaptan compound, an alkyl carboxylate, an alkyl sulfate, an alkyl sulfonate, an alkyl phosphate, an amine, a chelating agent, and an alkyl phosphonic acid. The activator can include, for example, a metal hydroxyl compound or sodium sulfide. The depressant can include, for example, sodium sulfide or a cyanide salt. The frother can include, for example, an alcohol, a polyether, ethylene oxide, and a polyethylene glycol ether.

[0096] According to one embodiment, the pH of the aqueous stream 100, 200a, 300a, 400b is adjusted to a pH in the range of 4.5-10 before subjecting the treated aqueous stream 101, 201, 301, 401 to cleaning flotation. The pH of the aqueous stream may be adjusted before adding coagulants and / or flocculants and / or flotation chemicals to the aqueous stream. Thus, the pH of the treated aqueous stream 101, 201, 301, 401 is in the range of 4.5-10 before subjecting it to cleaning flotation.

[0097] According to one embodiment, iron salts are used as coagulants. In this case, the pH of the aqueous stream 100, 200a, 300a, 400b may be adjusted to a range of 5-8 before subjecting the treated aqueous stream 101, 201, 301, 401 to clean flotation to obtain efficient coagulation. A pH range of 5-8 may be preferred because it is known that iron hydroxide precipitates within the pH range. The pH of the aqueous stream may be adjusted in any suitable manner. For example, the pH may be adjusted in a mixing unit. Using iron salts as coagulants is beneficial because the aqueous stream already contains iron, and therefore a smaller amount of coagulant may be required to obtain the desired coagulation. In addition, the flocs formed using iron salts as coagulants may be more durable under clean flotation conditions, thereby improving the efficiency of clean flotation.

[0098] The method described herein has the effect that the treated process water (i.e. the liquid obtained from the cleaning flotation unit) is pure with respect to the content of soluble and / or colloidal silicon compounds, so that the treated process water can be reused without negatively affecting the process results. Depending on the composition of the aqueous stream in question, Si removal rates of 55-90% can be obtained.

[0099] Furthermore, since aqueous streams typically contain Fe complexed with Si, the method also provides a route for removing at least some of the iron contained in aqueous streams of mineral processing equipment. Problems caused by complexes containing Si and Fe, as well as excess iron itself, can thus be avoided. Depending on the coagulant dosage and the composition of the aqueous stream, about 60-90% of the iron contained in the aqueous stream can be removed by the method disclosed herein.

Claims

1. A method for removing soluble and / or colloidal silicon compounds from an aqueous stream (100, 200a, 300a) of a mineral processing facility, the method comprising: include: - adding a coagulant and / or a flocculant and / or a flotation chemical to the aqueous stream (100, 200a, 300a) to promote the formation of flocs comprising at least some silicon compounds and forming a treated aqueous stream (101, 201, 301), - subjecting the treated aqueous stream (101, 201, 301) to clean flotation to separate out at least some of the silicon compounds as clean flotation overflow (103, 203, 303), and - Removing clean flotation overflow (103, 203, 303); wherein the clean flotation comprises gas bubbles, at least 90% of which have a diameter of 0.2 to 250 μm, wherein the aqueous stream (100, 200a, 300a) comprises water obtained from a dewatering device (105), wherein an aqueous stream (100, 200a, 300a) comprising water obtained from a dewatering device (105) originates from a flotation device (216, 316) comprising a mineral flotation circuit (211, 311a, 311b) arranged to process ore particles suspended in a slurry (212, 312) by flotation to recover the ore; wherein the mineral flotation circuit (211, 311a, 311b) is arranged to separate the ore pulp (212, 312) into an underflow (213, 313a, 313b) of the mineral flotation circuit and an overflow (214, 314a, 314b) of the mineral flotation circuit; and The aqueous stream (200a, 300a) originating from the flotation device (216, 316) including water obtained from the dewatering apparatus (105) is the underflow (213, 313b) of the mineral flotation circuit.

2. The method according to claim 1, wherein the dewatering device (105) comprises a sedimentation device or a filter.

3. The method according to claim 2, wherein the settling device is a thickener (205a, 305a).

4. The method according to claim 1, wherein the aqueous stream (100, 200a, 300a) comprises at least a portion of a stream obtained from the dewatering device (105).

5. The method of claim 1, wherein the flotation device (216, 316) is arranged to recover Ni and / or Cu.

6. A method according to claim 5, wherein the flotation device (216, 316) comprises a first mineral flotation circuit (311a) arranged to recover Cu and a second mineral flotation circuit (311b) arranged to recover Ni.

7. The method according to any one of claims 1 to 6, wherein the method further comprises recycling at least a portion of the clean flotation underflow (104, 204, 304) back to the flotation process or a process prior to flotation.

8. The method according to any one of claims 1 to 6, wherein the coagulant is an aluminum salt.

9. The method according to any one of claims 1 to 6, wherein the coagulant is an iron salt.

10. The method according to any one of claims 1 to 6, wherein the pH of the aqueous stream (100, 200a, 300a) is adjusted to within the range of 4.5 to 10 before subjecting the treated aqueous stream (101, 201, 301) to cleaning flotation.

11. The method of any one of claims 1-6, wherein the aqueous stream (100, 200a, 300a) comprises Fe complexed with Si, and the method comprises removing at least some of the Fe from the aqueous stream (100, 200a, 300a).

12. The method according to any one of claims 1 to 6, wherein the cleaning flotation is dissolved air flotation.

13. A device for removing soluble and / or colloidal silicon compounds from an aqueous stream (100, 200a, 300a) of a mineral processing facility, the device comprising a mixing system arranged to provide coagulants and / or flocculants and / or flotation chemicals to the aqueous stream (100, 200a, 300a), a clean flotation cell (102, 202, 302) arranged to separate at least some silicon compounds from the aqueous stream (100, 200a, 300a) as a clean flotation overflow (103, 203, 303) and to form residual process water as a clean flotation underflow (104, 204, 304), wherein the clean flotation comprises gas bubbles, at least 90% of which have a diameter of 0.2 to 250 μm, The device also includes - a dewatering device (105), and a flotation device (216, 316) comprising a mineral flotation circuit (211, 311a, 311b) arranged to process ore particles suspended in a slurry (212, 312) by flotation to recover the ore, wherein the mineral flotation circuit (211, 311a, 311b) is arranged to separate the ore pulp (212, 312) into an underflow (213, 313a, 313b) of the mineral flotation circuit and an overflow (214, 314a, 314b) of the mineral flotation circuit, and wherein an underflow (213, 313b) of the mineral flotation circuit is configured to be directed to a dewatering device (105), wherein the aqueous stream (100, 200a, 300a) comprises water from the dewatering device (105).

14. The apparatus according to claim 13, wherein the dewatering device (105) comprises a sedimentation device or a filter.

15. The device according to claim 14, wherein the settling device is a thickener (205a, 305a).

16. Apparatus according to claim 13, wherein the flotation device (216, 316) is arranged to recover Ni and / or Cu.

17. The apparatus according to any one of claims 13 to 16, wherein the cleaning flotation unit (102, 202, 302) is a dissolved air flotation unit.

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