工業(yè)廢水氧化還原法
Wastewater oxidation-reduction method: the toxic and harmful substances dissolved in wastewater are converted into new non-toxic and harmless substances through oxidation-reduction reaction. This wastewater treatment method is called wastewater oxidation-reduction method. In the redox reaction, toxic and harmful substances are sometimes used as reducing agents, which requires additional oxidants, such as air, ozone, chlorine, bleaching powder, sodium hypochlorite, etc. When toxic and harmful substances are used as oxidants, reducing agents such as ferrous sulfate, ferrous chloride and zinc powder are needed. If electrified electrolysis, the anode is an oxidant and the cathode is a reducing agent.
藥劑氧化
Chemical oxidation
廢水中的有毒有害物質(zhì)為還原性物質(zhì)，向其中投加氧化助劑，將有毒有害物質(zhì)氧化成無毒或毒性較小的新物質(zhì)，此種方法稱為藥劑氧化法。在廢水處理中用的最多的藥劑氧化法是氯氧化法，即投加的藥劑為含氯氧化物如液氯、漂白粉等，其基本原理都是利用產(chǎn)生的次氯酸根的強(qiáng)氧化作用。
The toxic and harmful substances in wastewater are reductive substances. Adding oxidation aids to them can oxidize the toxic and harmful substances into new non-toxic or less toxic substances. This method is called reagent oxidation method. Chlorine oxidation is the most commonly used chemical oxidation method in wastewater treatment, that is, chlorine containing oxides such as liquid chlorine and bleaching powder are added. Its basic principle is to use the strong oxidation of hypochlorite.
氯氧化法常用來處理含氰廢水，國(guó)內(nèi)外比較成熟的工藝是堿性氯氧化法。在堿性氯氧化法處理反應(yīng)中，pH值小于8.5則有放出劇毒物質(zhì)氯化氰的危險(xiǎn)，一般工藝條件為：廢水pH值大于11，當(dāng)氰離子濃度高于100mg/L時(shí)，最好控制在pH=12～13。在此情況下，反應(yīng)可在10～15min內(nèi)完成，實(shí)際采用的20～30min。該處理方法的缺陷是雖然氫酸鹽毒性低，僅為氰的千分之一。但產(chǎn)生的氰酸鹽離子易水解生成氨氣。因此，需讓次氯酸將氰酸鹽離子進(jìn)一步氧化成氮?dú)夂投趸迹杷猁}對(duì)環(huán)境的污染同時(shí)進(jìn)一步氧化殘余的氯化氰。在進(jìn)一步氧化氰酸鹽的過程中，pH值值控制是至關(guān)重要的。pH值大于12，則反應(yīng)停止，pH值7.5～8.0，用硫酸調(diào)節(jié)pH值，反應(yīng)過程適當(dāng)攪拌以加速反應(yīng)的完全進(jìn)行。
Chlorine oxidation process is often used to treat cyanide containing wastewater, and the mature process a
t home and abroad is alkaline chlorine oxidation process. When the pH value is less than 8.5, cyanide chloride will be released. The general process conditions are as follows: the pH value of wastewater is more than 11, and when the concentration of cyanide ion is higher than 100mg / L, it is best to control the pH value at 12-13. In this case, the reaction can be completed in 10-15 minutes, and the actual reaction time is 20-30 minutes. The drawback of this treatment method is that although the toxicity of hydrogenate is low, it is only one thousandth of that of cyanide. But the cyanate ion is easy to hydrolyze to produce ammonia. Therefore, it is necessary for hypochlorite to further oxidize cyanate ions into nitrogen and carbon dioxide to eliminate the environmental pollution caused by cyanate and further oxidize the residual cyanogen chloride. In the process of further oxidation of cyanate, the control of pH value is very important. When the pH value is higher than 12, the reaction stops. The pH value is 7.5-8.0. Adjust the pH value with sulfuric acid, and properly stir the reaction process to accelerate the complete reaction.臭氧氧化
Ozonation
臭氧氧化法是利用臭氧的強(qiáng)氧化能力，使污水（或廢水）中的污染物氧化分解成低毒或無毒的化合物，使水質(zhì)得到凈化。它不僅可降低水中的BOD、COD，而且還可起脫色、除臭、除味、殺菌、殺藻等功能，因而，該處理方法愈來愈受到人們重視。
Ozone oxidation method is to use the strong oxidation ability of ozone to oxidize and decompose the pollutants in sewage (or wastewater) into low toxic or non-toxic compounds, so as to purify the water quality. It can not only reduce the BOD and COD in water, but also decolorize, deodorize, deodorize, sterilize and kill algae. Therefore, people pay more and more attention to this treatment method.
藥劑還原與金屬還原
Chemical reduction and metal reduction
藥劑還原法是利用某些化學(xué)藥劑的還原性，將廢水中的有毒有害物質(zhì)還原成低毒或無毒的化合物的一種水處理方法。常見的例子是用硫酸亞鐵處理含鉻廢水。亞鐵離子起還原作用，在酸性條件下（pH值=2～3），廢水中六價(jià)鉻主要以重鉻酸根離子形式存在。六價(jià)鉻被還原成三價(jià)鉻，亞鐵離子被氧化成鐵離子，需再用中和沉淀法將三價(jià)鉻沉淀。沉淀的污染物是鉻氫氧化物和鐵氫氧化物的混合物，需要妥善處理，以防二次污染。該工藝流程包括集水、還原、沉淀、固液分離和污泥脫水等工序，可連續(xù)操作，也可間歇操作。
Chemical reduction is a kind of water treatment method which uses the reducibility of some chemicals to reduce the toxic and harmful substances in wastewater into low toxic or non-toxic compounds. A common example is the treatment of chromium containing wastewater with ferrous sulfate. Ferrous ions play a reducing role. Under acidic conditions (pH = 2-3), hexavalent chromium in wastewater mainly exists in the form of dichromate. Hexavalent chromium is reduced to trivalent chromium, ferrous ion is oxidized to ferric ion, and trivalent chromium is precipitated by neutralization precipitation method. The precipitated pollutant is a mixture of chromium hydroxide and iron hydroxide, which needs to be properly treated to prevent secondary pollution. The process includes water collection, reduction, sedimentation, solid-liquid separation and sludge dewatering, which can be operated continuously or intermittently.
金屬還原法是向廢水中投加還原性較強(qiáng)的金屬單質(zhì)，將水中氧化性的金屬離子還原成單質(zhì)金屬析出，投加的金屬則被氧化成離子進(jìn)入水中。此種處理方法常用來處理含重金屬離子的廢水，典型例子是鐵屑還原處理含汞廢水。其中鐵屑還原效果與水中pH值有關(guān)，當(dāng)水中pH值較低時(shí)，鐵屑還會(huì)將廢水中氫離子還原成氫氣逸出，因而，當(dāng)廢水的pH值較低時(shí)，應(yīng)調(diào)節(jié)后再處理。反應(yīng)溫度一般控制在20℃～30℃。
Metal reduction method is to add metal elements with strong reducibility into the wastewater, reduce the oxidizing metal ions in the water to elemental metal precipitation, and the added metal is oxidized into ions into the water. This treatment method is often used to treat wastewater containing heavy metal ions. A typical example is the reduction treatment of mercury containing wastewater by iron filings. The reduction effect of iron filings is related to the pH value of the water. When the pH value of the water is low, the iron filings will also reduce the hydrogen ion in the wastewater into hydrogen and escape. Therefore, when the pH value of the wastewater is low, it should be adjusted before treatment. The reaction temperature is generally controlled between 20 ℃ and 30 ℃.