PROCESS FOR PURIFYING CAUSTIC SODA LIQUORS

The invention relates to a process for purifying caustic soda liquors resulting from the sodium chloride electrolysis by chemical treatment, in a first step, with an oxidant, preferably sodium persulphate, in a ratio of 5g/l of liquor and hydrated baryta in a ratio of 4g/l of liquor, while stirring for 8...12 hours at the ambient temperature, followed by a second step of treatment with a sodium carbonate solution in a ratio of 40g/l of liquor, under the same temperature conditions while stirring for 4...7 hours. After resting for 10...14 hours, the purified solution is filtered through a glass wool filtering layer. The resulting caustic soda solution has a concentration of 14...45%, varying with the amount of distilled water used in both treatment steps. Inventia se refera la un procedeu de purificare a lesiilor de hidroxid de sodiu, obtinute prin electroliza clorurii de sodiu prin tratare chimica, intr-o prima etapa, cu o substanta oxidanta, de preferinta persulfat de sodiu, in proportie de 5 g/l lesie si hidroxid de bariu in proportie de 4 g/l lesie, sub agitare, timp de 8...12 h, la temperatura camerei, urmata de o a doua etapa de tratare cuo solutie de carbonat de sodiu in proportie de 40 g/l lesie, in aceleasi conditii de temperatura si sub agitare timp de 4...7 h. Dupa 10...14 h de repaus, solutia purificata este filtrata printr-un strat filtrant, format din vata de sticla. Solutia de hidroxid de sodiu rezultata are o concentratie de 14...45%, in functie de cantitatea de apa distilata utilizata in cele doua trepte de tratare.