KR20020043024A - Preparation of activated oyster shell and use thereof - Google Patents

Abstract

PURPOSE: Provided is a method for manufacturing an activated oyster shell(AOS), which useful to coagulate nutrients that is apt to suspend during dredging sediment. CONSTITUTION: The preparation of activated oyster shell comprises the steps of washing and drying oyster shell; crushing the oyster shell; and heat-treating the oyster shell at 350deg.C.

Description

Method for producing active powder oyster shell and its use {PREPARATION OF ACTIVATED OYSTER SHELL AND USE THEREOF}

The present invention provides a method for preparing an active powder oyster shell for washing, pulverizing and activating an oyster shell, wherein the pyrolysis temperature is 350 to 500 ° C., and the improved solid-liquid separation of sludge dredged soil or wastewater treatment plant sludge is used. It relates to the use of the active powder shell shell used.

Fish and shellfish farms in the sea and lakes differ somewhat depending on the type of aquaculture, but they contain many organic materials such as excreta, excess feed, and carcasses of aquaculture. These farm sediments act as a continuous source of contamination by eluting or moving into the water column depending on the conditions. The most direct and reliable way to solve this is to clean-up dredging.

Contaminated sediments raised from aquaculture should be separated into solids for the treatment of: In other words, suspended sediments have high concentrations of suspended solids, high concentrations of COD, nitrogen, and phosphorus, some of which settle again, but a large portion of the contaminants are present in the water.

Various flocculants for sludge treatment in domestic and international sewage treatment plants have been developed. However, the development of flocculants suitable for dredged soils in aquaculture farms containing a large amount of eutrophic nitrogen and phosphorus is insufficient.

Korean Patent No. 225047 (patented on September 15, 1993) by the present applicant discloses a method for producing active oyster shell powder for wastewater treatment, and an active oyster shell powder obtained according to the method. In this document, the oyster shell powder is produced by pyrolysis at 300 to 600 ° C., and the active oyster shell obtained as described above can be used to reduce the concentration of phosphorus in water to 1 mg / l or less.

The raw material of oyster shell consists of about 94% of CaCO ₃ and trace amounts of Mg, Al, and Si, and it converts into CaO through activation by high temperature treatment and has the property of binding to phosphorus in wastewater. .

Therefore, the present inventors measured the change in the components of the active oyster shell through pyrolysis experiments at various temperatures, and as a result, there is a significant difference in the composition of components in the pyrolysis treatment at 300 ℃ and pyrolysis treatment at 350 to 500 ℃ To discover and complete the present invention.

It was also found that co-precipitation of the active oyster shells prepared in this way together with existing organic flocculants could result in the coagulation and precipitation of a significant amount of eutrophication material resuspended during the dredging process of aquaculture dredged soils.

Accordingly, an object of the present invention is to provide an improved manufacturing method for producing an optimal activated oyster shell powder by analyzing the components of the active powder oyster shell.

In addition, the present invention provides the use of the active powder oyster shell for solid-liquid separation of aquaculture dredged soil and sludge to remove resuspended organic matter with a significantly higher efficiency than conventional by using an existing organic flocculant with the oyster shell produced by the above production method. It is aimed at.

1 is an XRD result showing the composition change of the active powder oyster shell when the pyrolysis temperature is 300 ℃.

Figure 2 is an XRD result showing the composition change of the active powder oyster shell when the pyrolysis temperature is 350 ℃.

Figure 3 is an XRD result showing the change in composition of the active powder oyster shell when the pyrolysis temperature is 400 ℃.

Figure 4 is an XRD result showing the composition change of the active powder oyster shell when the pyrolysis temperature is 450 ℃.

5 is an XRD result showing the composition change of the active powder oyster shell when the pyrolysis temperature is 500 ° C.

6 is an XRD result showing the composition of the active powder oyster shell when the pyrolysis treatment was not performed as a control.

The method for preparing the active powder oyster shell disclosed in the present invention includes washing and drying the oyster shell, crushing the dried oyster shell, and activating the obtained oyster shell powder, wherein the activation step is 350 to 500 It is characterized in that it is carried out through pyrolysis at ℃.

Oyster shells used in the present invention are shells of oysters inhabiting the sea, and since they are widely distributed in the sea, their shelling is very easy to obtain. It is cheaper.

Oyster shells collected offshore are washed with clean water to remove sand, soil and other contaminants.

Oyster shells with contaminants removed and dried in nature. Although it may be dried by a physical method by artificially applying energy, a natural drying method of evaporating water by exposure to the atmosphere is preferable in view of economical efficiency.

The dried oyster shell is pulverized to form a powder. If the particle size of the powder is too large or too small, the treatment efficiency may vary or problems may occur in the field application. Therefore, it is preferable to grind the oyster shell in a range suitable for the purpose of the present invention, and generally to a size of 30 to 50 mesh.

The activation of the oyster shell powder thus obtained is carried out by pyrolysis at 350 ° C to 500 ° C, and pyrolysis at 350 ° C is particularly preferable in terms of energy saving.

In addition, the present invention provides the use of active powder oyster shell to remove the eutrophication organic matter resuspended in the dredging process of aquaculture dredging soil in conjunction with the existing organic flocculant with a remarkably high efficiency.

Examples of existing organic flocculants include a product named "Supperfloc C577" and a product named "RS1883" which are approved by the US EPA and are currently used as solid-liquid separators for industrial wastewater or domestic sewage.

Hereinafter, the method for preparing the active powder oyster shell and the efficacy of removing pollutants in aquaculture dredged soil described in the present invention will be described in detail, but the present invention is not limited to these examples.

Example 1

Preparation of Active Oyster Shells by Pyrolysis

Oyster shells piled up on the shore were collected and washed with tap water. The oyster shell was left to dry at room temperature. The dried oyster shells were ground to 30 to 50 mesh to obtain a dry powder. The dried powder was pyrolyzed at 300 ° C., 350 ° C., 400 ° C., 450 ° C. and 500 ° C., respectively, without contact with oxygen in an electric heating furnace, and the XRD analysis of the components of each pyrolyzed sample was carried out. 5 is shown. As a control, the results of XRD analysis of the sample without pyrolysis are shown in FIG. 6.

As can be seen from the XRD analysis results shown in FIGS. 1 to 6, the component change of the sample at the pyrolysis temperature of 300 ° C. and 350 to 500 ° C. was significantly different. The analytical result of FIG. 1 shows a peak of a pattern similar to that of FIG. 6, which is an analytical result of a sample that is not pyrolyzed as a control, while the point of 37.3 during pyrolysis at 350 to 500 ° C. as shown in the analytical results of FIGS. 2 to 5 is shown. CaO peaks were observed as the main peaks at and 53.8, and oyster shells were also activated at several other points as the conversion from CaCO ₃ component to CaO component occurred.

Accordingly, the present invention provides a method for producing an active powder oyster shell, characterized in that the thermal decomposition step of 350 to 500 ℃ to induce a component change desirable for the purpose of the invention. In particular, the pyrolysis step at 350 ° C. is most preferable in terms of energy saving in addition to the solid-liquid separation efficiency.

Example 2

Efficacy test for solid-liquid separation of aquaculture

In order to test whether the active powder oyster shell prepared as in Example 1 is effective in solid-liquid separation of dredged soils, first, the contamination characteristics of the resuspended sediment dredged soils of the farms were analyzed five times. The results are shown in Table 1 below.

Pollution Characteristics of Resuspended Dredged Soil Item density Mean ± Standard Deviation Primary Secondary 3rd 4th 5th Suspended solids (mg / L) 216 161 286 185 109 191 ± 65.8 COD (mg / L) 8.9 5.4 5.6 7.0 8.4 7.1 ± 1.59 NH ₃ -N (mg / L) 6.767 5.540 4.441 4.304 6.852 5.581 ± 1.2200 NO ₂ -N (mg / L) 0.148 0.123 0.188 0.122 0.118 0.140 ± 0.0294 NO ₃ -N (mg / L) 0.271 0.380 0.374 0.367 0.167 0.312 ± 0.0925 DIN (mg / L) 7.186 6.043 5.003 4.793 7.137 6.032 ± 1.1343 PO ₄ -P (mg / L) 0.370 0.108 0.084 0.162 0.271 0.199 ± 0.1197 pH 8.09 8.54 8.12 8.15 8.45 8.27 ± 0.209

The first flotation and the fourth resuspension of aquaculture dredged soil containing such pollutants are treated with the existing flocculants RS1883 and C577, respectively, and the second resuspension is the active powder oyster shell (AOS) and C577 of the present invention. The treatments were analyzed for changes in the content of contaminants present in each sample.

In this experiment, RS1883 was injected 250 ml diluted 4 ml / L, C577 was injected 250 ml diluted 10 ml / L and pyrolyzed AOS was injected 2 g / L.

The analysis results are as described in Table 2 below.

Comparison of efficacy of each flocculant treated in dredged soil resuspension Item Existing Coagulant AOS + C577 RS1883 C577 Suspended solids (mg / L) 216 ⇒ 18 185 ⇒ 1 161 ⇒ 5 COD (mg / L) 8.9 ⇒ 6.7 7.0 ⇒ 3.6 5.4 ⇒ 3.2 DIN (mg / L) 7.186 ⇒ 6.480 4.793 ⇒ 3.576 6.043 ⇒ 2.252 PO ₄ -P (mg / L) 0.37 ⇒ 0.37 0.162 ⇒ 0.139 0.108 ⇒ 0.001 pH 8.09 ⇒ 8.13 8.15 ⇒ 8.12 8.54 ⇒ 8.61

As can be seen from Table 2, when the existing flocculant is used alone, the contents of the contaminants, especially DIN and phosphorus, are maintained in the suspension without significant change, whereas when using the AOS of the present invention together with C577, DIN is about 3 In the case of phosphorus, it was reduced by about 100 times, especially in the case of phosphorus, which could reduce phosphorus to almost zero in seawater.

The use of inorganic coagulants (AOS) as an inorganic coagulant that can remove contaminants that cannot be treated with existing organic flocculants, which are currently used as solid-liquid separators for industrial wastewater or domestic sewage, is an important environment to solve the problems of eutrophication in the future. The material can be used for sediment removal in fresh water and seawater farms as well as in general water sediments. In addition, when the active powder oyster shell is added to the general sludge treatment sludge treatment, the same effect will be obtained, and in the concentration process will also facilitate the sludge treatment with its sedimentation and water functionality. In the case of sewage sludge containing little harmful substances, active powder oyster shells containing Ca may be used to increase the effectiveness of soil improvers and fertilizers in the final sludge disposal.

Claims (3)

In the method of manufacturing an active oyster shell powder comprising washing and drying the oyster shell and then crushing the dried oyster shell, thus activating the oyster shell powder obtained, the activation step is carried out by pyrolysis at 350 to 500 ℃ Method for producing an active oyster shell powder, characterized in that. The method of claim 1, wherein the activation step is carried out by pyrolysis of 350 ℃. An active oyster shell powder produced by the production method of claim 1, which is used for solid-liquid separation of the dredged soil of aquaculture farm and sludge of sewage treatment plant.