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Applications of Sodium Humate as Deodorant for Garbage Dumps

Time : 2022.03.09 Hits : 38

With a growing amount of wastes caused by human activities, various odors appear in such places as garbage dumps, toilets, animal farms and slaughterhouses and thus seriously pollute the environment. In today’s society, which greatly values the environment, it becomes rather urgent to solve the problem of how to effectively and quickly deodorize those fore-mentioned odor sources.

First, please let me analyze the root causes of odors in garbage dumps and animal farms. These odors are mainly caused by the decomposition of organic components in various wastes. The decomposition process can be generally divided into three stages: the first stage is the hydrolysis acidification stage, the second stage is the methane generation stage and the third stage is the conversion of most degradable organic matter into NH3 and CO2, which are released to the air.
The odors basically fall into the following three categories.
The first category principally include methane and carbon dioxide.
The second category includes malodorous gases such as H2S, NH3 and SO2. H2S is a kind of colorless toxic gas with an irritating and asphyxiating smell. NH3 is extremely harmful to human beings. SO2 is a colorless toxic gas with an irritating smell.
The third category are mainly trace components, such as organic acids, sugars and compounds containing sulfur and nitrogen, which are highly toxic and pose a serious threat to human health.

Then we will analyze why sodium humate can be used as a deodorant. Sodium humate deodorant is a product obtained by reacting such raw materials as peat, lignite or leonardite with sodium hydroxide. It is water-soluble and alkaline, containing active groups such as carboxyl groups and phenolic hydroxyl groups. Humic acid is a natural macromolecular organic compound which is generally considered to be a complex hydroxybenzenecarboxylic acid compound with uneven molecular weight (having an average molecular weight between 1000 and 1400). Its main constituent elements are: C (carbon), O (oxygen), H (hydrogen), N (nitrogen) and S (sulfur).

From the viewpoint of the physical properties of humic acid, it has a colloidal property, which plays an important role in its function as a deodorant. When electrolytes are added, the stability of the humic acid colloid is destroyed, its particles are flocculated to cause flocculation and precipitation, thus humic acid is a kind of flocculant. Judged from its chemical properties, humic acid is a kind of weak acid with complex macromolecular structure and various functional groups. It can be combined with potassium, sodium, calcium, magnesium or ammonium to form corresponding humate. Humic acid has a strong ion exchange capacity, thereby being able to remove harmful heavy metal ions when it contacts contaminants. It is particularly important that the humic acid molecules contain benzene ring, fused ring and various heterocyclic rings, which are connected by bridged bonds. On those rings and their branches, there are carboxyl groups, hydroxyl groups, methoxy groups and  amine groups, etc. Thus humic acid has such properties as acidity, hydrophilicity, ion-exchangeability; it also has strong complexation, chelating and adsorption capacity and thereby plays an important role in deodorization.

Listed below are the removal reaction processes of humic acid as a deodorant for odorous substances such as ammonia, nitrogen, hydrogen sulfide and sulfur dioxide:
1:Removal of NH3 and NH/:
Ammonia usually comes in forms such as NH3 and NH/. Humic acid can react with  ammonia in the odor and form an odor-free ammonium and water-soluble salt.
2:Removal of Nitrogen:
NO and NO2  are the most commonly-seen air pollutant in the form of nitrogen oxide. NO2 is a kind of toxic corrosive gas with an irritating smell. After humic acid contacting and reacting NO2, the peptization and absorption property of humic acid solution enables NO2 to be dissolved in water and form nitric acid and nitrous acid.
3:Removal of SO2:
SO2 is a kind of colorless toxic gas with an irritating smell and good water solubility. Since humic acid deodorant has peptization and adsorption property, its deodorizing effect is better after the contact of humic acid solution and SO2.
4:Removal of H2S:
4.1:The density of H2S in a certain dumping ground is closely related to the composition of the dump. If there is a large amount of organic matters in the dump, H2S will increase greatly when they decay. Sodium humate solution can react with H2S and remove the odor.
4.2:Removal of hydrogen sulfide by the absorption property of humic acid: humate can be hydrolyzed in water and forms a humic acid gel. Humic acid reacts with iron ions in the garbage and form a kind of humic acid iron salt (colloidal spongy iron). Then hydrogen sulfide reacts with hydrated humic acid iron and forms humic acid and insoluble iron sulfide. Humic acid and some metal ions can not only form salts, but also form compound or chelate through reaction between the oxygen-containing functional groups on its side chains and bivalent and polyvalent metal ions such as Cu”‘, Hg2+, Cd2+, Fe3+, Ge4+, U”. As long as H2S is present in the waste, when the above-mentioned metal ions contact with hydrogen sulfide, they will quickly combine into a insoluble sulfide precipitate, which quickly and thoroughly removes harmful hydrogen sulfide gas and it odor.
5:Removal of Trace Components Odors:

Organic acids, sugars and compounds containing sulfur and nitrogen are produced during the decomposition process of organic matters in the waste. These substances have certain reactive groups and they are easily complexed or chelated with such metal ions as Fe3+ or Mi. Humic acid, which contains aromatic structures and carboxyl groups, is a good chelating agents. Humic acid is capable of capturing metal ions due to its negative chargeability on its primary functional groups. In order to maintain the ionization equilibrium, the insoluble metal compound will be continuously dissociated, so that the metal may be converted from poorly soluble compounds to humates, coordination compounds or chelates, thereby removing the odors emitted by organic acids, sugars and sulfur- and nitrogen-containing heterocyclic compounds which are produced during the decomposition process of the garbage.

In addition, the humic acid content in sodium humate solution is a kind of nutrient-rich microbial nutritional medium. It is a beneficial bacterial population, containing beneficial microorganisms such as yeast, lactic acid bacteria, photosynthetic bacteria, and actinomycetes. Thus the beneficial microbial liquid plays a key role in removing pollutants. As long as the beneficial microbial population is activated, it plays an important role in the treatment of various pollutions.

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