Amorphous silica adsorbents for moisture control near ambient conditions, supplied in bulk in white and color-indicating grades and backed by technical support.
Silica gel is an amorphous, highly porous form of silicon dioxide, produced by acidifying a sodium silicate solution and then washing and drying the resulting gel into hard, glassy beads or granules. Despite the name, the finished product is a solid. Its internal pore network gives each bead a very large surface area, and the hydroxyl groups lining that surface have a strong affinity for water and other polar molecules, so the material draws moisture out of air, gas, and liquid streams by physical adsorption and, as humidity rises, by capillary condensation in the finer pores. Interra Global supplies silica gel in bulk under the sSORB® product line, in non-indicating white beads and in blue and yellow color-indicating grades. Silica gel is typically the desiccant of choice where the moisture load arrives at moderate to high relative humidity and near ambient temperature. Under those conditions it typically holds more water per pound than activated alumina or molecular sieve, and it regenerates at lower temperatures than either. The base material is chemically inert and non-toxic. Its capacity falls as temperature rises and as the stream gets drier, which is why deep drying and hot service typically go to molecular sieve, and standard grades are kept away from liquid water, which can fracture the beads. TYPES BY PORE STRUCTURE Silica gel is classified by pore size. Type A, the narrow pore gel, has a nominal pore opening of 20 to 30 angstroms and is the standard desiccant grade, with the highest capacity at low to moderate humidity among the gel types and high crush strength; every sSORB grade on this page is Type A. Wider pore gels, designated Type B and Type C, hold less water at low humidity and more at high humidity, and serve as humidity buffers, liquid-phase adsorbents, and catalyst carriers rather than as drying desiccants. Wider pore grades are available on request. INDICATING AND NON-INDICATING GRADES White silica gel, sSORB AW, is the non-indicating workhorse: the Type A bead with no additive, in three bead-size ranges for packed beds, breathers, and packaging. Indicating grades are the same Type A bead impregnated with a moisture-sensitive indicator, so a color change shows when the material is approaching saturation. Blue indicating silica gel uses cobalt chloride and shifts from deep blue through purple to pink as it takes up water. Yellow (orange) indicating silica gel is cobalt-free and shifts to dark green or to clear, depending on the grade. Indicating gel is typically used as a visible fraction blended into white gel, or on its own in sight glasses, dehydrating breathers, and packaging where an operator needs a visual check without instruments; the whole bed rarely needs to be indicating. Cobalt chloride carries hazard classifications in a number of jurisdictions and is restricted in some markets, so the cobalt-free grades are typically specified where that matters; the safety data sheet for each grade is the reference. WHERE SILICA GEL FITS AMONG INTERRA GLOBAL'S DESICCANTS Interra Global supplies three regenerable desiccant families, and the choice typically follows the service conditions. Silica gel takes the largest moisture load at ambient temperature and moderate to high humidity, and it is the usual choice for static protection, packaging, and dryers operating near ambient conditions; the sSORB Type A grades can adsorb moisture at temperatures as high as 220°F, with preferred service near room temperature and at high relative humidity, per the product data sheets. Activated alumina tolerates liquid water and higher temperatures and typically serves heat-regenerated and heatless compressed air dryers. Molecular sieve holds its capacity at low humidity and elevated temperature and reaches far lower outlet moisture, so it takes deep drying and dew point critical service, sometimes downstream of a gel or alumina bed that removes the bulk water first. Standard silica gel should not see liquid water; where free water or heavy carryover is possible, a water-resistant silica alumina gel guard layer typically protects the main bed. TYPICAL APPLICATIONS
PACKAGING AND SUPPLY sSORB silica gel ships in 55 lb (25 kg) bags and made-to-order super sacks, in quantities from bag lots to full container loads. Bead size, packaging, and current lead time are confirmed at quote, and unlisted sizes or grades route are quoted on request. SELECTING A GRADE Selection typically starts with three questions: whether a visual saturation check is needed, what the humidity and temperature at the bed will be, and whether liquid water could reach the media. From there, bead size, packaging, and regeneration method narrow the choice, and each product page below carries the properties and documents for its grade. When the right grade is not obvious, Interra Global's technical staff review the service conditions and recommend a fit when called on. FREQUENTLY ASKED QUESTIONS What is silica gel? Silica gel is a hard, porous, amorphous form of silicon dioxide (SiO2 · nH2O) used as a desiccant and adsorbent. Its internal surface carries hydroxyl groups with a strong affinity for water, so it draws moisture from the surrounding air, gas, or liquid and holds it in its pores until the material is regenerated by heating. It is among the most widely used desiccants for protecting goods and equipment from humidity. What is a desiccant? A desiccant is any material used to remove moisture from its surroundings. Most industrial desiccants are regenerable adsorbents that hold water on their internal surfaces and can be heated and reused; silica gel, activated alumina, and molecular sieve are the three in common bulk use. The word describes the job; adsorbent describes the mechanism. Is silica gel polar? Yes. The silicon-oxygen bonds in silica are polar, and the surface of a silica gel bead is lined with hydroxyl (silanol) groups, so the material attracts other polar molecules, water above all. That polarity is what makes silica gel a desiccant, and it is also why silica gel serves as the stationary phase in chromatography and can be surface-treated to adjust its selectivity for particular applications. How does indicating silica gel work, and which color should I use? Indicating grades carry a small amount of a moisture-sensitive indicator that changes color as the bead approaches saturation: blue to pink for the cobalt chloride grade, and yellow-orange to green or to clear for the cobalt-free grades. Choose by the check you need and the rules you operate under. Is silica gel toxic? Plain silica gel is chemically inert and non-toxic. The "do not eat" warning on desiccant packets exists because the packets and beads are a choking hazard, not because the silica is poisonous. Blue indicating silica gel is the exception: its cobalt chloride indicator carries hazard classifications, and the safety data sheet governs handling. Fine silica dust, like any dust, should not be inhaled. How is silica gel regenerated? Spent silica gel is regenerated by heating it in a stream of dry air or gas until the adsorbed water is driven off, typically at temperatures on the order of 250 to 350°F [SME, drafted figure: confirm or strike; the sentence reads whole without it], well below what molecular sieve requires. Indicating grades are typically regenerated at the lower end of the range to protect the indicator, and heavy overheating degrades the pore structure, so each grade's product data sheet is the reference. In regenerative dryers the cycle is built into the equipment; in static service the material is often replaced rather than regenerated. Can silica gel get wet? Standard silica gel should not be exposed to liquid water. Contact with free water can crack or shatter the beads, releasing fines and eventually plugging the bed, and saturated gel is at capacity in any case. Where free water, condensate, or carryover is possible, dryer designs typically protect the main bed with a water-resistant silica alumina gel layer that takes the liquid load without breaking down. [SME re-sight; OPP-003] When should I use silica gel instead of molecular sieve or activated alumina? As a rule of thumb: silica gel for the largest moisture loads at ambient temperature and moderate to high humidity, activated alumina where liquid water, higher temperature, or heatless regeneration is involved, and molecular sieve where the outlet has to be very dry. Many dryers pair the materials, with gel or alumina taking the bulk water ahead of a sieve polishing layer. The molecular sieve family page carries the fuller comparison. |
sSORB AW is a hard, smooth Type A silica gel bead with high moisture adsorption capacity and three particle-size options.
Thank you for contacting us!