Method for treating water contaminated with manganese and iron, and corresponding equipment

Abstract

The present patent of invention relates to a method for treating effluent in which a chemical reagent is dispensed directly onto aqueous liquid effluent generated continuously or intermittently, especially effluent containing iron and manganese in its composition. The invention is applicable in the field of mining in general and in the field of effluent treatment in particular, through the metered and automatically controlled introduction of calcium peroxide or calcium peroxide in conjunction with calcium oxide directly into the effluent containing the toxic metals, using autonomous equipment and instruments or controlled dissolution systems (in the form of pellets or balls), capable of accommodating different flow rates and concentrations of iron and manganese in the effluent.

Description

[0001] PROCESS FOR TREATMENT OF WATER CONTAMINATED WITH MANGANESE AND IRON AND CORRESPONDING EQUIPMENT

[0002] Field of invention

[0003] The present invention patent refers to a process for treating wastewater and other effluents containing levels of iron (Fe) and manganese (Mn) above the acceptable legal parameters, applied in the environmental field, more specifically in the area of ​​treatment and remediation of toxic metals in water originating from mining effluents with the purpose of promoting their reuse or adequate disposal within legal parameters, with the advantages of using a form of application of the remediation product through a portable dosing equipment or even through other forms of delivery of the active ingredient calcium peroxide, such as the use of self-soluble tablets, low cost and easy to install and being a relatively simple process aligned with ecological and sustainable issues.

[0004] Fundamentals of the invention

[0005] The growing contamination of water by toxic metals such as Mn and Fe has become a key concern for environmental preservation and public health. These metals, often present in industrial effluents and mining wastewater, have harmful impacts, including bioaccumulation in aquatic fauna and toxicity risks throughout the food chain. In response to this problem, it is becoming increasingly necessary to develop solutions that reduce their concentrations to environmentally safe levels that are in line with regulations.

[0006] The urgency for advanced treatment technologies intensified after events like the Mariana environmental disaster, which highlighted the consequences of releasing mining waste into water bodies. In addition to the immediate effects, continued contamination and the natural runoff of these metals in mining regions reinforce the need for effective methods that can meet the demand for safer and more sustainable aquatic environments. Containing and removing Mn and Fe from water are essential measures to prevent ecosystem deterioration and protect nearby communities.

[0007] REPLACEMENT SHEET (RULE 26) After searching the Brazilian and international patent databases, the following disclosures were found.

[0008] Patent JP2014233657A discloses a treatment device for water contaminated with high Fe and Mn contents, designed to optimize space and ensure the stability of membrane filtration operations. The system includes specific technical steps: first, an oxidant is added to oxidize soluble Fe and Mn, forming insoluble particles. The water then passes through a treatment tank with a manganese dioxide IV (MnCF) catalyst, accelerating the oxidation. Turbidity removal then occurs, eliminating the particles formed, preparing the water for final membrane filtration, which retains remaining residues and ensures process efficiency and reliability in a reduced space.

[0009] Although patent JP2014233657A presents an innovative solution to the problem, it still presents significant technical challenges. The use of manganese dioxide increases maintenance costs due to its frequent replacement. The system requires precise oxidant dosage for effective iron and manganese oxidation; failure to do so can compromise filtration and increase the risk of membrane and tank clogging. Furthermore, the device is sensitive to variations in water conditions, requiring constant monitoring of the steps to prevent wear, which limits its applicability in waters with high solids concentrations and in large-scale operations.

[0010] Patent JP2022054063A proposes an optimized approach for treating water containing Mn and Fe, utilizing a minimized combination of substrates and reagents to maximize efficiency and reduce excessive chemical use. Instead of adding large amounts of sodium hypochlorite (NaClO) to oxidize the metals, the described method combines the addition of hydrogen peroxide (H2O2) and a column of biological activated carbon, followed by a flocculation and filtration step. This process allows for efficient removal of Mn and Fe, even when the water also contains organic substances such as ammonia (NH3) and humic acids.

[0011] Although patent JP2022054063A offers an interesting solution for treating water contaminated with Fe and Mn, its reliance on H2O2, NaClO, and flocculant reagents can generate high costs and undesirable byproducts. Furthermore, the efficiency of activated carbon can be compromised in waters with a high organic matter load, requiring strict control of operational parameters that, on a large scale, can compromise the process. Maintenance and regeneration of activated carbon can also pose an additional challenge in terms of costs and ongoing efficiency.

[0012] Patent TW202246187A describes a method and device for treating water containing Mn and Fe using ozone (O3) to oxidize these metals. The objective of oxidation is to transform the metals into insoluble substrates, such as iron oxides (Fe2O3) and manganese oxides (MnCE), or iron hydroxides (Fe(OH)3) and manganese oxides (Mn(OH)2), which precipitate in the medium and can be easily removed by filtration. The use of O3 aims to increase process efficiency while minimizing the use of other chemical reagents, such as NaClO. This treatment ensures effective contaminant removal, improving water quality and meeting required environmental standards.

[0013] Although patent TW202246187A presents an efficient solution for the treatment of water contaminated with Mn and Fe, the high cost of generation, the need for precise dosage control and the efficient removal of oxidation byproducts by O3 are critical points that may limit its technical viability, especially in highly contaminated waters or on a large scale.

[0014] Patent JP2016120467A discloses a water treatment equipment and method aimed at reducing Mn and Fe levels over a wide pH range. The equipment includes a chemical supply tank for adding chemicals to the water to be treated, and a sand filtration device for filtering the water after chemical addition. Reagents used in the process include bromine (Br)-based oxidants or compounds that react between a Br compound and a chlorine (Cl)-based oxidant, and a sulfamic acid compound (H3NSO3). Alternatively, the system can use a Cl-based oxidant or products of the reaction between Br and Cl compounds with H3NSO3.

[0015] Although patent JP2016120467A presents an interesting solution for Mn and Fe removal over a wide pH range, the use of Br- and Cl-based oxidizing compounds, along with H3NSO3 acid, can produce undesirable and difficult-to-control byproducts, which can pose environmental and safety risks. Furthermore, pH control during the process can be challenging, as the addition of acidic reagents can cause fluctuations in water pH, affecting the efficiency of metal precipitation and subsequent filtration. The reliance on sand filtration is also a critical point, as the effectiveness of this step depends on the adequate size of the precipitates, which is not always guaranteed. Finally, high reagent consumption and operational complexity can increase process costs, making it less viable on a large scale.

[0016] The article “Manganese removal processes and geochemical behavior in residues from passive treatment of mine drainage” (Le Bourre, B. et al. Chemosphere, v. 259, n. 127424, p. 127424, 2020) addresses the limitations of passive treatment in removing Mn from mine drainage, particularly due to the interference of Fe. Four samples were tested: real acid mine drainage treatment residues, real contaminated neutral drainage, synthetic neutral drainage, and a calcite sample. Mn immobilization occurred primarily in the form of MnOx, but the efficiency of the process was compromised in some cases by the presence of Fe. Semi-calcified dolomite showed good results in some cases, but the pH of the treated residues did not always meet the criteria required for safe disposal, making the process not essentially environmentally friendly.

[0017] The article "A review of the implications and challenges of manganese removal from mine drainage" (Neculita, CM; Rosa, E. A review. Chemosphere, v. 214, p. 491-510, 2019) presents an overview of the impacts of Mn on human health and ecosystems, highlighting the need to treat mine drainage. The study discusses technical options for dealing with Mn contamination, covering physicochemical and biological processes, with a special focus on passive treatment systems. Furthermore, it addresses the challenges, design criteria, and operational requirements of these methods, offering insights into future research needed to overcome the difficulties in Mn removal during mine drainage treatment. The study also highlights the advantages and disadvantages of each methodology.

[0018] Chinese patent CN115321692B describes a slow-release oxygen material and a method for in situ Mn removal from groundwater in alpine regions. The material, composed of calcium peroxide surrounded by a slow-release carrier, forms microspheres that control the rate of oxygen release. This limits direct contact between the calcium peroxide and water, releasing oxygen in the amount necessary for the growth of microorganisms, optimizing wastewater treatment.

[0019] The process of Chinese patent CN115321692B is related to the use of calcium peroxide for manganese treatment, but its application is aimed at the treatment of alpine groundwater, as well as the process for producing said material in microspheres, in addition to being complex and expensive, involves several non-environmentally friendly production steps, mainly due to the use of dichloromethane, a highly toxic substance.

[0020] U.S. patent No. US2456196 discloses compartment-type electrolytic cells designed for washing or recovering Mn and similar metals, with the aim of removing anode sludge and improving process efficiency. The invention applies to electrolytic cells in which the anodes are suspended in a compartment, separated from the cathodes by porous diaphragms.

[0021] Despite the good results of US patent US2456196, the process is quite complex and involves several steps, which can be challenging and result in constant maintenance.

[0022] European patent EP3342757A1 describes an efficient method for removing Mn from wastewater, minimizing the use of chemicals, including neutralizers. The invention applies to wastewater from a wet smelting process for nickel oxide ore, where an acid is added to the ore and the mixture is subjected to pressure leaching to recover the nickel. The method involves regulating the pH of the wastewater to a value between 8.0 and 9.2, followed by applying a pH-adjusted liquid to a drainage path containing manganese-oxidizing bacteria.

[0023] Despite the efficiency of the method of European patent EP3342757A1, the use of bacteria for metal remediation can lead to the formation of other substrates in the reaction medium, of greater or lesser toxicity.

[0024] The article “Manganese removal from acid mine drainage by a consortium of Mn-oxidizing bacteria in a continuous stirred tank bioreactor: Long-term treatment and reactive mixture characterization” (MAO, Q. et al. ACS ES&T Water, v. 3, n. 6, p. 1620-1629, 2023) evaluated the bioremediation effectiveness of Mn-rich acid mine drainage using a consortium of Mn-oxidizing bacteria in a continuous stirred tank bioreactor. The experiment, carried out at pH 5.5 and a hydraulic retention time of 48 hours, obtained a high removal rate of Mn (86.5%) and other metals such as Cu (98.8%), Zn (96.9%), and Cd (97.0%). The bacteria Acinetobacter and Azospirillum have been identified as responsible for Mn oxidation, forming biogenic precipitates such as MnCE, MnOOH, and MnCCE.The results indicate the effectiveness of the process in treating acid drainage rich in Mn; however, the treatments demonstrated use high pH conditions and substrate concentrations, which can cause an even greater environmental problem.

[0025] The article "Use of ozone to remediate manganese from coal mine drainage waters" (TEW ALT, SJ et al. Journal of the American Society of Mining and Reclamation, v. 2005, n. 1, p. 1166-1177, 2005) describes the difficulty in removing Mn from acid mine drainage and presents a method using ozone to oxidize it and precipitate it as oxide. Laboratory experiments have validated the process for treating acid mine drainage, resulting in significant reductions in the concentrations of manganese, iron, cobalt, and nickel in the treated effluent. However, the processes used to remove these metals are not inherently environmentally friendly.

[0026] In this scenario, the developed solution proposes a relatively simple yet highly efficient approach to treating effluents and water contaminated with toxic metals. With an innovative system for removing and controlling Mn and Fe, this technology allows wastewater to be brought into compliance with environmental standards, minimizing the risks of bioaccumulation and toxicity. This technology contributes significantly to the sustainability of industrial activities and the preservation of water quality, benefiting both the environment and human health.

[0027] The present invention relates to a process for treating water contaminated with high levels of Mn and Fe from mining effluents. This process involves oxidation, precipitation, and removal of these metals, increasing dosing efficiency, reducing precipitation time, and enhancing environmental control. The proposed innovations aim to optimize the use of CaCE reagent in this treatment, improve process automation, and ensure greater operational robustness under varying flow rates and effluent composition.

[0028] The process includes a conventional reagent dosing system directly into the water body using an automatic doser or even the release of the active ingredient calcium peroxide (CaCE) through tablets that slowly dissolve in the effluent, allowing for controlled and continuous dosing, as needed. This modification offers a number of benefits, such as eliminating complex dosing equipment and reducing operating costs. The gradual dissolution of CaCE also provides greater efficiency in contaminant oxidation, minimizing waste and ensuring process stability, regardless of fluctuations in flow or contaminant concentration in the effluent. The developed technology provides a robust and low-cost solution for the treatment of contaminated water, aligning with the most stringent environmental requirements.Furthermore, the system solves a wide range of technical problems not solved by previous versions.

[0029] The prior art presents the following technical problems and shortcomings, which were resolved by the present invention, as shown below: a. Lack of portability of equipment for treating water contaminated with mining effluents. This is resolved by the inclusion of portable equipment consisting of an automatic, low-energy, sunlight-powered doser or controlled-solubility tablets, allowing for easy, low-cost application of the remediation agent under severe conditions; b. Use of substrates with higher toxicity, such as sulfamic acid, hypochlorite, bromine, ammonia, or other substances with toxic or environmentally unsuitable characteristics, which may generate undesirable byproducts in the process.Solved by the use of calcium peroxide, a mild oxidizer and long-lasting dissolved oxygen releaser with very low environmental toxicity, which selectively acts on target metals, especially manganese, to form substrates with lower solubility, being completely consumed and generating no reaction byproducts; c. Use of equipment that requires high-consumption energy sources, with or without the use of oxygen cylinders to generate less toxic oxidants such as ozone. Solved by the direct introduction of calcium peroxide into the aqueous medium, which also releases oxygen in molecular form, capable of acting on manganese, oxidizing it to insoluble forms; and d. Continuous addition of substrates during the process stages, requiring constant replenishment.Solved by using CaCU in tablet form, resulting in controlled substrate release and dosage with a longer duration, requiring fewer operational changes or feedings, reducing operational costs, and acting as a passive water decontamination technology. Brief description of the drawings.

[0030] For a better understanding of this patent, the following figures are attached:

[0031] Figure 1 shows the flowchart of the process for treating water contaminated (AC) by Mn and Fe from mining effluents using a static mixer consisting of baffles and an automatic screw-type doser;

[0032] Figure 2 shows the schematic representation of the alternative form of equipment and process for treating water contaminated (AC) by Mn and Fe from mining effluents, optionally using a permeable basket with controlled release tablets (or spheres) of Calcium Peroxide or Calcium Peroxide together with Calcium Oxide;

[0033] Figure 3 shows the graph showing the variations in calcium and manganese peroxide concentrations at times 5 and 10 minutes;

[0034] Figure 4 shows the graph showing the effectiveness of manganese precipitation as a function of time for a fixed product dose of 250 g / ml; and

[0035] Figure 5 shows a graph of manganese concentrations as a function of time for varying iron concentrations.

[0036] The laboratory experiments that confirmed the results that culminated in this invention patent demonstrate the significance of the existence of three possible manganese oxides: extensive laboratory studies demonstrated that after treating solutions containing manganese with the described invention, manganese concentrations were almost completely eliminated (over 99.9% efficacy), with concentrations remaining below the limit of quantification (an ICP / OES device with high enough precision to detect up to 50 micrograms per liter of manganese was used for detection). The fact that manganese was eliminated at unquantifiable levels in the solutions indicates that the oxides likely to have formed are MnO and MmCU, both brown in color and insoluble in water.The tested solubility of 5 to 10 mg / L for manganese oxide (II) is sufficient for a few remaining milligrams of manganese to still be soluble in water, which was not observed experimentally. This experimental observation is consistent with the theory that describes the electronic behavior of manganese ions and their strong thermodynamic tendency to form stable compounds with oxygenated species. Furthermore, the simultaneous presence of Mn ions. 2+ and Mn 3+ in solution offers the ions a new precipitation route, via the mixed-valence oxide, which is also insoluble. Finally, the invention presented here also relies on a manganese precipitation route through the formation of manganese oxyhydroxide, MnOOH, which occurs naturally in the form of the mineral manganite. The manganite formed is also extremely insoluble in water, with the Mn ion 3+Its constituents have a solubility of approximately 1.0 x 10-18 mol / L in pure water. Manganite, like the mixed oxide, offer pathways for the precipitation of trivalent manganese, which may either already be present in the effluent or may be generated by the oxidation of divalent manganese.

[0037] The chemical reactions that govern the present invention, making it so effective in converting soluble metals into insoluble precipitates, are as follows.

[0038] Mechanism 1 for the formation of hydrogen peroxide:

[0039] Mechanism 2: co-precipitation of manganese with iron, with the OH ion coming from the reaction of CaO2 with water:

[0040] Mechanism 3: reaction of manganese directly with the released molecular oxygen (02), forming manganite (MnOOH):

[0041] Mechanism 3 is the most common precipitation mechanism, due to the large amount of oxygen released by calcium peroxide. However, all possible processes contribute to precipitation, resulting in complex mixtures of oxides and hydroxides.

[0042] Essentially, the invention presented here directly improves mining effluent by forming iron and manganese oxides immediately after the introduction of the oxidizing chemical reagent calcium peroxide. The chemical reaction reaches its maximum efficiency after ten minutes, when approximately 99.9% of the iron and manganese present in the medium are converted to insoluble oxides.

[0043] Manganese(II) oxide, generated in the precipitation process, is a dark brown solid formed by direct reaction with the oxide anion. It has the molecular formula MnO and is virtually insoluble in water, soluble only in concentrated solutions of some inorganic acids, such as concentrated hydrochloric acid (HCl). Manganese(III) oxide, with the formula Mn2Ü3, appears as a black powder and has a solubility in water of 5 to 10 mg / L, depending on the crystal structure of the resulting solid, which varies according to different methods of production. There is also a mixed-valence oxide, manganese(II) and (III) oxide, with the formula MmC. This mineral is a dark brown solid and, like MnO, is insoluble in water and only soluble in highly acidic solutions.

[0044] These manganese oxides, oxyhydroxides, and mixed oxides possess the desirable characteristics of being extremely stable, presenting very low solubility, and exhibiting no toxicity or mobility in environmental compartments. The scientific literature reports extremely low solubility for all of these compounds (reference: Perry, Dale L. Handbook of inorganic compounds. CRC press, 2016), except under very extreme conditions, such as solubility in concentrated hydrochloric acid (370 g / L). Thus, the stability of the precipitates formed by the invention ensures a lasting solution to the problem of effluents contaminated with large amounts of manganese, with or without the presence of iron. In fact, rigorous laboratory tests demonstrated that the solid formed, after remaining agitated for 24 hours, undergoes a maximum solubilization of only 0.01% in the form of manganese, and this solubilization is unaffected by pH in the range studied (5 to 9).It was shown that the resulting solid presents characteristics of resistance to pH changes reminiscent of calcium peroxide, which contributes to its stability against small changes in pH.

[0045] Essentially, the invention presented here solves two fundamental problems related to the need to treat water contaminated with iron and manganese in dissolved forms. The first concerns portability, with its applicability in regions lacking infrastructure and adaptability to flow variations. The second concerns the formation of non-toxic substances resulting from the manganese oxidation process, reincorporating these metals into the environment in a safe and stable manner. The main substances formed are manganese oxides and hydroxides, and in cases where iron is also present, oxides and hydroxides of this second metal. Furthermore, the presence of iron, which frequently occurs alongside manganese in liquid effluents from mining, can aid in the manganese precipitation process. It has been reported in the scientific literature that manganese ions can be co-precipitated by iron(III) hydroxides.This provides another additional route for manganese precipitation, as it is independent of the oxidizing species and occurs simply through the formation of mixed iron and manganese hydroxides. Because iron(III) hydroxide is an extremely weak base, its tendency to precipitate as a base is very high (its solubility product is Ksp = 4.0 x 10-38). Since the invention causes a slight increase in the pH of the water being treated, this pH will invariably aid in the rapid precipitation of any iron present, which in turn will aid in the precipitation of manganese.

[0046] Laboratory tests indicate that for concentrations of 30 mg / L of manganese dissolved in water and varying the calcium peroxide application dosage between 100 mg / L and 500 mg / L, we obtained a reduction of more than 4x in the dissolved manganese concentration for a 5-minute contact time with doses greater than 500 mg / L. Meanwhile, for the 10-minute contact time of the dissolved manganese with calcium peroxide, we obtained reductions of 6x in the concentration of the same with only 150 mg / L of calcium peroxide, achieving a 98.1% reduction for 250 mg / L of the reagent and a 100% reduction for 500 mg / L. Thus, it can be concluded that the most efficient reaction from an economic perspective occurs with the longest contact time between the effluent and the calcium peroxide reagent. As shown in figure 5, which illustrates the graph showing the variations in the concentrations of calcium peroxide and manganese at times 5 and 10 minutes.

[0047] While monitoring several water treatment projects at mining sites, the inventors realized the difficulty of implementing efficient solutions that were simultaneously practical, economical, and suitable for the harsh environmental conditions of these areas. Large, heavy equipment required for conventional treatment was unfeasible due to high costs, lack of electricity, and difficult access. The need arose for a more agile and flexible solution to effectively treat effluents without compromising the environment or financial viability.

[0048] The solution for dissolved Manganese and Iron present in the bottom drains was based on the precipitation of manganese, where the oxidative pathway proved to be more promising, and does not require ideal conditions for the conversion of soluble manganese to oxides and the formation of insoluble precipitates.

[0049] The first approach evaluated was ozone generation and direct application to bottom drains, generating manganese and iron oxides. According to existing articles, one of the solutions used worldwide for similar treatments uses this technology. However, it proved unfeasible due to high investment costs, and the difficulties with energy supply and oxygen cylinder consumption would make this alternative unviable.

[0050] In research carried out in scientific publications, it was observed that dissolved Manganese can also be viably oxidized by the Calcium Peroxide reagent, since there is formation of free oxygen radicals capable of converting Manganese into stable and insoluble oxides.

[0051] During their research, the team observed, for the first time, the surprising effect that the use of CaO2, a widely available compound with great potential for oxidizing Mn and Fe, could be a good alternative to solve these problems. During several tests conducted by the inventors, CaCh proved highly effective in oxidizing Mn and Fe, converting these soluble metals into insoluble forms, such as oxides and hydroxides, which can be easily removed by precipitation and filtration.

[0052] Laboratory tests indicate that for concentrations of 30 mg / L of manganese dissolved in water and varying the calcium peroxide application dosage between 100 mg / L and 500 mg / L, we obtained a reduction of more than 4x in the dissolved manganese concentration for a 5-minute contact time with doses greater than 500 mg / L. Meanwhile, for the 10-minute contact time of the dissolved manganese with calcium peroxide, we obtained reductions of 6x in the concentration of the same with only 150 mg / L of calcium peroxide, achieving a 98.1% reduction for 250 mg / L of the reagent and a 100% reduction for 500 mg / L. Thus, it can be concluded that the most efficient reaction from an economic perspective occurs with the longest contact time between the effluent and the calcium peroxide reagent. As shown in figure 3, which illustrates the graph showing the variations in the concentrations of calcium peroxide and manganese at times 5 and 10 minutes.

[0053] It was also observed that by setting the calcium peroxide remediation reagent dose at 250 mg / L, the ideal time to achieve a reduction of more than 90% of the dissolved manganese occurs in approximately 10 (ten) minutes of contact, reaching a peak of 100% after 30 (thirty) minutes of contact. Thus, it is concluded that calcium peroxide concentrations lower than 200 mg / L can be used for effective manganese precipitation; however, contact times longer than 15 (fifteen) minutes should be considered. This can be easily resolved since this contact time can occur within the tributary stream itself downstream of the dosing and mixing equipment. As shown in Figure 4, which illustrates the graph showing manganese precipitation effectiveness as a function of time for a fixed product dose of 250 g / ml.

[0054] The presence of soluble iron in the effluent from mining tailings drains also showed little influence up to a concentration of 86 mg / L. Furthermore, the absence of iron slows the formation of precipitates precisely because iron also forms precipitates that aid decantation. The presence of PAM (polyacrylate) also proved effective in accelerating the process and forming precipitates, as shown in the figure, which illustrates manganese concentrations as a function of time for varying iron concentrations.

[0055] In a pilot test of the technology for reducing manganese directly into the bottom drains of an iron ore tailings dam belonging to a major Brazilian mining company, the technology proved to be highly viable, offering high portability, ease, and speed of installation and adjustment. Furthermore, during the testing period, significant impacts were observed on manganese concentrations, using the following metric points: Dam Outlet and Stream. Analyses were conducted in the field and in two INMETRO-accredited laboratories (ISO 17025:2017), which conclusively confirmed the efficiency results.Thus, based on the analyses of both laboratories, it was possible to confirm a reduction of up to 99.60% in the concentrations of total manganese and up to 99.25% in the reduction of dissolved manganese, meeting the guiding values ​​CONAMA 357 / 2005 (limit of 0.1 mg / E of total manganese for class II surface water) and CONAMA 430 / 2011 (limit of 1 mg / L of dissolved manganese for effluent discharge).

[0056] In addition to the demonstrated physicochemical properties of calcium peroxide, the effective remediation agent for reducing dissolved manganese and iron, it also has extremely positive environmental benefits. This substance not only promotes the oxidation of target metals by releasing molecular oxygen, but also the excess oxygen generated and not consumed in the oxidation process promotes more suitable conditions for sustaining the life of microorganisms, aquatic plants, and fish. The dissolved oxygen present in the water from the manganese reduction treatment also aids in the purification of undesirable organic substances, such as sewage organic matter.The raw material for calcium peroxide production is calcium carbonate, a naturally occurring mineral that does not contain other toxic elements, such as heavy metals, carcinogens, or even iron and manganese. Therefore, the product used for water treatment is also extremely safe for environmental applications and in water treatment, as it contains no harmful contaminants. Various bibliographies also demonstrate this.

[0057] Calcium peroxide is obtained from the mineral Calcium Carbonate (CaCCh) which, when heated, is converted to calcium oxide (CaO) and subsequently, through reaction with Hydrogen Peroxide (H2O2) under specific conditions of temperature and pressure, another oxygen is inserted into the molecule, forming calcium dioxide (CaCh).

[0058] The chemical reaction mechanism of calcium peroxide provides the following solutions for treating drain bottom waters containing manganese and soluble iron: 1) Instantaneous conversion of soluble metals to their insoluble form, which begins when calcium peroxide dissolves in the aqueous medium, releasing molecular oxygen and reacting with these metals. 2) Natural precipitation by gravity in the stream or riverbed of manganese and iron oxides, in their insoluble form, is reincorporated into the environment safely and non-toxically. 3) Excess oxygen generated by calcium peroxide, not used in the process of converting metals into oxides, will aid in the recovery of local streams and rivers by introducing more oxygen into the environment, which, as a side effect, will promote the growth of natural flora and fauna, thus expanding life in these areas.4) The precipitates formed can be more easily removed in the process by simply inserting physical separation processes such as centrifuges, decanters, or filters. 5) Substances called polyelectrolytes or coagulation facilitators can also be added to increase the settling rate of the precipitates formed, enabling their application in wastewater treatment plants for high flow rates or high concentrations of manganese or iron in the medium. 6) As a means of delivering the calcium peroxide treatment agent, tablets or spheres can be used to gradually release the reactive substance into the aqueous medium.

[0059] During the development of the process for this patent, a new discovery emerged with a surprising effect: the introduction of calcium oxide as a way to optimize the use of peroxycalcium in the treatment of contaminated water, especially in situations where there is a high presence of iron. It acts as a natural pH increaser, promoting an increase in alkalinity, which is essential for iron precipitation, since iron hydroxide is formed under basic conditions.

[0060] Table 1: Calcium Peroxide Specification

[0061] With this new discovery, the Two-Step Treatment Process: The proposed approach involves a two-step treatment. First, calcium oxide would be used to precipitate the iron, forming iron hydroxide. Then, after the iron hydroxide is removed, calcium peroxy would be applied to treat the manganese. This sequence is proposed to maximize treatment efficiency and minimize calcium peroxide consumption, since the initial iron treatment would reduce the load on the calcium peroxide. The addition of calcium oxide is seen as a way to reduce operating costs, since the use of calcium peroxide would be reduced by the action of calcium oxide in treating the iron. This strategy is not only cost-effective but also promotes more effective treatment of contaminated water, simultaneously addressing the presence of iron and manganese.

[0062] The quantity of chemical reagents Calcium Peroxide and Calcium Oxide will vary according to previous chemical analyses of the quantities of iron and manganese in the mining waste and are pre-mixed before dosing in the effluent.

[0063] Description of the invention

[0064] The treatment process described in this patent is carried out in the following steps, as shown in Figure 1: I. It consists of a method of reducing the elements Iron and Manganese, through the insertion, delivery or controlled dosage of calcium peroxide directly into surface water bodies, effluents and other wastewater with concentrations of these dissolved toxic metals above the desired limits;

[0065] II. For the method of delivery, dosage and insertion of calcium peroxide into aqueous media, a powder product dosage system can be used, in an automated and self-controlled manner by equipment (1) consisting of a containment basin (11), driven by automatic water piping (12) and fed into equipment (1) equipped with a powder doser (14) that feeds the chemical reagents calcium oxide and / or calcium peroxide, in an ideal calculated dosage, allowing toxic metals to be removed from the aqueous medium by simple gravity decantation;

[0066] III. Method of dosing, incorporating and dissolving calcium peroxide consisting of the direct insertion into the aqueous medium of tablets or spheres of calcium peroxide and calcium oxide arranged in permeable metal baskets, allowing the controlled release and dosage of the active ingredient, converting the soluble toxic metals to insoluble precipitates that can be removed from the aqueous medium by simple gravity decantation;

[0067] IV. Method that converts dissolved metals into oxide and hydroxide substances of very low solubility, allowing them to: a) settle naturally in the streambed; b) be removed by gravity through sedimentation tanks; c) removed by filters or membranes; and d) by other complementary physical methods such as centrifuges or similar; and

[0068] V. After dosing, incorporating, dissolving and mixing calcium peroxide and / or calcium oxide in the water or effluent, flocculants or polyelectrolytes may be added to aid precipitation, reducing the precipitation time to seconds, where the stable precipitates will sediment naturally in the stream or may be removed by physical systems such as sedimenters, filters or other complementary methods.

[0069] The equipment and instruments of the present patent consist of: equipment (1) for dosing and incorporating chemical reagents, essentially composed of a containment basin (11); piping (12) connected to the outlet of the basin (11); automatic water flow meter (13) of the flowmeter type or similar, positioned in the piping (12); powder doser (14) of the dosing screw type or similar, positioned above the piping (12); programmable logic controller (15), electrical power supply (16) of the 12 V battery type or similar; flow and concentration meters (17) for determining concentrations and flow rates of aqueous suspensions in line, positioned after the mixer; static mixer (18) for low flow rates.

[0070] The equipment and instruments will be powered by an electric motor for dosing the calcium oxide and calcium peroxide mixture; a remote communication system (3) using satellite or telephone technology; a motor for stirring and mixing the calcium peroxide and flocculant in-line; a PLC programmable logic controller (15), or equivalent technology, with low power, powered by a solar panel in conjunction or not with a hydroelectric microturbine, depending on the flow rate and concentrations of effluent to be treated.

[0071] The energy demands of the proposed equipment (1) are compatible with commercially available low-power solar panels. In the event of solar power unavailability, it can also be powered by microhydroelectric turbines. These turbines can use the natural water flowing from the drain to the local stream, depending only on the height of the bottom drain in response to the stream into which it is discharged, i.e., the hydraulic head. The small-power turbine can be coupled to the inlet of the proposed treatment system, after the drain effluent collection basin.

[0072] The invention presented here can easily apply a mixture of calcium oxide and calcium peroxide directly to the generation points of effluents containing high levels of iron and manganese. It is a portable, modular, energy-sufficient, and self-regulating solution capable of adjusting to flow variations. Thus, the problem also offers a viable solution from a financial perspective, given that the cost of the equipment and its ease of installation make the technology viable. The cost of the main input and chemical reagent in the treatment process is also low. Calcium peroxide is affordable and can be used directly in the receiving surface water body due to its high environmental safety and its ability to oxygenate the environment without generating toxic byproducts.During the development of the process for this patent, an option for applying a mixture of calcium oxide and calcium peroxide emerged, replacing the automatic dosing device with CaO and CaO mixture tablets. These tablets, by slowly dissolving over time, ensure a more controlled and consistent dosage, without the need for manual adjustments or complex systems. This new system is simpler, more robust, and extremely effective in a variety of environmental and flow conditions. By eliminating the need for heavy equipment and constant maintenance, the invention proposed a more economical, portable, and self-sufficient solution, ideal for the challenging conditions of mining regions. This improvement in the dosing process brought greater efficiency to effluent treatment while maintaining sustainability and environmental safety as pillars of the system.Alternatively, the automatic doser can be replaced by perforated baskets containing calcium oxide and calcium peroxide mixture tablets (5), as shown in Figure 2, which are placed directly into the water flow of the pipeline, allowing for controlled and constant dosing of the calcium oxide and calcium peroxide mixture over time, without the need for manual adjustments or complex systems, providing a simpler and more efficient solution for treating the effluent (E) until its return or sedimentation in the streambeds (C).

[0073] Alternatively, the process can occur according to the sequence shown in Figure 2: a) The effluents and waters containing manganese, especially those from mining tailings bottom drains, are connected to the outcrop points of the contaminated waters that flow into a stream, where the calcium oxide and calcium peroxide mixture tablets are positioned in perforated baskets, which are fixed inside the stream; and b) Finally, the decontaminated water and insoluble substrates can be reincorporated into the sediment matrix of the stream (C) in an insoluble and environmentally friendly condition and (D) through the use of sedimentators or filters installed in the effluent channel to be treated.

Claims

CLAIMS 1. PROCESS FOR TREATMENT OF WATER CONTAMINATED BY MANGANESE AND IRON, characterized by the following steps: I. Reduction of the elements Iron and Manganese, through the insertion, delivery or controlled dosage of calcium peroxide directly into surface water bodies, effluents and other wastewater with concentrations of these dissolved toxic metals above the desired limits; II. Delivery, dosage and insertion of calcium peroxide into aqueous media through a powder product dosage system, in an automated and self-controlled manner by equipment consisting of a containment basin (11), driven by automatic water piping (12) and fed into the equipment (1) equipped with a powder doser (14) that feeds the chemical reagents calcium oxide and / or calcium peroxide, in an ideal calculated dosage; III. Dosage, incorporation and dissolution of calcium peroxide consisting of the direct insertion into the aqueous medium of tablets or spheres of calcium peroxide and calcium oxide arranged in permeable metal baskets, with the controlled release and dosage of the active ingredient, converting the soluble toxic metals to insoluble precipitates removed from the aqueous medium by simple gravity decantation; and IV. Conversion of dissolved metals into oxide and hydroxide substances of very low solubility, allowing them to: a) settle naturally in the stream bed; b) be removed by gravity through sedimentation tanks; c) removed by filters or membranes; and d) by other complementary physical methods such as centrifuges or similar.

2. PROCESS FOR TREATMENT OF WATER CONTAMINATED BY MANGANESE AND IRON, according to claim 1, characterized by optionally including the following step: after dosing, incorporating, dissolving and mixing the peroxide calcium and / or calcium oxide in the water or effluent, flocculants or polyelectrolytes can be added to aid precipitation, reducing the precipitation time to seconds, where the stable precipitates will settle naturally in the stream or be removed by physical systems such as sedimentators, filters or other complementary methods.

3. EQUIPMENT FOR TREATMENT OF WATER CONTAMINATED WITH MANGANESE AND IRON IN MINING EFFLUENTS, for carrying out the process of claim 1, characterized by being provided with a containment basin (11), piping (12) connected to the outlet of the basin (11), provided with an automatic water flow meter (13) of the flowmeter type or similar positioned in the piping (12); powder doser (14) of the dosing screw type or similar positioned above the piping (12); provided with flow and concentration meters (17) for determining concentrations and flows of aqueous suspensions in line positioned after the mixer; and provided with a static mixer (18) for low flows.

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