Difference between revisions of "Silica gel, commercial"

From CAMEO
Jump to navigation Jump to search
Line 1: Line 1:
**This record is in progress. Please do not link or cite
 
.
 
 
==Description==   
 
==Description==   
 +
An amorphous material of [[silica|silica]] that has the ability to act as a humidity buffering agent.  As a RH buffer, silica gel absorbs moisture in humid environments and releases water in dry air. Once equilibrated to set moisture level, silica gel will maintain that humidity level in a tightly sealed environment. Silica gel performs best at room temperature (70-80F) and high humidity (60-90%). The pore size in silica gel is related to its ability to adsorb water and other pollutants. Silica gel Type A with approximately pore size of 2.5 nm is most often used for vapor-phase moisture. Silica gel saturated with water can dried with heat (120 C for 2 hours) and used again as a desicant.  For re-use as a humidity buffer, it must be reconditioned at the required humidity.
  
 
{| class="wikitable"  
 
{| class="wikitable"  
Line 29: Line 28:
 
| cellulose, water, salts
 
| cellulose, water, salts
 
| 62% +/- 3% in sealed container
 
| 62% +/- 3% in sealed container
| same
+
| Same
| food storage, tobacco, wood  instruments, herbs; variable size packets
+
| Food storage, tobacco, wood  instruments, herbs; variable size packets
 
| Sorbent Systems: [https://www.sorbentsystems.com/moisturepak.html MoisturePak]
 
| Sorbent Systems: [https://www.sorbentsystems.com/moisturepak.html MoisturePak]
 
|-
 
|-
Line 37: Line 36:
 
| 30%  35%  40% 45%    50%  55%  60%
 
| 30%  35%  40% 45%    50%  55%  60%
 
| Optimum between 30-60% range
 
| Optimum between 30-60% range
| similar performance as Rhapid  gel; beads, sachets, cassettes
+
| Similar performance as Rhapid  gel; beads, sachets, cassettes
 
| Sercalia: [https://www.sercalia.com/en/prosorb-moisture-stabilizer/ Prosorb]
 
| Sercalia: [https://www.sercalia.com/en/prosorb-moisture-stabilizer/ Prosorb]
 
|-
 
|-
Line 44: Line 43:
 
| 0% 40% 45% 50% 60%
 
| 0% 40% 45% 50% 60%
 
| Best for 0-65% range; avg value  of MH* is 5 in range
 
| Best for 0-65% range; avg value  of MH* is 5 in range
| flexible moisture-pearmeable  sachets
+
| Flexible moisture-pearmeable  sachets
 
| APSNYC: [https://www.apsnyc.com/products Products page]
 
| APSNYC: [https://www.apsnyc.com/products Products page]
 
|-
 
|-
Line 55: Line 54:
 
|-
 
|-
 
| Silica  gel M
 
| Silica  gel M
| macroporous SiO2
+
| Macroporous SiO2
 
|  
 
|  
 
| Best for 80-100%
 
| Best for 80-100%
| prevents condensation at high RH
+
| Prevents condensation at high RH
 
|  
 
|  
 
|-
 
|-
Line 65: Line 64:
 
|  
 
|  
 
| Best for 0-30%
 
| Best for 0-30%
| moisture indicator: changes  orange to green as increases from 5 to 15%
+
| Moisture indicator: changes  orange to green as RH increases from 5 to 15%
 
| AGM:  [https://www.agmcontainer.com/blog/desiccant/indicating-silica-gel/#:~:text=These%20indicators%2C%20typically%20either%20cobalt%20chloride%20or%20methyl,silica%20gel%20needs%20to%20be%20replaced%20or%20recharged.  Blue vs orange]
 
| AGM:  [https://www.agmcontainer.com/blog/desiccant/indicating-silica-gel/#:~:text=These%20indicators%2C%20typically%20either%20cobalt%20chloride%20or%20methyl,silica%20gel%20needs%20to%20be%20replaced%20or%20recharged.  Blue vs orange]
 
|-
 
|-
Line 72: Line 71:
 
|  
 
|  
 
|  
 
|  
| moisture indicator: changes blue  to pink as increases from 15-45%
+
| Moisture indicator: changes blue  to pink as RH increases from 15-45%
 
|  
 
|  
 
|-
 
|-

Revision as of 10:27, 11 August 2023

Description

An amorphous material of Silica that has the ability to act as a humidity buffering agent. As a RH buffer, silica gel absorbs moisture in humid environments and releases water in dry air. Once equilibrated to set moisture level, silica gel will maintain that humidity level in a tightly sealed environment. Silica gel performs best at room temperature (70-80F) and high humidity (60-90%). The pore size in silica gel is related to its ability to adsorb water and other pollutants. Silica gel Type A with approximately pore size of 2.5 nm is most often used for vapor-phase moisture. Silica gel saturated with water can dried with heat (120 C for 2 hours) and used again as a desicant. For re-use as a humidity buffer, it must be reconditioned at the required humidity.

Product Composition Pre-conditioned RH options Humidity for usage Comments/Forms Web page for more info
Arten Gel type A SiO2 0% 30% 40% Best for 0-40% range; avg value of MH* is 5 in range 8 mesh beads (2mm diameter) in moisture permeable bag APSNYC: Product page
Art Sorb 90% SiO2 10% LiCl 0% 40% 45% 50% 55% 60% 65% 70% Best from 40-70% Prosorb site says Art Sorb is best from 60-80%; beads, sheets, cassettes Fuji Silysia: Art Sorb
Moisture Pak cellulose, water, salts 62% +/- 3% in sealed container Same Food storage, tobacco, wood instruments, herbs; variable size packets Sorbent Systems: MoisturePak
Prosorb 97% SiO2 3% Al2O3 30% 35% 40% 45% 50% 55% 60% Optimum between 30-60% range Similar performance as Rhapid gel; beads, sachets, cassettes Sercalia: Prosorb
Rhapid gel Hybrid SiO2 0% 40% 45% 50% 60% Best for 0-65% range; avg value of MH* is 5 in range Flexible moisture-pearmeable sachets APSNYC: Products page
Silica gel E type A SiO2 Best for 0-30%
Silica gel M Macroporous SiO2 Best for 80-100% Prevents condensation at high RH
Silica gel orange type A SiO2 with methyl violet indicator Best for 0-30% Moisture indicator: changes orange to green as RH increases from 5 to 15% AGM: Blue vs orange
Grade 42 type A SiO2 with cobalt dichloride indicator Moisture indicator: changes blue to pink as RH increases from 15-45%
Grade 40 type A SiO2 may be mixed with 42

Moisture Reservoir Information

Silica Gel Comparison
Preservation Equipment

The moisture adsorbing properties of silica gels are affected by factors such as capillary pore size or the inclusion of hygroscopic salts, resulting in a wide range of performance. Thus, it is important to compare the buffering capacity of different types of silica gels to determine which has the best performance for a specific application. In 1977, Thomson described the specific moisture reservoir with the variable M where M represents the amount of water (in grams) that is gained or lost by 1 kilogram of silica gel for each 1% change in RH. However for any specific silica gel type, M can vary widely due to the expected RH range and the hysteresis of the adsorption/desorption curve. In order to compensate, a new value called MH has been defined as the average amount of water (in grams) that is gained or lost by 1 kilogram of silica gel for each 1% change in RH. This is determined by repeatedly cycling silica gel between adsorption and desorption within a specific RH range until a constant value is measured.

TABLE: Specific moisture reservoir (g/kg for a 1% RH change) at 20°C *

Moisture sorbent MH 50 ± 10% M 20 → 30% M 60 → 50% Recommended amounts
RH around 50% Keep RH low Keep RH high Depends on air flow and exhibit length
RHapid Gel 6.11 ± 2.16 4.48 ± 0.42 4.38 ± 1.40 2-4 kg/m3
PROSorb 5.42 ± 1.32 4.37 ± 0.10 4.25 ± 0.38 2-4 kg/m3
Art-Sorb 4.04 ± 0.80 2.84 ± 0.47 4.18 ± 0.49 4-8 kg/m3
Arten Gel 5.7 5.5 9-18 kg/m3
Regular density silica gel (clear, type A) 1.93 ± 0.44 5.48 ± 0.40 1.47 ± 0.16 9-18 kg/m3
Orange silica gel 1.16 ± 0.26 4.92 ± 0.59 0.94 ± 0.14 9-18 kg/m3
Bentonite clay (Desi Pak) 1.19 ± 0.07 2.25 ± 0.03 1.11 ± 0.02
Molecular sieves 4A (zeolite) 0.33 ± 0.02 0.47 ± 0.04 0.31 ± 0.01

Table from: J. Tetreault (2017) with additional information from S. Weintraub (2002)

Resources and Citations

Retrieved from "https://cameo.mfa.org/index.php?title=Silica_gel,_commercial&oldid=96380"