Filtering system for removing volatile organic sulfur compounds (VOSC) in indoor air

Abstract

The present disclosure relates to a filtration system for an air purification apparatus for removing volatile organic sulfur compounds (VOSCs) from indoor air at room temperature, comprising a filter element comprising particles and / or pellets made from two zinc compounds, zinc hydroxide (Zn (OH) 2) and zinc peroxide (ZnO2), and wherein the filter acts as an absorption filter that irreversibly reacts with volatile organic sulfur compounds that may contaminate the indoor air, the volatile organosulfur compounds include vapors of liquid organic mercaptans (RSH), vapors of liquid dialkyl oligosulfides (RS-SR and RS-S-SR, including those present in allium species), and vapors of solvent carbon disulfide (CS2). The present disclosure also relates to a method of removing these volatile organosulfur compounds from indoor air in which a controlled indoor air flow is passed through a filtration system comprising particles or pellets prepared from zinc hydroxide (Zn (OH) 2) and zinc peroxide (ZnO2), and wherein the volatile organosulfur compound reacts irreversibly with the hydroxide and peroxide ions of the aggregate (pellets or granules) to produce solid harmless zinc salts to be trapped in the filtration system.

Description

Technical Field

[0001] This disclosure relates to a filtration system for removing vapors of certain groups of organic sulfur compounds from indoor air, specifically to the removal of vapors of liquid thiols (R-SH), organic oligosulfides (e.g., RSSR and RSSSR, also known as dialkyl polysulfides), and solvent carbon disulfide (CS2, S=C=S), and to a method for removing such compounds from indoor air. Background Technology

[0002] Volatile sulfur compounds (VSCs) are recognized as harmful, toxic, and / or foul-smelling compounds. They consist of a large number of sulfur-containing organic molecules, namely, dozens of volatile liquids, which may be referred to as volatile sulfur organic compounds or volatile organic sulfur compounds (VOSCs) to distinguish them from all other volatile organic compounds (i.e., so-called VOCs, which contain thousands of gases and liquids belonging to all categories of organic molecules).

[0003] Some sulfur compounds, whether inorganic or organic, are gases at room temperature and atmospheric pressure, such as hydrogen sulfide (H2S), methanethiol (CH3SH), carbonyl sulfide (COS), and sulfur dioxide (SO2). These gases are not treated in this application because removal technologies for them have already been established in the petroleum industry.

[0004] This application is limited to removing vapors of certain groups of organic sulfur compounds (VOSCs) from indoor air. Specific treatment methods for these compounds have not yet been disclosed. A) Dozens of liquid organothiols (RSHs), especially those that are highly volatile and have a very unpleasant odor. Low molecular weight liquid ethanethiol (thioethanol, CH3CH2SH, "malodorous gas," smells like rotten cabbage) and allyl thiols (found in garlic and many other Allium species) Allium (Ethyl mercaptan) is toxic at high concentrations. For example, ethanethiol inhibits the central nervous system and affects the respiratory center, leading to respiratory paralysis and death. Phenylenol (PhSH, LC50) is also toxic in rats. 50 Alkyl mercaptan (33 ppm) and 1-dodecyl mercaptan are also toxic at high concentrations. According to the National Institutes of Health (NIH), even less volatile alkyl mercaptans, such as 1-octadecyl mercaptan, "can be harmful by ingestion, inhalation or skin contact; they are eye, skin and respiratory irritants."

[0005] Many liquid organosulfur compounds (RS-R', also known as thioethers) have a foul odor and exhibit toxicity through inhalation. However, these compounds are not addressed in this application because the oxidation of certain members of this group (such as mustard gas (ClCH2CH2-S-CH2CH2Cl) and diethyl sulfide (CH3CH2-S-CH2CH3)) has been the subject of much research since its use as a toxic gas during World War I, and because their oxidation does not produce solid zinc salts, but rather sulfoxides (R-SO-R) and sulfones (R-SO2-R).

[0006] B) Organic disulfides / trisulfides / tetrasulfides (i.e., organic oligosulfides, commonly referred to as dialkyl polysulfides) also have a foul odor, either a strong garlic-like smell or a fecal stench. Diallyl disulfide (CH2=CHCH2-SS-CH2CH=CH2) is a typical component of garlic and has some medicinal properties (but may cause allergic contact dermatitis; its LD50 in rats is low). 50 =260 mg / kg), while dipropyl disulfide (CH3CH2CH2-SS-CH2CH2CH3) is abundant in onions; allyl propyl disulfide and the aforementioned dipropyl disulfide (onion) are toxic to dogs and cats. In the petroleum industry, a mixture of dialkyl disulfides and trisulfides is called disulfide oil (DSO). Although RS-R', RSS-R', RSSS-R', etc. (for dimethyl derivatives, inhalation, LD50 in rats) 50 =50 g / m 3 The odor (8h) is moderately toxic, but even a slight concentration in indoor air such as industrial kitchens, hotels, hospital canteens, and public toilets is clearly contraindicated. Houses and buildings near food processing industries that handle onions, garlic, scallions, wild leeks (ramps), etc., should also be kept away from these odors.

[0007] Garlic (Allium sativa) contains a significant amount of VOSCs. In addition to the aforementioned disulfides (primarily diallyl disulfides), other cyclic sulfides and disulfides have been characterized, including thiophene derivatives, whose odor is unpleasant at industrial levels. On the other hand, when garlic cloves are chopped, an enzymatic process generates a specific disulfide oxide, allicin (S-allyl-2-propene thiosulfinate, CH2=CHCH2-S(=O)-S-CH2CH=CH2), and more complex sulfoxides, such as ajoene isomers (these are beneficial and non-volatile, and therefore not discussed here).

[0008] Onions (Allium cepa) also contain significant amounts of volatile dialkyl disulfides and trisulfides, fortunately with low to moderate toxicity to humans. The pungent flavor is primarily attributed to these disulfides, many of which differ from those found in garlic. Furthermore, when the cells are chopped, another enzymatic reaction is triggered, releasing a well-known lachrymatory agent (the Z-isomer of propanthaldehyde S-oxide, CH3CH2CH=S=O). This hydrolyzes in our mucous membranes, producing propanthaldehyde and a low-valent sulfur intermediate, possibly also some propanesulfinic acid. These compounds cause tearing as a defensive reaction of the eyes. Fortunately, this volatile byproduct is water-soluble and decomposes with water, but the food processing industry doesn't cut hundreds of onions under running water. Appropriate filters would be useful to remove this particular sulfoxide from the manufacturing plant and surrounding buildings.

[0009] C) Carbon disulfide (CS2, S=C=S) is a neurotoxic solvent and reagent with a sweet odor similar to chloroform. It is used in the manufacture of perfumes, cellophane, rayon, and some types of rubber, as well as as a soil fumigant. As a solvent, it was banned in laboratories decades ago due to its hepatotoxicity and flammability. All government agencies have mandated a threshold limit of 1 ppm for an 8-hour shift. At 6 ppm, increased mortality has been reported. LD50 has been reported. 50 The value is 3.2 g / kg (rat). Trithiocarbonate or thiocarbonate (H₂CS₃, HS-CS-SH) is also a low-boiling-point liquid that decomposes to produce carbon disulfide (and H₂S). Xanthates or dithiocarbonate derivatives have the general formula ROC(=S)S. - M + ROC(=S)SH and ROC(=S)SR' are commonly used as pesticides or in mining processes, as well as dithiocarbamates or dithiocarbamate derivatives, R2NC(=S)S - M + R2NC(=S)SH, R2NC(=S)SR', etc., are used for rubber vulcanization. Their thermal decomposition and / or hydrolysis readily produce CS2, which may be included in this group, even though many of them are solids or low vapor pressure liquids (but are still toxic).

[0010] There are no specific patents relating to the removal of liquid VOSC vapors from indoor air at room temperature, including Group A (liquid thiols), Group B (organic disulfides, organic trisulfides, etc.), and Group C (solvent carbon disulfide CS2, trithiocarbonate, and vapors of the aforementioned precursors). Furthermore, there are no specific patents relating to the simultaneous elimination of all three groups of VOSCs.

[0011] In other words, several reagents can capture or remove gases such as H2S / CH3SH, COS, and SO2 from the petroleum and coal industries, from wastewater, or from chemical and pharmaceutical processes that produce large quantities of these byproducts or their precursors. The most common is zinc oxide (ZnO). The reaction of ZnO with H2S to form ZnS has been known since the early days of chemistry. Furthermore, many oxidizing agents can convert H2S to sulfur (S8) and / or higher valence sulfur, even sulfate ions, and convert SO2 / sulfite to SO3 / sulfate. Therefore, many patents cover, and some still cover, these possibilities and related reactions, primarily for the removal of these gases in industrial environments, as described above: US2016 / 0250370 discloses a deodorant made of hydrophobic zeolite + ZnO (an “adsorbent” for H2S and CH3SH, as stated in the original text) + MnO2 (a catalyst, also applicable to “removal of sulfides, as stated in the original text)).

[0012] WO2015 / 069357 describes a gas mask with two impregnated carbon filters. The first filter contains a metal / TEDA (triethylenediamine), and the second filter contains Zr(OH)4 and zinc (hydrogen) oxide to capture several toxic inorganic gases, but only NO was evaluated. x NH3 and SO2. As is known, "zirconium hydroxide is a reactive matrix for removing sulfur dioxide." Furthermore, "the inclusion of zinc (hydrogen) oxides in the particles of the second filter media may help filter HCN, (CN)2, and NH3 from the airflow."

[0013] US2015 / 0306536 specifies the capture of SO2, H2S, HCHO, NH3, HCN, ClCN, COCl2, cyclohexane (as stated in the original text), NO2, and PH3, wherein, in addition to a first activated carbon-based filter (see above), there is a second filter containing Zr(OH)4 (zirconium hydroxide) and zinc oxide or zinc hydroxide plus one or more cobalt compounds. Organosulfur compounds were not investigated. No claims concerning VOSCs are included.

[0014] US2018 / 0291284, titled "Particulates for the Removal of H2S and / or Thiols," describes the removal of particles from an aqueous suspension of silica or alumina using Fe... 2+ or Zn 2+ Salt immersion. The invention description mentions all commercially available Zn-containing... 2+Salts or compounds (up to 21, including zinc hydroxide and zinc peroxide). They are treated with an alkaline aqueous solution, so the active species is always zinc hydroxide (with one possible exception, but this is not mentioned). Terms such as “sulfide-removed nanoparticles” (but not “microparticles” in the title) and “sulfide-reactive metals” are used incorrectly multiple times because the author is only referring to the capture of hydrogen sulfide (H2S): no real organosulfur compounds (dialkyl sulfides) are treated; thiols are not included in any of the examples or claims. This aqueous suspension is intended for use in petroleum extraction processes, wastewater treatment processes, and similar activities (not as a device for purifying indoor air).

[0015] US1989 / 4888157 has a very general title, "Removal of Sulfur Compounds," but only claims protection for the removal of carbonyl sulfide (COS), hydrogen sulfide (H2S), and thiols (in this case, without any examples, chemical formulas, or comments) from aggregates of CuO / ZnO / Al2O3 ignited at 900ºC, wherein "the content of CuO and ZnO present in the ignited aggregates is at least 70% by weight." Claim 9 states that "the aggregates contain at least one compound selected from the group consisting of ZnO, Zn(OH)2, ZnCO3, and basic zinc carbonate," but upon heating (even at temperatures far below 900ºC), the latter three compounds decompose into ZnO. In other words, the aggregates can only contain ZnO.

[0016] CN2003 / 1415402 relates to the use of ZnO-TiO2-Al2O3 to capture H2S. On page 6 (English translation), ZnO·2CO2·4H2O is reported, which clearly refers to the hydrated form of zinc bicarbonate, namely Zn(HCO3)2·3H2O.

[0017] CN2014 / 103769038 (as well as 041 and 044) discloses a gas desulfurization adsorbent (as stated in the original text) and its preparation and application, wherein the adsorbent is a mixture of ZnO, SiO2, and "oxyacid salts of molybdenum carbide and calcium", suitable for removing H2S, sulfur oxides and "sulfides" (as stated in the original text, although this may be a translation issue) from natural gas, oilfield gas, flue gas and exhaust gas.

[0018] US2010 / 0180770 addresses the adsorption of hydrogen sulfide gas (also known as H2S) and other gases, including but not limited to CO2. Activated carbon combined with granular MgO, TiO2, and ZnO forms the adsorption material.

[0019] US2022 / 0161180 discloses an industrial air purifier. Claim 11 states that its device comprises metal oxides, claim 17 relates to a water spray that generates a wastewater stream, and claim 20 states that the pollutants include particulate matter, CO, H2S, and nitrogen oxides.

[0020] US2012 / 8333824 discloses an "adsorbent comprising activated carbon (AC) impregnated with a Zn compound and a molybdenum compound, and a gas filter element containing the adsorbent", primarily for binding HCN and SO2. The claimed efficacy is as follows: (1) activated carbon (AC) impregnated with 0.5-15 wt% molybdate, consisting of at least one Zn compound (in the form of ZnCO3 and zinc halide); (3) the zinc compound also in the form of hydroxide and / or oxo or polyoxo anion of molybdate; (7) dissolved zinc carbonate, NH4Cl, (NH4)2CO3 and sodium molybdate; (10) Zn as an oxide, carbonate, halide, hydroxide, sulfate and / or oxo or polyoxo anion of molybdate, for simultaneously filtering HCN, SO2 and H2S from the environment.

[0021] WO2021 / 091076 discloses a catalyst for pretreatment desulfurization comprising (a) at least one oxide; (b) at least one metal; and (c) at least one selected liquid composition. The catalyst is supplied to marine fuel oil for the purpose of adsorbing sulfur oxides present therein.

[0022] US1993 / 5248489 discloses a method for removing H2S from a fluid stream by contacting the fluid stream with an absorbent composition consisting mainly of ZnO and silicon dioxide (SiO2) under suitable conditions.

[0023] EP1990 / 0401789 discloses a method for removing hydrogen sulfide from a fluid stream by contacting the fluid stream with an absorbent composition consisting mainly of ZnO and silica under suitable conditions, and preferably with a metal oxide promoter (NiO).

[0024] US2008 / 0271602 discloses an adsorbent composition comprising a porous SiO2 support impregnated with a mixture comprising ZnO and copper, which can be used in systems and methods for removing sulfur compounds (unspecified, presumably H2S) from a gas stream. Furthermore, the patent application discloses a filter material comprising the adsorbent composition and a method for removing sulfur compounds from a stream by passing the stream through the adsorbent composition at 100-900ºC. Oxidants such as ozone (O3) or hydrogen peroxide (H2O2) can be used to remove sulfur compounds “adsorbed” onto the adsorbent.

[0025] WO2009 / 064453 describes methods and apparatus for reducing or eliminating malodors. Specifically, it provides a method for reducing indoor air malodors using vaporized hydrogen peroxide (H2O2), which is generated by evaporation of a pH-neutral to weakly acidic aqueous liquid composition or by sublimation of a solid composition containing at least one pH-neutral to weakly acidic hydrogen peroxide compound. The vaporized hydrogen peroxide (VPHP) reacts in air containing malodorous compounds with a medium coated with at least one transition metal element or compound. The combination of vaporized hydrogen peroxide and the transition metal compound as an oxidation catalyst provides an increase in the oxidizing efficiency of malodorous molecules.

[0026] Zinc hydroxide (Zn(OH)₂) is commercially available. It is a moderately strong base with well-known amphoteric properties. The uses and advantages of this compound for the removal of organosulfur compounds are almost entirely disclosed in the prior art.

[0027] One patent (ICI, ZA1989 / 8804251, entitled "Removal of Sulfur Compounds from Gas Stream") describes a close mixture of oxides, hydroxides, carbonates, and / or basic carbonates of Cu, Zn, and other elements for the removal of H2S and COS at 100ºC. However, these mixtures have been previously calcined, so the agglomerates are mixtures of oxides (CuO / ZnO / Al2O3), meaning one of the active components is ZnO rather than Zn(OH)2.

[0028] Another patent (US2002 / 0102229, Products and methods for controlling odor) reports a mixture of oxides / hydroxides / peroxides / carbonates of H2O2, Zn / Fe / Ca / Mg, etc., and metal nitrates, "for substantially eliminating the malodorous odor of H2S", but does not study general organosulfur compounds (or especially A / B / C type VOSCs).

[0029] Regarding the removal or capture of CS2, one paper and one patent are somewhat relevant to this topic. The paper, titled "Removal of Carbon Disulfide from Gasoline Fractions from Zinc-Carbon Composites Synthesized by Microwave-Assisted Homogeneous Precipitation" (Environm. Sci. Pollution Res. 2023, 30, 82014-82030), involves loading the product of heating zinc nitrate with urea onto a carbon surface to generate ZnO, Zn(OH)2, and 2ZnCO3·3Zn(OH)2 (i.e., basic zinc carbonate). The results show that "ZC (zinc-carbonate)" has the highest CS2 "adsorption" capacity.

[0030] Patent WO2018 / 1841158 (CN2017 / 079507W) describes a method for preparing a composite material with nitrogen-doped graphene / zinc hydroxide / hollow sulfur particles, involving many complex steps (adding S to CS2, adding Ni powder, treating with FeCl3, adding the precipitate to a solution containing ZnCl2, urea, and surfactants, etc.), "aimed at improving electrochemical performance," but clearly not at removing VOSCs.

[0031] Zinc peroxide (ZnO2) is commercially available and has enjoyed some medical and pyrotechnic applications. However, no patents describe its use for capturing or removing organosulfur compounds, even though the agent is far less hazardous than most metal peroxides. No prior art documents address the removal or capture of thiols (A), organic disulfides / trisulfides (B), and / or carbon disulfide and its precursors (C). There is a patent (CN2018 / 108970353, titled "Comprehensive Desulfurization and 'Denitrification' Method for Catalytic Flue Gas and Ammonia-Containing Acid Gases") that explains how to remove H2S from catalytic flue gas using Fe2O3 or ZnO, as explicitly indicated in the claims; ZnO2 is only mentioned in the invention description, which is clearly a machine translation error. In any case, there is no conflict between this patent and this patent application, which does not relate to the removal of gaseous and inorganic sulfur compounds such as H2S.

[0032] Only one paper ( Appl. Catal. B: Environ. 2018, 226, 429-440) reported the reaction of ZnO2 with diethyl sulfide (oxidation) and 2-chloroethyl ethyl sulfide (Cl replaced by OH), based on X-ray, SEM, Raman spectroscopy and other techniques. As noted, this patent application does not deal with these or any other dialkyl sulfides (also known as thioethers) of the general formula RS-R'. It is known from early organic chemistry that oxidation of dialkyl sulfides with peroxides or peroxide salts yields sulfoxides and sulfones, which are generally stable high-boiling liquids. In contrast, the objective of this application is to capture VOSCs that, upon contact with Zn(OH)2-ZnO2, primarily provide white salts such as zinc thiolates and / or zinc sulfonate or zinc sulfate.

[0033] To the applicant's knowledge, mixtures or combinations of these two compounds, Zn(OH)₂ and ZnO₂, have never been reported as reagents for organic synthesis. Aggregates or nanoparticles of zinc cations with hydroxide and peroxide anions as ligands have also never been reported. Clearly, this combination has never been used as a reagent for the removal of VOSCs, particularly for the removal of Groups A, B, and C contaminants disclosed in this application.

[0034] In summary, existing technologies do not address filters suitable for removing liquid thiols (part A or group A), liquid organic disulfides / trisulfides (organic oligosulfides, or general dialkyl polysulfides, belonging to group B or type B), and solvent CS2 (and its precursors, type C) vapors from indoor air (i.e., at ambient or room temperature, not from hot crude oil). Any simple filter capable of completely and irreversibly capturing or trapping these VOSC group contaminants from indoor air at room temperature, and simultaneously capturing or trapping all three types of samples, would be socially useful by converting them all into harmless, non-volatile, white zinc salts. This is the objective of this application. Summary of the Invention

[0035] To address one or more of the aforementioned problems, one aspect of this disclosure provides a filtration system for an air purification device for removing volatile organic sulfur compounds (VOSCs) from indoor air at room temperature. The filtration system includes a filter element comprising particles and / or pellets made of two zinc compounds, zinc hydroxide (Zn(OH)₂) and zinc peroxide (ZnO₂), and wherein the filter functions as an absorption filter that irreversibly reacts with volatile organic sulfur compounds that may pollute indoor air.

[0036] The two zinc compounds are commercially available crystalline solids and are completely compatible.

[0037] The combination of these two Zn reagents has not been previously reported in chemical literature or prior patents. As the inventors have observed through experiments, they exhibit a synergistic effect when combined in pellet or granule form, in addition to the practical advantages of using pellets or granules rather than powder.

[0038] There are very few harmless and non-toxic alkaline reagents that can be safely included in filters and designed to operate at ambient temperatures in rooms, bathrooms, apartments, hotels, hospitals, airplanes, cinemas, schools, or lecture halls (to name just a few).

[0039] The two zinc compounds are preferably mixed in water or alcohol (preferably ethanol) to form a suspension, which is then converted into white pellets or granules. The suspension (slurry or gel) is extruded and dried (e.g., in air or in a glass desiccator) to obtain a dried material. This porous dried material is then easily cut into small pieces. The resulting granules and / or pellets resemble activated carbon pellets but are white. The diameter of the granules can be 3 ± 1 mm (about 3 mm), and the diameter of the pellets can be up to 5 mm, with a length of 5 ± 1 mm (about 5 mm).

[0040] No commercially available coagulants or chemical binders, such as povidone, microcrystalline cellulose, or calcium phosphate, need to be added. In fact, pellets prepared from aqueous or alcoholic suspensions are more pressure-resistant (less prone to breakage and pulverization) than pellets prepared using these chemical binders, suspensions in organic solvents, or suspensions in hydrogen peroxide solutions.

[0041] The filtration system according to this disclosure comprises zinc hydroxide and zinc peroxide in a weight ratio of 1:9 to 9:1, depending on the primary contaminants expected to be present in the house, hospital, school, airplane, or auditorium. As explained below, for general cases, as described in the experimental section, a w / w ratio of 1:2 is preferred.

[0042] The filter cartridge in the filtration system disclosed herein can also be placed between two nonwoven filters. The filtration system may also include a final EPA or HEPA filter.

[0043] Another aspect of this disclosure relates to a method for removing volatile organic sulfur compounds (VOCs) from indoor air, wherein a controlled airflow is passed through a filtration system comprising particles or pellets of a mixture / combination of zinc hydroxide (Zn(OH)₂) and zinc peroxide (ZnO₂), and wherein the VOCs undergo an irreversible reaction with the zinc hydroxide (peroxide aggregates). In other words, the VOCs react with hydroxide and / or peroxide anions in the aggregates and are captured in the filtration system as harmless, white, non-volatile zinc salts.

[0044] The volatile organic sulfur compounds (VOSCs) removed in the disclosed method are preferably vapors of liquid organic sulfur compounds belonging to type AC / group A. Specifically, but not limitingly, liquid organic thiols (type A or group A) can be aliphatic thiols, such as ethanethiol and 1-butanethiol, and aromatic thiols, such as thiophenol.

[0045] Specifically, but not limitingly, the organic oligosulfides (Group B) can be aliphatic disulfides (RSSRs), such as dimethyl disulfide (CH3-SS-CH3) and dimethyl trisulfide (CH3-SSS-CH3). Characteristic derivatives found in Allium species, such as diallyl disulfide and dipropyl disulfide (and the onion lachrymatory factor derived from the latter), in addition to oxidized derivatives, such as thiosulfinates (R-SO-SR), have also been studied.

[0046] Specifically, a comprehensive and detailed study has been conducted on solvent carbon disulfide (S=C=S), a key representative of type C or group C, which includes the aforementioned precursors, such as trithiocarbonate (HS-CS-SH) and its derivatives, as well as volatile xanthates.

[0047] The mixture of these three components has also been studied.

[0048] In the methods disclosed herein, the controlled airflow through the filtration system is preferably at room temperature. Attached Figure Description

[0049] The features and advantages of the filtering system disclosed herein can be better understood with the aid of the accompanying drawings, which should be viewed in an illustrative and non-limiting manner.

[0050] Figure 1 The diagram shows the change in the concentration of the indicated thiols over time when a continuous stream of contaminated air passes through a separate glass column containing 12.0 g of potential absorbent: Zn(OH)₂-ZnO₂ (1:2 w / w) pellets; Zn(OH)₂ powder; ZnO₂ powder; and ZnO powder. Illustrations of ungranulated Zn(OH)₂ and ZnO₂ powders produced in 1:2 w / w and 1:1 w / w mixtures are also shown (not included for simplicity). Figure 1 (The middle value) has an intermediate value between Zn(OH)2 and ZnO2, as expected.

[0051] Figure 2 The diagram shows the changes in concentrations of the indicated organic disulfides and dimethyl trisulfides when a continuous stream of contaminated air passes through a separate glass column containing 12.0 g of potential absorbent: Zn(OH)₂-ZnO₂ (1:2 w / w) pellets; Zn(OH)₂ powder; ZnO₂ powder; and ZnO powder. Illustrations of the production from ungranulated Zn(OH)₂ and ZnO₂ powders in 1:2 w / w and 1:1 w / w mixtures are also shown (not included). Figure 2 (The value of ZnO2) clearly has an intermediate value between Zn(OH)2 and ZnO2.

[0052] Figure 3 The changes in concentrations of commercially available allicin (CH2=CHCH2-SO-S-CH2CH=CH2), onion vapor, and garlic vapor are shown when air flows through these materials and then through separate glass columns containing 12.0 g of potential absorbent: Zn(OH)2-ZnO2 (1:2 w / w) pellets; Zn(OH)2 powder; ZnO2 powder; and ZnO powder. It was difficult to generate airflows with volatile organic compound (TVOC) concentrations higher than 4.12 ppm (from chopped onion) and 2.33 ppm (from chopped garlic).

[0053] Figure 4The concentrations of carbon disulfide (CS2) vapor are shown when a continuous stream of air contaminated with this solvent passes through separate glass columns containing 12.0 g of potential absorbent, as illustrated in the preceding figures: Zn(OH)2-ZnO2 (1:2 w / w) pellets; Zn(OH)2 powder; ZnO2 powder; and ZnO powder. CS2 appears to be more sensitive to the oxidation of peroxides such as ZnO2 than to the moderately basic characteristics of Zn(OH)2. Considering the lower ZnO2 content in the pellets (first column, 33% w / w) compared to the third column (50% w / w, since, as indicated, commercially available ZnO2 is a 1:1 mixture of ZnO2 and ZnO), and their significantly smaller surface area, the pellets are remarkably efficient.

[0054] Figure 5 The figure shows the change over time in the total concentration of the volatile organic sulfur compound mixture at the column outlet when an air stream contaminated with a mixture of 2 ppm 1-butanethiol (representing Group A), 2 ppm dimethyl disulfide (Group B or Type B), and 2 ppm carbon disulfide (Group C) is continuously introduced into four different glass columns (each containing 12.0 g of the same absorbent as in the previous figure).

[0055] Figure 6 Blank experiments were shown using empty columns and columns filled with SiO2 (standard laboratory silica gel) to ensure that air pressure drop was irrelevant (i.e., the flow rate was experimentally reduced from 3.0 L / min to 2.5 L / min when air passed through a column filled with zinc compound pellets). When the column was filled with commercially available powdered activated carbon (third column) or activated carbon pellets (fourth column), the contaminants were partially adsorbed (i.e., physically / temporarily / partially retained or adsorbed, but not chemically absorbed, see main text).

[0056] Figure 7 The left side shows the filter element (schematic diagram). The middle shows the stable, white, porous pellets (top) and granules (bottom) prepared as described above. The right side shows the filter at 20 μm. 3 A turbine extractor used in containers contaminated with a vapor mixture of 1-butanethiol, dimethyl disulfide, and CS2. This turbine extractor forces the contaminated air through a filter. A final EPA or HEPA filter may be included to remove any micron or nanoparticles (PM10 / PM0.1). Detailed Implementation

[0057] Unless otherwise stated, all percentages relating to the content of a component or group of components in this disclosure refer to weight percentages or weight ratios relative to the total weight of the composition.

[0058] A filtration system for removing certain volatile organic sulfur compounds (referred to herein as VOSCs to distinguish them from the large amounts of volatile organic compounds (VOCs) that do not contain sulfur atoms) from indoor air is disclosed, comprising: vapors of liquid thiols (Group A); vapors of organic disulfides / trisulfides (organic oligosulfides, also commonly referred to as organic polysulfides or dialkyl polysulfides), and oxidized derivatives (some of which are found in Allium species) (Group B); and vapors of CS2 and some precursors (Group C).

[0059] The filtration system includes a filter element, preferably a plastic filter element, preferably in the form of a hexagonal honeycomb, cylindrical pore, square pore or similar pore, which serves as a container in which chemical components that chemically absorb (and irreversibly react with) these vapors are added.

[0060] These toxic and / or malodorous compounds are captured by a layer of a mixture or combination of commercially available, non-toxic, chemically compatible zinc compounds (i.e., zinc hydroxide Zn(OH)2 and zinc peroxide ZnO2) that have not been previously reported to the applicant. The aqueous or ethanol suspension of this mixture (which can be considered as an aggregate of zinc cations with hydroxide and peroxide anions as ligands) is ultimately transformed into porous cylinders that can be easily cut into granules or pellets.

[0061] As described above, the system disclosed herein is capable of removing multiple groups of volatile liquids, namely organosulfur compounds or VOCs, from indoor air, including: (A) dozens of liquid thiols; (B) dialkyl disulfides / trisulfides / tetrasulfides, and S-oxides (thiosulfinates) of diallyl disulfide, dipropyl disulfide, and thiopropionaldehyde (the first S-oxide is a natural product of garlic, and the other two compounds are found in onions); and (C) solvent CS2 (S=C=S) and some precursors such as HS-CS-SH and RO-CS-SH. It should be remembered that in the background art, these contaminants have been classified as Type A, Type B, and Type C VOCs, respectively.

[0062] The combination of zinc compounds Zn(OH)₂ and ZnO₂ (in granular or pellet form) exhibits a synergistic effect in VOSC removal compared to using each compound alone. Some VOSCs (thiols, RSH, Group A) more readily form stable and insoluble zinc thiolate Zn(SR)₂, and / or only generate the RS-Zn-OH intermediate, but these primary zinc thiolates and / or intermediates can subsequently be oxidized to organic disulfides more rapidly (as observed in independent experiments in standard reaction flasks, than their respective thiols). These primary or initial oxidation products are then further oxidized, as with the organic disulfides discussed in the following paragraphs.

[0063] Type B VOSCs, such as RSSR and RSSSR, are not acidic but are readily oxidized to thiosulfinates (R-SO-SR), and further to thiosulfinates (R-SO2-SR), etc. These products are more polar than the starting compounds and therefore can react with hydroxide anions in the pellets (in other words, with Zn). x (OH) y (O2) z OH - The ligands interact strongly. Therefore, thiosulfinates, thiosulfonates, and related oxidation intermediates can be more readily retained by the absorbent mixture. Furthermore, based on the known reactivity of thiosulfinates and thiosulfonates, these oxidation derivatives can be cleaved by the hydroxide anions of Zn(OH)₂ and / or the aforementioned aggregates. For example, the reaction of thiosulfinates with hydroxide anions can slowly generate zinc sulfinates and zinc thiolates (which are immediately oxidized by peroxide anions), while the reaction of thiosulfonates with these hydroxide anions can rapidly generate zinc sulfonates and zinc thiolates; the latter are oxidized to disulfides, then to thiosulfinates, and more slowly to thiosulfonates, which are readily and rapidly cleaved.

[0064] In this regard, the inventors have determined that the pH value of the suspension of pulverized Zn(OH)2-ZnO2 pellets in distilled water is 8.6.

[0065] Therefore, R-SH (Group A VOSC) and RSSR (Group B VOSC) will eventually be converted into white, harmless zinc sulfonate. In the case of dialkyl trisulfides (RSSSR) and dialkyl tetrasulfides (RSSSSR), ZnSO4 can also be additionally generated through the oxidation of non-terminal S atoms (and the breaking of the S-SO2-S bond).

[0066] Finally, pellets and granules made from Zn(OH)₂ and ZnO₂ also improved the removal of the toxic vapors of the solvent CS₂ (carbon disulfide, S=C=S) and its precursors (Group C VOSCs); these precursors first release H₂S, which is then captured as ZnS and subsequently oxidized. In reality, Zn(OH)₂ facilitates the hydrolysis of S=C=S (formally producing CO₂ and 2H₂S, but actually producing ZnCO₃ and 2ZnS), while ZnO₂, like most peroxides, may at first glance produce COS (carbonyl sulfide, an easily hydrolyzable gas), harmless molecular sulfur, and sulfur dioxide. In other words, the hydroxyl groups of the aggregates (pellets or granules) and the peroxyligands of these aggregates appear to synergistically decompose CS₂. Figure 4It is inferred that the reaction of CS2 with ZnO2 is faster than that with Zn(OH)2. Since the sensor at the end of the pellet-filled column never detected CO2 or SO2, it is speculated that these gases were captured as ZnCO3 and ZnSO3, respectively; the latter, namely zinc sulfite, is expected to eventually be oxidized to zinc sulfate ZnSO4.

[0067] The synergistic effect of the presence of both Zn(OH)2 and ZnO2 (partly in the form of aggregates containing both hydroxide and peroxide anions as ligands) will be discussed in the experimental results section below.

[0068] In this disclosure, Zn(OH)₂ and ZnO₂ can be mixed at a 1:1 w / w ratio, which seems close to a molar ratio. However, in practice, a 1:2 ratio is recommended if different types of VOSCs are present in the indoor environment, while noting that commercially available ZnO₂ samples may contain ZnO. However, if the primary pollutants in buildings and industrial environments are caused by thiols or any acidic pollutants, the 1:2 ratio can be modified to a maximum of 9:1 w / w; if the primary pollutants are primarily removed by oxidation (i.e., if the primary pollutants do not contain acidic protons), the ratio can be modified to a maximum of 1:9 w / w.

[0069] Both of these zinc reagents are commercially available, colorless, and non-toxic solid products (in fact, Zn...). 2+ Zinc is essential for the normal development of all cells, and is therefore considered an essential biological element for human health. Through reaction with thiols, some of the contaminants described herein are readily converted into white, solid zinc thiolates, which are non-toxic and non-volatile. This is a significant advantage of using Zn(OH)₂ instead of other bases, including other metal hydroxides. The aforementioned zinc thiolates are subsequently oxidized to zinc disulfide, zinc thiosulfinate, and zinc thiosulfonate, which can be decomposed into zinc sulfonate and zinc thiolates, which can then be oxidized again.

[0070] diallyl disulfide, other disulfides and trisulfides, and garlic ( Allium sativa The thiosulfinates (disulfides S-oxides) in the zinc salt are oxidized by ZnO2, followed by cleavage by Zn(OH)2 (thiosulfinates cleave slowly, thiosulfinates cleave rapidly), and the thiolate fragments are subsequently oxidized and cleaved, and so on. In other words, these compounds are expected to react with aggregates containing hydroxide and peroxide anions to ultimately form zinc salts. Similarly, dipropyl disulfide and onion (… Allium cepaOther disulfides in the onion are oxidized and then cleaved, while thiopropionaldehyde S-oxide (the lachrymatory factor in onions) is hydrolyzed into propionaldehyde and low-valence sulfuric acid, and may be partially converted into non-volatile zinc propanesulfonate and oxidized to its propanesulfonate. Other common volatile byproducts present in Allium species, namely the well-known relatively low molecular weight aldehydes and carboxylic acids, will be chemically absorbed due to the oxidizing and alkaline properties of the absorbent material, respectively.

[0071] Carbon disulfide (CS2) is likely oxidized to COS (which subsequently undergoes its own hydrolysis and oxidation pathway) and SO2, with SO2 being converted to SO3. Both of these sulfur oxides are obviously removed by the absorbent material. Some CS2 may also react with OH-. - The reaction produces COS and HS. - All of these reactions are well-known, therefore no protection is sought here.

[0072] In several cases, the synergistic effect produced by using the unprecedented Zn(OH)2-ZnO2 combination is significant, as shown in the figure below.

[0073] Regarding ZnO2, it must be remembered that it is a peroxide, therefore skin and eye contact, as well as inhalation or ingestion, should be avoided, and due to its oxidizing properties, it may react with flammable materials. However, as mentioned above, it is less toxic and hazardous than most metal peroxides and is more stable than most peroxyates at pH > 7. Commercially available zinc peroxide is a pure compound containing 50% ZnO (approximately a 1:1 w / w ZnO2 / ZnO mixture). This reduces the oxidizing power of the peroxide, but also reduces its hazard relative to most alternative peroxides (because commercially available ZnO2 samples are not hazardous at room temperature). When ZnO2 is used as an oxidant, it obviously converts to ZnO.

[0074] In summary, the inventors have unexpectedly discovered that combining the moderate alkalinity of Zn(OH)2 (as opposed to the general tendency of R-SH and Zn ions to form insoluble zinc thiolates) with the oxidizing power of ZnO2 allows for the simultaneous capture and removal of different types of volatile organic sulfur compounds (VOSCs) as noted throughout this application. Furthermore, this mixture is more effective than either of the individual reagents alone, and far more effective than ZnO, a reagent commonly used in the petrochemical and coal industries.

[0075] The air filtration system preferably consists of a honeycomb filter cartridge or box. This container has a 2-4 cm high filter cartridge containing two breathable, opposing non-woven or EPA filters as mesh or screens to retain all absorbent within the cartridge through which indoor air flows. It is recommended to use an initial non-woven or EPA mesh / screen, followed by a final EPA 12 or HEPA 13 filter.

[0076] Finally, the presence of Zn(OH)2 in the absorbent material has the added advantage of indirect application. It also clearly helps to capture / absorb gaseous hydrogen halides, hydrogen cyanide (HCN), and azidoic acid (HN3), as well as volatile carboxylic acids with pungent odors, such as formic acid, acetic acid, propionic acid (propionic acid), including hexanoic acid (also known as caproic acid, with its typical goat sweat and dirty sock odor) and (… E 3-Methyl-2-hexenoic acid (human sweat odor) has also been successfully tested by the inventors. If these acidic pollutants can also be removed from indoor air, indoor air quality (IAQ) will be improved.

[0077] Regarding the short-chain aldehydes and carboxylic acids detected in many natural products isolated from Allium species, aldehydes are oxidized to acids by ZnO2 and subsequently captured by Zn(OH)2, while carboxylic acids are directly captured by Zn(OH)2 as described in the preceding paragraphs. Furthermore, pyruvate (a byproduct of the enzymatic breakdown of α-amino acid alliin and its analogues into allicin [CH2=CHCH2-S(=O)-S-CH2CH=CH2] and its analogues) can also be captured.

[0078] Experimental results Equal amounts of Zn(OH)2-ZnO2 mixture (1:2 w / w) granules or pellets, Zn(OH)2 powder, ZnO2 powder and ZnO powder were placed in separate laboratory glass columns (with small pieces of glass wool or degreased cotton placed at the bottom and top).

[0079] Each contaminant was generated in a round-bottom flask under highly diluted conditions and could be switched to an alternative glass column containing its respective absorbent via a valve system, guided by an airflow (3 L / min) to the appropriate detector. Airflow contamination was measured in ppm using commercial detectors (Aeroqual, Lander Technology-Dienmern, Temtop AQMonitors) before and after column entry.

[0080] The same contamination reduction effect was achieved using granules (spherical) or pellets (cylindrical). Depending on the specific circumstances, these porous granules and pellets, which are easily prepared as described above, are more efficient or slightly more efficient than an equal-weight mixture of two crystalline solids that have not been pre-granulated. This occurs despite the smaller effective reaction surface area of ​​the pellets. Therefore, in addition to the practical advantages of using pellets instead of powder in filters, the inventors attribute the performance of granules and pellets to the close proximity of hydroxyl and peroxide anions in the zinc aggregates, which allows for more rapid occurrence of sequential or concurrent acid-base and oxidation reactions.

[0081] The compositions disclosed herein have been compared with individual component powders and zinc oxide (ZnO). The comparison with zinc oxide (ZnO) is crucial because, as mentioned many times, it is the most standard zinc reagent used in the petrochemical industry for the removal of H2S / CH3SH and COS gases over the past few decades.

[0082] Comparative examples and results are described in Figures 1-6 In this study, an airflow of 3.0 L / min was used, contaminated with 6-8 ppm of each of the aforementioned VOSCs, either chemically generated in the reaction flask or commercially available. Relative chemical absorption efficiency was determined under extreme conditions: a continuous airflow containing 6-8 ppm of each individual contaminant. The outlet flow rate was measured to be 2.5 L / min.

[0083] Figure 1 The efficiency of pellets from a 1:2 w / w Zn(OH)2-ZnO2 mixture is shown when an air stream contaminated with vapors of 6-8 ppm of representative liquid thiols is continuously passed through a glass column approximately 4 cm high (each column filled with 12.0 g of the specified absorbent material), and compared with the reagents alone and ZnO (i.e., the standard reagent for capturing H2S industrially as described above). These thiols (referred to as Group A or Type A in the Background section) are ethanethiol and 1-butanethiol (first row) and thiophenol / benzenethiol (second row).

[0084] Under the conditions described in this report, the results of particle production are almost identical to those of pellet production; for simplicity, particle data are not included in the accompanying figures. Individually, both zinc compounds, Zn(OH)₂ and ZnO₂, are effective: Zn(OH)₂ due to its basicity and its ability to form zinc thiolates; ZnO₂ due to its oxidizing properties. For example... Figure 1 As shown in the first row, pellets are superior to individual components. The values ​​obtained for the ungranulated mixture of Zn(OH)₂ and ZnO₂ crystalline powders fall between those shown in the second and third columns, and therefore they are not included. The synergistic effect is more apparent when comparing the molar ratios of the components rather than their weight ratios: Column 1: 30.8 mol% Zn(OH)₂ + 31.4 mol% pure ZnO₂; Column 2: 100 mol% Zn(OH)₂; Column 3: approximately 46 mol% pure ZnO₂.

[0085] Figure 2This shows how the concentrations of individual pollutants dimethyl disulfide (CH3S-SCH3) and dimethyl trisulfide (CH3S-S-SCH3), examples of organic oligosulfides (Group B or Type B), decrease when a continuous airflow of the corresponding vapors passes through 12.0 g of absorbent material in a glass column (4 cm high), as described above. Similarly, the efficiency of 1:2 w / w Zn(OH)2-ZnO2 pellets or granules is compared with the efficiency of the reagent alone and ZnO. As can be seen from the first row, Zn(OH)2 (second column) and ZnO (fourth column) do not react with CH3S-SCH3 and CH3S-S-SCH3, as expected. On a molar basis, the first column is slightly more active than the third column. Furthermore, it is believed that once the S atom is oxidized by peroxide ions, the intermediates thiosulfinates and thiosulfonates [e.g., CH3S(=O)-SCH3 and CH3SO2-SCH3 in the case of CH3S-SCH3] may be cleaved by hydroxide ions to generate harmless zinc salts, which is a known rapid reaction in the case of thiosulfonates.

[0086] Figure 2 (Bottom) shows that the results for diallyl disulfide (CH2=CHCH2S-SCH2CH=CH2, from garlic) and dipropyl disulfide (CH3CH2CH2S-SCH2CH2CH3, from onion) are parallel to those obtained with dimethyl disulfide (CH3S-SCH3).

[0087] exist Figure 3 In this study, similar tests were performed on allicin (CH2=CHCH2-SO-S-CH2CH=CH2), vapors from chopped garlic (containing allicin, numerous VOSCs, and carboxylic acids, as described in the Background section), and vapors from freshly chopped onions (experimentally containing the tear gas Z isomer of propanethial S-oxide, as well as many other volatile dialkyl disulfides, thiosulfinates, aldehydes, and carboxylic acids), and their TVOC (total volatile organic compounds) levels were compared. In this case, the initial concentrations of pollutants were below typical levels: even when samples were freshly prepared from commercially available onions and garlic, it was difficult to generate airflows with TVOC concentrations exceeding 4.12 ppm (from chopped onions) and 2.33 ppm (from chopped garlic). Under experimental conditions, ZnO2 (i.e., peroxide ions are key) is crucial to significantly reduce the concentration of these vapors (including aldehydes); the presence of Zn(OH)2 (i.e., hydroxide ions) in pellets or granules, in addition to the aforementioned potential advantages, can effectively capture some garlic components, mainly aliphatic acids, as well as 2-propen-1-thiol ("allyl thiol", CH2=CHCH2SH).

[0088] Figure 4The chemical absorption of a continuous air stream contaminated with carbon disulfide (solvent CS2) vapor through a column packed with 1:2 w / w Zn(OH)2-ZnO2 pellets, equal amounts of each individual reagent, and equal amounts of ZnO was compared. Figure 4 This indicates that Zn(OH)2 is less effective than ZnO2 in removing CS2 (its hydrolysis under moderate alkali conditions is slower than its oxidation). Although Zn(OH)2-ZnO2 pellets show only a slight synergistic effect (calculated by molar ratio), their advantage is that the final oxidation byproducts CO2 and SO2 are mostly removed in the form of zinc carbonate and zinc sulfate, respectively.

[0089] Further experiments using a mixture of contaminants confirmed these results. Figure 5 ). Figure 5 The changes in total contaminant concentration are shown when a continuous stream of air simultaneously contaminated with three VOSC vapors (from a near equimolar mixture of three liquids with similar boiling points, at a concentration of up to 6.1 ppm) passes under the same conditions through a glass column filled with pellets (a 1:2 w / w mixture of Zn(OH)₂ and ZnO₂), and compared with other absorption columns. In the first column, all three components were almost completely removed within minutes (from 6.1 ± 0.1 ppm to 0.5 ± 0.1 ppm), while, based on the preceding figures, it was expected that only CH₃CH₂CH₂CH₂SH and some CS₂ would be captured in the second column. In the final column (ZnO), almost no components were chemically absorbed.

[0090] A blank experiment was also conducted. Figure 6 (First column and second column), using empty columns and columns filled with SiO2 (standard laboratory silica gel) to ensure that the air pressure drop (i.e., the flow rate of air passing through a column filled with pellets or solid zinc compound alone is experimentally reduced from 3.0 L / min to 2.5 L / min) is irrelevant.

[0091] When the column is filled with powdered activated carbon (activated carbon) or activated carbon pellets ( Figure 6 The third and fourth columns (respectively) were used to detect pollutants that were partially adsorbed (i.e., physically / temporarily / partially retained, but not chemically absorbed). This hypothesis was confirmed by saturating the two activated carbon columns and another column filled with Zn(OH)₂-ZnO₂ pellets (by passing a large excess of the three pollutants for 1 hour). Afterward, the pollutant inflow was cut off, and clean air was passed through the system: a continuous 0.7-0.8 ppm VOSC was detected emanating from the activated carbon column, while only 0.05 ppm escaped from the Zn(OH)₂-ZnO₂ pellet column for several minutes (surface-adsorbed but unreacted pollutants were desorbed, but various zinc salts generated from chemically absorbed pollutants were clearly retained in the filter).

[0092] Finally, additional experiments were conducted using 20 m... 3 The sealed container (“room model”) uses an air extraction turbine, with a filter 4 cm high (40 cm long × 40 cm wide × 4 cm high) added to its top. This filter is filled with pellets made from a 1:2 w / w Zn(OH)2-ZnO2 mixture, such as... Figure 7 As shown, unlike the previous laboratory experiments, a continuous stream of contaminated air was not introduced into the system. The container was first contaminated, typically to 6-8 ppm, then the supply of contaminated air was cut off, and the exhaust fan and corresponding detectors (electrical switches were outside the container) placed inside the container were activated. Within 15 minutes, the contaminant concentration decreased to 0.2-0.5 ppm. Within approximately 60 minutes, they decreased to <0.05 ppm (<50 ppb).

[0093] Therefore, the various experiments and examples disclosed herein demonstrate that, for the air purification of volatile organic sulfur compounds (VOSCs) of groups A, B, and C, mixtures of zinc compounds in particulate or pellet form outperform zinc oxide as well as zinc hydroxide and / or zinc peroxide used alone.

Claims

1. A filtration system for an air purification device for removing volatile organic sulfur compounds (VOSCs) from indoor air at room temperature, the filtration system comprising a filter element containing particles and / or pellets made of two zinc compounds, said two zinc compounds being zinc hydroxide Zn(OH)2 and zinc peroxide ZnO2, wherein said filter functions as an absorption filter that irreversibly reacts with said volatile organic sulfur compounds in polluted indoor air.

2. The filtration system according to claim 1, wherein the particles and / or pellets made of the two zinc compounds are prepared by the method described in the following steps: • The two zinc compounds are mixed in water or alcohol to form a suspension; • Extrude the corresponding suspension; • Dry the extruded suspension to obtain dried material; and • Cut the dried material into pieces.

3. The filtration system according to any one of the preceding claims, wherein the relative weight ratio between zinc hydroxide and zinc peroxide is 1:9 to 9:

1.

4. The filtration system according to claim 3, wherein the relative weight ratio between zinc hydroxide and zinc peroxide is 1:

2.

5. The filtration system according to any one of the preceding claims, wherein the diameter of the particles is about 3 mm, the diameter of the pellets is about 5 mm, and the length is at most 5 mm.

6. The filtration system according to any one of the preceding claims, wherein the particles and pellets made from the two zinc compounds do not contain any coagulants and / or chemical binders.

7. The filtration system according to any one of the preceding claims, wherein the filter element is placed between two nonwoven filters.

8. The filtration system according to any one of the preceding claims further includes EPA and / or HEPA filters.

9. A method for removing volatile organic sulfur compounds from indoor air, wherein a controlled airflow is passed through a filtration system comprising particles and / or pellets made of zinc hydroxide (Zn(OH)2) and zinc peroxide (ZnO2), wherein the volatile organic sulfur compounds undergo an irreversible reaction with hydroxide and / or peroxide anions, thereby being captured in the filtration system as harmless, white, non-volatile zinc salts.

10. The method for removing volatile organic sulfur compounds from indoor air according to claim 9, wherein the volatile organic sulfur compounds are vapors of liquid organic sulfur compounds selected from the group consisting of: (A) organothiols; (B) organic oligosulfides or dialkyl polysulfides, including disulfide derivatives present in Allium species; (C) carbon disulfide; and (D) combinations thereof.

11. The method according to claim 10, wherein the liquid organic thiol is an aliphatic thiol (R-SH) and an aromatic thiol (Ar-SH).

12. The method of claim 10, wherein the volatile organic sulfur compound is an aliphatic disulfide (RSSR), an aliphatic trisulfide (RSSSR), and related disulfides and thiosulfinates present in Allium species.

13. The method of claim 10, wherein the volatile organic sulfur compound is a vapor of carbonyl disulfide (S=C=S).

14. The method according to any one of claims 9 to 13, wherein the controlled indoor airflow passes through the filtration system at room temperature.

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