Humic Acids Used for Industrial Wastewater Treatment Application

Industrial wastewater treatment Product: Water-soluble sodium salt of humic acids

Humic acid salts for water treatment are used as an approx. 10% aqueous solution with a sodium content of approx. 1%.

The solution has a pH value of 9 to 10. The slight cloudiness or the possibly small sediment is caused by natural clay components. The humic acid salts are produced from an oxidation product of brown coal using a special extraction process. The product consists of high-molecular humic acids, which can be quantitatively precipitated or coagulated by neutralization and preferably multivalent cations. Humic acids for water treatment should not be confused with humic substances and their metal complexes, which are occasionally known from waterworks operations as particularly disruptive groundwater contaminants. These are low-molecular humic substances or humic substance precursors.

Properties: The coagulated humic acids have the following dominant characteristics:

1. Adsorption of lipophilic substances
2. Electron donor/acceptor complex formation
3. Salt formation with bases
4. Formation of poorly soluble complexes with polyvalent cations and heavy metals
5. Salt formation with acids and
6. Electron exchange capacity

Due to these characteristics, special humic acid salts are suitable as sorbents for a range of water contaminants, particularly for the substance groups

1. Heavy metals
2. Lipophilic substances.

A particularly valuable property of the industrial wastewater treatment humic acid salts is their coagulation capacity in the neutral to acidic pH range of the water, which causes it to precipitate in coarse flakes, especially in the presence of polyvalent cations such as calcium, aluminum or iron.

Spectrum of action: Due to the characteristics mentioned, this special form of humic acid salts is used for water purification. They are ideally suited to removing heavy metals from this medium, especially down to trace levels, such as:

1. Chromates
2. Nickel compounds
3. Copper compounds
4. Mercury compounds
5. Cadmium compounds
6. Lead compounds
7. Zinc compounds

Furthermore, the coagulated humic acid salts are able to bind lipophilic organic components by sorption due to their high internal surface. Due to the coagulating properties of the precipitated humic acid salts, they can also be used as flocculants or precoats for gravel filtration. Due to these properties, the humic acid salts can be used in a variety of ways to purify wastewater and mine water.

Application：

The humic acid salt solution is mixed with the wastewater to be treated using dosing systems, as is also common for dosing conventional flocculants. By neutralizing the wastewater, with the simultaneous addition of multivalent cations, preferably calcium chloride, aluminum or iron salts, it is coagulated at pH values ​​below 7.5. This creates typical humic acid flocs that are not only able to bind the above-mentioned solution load by sorption, but also coagulate the suspended matter load in the conventional way and thus bring about water clarification. Humic acid salts are particularly advantageous in combination with conventional flocculants. These usually hydrolyze to acids, which are neutralized by the added humic acid salt solution. This creates a very stable combined flocculation that can be effectively sedimented or filtered.

Special advantages in industrial wastewater treatment：

1. Separation of dissolved heavy metals
2. Separation of dissolved lipophilic substances
3. Effective flocculant for fats, oils and suspended matter of all kinds
4. Improvement of the effectiveness of conventional flocculants while simultaneously acting as an alkaline neutralizing agent
5. Improvement of sewage sludge properties through immobilization of heavy metals and lipophiles

Thereby:

1. Improvement of sewage sludge for use in agriculture by creating a natural soil pore structure
2. Humic acids are an essential natural substance for many ecosystems

Example:

Flue gas scrubbing from a waste incineration plant: The part of the water that is constantly diverted from the flue gas water cycle and discharged as waste water must be treated before discharge. The water, which usually contains a high heavy metal content, is usually highly acidic and therefore must be neutralized. The conventional processes for heavy metal separation are based on treatment with alkali to precipitate the heavy metals as hydroxides in the alkaline pH range. This precipitation process is not sufficient for some heavy metals, especially mercury.

Another disadvantage is the alkaline pH value of the waste water, which must be corrected in a further neutralization stage. By adding humic acid salt solution to the wastewater from flue gas scrubbing as a co-neutralizing agent (if necessary in combination with lime and conventional flocculants as well as iron salts and possibly organic polyelectrolyte). compared to the conventional alkaline precipitation process, The heavy metal content in the neutral to slightly acidic pH range can be quantitatively separated by humic acid. With the additional advantage of minimizing the salinization of the industrial wastewater treatment.

Disposal Due to the firm binding of the heavy metals in the humic acids, a release of these components from the sewage sludge is not to be expected even under conditions that can normally lead to the mobility of these elements. e.g. through so-called acidic precipitation, which can lead in particular to heavy metal mobility from the precipitated hydroxide.

Disposal routes that have previously been problematic, such as agricultural use for soil improvement, can thus be pursued with greater safety. The lipophilic pollutants present in the sewage sludge, e.g. aromatic polycyclics, polychlorinated biphenyls, dioxins and furans, are immobilized by humic acids. It is precisely for this reason that the use of humic acids in industrial wastewater treatment or sludge treatment is advantageous.

Sewage sludge containing humic acids is therefore much more suitable for agricultural use than comparable conventional sewage sludge, because the coagulated humic acids give the dried sludge and thus also the soil treated with sludge a crumbly, earthy-humic consistency, which can improve the function of the soil as a plant substrate in many ways (aeration, moisture retention, resistance to wind transport, fertilizer retention, reduction of soil permeability to nitrate, ammonium and biocides).

Otherwise, the humic acid-containing sludge can be used after drying as energy sources in thermal processes, such as:

1. waste incineration
2. waste gasification
3. waste pyrolysis
4. additional fuel in other incineration plants
5. cement production

Where the heavy metal content is preferably fixed in an environmentally friendly way in the slag melt or in the cement clinker, both of which are also raw materials for the construction industry, in silicate binding.

Industrial wastewater treatment product information:

1. Characteristics of humic acid salts
   • Appearance: black-brown water-soluble powder or flakes
   • Odor: odorless
   • Active substance: humic acids in the form of the sodium salt
   • CAS No.: 68131-04-4
   • pH value: 9-10
2. Toxicology and ecology After mixing and neutralization with the wastewater to be cleaned, the possible negative ecological or toxic effects resulting solely from the alkalinity of the humic acid solution used are eliminated. Since humic acids are a completely harmless natural substance, they themselves do not have any negative effects.
3. Storage and handling The storage stability of the humic acid salts is almost unlimited if the containers are not exposed to extreme fluctuations, such as heat or frost, and are stored dry. Contaminants on the skin can be removed with soap and water. If it comes into contact with the eyes, rinse immediately with plenty of clean water.
4. Transport regulations Not a dangerous good according to the applicable national and international transport regulations.