SU1318535A1 - Method for electrochemical treatment of waste water - Google Patents

Abstract

The process for electrochemically purifying waste waters comprises passing the waste water through membrane electrolysis cells (2, 16), the separate draining of catholyte and anolyte and their subsequent blending, and the removal of the purified waste waters. According to the invention, the separately drained anolyte and catholyte are obtained in the membrane electrolysis cell (16) using soluble electrodes (17, 18), in particular electrodes made of aluminium, anolyte and catholyte being fed in parallel out of the membrane electrolysis cell (2) containing insoluble electrodes into the anode and cathode space (14 and 15, respectively) of the membrane electrolysis cell (16) containing soluble electrodes (17, 18). <IMAGE>

Description

The invention relates to wastewater treatment using soluble electrodes and can be used to clean wastewater on ships.

The purpose of the invention is to reduce the energy consumption for carrying out the process by eliminating the formation of precipitation on the electrodes.

Example. The treated wastewater is supplied in parallel streams to the anode and cathode chambers of a diaphragm electrolyzer with graphite electrodes. From the anodic and cathodic chambers, the flows are respectively supplied to the anodic and cathodic chambers of a diaphragme electrolyzer with aluminum electrodes.

When electrolysis is carried out, a current of 45 A is applied to soluble electrodes and 55 A to insoluble electrons. The flow of effluent through the electrolyzer is 1000 l / h. Every 30 minutes a polarity reversal of both pairs of electrodes is carried out in both electrolysers.

First, the diaphragm electrolyzer with soluble electrodes serves wastewater without supplying a current to the electrolyzer with insoluble electrodes, the incoming drains have a pH of 7-8, and a current of 5 mA / cm is passed through aluminum electrodes.

The effluent from the anode space has a pH of 4.3-4.5, and from the ca. One space is pH 9.1–9.3. Re-polarity is performed every 30 minutes. In this case, a loose sediment is formed on the surface of the electrodes. A qualitative analysis of this precipitate on an infrared spectrophotometer shows that it consists of aluminum hydroxide mixed with magnesium hydroxide. After 30–40 hours of operation, the sediment almost completely kills the anode and cathode spaces. At the termination of the electrolyzer on dissolveTable 1

.рн, ° io ,, i

. The presence of (+) + no (-) layer of hydroxides on the electrode

five

Aluminum electrodes are observed to corrode them to form a precipitate mainly from aluminum hydroxide.

When passing waste water only through a diaphragm electrolyzer with insoluble electrodes (with a disconnected diaphragm electrolyzer with soluble electrodes) at a current density of 4 mA / cm, the wastewater has a pH of 2.9 and from the cathode space of pH 11, one. In this case, a white precipitate is formed on the cathode, the analysis of which shows that it consists mainly of MgCOH). When the polarity changes, the deposit from the surface of the electrode dissolves.

Thus, when only soluble electrodes are operated in a diaphragm electrolyzer with soluble electrodes, a deposit is formed on the surface of the latter, which prevents electrochemical treatment of wastewater, and a precipitate also forms on the surface of graphite electrodes when the electrolyzer is not polarized. electrodes.

The data obtained when the alkaline alkaline electrolytic cell and the anodic acid wastewater are fed into the cathode chamber of the diaphragm electrolyzer are given respectively in Table. 1 and 2.

The tests at each pH value of 35 are carried out for 20 hours, after an optical test, the presence of a hydroxide layer on the electrodes is determined.

The data show that feed in

0

five

0

40

45

The cathode chamber of sewage with a pH of 10.1, and in the anodic chamber with, 5, leads to the elimination of sediment on the electrodes, which ensures stable operation of the apparatus — eliminates the increase in voltage on it, i.e., removes energy consumption for the process.

Table 1

 ° io ,, i

ph i d i i i

+ + + + +

Claims (1)

METHOD FOR ELECTROCHEMICAL WASTE WATER TREATMENT, including the supply of wastewater in parallel streams into the anode and cathode chambers of a diaphragm electrolyzer using soluble electrodes with their subsequent mixes i, characterized in that, in order to reduce energy consumption by eliminating the formation of precipitation on the electrodes, before feeding in the anode and cathode chambers of the electrolyzer with soluble electrodes, the flow is treated respectively in the anode and cathode chambers of the diaphragm electrolyzer with insoluble electrodes s until reaching pH 3.0-3.5 anolyte and catholyte 10,1-10,6. SU, ", 1318535