JPH09299962A - Treatment of waste water containing lead ton - Google Patents

Abstract

PROBLEM TO BE SOLVED: To separate lead ion as a insoluble material and to remove lead ion in waste water without generating a poisonous gas at the time of treating the waste water contg. lead ion by controlling the pH of the waste water to a specified value and then adding a specified amt. of calcium silicate. SOLUTION: When a waste water contg. lead ion is treated, the waste water is controlled to pH 5.6-12, and then calcium silicate is added in 75:1 weight ratio to the lead to separate the lead ion as the insoluble material. In this case, CaSiO3 , Ca2 SiO4 , etc., are preferably used as the calcium silicate. Any conventionally used alkali or mineral acid capable of controlling the pH to 5.6-12 can be used without any restriction. Consequently, the waste water is safely treated without using a sulfiding agent, etc., which generates highly toxic gas.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a treatment method for separating and removing lead ions as insoluble matter from wastewater containing lead ions.

[0002]

2. Description of the Related Art Conventionally, a neutralization precipitation method or a sulfurization precipitation method has been generally adopted as a method for treating wastewater containing lead ions. However, when the neutralization precipitation method is used, lead ions precipitate at pH 9.5, but since the precipitation pH range is extremely narrow, there is the problem that pH control of wastewater is extremely difficult. , PH of drainage
Since it is only necessary to add a sulfiding agent after adjusting the value to 3.5 or more, the pH adjustment range is wide and the pH control of the wastewater is easy.
This is not preferable because it requires complicated equipment for degassing toxic gas or dissolved gas generated by decomposition of the sulfiding agent charged into the waste water.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in treating wastewater containing lead ions, and the lead ions in the waste water are at a risk of generating toxic gas. It is an object of the present invention to provide a treatment method capable of insolubilizing and separating in a wide pH range without using any additive having properties.

[0004]

Means for Solving the Problems The present invention for achieving the above-mentioned object is to provide a method for treating lead ion-containing wastewater,
After adjusting the pH of the waste water to be between 5.6 and 12, lead ions are separated as insoluble matter by adding calcium silicate in an amount of 75 times as much as lead by weight or more. This is the method for treating the wastewater contained.

Preferred calcium silicates that can be used in the present invention are CaSiO ₃ , Ca ₂ SiO _{4 and the} like, and as a pH adjuster, a commonly used alkali or mineral acid may be used. The value is not particularly limited as long as the value can be adjusted between 5.6 and 12.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail based on the experimental examples conducted by the present inventor. Examination experiment of influence of pH value In this experiment, lead ion concentration was 2.7 mg as wastewater treatment liquid.
/ L was used. Pour 500 ml of this waste water into a reaction vessel equipped with a stirrer (1 l beaker) and p while stirring.
Ca (OH) 2 _was added so that the H value could take various values. After confirming that the change in pH value almost disappeared and the predetermined value was stably maintained, CaSiO ₃ was added to 1
Add 15 mg (CaSiO ₃ /Pb=85.2), 6
After continuing stirring for 0 minutes, the produced insoluble matter was subjected to solid-liquid separation to obtain a treatment completed liquid, and then the concentration of lead ions in the treatment completed liquid was quantified. The results obtained are shown in Table 1.

[0007]

[Table 1] Sample pH value Pb ion concentration of the final solution Number (mg / l) ───────────────────────────── 1 5. 31 0.18 2 5.62 0.08 3 6.15 0.03 4 7.64 0.02 5 9.87 0.01 6 11.94 0.02 ─────────── ─────────────────

Experiment on influence of addition of calcium silicate Also, using the same wastewater treatment liquid as above, the wastewater of 500 m
1 into a reaction container similar to the above, Ca (OH) ₂ was added so that the pH value became 6.1 while stirring the waste water, and after confirming that the pH value did not change, CaS
iO ₃ was added while changing the amount in the range of 60 mg to 120 mg with stirring, and the stirring was continued for 60 minutes, then the generated insoluble matter was subjected to solid-liquid separation to obtain a treatment completed liquid, and the lead in the treatment completed liquid was obtained. The concentration of ions was measured. Table 2 shows the obtained results.

[0009]

[Table 2] Sample pH value CaSiO ₃ CaSiO ₃ Pb number (mg / l) / Pb ratio in the final solution Ion concentration (mg / l) ─────────────────── ───────────────── 7 6.11 60 44.4 2.40 8 6.17 70 51.9 0.68 9 6.14 85 63.0 0.36 10 6.10 100 74.1 0.11 11 6.18 110 81.5 0.05 12 6.12 120 88.9 0.02 ────────────────── ────────────────────

From the results shown in Tables 1 and 2, the precipitation rate of lead ions from the lead ion-containing wastewater is determined by the pH value of the wastewater and the C value.
It can be seen that it depends on the addition amount of aSiO ₃ .
Then, in order to reduce the amount of lead ions in the wastewater to the standard value of the wastewater or less, after adjusting the pH value of the wastewater to the range of 5.6 to 12, CaSiO ₃ is added in an amount 75 times as much as the lead by weight or more. It turns out that it is desirable to do. On the other hand, even if calcium silicate such as CaSiO ₃ is added in an amount 90 times as much as that of lead in terms of weight ratio, the precipitation rate of lead ions is not further improved, and this value is the upper limit of the addition amount. The reason why the precipitation rate of lead ions is improved by adding calcium silicate to the wastewater after pH adjustment is not fully clear, but some of calcium in calcium silicate is replaced with lead ions. It is thought that this is due to things.

[0011]

Next, an embodiment of the present invention will be described.

Example 1: Drainage of a chloride solution containing sodium containing lead ions of 7.3 mg / l 1000
After adjusting the pH value to 8.32 by adding NaOH to ml, 580 mg of CaSiO ₃ was added. Then, the mixture was stirred for 30 minutes, and the produced precipitate was separated to obtain a treatment completed liquid. When the lead ion concentration in the liquid of the finished liquid was measured, it was found to be 0.06 mg / l, which sufficiently satisfied the wastewater standard value.

Example 2 C was added to 500 ml of drainage of a sulfate solution having a pH value of 4.5 containing lead ion of 1.1 mg / l.
After adjusting the pH value to 11.05 by adding a (OH) ₂ , 51 mg of Ca ₂ SiO ₄ was added. Then, the mixture was stirred for 75 minutes, and the generated precipitate was separated to obtain a treatment completed liquid. When the lead ion concentration in the liquid of the finished liquid was measured, it was found to be 0.01 mg / l, which was sufficiently satisfied with the drainage standard value.

[0014]

As described above, according to the treatment method of the present invention, when treating the wastewater containing lead ions, after adjusting the pH value of the wastewater to the range of 5.6 to 12,
By adding calcium silicate in an amount 75 times or more that of lead by weight, lead ions can be insolubilized and easily separated and removed. When the method of the present invention is used, the adjustment range of the pH value of the wastewater for precipitating lead ions is wide without using a sulfiding agent or the like that generates highly toxic gas, and the adjustment is easy. Not only can it be performed, but zinc ions, iron (II) ions, and the like can also be simultaneously removed as insoluble matter in this pH value range, and therefore its utility value as a wastewater treatment method is high.

Claims (1)

[Claims] 1. When treating wastewater containing lead ions,
After adjusting the pH of the waste water to be between 5.6 and 12, lead ions are separated as insoluble matter by adding calcium silicate in an amount of 75 times as much as lead by weight or more. Wastewater treatment method contained.