Electrolysis of sodium sulfate

However, disposal will become increasingly difficult, if not impossible, in the near future due to tighter environmental regulations. In any case, it will certainly become increasingly expensive and for this reason, at least, the recovery by electrolysis of sodium sulfate—and in general of other neutral salts, such as sodium nitrate and sodium chloride, which are also generated in some chemical processes—is expected to have a bright future. 

The electrolysis of sodium sulfate is a much-studied process for production of caustic soda without chlorine. When Na2S04 electrolyzes in a divided cell, oxygen and hydrogen form at the anode and cathode, leaving H+ and OH in the respective compartments. Dilute solutions of sulfuric acid and caustic soda form by the reactions... 

Sulfuric Acid 120 49 — — E E produced from electrolysis of sodium sulfate solution. Product of SO scrubbing. 1.0 N H S0 with 17% Na S04, 218 days... 

For the recoveiy of thallium from the flue dust of pyrite burners, the dust is boiled with H2O, allowed to stand some time, filtered, and HC1 added to die filtrate, whereupon crude thallous chloride is precipitated. This is purified by further treatment, and thallium metal obtained (1) by electrolysis of the sulfate solution or (2) by fusion of the chloride widi sodium cyanide and carbonate. 

Hydrochloric acid is a convenient acid for laboratory-scale electrolysis it is easy to remove during the workup by evaporation. The oxygen-containing acids, such as sulfuric or perchloric acid, must be neutralized before basic products can be extracted. Sulfuric acid is most conveniently neutralized by concentrated ammonia rather than by sodium hydroxide, whereby the precipitation of sodium sulfate is avoided. 

In addition to the reduction of sodium sulfate, an electrolysis process is operated in which a sodium polysulfide solution (from sodium sulfide solution and... 

The following example deals with the electrolysis of an aqueous solution of sodium sulfate (Na2S04). 

Substantial savings of money, which otherwise would have been required for disposal of by-product salts. In the specific case of sodium sulfate, electrolysis becomes economically interesting when the disposal cost of the salt is in the order of 100 per tonne, with a caustic soda price in the range of 200 per tonne. 

Figure 101. Flow diagram of sodium sulfate electrolysis in two-compartment electrolyzers (production of acid sodium sulfate, oxygen-evolving anodes)...

Figure 103. Flow diagram of sodium. sulfate electrolysis in three-compartment electrolyzers (bufler compartment) MC = Cation-exchange membrane...

As a purely indicative example, an electrolysis plant based on three-compartment cells is considered, having a capacity of3000 t/a of sodium sulfate (100 % basis) fed to the cells as a 20 % solution The investment for a doubleeffect evaporation unit represents about 10-15% of the total investment for the complete plant, comprising cells, rectifier, pretreatment unit, evaporation, and construction. The cost of steam amounts to about 50% of the total electric energy cost. 

With a porous diaphragm, it is difficult to achieve efficient separation of the acidic anolyte from the alkaline catholyte. The result is a significant loss of current efficiency. Also, the choice of a diaphragm resistant to both sulfuric acid and caustic soda and the selection of an anode stable in sulfuric acid solution are limited. These difficulties have retarded the development of sodium sulfate electrolysis. 

An effluent stream of 3 m /h containing 7.6 gd of sodium sulfate at 20 C is treated in a hybrid process reverse osmosis for concentration and production of clean process water and membrane electrolysis for the conversion of sodium sulfate into sulfuric acid (15%) and caustic soda which is used for neutralisation. 

The question arises as to whether the formation of organometallic compounds during electrolysis of aqueous solutions of acrylonitrile is not due to cyanoethylation of hydrides formed initially at the electrode. In Table 5 data on the electrochemical reduction of tin, sulfur, selenium, and tellurium in aqueous solutions of sodium sulfate with and without acrylonitrile are compared [40]. 

Oxygen can be produced from water by electrolysis using sodium sulfate, sulfuric acid, or sodium hydroxide as the electrolyte. At least 500 mg. of water are required for each analysis, even using specially designed microelectrolytic cells, and the method has no advantage over equilibration, except for analyses. 

NC13, mw 120.38, N 11.64% yel, vol, pungent-smelling oil, mp <-40° (Porret in 1813 reported —27°), bp about 71° (explds at 93-95°), d 1.653g/cc. Sol in cold w (decompd by hot w), ale, eth, chlf, bz, CCl CS2 phosphorous oxychloride. Prepd (with great care) by the action of sodium hypochlorite on amm chloride. The compd also forms at the anode in the electrolysis of coned amm chioride soln. Another prepn consists of bubbling chlorine into a cooled aq soln of amm sulfate di-n-butyl ether (Refs 1,... 

A mixture of water/pyridine appears to be the solvent of choice to aid carbenium ion formation [246]. In the Hofer-Moest reaction the formation of alcohols is optimized by adding alkali bicarbonates, sulfates [39] or perchlorates. In methanol solution the presence of a small amount of sodium perchlorate shifts the decarboxylation totally to the carbenium ion pathway [31]. The structure of the carboxylate can also support non-Kolbe electrolysis. By comparing the products of the electrolysis of different carboxylates with the ionization potentials of the corresponding radicals one can draw the conclusion that alkyl radicals with gas phase ionization potentials smaller than 8 e V should be oxidized to carbenium ions [8 c] in the course of Kolbe electrolysis. This gives some indication in which cases preferential carbenium ion formation or radical dimerization is to be expected. Thus a-alkyl, cycloalkyl [, ... 

Electrolysis of aqueous solutions of the following using inert electrodes sodium chloride, copper(n) sulfate, sodium sulfate and sodium hydroxide. 

Calculate the time required to produce 2.50 g of hydrogen by the electrolysis of water (containing sodium sulfate to carry the charge) with a current of 5.00 A. 

The electrolysis of water, shown in Figure 16, leads to the overall reaction in which H2O is broken down into its elements, H2 and O2. Pure water does not have enough ions in it and is not conductive enough for electrolysis. An electrolyte, such as sodium sulfate, must be added. The Na (a ) and SO aq) ions play no part in the electrode reactions, which are as follows ... 

Into the cell is then placed a solution of 15 g. sodium sulfate. 15. g. boric acid and 14 g. of salicylic acid (0.1 mole), just neutralized with the calculated amount of sodium hydroxide. The solution is then diluted to, 175 cc. All the boric acid not dissolve in this quantity of solution, but is kept in suspension by means of rapid mechanical stirring. The cell is placed in a cooling mixture, and when the temperature reaches 15° to 18° the current is turned on. A temperature of 15° to 18° is maintained throughout the experiment. A current of 3 amp. (6 amp. per sq. dm.) is then passed through the solution for a period of 1 hr. 55 min., which is slightly more than the calculated amount (5.4 amp.-hr.) necessary to reduce the salicylic acid to salicylic aldehyde. During the electrolysis 20 g. sodium bisulfite are added at the rate of about 1.5 g. every 10 min. It has been found best not to begin the addition of the sodium bisulfite until the electrolysis has been started about 5 min, since the bisulfite reduced to sulfur when added to soon, or too rapidly thereafter. 

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