JPH0639277A - Active paddy husk and water purifying method using same - Google Patents

Abstract

PURPOSE: To prepare an active chaff having increased surface area and adsorption ability from chaff and to utilize the active chaff for water cleaning treatment by adding an inorg. acid and/or an alkali to carbonized chaff or silver white color chaff, heating it, thereafter filtering and drying. CONSTITUTION: An aq. soln. of an inorg. acid (such as hydrochloric acid) and/or an alkali (such as sodium hydroxide) are (or) are added to carbonized chaff or silver white color chaff, and the added substance is heated, thereafter filtered and dried. For example, a 10% aq. soln. of hydrochloric acid is added to the carbonized chaff, which is heated under reflux, and thereafter cooled to the normal temp. The surface area of the active carbonized chaff is 114 m<2> /g, which is prepared by washing the content with water, neutralizing with an aq. NaOH soln., thereafter further washing with water, filtering and drying. As a result, the active chaff having increased surface area and adsorption ability can be prepared from chaff. Various toxic contaminating substances dissolved in water can be removed by using the active chaff.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing activated rice husks having a large surface area and a high adsorption capacity from rice husks and a method for removing various harmful water pollutants by using the activated rice husks in a water purification process. .

[0002]

2. Description of the Related Art With the increase of population and the development of industry, the quality of surface water is rapidly deteriorating due to various domestic wastewater, agricultural wastewater, industrial wastewater and the like. Among various harmful components that pollute water quality, various harmful organic substances (trihalomethane, etc., hereinafter referred to as THMs), heavy metals,
Efforts to remove these harmful components with residual toxic pesticides and detergents by a simpler and more economical method are being actively carried out worldwide.

For example, trihalomethane is produced by reacting an organic substance dissolved in water with a halogen atom. Therefore, in order to suppress the production of THMs in a water treatment process, i) an organic substance contained in raw water (a precursor of THMs) Must be removed and the concentration thereof must be minimized, or ii) chlorine disinfection must be replaced with another disinfectant that does not produce trihalomethanes such as chlorine dioxide or ozone. In this case, chlorine dioxide and ozone, which are strong oxidizers, oxidize the organic substances in the water and reduce the concentration of precursors that produce THMs. As another means of reducing the concentration of the THMs precursor, there can be mentioned a method of adsorbing, aggregating and filtering an organic substance contained in water with plant activated carbon. However, these oxidizers and activated carbon are expensive, and in the case of ozone in particular, there is a drawback that ozone remaining after passing through the activated carbon layer must be removed in order to remove toxicity due to residual ozone.

[0004]

In the present invention, in order to solve the above-mentioned problems of the known art, so-called activated rice husk having a large surface activity is produced from rice husk obtained as a by-product at the time of rice production. It provides a new and improved method for water purification by using it in the water purification process and effectively removing various harmful pollutants mentioned above.

The annual production of rice in Korea is about 5.47 million tons, and the amount of rice husk as a by-product reaches 1.3 million tons.
At present, rice husks are carbonized by a general method and used as a heat retaining agent for molten metal (iron hot water) in an iron mill. The composition of the carbonized rice husk is mainly composed of silicate (Si content: about 20 to 30%) and carbon (about 30 to 50%), and contains a trace amount of potassium, calcium, magnesium, aluminum, iron, manganese and the like. . In addition to this carbonized rice husk, silver-white rice husk, which is a silicate mostly made by completely oxidizing carbon, is also produced.

[0006]

The present invention provides carbonized rice hulls or silver white rice hulls with inorganic acids (hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, HF).
Etc.) and / or an alkali (NaOH, KOH, etc.) aqueous solution, and after heating, filtration and drying treatment, a method for producing active rice husk in which the surface area and the adsorbing capacity associated therewith are greatly increased. In the present invention, rice husks whose surface activity has been increased by such a chemical treatment are named activated carbonized rice husks or activated silver white rice husks, respectively. Table 1 shows the results of elemental analysis of various active rice husks.

[0007]

[Table 1]

As shown in Table 2, the surface area of the carbonized rice hulls was about 103 m ² / g before the treatment, but it was 1 after the acid treatment.
It increased to 14 m ² / g and to 400 to 450 m ² / g after alkali treatment. Also, the surface area of silver-white rice husks was 4.6 m ² / g before the treatment, but after surface treatment with acid or alkali,
Slightly increased to 8 m ² / g.

[0009]

[Table 2]

[0010]

[Table 3]

[0011]

[Table 4]

In this case, it is considered that the water-soluble silicate and a trace amount of metal components are removed from the carbonized rice husk and the silver white rice husk during the treatment with acid and alkali to form new pores and increase the surface area. As shown in the surface analysis results in Table 2, the activated carbonized husk has micropores to macropores, and the surface area of the pores having a diameter of 20 Å or more, which is particularly effective for adsorbing organic substances, is 180 to It is 190 m ² / g and occupies 40 to 50% of the total surface area. In contrast to this, in the case of existing plant activated carbon, the surface area of pores in this range was 6 to 30% (58 to 210 m ² / g) of the total surface area depending on the raw material.

The method for treating water or wastewater of the present invention utilizes the increased surface activity of activated carbonized rice husks and activated silver white rice husks, i) adding fine powder in the water purification treatment process or ii) water purification process It is characterized in that it is put in place of the existing plant activated carbon used in the above-mentioned filtration tank to effectively remove various organic substances, heavy metal components, residual pesticide components, detergents and the like dissolved in raw water.

[0014]

EXAMPLES The method for producing activated carbonized rice husks and activated silver white rice husks, which are new adsorbents according to the present invention, and their removal ability for various harmful substances in water will be described in more detail with reference to the following examples.

Example 1. Production of activated carbonized rice husks 1.1. Production of activated carbonized rice husk (A) 60 g of carbonized rice husk was put in a flask and 10% hydrochloric acid aqueous solution 7
After adding 00 ml and heating under reflux for about 2 hours, the mixture was cooled to room temperature. The contents were washed with water 2-3 times, neutralized with an aqueous NaOH solution, further washed with water 2-3 times, filtered and dried. The surface area of the activated carbonized rice husk thus produced is 114 m ²
It was / g.

1.2. Production of Activated Carbonized Husk (B) 60 g of carbonized chaff was put in a flask, 700 ml of 10% NaOH aqueous solution was added, and the mixture was heated under reflux for about 2 hours and then cooled to room temperature. The contents were washed with water 2-3 times, neutralized with dilute hydrochloric acid, and then further washed 2-3 times with water. The surface area of the filtered and dried activated carbon hulls was 380 to 450 m ² / g.

1.3. Manufacture of activated carbonized rice hulls (AB) and activated carbonized rice hulls (BA) 60 g of carbonized rice hulls were placed in a flask and 10% aqueous hydrochloric acid solution 7
After adding 00 ml and heating under reflux for about 2 hours, the mixture was cooled to room temperature. The contents were washed with water 2-3 times and filtered, and then placed in a flask, 700 ml of 10% NaOH aqueous solution was added, and the mixture was heated under reflux for about 2 hours. After cooling to room temperature, wash with water 2-3 times, neutralize with dilute hydrochloric acid, and then with water 2-3 times.
Washed twice. After filtration, the surface area of the dried activated carbonized rice hulls (AB) was 216 m ² / g. Activated carbonized rice husks (B) when the above experiment was carried out in the order of alkali treatment and then acid treatment (B
The surface area of A) was 294 m ² / g.

Example 2. Production of activated silver white rice husks As a result of activating the silver white rice husks in the same manner as in Examples 1.1 and 1.3, the surface area was 6 to 8 m ² / g.

Example 3. Measurement of changes in pH, turbidity, BOD, and COD of water when activated rice husks are used in the water purification process A fine powder of activated carbonized rice husks (B) and activated silver white rice husks (AB) produced in Examples 1 and 2 30 after
mg was added to 1 L of raw water and stirred at about 150 rpm for 30 minutes. After additionally adding 12 mg of polyaluminum chloride, the mixture was further stirred for 6 minutes, then the speed was reduced to about 70 rpm, further stirred for 20 minutes and then left at room temperature. After the suspension was completely precipitated, the supernatant was taken and the pH, turbidity, B
OD and COD were measured. Existing plant activated carbon was used as a control group. Turbidity was measured with a HACH Ratio / XR Turbidimeter, and BOD was measured using known materials ["Standard Methods for the
Examination of Water and Waste Water ", Washington
DC 17ed, (1989)], and COD is Dr. La.
It was measured with a spectrophotometer manufactured by nge.

As shown in Table 3, with respect to pH and turbidity, activated carbonized rice husks (B), activated silver white rice husks (AB), and existing plant activated carbon all showed similar effects.
And COD were much better when treated with activated carbonized rice husk (B) than when treated with activated silver white rice husk (AB) or existing plant activated carbon.

[0021]

[Table 5]

Example 4. Measurement of trihalomethane production concentration when using active rice husks in water purification process 4.1. Put polyaluminum chloride (12mg / L) and Cl ₂ (0.5ppm) into raw water (collected at the water source pond),
After stirring at 0 rpm for 6 minutes, the stirring speed was reduced to 70 rpm, stirring was continued for 20 minutes, and the mixture was left at room temperature. After the suspension was completely settled, a part of the supernatant was removed to form T
The concentration of HMs was analyzed. See Table 4 for analysis results.

4.2. Example 4.1. The supernatant obtained from the above was used as a plant activated carbon layer (diameter 6 cm x height 20 cm, 280 g)
Or activated carbonized rice husk (B) layer (diameter 6 cm x height 20 cm, 5
After filtering through 0 g), the filtrate was subjected to gas chromatography (Purge and Trap, ECD) for comparative analysis of THMs concentration. See Table 4 for analysis results.

[0024]

[Table 6]

Example 5. Experiment for Removing Residual Toxic Pesticide in Water Using Activated Carbonized Husk (B) In this experiment, the activated carbonized rice husk (B) produced by the present invention was used.
In order to compare its ability to adsorb and remove residual toxic pesticides from existing plant activated carbon, an aqueous solution in which the highly toxic insecticides diazinon, fenitrothion and parathion are dissolved at concentrations of 6 ppm, 12 ppm and 18 ppm, respectively. After filtering (300 times the standard value of water quality in Japan) through a plant activated carbon layer (diameter 6 cm x height 20 cm, 280 g) or activated carbonized rice hulls (B) layer (diameter 6 cm x height 20 cm, 50 g), each The filtrate was analyzed using gas chromatography.

As can be seen from the results in Table 5, when filtered through the plant activated carbon layer, diazinon, fenitrothion and parathion were found to be 1.2 each from the 15th locus.
It was detected in the filtrate at concentrations of ppm, 1.4 ppm and 3.2 ppm, but no pesticide was detected up to 30 L when filtered through the activated charcoal husk (B) layer.

[0027]

[Table 7]

Example 6. Experiment for Removal of Phenol Dissolved in Water Using Activated Carbonized Husk (B) In this experiment, the activated carbonized rice husk (B) produced by the present invention was used.
In order to compare the adsorption and removal capacity for phenol, which is an organic toxic compound of, with existing plant activated carbon, an aqueous solution containing phenol dissolved at a concentration of 4.47 ppm (900 times the standard value for domestic water supply water quality) Vegetable activated carbon layer (diameter 6 cm x height 20 cm, 280 g) or activated carbonized rice husk (B)
After filtration through a layer (diameter 6 cm x height 20 cm, 50 g) each filtrate was analyzed using gas chromatography. As can be seen from the results in Table 6, when filtered through a plant activated carbon layer, it was already 42 ppb from the 15th locus.
Of phenol was detected from the filtrate, but when filtered through the layer of activated charcoal husk (B), no phenol was detected up to 15 L, and 12 ppb of phenol was detected after passing 30 L.

[0029]

[Table 8]

Example 7. Experiment for Removal of Surfactant Dissolved in Water Using Activated Carbonized Rice Husks (B) In this experiment, the ability of activated carbonized rice husks (B) to adsorb and remove anionic surfactants from existing plant To compare with activated carbon, an aqueous solution of 4.47 ppm of sodium dodecylbenzene sulfonic acid (about 10
Double the amount of the vegetable activated carbon layer (diameter 6 cm x height 20 cm, 28
0g) or activated carbonized rice husk (B) layer (diameter 6 cm x height 20 c
After filtering through m, 50 g), each filtrate was analyzed by absorptiometry (methylene blue method). As can be seen from Table 7, in the case of the plant activated carbon layer, 0.47 ppm of the surfactant was already detected at the 5th liter, but when filtered through the activated charcoal husk (B) layer, it was almost up to 30L. Not detected.

[0031]

[Table 9]

Example 8. Experiment for Removal of Metal Components Dissolved in Water Using Activated Carbonized Husks (I) 5.1 g FeCl ₃ .6H ₂ O, 7.41 g CuC
l ₂ , 3.8 g of MnCl ₂ .4H ₂ O, 15.93 g
Zn (NO ₃ ) ₂ .6H ₂ O, 1.35 g of Cr (NO
_{3) 2 · 9H 2 O,} 0.6g of Pb (NO _{3) 2} and 0.1
g of Cd (NO ₃ ) ₂ .4H ₂ O was placed in the flask and filled with distilled water to 1 L. 100ppm in 10ml of this solution
10 g of Hg ²⁺ solution was used and diluted to 35 L for use. This aqueous solution is used as a plant activated carbon layer (diameter 6 cm x height 20
cm, 280 g) or various activated carbonized rice husk layers (diameter 6 cm x height 20 cm, 50 g), and then each filtrate is analyzed by atomic absorption spectrometer (AA), inductively coupled plasma spectrometer (ICP)
Or inductively coupled plasma mass spectrometer (ICP-Mass)
Was analyzed. As can be seen from Table 8, in the case of plant activated carbon, most of the metal ions were already detected in the filtrate from the 1st eye, but activated carbonized rice hulls (AB), activated carbonized rice hulls (BA) or activated carbonized rice hulls were used. When filtered through layer (B), most of the metal ions other than Mn ²⁺ and Zn ²⁺ were barely detected until they passed through 30 L, especially Cr ³⁺ , Pb ²⁺ and Hg ²⁺ ions. Was not detected at all until it passed 45 L.

[0033]

[Table 10]

[0034]

[Table 11]

Example 9. Experiment (II) for removal of metal components dissolved in water using activated carbonized rice hulls (B) 9.1. Preparation of various metal ion aqueous solutions 1.44 g of Cd (NO ₃ ) .4H ₂ O, 1.45 g of H
g (NO ₃ ) ₂ , 1.96 g of Pb (NO ₃ ) ₂ , 0.38
g MnCl ₂ .4H ₂ O, 0.769 g ZnSO ₄
6H ₂ O, 0.054 g of Cr (NO ₃ ) 9H ₂ O,
0.254 g FeCl ₃ .6H ₂ O, 1.11 g C
uCl ₂ or 0.062 g of Ca (CH ₃ CO ₂ ) ₂ were used, each dissolved in 35 L of water.

9.2. Each aqueous solution of metal ions prepared in Example 9.1 was treated with an activated carbonized rice hull (B) layer (diameter 6 cm ×
After filtering through a height of 20 cm and 50 g), each filtrate was analyzed by atomic absorption spectrometer (AA), inductively coupled plasma spectrometer (IC).
P) or inductively coupled plasma mass spectrometer (ICP-Mas
s) was used for analysis. As shown in Table 9, the activated carbonized rice hulls (B) showed excellent adsorption ability for most of the metal ions tested.

[0037]

[Table 12]

[0038]

As can be seen from the above experimental results, the activated carbonized rice husk produced according to the present invention has a very large adsorption capacity and ion exchange capacity, so that various pollutants in water are aggregated, adsorbed and filtered. Is a new adsorbent that can be effectively and economically removed through.

Claims (4)

[Claims] 1. A method for producing active rice husk having a large surface area and adsorption ability, which comprises adding inorganic acid and / or alkali to carbonized rice husks or silver white rice husks, heating, filtering and drying. 2. The method for producing active rice husks according to claim 1, wherein the inorganic acid is an aqueous solution of an acid selected from hydrochloric acid, sulfuric acid, nitric acid, HF and phosphoric acid. 3. The method for producing active rice husks according to claim 1, wherein the alkali is an aqueous solution of an alkali selected from sodium hydroxide and potassium hydroxide. 4. Purified water or wastewater, characterized in that various kinds of harmful pollutants dissolved in water are removed by using the active rice husk produced by the method according to any one of claims 1 to 3. Processing method.