JPH02203905A - Method for adsorbing and removing heavy metals - Google Patents

Abstract

PURPOSE:To efficiently and selectively remove heavy metals by merely performing contact treatment by adsorbing heavy metals by bringing carbonate mineral into contact with the exudate of industrial waste or raw garbage containing heavy metals under an aerobic condition. CONSTITUTION:Carbonate mineral such as calcite, aragonite, baddeleyite, amorphous calcium carbonate or dolomite is brought into contact with the exudate of industrial waste or raw garbage containing heavy metals under an aerobic condition. By this method, heavy metals such as Hg, Cd, Cd, Fe, Pb or the like are adsorbed by the carbonate mineral. As the aforementioned aerobic condition, a CO2 concn. of 30ppm or less is pref. and 1ppm is more pref. and 3ppm or more is especially pref. When the exudate is brought into contact with the carbonate mineral, the aerobic condition is pref. held by performing aeration in a water diffusion bed or fixed bed.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for adsorbing and removing heavy metals contained in exudate water.

<Prior art> Conventionally, as a method for removing heavy metals such as cadmium and mercury from leachate of industrial or general waste final treatment plants, including industrial wastewater, for example, chelate resins for heavy metals or ion exchange resins have been used. A known method is to adsorb it onto a material such as

However, the chelate resins and ion exchange resins for heavy metals are very expensive and pose an economical problem.

<Problems to be Solved by the Invention> An object of the present invention is to provide a method for easily and efficiently adsorbing and removing heavy metals from exudate water.

<Means for Solving the Problems> According to the present invention, there is provided a method for adsorption and removal of heavy metals, which comprises bringing carbonate minerals into contact with exudate water containing heavy metals under aerobic conditions.

The present invention will be explained in more detail below.

The adsorption removal method of the present invention is characterized by bringing carbonate minerals into contact with exudate water from industrial waste, garbage, etc. under aerobic conditions.

The carbonate mineral used in the present invention can remove heavy metals such as Hg, Cd, Fe, Mn, and Pd in the leachate by contacting it with leachate from an industrial or general waste final treatment plant under aerobic conditions. A substance that can be adsorbed, specifically selected from one or more of the group consisting of calcite, aragonite, vaterite, amorphous calcium carbonate, dolomite, magnesium carbonate, coral, etc. It is particularly desirable to use porous coral having a multilayer structure. The term "coral" is a general term for animals belonging to the family Coralidae, and includes, for example, red coral, white coral, white coral, impana, and sea strawberry.

In the present invention, when the exudate water containing heavy metals is brought into contact with the carbonate mineral, it is necessary to do so under aerobic conditions. At this time, if the carbonate mineral is simply brought into contact with the exudate water, the heavy metals will not be sufficiently adsorbed due to the high concentration of carbon dioxide in the exudate water, and will be re-eluted as bicarbonate. In addition, the leachate immediately after a treatment plant is in service has a high salt concentration, which can suppress the activity of sulfur bacteria, but as the salinity decreases due to long-term operation, the activity of sulfur bacteria increases. , the sulfur content in the leachate oxidizes to produce sulfuric acid. For this reason, the sulfuric acid reacts with the carbonate mineral to produce gypsum or magnesium sulfate, which reduces its function as a carbonate mineral or turns it into a paste, blocking the flow path. Furthermore, under the aerobic conditions mentioned above, it is possible to perform biological treatment of not only one heavy metal but also the leachate water, but if biological treatment and adsorption removal of heavy metals are performed simultaneously, the removal efficiency of heavy metals will decrease. It is preferable to perform biological treatment separately in the pretreatment.

In the present invention, the aerobic conditions are 1, for example, preferably a CO2 concentration of 3 Qppm or less, and more preferably a DO2 concentration of 1 ppm or more, particularly 3 ppm or more. At this time, if the CO2 concentration exceeds 30 ppm, it is not preferable because heavy metals may be eluted as bicarbonate and sulfur bacteria may become active.

In the present invention, in order to maintain aerobic conditions when leachate is brought into contact with carbonate minerals, for example, the water sprinkling bed method or the method of steaming in a fixed bed are used, in other words, the leachate is collected, and after biological treatment or Preferred methods include filling a water spout bed or a tank with carbonate minerals with carbonate minerals, and then circulating or batching the exudate water to generate steam.

In the present invention, the time period for which the carbonate mineral is brought into contact with the exudate water is preferably in the range of 5 minutes to 1 week. In this case, if the contact time is less than 5 minutes, the heavy metals cannot be removed sufficiently, and even if the contact time exceeds 1 week, no improvement in the removal effect can be expected, which is economically undesirable. In this case, the carbonate mineral can be used alone or in combination with, for example, limestone, sand, etc. Furthermore, in the above-mentioned contact method, it is also possible to contact the carbonate mineral in multiple layers.

<Effects of the Invention> The adsorption removal method of the present invention can remove heavy metals at a high rate and selectively by simply bringing the exudate into contact with carbonate minerals under aerobic conditions. very useful.

<Examples> The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Lost Storm■↓ ・20 by-passing the leachate from an industrial waste disposal site that has been landfilled for 8 years, equipped with an aeration pipe at the bottom, and filled with Coral 20, a mixture of calcite and aragonite.
Water was passed through the cmφX100CII+ column at a rate of IQ/min for 8 months. As a result, no gypsumization of coral occurred. Table 1 shows the amounts of heavy metals and DO1CO2 in the leachate at the time of inflow and outflow.

Table 1 The same procedure as in Example 1 was carried out except that a diffuser pipe was not attached to the column. After 8 months, the coral turned into gypsum.
It became paste-like and water could not pass through it.

Hg, C, d, Fe, and Mn as artificial exudate water in the exudate water
1100 pp each and CO2: 300 pp m
The same procedure as in Example 1 was conducted except that artificial exudate water containing . Table 2 shows the quality of the exudate water at the time of the outflow.

As artificial exudate water, Hg, Cd, Fe and Mn are added to exudate water.
Comparative Example] was carried out in the same manner as in [Comparative Example] except that artificial exudate water containing 1100 pp of each was used. Table 2 shows the quality of the exudate water at the time of the outflow.

Table 2 From the above results, it was found that in the examples of the present invention carried out under aerobic conditions, heavy metals could be adsorbed and removed more efficiently than in the comparative examples in which exudate water was simply brought into contact with carbonate minerals. understood.

Claims (1)

[Claims] A method for adsorption and removal of heavy metals, which comprises bringing carbonate minerals into contact with exudate water containing heavy metals under aerobic conditions.