阅读说明：本技术 磺化腐植酸及其制备方法、复配改性腐植酸吸附剂、应用及应用方法 (Sulfonated humic acid and preparation method thereof, compound modified humic acid adsorbent, application and application method ) 是由 赵仕林 谢代蕊 黄皓 廖洋 马骏 张衡 张洪成 于 2020-05-09 设计创作，主要内容包括：本发明涉及废水处理技术领域,公开了一种磺化腐植酸的制备方法,是以腐植酸为原料,经碳化、硝化和磺化处理得到。以磺化腐植酸作为吸附剂,可将其应用于低浓度氨氮的处理。再以磺化腐植酸和载铁腐植酸为复配吸附剂,用于处理低浓度废水,废水包含有氨氮、有机氮中的至少一种。本发明磺化腐植酸对NH<Sub>4</Sub><Sup>+</Sup>兼具吸附速率快、富集效果佳的双重有益效果。再联合载铁腐植酸共同处理低浓度废水,载铁腐植酸对低浓度废水中的有机氮通过配位络合作用进行吸附,通过两者的配合能够将低浓度废水中的氨氮、有机氮得到有效吸附去除。以腐植酸为原料进行改性得到的改性腐植酸吸附剂,具备原料易得、容易制取、吸附速率快、吸附效果佳,易于推广。(The invention relates to the technical field of wastewater treatment, and discloses a preparation method of sulfonated humic acid, which comprises the following steps ofHumic acid is used as a raw material and is obtained by carbonization, nitration and sulfonation. Sulfonated humic acid is used as an adsorbent and can be applied to the treatment of low-concentration ammonia nitrogen. And then sulfonated humic acid and iron-loaded humic acid are used as a compound adsorbent for treating low-concentration wastewater, wherein the wastewater contains at least one of ammonia nitrogen and organic nitrogen. Sulfonated humic acid of the invention is to NH 4 + Has the double beneficial effects of high adsorption rate and good enrichment effect. And then jointly treating the low-concentration wastewater by combining with the iron-loaded humic acid, adsorbing the organic nitrogen in the low-concentration wastewater by the iron-loaded humic acid through coordination and complexation, and effectively adsorbing and removing the ammonia nitrogen and the organic nitrogen in the low-concentration wastewater through the cooperation of the iron-loaded humic acid and the low-concentration wastewater. The modified humic acid adsorbent obtained by modifying humic acid serving as a raw material has the advantages of easily available raw materials, easiness in preparation, high adsorption rate, good adsorption effect and easiness in popularization.)

1. The preparation method of the sulfonated humic acid is characterized by comprising the following steps:

s1 pretreatment: uniformly mixing humic acid and water, adjusting the pH value to 7, dipping, filtering and drying;

s2 carbonization: putting the dried humic acid in S1 into a tube furnace for carbonization, and adding the carbonized humic acid into N₂Heating to a certain temperature in the atmosphere, and then preserving heat to obtain humic acid carbon;

s3 nitration: adding nitric acid into humic acid carbon in S2, nitrifying in a water bath environment, cooling, circularly washing with water and centrifuging to obtain nitrified humic acid carbon;

s4 sulfonation: adding the nitrated humic acid carbon in S3 into sulfonating agent solution for sulfonation, washing and drying to obtain sulfonated humic acid.

2. The method according to claim 1, wherein in the S2, the carbonization temperature is 400 to 550 ℃; in the S3, the concentration of nitric acid is 2.5-15%.

3. The preparation method according to claim 1, wherein in S3, the sulfonation temperature is 35-65 ℃, and the sulfonation pH is 10.0-12.5.

4. A sulfonated humic acid obtained by the production method according to any one of claims 1 to 3.

5. The application of the sulfonated humic acid is characterized in that the sulfonated humic acid is used as an adsorbent for treating low-concentration ammonia nitrogen wastewater.

6. The application method of the sulfonated humic acid is characterized in that the dosage of the sulfonated humic acid is 0.8-2.0 g/L, the adsorption time is 1-180 min, the pH value of ammonia nitrogen wastewater is adjusted to 4-8, and the ammonia nitrogen concentration of the wastewater is 5-30 mg/L.

7. The compound modified humic acid adsorbent is characterized by comprising sulfonated humic acid and iron-loaded humic acid, wherein the iron-loaded humic acid is obtained by carbonizing and loading iron.

8. The application of the compound modified humic acid adsorbent is characterized in that the compound modified humic acid adsorbent is used for treating low-concentration wastewater, and the wastewater contains at least one of ammonia nitrogen and organic nitrogen.

9. An application method of a compound modified humic acid adsorbent is characterized by comprising the following three application methods:

(1) when the pH value of the wastewater is less than 7, adding sulfonated humic acid, and when the pH value of the wastewater is 8-10, adding iron-loaded humic acid;

(2) when the pH value of the wastewater is more than or equal to 7 and less than or equal to 9, the adding sequence can be any one of the following: firstly, adding sulfonated humic acid and then adding iron-loaded humic acid; adding iron-carrying humic acid and then adding sulfonated humic acid; thirdly, simultaneously adding iron-loaded humic acid and sulfonated humic acid;

(3) when the pH value of the wastewater is more than 9, firstly adding iron-loaded humic acid until the pH value of the wastewater is 5-7, and then adding sulfonated humic acid.

10. The application method of claim 9, wherein when the compound modified humic acid adsorbent is used for treating different types of low-concentration wastewater, the adding amount of the compound modified humic acid adsorbent is different:

(1) when the compound modified humic acid adsorbent is used for treating low-concentration ammonia nitrogen wastewater, the ammonia nitrogen concentration is 5-30 mg/L, the dosage of sulfonated humic acid is 2-4 g/L, and the dosage of iron-carrying humic acid is 2-4 g/L;

(2) when the compound modified humic acid adsorbent is used for treating low-concentration organic nitrogen wastewater, the concentration of organic nitrogen is 5 mg/L-200 mg/L, the dosage of sulfonated humic acid is 2 g/L-4 g/L, and the dosage of iron-carrying humic acid is 2 g/L-3.2 g/L;

(3) when the compound modified humic acid adsorbent is used for treating wastewater containing low-concentration ammonia nitrogen and low-concentration organic nitrogen, the ammonia nitrogen concentration is 5-30 mg/L, the organic nitrogen concentration is 5-200 mg/L, the dosage of sulfonated humic acid is 2-3 g/L, the dosage of iron-carrying humic acid is 1-2 g/L, and the wastewater contains Na⁺、Ca²⁺、Mg²⁺、Al³⁺And (4) plasma metal ions.

Technical Field

The invention belongs to the technical field of wastewater treatment, and particularly relates to sulfonated humic acid and a preparation method thereof, a compound modified humic acid adsorbent, an application and an application method thereof.

Background

Along with the development of urbanization, more and more domestic sewage is generated, and the water pollution condition is increasingly complicated. The substances in domestic sewage mainly comprise two main types: soluble organic matter (DOM) and inorganic salt, wherein the nontoxic organic matter mainly comprises carbohydrate and humus, the inorganic salt mainly comprises sulfide, ferrite, nitrate, nitrite, ammonium salt and the like, and the sewage may also contain toxic persistent organic pollutants such as organic chlorine, organic nitrogen and the like. The typical characteristic of municipal sewage is nitrogen, which is mainly total ammonia nitrogen (TAN, TAN ═ NH)₃/NH₄ ⁺-N) and Organic Nitrogen (ON).

Ammonia Nitrogen (NH)₃/NH₄ ⁺-N) is a main nitrogen-containing pollutant in the water environment, wherein the serious eutrophication of the water body can be caused by the over-high concentration of inorganic nitrogen and ammonia nitrogen, the dissolved oxygen is reduced, and the water body is damagedA self-cleaning system for an environment. In order to inhibit the growth of algae, the maximum allowable concentration of ammonia nitrogen in groundwater supply is 1.0mg N/L. Therefore, the removal of low-concentration ammonia nitrogen from surface water channels and treated wastewater is of great importance to prevent algae growth and water eutrophication and to improve the quality of reclaimed water.

The adsorption method is the most common and effective method for the advanced treatment of low-concentration ammonia nitrogen. The currently researched adsorbents mainly comprise activated carbon, zeolite, resin, bentonite, fly ash, plant polyphenol, ceramic and modified products thereof and the like. The prior adsorbent mainly has the problems of long reaction time, low ammonia nitrogen adsorption capacity, low removal rate and high cost.

The patent with publication number CN104211246B discloses a method for treating low-concentration ammonia nitrogen wastewater or feed liquid. The patent treats ammonia nitrogen wastewater by a zeolite and gaseous membrane combined treatment mode, and has the defects of long treatment period and high cost.

The patent with publication number CN105060387A discloses a preparation method of biological particles for treating low-concentration ammonia nitrogen wastewater. The patent is used for adsorbing ammonia nitrogen, and mainly utilizes the action of fibers in reed particles and the ammonia nitrogen, and lignin and cellulose chains in the fibers are negatively charged between pH 5 and 7. The adsorption (ion exchange) with positively charged ions is promoted by electrostatic attraction, the time for the adsorption to reach equilibrium is short, and when the pH value exceeds 7, the equilibrium adsorption state is rapidly transferred to a non-ionic form, so that the removal of ammonia nitrogen is not facilitated.

Therefore, it is important to find an adsorbent which can quickly adsorb ammonia nitrogen and has low cost.

At present, the method for treating wastewater is very large, but the treated wastewater hardly reaches the A-type discharge standard, and even the super-magnetic separation and purification technology developed in recent years cannot reach the standard, and further treatment is needed. The method for treating the low-concentration wastewater mainly comprises an adsorption method, an oxidation method, a biological method and the like, and some biological methods have the problems of large occupied area, long running period and high cost; some oxidation methods can only convert ammonia nitrogen into nitrate nitrogen and nitrite nitrogen, which causes more serious water body pollution; some biological denitrification methods have the problems of high cost and difficult control, such as CN105110581B and CN 103710294B; some degradation methods only degrade a single pollutant into some intermediates, and the intermediates are more harmful, such as CN101372370B, CN104926019A and CN 205328805U. The adsorption method is widely applied due to the advantages of low cost, high adsorption effect and easy removal. The adsorption method is mainly used for selecting an adsorption material.

However, some adsorbents can only selectively adsorb part of pollutants, and do not have adsorption performance on broad-spectrum pollutants. In addition, some treatment methods are mainly used for treating ammonia nitrogen and organic nitrogen with high concentration, such as CN110156280A, CN105668810A and CN110283740A, but not for treating low-concentration wastewater.

Therefore, it is very important to find a multifunctional composite adsorption material for low-concentration ammonia nitrogen, organic nitrogen and organic matters in domestic wastewater.

Disclosure of Invention

Through a large amount of researches, we find that the sulfonated humic acid formed by carbonizing, sulfonating and modifying humic acid serving as a raw material is NH₄ ⁺Have the dual beneficial effect that adsorption rate is fast, the enrichment effect is good concurrently, and then be applied to low concentration ammonia nitrogen waste water with it, adsorb ammonia nitrogen waste water. And then jointly treating the low-concentration wastewater by combining with the iron-loaded humic acid, adsorbing the organic nitrogen in the low-concentration wastewater by the iron-loaded humic acid through coordination and complexation, and effectively adsorbing and removing the ammonia nitrogen and the organic nitrogen in the low-concentration wastewater through the cooperation of the iron-loaded humic acid and the low-concentration wastewater. The modified humic acid adsorbent obtained by modifying humic acid serving as a raw material has the advantages of easily available raw materials, easiness in preparation, high adsorption rate, good adsorption effect and easiness in popularization.

Therefore, the first objective of the present invention is to provide a method for preparing sulfonated humic acid, comprising the following steps:

s1 pretreatment: uniformly mixing humic acid and water, adjusting the pH value to 7, dipping, filtering and drying;

s2 carbonization: carbonizing the dried humic acid in S1 in a tube furnace, heating to a certain temperature in N2 atmosphere, and preserving heat to obtain humic acid carbon;

s3 nitration: adding nitric acid into humic acid carbon in S2, nitrifying in a water bath environment, cooling, repeatedly washing with water, and centrifuging to obtain nitrified humic acid carbon;

s4 sulfonation: adding the nitrated humic acid carbon in S3 into sulfonating agent solution for sulfonation, washing and drying to obtain sulfonated humic acid.

The modified humic acid obtained by carrying out pretreatment, carbonization, nitration and sulfonation on the sulfonated humic acid is easy to obtain raw materials and simple to prepare.

(1) The existing sulfonated humic acid is obtained by directly modifying through a sulfonating agent and is mostly used for flocculating wastewater with high concentration and severe pollution, but the sulfonated modified humic acid is almost completely hydrophilic, so that COD (chemical oxygen demand) of water quality is increased in the using process, and secondary pollution of water environment is caused. (2) As shown in fig. 1, it is a synthesis scheme of sulfonated humic acid. The sulfonated humic acid is carbonized firstly, loses micromolecular soluble humic acid and micromolecular groups such as methyl, methoxyl, alkyl and the like, reserves most aromatic nucleus structures of the humic acid, is further nitrified, and nitric acid oxidizes HA-COOH, -COH and HA-Ar-NO added to the humic acid₂Then sulfonating the mixture under alkaline condition to enable sulfonic group to replace nitro on carbon atom to generate HA-Ar-SO₃ ^-To obtain Sulfonated Carbonized Humic Acid (SCHA), which is called sulfonated humic acid for short. (3) The surface appearance of the sulfonated humic acid is in a non-uniform granular shape, interlayer gaps and gaps exist, and certain capillary force exists among the gaps, so that favorable conditions of physical adsorption are formed.

The second purpose of the invention is to provide sulfonated humic acid obtained by the preparation method of the sulfonated humic acid.

The third purpose of the invention is to provide an application of sulfonated humic acid, wherein the sulfonated humic acid is used as an adsorbent for treating low-concentration ammonia nitrogen wastewater.

The application utilizes the sulfonated humic acid as the adsorbent for treating low-concentration ammonia nitrogen in domestic sewage, and has the characteristics of large treatment capacity, continuous and stable removal capacity on the low-concentration ammonia nitrogen and excellent cycle performance.

(1) Humic acid is grafted with sulfonic acid anion through sulfonation, the electronegativity of the humic acid is changed, and compared with-COOH and-OH, H has strong electron-withdrawing effect on S atoms due to 2O atoms⁺More readily from-SO₃H group is detached from NH₄ ⁺Exchange, and then carry out electrostatic adsorption reaction to remove ammonia nitrogen, as shown in fig. 2, which is a schematic diagram of an adsorption process of sulfonated humic acid to adsorb ammonia nitrogen; (2) because of SO3 in the sulfonated humic acid^-Is grafted on the surface of humic acid, so long as the surface is fully mixed with NH₄ ⁺The contact can generate electrostatic force attraction to combine together, so as to achieve the effect of removing ammonia nitrogen, therefore, the reaction speed is higher and the reaction is rapid.

The fourth purpose of the invention is to provide an application method of sulfonated humic acid, wherein the dosage of the sulfonated humic acid is 0.8-2.0 g/L, the adsorption time is 1-180 min, the pH value of the ammonia nitrogen wastewater is adjusted to 4-8, and the ammonia nitrogen concentration of the ammonia nitrogen wastewater is 5-30 mg/L.

This application is through injecing the adsorption time of sulfonated humic acid's dosage, sulfonated humic acid as the adsorbent, the pH of ammonia nitrogen waste water and the ammonia nitrogen concentration of ammonia nitrogen waste water for reach best adsorption effect.

Specifically, the method comprises the following steps: the dosage of the sulfonated humic acid is 0.8 g/L-2.0 g/L, and the sulfonated humic acid has the best effect in the range; if the adding amount is too small, the adsorption sites are less, and the adsorption effect on ammonia nitrogen is poor; if the adding amount is too much, the adsorption capacity of the sulfonated humic acid is reduced, and meanwhile, because the adding amount is too much, the pH value of the wastewater is increased, and free NH is generated₄ ⁺The content is gradually reduced, causing that the removal rate is not obviously increased. Therefore, when the adding amount is comprehensively considered to be 0.8-2.0 g/L, the adsorption rate of the ammonia nitrogen is better when the pH value of the wastewater is adjusted to 4-8. When the adsorption time is 1-180 min, the adsorption removal rate is improved along with the prolonging of the time.

The fifth purpose of the invention is to provide a compound modified humic acid adsorbent, which comprises sulfonated humic acid and iron-loaded humic acid.

The iron-loaded humic acid is obtained by modifying ferric chloride after humic acid carbonization. Iron-carrying humic acid and NH₃·H₂And performing coordination complexing on the O to achieve the effect of adsorbing and removing ammonia nitrogen. Under the condition of not adjusting the pH value, the pH value of the ammonia nitrogen solution is acidic due to the iron-loaded humic acid, and NH₃·H₂The content of O form is very small, and only a very small amount of ammonia nitrogen can be removed through complexation, so that the O form and the O form need to be matched with sulfonated humic acid for use together, so that the ammonia nitrogen can be removed.

The sixth purpose of the invention is to provide application of the compound modified humic acid adsorbent for treating low-concentration wastewater, wherein the wastewater contains at least one of ammonia nitrogen and organic nitrogen.

The application adopts the compound modified humic acid adsorbent for adsorbing low-concentration ammonia nitrogen and organic nitrogen in the wastewater, and sulfonated humic acid can adsorb NH (ammonia nitrogen) electrostatically₄ ⁺N, organic nitrogen in the sewage is efficiently adsorbed by electrostatic, hydrophobic distribution and pi-pi action, and iron-loaded humic acid can respectively adsorb NH₄ ⁺-N and NH₃the-N and the organic nitrogen are mutually matched, so that the ammonia nitrogen and the organic nitrogen in the waste water can be efficiently adsorbed.

Specifically, the method comprises the following steps: (1) humic acid raw material is carbonized, and sulfonated humic acid prepared by sulfonation can adsorb NH on static₄ ⁺the-N has the properties of activated carbon, high specific surface area, electrostatic and hydrophobic distribution and pi-pi effect, and can efficiently adsorb organic nitrogen (RNH) in sewage₂-N), adsorption removal of organic nitrogen, mainly by means of electronegative sulfonated humic acids and organic nitrogen (RNH)₂-N) electrostatic interactions and hydrophobic partitioning interactions. (2) The humic acid raw material is carbonized and then loaded with Fe³⁺The modified iron-carrying humic acid can respectively adsorb NH₄ ⁺-N and NH₃N, has the properties of activated carbon, high specific surface area, hydrophobic distribution, coordination and pi-pi action, and can efficiently adsorb organic nitrogen (RNH) in sewage₂-N) and Ammonia Nitrogen (NH)₃-N). (3) For ammonia nitrogen, the adsorption removal rate of the iron-loaded humic acid on the ammonia nitrogen is increased along with the increase of pH,with NH₃·H₂The content of O increases. (4) The iron-carrying humic acid can adsorb and remove organic nitrogen, mainly through Fe and organic nitrogen (RNH)₂-N) coordination complexation.

The seventh purpose of the invention is to provide an application method of the compound modified humic acid adsorbent, which comprises the following three application methods:

(1) when the pH value of the wastewater is less than 7, adding sulfonated humic acid, and when the pH value of the wastewater is 8-10, adding iron-loaded humic acid;

(2) when the pH value of the wastewater is more than or equal to 7 and less than or equal to 9, the adding sequence can be any one of the following: firstly, adding sulfonated humic acid and then adding iron-loaded humic acid; adding iron-carrying humic acid and then adding sulfonated humic acid; thirdly, simultaneously adding iron-loaded humic acid and sulfonated humic acid;

(3) when the pH value of the wastewater is more than 9, firstly adding iron-loaded humic acid until the pH value of the wastewater is 5-7, and then adding sulfonated humic acid.

Specifically, the method comprises the following steps: (1) because the surface charge properties of the sulfonated humic acid and the iron-loaded humic acid are different, the adsorption mechanism of the sulfonated humic acid and the iron-loaded humic acid are different, so that the adsorption effect of the sulfonated humic acid and the iron-loaded humic acid on ammonia nitrogen is inhibited to different degrees under the condition of higher or lower pH value of the wastewater, and the sulfonated humic acid and the iron-loaded humic acid have antagonism. (2) The ammonia nitrogen removal rate of the sulfonated humic acid is increased and then decreased along with the increase of the pH value; the removal rate of the iron-carrying humic acid to ammonia nitrogen increases along with the increase of the pH value. If the pH value of the wastewater is less than 7, NH is contained in ammonia nitrogen₄ ⁺Mainly in form, adding sulfonated humic acid to increase pH to 8-10 and NH in ammonia nitrogen₃·H₂The form of O is increased, and the iron-carrying humic acid is more beneficial; if the pH value of the wastewater is more than 9, the ammonia nitrogen is replaced by NH₃·H₂The form of O is dominant, firstly adding iron-carrying humic acid to be beneficial, reducing the pH of the solution to 5-7, and using NH as ammonia nitrogen₄ ⁺The form is the main form, and the sulfonated humic acid is more beneficial.

The invention has the beneficial effects that:

(1) the raw material of the sulfonated humic acid is easy to obtain, the preparation process is simple, the adsorption rate to low-concentration ammonia nitrogen is high, and the adsorption effect is good; (2) sulfonated humic acid and iron-loaded humic acidThe compound adsorbent formed by combination has the properties of activated carbon, high specific surface area, hydrophobic distribution, coordination and pi-pi action, and can efficiently adsorb organic nitrogen (RNH) in sewage₂-N) and Ammonia Nitrogen (NH)₃N) so as to effectively adsorb ammonia nitrogen and organic nitrogen in the low-concentration wastewater, thereby reducing the COD of the wastewater.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments of the present application will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and that those skilled in the art can also obtain other related drawings based on the drawings without inventive efforts.

FIG. 1 is a scheme of the synthesis route of sulfonated humic acids;

FIG. 2 is a schematic diagram of an adsorption process of sulfonated humic acid to adsorb ammonia nitrogen;

FIG. 3 is a schematic diagram showing the effect of the dynamic adsorption and desorption times on adsorption of 35mg/L ammonia nitrogen by the SCHA column;

FIG. 4 is a data diagram of the effect of carbonization temperature, nitrification acidity and sulfonation pH on the preparation of sulfonated humic acid;

FIG. 5 is an SEM image of sulfonated humic acid;

FIG. 6 is a FT-IR spectrum of humic acid carbon and sulfonated humic acid carbon;

FIG. 7 is a data chart of the effect of contact time (i.e., adsorption time) on the removal rate of ammonia nitrogen adsorbed by sulfonated humic acid;

FIG. 8 is a data diagram showing the effect of pH on the removal of ammonia nitrogen adsorbed by sulfonated humic acid;

FIG. 9 is a data chart of the results of the influence of the dosing amount of sulfonated humic acid on the ammonia nitrogen removal rate and the adsorption capacity;

FIG. 10 shows Na⁺、Ca²⁺、Mg²⁺、Al³⁺A data graph of the influence result of ions on the adsorption of ammonia nitrogen by sulfonated humic acid;

FIG. 11 shows the influence of different temperatures on the adsorption capacity of SCHA and the first-order and second-order kinetics fitting curves (initial ammonia nitrogen concentration is 20 mg/L);

FIG. 12 is a data diagram of the effect of the sequential adsorption of ammonia nitrogen removal rate by adding a compound modified humic acid adsorbent;

FIG. 13 is a data diagram of adsorption results of a compound modified humic acid adsorbent on actual ammonia nitrogen wastewater;

FIG. 14-1 and FIG. 14-2 are graphs of data of the effect of the dosage of iron-carrying humic acid and the dosage of sulfonated humic acid on ammonia nitrogen removal rate, respectively;

FIG. 15 is a data diagram of adsorption results of a compound modified humic acid adsorbent on simulated organic nitrogen;

16-1 and 16-2 are data graphs of adsorption results of simulated ammonia nitrogen and organic nitrogen by the modified humic acid adsorbent;

FIG. 17 is a data diagram of adsorption results of the compound modified humic acid adsorbent on ammonia nitrogen and organic nitrogen in domestic sewage.

Reference numerals: HA represents humic acid, CHA represents humic acid carbon, and SCHA represents sulfonated humic acid; HA- (3%) Fe (III) represents iron-carrying humic acid with the carbonization temperature of 3% of iron-carrying quantity; TAN stands for Total Ammonia Nitrogen (NH 3/NH)₄ ⁺-N); TN stands for total nitrogen.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The invention provides a preparation method of sulfonated humic acid, which comprises the following steps:

s1 pretreatment: uniformly mixing humic acid and water according to the mass ratio of 1: 4-6, adjusting the pH value to 7 by using 0.2mol/L NaOH, dipping for 2 hours, carrying out suction filtration, and drying at 60 ℃;

s2 carbonization: carbonizing the dried humic acid in S1 in a tube furnace, heating to 400-550 ℃ in N2 atmosphere, and preserving heat to obtain humic acid carbon;

s3 nitration: adding nitric acid into humic acid carbon in S2, nitrifying for 2h in a water bath environment, cooling, centrifuging, washing with water for the first time, washing with water for the second time, and centrifuging to obtain nitrified humic acid carbon; the concentration of nitric acid is 2.5 to 15 percent, deionized water is used for primary washing, and the pH value of secondary washing is adjusted to 7 by 0.2mol/L NaOH;

s4 sulfonation: adding the nitrated humic acid carbon in S3 into a sulfonating agent solution for sulfonation, washing and drying to obtain sulfonated humic acid; the sulfonation temperature is 35-65 ℃, the sulfonation pH is 10.0-12.5, and the drying is carried out at the temperature of 60 ℃.

In the preparation process of the sulfonated humic acid, nitric acid mainly plays a role in nitration and oxidation, on one hand, the amount of carboxyl is increased, and on the other hand, NO can be grafted₂Providing substitution sites for subsequent sulfonation reactions, HNO₃The concentration of the catalyst has certain influence on the next sulfonation, the higher the acidity, the better the nitration degree, the more beneficial the sulfonation is, but the too high acidity also causes waste; the higher the sulfonation pH value, the higher the sulfonation degree, but the too high sulfonation pH value can weaken the ammonia nitrogen adsorption capacity.

The invention adopts nitric acid as an activating agent to treat CHA, because the nitric acid has obviously increased ammonia nitrogen adsorption performance of the CHA treated by nitric acid compared with the CHA treated by activated carbon, sulfuric acid and sodium hydroxide in the same adsorption time, because the acid functional groups of the CHA treated by nitric acid, such as-COOH, are increased and have larger specific surface area.

Secondly, the invention provides sulfonated humic acid which is prepared by taking humic acid as a raw material through carbonization, nitration and sulfonation.

Thirdly, the invention provides a method for treating low-concentration ammonia nitrogen wastewater by using sulfonated humic acid as an adsorbent.

Experiments show that SCHA is more suitable for treating low-concentration ammonia nitrogen wastewater and is not ideal in the treatment process of high-concentration ammonia nitrogen wastewater. Through the adsorption experiment of ammonia nitrogen on the SCHA column, NH is treated through SCHA₄ ⁺The corresponding primary and secondary cycle adsorption breakthrough curves are shown in fig. 3. NH (NH)₄ ⁺A concentration of 35mg/L, the ammonia nitrogen concentration reaching the breakthrough point by adsorption in the first and second circulation curves is 2mg/L, the emission standard is 8mg/L, the volumes of the ammonia nitrogen wastewater which can be treated to reach the standard are 0.88L and 0.94L respectively, and the volume of the ammonia nitrogen wastewater is slightly larger than the volume of the ammonium chloride solution at the breakthrough point. After the breakthrough point had been reached (the adsorption capacity had reached 6.16mg/g), but saturation did not occur with NH₄ ⁺The concentration of the discharged water is gradually increased, and the adsorption column SCHA is gradually saturated, which shows that the efficiency of SCHA for treating ammonia nitrogen with higher concentration is not ideal.

Fourthly, the invention provides an application method of sulfonated humic acid, wherein the dosage of the sulfonated humic acid is 0.8-2.0 g/L, the adsorption time is 1-180 min, the pH value of the ammonia nitrogen wastewater is adjusted to 4-8, and the ammonia nitrogen concentration of the wastewater is 5-30 mg/L. The adsorption time can also be 5min to 60min, 5min to 40min, 10min to 40min or 10min to 20 min.

When the sulfonated humic acid is applied to the treatment of low-concentration ammonia nitrogen wastewater, the sulfonated humic acid has the advantages of large adsorption capacity and high ammonia nitrogen adsorption removal rate. Compared with other adsorbents, the adsorption capacity of SCHA is higher than that of SCHA for treating ammonia nitrogen with the same concentration of 20mg/L, the adsorption removal rate of ammonia nitrogen with lower concentration is higher, and the SCHA is cheap in raw materials, easy to prepare and environment-friendly.

Meanwhile, SCHA has certain influence on the adsorption capacity and the adsorption rate of ammonia nitrogen at high temperature and low temperature. Langmuir, R of the model²Based on the data, the fitting data show that the Langmuir equation can more accurately describe the ammonia nitrogen adsorption behavior of the biochar, and the adsorption behavior of the SCHA on the ammonia nitrogen is more prone to uniform single-layer adsorption. R of Langmuir model²Less than 0.95, indicating that physical adsorption exists to a certain extent, but chemical adsorption is more favorable, wherein the adsorption effect of surface tension, capillary tension, micro-mesopores and the like are included. The main adsorption mechanism of SCHA on ammonia nitrogen is SO on SCHA₃ ^-Radical or carboxyl anion COO-with ammonium (NH)₄ ⁺) Thermodynamic function calculation results show that the reaction △ G<0, and △ H θ<0，△Sθ>0, indicating that the reaction is a spontaneous exothermic reaction, entropy increases, and high temperature is not favorable for the reaction. From a molecular point of view, NH₄Cl is hydrolyzed at high temperature and combined with water molecules to generate ammonia molecules, ion form ammonia Nitrogen (NH)₄ ⁺) The adsorption amount is also reduced.

In addition, Na also exists in the low-concentration ammonia nitrogen wastewater⁺、Ca²⁺、Mg²⁺、Al³⁺Etc., and the existence of the cations can influence the adsorption removal rate of the SCHA on the ammonia nitrogen, and the multivalent cations (Ca)²⁺、Mg²⁺、Al³⁺) Influence on Ammonia Nitrogen of monovalent cation (Na)⁺) More significantly, the negative surface charge of SCHA is easily eliminated with the increase of ionic strength, thereby reducing NH₄ ⁺Amount adsorbed on SCHA. Therefore, the ionic strength of the wastewater needs to be considered before the low-concentration ammonia nitrogen wastewater is treated, and the dosage of SCHA is increased, so that the ammonia nitrogen removal effect can be maintained.

Finally, the SCHA can realize the ammonia nitrogen analysis under 0.01mol/L HCl, and the analysis rate can reach more than 80 percent; regeneration can be realized under 0.01mol/L NaOH, the regeneration process is simple, and the adsorption capacity is only reduced by 7 percent after the regeneration process is circularly used for four times, which shows that the regeneration agent has reutilization property.

Fifthly, the invention provides a compound modified humic acid adsorbent, which comprises sulfonated humic acid and iron-loaded humic acid, wherein the iron-loaded humic acid is obtained by carbonizing and loading iron.

Sixth, the invention provides an application of a compound modified humic acid adsorbent, which is used for treating wastewater containing at least one of low-concentration ammonia nitrogen and organic nitrogen.

Seventh, the invention provides an application method of a compound modified humic acid adsorbent, which comprises the following three application methods:

(1) when the pH value of the wastewater is less than 7, adding sulfonated humic acid, and when the pH value of the wastewater is 8-10, adding iron-loaded humic acid; (2) when the pH value of the wastewater is more than or equal to 7 and less than or equal to 9, the adding sequence can be any one of the following: firstly, adding sulfonated humic acid and then adding iron-loaded humic acid; adding iron-carrying humic acid and then adding sulfonated humic acid; thirdly, simultaneously adding iron-loaded humic acid and sulfonated humic acid; (3) when the pH value of the wastewater is more than 9, firstly adding iron-loaded humic acid until the pH value of the wastewater is 5-7, and then adding sulfonated humic acid.

In the invention, when the composite adsorbent is used for treating different low-concentration wastewater, the dosage of the compound modified humic acid adsorbent is different:

(1) when the compound modified humic acid adsorbent is used for treating low-concentration ammonia nitrogen wastewater, the ammonia nitrogen concentration is 5-30 mg/L, the dosage of sulfonated humic acid is 2-4 g/L, and the dosage of iron-carrying humic acid is 2-4 g/L; (2) when the compound modified humic acid adsorbent is used for treating low-concentration organic nitrogen wastewater, the concentration of organic nitrogen is 5 mg/L-200 mg/L, the dosage of sulfonated humic acid is 2 g/L-4 g/L, and the dosage of iron-carrying humic acid is 2 g/L-3.2 g/L; (3) when the compound modified humic acid adsorbent is used for treating wastewater containing low-concentration ammonia nitrogen and low-concentration organic nitrogen, the ammonia nitrogen concentration is 5-30 mg/L, the organic nitrogen concentration is 5-200 mg/L, the dosage of sulfonated humic acid is 2-3 g/L, the dosage of iron-carrying humic acid is 1-2 g/L, and the wastewater contains Na⁺、Ca²⁺、Mg²⁺、Al³⁺And (4) plasma metal ions.