CS255458B1 - Method of tablets preparation from activated carbon - Google Patents

Abstract

Tablets are for diffuse, permeation, optionally filter-adsorption capturing harmful substances from the air. The content is determined by analysis substances collected in the tablet and calculated the concentration of pollutants in the air. Yet known processes for compressing tablets from carbonaceous high pressure materials pressing a mixture of powdered sorbents with binder, can not be used. Deht the binders contain volatile organic especially substances that interfere with analysis by gas and liquid methods chromatography. Newly designed preparation the tablet is based on mixing the active coal and powdered polymer, such as polyethylene, and for heating the mixture in the press to a temperature above the temperature polymer melting.

Description

The invention solves the preparation of activated carbon tablets which are intended for diffuse, permeation or filter-adsorption capture of harmful substances from the atmosphere.

At present, CSR is used for filling of passive dosimeters and adsorption tubes exclusively with granular activated carbon, which is characterized by a widely developed structure of very fine pores with an effective diameter of less than 2 nm. The basic prerequisite for proper functioning of the bed of sorbent is a completely homogeneous filling of the determined geometric space with granules and furthermore that undesirable cavities and layers of different density are not formed. The pellet placement must resist shocks and vibrations, both vertically and horizontally.

□ Passive dosimeters are used to fix the bed of loose sorbent with various auxiliary materials such as filter paper, polyurethane foam, glass cloth or fine sieves of chemically resistant alloys. Practical experience has shown that all these materials are partially deformable and do not guarantee that the granulation bed does not cause undesirable movement of the granules, or the refolding of the granules, and thus the difficulty in defining the efficiency of the sorption bed.

These undesirable effects are particularly pronounced when sorption beds with a large area and a small thickness are used. The large-area beds are particularly appreciated in practice, because they allow the most efficient utilization of the sorbent capacity.

These difficulties are eliminated when the sorbent granules are bound in the sorption bed and the bed is compressed to form a tablet. Tablets of compressed activated carbon retain an unchangeable shape even over a large area and relatively small thickness. When used as a filler of passive dosimeters, they guarantee constant sorption efficiency and maximum sorbent utilization even when exposed to vibrations and vibrations. Another advantage of the charcoal tablets is that in their use, the laborious and time-consuming filling of passive dosimeters and filtration devices with loose sorbent and the necessity of careful homogenization of the granule bed in the sorption bed are eliminated.

The prior art processes for compressing carbonaceous material tablets based on high pressure compression of a mixture of powdered sorbents with tarry binders cannot be used, since tar binders contain considerable amounts of volatile organic compounds, making it impossible to analyze pollutants captured from the air by sorbent by liquid and gas chromatography methods. In addition, the high pressures required for tar-like substances to act as binders, causing partial destruction of the fine porous structure of activated carbon, and the prepared tablets have a significantly reduced sorption capacity.

The preparation of potable, sufficiently mechanically resistant, yet chemically pure activated carbon tablets has been achieved by the method of the invention. Inorganic ash-free activated charcoal, the grain size of which is modified by grinding, is mixed with the organic polymer in a specified ratio. A suitable type of organic polymer is suitable, the presence of which does not interfere in the evaluation of the samples taken by the chromatographic method used.

The sorbent / polymer mixture is filled with a hand press, the molded material being separated from the inner walls with a suitable heat-resistant, non-stick material.

The tightened press is placed in a furnace heated to a temperature above the melting point of the polymer used. After a period of time, which depends on the melting point of the organic polymer, the press is removed from the furnace and heat-tightened again. The tightened press is put back into the furnace at the same temperature. The press is then allowed to cool to ambient temperature, the molding is removed and tablets of the desired shape are prepared by cutting, chopping or slicing.

The manufactured tablets can advantageously be used by all workplaces focused on measuring the concentrations of harmful substances in the air, which is one of the important tasks in the complex solution of protection and creation of environment and work environment. Direct manufacturers of passive dosimeters and air sampling devices can also use the tablet preparation process.

Example

Technical activated charcoal for recuperation purposes is subjected to grinding and sieve analysis of 0.3 to 0.6 mm fractions. The prepared fraction is freed from dust by decanting with distilled water and extracted several times in an Soxhlet inorganic ash apparatus. Distilled water was first used as the extraction liquid, followed by azeotropic hydrochloric acid, with each liquid extracting the activated carbon continuously for at least 6 hours. The extracted sorbent is washed with dilute ammonia until the reaction to chloride ions disappears and is pre-dried in a tray oven at 70 ° C. The pre-dried charcoal is introduced into a tube and dried in a stream of inert gas such as nitrogen at a temperature of 300 to 350 ° C for at least two hours. The sorbent prepared is mixed well with powdered polyethylene (3 parts by weight of activated carbon, 2 parts by weight of polyethylene powder).

The mixture is filled to the inside of the hand press, the bottom of which is covered with a separating layer of glass fabric. The mixture is covered with a glass cloth and the press is tightened by hand.

The tightened press is placed for 30 minutes in an oven heated to 160 ° C. After this time, the press is removed, tightened while still warm and placed in the oven heated to 160 ° C for 30 minutes. After this time, the press is allowed to cool, the molding obtained is removed and, after removal of the glass cloth, tablets of the desired shape are prepared by cutting, chopping or slicing. The prepared tablets are particularly suitable for passive dosimeters intended for capture of organic solvent vapors from the atmosphere by gas chromatography methods.

Claims (1)

SUBJECT OF THE INVENTION Process for the preparation of activated carbon tablets intended for diffuse, permeation or filter-adsorption capture of harmful substances from gaseous mixtures or aerosols, for example from the air, characterized in that the sorbent mixed with a pulverulent polymer, for example polyethylene, is subjected to heating at a temperature above melting point of the polymer.