SU715508A1 - Method of waste water purification from arsenic - Google Patents

Description

(54) METHOD FOR CLEANING WASTEWATER FROM ARZYAK

1 The invention relates to the treatment of sewage from the mouse, in particular, the sewage treatment of enterprises of the semiconductor industry by electrochemical treatment. A known method for cleaning the discharge of condensate aggregates of the tin plant at the tin plant by electrochemical treatment of wastewater with a pH of 4-7.9 in a hatch with iron electrodes and a diaphragm made of fabric l. Electricity consumption is 24 O-72 O Ah / l. The method allows to reduce the concentration of arsenic 10-2 O-0, 05 mg / l. The disadvantage of this method is that in the process of electrochemical treatment up to 10 ~ 2 O about my type is lost in the form of current of a scinog arsin gas. There is also known a method for purifying waste water from mice by electrochemical treatment with a soluble iron anode and a cathiacal diaphragm at an anodic current density of 0.9-2 A / dm and a pH of 1.5-3.5, followed by neutralization with lime. The method makes it possible to reduce the concentration of the mouse from 535 mg / l to 1.6 mg / l t2l. The disadvantage of the method is the high consumption of iron 24.2 kg / m) and electricity, in addition, cleaning from the mouse to the maximum permissible concentration is not achieved (the concentration is not permissible). The purpose of the invention is to control the degree of wastewater treatment from an elemental and soluble three and five-vial mouse. This goal is achieved by the fact that electrolytic processing of solutions with a soluble iron anode is carried out at an anodic current density of 0.080,2 A / dm, pH 7-8, temperature 256 ° C and contact time of 10-25 minutes. Cleaning with the use of such parameters reduces the consumption of iron and eliminates the incidence of arsia, and also contributes to the sedimentation of fine particles. 37 The essence of the method is based on the fact that the pH of the waste water is adjusted to 7-8 by neutralization, and then during electrochemical processing at a certain pH, a certain current density and temperature, the mouse is agitated and suspended. As a result of the process, the wastewater is thoroughly cleaned from the mouse and its compounds. In addition, as a result of the easily filtered precipitation, the vrets of filtration is reduced and the number of Cleanings of filter cloths is reduced. The specified parameters are dictated by the following process conditions: The process is carried out at current densities O, 08-O, 2 A / dm I At current densities below O, O8, cleaning is achieved to sanitary standards. An increase in the current density is impractical, since it increases the consumption of electricity and iron, and the residual content of the ka-ion remains the same; The process is carried out with the duration of the contact. min With a shorter contact time, cleaning up to MPC is not achieved. Increasing the contact time is impractical because of the high consumption of electricity and iron. The temperature range of 25-6 ° C is due to the fact that at temperatures below 25 ° C, iron consumption and anode voltage increase, which leads to an increase in energy consumption. Together with this, the degree of settling of suspended particles worsens. Increasing the atura rate above is impractical due to the additional cost of water heating. During electrochemical treatment of wastewater with an initial pH below 7, arsine is released; at pH more than 8.0, purification to MPC is not achieved. The method is carried out by following the region .--- ----; -,. - - - - - - Sewage water with an initial content of 1–2O mg / l, extracting 6O – 5OO mg / l, including elemental As. and pH 7, O-8.0 in addition to la aLectroscheer with a silver anode. A direct current source is connected and electrolysis is carried out for 10-25 minutes at a current density of O, O8-O, 2 A / dm. Popuzhuyu PUZhPU 6 stand for an hour and filter. The filtrate is discarded, and the precipitate, which contains mouse and iron, is sent for disposal. The residual content of mouse is 1Ps in fIettrat mg / l, pH 7-8. :: 8 Example 1. Sewage water containing 5.5 mg / l mouse with a pH of 7.5 at 25 ° C is passed through an electrolytic cell with a circulation rate of 13 l / h and contact time of 25 minutes at varying density of current (tab. 1). I. In the range of the current density of 0.08 O, 02 A / dm, wastewater treatment is achieved from mice to ionic sanitary water (0, O5 mg / l and below). When the current density is below 0.08 A / dm, the cleaning to MPC is not achieved. A further increase in current density is not advisable, as the consumption of iron and electricity increases, and the residual content of the mouse remains the same. Example 2, Sewage water containing 5.5 mg / l mouse with a pH of 7.6 at 25 s is passed through an electrolyzer with a circulation rate of 13 l / h at a current density of 0.12 A / dm. Suspended / residual residual content of mouse to ion on contact time (Table 2) Optimal contact time is 1025 minutes. With a shorter contact time, cleaning to the MPC is not achieved. The increase in time is impractical because of the high consumption of iron and electricity, Example 3. Sewage water containing 5.5 MP / l mouse with a pH of 7.5 was passed through an electrolyzer with a circulation rate of 13 l / h for 15 minutes The current density was 0.2 A / dm, and the temperature cut of the treatment varied (Table 3). The optimum temperature range is 25-6 ° C, since at this temperature the solution is clarified by 90% within 1 hour. At temperatures below 25 ° C, iron consumption increases and sterility of Hb particles settling deteriorates. Temperatures above 60.C are impractical due to the additional cost of heating water. If the waste water was not subjected to electrochemical processing, it was not clarified for 2 days. The sedimentation of wastewater containing mt to allows for complete purification of the mouse by borbhsh mouse kion and iron hydroxide; the residual content of 0, O5 mg / l, which corresponds to the MPC (in the prototype, the residual content of the mouse k-ion exceeds the MAC by 30 times), the formation of arsine is excluded due to the maintenance of a certain

57155086

pH of the solution, as well as saving reagents. mouse to water from 24 2 kg to lime to neutralize, in addition, OD kg and power consumption with reduced iron consumption for cleaning 1m / 4.5 kWh / m 0.7 kW pass / m I

Contact time, min

five

10 25 35

45

Table 1

Table 2

Residual mouse content, mg / l

0.1 0.05 0.025 0.025 0.025

Table 3

Claims (1)

Claim The method of purification of wastewater from arsenic by electrochemical treatment with a soluble iron anode, characterized in that, in order to increase the degree of wastewater treatment from elemental and soluble tri- and pentavalent arsenic, the process is carried out at a current density of 0.08-0.2 A / dm, pH 7-8, temperature 25-60 ° С and contact duration 10-25 min.