Humic acid is animal and plant debris under the action of microorganisms can be decomposed into simple organic compounds, and then by the condensation and the formation of an amorphous polymer compound, widely exists in the river, lake, sea sediment and soil, weathered coal, lignite, carbon mud. One of the main components of organic matter in natural water is humic acid, which accounts for 50% ~ 90% of total organic matter in water. The content of humic acid in most fresh water is 1 ~ 12 mg/L. In addition, there is a certain amount of humic acid in the waste liquor and alcohol waste liquor. Humic acid has been widely studied and applied due to its unique physical and chemical properties and biological characteristics. However, the concept of humic acid, the characteristics of environmental behavior, and its interaction with microorganisms in the environment are still lack of systematic exposition.
The concept of humic acid
At present, all kinds of references and products mentioned in the concept of humic acid are not consistent, not only the different articles referred to the concept of different, even the same article in the connotation of humic acid are different. Based on the analysis of chemical structure, humic substances are macromolecular aromatic compounds containing phenolic hydroxyl, carboxyl and hydroxyl groups. The main elements are C, H, O, N and S. The general meaning of humic acid is a broad concept, its connotation is equivalent to humus, including plant residues, wood fiber structure has saprophytic fungi and bacteria and other microbial metabolites, different degree of polymerization and decay of organic matter. The humic acid reported in the foreign literature covers the organic polymers with high molecular structure, such as lignin decomposing polymers, polysaccharides, peptides, fatty acids and so on. From the narrow sense, according to the solubility of different humic substances can be subdivided into humic acid, fulvic acid and humic type three. Among them, the soluble part is called Hu Min acid (black humic acid), soluble in alcohol or acetone part of the brown brown acid (Yoshima Tamiro acid), only part of the water soluble in the grass yellow, rich in acid (Huang Fusuan) (in Chinese). There is still debate over the chemical structure of humic acid, a view that the aromatic structure of the material is dominant, another view is that the aliphatic structure of the material is dominant. There are many reasons for the controversy, such as the source, extraction, purification and analysis methods of humic acid. If a person from the 3 kinds of organic materials of peat, lignite and weathering coal extraction of humic acid, the determination result of the composition and properties of lignite showed that Hu Min acid oxidation degree and aromatic degree is the highest, followed by weathered coal Hu Min acid, finally the peat Hu Min acid; weathered coal fulvic acid and aromatic oxygen degree of the highest degree secondly, lignite fulvic acid and peat fulvic acid. The recovery rate in weathered coal Hu Min acid is highest, followed by Hu Min acid and Hu Min acid peat lignite. The more accurate and comprehensive concept should be: humic acid is a kind of heterogeneous structure of polymer materials.
Because of the complexity of humic acid, the degradation of humic acid is still controversial. Sudha Goel and other studies have shown that only a small part of humic acid is biodegradable, most of which have biological inhibition group. However, Huang Tinglin and other studies have pointed out that humic acid has a certain degree of biodegradability, due to the impact of various factors in the bioreactor, its speed is generally slower.
Environmental behavior of humic acid
The natural humic acid extracted from weathered coal, lignite and peat has the advantages of abundant raw materials, low price and environmental friendliness.
Humic acid has the characteristics of weak acidity, hydrophilicity, cation exchange, complexing ability and high adsorption capacity. The high molecular weight characteristics of humic acid have been paid much attention and applied in environmental technology. As a kind of scale inhibitor and bactericide, humic acid product has been developed and used in industrial water treatment, and achieved good results. At present, most of the commonly used water treatment corrosion inhibitors in cooling water system at home and abroad are phosphate series. Because the phosphorus emission will cause the eutrophication of the surrounding waters, the development of low phosphorus or phosphorus free green water treatment agent has become the main direction of water treatment agent. The sodium humate molecules containing hydroxyl and carboxyl groups, these groups with more negative charge, can provide electrons to the metal ion of the outer track, or make the metal surface coverage of Fe3O4, SiO2 and CaCO3 and sodium humate complex, dense and stable chemical adsorption protective film - neutral insulating layer is formed on the metal the surface, so that the metal surface and the corrosion medium separated by slow chemical corrosion of the metal surface, showing good scale and scale and corrosion inhibition performance of humic acid water treatment agent, thus become a new direction for the development of green water treatment agent. Because the additive of humic acid drilling fluid has the functions of reducing fluid loss, reducing viscosity, preventing collapse, and has good salt and high temperature resistance, it is widely used in oil field.
Humic acid has a large specific surface area, so it can absorb a large amount of solid and gaseous substances. The addition of sodium humate in ammonium phosphate production can reduce ammonia, thereby reducing the slurry process of diammonium phosphate production cost. Humic acid as a high efficient and low-cost surfactant can reduce the cost of production, and has attracted the attention of foreign researchers in recent years. Study on remediation of petroleum contaminated soil. The results showed that humic acid has strong organic solubilization, diesel desorption concentration with the increase of sodium humate increases linearly, application of humic acid in oil contaminated soil to reduce the amount of surfactant, thereby reducing the pollution to the environment. Humic acid as the main raw material of water retaining agent, the cost of water retaining agent can be reduced by about 10%.
Although the adsorption of heavy metals by humic acid has been approved, there are still some objections to the understanding of the characteristics of different metal ions. Think of heavy metal contaminated soils the results of some researchers, humic acid can change the soil holding capacity of heavy metal ions on various forms of heavy metal absorption, soluble has direct toxicity dramatically reduced, while the heavy metal oxides bound and carbonate bound and organic bound increase, reduce heavy metal mobility in soil, activity and bioavailability. The results of other laboratory studies show that humic acid has a promoting effect on the dissolution of Cu and Zn in the extractant, but it has an effect on Pb and Cd, so it can improve the efficiency of Cu and Zn extraction. The quantitative research shows that the effect of humic acid on Cd content of soil in the form is: with the investment ratio increased, the soluble organic Cd decreased, Cd increased, iron and aluminum (MN) oxidation state Cd and organic Cd similar to the most significant correlation between soluble Cd and organic Cd and the.
Humic substances can be used to treat industrial heavy metal wastewater. Used as adsorbent of humic substance has two categories, one is naturally rich in humic acid in weathered coal, peat, lignite, mud pond (ditch), the price is low, the adsorption treatment of heavy metal wastewater has certain practical value, especially on the existing lignite humic acid application study on treatment of electroplating wastewater containing heavy metals is reported; the other is the rich in humic acid substances made of humic acid series resin in the treatment of electroplating industrial wastewater has been successful experience and equipment, such as the application of humic acid resin processing wastewater, chrome passivation cadmium plating wastewater, plating nickel wastewater. Sectional chemical degradation method has its own characteristics of innovation by Shanxi Coal Chemical Research Institute of Chinese, from all kinds of coal such as the extraction of water soluble humic coal lignite, peat and weathered coal (the coal base acid, fulvic acid, name) and the water soluble coal based acid composition, properties and structure characteristics study shows that the coal based acid as pesticide synergist in various agricultural products in use have achieved very good results.
Although humic acid (humus) as a plant growth regulator, the bioactive substances of feed additives and organic fertilizer such as a large number of reports, but these reports only stay in effect to describe the results, the effect of composition and the function of the mechanism described in ten is not clear, needs to be further studied.
Environmental remediation function of active humic acid
Active humic acid and humic acid are both related and different. The author has some understanding of active humic acid in his research field. The humic acid in this paper includes biological active humic acid (BFA) and modified humic acid. The biological activity of humic acid from crop straw, sawdust, bagasse and other agricultural waste by chemical or microbial fermentation preparation method. The main component of humic acid is the most active fulvic acid. Research shows that BFA also contains a variety of amino acids and beneficial microorganism, is a mixture of the condensation degree and low carbon content, low molecular weight, many active groups, with lighter color, better water solubility and high biological activity and easy passive, plant tissue absorption characteristics. However, it must be shown that fermentation humic acid can be purified. The environmental behavior of bio active humic acid not only includes the physical and chemical properties and biological characteristics of humic acid and microorganism, but also shows the particularity of the two.
Since 1920s, with the development of industry and agriculture, the environmental pollution problems caused by the discharge of industrial waste and unreasonable use of agricultural chemicals. In many developing countries and developed countries are facing the problem of soil and water pollution seriously hindered the ecological environment and agricultural production. Therefore, the problem of environmental remediation has become a hot research topic in recent years. Humic acid has attracted the attention of researchers in this field because of its unique characteristics.
Application of humic acid in oil drilling. The results showed that the modified humic acid in fresh water mud and saturated saline water mud dilution effect than Fe Cr lignosulfonate and sulfonated lignite is better in polymer mud modified humic acid has good dilution effect. Recently, foreign to the repair of humic acid caused by eutrophication of cyanobacteria the preliminary study showed that when the concentration of iron ions and humic acid in the water exceeds a certain threshold (iron 10-7 ~ 10-8 M, HA>0.1 mg/CL), can reduce or delay the growth of cyanobacteria, ease of eutrophication in water the pollution in a certain extent.
In recent years, active humic acid has been widely used in water environment. As a feed additive, humic acid can activate polyphenol oxidase, peroxidase, ascorbic acid, promote cell absorption and metabolism, enhance the immune function of animals, improve disease resistance. The use of bio active humic acid residue to produce sugar plants, can purify water quality and improve aquaculture water environment, promote healthy water and micro ecological system, reduce the ammonia and nitrite content in water by complexation, contribute to the growth of green algae and cyanobacteria, increase dissolved oxygen in water, to create a good environment for the growth of prawn and improve the shrimp yield and reduce feed coefficient, and can improve the breeding body immunity, improve economic efficiency. The active humic acid can improve the environment and improve the immunity of the organism. The nucleic acids, amino acids, vitamins, inositol, polysaccharides, etc. in biological active humic acid can be directly involved in the metabolism of the organism. The biological activity of humic acid in the feed can make big molecules full of nutrients into small molecular nutrients, while improving animal cell membrane permeability, so as to promote the absorption of nutrients, improve the production performance of livestock and poultry. The biological activity of humic acid contains quinone group, which is involved in the redox reaction of the body, maintains a strong metabolism and promotes cell division and proliferation. The biological activity of sodium humate in animals and plants can directly excite the nervous system, M like and N like receptors, M like effects, inhibition of the sympathetic nerve, the heart slows down, gastrointestinal activity enhancement, increased secretion of digestive juice, lower body temperature, reduce the consumption of livestock and poultry, in a quiet state, sleep time prolonged, the organ system (especially digestive system) function timely recovery, so as to improve the utilization rate of feed. The biological activity of humic acid by fermentation of various microorganisms and into, which contains a variety of active enzymes, can promote digestion, improve feed efficiency.
The activity of active humic acid in soil is closely related to the action of microorganisms. Soil microorganisms and their metabolites can adsorb and transform heavy metals. The bioaccumulation of heavy metals by microorganisms is mainly manifested in 3 forms: extracellular complexation, extracellular precipitation and intracellular accumulation. The microorganism can absorb heavy metal ions on the surface of the charged cells, or absorb the heavy metal ions by absorbing the necessary nutrient elements. According to Beveridge, the active site of heavy metals was first adsorbed on the surface of bacteria on the process in accordance with the stoichiometric rules, and formed a heavy metal core, heavy metals accumulated in the "core" around the void, until it fills around the nucleus so far. Microorganisms and other heavy metal elements in soil oxidation, some autotrophic bacteria such as sulfur and iron bacteria (Thiobacillus Ferrobacillus) As3+, Cu2+, Mo4+ oxidation and Fe2+, Pseudomonas aeruginosa (Pseudomonas) to As3+, Fe2+ and Mn2+ oxidation, microbial oxidation could make these heavy metals decreased the activity of. Sulfur reducing bacteria can be through two ways to reduction of sulfate into sulfide, a reduction of sulfate as electron acceptor in the process of respiration, the other is in the process of assimilation by sulfate synthesis of amino acids, such as cystine and methionine, and then through the desulfurization effect of S2- secretion in vitro. S2- can form precipitation with heavy metal Cd2+ to reduce the solubility and environmental toxicity of Cd2+. Soluble mercury (Hg2+) in the environment can be reduced to aerobic bacteria and volatile Hg, and released into the air, can be used to mercury mercury reducing bacteria (Hg2+) reduction and volatilization, in order to achieve the purpose of biological remediation of mercury contaminated soil. As far as the Cr element is concerned, Cr6+ is highly toxic and water-soluble, with low toxicity and water solubility and poor mobility in Cr3+. Therefore, the ecological toxicity of Cr and the mobility in the soil can be reduced by reducing, so as to achieve the purpose of pollution control. Penicillium can reduce Cr6+ to Cr3+, and its reduction is non induced, but in the presence of Hg2+, Cu2+, Co2+, Cd2+ and Ni2+ ions, the inhibition of Cr6+ has obvious inhibitory effect. There are a variety of distribution in the soil can make the reduction of chromate and dichromate bacteria, such as Alcaligenes sp. (Az-caligenes), bacillus, Corynebacterium (Corynebacteri-izm), enterobacter, Pseudomonas and Micrococcus (Microco-Cl, S), these bacteria can be reduced with high toxicity Cr6+ for the low toxicity of Cr3+. Therefore, it is necessary to study how to combine humic acid with microorganism to achieve better environmental remediation.
The biological activity of humic acid liquid vinasse production, not only solve the problem of alcohol wastewater treatment plant, reduce the production cost, and the produced active humic acid has multiple properties of fertilizers, pesticides and hormones, can be directly used as the promoter of crop seed germination and rooting of the use, can also be further processed as aquatic medicine, environmental protection the type of agricultural trace element fertilizer, fertilizer, fertilizer, vegetable water fruit tree fertilizer use.
At present, the research and application of active humic acid in agricultural sustainable development and environmental management have made great progress. The active humic acid can not only achieve the effect of increasing yield and income of agriculture, but also can effectively utilize industrial waste.
Development and application prospect of active humic acid
At present, the development and application of active humic acid as a green pollution-free biological products is still relatively narrow, which is mainly used in the field of agricultural production. Because the study of bioremediation of environmental pollution is still a very young discipline, the depth and breadth of research and abroad there is still a gap. The industrial production of organic waste a large number of people have not been seriously and became a source of pollution can be recovered; the number of extremely active humic acid considerable in industrial waste, a large amount of wastewater, such as papermaking wastewater contains large amounts of cellulose, by fermentation of specific microbes can be extracted from a large number of active humic acid. At present, the production of active humic acid vinasse technology has been in active humic acid applied to environmental purification of a pioneer step
