CN103252216B - Adsorbent, preparation process thereof and application of adsorbent to purification of ammonia-nitrogen wastewater with medium-low concentration - Google Patents

Abstract

The invention relates to a technology for purifying and treating ammonia nitrogen wastewater by adsorption method, in particular to an adsorbent and a preparation process thereof which are applied to purify medium and low concentration ammonia nitrogen wastewater. The iron-plated sawdust adsorbent of the present invention is composed of sawdust and Fe(OH) ₃ , and its preparation process: the sawdust is first washed with water for 1-3 times to remove impurities, dried and pulverized, and sieved so that the particle size of the sawdust is 198-350 μm. Percentage ≧ 80%; Finally, react FeCl ₃ solution with a concentration of 0.15~0.25 mol/L and NaOH solution to form Fe(OH) ₃ suspension; then sieve wood chips and Fe(OH) ₃ suspension at a solid-to-liquid ratio of 0.6 The ratio of ~1.0 g/10 mL was fully mixed, and the hydrothermal treatment was carried out at a temperature of 30-50 °C for 1.5-3 h. The product was washed with water until neutral, filtered with suction, and dried. It is used to purify medium and low concentration ammonia nitrogen wastewater, the removal rate of NH ₄ ⁺ -N is ≧90%, and the removal rate of COD is ≧75%.

Description

An adsorbent and its preparation process and its application to purify medium and low concentration ammonia nitrogen wastewater

technical field

The invention relates to a technology for purifying and treating ammonia nitrogen wastewater by adsorption method, in particular to an adsorbent and a preparation process thereof which are applied to purify medium and low concentration ammonia nitrogen wastewater.

Background technique

With the development of the economy and the continuous improvement of people's living standards, the pollution caused by ammonia nitrogen wastewater from a wide range of sources and increasing discharge has attracted global attention. In addition to petroleum, chemical, fertilizer, steel, food, pharmaceutical and other industries producing a large amount of wastewater, the decomposition of nitrogen-containing organic matter in domestic sewage, animal excretion, landfill leachate and the use of nitrogen fertilizers in agricultural production will also produce ammonia nitrogen pollution. After the ammonia nitrogen enters the water body, the most obvious thing is to cause the eutrophication of the water body, which causes the rapid proliferation of algae and plankton, the decrease of dissolved oxygen, the serious deterioration of the water quality, and the death of a large number of organisms, causing the water body to be black and smelly. In 2010, the total discharge of waste and sewage in my country reached 61.73 billion tons, of which the discharge of industrial wastewater was 23.75 billion tons, and the discharge of ammonia nitrogen in wastewater reached 1.203 million tons. It can be seen that ammonia nitrogen pollution has become one of the serious pollution problems in my country, and the removal of ammonia nitrogen in wastewater has become a hot and difficult point in environmental pollution control.

According to the different concentration of ammonia nitrogen in wastewater, wastewater can be divided into 3 categories: high concentration ammonia nitrogen wastewater (NH ₄ ⁺ -N >500 mg/L), medium concentration ammonia nitrogen wastewater (NH ₄ ⁺ -N is 50-500 mg/L ), low concentration ammonia nitrogen wastewater (NH ₄ ⁺ -N <50 mg/L). At present, the treatment technology of high-concentration ammonia nitrogen wastewater is relatively mature, but there are few studies on the treatment technology of medium and low concentration ammonia nitrogen wastewater, mainly including biological denitrification method, breakpoint chlorination method, ion exchange method, soil irrigation method, etc. Most of them have disadvantages such as high operating cost, complicated treatment process, and secondary pollution.

The adsorption method has been favored by people because of its simple and convenient operation and good removal effect. The traditional adsorption method mostly uses adsorbents such as activated carbon and activated carbon fiber, which have good treatment effects, but their service life is short, the operating cost is high, and the regeneration cost of the adsorbent is high, which limits its application. Therefore, the development of cheap and efficient materials for adsorbing medium and low concentrations of ammonia-nitrogen has become a research hotspot in adsorption methods.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned defects, provide an adsorbent and its preparation process and be applied to purify medium and low concentration ammonia nitrogen wastewater.

The technical scheme of the present invention: an adsorbent for iron-plated sawdust, which is composed of sawdust and Fe(OH) ₃ , wherein the mass percentage of sawdust is ≧99%, and the mass percentage of Fe(OH) ₃ is ≦1%.

An iron-plated sawdust adsorbent, the particle size of wood chips is 198~350 μm, accounting for ≧80% by mass.

A process for preparing an iron-plated sawdust adsorbent, comprising the following steps: the sawdust is first washed with water for 1-3 times to remove sand and mechanical impurities, dried and pulverized, and sieved so that the particle size of the sawdust is 198-350 μm in mass percentage ≧80% _; then react FeCl ₃ solution with a concentration of 0.15~0.25 mol/L and NaOH solution to form Fe(OH) ₃ suspension; The ratio of 1.0 g/10 mL was mixed thoroughly, and hydrothermal treatment was carried out at a temperature of 30-50 °C for 1.5-3 h. The product was washed with water until neutral, filtered with suction, and dried.

A preparation process of iron-plated sawdust adsorbent. The optimal process conditions are: the particle size of wood chips is 198-350 μm, accounting for 85% by mass, and the concentration is 0.15 mol/L. FeCl ₃ solution reacts with NaOH solution to form Fe( OH) ₃ suspension, then fully mix wood chips and Fe(OH) ₃ suspension at a solid-to-liquid ratio of 1.0 g/10 mL, hydrothermally treat at a temperature of 40 °C for 2 h, wash the product to neutrality, and suction filter. drying.

A method for purifying medium and low concentration ammonia nitrogen wastewater, comprising the following steps: adjusting the pH of the ammonia nitrogen wastewater to 9-11, using 3-5 g/L of iron-plated sawdust adsorbent, and a reaction temperature of 25-35°C, and adsorbing the ammonia-nitrogen wastewater and iron-plated sawdust After mixing the reagents for 20-50 min, filter.

A method for purifying medium and low-concentration ammonia nitrogen wastewater. The optimal parameter conditions are as follows: adjust the pH of ammonia nitrogen wastewater to 9, the amount of iron-plated sawdust adsorbent is 3 g/L, and the reaction temperature is controlled at 30°C. The ammonia nitrogen wastewater and iron-plated sawdust adsorbent After mixing for 30 min, filter.

The present invention adopts the hydrothermal method to prepare the adsorbent. The hydrothermal method is a new technology. The adsorbent prepared by this method has excellent performance: the particle distribution is uniform, the degree of agglomeration is light, and cheaper raw materials can be used, eliminating the need for high temperature Combustion and ball milling etc.

The present invention uses wood chips as the substrate of the adsorbent, based on the fact that the wood chips itself contains acidic substances such as cellulose, pentosan, and tannins, as well as some aldehydes, ketones, alcohols, and esters, which contain a large number of hydroxyl and carboxyl groups. , some free hydroxyl groups, free amino acids and free lignin, these functional groups can adsorb some cationic substances and organic substances; and Fe(OH) ₃ suspension has a certain flocculation function. Therefore, its sedimentation speed is fast, the removal rate of NH ₄ ⁺ -N is ≧90%, and the removal rate of COD is ≧75%, and the effluent after purification treatment can meet the standard requirements of "Comprehensive Wastewater Discharge Standard" (GB8978-1996).

The present invention is different from the activated carbon adsorption process. It is not only cheap and easy to obtain, but also has the characteristics of coexistence of adsorption and ion exchange. Its outstanding advantage is that iron-plated sawdust can be used as a biological adsorbent after being saturated with medium and low concentration ammonia nitrogen wastewater. Fertilizers are applied to orchards and gardens.

The determination of each process parameter is described in detail below:

1. The influence of hydrothermal synthesis temperature on the adsorption effect of ammonia nitrogen was investigated. The adsorption test conditions were: FeCl ₃ solution concentration = 0.15 mol/L, solid-liquid ratio = 1.0 g/10 mL, ammonia nitrogen wastewater pH = 9, reaction time = 30 min, the reaction temperature = 28°C, and the amount of adsorbent was 3 g/L. The effect of hydrothermal synthesis temperature on the adsorption effect of ammonia nitrogen is shown in Figure 1.

Figure 1 shows that with the increase of hydrothermal synthesis temperature, the removal effect of ammonia nitrogen is better. But too high synthesis temperature leads to higher cost.

2. The influence of modifier FeCl ₃ concentration on the adsorption effect of ammonia nitrogen was investigated. The adsorption test conditions were: hydrothermal synthesis at 40 ℃ for 2 h, solid-liquid ratio = 1.0 g/10 mL, ammonia nitrogen wastewater pH = 9, reaction time = 30 min , the reaction temperature = 31°C, and the amount of adsorbent was 3 g/L. The effect of modifier FeCl ₃ concentration on the adsorption effect of ammonia nitrogen is shown in Figure 2.

It can be seen from Figure 2 that compared with the Fe(OH) ₃ suspension, the removal rate of ammonia nitrogen by iron-plated sawdust is higher. As the concentration of Fe(OH) ₃ suspension increases, the removal rate of ammonia nitrogen also increases; the removal rate of ammonia nitrogen also increases with the increase of modifier iron ion concentration in iron-plated sawdust. In addition, it was found that the concentration of Fe ³⁺ in the solution increased slightly after the adsorption of ammonia nitrogen, so it was speculated that there may be cation exchange in the process of removing ammonia nitrogen from iron-plated sawdust.

3. The effect of the ratio of wood chips to Fe(OH) ₃ suspension (solid-to-liquid ratio) on the adsorption effect of ammonia nitrogen was investigated. The adsorption test conditions were: hydrothermal synthesis at 40 ℃ for 2 h, concentration of FeCl ₃ solution = 0.15 mol/L, The pH of ammonia nitrogen wastewater was 9, the reaction time was 30 min, the reaction temperature was 33°C, and the amount of adsorbent was 3 g/L. The effect of solid-liquid ratio on the adsorption effect of ammonia nitrogen is shown in Figure 3.

It can be seen from Fig. 3 that in the range of 0.6-1.0 g/10 mL, with the increase of the ratio of wood chips to Fe(OH) ₃ suspension, the removal rate of ammonia nitrogen decreased slowly; but in the range of 1.0-1.6 g/10 mL Within the range, the removal rate of ammonia nitrogen decreased rapidly.

4. The influence of solution pH on the adsorption effect of ammonia nitrogen was investigated. The adsorption test conditions were: hydrothermal synthesis at 40 ℃ for 2 h, concentration of FeCl ₃ solution = 0.15 mol/L, solid-liquid ratio = 1.0 g/10 mL, reaction time = 30 min, the reaction temperature = 32°C, and the amount of adsorbent was 3 g/L. The effect of solution pH on the adsorption effect of ammonia nitrogen is shown in Figure 4.

Considering that higher pH will lead to the evolution of ammonia gas, therefore, the pH range of the solution is set at 4 to 11. It can be seen from Figure 4 that when the pH changes in the range of 4 to 11, the net adsorption and removal rate of ammonia nitrogen by raw wood chips is up to 44%, and the removal rate of ammonia nitrogen by iron-plated wood chips is as high as 44%. The net adsorption removal rate is as high as 77%. The removal rate of ammonia nitrogen in the solution increases with the pH of the solution. This is because when the solution is acidic, the iron oxide layer on the surface of the iron-plated sawdust adsorbent undergoes hydroxylation in an acidic water environment and is positively charged; and when the solution is When alkaline, the surface of the adsorbent is negatively charged, and electrostatic attraction occurs with positively charged ionic ammonium.

5. The influence of reaction time on the adsorption effect of ammonia nitrogen was investigated. The adsorption test conditions were: hydrothermal synthesis at 40°C for 2 h, concentration of FeCl ₃ solution = 0.15 mol/L, solid-liquid ratio = 1.0 g/10 mL, pH of ammonia nitrogen wastewater = 9. The reaction temperature is 32°C, and the amount of adsorbent is 3 g/L. The effect of reaction time on the adsorption effect of ammonia nitrogen is shown in Figure 5.

Figure 5 shows that the entire adsorption process proceeded very rapidly within 20 min, and basically reached the adsorption equilibrium state after 30 min.

6. The influence of the amount of adsorbent on the adsorption effect of ammonia nitrogen was investigated. The adsorption test conditions were: hydrothermal synthesis at 40°C for 2 h, concentration of FeCl ₃ solution = 0.15 mol/L, solid-liquid ratio = 1.0 g/10 mL, pH of ammonia nitrogen wastewater = 9, reaction time = 30 min, reaction temperature = 34 °C. The effect of the amount of adsorbent on the adsorption effect of ammonia nitrogen is shown in Figure 6.

It can be seen from Figure 6 that with the increase of the amount of adsorbent, the removal rate of ammonia nitrogen also shows an upward trend, which is because the increase of adsorption sites makes the removal rate of ammonia nitrogen increase rapidly; and the increase of the amount of adsorbent also shows that the adsorption The amount of Fe ³⁺ on the surface of the agent increases, so its possibility of replacing ammonium ions increases. But after reaching 3 g/L, its upward trend is not obvious.

Description of drawings

Fig. 1 is the influence of hydrothermal synthesis temperature on ammonia nitrogen adsorption effect in the present invention.

Fig. 2 is the effect of modifier iron ion concentration on ammonia nitrogen adsorption effect in the present invention.

Fig. 3 is the influence of solid-liquid ratio on ammonia nitrogen adsorption effect in the present invention.

Fig. 4 is the influence of solution pH on ammonia nitrogen adsorption effect in the present invention.

Fig. 5 is the influence of reaction time on ammonia nitrogen adsorption effect in the present invention.

Figure 6 is the effect of the amount of adsorbent on the adsorption effect of ammonia nitrogen in the present invention.

Detailed ways

The medium and low concentration ammonia nitrogen wastewater referred to in the present invention refers to wastewater with an ammonia nitrogen concentration within the range of 50 to 150 mg/L.

Embodiment one:

The mass percentage of sawdust is 99.7%, and the mass percentage of Fe(OH) ₃ is 0.3%.

Preparation of iron-plated sawdust: the particle size of wood chips is 198-350 μm, the mass percentage accounts for 81%, the FeCl ₃ solution with a concentration of 0.15 mol/L reacts with NaOH solution to form a Fe(OH) ₃ suspension, and then the wood chips and Fe(OH ) ₃ Suspension was fully mixed at a solid-to-liquid ratio of 1.0 g/10 mL, then hydrothermally treated at a temperature of 40 °C for 2 h, the product was washed with water until neutral, filtered with suction, and dried to obtain the iron-plated sawdust adsorbent.

Purification and treatment of ammonia nitrogen wastewater by iron-plated sawdust adsorbent: the initial NH ₄ ⁺ -N and COD concentrations in the wastewater were 102 mg/L and 355 mg/L respectively, the reaction temperature was controlled at 25°C, and the pH of the wastewater was adjusted to 9. The iron-plated sawdust adsorbent The dosage was 3 g/L. After 30 minutes of reaction, the concentration of ammonia nitrogen in the filtrate was determined to be 10 mg/L, the COD was 83 mg/L, and the removal rate of NH ₄ ⁺ -N reached 90.2%.

Embodiment two:

The mass percentage of sawdust is 99.4%, and the mass percentage of Fe(OH) ₃ is 0.6%.

Preparation of iron-plated sawdust: the particle size of wood chips is 198-350 μm, the mass percentage accounts for 85%, the FeCl ₃ solution with a concentration of 0.20 mol/L reacts with NaOH solution to form a Fe(OH) ₃ suspension, and then the wood chips and Fe(OH ) ₃ Suspension was fully mixed at a solid-to-liquid ratio of 0.8 g/10 mL, then hydrothermally treated at a temperature of 30 °C for 3 h, the product was washed with water until neutral, filtered with suction, and dried to obtain the iron-plated sawdust adsorbent.

Purification and treatment of ammonia nitrogen wastewater by iron-plated sawdust adsorbent: the initial concentrations of NH ₄ ⁺ -N and Zn ²⁺ in the wastewater were 94 mg/L and 4.5 mg/L respectively, the reaction temperature was controlled at 35°C, the pH of the wastewater was adjusted to 10, and the amount of adsorbent After 40 minutes of reaction, the concentration of ammonia nitrogen in the filtrate was determined to be 9 mg/L, Zn ²⁺ was 1.2 mg/L, and the removal rate of NH ₄ ⁺ -N reached 90.4%.

Embodiment three:

The mass percentage of sawdust is 99.4%, and the mass percentage of Fe(OH) ₃ is 0.6%.

Preparation of iron-plated sawdust: the particle size of wood chips is 198-350 μm, the mass percentage accounts for 85%, the FeCl ₃ solution with a concentration of 0.20 mol/L reacts with NaOH solution to form a Fe(OH) ₃ suspension, and then the wood chips and Fe(OH ) ₃ Suspension was fully mixed at a solid-to-liquid ratio of 0.8 g/10 mL, then hydrothermally treated at a temperature of 50 °C for 1.5 h, the product was washed with water until neutral, filtered with suction, and dried to obtain the iron-plated sawdust adsorbent.

Purification and treatment of ammonia nitrogen wastewater by iron-plated sawdust adsorbent: the initial concentration of NH ₄ ⁺ -N and AsO ₄ ^3- in the wastewater were 147 mg/L and 0.9 mg/L respectively, the reaction temperature was controlled at 28°C, the pH of the wastewater was adjusted to 9, and the adsorbent The dosage was 4.8 g/L. After reacting for 30 minutes, the concentration of ammonia nitrogen in the filtrate was determined to be 13 mg/L, AsO ₄ ^3- 0.3 mg/L, and the removal rate of NH ₄ ⁺ -N reached 91.2%.

Embodiment four:

The mass percentage of sawdust is 99.0%, and the mass percentage of Fe(OH) ₃ is 1.0%.

Preparation of iron-plated sawdust: the particle size of wood chips is 198-350 μm, the mass percentage accounts for 83%, the FeCl ₃ solution with a concentration of 0.25 mol/L reacts with NaOH solution to form Fe(OH) ₃ suspension, and then the wood chips and Fe(OH ) ₃ Suspension was fully mixed at a solid-to-liquid ratio of 0.6 g/10 mL, then hydrothermally treated at a temperature of 45 °C for 2 h, the product was washed with water until neutral, filtered with suction, and dried to obtain the iron-plated sawdust adsorbent.

Purification and treatment of ammonia nitrogen wastewater by iron-plated sawdust adsorbent: the initial concentrations of NH ₄ ⁺ -N, COD, and AsO ₄ ^3- in the wastewater were 55 mg/L, 253 mg/L, and 0.7 mg/L, respectively, and the reaction temperature was controlled at 32°C. Adjust the pH of the wastewater to 11, the amount of adsorbent to 4 g/L, and measure the concentration of ammonia nitrogen in the filtrate after 50 min of reaction to 5 mg/L, COD 69 mg/L, AsO ₄ ^3- 0.3 mg/L, and the removal rate of NH ₄ ⁺ -N to reach 90.9%.

Claims (4)

1. a plating iron wood chip adsorbent, is characterized in that: by wood chip, Fe (OH) ₃composition, wherein wood chip mass percent Wei≤99%, Fe (OH) ₃mass percent Wei≤1%;

The preparation technology of the wood chip of plating iron simultaneously adsorbent carries out according to the following steps: wood chip is first washed through 1-3 times to remove silt, mechanical admixture, dries and pulverizes, sieve, make wood pellet particle diameter account for quality hundred points of number≤80% at 198 ~ 350 μm; Be the FeCl of 0.15 ~ 0.25mol/L by concentration afterwards ₃solution and NaOH solution are reacted and are generated Fe (OH) ₃suspension; To be sieved wood chip and Fe (OH) again ₃suspension fully mixes with the ratio of solid-to-liquid ratio 0.6 ~ 1.0g/10mL, hydrothermal treatment consists 1.5 ~ 3h at temperature 30 ~ 50 DEG C, and product is through being washed to neutrality, and suction filtration, dries.

2. a plating iron wood chip absorbent preparation technique, is characterized in that: comprise the following steps: wood chip is first washed through 1-3 times to remove silt, mechanical admixture, dries and pulverizes, sieve, make wood pellet particle diameter account for quality hundred points of number≤80% at 198 ~ 350 μm; Be the FeCl of 0.15 ~ 0.25mol/L by concentration afterwards ₃solution and NaOH solution are reacted and are generated Fe (OH) ₃suspension; To be sieved wood chip and Fe (OH) again ₃suspension fully mixes with the ratio of solid-to-liquid ratio 0.6 ~ 1.0g/10mL, hydrothermal treatment consists 1.5 ~ 3h at temperature 30 ~ 50 DEG C, and product is through being washed to neutrality, and suction filtration, dries.

3. a kind of plating iron wood chip absorbent preparation technique according to claim 2, it is characterized in that: optimum process condition is: wood pellet particle diameter accounts for quality Bai Fen Shuo≤85% at 198 ~ 350 μm, is the FeCl of 0.15mol/L by concentration ₃solution and NaOH solution are reacted and are generated Fe (OH) ₃suspension, then by wood chip and Fe (OH) ₃suspension fully mixes with the ratio of solid-to-liquid ratio 1.0g/10mL, hydrothermal treatment consists 2h at temperature 40 DEG C, and product is through being washed to neutrality, and suction filtration, dries.

4. Low Concentration Ammonia Containing Wastewater method in a purification, it is characterized in that: comprise the following steps: regulate ammonia nitrogen waste water pH to be 9 ~ 11, plating iron wood chip adsorbent amount 3 ~ 5g/L, reaction temperature 25 ~ 35 DEG C, after ammonia nitrogen waste water and plating iron wood chip adsorbent hybrid reaction time 20 ~ 50min, filter.