KR100401987B1 - A method for preparing chromic acid from electroplating was tewater including hexavalent chrome - Google Patents

A method for preparing chromic acid from electroplating was tewater including hexavalent chrome Download PDF

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KR100401987B1
KR100401987B1 KR10-1998-0055326A KR19980055326A KR100401987B1 KR 100401987 B1 KR100401987 B1 KR 100401987B1 KR 19980055326 A KR19980055326 A KR 19980055326A KR 100401987 B1 KR100401987 B1 KR 100401987B1
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chromium
sludge
hexavalent chromium
waste liquid
chromic acid
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KR10-1998-0055326A
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Korean (ko)
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KR20000039859A (en
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이훈하
이재영
김대영
손진군
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주식회사 포스코
재단법인 포항산업과학연구원
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G37/00—Compounds of chromium
    • C01G37/02—Oxides or hydrates thereof
    • C01G37/033—Chromium trioxide; Chromic acid
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W10/00—Technologies for wastewater treatment
    • Y02W10/20—Sludge processing
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W10/00—Technologies for wastewater treatment
    • Y02W10/40—Valorisation of by-products of wastewater, sewage or sludge processing

Abstract

본 발명은 6가 크롬함유 폐액으로부터 불순물을 제거하고, 이로부터 크롬산을 제조하는 방법에 관한 것으로,The present invention relates to a method for removing impurities from a hexavalent chromium-containing waste liquid and preparing chromic acid therefrom.

6가 크롬함유 폐액을 여과하여 불용성 불순물을 제거하는 단계;Filtering the hexavalent chromium-containing waste liquid to remove insoluble impurities;

상기 6가 크롬함유하는 폐액중의 2가 철이온을 3가 철이온으로 산화시키는 단계;Oxidizing divalent iron ions in the hexavalent chromium-containing waste liquid to trivalent iron ions;

상기 산화후, 가성소다를 첨가하여 pH를 3∼5로 조절함으로써 3가 철이온 슬러지를 형성하고 형성된 슬러지를 여과하여 제거하는 단계;After the oxidation, by adding caustic soda to adjust the pH to 3 to 5 to form trivalent iron ion sludge and to remove the formed sludge by filtering;

상기 불순물이 제거된 6가 크롬함유 폐액에 황산을 투입하여 용액의 pH를 1∼2로 조절하는 단계;Adding sulfuric acid to the hexavalent chromium-containing waste solution from which the impurities are removed to adjust the pH of the solution to 1 to 2;

pH 조절 후, 환원제를 첨가하여 폐액중의 Cr+6을 Cr+3으로 환원시키는 단계;after pH adjustment, reducing Cr +6 to Cr +3 in the waste liquid by adding a reducing agent;

수산화크롬 슬러지를 형성하도록 가성소다를 첨가하여 pH 7∼11로 중화하는 단계;Neutralizing to pH 7-11 by adding caustic soda to form chromium hydroxide sludge;

상기 수산화크롬 슬러지를 수세, 여과 및 건조하는 단계; 및Washing, filtering and drying the chromium hydroxide sludge; And

상기 수산화크롬슬러지에 수산화크롬과 동일한 당량비로 과산화수소수를 첨가하는 단계;Adding hydrogen peroxide water to the chromium hydroxide sludge in the same equivalent ratio as chromium hydroxide;

를 포함하는 6가 크롬을 함유하는 폐액을 이용한 크롬산 제조방법이 제공된다.Provided is a method for preparing chromic acid using a waste liquid containing hexavalent chromium including.

상기 본 발명의 방법으로 6가 크롬함유 폐액을 이용하여 슬러지문제 없이 크롬산을 제조할 수 있을 뿐만 아니라 제조된 크롬산은 크롬도금용액으로 사용된다.By using the hexavalent chromium-containing waste solution by the above method of the present invention, not only the chromic acid may be prepared without a sludge problem, but the produced chromic acid is used as the chromium plating solution.

Description

6가 크롬 함유 폐액을 이용한 크롬산 제조방법 {A METHOD FOR PREPARING CHROMIC ACID FROM ELECTROPLATING WAS TEWATER INCLUDING HEXAVALENT CHROME}Method for producing chromic acid using hexavalent chromium-containing waste liquid {A METHOD FOR PREPARING CHROMIC ACID FROM ELECTROPLATING WAS TEWATER INCLUDING HEXAVALENT CHROME}

본 발명은 6가 크롬함유 폐액(이하, 단지 '폐액'이라고도 한다.)으로부터 크롬산을 제조하는 방법에 관한 것이며, 보다 상세하게는 6가 크롬 함유 폐액으로부터 불순물을 제거하고, 이로부터 크롬도금용액의 원료로 사용되는 크롬산을 제조하는 방법에 관한 것이다.The present invention relates to a method for producing chromic acid from a hexavalent chromium-containing waste solution (hereinafter also referred to simply as 'waste'), and more particularly, to remove impurities from the hexavalent chromium-containing waste solution, The present invention relates to a method for producing chromic acid used as a raw material.

6가 크롬을 함유하는 폐액은 도금강판 후처리의 일종인 크로메이트 처리시 또는 크롬도금시 발생된다. 또한, 6가 크롬함유 폐액은 염료, 안료, 피혁 제조과정등에서발생된다.The waste liquid containing hexavalent chromium is generated during chromate treatment or chromium plating, which is a kind of post-plated steel sheet treatment. In addition, hexavalent chromium-containing waste liquids are generated during dyeing, pigmenting, and leather manufacturing processes.

종래 이와 같이 발생되는 6가 크롬 함유 폐액은 6가 크롬함유 도금 폐액을 재이용하기 위한 방법의 하나로써 증발 및 농축을 기본으로 하는 크롬회수 방법 등이 일부 사용되고 있으나, 이러한 크롬회수 시스템은 초기 설비 투자비가 높기 때문에 널리 사용되지 못하고 있다.Conventionally, the hexavalent chromium-containing waste liquid generated as described above is partially used as a method for reusing a hexavalent chromium-containing plating waste liquid, but a chromium recovery method based on evaporation and concentration is used. It is not widely used because of its high.

따라서 대부분은 발생되는 6가 크롬함유 도금폐액을 환원처리 후 생석회를 이용하여 중화처리한 후 슬러지화하여 매립하는 방법이 이용되고 있다. 이와 같은 종래의 6가 크롬함유 도금폐액의 처리방법을 도 1에 나타내었다. 즉, 6가 크롬함유 폐액은환원제를 사용하여 환원처리한 후, 생석회를 사용하여 중화시키고 이에 따라 형성되는 슬러지를 매립하는 방법이 이용되어 왔다.Therefore, most of the generated hexavalent chromium-containing plating waste is neutralized by using quicklime after reduction, and then sludged and landfilled. The conventional method for treating a hexavalent chromium-containing plating waste liquid is shown in FIG. 1. That is, the hexavalent chromium-containing waste liquid has been reduced by using a reducing agent, and then neutralized by using quicklime, and a method of landfilling sludge thus formed has been used.

그러나, 이와 같이 생석회를 이용한 중화처리방법은 중화슬러지의 증량문제를 초래할 뿐만 아니라 슬러지를 매립함으로 인하여 심각한 환경 문제를 야기하고 있다.However, the neutralization treatment method using the quicklime not only causes the problem of increasing the amount of neutralized sludge, but also causes serious environmental problems by landfilling the sludge.

이에 본 발명의 목적은 종래의 크롬 회수 시스템에 비하여 보다 경제적으로 6가 크롬을 함유하는 폐액을 재이용하는 방법을 제공하는 것이다.It is therefore an object of the present invention to provide a method for recycling waste liquids containing hexavalent chromium more economically than conventional chromium recovery systems.

본 발명의 다른 목적은 6가 크롬을 함유하는 폐액을 처리함에 있어서, 환원처리 후, 중화제로 생석회를 사용하는 경우에 발생되는 슬러지 처리문제를 해결하는 방법을 제공하는 것이다.Another object of the present invention is to provide a method for solving the problem of sludge treatment generated in the case of using quicklime as a neutralizing agent after the reduction treatment in treating waste liquid containing hexavalent chromium.

본 발명의 또 다른 목적은 6가 크롬함유을 이용하여 크롬산을 제조하는 방법을 제공하는 것이다.Still another object of the present invention is to provide a method for preparing chromic acid using hexavalent chromium.

나아가, 본 발명의 또 다른 목적을 크롬도금용액으로 사용되는 크롬산을 제공하는 것이다.Further, another object of the present invention to provide a chromic acid used as a chromium plating solution.

도 1은 종래의 6가 크롬함유 폐액을 처리하는 방법을 나타내는 공정개략도이며,1 is a process schematic diagram showing a method for treating a conventional hexavalent chromium-containing waste liquid,

도 2는 본 발명의 6가 크롬함유 폐액을 이용한 크롬산 제조방법을 나타내는 공정개략도이다.2 is a process schematic diagram showing a method for producing chromic acid using a hexavalent chromium-containing waste liquid of the present invention.

본 발명에 있어서,In the present invention,

6가 크롬함유 폐액을 여과하여 불용성 불순물을 제거하는 단계;Filtering the hexavalent chromium-containing waste liquid to remove insoluble impurities;

상기 6가 크롬함유 폐액중의 2가 철이온을 3가 철이온으로 산화시키는 단계;Oxidizing divalent iron ions in the hexavalent chromium-containing waste liquid to trivalent iron ions;

상기 산화후, 가성소다를 첨가하여 pH를 3∼5로 조절함으로써 3가 철이온 슬러지를 형성하고 형성된 슬러지를 여과하여 제거하는 단계;After the oxidation, by adding caustic soda to adjust the pH to 3 to 5 to form trivalent iron ion sludge and to remove the formed sludge by filtering;

상기 불순물이 제거된 6가 크롬함유 폐액에 황산을 투입하여 용액의 pH를 1∼2로 조절하는 단계;Adding sulfuric acid to the hexavalent chromium-containing waste solution from which the impurities are removed to adjust the pH of the solution to 1 to 2;

pH 조절 후, 환원제를 첨가하여 폐액중의 6가 크롬을 3가 크롬으로 환원시키는 단계;after adjusting the pH, adding a reducing agent to reduce hexavalent chromium in the waste liquid to trivalent chromium;

수산화크롬(Cr(OH)3) 슬러지를 형성하기 위해 가성소다를 첨가하여 pH 7∼11로 중화하는 단계;Neutralizing to pH 7-11 by adding caustic soda to form chromium hydroxide (Cr (OH) 3 ) sludge;

상기 수산화크롬 슬러지를 수세, 여과 및 건조하는 단계; 및Washing, filtering and drying the chromium hydroxide sludge; And

상기 수산화크롬 슬러지에 수산화크롬과 동일한 당량비로 과산화수소수를 첨가하는 단계;Adding hydrogen peroxide water to the chromium hydroxide sludge in the same ratio as chromium hydroxide;

를 포함하는 6가 크롬함유 폐액을 이용한 크롬산 제조방법이 제공된다.Provided is a method for preparing chromic acid using a hexavalent chromium-containing waste liquid comprising a.

이하, 본 발명에 대하여 상세히 설명한다.EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

본 발명에 의하여, 6가 크롬함유 폐액을 이용함으로써 크롬산을 제조하게 된다.According to the present invention, chromic acid is produced by using a hexavalent chromium-containing waste liquid.

본 발명에 사용되는 6가 크롬을 함유하는 폐액은 도금강판 후처리의 일종인 크로메이트 처리시 발생되는 6가 크롬 폐액 및 크롬 도금시 발생되는 6가 크롬 도금 폐액을 주대상으로 하며, 염료, 안료, 피혁 제조과정에서 발생되는 크롬폐액 또한 적용가능한 것이다.The waste liquid containing hexavalent chromium used in the present invention mainly consists of hexavalent chromium waste liquid generated during chromate treatment, which is a kind of post-plated steel sheet treatment, and hexavalent chromium plating waste liquid generated during chromium plating, and includes dyes, pigments, Chromium waste liquors generated during the leather manufacturing process are also applicable.

상기 6가 크롬함유 폐액을 재활용하기 위해서는 먼저 폐액중의 불순물을 정제하여야 한다. 상기 6가 크롬 도금 폐액에는 SiO2, Sn 금속분말 등의 수용액 불용성 불순물 및 수용액 가용성 불순물이 함유되어 있다. 수용액 가용성 불순물중 특히 철이온등은 목적하는 최종 목적물에 불순물로 존재하여 그 순도등을 저하시킴으로 반드시 제거하여야 하는 것이다.In order to recycle the hexavalent chromium-containing waste liquid, impurities in the waste liquid must first be purified. The hexavalent chromium plating waste liquid contains aqueous solution insoluble impurities such as SiO 2 , Sn metal powder, and aqueous solution soluble impurities. Among the soluble impurities in the aqueous solution, iron ions, etc., must be removed as they exist as impurities in the desired end object and lower the purity.

본 발명에 의한, 6가 크롬함유 폐액으로부터 크롬산을 제조하는 방법을 도 2에 나타내었으며 이를 참조하여 본 발명에 대하여 설명한다.The process for producing chromic acid from hexavalent chromium-containing waste liquid according to the present invention is shown in FIG. 2 and the present invention will be described with reference to this.

도 2에 나타낸 바와 같이 폐액중의 수용액 불용성 불순물은 1차 여과기 여과함으로써 폐액으로부터 간단히 분리, 제거된다. 이와 같이 수용액 불용성 불순물을 제거한 후, 수용액 가용성 불순물, 특히 2가 및 3가 철이온을 제거하게 된다.As shown in Fig. 2, the aqueous solution insoluble impurities in the waste liquid are simply separated and removed from the waste liquid by primary filter filtering. After removing the aqueous solution insoluble impurities, the aqueous solution soluble impurities, in particular divalent and trivalent iron ions, are removed.

2가 철이온 폐액중에 극히 미량으로 존재하며, 이와 같은 2가 철이온은 3가 철이온으로 산화시킨 후 제거한다.It is present in extremely small amounts in the divalent iron ions, and such divalent iron ions are removed after oxidizing to trivalent iron ions.

폐액에 산화제를 첨가함으로써 폐액중의 2가 철이온을 3가 철이온으로 산화시킨다.By adding an oxidizing agent to the waste liquid, divalent iron ions in the waste liquid are oxidized to trivalent iron ions.

상기 산화는 산화제로는 과산화수소를 첨가하거나, 혹은 공기를 버블링하여 Fe+2를 Fe+3로 산화시킨다.The oxidation is performed by adding hydrogen peroxide as an oxidant or by bubbling air to oxidize Fe + 2 to Fe + 3 .

과산화수소를 첨가하여 산화시키는 경우, 첨가되는 과산화수소의 양은 Fe+2가 하기 화학식(1)과 같이 Fe+3으로 산화됨을 고려하여 폐수중에 함유되어 있는 Fe+2와 동일한 당량비로 첨가하는 것이 바람직하다. 과산화수소가 다량 첨가되면, 과산화수소가 6가 크롬을 환원시키는 환원제로도 또한 작용함으로 과산화수소는 Fe+2만을 산화시키기에 충분한 양으로 첨가하는 것이 바람직하다.When oxidizing with hydrogen peroxide, the amount of hydrogen peroxide added to the Fe +2 to Fe +3 oxidation, taking into account that as the formula (1) is preferably added in the same equivalent ratio and the Fe +2 contained in the waste water. When a large amount of hydrogen peroxide is added, it is preferable to add hydrogen peroxide in an amount sufficient to oxidize only Fe +2 since hydrogen peroxide also serves as a reducing agent for reducing hexavalent chromium.

2FeSO4+ H2O2+ H2SO4------> Fe2(SO4)3+ 2H2O2FeSO 4 + H 2 O 2 + H 2 SO 4 ------> Fe 2 (SO 4 ) 3 + 2H 2 O

이와같이 수용성인 Fe+2를 Fe+3으로 산화시킨 후, 도금폐액중에 함유되어 있는 Fe+3를 슬러지화하여 제거한다. 폐액중의 Fe+3를 슬러지화하여 제거하기 위해, 폐액의 pH를 3∼5로 조절한다.In this way, the water-soluble Fe + 2 is oxidized to Fe + 3, and then Fe + 3 contained in the plating waste liquid is sludged and removed. In order to sludge and remove Fe +3 in the waste liquid, the pH of the waste liquid is adjusted to 3-5.

이때, 가성소다를 사용하여 pH를 조절하는 것이 바람직하다. 가성소다를 사용하여pH 3∼5로 조절함으로써 3가 철이온 슬러지가 형성되며, 또한 황산을 기초로한 폐액중의 SO4 -2와 Na+가 반응하여 Na2SO4가 생성되며 Na2SO4는 가용성 물질로수세함으로써 용이하게 제거된다. 그러나, 종래의 6가 크롬함유폐액처리방법에서와 같이 생석회(Ca(OH)2)를 사용하는 경우에는 CaSO4를 형성하며 이는 고형물로서 제거되지 않고 반응도중 불순물로 존재함으로 가성소다를 사용하여 pH를 조절하는 것이 바람직하다.At this time, it is preferable to adjust the pH using caustic soda. By adjusting to pH 3~5 with caustic formed a sludge trivalent iron ions, and is of a waste liquid based on sulfuric acid and SO 4 -2 and Na + is the reaction Na 2 SO 4 is produced Na 2 SO 4 is easily removed by washing with a soluble substance. However, when using quicklime (Ca (OH) 2 ) as in the conventional hexavalent chromium-containing waste treatment method, CaSO 4 is formed, which is not removed as a solid but is present as an impurity in the reaction. It is desirable to control the.

이와 같이 pH를 3∼5로 조절함으로써 3가 철이온은 슬러지를 형성하게 된다.Thus, by adjusting the pH to 3-5, trivalent iron ions form sludge.

pH가 3이하인 경우에는 3가 철이온 슬러지가 형성되지 않음으로 바람직하지 않으며, pH가 5이상인 경우에는 후속공정인 크롬환원처리 전공정에서 폐액의 pH를 낮추기위해 다량의 황산을 첨가하여야 함으로 또한 바람직하지 않은 것이다.If the pH is 3 or less, it is not preferable because no trivalent iron ion sludge is formed, and if the pH is 5 or more, it is also preferable to add a large amount of sulfuric acid to lower the pH of the waste liquid in the subsequent process of chromium reduction treatment. I haven't.

형성된 3가 철이온 슬러지는 도 2에 나타낸 바와 같이 2차 여과기를 사용하여 제거한다.The trivalent iron ion sludge formed is removed using a secondary filter as shown in FIG. 2.

이와 같이 도금폐수내에 함유되어 있는 수용액 불용성 및 가용성 불순물을 제거한 후, 폐수를 환원처리하게 된다.Thus, after removing the aqueous solution insoluble and soluble impurities contained in the plating waste water, the waste water is reduced.

환원처리에 앞서 불순물이 제거된 순수한 6가 크롬을 함유하는 폐액의 pH를 1∼2로 조절한다. 이때 6가 크롬을 함유하는 폐액 자체가 황산을 기초로한 폐액임으로 황산을 이용하여 pH를 조절하는 것이 다른 불순물등이 유입되지 않는 것으로 바람직한 것이다.Prior to the reduction treatment, the pH of the waste liquid containing pure hexavalent chromium from which impurities are removed is adjusted to 1-2. At this time, since the waste solution containing hexavalent chromium itself is a waste solution based on sulfuric acid, it is preferable to adjust pH using sulfuric acid so that no other impurities are introduced.

폐액의 pH를 강산 영역, 즉, pH 1∼2로 조절함으로써, 6가 크롬을 3가 크롬으로 환원처리하는 경우, 환원효율 및 환원속도가 증대된다.When the pH of the waste liquid is adjusted to a strong acid range, that is, pH 1 to 2, when the hexavalent chromium is reduced to trivalent chromium, the reduction efficiency and the reduction rate are increased.

폐액의 pH를 1∼2로 조절한 후, 환원제를 첨가하여 6가 크롬을 3가 크롬으로 환원시킨다. 이 때 환원제로는 NaHSO3, Na2S2O5및 SO2가 사용된다. 이때 사용되는 환원제의 첨가량은 산화환원전위 측정법 또는 폐액 중 6가 크롬의 농도를 분석하여 6가 크롬의 당량에 대하여 1∼1.5배의 당량비로 첨가하는 것이 바람직하다.After adjusting the pH of the waste liquid to 1-2, the reducing agent is added to reduce the hexavalent chromium to trivalent chromium. In this case, NaHSO 3 , Na 2 S 2 O 5, and SO 2 are used as reducing agents. In this case, the amount of the reducing agent used may be added at an equivalent ratio of 1 to 1.5 times the equivalent of hexavalent chromium by analyzing the redox potential measurement method or analyzing the concentration of hexavalent chromium in the waste liquid.

동일한 당량비 이하에서는 6가 크롬이 충분히 3가 크롬으로 환원되지 않으며, 1.5배 이상의 당량비로 첨가하더라도 더 이상의 환원이 일어나지 않음으로 환원제를 1∼1.5배의 당량비로 첨가하는 것이 바람직하다.Below the same equivalent ratio, hexavalent chromium is not sufficiently reduced to trivalent chromium, and even if it is added in an equivalent ratio of 1.5 times or more, no further reduction occurs, so it is preferable to add a reducing agent in an equivalent ratio of 1 to 1.5 times.

이와같이 환원제를 사용하여 도금폐액중의 6가 크롬을 3가 크롬으로 환원시킨 후, 폐액을 중화시킨다. 이 때 상기 3가 철이온 슬러지를 형성하기 위해 pH를 조절하는 경우와 동일한 이유로 가성소다를 사용하여 중화시키는 것이 바람직하며, 또한, pH 7∼11로 중화하는 것이 좋다. pH 7이하에서는 환원된 3가 크롬이 완전히 침전하지 않으며, pH 11이상에서는 형성된 크롬 슬러지 Cr(OH)3가 이온으로 재용해됨으로 pH 7∼11로 조절하는 것이 바람직하다.In this way, the hexavalent chromium in the plating waste liquid is reduced to trivalent chromium by using a reducing agent, and then the waste liquid is neutralized. At this time, it is preferable to neutralize using caustic soda for the same reason as in the case of adjusting the pH to form the trivalent iron ion sludge, and to neutralize to pH 7-11. Below pH 7, the reduced trivalent chromium is not completely precipitated, and at pH 11 or above, it is preferable to adjust the pH to 7-11 because red chromium sludge Cr (OH) 3 is redissolved with ions.

이와같이 중화처리된 슬러지내에는 중화시 생성되는 Na2SO4가 포함되어 있으며, 이는 물로 수세함으써 제거된다. 따라서 형성된 수산화크롬 슬러지(Cr(OH)3)를 수세 및 여과하여 Na2SO4를 제거한다.The neutralized sludge contains Na 2 SO 4 produced during neutralization, which is removed by washing with water. The formed chromium hydroxide sludge (Cr (OH) 3 ) is then washed with water and filtered to remove Na 2 SO 4 .

그후, 형성된 Cr(OH)3중화슬러지를 건조한 후, 이에 강산화제인 과산화수소수를 첨가하면, Cr(OH)3와 과산화수소수는 하기 화학식 2의 반응에 의하여 6가 크롬산이 형성된다.Thereafter, the formed Cr (OH) 3 neutralized sludge is dried, and when hydrogen peroxide solution, which is a strong oxidizer, is added thereto, hexavalent chromic acid is formed by reacting Cr (OH) 3 with hydrogen peroxide solution.

2Cr(OH)3+ 3H2O2----------> 2CrO3+ 6H2O2Cr (OH) 3 + 3H 2 O 2 ----------> 2CrO 3 + 6H 2 O

이 때 첨가되는 과산화수소수는 Cr(OH)3와 동일한 당량비 첨가한다.The hydrogen peroxide solution added at this time is added in the same equivalent ratio as Cr (OH) 3 .

첨가되는 과산화수소수의 양이 Cr(OH)3에 대하여 동일한 당량비미만으로 첨가되면, Cr(OH)3의 불완전한 산화로 수산화크롬 슬러지가 잔존하며, 동일한 당량비 이상으로 첨가되면, 형성되는 크롬산내에 과산화수소수가 잔존하게 됨으로 바람직하기 않은 것이다.When the amount of the hydrogen peroxide solution is added Cr (OH) is added below the same equivalent ratio relative to 3, if the Cr (OH), and chromium hydroxide sludge is left in an incomplete oxidation of 3, was added over the same equivalent ratio, the number of hydrogen peroxide in the chromic acid is formed It is not desirable to remain.

이와 같이 과산화수소수를 첨가하여 수산화크롬을 산화시킴으로써 크롬산을 형성하며, 그 후, 잔류물을 여과한다. 여과후, 잔류물은 과산화수소수를 이용하는 산화반응에 재투입된다.Thus, hydrogen peroxide solution is added to oxidize chromium hydroxide to form chromic acid, and the residue is then filtered. After filtration, the residue is reintroduced into an oxidation reaction using hydrogen peroxide water.

상기한 바와 같은 방법에 의해서 6가 크롬 함유 폐액으로부터 크롬산이 제조되며, 이와 같이 제조된 크롬산은 크롬도금용액으로 이용된다.The chromic acid is prepared from the hexavalent chromium-containing waste liquid by the method as described above, and the chromic acid thus prepared is used as the chromium plating solution.

이하, 본 발명의 실시예에 대하여 상세히 설명한다.Hereinafter, embodiments of the present invention will be described in detail.

실시예 1Example 1

본 실시예에서는 6가 크롬함유 도금폐액중에 존재하는 수용액 불용성 및 수용성 불순물을을 제거하는 정제공정조건을 달리하면서 폐액내의 불순물 정제여부를 조사하였으며, 그 결과를 하기 표 1에 나타내었다.In this embodiment, the purification of impurities in the waste solution was examined while varying the purification process conditions for removing aqueous solution insoluble and water-soluble impurities present in the hexavalent chromium-containing plating waste, and the results are shown in Table 1 below.

(발명예 1 및 2)(Invention Examples 1 and 2)

발명예 1 및 2에서는 6가 크롬함유 도금폐액중의 불용성 불순물을 1차 여과기로여과처리한 후, 용액내의 2가 철이온의 당량비만큼 과산화수소를 투입하여 2가 철이온을 산화시켰다. 그 후, 폐액에 가성소다를 첨가하여 용액의 pH를 각각 3.5 및 4.5로 유지하여 3가 철이온이 충분히 응집하여 슬러지화되도록 하였다. 그 후, 3가 철이온의 슬러지를 2차 여과기로 여과하여 제거하였다.In Inventive Examples 1 and 2, the insoluble impurities in the hexavalent chromium-containing plating waste were filtered with a primary filter, and then hydrogen peroxide was added in an amount equivalent to the amount of divalent iron ions in the solution to oxidize the divalent iron ions. Thereafter, caustic soda was added to the waste liquid to maintain the pH of the solution at 3.5 and 4.5, respectively, so that trivalent iron ions were sufficiently aggregated and sludged. The sludge of trivalent iron ions was then removed by filtration with a secondary filter.

이와 같이 폐액중에서 불순물을 제거한 후, 황산을 투입하여 pH 1로 조절하고 6가 크롬함량과 동일한 당량비로 NaHSO3환원제를 투입하여 6가 크롬을 환원시켰다.Thus, after removing impurities from the waste liquid, sulfuric acid was added to adjust the pH to 1, and NaHSO 3 reducing agent was added to reduce the hexavalent chromium at the same equivalent ratio as the hexavalent chromium content.

환원처리된 용액에 가성소다를 첨가하여 pH 9로 중화처리하였으며, 그 후 수세, 여과하여 알카리성분을 제거하고 슬러지내의 성분을 분석하였다.Caustic soda was added to the reduced solution and neutralized to pH 9, followed by washing with water and filtration to remove alkali and analyzed the components in the sludge.

중화된 슬러지 즉, Cr(OH)3에서는 철이온 불순물이 검출되지 않았으며, 따라서 Cr(OH)3슬러지를 사용하여 크롬산을 제조할 수 있는 것이다.Iron ion impurities were not detected in the neutralized sludge, that is, Cr (OH) 3 , and therefore, chromic acid can be prepared using Cr (OH) 3 sludge.

(비교예 1)(Comparative Example 1)

비교예 1에서는 불용성 불순물 제거공정 및 가용성 불순물인 철이온제거공정을 거치지 않고 도금폐액에 황산을 투입하여 pH 1로 조절하고 6가 크롬과 동일한 당량비 만큼 NaHSO3환원제를 투입하여 6가 크롬을 환원시켰다.In Comparative Example 1, sulfuric acid was added to the plating waste solution to adjust pH 1 without going through the process of removing insoluble impurities and iron ions as soluble impurities, and reduced the hexavalent chromium by adding NaHSO 3 reducing agent in the same equivalent ratio as hexavalent chromium. .

그 후의 처리공정은 상기 발명예 2와 동일하게 처리하였다.Subsequent treatment processes were performed in the same manner as in Inventive Example 2.

형성된 수산화크롬 슬러지내의 성분을 분석한 결과, 하기 표 1에 나타낸 바와 같이, Sn등의 불용성 불순물 및 철이온등의 가용성 불순물이 존재하며, 이와 같은 불순물이 존재함으로 인하여 의도하는 크롬산을 제조할 수 없었다.As a result of analyzing the components in the formed chromium hydroxide sludge, as shown in Table 1, there are insoluble impurities such as Sn and soluble impurities such as iron ions, and the intended chromic acid could not be prepared due to such impurities. .

(비교예 2)(Comparative Example 2)

도금폐액중의 불용성 불순물을 제거한 다음 폐액내의 2가 철이온과 동일한 당량비로 과산화수소수를 투입하여 2가 철이온을 산화시킨 후, 가성소다를 사용하여 pH를 2로 유지하였으며, 그 이외의 처리는 발명예 2와 동일하게 처리하였다.After removing the insoluble impurities in the plating waste liquid, hydrogen peroxide water was added at the same ratio as the divalent iron ions in the waste liquid to oxidize the divalent iron ions, and the pH was maintained at 2 using caustic soda. It processed similarly to invention example 2.

폐액의 pH를 2로 유지한 결과, 3가 철이온 슬러지가 생성되지 않았으며, 후속 공정인 크롬 환원후 중화시 철이온이 슬러지화됨으로 이를 이용하여 크롬산을 제조하는 경우, 철이온이 크롬산과 함께 불순물로 존재하며, 따라서 최종물인 크롬산의 순도에 악영향을 미치게 됨으로 바람직하지 않은 것이다.As a result of maintaining the pH of the waste solution at 2, no trivalent iron ion sludge was formed, and iron ions were sludged upon neutralization after chromium reduction. It is undesirable because it is present as an impurity and thus adversely affects the purity of the final chromic acid.

(비교예 3)(Comparative Example 3)

폐액중의 수용액 불용성 불순물을 제거한 다음, 2가 철이온을 산화시키지 않고 폐액에 가성소다를 첨가하여 폐액의 pH만을 3.5로 유지하여 슬러지를 형성한 후, 형성된 3가 철이온슬러지를 여과처리하였다. 그 이외의 처리는 발명예 2와 동일하게 처리하였다.After removing the aqueous solution insoluble impurities in the waste liquid, caustic soda was added to the waste liquid without oxidizing divalent iron ions to maintain the pH of the waste liquid at only 3.5 to form sludge, and then the formed trivalent iron ion sludge was filtered. Treatment other than that was processed similarly to invention example 2.

본 비교예에서는 3가 철이온은 제거되나, 2가 철이온은 제거되지 않고 후속공정인 환원 및 중화시 슬러지중에 철이온 성분이 검출되었으며, 이를 이용한 크롬산제조시에도 Fe+2불순물의 존재로 인하여 그 순도등에 악영향을 미치게 된다.In this comparative example, trivalent iron ions are removed, but divalent iron ions are not removed, and iron ions are detected in the sludge during the subsequent reduction and neutralization, and due to the presence of Fe +2 impurities in the production of chromic acid using the same, It will adversely affect the purity.

(비교예 4)(Comparative Example 4)

2가 철이온을 3가 철이온으로 산화시킨후, 3가 철이온의 슬러지 형성시, 가성소다를 투입하여 용액의 pH를 5.5로 유지한 것을 제외하고는 발명예 2와 동일하게 처리하였다.After oxidizing divalent iron ions to trivalent iron ions, when treating the sludge of trivalent iron ions, the same treatment as in Inventive Example 2 was carried out except that caustic soda was added to maintain the pH of the solution at 5.5.

본 비교예에서와 같이 pH를 5이상으로 유지하는 경우에는 후속공정인 환원공정전단계에서 환원효율을 향상시키기 위해 pH를 1∼2로 조절할 때 다량의 황산을 첨가하여야 함으로 바람직하지 않은 것이다.When the pH is maintained at 5 or more as in this comparative example, it is not preferable because a large amount of sulfuric acid should be added when the pH is adjusted to 1-2 in order to improve the reduction efficiency in a subsequent step before the reduction process.

구분division 불순물 처리법Impurity Treatment 비 고Remarks 발명예 1Inventive Example 1 불용성 불순물 여과처리후,H2O2를 Fe+2이온 당량비 만큼 투입후,pH 3.5 유지After insoluble impurity filtration treatment, H 2 O 2 was added as much as Fe + 2 ion equivalent ratio, and pH was maintained at 3.5. 불순물 제거 양호Good removal of impurities 발명예 2Inventive Example 2 불용성 불순물 여과처리후,H2O2를 Fe+2이온 당량비 만큼 투입후,pH 4.5 유지After insoluble impurity filtration treatment, H 2 O 2 was added in the ratio of Fe + 2 ion equivalent ratio, and the pH was maintained at 4.5. 불순물 제거 양호Good removal of impurities 비교예 1Comparative Example 1 불순물 처리공정 없음No impurity treatment Sn등 불용성 불순물 및 Fe불순물 처리불가Insoluble impurities such as Sn and Fe impurities cannot be processed 비교예 2Comparative Example 2 불용성 불순물 여과처리후,H2O2를 Fe+2이온 당량비 만큼 투입후,pH 2 유지After insoluble impurity filtration treatment, H 2 O 2 was added in the ratio of Fe + 2 ion equivalent ratio, and the pH was maintained. Fe+3이온 처리불가Fe +3 ion treatment not possible 비교예 3Comparative Example 3 불용성 불순물 여과처리후,2가 철이온의 산화단계 없음, pH 3.5 유지After insoluble impurity filtration, there is no oxidation step of divalent iron ions, maintained at pH 3.5 미량의 Fe+2이온처리불가Small amount of Fe +2 ion treatment 비교예 4Comparative Example 4 불용성 불순물 여과처리후,H2O2를 Fe+2이온 당량비 만큼 투입후,pH 5.5 유지After insoluble impurity filtration treatment, H 2 O 2 was added as much as Fe + 2 ion equivalent ratio, and the pH was maintained at 5.5. 황산 원료 손실 발생Sulfuric acid raw material loss

실시예 2Example 2

본 실시예는 6가 크롬의 환원처리 후, 가성소다를 이용한 pH 조절시, pH가 크롬산제조반응에 미치는 영향을 알아보기 위한 것이다.This example is to determine the effect of pH on the chromic acid production reaction during pH adjustment using caustic soda after reduction treatment of hexavalent chromium.

본 실시예에서는 상기 실시예 1의 발명예 2와 같이 도금폐액내의 불순물을 제거하였다. 폐액내의 6가 크롬과 동일한 당량비로 NaHSO3를 첨가하여 환원처리한 후, 가성소다를 첨가하여 수산화크롬 슬러지가 형성되도록 중화시키는 경우, pH를 하기 표 2에 나타낸 바와 같이 조절한 것을 제외하는 실시예 1의 발명예 2와 같이 처리하였으며, 그 결과를 하기 표 2에 나타내었다.In this embodiment, impurities in the plating waste liquid were removed as in Example 2 of Example 1. After the reduction treatment by adding NaHSO 3 in the same equivalent ratio of hexavalent chromium in the waste solution, and then neutralizing the addition of caustic soda to form chromium hydroxide sludge, except that the pH was adjusted as shown in Table 2 below Treatment was carried out as in Inventive Example 2, and the results are shown in Table 2 below.

(발명제 3 및 4)(Invention 3 and 4)

하기 표 2에 나타낸 바와 같이, pH를 7내지 11로 유지한 발명예 3 및 4의 경우, 환원된 3가 크롬이 100% 슬러지화 되었다.As shown in Table 2 below, for Inventive Examples 3 and 4, wherein the pH was maintained between 7 and 11, the reduced trivalent chromium was 100% sludged.

(비교제 5 및 6)(Comparative 5 and 6)

하기 표 2의 비교예 5에서와 같이 도금 폐액의 pH가 6인 경우에는 환원용액중 크롬의 슬러지화율이 90%로 바람직하지 않았으며, 또한, 비교예 6에서와 같이 도금폐액의 pH를 11이상으로 조절하면, 슬러지화율이 80%로 저조할 뿐만 아니라, 중화된 크롬 침전물 슬러지인 Cr(OH)3의 일부가 재용해됨으로 바람직하지 않은 것이다.When the pH of the plating waste solution was 6 as shown in Comparative Example 5 in Table 2, the sludge ratio of chromium in the reducing solution was not preferable as 90%, and the pH of the plating waste solution was 11 or more as in Comparative Example 6. When adjusted to, not only is the sludge rate lowered to 80%, but also some of the neutralized chromium precipitate sludge Cr (OH) 3 is redissolved, which is undesirable.

구 분division 중화시 용액의 pHPH of solution upon neutralization 환원용액중 Cr의 슬러지화율(%)Sludge rate of Cr in reducing solution (%) 발명예 3Inventive Example 3 pH=7pH = 7 100%100% 발명예 4Inventive Example 4 pH=11pH = 11 100%100% 비교예 5Comparative Example 5 pH=6pH = 6 90%90% 비교예 6Comparative Example 6 pH=12pH = 12 80%/ Cr(OH)3의 일부 재용해Some redissolution of 80% / Cr (OH) 3

실시예 3Example 3

본 실시예는 형성된 수산화크롬 슬러지에 과산화수소수첨가시, 과산화수소수의 첨가량이 크롬산 생성에 미치는 효과는 알아보기 위한 것이다.This embodiment is to determine the effect of the addition amount of hydrogen peroxide on the production of chromic acid when hydrogen peroxide is added to the formed chromium hydroxide sludge.

불순물이 제거된 6가 크롬함유 폐액을 환원시키고, 중화처리하여 수산화크롬 슬러지를 제조하고, 수세, 여과 및 건조한 후, 이에 첨가되는 과산화수소의 양을 하기 표 3에서와 같이 조절한 것을 제외하고는 실시예 1의 발명예 2과 같이 처리하였으며, 그 결과를 하기 표 3에 나타내었다.The hexavalent chromium-containing waste solution from which impurities were removed was reduced, neutralized to produce chromium hydroxide sludge, and washed with water, filtered and dried, except that the amount of hydrogen peroxide added thereto was adjusted as shown in Table 3 below. Treatment was carried out as inventive example 2 of Example 1, the results are shown in Table 3 below.

하기 표 3의 발명예 5와 같이 Cr(OH)3와 H2O2가 동일한 당량비로 존재하는 경우,When Cr (OH) 3 and H 2 O 2 are present in the same equivalent ratio as in Inventive Example 5 of Table 3,

Cr(OH)3수산화크롬 슬러지가 100% 크롬산으로 전환되었다.Cr (OH) 3 chromium hydroxide sludge was converted to 100% chromic acid.

이에 반하여, 비교예 1과 같이 Cr(OH)3에 대한 과산화수소수의 화학량론적인 몰당량비가 0.8인 경우, Cr(OH)3의 불완전한 산화로 Cr(OH)3중화슬러지가 잔존하는 문제가 있으며, 비교예 8과 같이 Cr(OH)3에 대한 과산화수소수의 화학량론적인 몰당량비가 1을 초과하는 경우에는 과량의 과산화수소수를 사용함으로 인한 과산화수소수의 손실뿐만 아니라 형성된 크롬산내에 과산화수소수가 잔존하게 됨으로 바람직하지 않은 것이다.On the other hand, Comparative Example 1 Cr as (OH) If the stoichiometric molar equivalent ratio of the number of hydrogen peroxide for 3 0.8, Cr (OH), and a problem that Cr (OH) 3 neutralization sludge remaining in an incomplete oxidation of the 3 When the stoichiometric molar equivalence ratio of hydrogen peroxide to Cr (OH) 3 exceeds 1 as in Comparative Example 8, not only the loss of hydrogen peroxide water due to the use of excess hydrogen peroxide water, but also the hydrogen peroxide water remains in the formed chromic acid. It is not desirable.

구 분division Cr(OH)3에 대한 H2O2의화학량론적인 당량비Stoichiometric equivalence ratio of H 2 O 2 to Cr (OH) 3 비 고Remarks 발명예 5Inventive Example 5 1One 비교예 7Comparative Example 7 0.80.8 Cr(OH)3의 불완전산화로 슬러지 잔존Sludge Remains from Incomplete Oxidation of Cr (OH) 3 비교예 8Comparative Example 8 1.21.2 ① 과잉의 과산화수소수 사용으로인한 과산화수소수의 손실② 크롬산내에 과산화수소 잔류① Loss of hydrogen peroxide due to excessive use of hydrogen peroxide ② Residual hydrogen peroxide in chromic acid

이와 같이 본 발명에 의한 방법으로 6가 크롬함유 폐액을 이용하여 크롬산을 제조할 수 있을 뿐만 아니라, 종래 6가 크롬함유 폐액을 환원시킨 후, 생석회로 중화처리하는 경우 발생하는 슬러지 처리 문제를 해결하는 것이다. 또한, 상기 제조된 크롬산은 크롬도금용액으로 사용된다.As described above, not only the chromic acid can be prepared using the hexavalent chromium-containing waste liquid by the method of the present invention, but also the sludge treatment problem occurring when the conventional hexavalent chromium-containing waste liquid is reduced and then neutralized with quicklime. will be. In addition, the prepared chromic acid is used as a chromium plating solution.

Claims (3)

6가 크롬을 함유하는 폐액을 여과하여 불용성 불순물을 제거하는 단계;Filtering the waste liquid containing hexavalent chromium to remove insoluble impurities; 산화제로 과산화수소 혹은 공기를 사용하여 상기 6가 크롬을 함유하는 폐액중의 2가 철이온을 3가 철이온을 산화시키는 단계;Oxidizing trivalent iron ions to trivalent iron ions in the waste liquid containing hexavalent chromium using hydrogen peroxide or air as an oxidant; 상기 산화후, 가성소다를 첨가하여 pH를 3∼5로 조절함으로써 3가 철이온의 슬러지를 형성하고 형성된 슬러지를 여과하여 제거하는 단계;After the oxidation, by adding caustic soda to adjust the pH to 3 to 5 to form a sludge of trivalent iron ions and to remove the formed sludge by filtering; 6가 크롬을 함유하는 폐액에 황산을 투입하여 용액을 pH를 1∼2로 조절하는 단계;Adding sulfuric acid to a waste solution containing hexavalent chromium to adjust the solution to a pH of 1 to 2; pH 조절 후, NaHSO3, Na2S2O5및 SO2가스로 구성된 그룹으로부터 선택된 최소 하나의 환원제를 6가 크롬산의 당량에 대하여 1~1.5의 당량비로 첨가하여 폐액중의 6가 크롬을 3가 크롬으로 환원시키는 단계;After pH adjustment, at least one reducing agent selected from the group consisting of NaHSO 3 , Na 2 S 2 O 5, and SO 2 gas was added in an equivalent ratio of 1 to 1.5 with respect to the equivalent of hexavalent chromic acid to form hexavalent chromium in the waste solution. Reducing to chromium; 수산화크롬(Cr(OH)3) 슬러지를 형성하기 위해 가성소다를 첨가하여 pH 7∼11로 중화하는 단계;Neutralizing to pH 7-11 by adding caustic soda to form chromium hydroxide (Cr (OH) 3 ) sludge; 상기 수산화크롬슬러지를 수세, 여과 및 건조하는 단계; 및Washing, filtering and drying the chromium hydroxide sludge; And 상기 수산화크롬 슬러지에 수산화크롬과 동일한 당량비로 과산화수소수를 첨가하는 단계;Adding hydrogen peroxide water to the chromium hydroxide sludge in the same ratio as chromium hydroxide; 를 포함하는 6가 크롬을 함유하는 폐액을 이용한 크롬산 제조방법.Chromic acid production method using a waste solution containing hexavalent chromium containing. 제 1항에 있어서, 상기 산화제로서 과산화수소는 6가 크롬을 함유하는 폐액중에 존재하는 2가 철이온과 동일한 당량비로 폐수중에 첨가함을 특징으로 하는 방법.The method according to claim 1, wherein the hydrogen peroxide as the oxidizing agent is added to the waste water in the same equivalent ratio as the divalent iron ions present in the waste liquid containing hexavalent chromium. 크롬도금용액으로 사용되는 청구항 1항의 방법에 의하여 제조된 크롬산.Chromic acid prepared by the method of claim 1 used as a chromium plating solution.
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US3961029A (en) * 1973-05-21 1976-06-01 Tokico Ltd. Process for recovering chromic acid solution from a waste liquor containing chromic ions
JPS5632329A (en) * 1979-08-18 1981-04-01 Kitaoosaka Seisou Kk Treatment of chromic acid waste liquid
EP0316487A1 (en) * 1987-11-16 1989-05-24 Norman B. Hjersted A process of preparing ferric sulfate solution
EP0433748A1 (en) * 1989-12-16 1991-06-26 Bayer Ag Process for the preparation of chromic acid
JPH03164433A (en) * 1989-11-22 1991-07-16 Toda Kogyo Corp Production of jarosite particles

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US3961029A (en) * 1973-05-21 1976-06-01 Tokico Ltd. Process for recovering chromic acid solution from a waste liquor containing chromic ions
JPS5632329A (en) * 1979-08-18 1981-04-01 Kitaoosaka Seisou Kk Treatment of chromic acid waste liquid
EP0316487A1 (en) * 1987-11-16 1989-05-24 Norman B. Hjersted A process of preparing ferric sulfate solution
JPH03164433A (en) * 1989-11-22 1991-07-16 Toda Kogyo Corp Production of jarosite particles
EP0433748A1 (en) * 1989-12-16 1991-06-26 Bayer Ag Process for the preparation of chromic acid

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