JP2002159952A - Method for removing harmful metal from waste viscus of scallop - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a practical method for efficiently removing harmful metals such as Cd in waste mainly composed of soft body parts such as mid-intestine gland (generally called 'uro' and hereinafter called waste visora) which are discharged without being utilized in food processing of a scallop. SOLUTION: Pulverized matter of waste visora of the scallop (preferably finely pulverized matter) is agitated in an aqueous medium to elute out harmful metals from waste visora pulverized matter in the aqueous medium (harmful metal eluting operation); suspended solid matter in the aqueous medium is precipitated by a coagulant (suspended solid matter coagulating operation); harmful metal-containing aqueous medium after separating the solid matter is brought into contact with a fibrous amidoxime capturing agent manufactured by a radiation graft polymerization method to make the harmful metals to be adsorbed onto the fibrous amidoxime capturing agent (adsorption operation of metal in aqueous phase by using the amidoxime capturing agent); the harmful metals adsorbed by the fibrous amidoxime capturing agent is eluted by a dilute acid to be recovered (adsorbed metal eluting and recovering operation); on the other hand, the separated solid matter is taken outside the system (solid matter discharging operation).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to waste mainly containing soft parts such as midgut glands discharged without being used in food processing of scallop (hereinafter referred to as "scale"). The present invention relates to a method for efficiently removing harmful metals such as Cd therein.

[0002]

2. Description of the Related Art Regarding the disposal and recovery of "scale" discharged in large quantities during the processing of scallop, various types of uranium are used because they contain a relatively high concentration of harmful metals (typically Cd). There's a problem. Scallop shells contain a significant concentration of cadmium (C
d) is contained, for example, there is a possibility of environmental pollution in landfill disposal or ocean dumping, and there is also a risk of secondary pollution in use as a fertilizer. Therefore, there is a demand for the development of a treatment technique for industrial waste. To date, scallop scales have been subjected to or proposed treatments such as incineration, electrolytic treatment, fertilization, feed conversion, and microbial decomposition.

When scallop shells are incinerated, the inner walls of incinerators and chimneys are significantly damaged due to the large amount of water and oil contained in the shells, and the durability of the incinerator deteriorates. . In addition, Cd contained in fly ashing generated by incineration may scatter into the atmosphere. Odor generation is also a serious problem.

[0004] A method of electrolytically processing the processing residue of scallop is described in, for example, "Waste Society Transactions", Vol. 9, No. 3, No. 145.
-Page 154 (2000) or Vol. 11, 2/3
No. 61-68 (1998). The outline of this description method is to immerse waste such as the midgut gland of scallop in a sulfuric acid solution to elute cadmium bound to living tissue into the sulfuric acid solution, and cadmium thus eluted. Perform an electrolytic treatment of a sulfuric acid solution containing
The eluted cadmium is deposited and collected on the cathode plate and removed. However, the conductivity of the solution subjected to the electrolytic treatment is poor, and for example, C
To reduce cadmium to a level of about 0.1 ppm of d, the applied voltage must be higher. That is, the electric resistance is high due to the oil content in the solution, and therefore, the processing speed is slow, and it is not suitable for mass processing of waste. The electrolysis efficiency in such an electrolysis method is on the order of approximately 0.01%.

[0005] It has been proposed that scallop shells be directly used as fertilizers and feeds, but harmful metals such as Cd contained in the scallops hinder their use. Such direct use is not preferred unless harmful metals are removed. For example, when used as a fertilizer, crops may be contaminated due to harmful metals such as Cd contained therein. Similar adverse effects would occur when used as feed.

[0006] It has been proposed that scallop shells be microbiologically treated to remove cadmium, and the treated material be used as feed [for example, "Journal of the Society of Waste Management," Vol. 8, No. 2,
No. 65-70 (1997)]. The outline of this microbiological method is that the soil microorganisms and sulfate-reducing bacteria are allowed to act on the scallop scale extract (nutrition source), and are generated by enzymes and sulfate-reducing bacteria secreted by the soil microorganisms. With H ₂ S, metals such as Cd from biological tissues are precipitated and removed in the form of metal sulfide, and the residue is converted to feed. In such a treatment method using microorganisms, the growth of microorganisms is indispensable, and a long treatment time is inevitably required.

[0007]

As mentioned above, each of the prior art methods proposed for the treatment of scallops scale has drawbacks or disadvantages. Among the conventional methods, the electrolytic treatment and the microorganism treatment are considered to be promising at present, but the electrolytic treatment still has an electrolysis efficiency of about 0.01%.
And at least 72 for microbial treatment.
Significant disadvantages such as requiring a processing time of about three hours are required. Accordingly, the present invention has been completed as a result of studies and studies aimed at providing a practical method for more efficiently removing harmful metals such as Cd in scallop shells.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a method in which a substrate (eg, a polyethylene non-woven fabric) which is conventionally known as an adsorbent for collecting uranium resources dissolved in seawater is bonded by a radiation graft polymerization method. Adsorbent obtained by amidoximation of a portion of a polymer chain (eg, polyacrylonitrile chain, polyacrylonitrile-methacryl chain) [Journal of the Japan Sea Water Society] 53, p. 180-184 (1999)], which adsorbs metals such as cadmium in an aqueous medium quickly and effectively, and easily desorbs and releases the adsorbed metals by washing with a dilute acid. ing.

Accordingly, the present invention provides a method of stirring a scallop crushed product (preferably as finely pulverized as possible) in an aqueous medium to elute harmful metals from the scallop product into an aqueous medium. A suspended solid content in the aqueous medium is precipitated by a flocculant; the harmful metal-containing aqueous medium after the solid content is separated is brought into contact with a fibrous amidoxime trapping material produced by a radiation graft polymerization method to cause harmful metal. Is adsorbed by the fibrous amidoxime collector; the harmful metal adsorbed by the fibrous amidoxime collector is recovered by eluting with a dilute acid; while the separated solids are taken out of the system;
Provided is a method for removing harmful metals from scallop scales, including various steps.

In the method of the present invention, in order to promote the elution of harmful metals from the scales of scallops, the scales are brought into contact with an aqueous medium in a form as finely ground as possible, followed by stirring. It is charged and stirred or homogenized preferably using a high-speed high-speed rotary stirrer, more preferably a homogenizer until the harmful metal is sufficiently eluted. Water is usually used as the aqueous medium.

[0011] A coagulant is added to the slurry-like liquid after completion of the elution treatment of the metal from the ground scallop scales, and the mixture is stirred and allowed to stand to settle suspended solids, or by centrifugation or the like. Then, solid-liquid separation is performed to obtain a harmful metal-containing supernatant. Other separation means such as a filter, for example, an in-line filter, may be employed for the solid-liquid separation.

The flocculant used may be a conventional one, but it will be necessary to select an appropriate one according to the use of the solid to be separated or the place of disposal. If so, an appropriate flocculant to be employed could be easily selected. Examples of specific flocculants include, but are not limited to, sodium polyacrylate, sodium sulfate, sodium aluminate, iron (II) sulfate, chlorinated green bun, and the like. Flocculants are commonly used, for example, at concentrations of less than about 1%.

The solids separated at this time have various water contents depending on the degree of separation (strength), and can be a solid slurry, a paste, a semi-solid, or a solid. These can be used as they are as fertilizers or feeds, or can be mixed with other fertilizer components or feed components to form fertilizer compositions or feed compositions. Further, in the method of the present invention, a dewatering treatment and a drying treatment may be further performed as needed before the separated solid content is taken out of the system,
The semi-solid and solid products obtained in this manner have a volume significantly reduced by about 0.08 times and a weight of about 0.16 times as compared with the first supplied scallops. Thus, the ease of subsequent handling, the ease of disposal, and the ease of transport can be improved.

The fibrous amidoxime-collecting material used for adsorbing harmful metals in an aqueous medium in the method of the present invention can be prepared by a known method. The fibrous amidoxime trapping material is described in, for example, the above-mentioned literature: “Journal of the Japan Society of Sea Water” 5
3, p. As described in 180-184 (1999), for example, acrylonitrile is graft-polymerized to a substrate made of, for example, a polyethylene nonwoven fabric, or acrylonitrile and methacryl are co-grafted and polymerized by a radiation graft polymerization method. The portion of the grafted polymer chain (ie, polyacrylonitrile polymer chain or polyacrylonitrile-methacrylic acid copolymer chain) is amidoximated. This amidoximation is carried out by the cyano group of the acrylonitrile unit in the polymer chain.
The reaction can be carried out by reacting CN with hydroxylamine (NH ₂ OH) to form an amidoxime group —C ＝ N (OH) NH ₂ .

The contact between the harmful metal-containing aqueous medium and the fibrous amidoxime trapping material for adsorbing harmful metals in the aqueous medium after the solid content is separated by the method of the present invention is carried out by adsorbing the residual metals in the aqueous medium by adsorption. To an acceptable level
For example, at or near equilibrium concentration, for a reduced time. This contacting operation is preferably carried out by filling the column with the fibrous amidoxime-collecting material and flowing the harmful metal-containing aqueous medium through the column.

The metal adsorbed on the fibrous amidoxime trapping material can be easily eluted and recovered by washing the harmful metal-carrying fibrous amidoxime trapping material with a dilute acid such as dilute hydrochloric acid. When a column packed with a fibrous amidoxime collecting material is used, a metal can be eluted and recovered by flowing a dilute acid through the column, thereby regenerating the column packed with a fibrous amidoxime collecting material. You. If necessary, the column can be washed with an alkali, neutralized, and reused in the next harmful metal adsorption operation.

When the method of the present invention is put to practical use, a plurality of columns packed with a fibrous amidoxime trapping material are arranged in parallel, and the operation of adsorbing and removing harmful metals in each column is performed by switching valves. Perform the elution operation and the regeneration preparation operation for the next removal of harmful metals in parallel or in coordination (in harmony with the progress of other steps), so that the whole process can be performed substantially continuously. Can be. For example, if three units A, B and C are arranged in parallel, at some point A will be used for the harmful metal adsorption and removal operation, B will be subjected to the adsorption harmful metal elution operation, and C will be After a regeneration preparation operation for adsorption removal, it can be made to be in a standby state, and this cycle can be made to proceed by switching a valve.

FIG. 1 is a flow sheet showing an outline of one embodiment of the method of the present invention. Scallop scales and water are charged into a container (sedimentation tank) at a weight ratio of, for example, about 1: 4, and stirred at high speed with a homogenizer to pulverize the scales and bring them into close contact with water. Hazardous metals such as Cd bound to the tissue are eluted into the aqueous phase. Normally, this contacting and stirring is continued until the concentration of the harmful metal in the aqueous phase reaches equilibrium. The achievement of an equilibrium concentration can be detected by monitoring the concentration of the metal in the aqueous phase continuously or at regular time intervals. Once at or near the equilibrium concentration of harmful metals in the aqueous phase, add a flocculant to the settling tank, stir to aggregate the solids, separate the solids by centrifugal dewatering, if necessary Dry and remove by air drying. On the other hand, the harmful metal-containing liquid (supernatant) separated from the solid content is allowed to flow through a column filled with the fibrous amidoxime collector to adsorb the harmful metal. The concentration of harmful metals in the water discharged from this column is monitored continuously or at regular time intervals. Stop metal adsorption. In this saturated or near-saturated column, adsorbed harmful metals are eluted and recovered by flowing a dilute acid (eg, dilute hydrochloric acid of about 0.5N). Thereafter, if necessary, the fibrous amidoxime collecting material in the column is regenerated by neutralization with an alkali solution, and the column is made to stand by for the next harmful metal adsorption operation.

[0019]

Example 1 A four-fold amount (by weight) of pure water was added to scallops and ground and stirred for 1 hour with a homogenizer, and then 0.1% (by weight) of sodium polyacrylate was used as a flocculant. Was added and stirred to solidify the solid content. 1 g of the amidoxime collector was added to 200 ml of the supernatant obtained by subjecting the aqueous mixture to solid-liquid separation, and the mixture was continuously stirred with a stirrer, and occasionally sampled to measure the Cd concentration. Almost saturated adsorption was reached by stirring for about 30 minutes, and 0.05 p
Cd of about pm remained. Cd adsorbed on the amidoxime collector was eluted using 0.5N hydrochloric acid.

Example 2 (Using an amidoxime collecting material column)
The same operation as the general operation of Example 1 was repeated, but in this example, metal adsorption was performed using a column of amidoxime collecting material. That is, first, 4 times (by weight) pure water is added to the scallop shell, and the mixture is ground and stirred with a homogenizer for 1 hour, and then 0.1% (by weight) of sodium polyacrylate is added as a flocculant and scraped. Mix to agglomerate solids. Next, the supernatant liquid obtained by the solid-liquid separation was applied to a column packed with a fibrous amidoxime collector, and the space velocity SV =
The solution was sent at 10 hr ^-1 . The effluent from the column during this metal adsorption operation contained 0.007 ppm of residual Cd.

The adsorbed Cd was eluted by sending a dilute acid (0.5N HCl) to the collecting material packed column after the metal adsorption operation. Thus, the washed and regenerated column can be reused in the metal adsorption operation.

By dehydrating and drying the above separated solid, the volume could be reduced to 0.08 times and the weight could be reduced to 0.16 times, and the volume could be reduced, respectively, as compared with the feedstock.
As also shown in these examples, according to the present invention,
In an aqueous medium, scallop scales are crushed and mixed (for example, homogenized) to elute harmful metals from scale tissue,
By means of contacting the fibrous amidoxime collector, C
Harmful metals such as d can be almost completely removed. The collected Cd and the like can be used as metal resources. Because the content of Cd can be easily reduced to below the standard,
The processing liquid can be discharged as it is. The scallop shell solids to be separated are dehydrated and dried as necessary,
Or, even if it is not performed, a protein source (eg, feed, etc.) as appropriate
And can be safely used as fertilizer.

[Brief description of the drawings]

FIG. 1 is a schematic flow sheet of an embodiment of the method of the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) B09B 3/00 ZAB C02F 1/28 Z 4G035 1/52 Z 4G066 C02F 1/28 B02C 23/08 Z B09B 5 / 00 E 1/52 3/00 ZABZ // B02C 23/08 303H 304H (72) Inventor Takanobu Sugo 1233 Watanukicho, Takasaki City, Gunma Prefecture Japan Atomic Energy Research Institute Takasaki Research Institute (72) Inventor Tomofumi Shiraishi Gunma Prefecture 1233 Watanuki-cho, Takasaki City, Environmental Purification Research Institute, Inc. CA34 CA41 CA42 CA47 CB04 CB13 CB21 CC06 CC20 4D015 BA23 BB05 CA01 CA17 DA08 DA15 DA16 DB12 EA39 FA02 FA03 FA22 FA30 4D024 AA04 A B17 BA17 BB02 BC01 CA01 DA07 DB07 DB21 4D062 BA23 BB05 CA01 CA17 DA08 DA15 DA16 DB12 EA39 FA02 FA03 FA22 FA30 4D067 EE11 EE27 GA14 GB05 4G035 AB46 AB54 AE13 4G066 AD07B BA16 CA46 DA08 FA07 FA11 GA11

Claims (8)

[Claims] 1. A scoured scallop scale is stirred in an aqueous medium to dissolve harmful metals from the ground scallop into an aqueous medium; and a suspended solid content in the aqueous medium is precipitated by a flocculant. Harmful metal-containing aqueous medium after the solid content is separated,
Contacting the fibrous amidoxime collector with the fibrous amidoxime collector prepared by radiation graft polymerization to adsorb the harmful metal to the fibrous amidoxime collector; eluting the harmful metal adsorbed by the fibrous amidoxime collector with dilute acid A method for removing harmful metals from scallop scales, including various steps. 2. The method according to claim 1, wherein the elution of the harmful metal from the ground scallop scales is carried out by homogenizing the scallop scales in the presence of an aqueous medium. 3. The contact between the harmful metal-containing aqueous medium and the fibrous amidoxime collector after the solid content is separated by flowing the aqueous medium through a column filled with the fibrous amidoxime collector. The method according to claim 1 or 2, wherein the method is performed. 4. The fibrous amidoxime trapping material after removing the adsorbed harmful metal by eluting with a dilute acid, washing, neutralizing and regenerating the fibrous amidoxime trapping material, and then adsorbing the harmful metal. The method according to any one of claims 1 to 3, wherein the method is reused. 5. A method for adsorbing and removing harmful metals by arranging a plurality of columns packed with the fibrous amidoxime collector in parallel.
5. The method according to claim 3 or 4, wherein the operation of eluting the adsorbed harmful metal and the preparation operation for regeneration for removing the harmful metal next time are performed in parallel or in a coordinated manner so that the steps can be carried out substantially continuously. 6. The method according to claim 1, wherein hydrochloric acid is used as a dilute acid for eluting harmful metals. 7. The method according to claim 1, wherein the separated solid is dehydrated and taken out of the system. 8. The method according to claim 7, wherein the solid is dehydrated, further dried, and taken out of the system.