System and method for treating decorative stone by electrolysis

Abstract

The present invention relates to a system (100) and a method for treating decorative stone by means of electrolysis in an aqueous immersion solution with a low concentration of acids in order to remove impurities or contaminants, such as iron oxides. The system (100) operates by filling of compartments (120) with an aqueous solution containing acidic reagents. Decorative stone slabs are then positioned inside said compartments (120). An electrical potential difference is supplied between the anode (130) and cathode (140) terminals, promoting an electrolysis reaction to remove oxidation from said slabs.

Description

DESCRIPTIVE REPORT SYSTEM AND METHOD FOR TREATMENT OF ORNAMENTAL ROCKS BY ELECTROLYSIS FIELD OF APPLICATION

[0001] The present invention relates to a system and a method for treating ornamental rocks by means of electrolysis in an aqueous immersion with a low concentration of acids to remove impurities or contaminants, such as iron oxides.

[0002] The invention in question falls within the technical field of natural rock treatments for ornamental purposes such as granite, marble, quartzite, slate, among others. BACKGROUND OF THE TECHNIQUE

[0003] Ornamental rocks are understood to be stone materials, normally extracted by cutting them into blocks or slabs, which are used as internal and external coverings in buildings, as well as in architectural elements, decoration, and furniture. Such rocks are still commonly used in funerary art.

[0004] Examples of this type of rock are marble, granite, slate, quartzite, gneiss, as well as limestone or carbonate rocks.

[0005] Due to their intrinsically natural formation, ornamental rocks can present impurities or infiltrations. The most common are the oxidation of metals such as iron, for example. These infiltrations appear as "rust" stains embedded in the veins of the stones, making the aesthetic appearance of these rocks unattractive, which devalues ​​the product. The removal of these infiltrations, therefore, is highly desired in order to add value to the plaques and ornamental pieces.

[0006] Techniques for washing or immersing ornamental rocks in aqueous solutions with high concentrations of acids such as oxalic acid, phosphoric acid and citric acid for long periods (days, weeks and even months) are known. This technique provides satisfactory results in terms of removing iron oxides, but prolonged exposure to inadequate concentrations of acids can damage the rock and significantly impair its natural appearance. Furthermore, inadequate washing of the stone veneers (performed after the immersion bath) may not completely remove the chemicals and the material tends to change color over time.

[0007] Documents BR102014022521-8 (published on 10 / 25 / 2016), BR102016017826-6 (02 / 14 / 2018), BR102018012580-0 (01 / 07 / 2020) and BR102020015039-1 (02 / 01 / 2022) deal precisely with means of removing infiltration in ornamental rocks that require high concentrations of acids (normally above 10%) and other chemicals to obtain satisfactory results. The high The concentration of acidic products is extremely aggressive and can damage the parts if the exposure time and post-washing are inadequate. In addition, a treatment time that is too long leads to higher storage costs and energy consumption, given that it is common to use electrical resistors to increase the reaction temperature in the tanks.

[0008] Another technique widely used to correct imperfections in ornamental rocks is coloring or pigmentation using dyes. This procedure only "masks" the said imperfections and, if poorly executed, can remove the natural stone appearance of the piece.

[0009] Examples of artificial rock coloring can be seen in documents W02005019135A1 (03 / 03 / 2005) and ES2186498A1 (01 / 05 / 2003), which reveal rock pigmentation processes by means of electrolysis.

[0010] It is therefore desirable that the means of removing infiltration or oxidation be carried out in a non-aggressive aqueous solution, with a low concentration of acids (up to 10%) and that the exposure time to the solution be as short as possible. Furthermore, to maintain the natural aspects of the rock, it is necessary to avoid the use of dyes or pigments. SOLUTION PROPOSED BY THE INVENTION [ O il ] In order to mitigate or eliminate the drawbacks described above, the present invention provides a system and a method for treating ornamental rocks by means of electrolysis in an aqueous immersion with a low concentration of acids to remove impurities or contaminants, such as iron oxides.

[0012] The use of low concentrations of acids minimizes the aggressiveness of the solution on the rock. This is only possible because the removal reaction occurs in an electrochemical reactor that allows the material to undergo electrolysis. The electrolysis itself raises the temperature of the solution, increasing the reaction rate of the iron oxides in the stone plates. In this way, the time of exposure to the removal solution is minimized, reducing treatment costs.

[0013] The invention, therefore, provides for a system for treating ornamental rocks that comprises an immersion tank, internally coated with a layer of propylene. The system also comprises, inside the tank, a set of anodic and cathodic terminals distributed along the side wall and in the lower portion of said tank that facilitate the migration of ions through the solution.

[0014] The invention also discloses a method of treating ornamental rocks that comprises the steps of: immersing the plates in a tank containing an aqueous solution with a low concentration of acids; applying a difference in electrical potential between the anodic and cathodic terminals; exposure of the rock plates for a certain period to electrolysis to remove infiltrations; removal of the rock plates from the aqueous solution; washing of the parts to extract any chemical residues and drying.

[0015] The solution proposed by the invention is intended, preferably, for treatments of ornamental rocks cut into slabs, but pieces in other formats can also be treated by the technique disclosed here. OBJECTIVES OF THE INVENTION

[0016] The main objective of the invention is to promote a system and a method for treating ornamental rocks by immersing the rock slabs in an immersion tank, internally coated with a layer of propylene; in which a set of anodic and cathodic terminals, distributed along the side wall and in the lower portion of said tank, allow the removal of oxidation from said rocks.

[0017] It is also an objective of the invention to present a system and a method for treating ornamental rocks that involves an immersion bath in an aqueous solution with a low concentration of acids, in which the exposure time of the pieces to these products is as short as possible in order to mitigate any harmful effects caused by acid action.

[0018] The invention also aims to propose a system and a method for treating ornamental rocks that do not use dyes or pigments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 - Perspective view of the ornamental rock treatment system.

[0020] Figure 2 - Top view of the immersion tank of the ornamental rock treatment system.

[0021] Figure 3 - Cross-sectional view of the immersion tank of the ornamental rock treatment system. DETAILED DESCRIPTION OF THE INVENTION

[0022] Referring to figures 1 to 3, the invention describes a preferred embodiment comprising a system (100) for treating ornamental rocks by electrolysis to remove oxidation (mainly iron oxides) or infiltrations. Said system (100) comprises an immersion tank (110) intended to receive the ornamental rock slabs (not shown). Said immersion tank (110) is preferably made of masonry walls (115).

[0023] The immersion tank is capable of receiving at least one polymeric compartment (120) preferably manufactured from propylene. By way of example, the immersion tank (110) shown in Figures 1 and 2 show two compartments (120).

[0024] Inside the compartments (120), anodic (130) and cathodic (140) terminals are arranged, which are responsible for the electrochemical reaction, which occurs due to a difference in electrical potential that is applied between these terminals. The compartments (120) also receive the aqueous solution with reagent acids.

[0025] Still according to a preferred embodiment of the invention, the system (100) further comprises a control panel (150) and a control room (160) for monitoring and monitoring the electrochemical treatment.

[0026] According to a preferred embodiment, ornamental rock slabs (not shown) are positioned and aligned inside the compartments (120). Preferably, each tank (120) can receive 12 ornamental rock slabs with a thickness of 30 mm or 18 slabs with a thickness of 20 mm. By way of example, a tank (110) is 4.40 m long by 1.70 m wide and the compartments (120) have a width of around 730 mm.

[0027] As seen in Fig. 3, the compartments (120) comprise cathode (140) and anode (130) terminals. Preferably, at least one cathode terminal (140) is mounted on the side wall of each compartment (120) and at least one cathode terminal (140) is positioned at the base of each compartment (120), the same arrangement being applied in in relation to the anodic terminals (130), with at least one terminal being located at the base and another at the wall (see Fig. 3). This arrangement facilitates the migration of ions through the aqueous solution, allowing a homogeneous electrochemical reaction on all immersed plates.

[0028] The aqueous solution used in the electrochemical reaction preferably comprises a maximum concentration of acidic reagents of 10%, which is considered a low and non-aggressive quantity for the treatment of ornamental rocks, based on the acid concentration used in other known techniques.

[0029] The system (100) operates by filling the compartments (120) with the aqueous solution containing acidic reagents. The ornamental rock slabs are then positioned inside said compartments (120). The rock slabs are placed in such a way as not to come into direct contact with the cathodic (140) and anodic (130) terminals. An electrical potential difference is provided between said anodic (130) and cathodic (140) terminals, promoting the electrolysis reaction to remove oxidation from said plates. Due to the electrochemical reaction itself, in which the acid molecules are activated, the temperature of the solution preferably reaches a temperature between 80°C and 95°C. The electrolysis is applied, preferably, for a period of 24h to 36h, depending on the need and the type of rock slab. After this period, the rocks are removed from the immersion, washed and dried.

[0030] The method of treating ornamental rocks according to a preferred embodiment of the invention comprises the operation of the system (100) according to the following steps: a) filling the compartments (120) with the aqueous solution containing acidic reagents; b) immersing the ornamental rock plates inside said compartments (120); c) applying a difference in electrical potential between the anodic (130) and cathodic (140) terminals; d) maintaining the electrolysis reaction for a certain period to remove oxidation from said plates; e) extracting the plates from the immersion; f) washing to remove chemical reagents; g) drying the plates.

[0031] Those skilled in the art may appreciate that the system (100) and the method of treating ornamental rocks disclosed herein allow the removal of infiltrations of this type of material in a non-aggressive environment, and in a relatively short period of time, which minimizes any damage to the crystalline structure of the minerals.

Claims

MODIFIED CLAIMS Received by the International Secretariat on 25 FEB 2025 (25.02.2025) CLAIMS 1. Apparatus (100) for treating ornamental rocks to remove oxidation, comprising: - an immersion tank (110) intended to receive the ornamental rock slabs; - wherein the immersion tank (110) comprises at least one polymeric compartment (120); characterized by the fact that: - in which, inside the compartments (120), anodic (130) and cathodic (140) terminals responsible for the electrolysis reaction are arranged; - wherein, preferably, at least one anode terminal (130) is mounted on the side wall of each compartment (120) and at least one anode terminal (130) is positioned at the base of each compartment (120); - wherein also, preferably, at least one cathode terminal (140) is mounted on the side wall of each compartment (120) and at least one cathode terminal (140) is positioned at the base of each compartment (120).

2. Apparatus (100) according to claim 1, characterized in that the immersion tank (110) is preferably made of masonry walls (115).

3. Apparatus (100) according to claim 1, characterized in that the compartments (120) are preferably made of propylene.

4. Method of treating ornamental rocks comprising the operation of the apparatus (100) characterized by the fact that it comprises the following steps: a) filling the compartments (120) with an aqueous solution of 93% water by volume, 4% oxalic acid by volume, and 3% phosphoric acid by volume; b) immersion of the ornamental rock slabs inside the said compartments (120); MODIFIED SHEET (ARTICLE 19) c) application of a difference in electrical potential between the anode (130) and cathode (140) terminals with a current of 120 amps until the water is heated to 90°C, taking around 5 hours, then reducing the current to 62 amps; d) maintenance of the electrolysis reaction for a period of 12h to 36h to remove oxidation from the aforementioned plates; e) extraction of the plates from the immersion; f) washing with water at 45°C to remove chemical reagents; eg) drying the plates. MODIFIED SHEET (ARTICLE 19)

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