SU1634642A1 - Method of separating hexavalent chromium from sewage - Google Patents

Abstract

The invention relates to the electrochemical treatment of waste water from hexavalent chromas. The purpose of the invention is to reduce energy consumption with a decrease in sediment volume. titanium dioxide, and a block of soluble iron electrodes, the surface of the electrodes in the blocks being equal and the process is carried out while maintaining a density of 0.5-1.0 A / dm2 - on soluble Å crocs and 1.9-5.0 A / dm4 on non-soluble „2 tabl s SS (/) s:

Description

The invention relates to the electrochemical treatment of wastewater containing heavy metal ions, such as hexavalent chromium ions, and can be used in the treatment of wastewater from electroplating industries of the metalworking, machine-building and other industries.

The purpose of the invention is to reduce energy consumption and decrease the volume of sediment.

Example 1 o Waste water is pumped with a content of hexafluoride chromium of 50 mg / l at a pH of 1.3-1.7 per round electrolyzer of the vertical type, in which a section of electrodes Ti - TDA or Ti - ORTA is placed with a speed of 20 l / and voltage is applied to the electrodes. At a current density of i 1.4 A / dm2, the residual hexavalent chromium content in the waste water as a result of purification is 30 mg / l (the removal of gaesthivalent chromium is 40 XC

Example 2. Pumped waste water with a hexavalent chromium content of 50 mg / l at a pH of 1.3-1.7 through a vertical-type electrolyzer in which two sections of electrode plates are placed, one Ti — ORTA or Ti — TDA, and the other steel plates, each section of electrodes connected to a separate power source. At a pumping rate of water of 20 l / h, the current density on the titanoS5 CO Ј O 4 Yu

ia 1.9 A / dm output electrodes and current densities on steel plates i 0.5 A / dmg hexavalent chromium as a result of cleaning is completely absent (removal of hexavalent chromium is 100%). 36 A, h / l, electrode iron consumption is 0.072 g / l, the amount of suspended matter (sediment after neutralization of waste water is 540 mg / l (pH 7 of waste water is reached by treatment with 10% sodium hydroxide solution) 0

PRI me R 3 (phototype) Sewage water with a hexavalent chromium content of 50 mg / l at pH 4-5 is pumped through an electrolyzer of a vertical type, in which a section of chromium hexavalent steel is placed (with its content in the treated waste water 10 - 80 mg / l) of insoluble anodes from lead and graphite showed that the recovery process proceeds inefficiently (the yield on Cr3 + is only 15-20%) and the creation of a purification apparatus in this case is inappropriate,

Application as insoluble anodes of ORTA, TDA makes it possible to intensify the process (the yield in Cr reaches 40–50%) „

The application of this method, where in combination with a block of insoluble electrodes (Ti - ORTA, Ti - TDA) is used a block of iron electrodes, to which a very small amount is applied.

The plate is connected to the source of 20 Kova load (current density 0.5 supply and served more tightly. At a water pumping rate of 20 l / h and a current density of 3.2 A / dm (hexavalent chromium in the waste water as a result of cleaning is completely absent removal of hexavalent chromium is 100%) "The consumption of electricity in this case is 0.48 A t h / l, the consumption of iron is 0.5 g / l, the amount of substances sprinkled in the neutralized waste water (pH 7) is 1260 mg / l

The data from the above examples are summarized in Table 1.

From the data of the panel 1, it can be seen that the amount of precipitate formed as a result of the purification of the proposed method decreases by almost 2.5 pasat. Moreover, the precipitate formed by using titanium electrodes has a denser structure, its compaction and filtration rate is 1.5 times higher. than precipitation, obtained as a result of water treatment using only steel electrodes. All this significantly increases the operating efficiency of the equipment of the sewage treatment plant and the subsequent processing and disposal of sludge. In addition, the cleaning efficiency is increased by reducing the cost of the electrode material — steel.

Purification efficiency is increased due to the fact that the wastewater is pre-treated on a block of insoluble electrodes to reduce hexavalent chromium to trivalent electrodes.

thirty

35

1.0 A / dm2-) makes it possible to achieve a 100% yield with little electricity (90 - 120 Ah-m / m of treated wastewater) and a small amount of electrode iron (up to 50 g / m) of the treated wastewater0 This does not necessitate the addition of iron in the form of salts: the trivalent iron necessary for the complete reduction of chromium hexavalent to chromium goes into solution by dissolving the iron anodes in a minimum amount.

The results of a series of experiments are presented in tab.

The use of a current with a density below 1.9 A / dm2 on insoluble electrodes and 0.5 A / dm2 on soluble does not lead to the required degree of purification, and an increase in current density above 5.0 A / dm2 and 1.0 A / dm2, respectively, leads to energy waste

Claims (1)

45 claims A method for treating wastewater from hexavalent chromium, which includes supplying water for electrochemical processing using a block of soluble iron electrodes, characterized in that, in order to reduce energy consumption and reduce sludge volume, the treatment is carried out using an additional block of insoluble electrodes containing titanium cathodes and anodes made of titanium or its alloy and coated with ruthenium dioxide or two40 50 55 load (current density 0.5 1.0 A / dm2-) makes it possible to achieve a 100% yield with little electricity (90 - 120 Ah-m / m of treated wastewater) and a small amount of electrode iron (up to 50 g / m) of the treated wastewater0 This does not necessitate the addition of iron in the form of salts: the trivalent iron necessary for the complete reduction of chromium hexavalent to chromium goes into solution by dissolving the iron anodes in a minimum amount. The results of a series of experiments are presented in tab. The use of a current with a density below 1.9 A / dm2 on insoluble electrodes and 0.5 A / dm2 on soluble ones does not lead to the achievement of the required degree of purification, and an increase in current density above 5.0 A / dm2 and 1.0 A / dm2 accordingly leads to energy waste 45 claims A method for treating wastewater from hexavalent chromium, which includes supplying water for electrochemical treatment using a block of soluble iron electrodes, characterized in that, in order to reduce energy consumption and reduce the volume of sludge, the treatment is carried out using an additional block of insoluble electrodes containing titanium cathodes and anodes made of titanium or its alloy and covered with ruthenium dioxide or two five manganese oxide, the areas of soluble and insoluble electrodes are the same and the block of insoluble electrodes is placed under the block of soluble electrodes, and the treatment is carried out at a current density on insoluble Order 730 Circulation 630 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology CC1L 1.13035, Moscow, Zh-35, 4/5 Raushsk nab. electrodes 1.9-5.0 A / dm, on soluble electrodes — 0.5-1.0 A / dm, and the water is supplied in such a way that water is passed through the unit of insoluble and soluble electrodes, Table 1 Subscription