CS242349B1 - A method of isolating palladium from wastewater after catalytic hydrogenation - Google Patents

Abstract

The solution relates to a method of isolating palladium from waste water containing palladium after catalytic hydrogenation, whereby waste water chemically treated to a pH value of less than 6 is treated with a water-soluble salt of 2-mercaptobenzthiazole in the presence of a coagulation agent, and the precipitate containing palladium is separated by known methods. The method can be used in the chemical industry.

Description

(54) Method for the isolation of palladium from wastewater after catalytic hydrogenation

The present invention relates to a process for the isolation of palladium from palladium-containing effluents after catalytic hydrogenation, wherein the effluents chemically adjusted to a pH of less than 6 are treated with a water-soluble salt of 2-mercaptobenzothiazole in the presence of a coagulant.

The method can be used in the chemical industry.

The invention relates to a process for the isolation of palladium from waste water after catalytic hydrogenation using a palladium-containing catalyst, by precipitation of a water-soluble salt of 2-mercaptobenzothiazole followed by separation of the resulting precipitate using a coagulant.

Palladium finely dispersed on various types of supports, which may be activated carbon SiO 2, CaCO 3, is a frequently used industrial catalyst used in various organic syntheses. As reaction products, respectively. For example, in the reaction mixture, there may be substances in the reaction mixture which act by releasing the palladium from the carrier and converting it to a soluble form in the form of a complex. This soluble part of the palladium cannot then be separated from the liquid phase when the catalyst is separated and the palladium escapes in the waste water.

Because of the ability of palladium to form complexes with the organic substances they contain! different functional groups (NO, SH, oximes) this risk is relatively high. Such precious metal losses have a significant impact on the entire production economy.

Existing processes for recovering palladium from wastewater when applied to organically contaminated wastewater have several drawbacks.

The disadvantage of using ethylenediamine-modified glycidyl methacrylate-ethylene dimethacrylate as a selective ion exchange resin is clogging of the sorbent by precipitated organic impurities, low sorbent capacity, high cost, and cost-effectiveness in its application. The precipitation of palladium through amocomplexes is also ineffective in this case and similar results are obtained with the use of sodium sulfide as a precipitant. The use of special analytical precipitants on an industrial scale is economically disadvantageous.

Due to the fact that it is a relatively large amount of waste Sciences of low palladium ^(_e order of 10%) is separating the resulting precipitate difficult to filter and pumping equipment.

It has now been found that the above disadvantages are overcome by the method of recovering palladium from the waste leaders of the invention.

SUMMARY OF THE INVENTION The waste water chemically adjusted to pH < 6 is treated with a water-soluble salt of 2-mercaptobenzothiazole in the presence of a coagulant, the resulting palladium-containing precipitate being separated by known methods. For separation of the precipitate, it is advantageous to use filtration or flotation, preferably combining with filtration, respectively. flotation foam centrifugation. In the process according to the invention, the precipitation can be used as a coagulant, e.g. actively coal. The precipitation and coagulation process is preferably carried out continuously. The water-soluble salt of 2-mercaptobenzothiazole precipitates the insoluble Pd complex.

An advantage of said method of recovering palladium is that the addition of a coagulant substantially speeds up the coagulation process, which is slow at low Pd concentrations. The resulting suspension containing the solid phase Pd complex is subsequently processed, i. j. the solid phase is isolated from the solution. The addition of a coagulant is also advantageous with respect to other operations. It improves the filtration properties of the solid phase and simplifies further processing of the solid phase, i. j. combustion. After burning, a palladium concentrate is formed which can be further processed by known palladium dissolution procedures. The water-soluble salt of 2-mercaptobenzothiazole in a 10-20-fold molar excess over palladium is added to achieve maximum yield. The content of activated carbon in the basic solution of the water-soluble salt of 2-mercaptobenzothiazole is 1 to 10% by weight.

The following examples illustrate but do not limit the scope of the invention.

Example 1

A two-chamber flotator with a chamber volume of 12 liters was charged with 2.31 mg / L palladium waste water, t = 50 ° C and pH = ~ 4.8. To the waste water was added 1.8% by weight activated carbon suspension, 0.97% by weight 240 ml solution of ammonium salt of 2-mercaptobenzothiazole.

The mixture was stirred in the flotator for 30 minutes, then 4 ml of wetting agent was added and air was released. After 10 minutes of flotation, the flotator turned off. 20.5 L of wastewater with a palladium concentration of 0.20 mg / l remained in the flotator. Example 2

A two-chamber flotator with a chamber volume of 12 liters was pumped with organic matter contaminated at a concentration of 2.51 mg Pd / L, a temperature t = 50 ° C and a pH = 3.9, at a rate of 1.4 L / min. At the same time, a suspension of activated carbon in a solution of the ammonium salt of 2-mercaptobenzothiazole having the following composition was added:

2-MBT - 4.42% by weight, activated carbon 8.1% by weight, wetting agent 2.5% by weight, at a rate of 4 ml / min. The flotation foam was collected on the suction. The flotation effluent had an average Pd content of 0.38 mg / l, t. j. efficiency was 84.86%.

Claims (1)

SUBJECT Process for the isolation of palladium from waste water after catalytic hydrogenation, characterized in that the waste water chemically adjusted to pH <