Multilayer composite for reversible sorption of mercury and method for sorption and desorption of mercury from a gaseous phase

Abstract

A multilayer composite for reversible sorption of mercury, with a carrier core made of a metal or an alloy based on transition metals, has isolating layers of a transition metal nitride and externally located sorptive layers, made of a mixture of sulfides and nitrides of transition metals, the layers being deposited on both sides of the core. A method for sorption of mercury from a gaseous phase during an exposition of the multilayer composite to the influence of multicomponent gaseous mixtures that contain mercury vapors or compounds for a time period of 0.5 to 24 hours, while the temperature of the multilayer composite is maintained in the range from 20 to 150 C.

Claims

1. A multilayer composite for reversible sorption of mercury, wherein the following layers are deposited on both sides of a carrier core made of a metal or an alloy based on transition metals: an isolating layer of a transition metal nitride and an externally located sorptive layer, made of a mixture of sulfides and nitrides of transition metals.

2. A multilayer composite, according to claim 1, wherein the carrier core is made of iron.

3. A composite, according to claim 1, wherein the carrier core has a thickness of 0.2 to 2.5 mm.

4. A multilayer composite, according to claim 1, wherein the isolating layer is made of iron nitride.

5. A multilayer composite, according to claim 1, wherein the isolating layer has a thickness of 0.001 to 0.04 mm.

6. A multilayer composite, according to claim 1, wherein the sorptive layer is made of iron sulfide Fe.sub.1-xS and iron nitride Fe.sub.2-3N.

7. A multilayer composite, according to claim 1, wherein the thickness of the sorptive layer is from 0.001 to 0.04 mm.

8. A multilayer composite, according to claim 1, wherein the volume ratio of transition metal sulfides to nitrides in the sorptive layer is from 0.2 to 4.

9. A method for sorption of mercury from a gaseous phase, comprising exposing the multilayer composite, according to claim 1 to a multicomponent gaseous mixture containing mercury vapours or compounds, for a time period of 0.5 to 24 hours, the temperature of the multilayer composite being maintained in the range from 20 to 150 C.

10. A method for desorption of mercury from a gaseous phase, comprising heating the multilayer composite obtained by the method according to claim 9 in a stream of a flowing gas or gaseous mixture at a temperature of 180 to 600 C. for a time period of 3 minutes to 6 hours.

11. A method of reversible sorption and desorption of mercury from a gaseous phase, comprising carrying out sorption by the method of claim 8, thereby obtaining a multilayer composite sorbed with mercury, followed by heating the multilayer composite sorbed with mercury in a stream of a flowing gas or gaseous mixture at a temperature of 180 to 600 C. for a time period of 3 minutes to 6 hours, thereby obtaining a multilayer composite desorbed of mercury, wherein the number of sorption-desorption cycles is contained in the range of 1 to 50.

Description

EXAMPLE 1

(1) The sorptive composite with the sorptive layer having a thickness of 0.015 mm, consisting of iron sulfide Fe.sub.1-xS and iron nitride Fe.sub.2-3N, with the isolating layer having a thickness of 0.02 mm, made of iron nitride, on a carrier core having a thickness of 1 mm, made of a low-carbon steel, was exposed to a gaseous atmosphere containing vapours of mercury for 2 hours at a temperature of 50 C. As a result, an increase in the mercury content in the sorptive composite was obtained, from 0.0005% by wt. to 0.1% by wt.

EXAMPLE 2

(2) The sorptive composite with the sorptive layer having a thickness of 0.025 mm, consisting of iron sulfide Fe.sub.1-xS and iron nitride Fe.sub.23N, with the isolating layer having a thickness of 0.025 mm, made of iron nitride, on a carrier core having a thickness of 1.5 mm, made of a low-carbon steel, was exposed to a gaseous atmosphere containing vapours of mercury for 2 hours at a temperature of 80 C. As a result, an increase in the mercury content in the sorptive composite was obtained, from 0.0005% by wt. to 0.18% by wt.

EXAMPLE 3

(3) The sorptive composite with the sorptive layer having a thickness of 0.03 mm, consisting of iron sulfide Fe.sub.1-xS and iron nitride Fe.sub.23N, with the isolating layer having a thickness of 0.035 mm, made of iron nitride, on a carrier core having a thickness of 1.5 mm, made of a low-carbon steel, was exposed to a gaseous atmosphere containing vapours of mercury for 24 hours at a temperature of 100 C. As a result, an increase in the mercury content in the sorptive composite was obtained, from 0.0005% by wt. to 0.19% by wt.

EXAMPLE 4

(4) The sorptive composite with adsorbed mercury, described in Example 2, was subjected to heating in a stream of flowing nitrogen at a temperature of 200 C. for at least 30 minutes. As a result, a decrease in the mercury content to 0.0005% by wt. was obtained.

EXAMPLE 5

(5) The sorptive composite with adsorbed mercury, described in Example 3, was subjected to heating in a stream of flowing nitrogen at a temperature of 250 C. for at least 45 minutes. As a result, a decrease in the mercury content to 0.0005% by wt. was obtained.

EXAMPLE 6

(6) The sorptive composite was subjected to fivefold double cycles of: sorption under the conditions described in Example 2 and desorption under the conditions described in Example 4. As a result, repeatable ranges of mercury content from 0.17-0.19% by wt. were obtained after sorption cycles and, each time, a decrease in the content to 0.0005% by wt. after desorption processes.