Showing posts with label Adsorption. Show all posts

Sunday, October 18, 2020

ACTIVATED CARBON FILTERS - If you use an air purification system, or are shopping for one, you may be familiar with activated carbon filters. With so many air purifier filters to choose from, you may wonder how an activated carbon filter works or what the benefits of using one are. Don’t let their small stature fool you; these clever filters are major combaters of everything from allergens and harsh pollutants to unpleasant tastes and odors. They rely on the process of adsorption to remove and capture impurities, so that all you’re left with is fresh, breathable air. Activated carbon filters are small pieces of carbon, typically in granular or powdered block form, that have been treated to be extremely porous. It is so cavernous, in fact, that just one gram of activated carbon can easily have a surface area of 500m2 or higher. Vast surface area enables these carbon filters to adsorb exponentially more contaminants and allergens than traditional carbon. Adsorption is a process where organic compounds in the air or water react chemically with the activated carbon, which causes them to stick to the filter. The more porous the activated carbon is, the more contaminants it will capture. These filters are used to remove hazardous compounds in home air purification systems. There are many benefits associated with using activated carbon filters. These purifiers can be used to rid your air of unwanted or harmful contaminants that can pose a hazard to your health.

.................................................................................................................................................

Activated Carbon Filters

What They Are & How They Work

Sarah

If you use an air purification system, or are shopping for one, you may be familiar with activated carbon filters.

With so many air purifier filters to choose from, you may wonder how an activated carbon filter works or what the benefits of using one are.

Don’t let their small stature fool you; these clever filters are major combaters of everything from allergens and harsh pollutants to unpleasant tastes and odors.

They rely on the process of adsorption to remove and capture impurities, so that all you’re left with is fresh, breathable air.

Here is a closer look at how these small filters can make a big improvement in your overall air quality.

What is an Activated Carbon Filter?

Activated carbon filters are small pieces of carbon, typically in granular or powdered block form, that have been treated to be extremely porous.

It is so cavernous, in fact, that just one gram of activated carbon can easily have a surface area of 500m2 or higher.

Vast surface area enables these carbon filters to adsorb exponentially more contaminants and allergens than traditional carbon.

Adsorption is a distinct process where organic compounds in the air or water react chemically with the activated carbon, which causes them to stick to the filter.

The more porous the activated carbon is, the more contaminants it will capture.

These filters are most notably used to remove hazardous compounds in home air purification systems.

How Would I Benefit From an Activated Carbon Filter?

There are many benefits associated with using activated carbon filters.

These purifiers can be used to rid your air of unwanted or harmful contaminants that can pose a hazard to your health.

In air purification systems, activated carbon filters can be used in conjunction with HEPA filters to trap known allergens and impurities like:

o Dust

o Lint

o Mold spores

o Smoke

o Pet hair

o Common household chemicals

o Benzene and other VOCs

Carbon filters also help eliminate unpleasant odors so your indoor air remains fresh.

Used together, activated carbon and HEPA filters can trap 99.97% of small particles 0.3 microns and higher as well as most larger particles, especially spores.

Activated carbon filters can particularly benefit people who suffer allergies or aggravation from impure air, including second hand smoke.

If you are or live with a smoker, using an activated carbon filter in your home air purification system can provide unparalleled benefits to your respiratory health.

How do Activated Carbon Filters Work?

Although a filtration system that uses chemical reactions to decontaminate air may sound complicated, it is actually rather simple.

Activated carbon is typically sold in thick or thin packets for air filtration. It is then inserted into the main purifying device, such as an air purifier or HEPA air filter.

Contaminated air enters the filtration system, passes through the active carbon, undergoes adsorption, and leaves the filter purified.

If used in conjunction with a HEPA filter, the activated carbon works to prevent larger particles like dust and lint from reaching it, enabling the HEPA filter to perform better and last longer.

Are all Activated Carbon Filters the Same?

All activated carbon filters remove a significantly higher amount of air pollutants than regular carbon filters, however there are some distinctions.

Some filters contain more activated carbon than others, and this can affect the capacity for impurity removal.

The more activated carbon in a filter, the more contaminants it will catch and the faster it will adsorb.

Additionally, high levels of activated carbon increase a filter’s lifetime.

It will require fewer replacements and keep emitting fresh air longer. Another factor that influences filtering rate is the size of activated carbon particles.

Typically, smaller particles yield faster adsorption rates.

The most advanced activated carbon filters, like those found in Blueair air purifiers, are infused with other compounds like magnesium dioxide and copper oxide to remove even more hazardous pollutants from the air, such as carbon monoxide, ethylene oxide, and ozone.

Some modern activated carbon filters are also more adept at preventing a buildup of bacteria that can occur naturally over time.

Activated carbon filters are an important addition to any air purification system.

They can be used alone or in conjunction with other filters to significantly reduce the amount of impurities in your home or office.

Whether you choose a basic or advanced model, you can breathe easy using an activated carbon filter.

Sarah is a savvy urbanite with small town roots. As a foodie, wine lover & adventurer, she loves the bustling city and the great outdoors equally. Her motto is that you don’t have to sacrifice comfort, convenience, or fresh air for small-scale urban living.

https://learn.allergyandair.com/activated-carbon-filters/

Sunday, November 24, 2019

ACTIVATED CARBON - Activated Charcoal and How It Works - Activated charcoal is carbon that has been treated with oxygen. The treatment results in highly porous charcoal. These tiny holes give the charcoal a surface area of 300-2,000 m2/g, allowing liquids or gases to pass through the charcoal and interact with the exposed carbon. The carbon adsorbs a wide range of impurities and contaminants, including chlorine, odors, and pigments. Other substances, like sodium, fluoride, and nitrates, are not as attracted to the carbon and are not filtered out. Since adsorption works by chemically binding the impurities to the carbon, the active sites in the charcoal eventually become filled. Activated charcoal filters become less effective with use and have to be recharged or replaced.

.............................................................................................................................................................

Activated Carbon

Activated Charcoal and How It Works

by Anne Marie Helmenstine, Ph.D.

Activated charcoal (also known as activated carbon) consists of small, black beads or a solid black porous sponge.

It is used in water filters, medicines that selectively remove toxins, and chemical purification processes.

Activated charcoal is carbon that has been treated with oxygen. The treatment results in highly porous charcoal.

These tiny holes give the charcoal a surface area of 300-2,000 m²/g, allowing liquids or gases to pass through the charcoal and interact with the exposed carbon.

The carbon adsorbs a wide range of impurities and contaminants, including chlorine, odors, and pigments.

Other substances, like sodium, fluoride, and nitrates, are not as attracted to the carbon and are not filtered out.

Since adsorption works by chemically binding the impurities to the carbon, the active sites in the charcoal eventually become filled.

Activated charcoal filters become less effective with use and have to be recharged or replaced.

What Activated Charcoal Will and Won't Filter

The most common everyday use of activated charcoal is to filter water.

It improves water clarity, diminishes unpleasant odors, and removes chlorine.

It's not effective for removing certain toxic organic compounds, significant levels of metals, fluoride, or pathogens.

Despite persistent urban legend, activated charcoal only weakly adsorbs alcohol and it not an effective means of removal.

It will filter:

· Chlorine

· Chloramine

· Tannins

· Phenol

· Some drugs

· Hydrogen sulfide and some other volatile compounds that cause odors

· Small amounts of metals, such as iron, mercury, and chelated copper

It won't remove:

· Ammonia

· Nitrates

· Nitrites

· Fluoride

· Sodium and most other cations

· Significant amounts of heavy metals, iron, or copper

· Significant amounts of hydrocarbons or petroleum distillates

· Bacteria, protozoa, viruses, and other microorganisms

Activated Charcoal Effectiveness

Several factors influence the effectiveness of activated charcoal. The pore size and distribution vary depending on the source of the carbon and the manufacturing process.

Large organic molecules are absorbed better than smaller ones. Adsorption tends to increase as pH and temperature decrease.

Contaminants are also removed more effectively if they are in contact with the activated charcoal for a longer time, so flow rate through the charcoal affects filtration.

Activated Charcoal De-Adsorption

Some people worry that activated charcoal will de-adsorb when the pores become full.

While the contaminants on a full filter aren't released back into the gas or water, used activated charcoal is not effective for further filtration.

It is true that some compounds associated with certain types of activated charcoal may leach into the water. For example, some charcoal used in an aquarium might start to release phosphates into the water over time. Phosphate-free products are available.

Recharging Activated Charcoal

Whether or not you can or should recharge activated charcoal depends on its purpose.

It's possible to extend the life of an activated charcoal sponge by cutting or sanding off the outer surface to expose the interior, which might not have fully lost its ability to filter media.

Also, you can heat activated charcoal beads to 200 C for 30 minutes. This will degrade the organic matter in the charcoal, which can then be rinsed away, but it won't remove heavy metals.

For this reason, it's generally best to just replace the charcoal.

You can't always heat a soft material that has been coated with activated charcoal because it might melt or release toxic chemicals of its own, basically contaminating the liquid or gas you want to purify.

The bottom line here is that you possibly could extend the life of activated charcoal for an aquarium, but it's inadvisable to try to recharge a filter used for drinking water.

Anne Marie Helmenstine, Ph.D.

Introduction

Ph.D. in biomedical sciences from the University of Tennessee at Knoxville - Oak Ridge National Laboratory.

Science educator with experience teaching chemistry, biology, astronomy, and physics at the high school, college, and graduate levels.

ThoughtCo and About Education chemistry expert since 2001.

Widely-published graphic artist, responsible for printable periodic tables and other illustrations used in science.

Experience

Anne Helmenstine, Ph.D. has covered chemistry for ThoughtCo and About Education since 2001, and other sciences since 2013. She taught chemistry, biology, astronomy, and physics at the high school, college, and graduate levels. She has worked as a research scientist and also abstracting and indexing diverse scientific literature for the Department of Energy.

In addition to her work as a science writer, Dr. Helmenstine currently serves as a scientific consultant, specializing in problems requiring an interdisciplinary approach. Previously, she worked as a research scientist and college professor.

Education

Dr. Helmenstine holds a Ph.D. in biomedical sciences from the University of Tennessee at Knoxville and a B.A. in physics and mathematics with a minor in chemistry from Hastings College. In her doctoral work, Dr. Helmenstine developed ultra-sensitive chemical detection and medical diagnostic tests.

ThoughtCo and Dotdash

ThoughtCo is a premier reference site focusing on expert-created education content. We are one of the top-10 information sites in the world as rated by comScore, a leading Internet measurement company. Every month, more than 13 million readers seek answers to their questions on ThoughtCo.

For more than 20 years, Dotdash brands have been helping people find answers, solve problems, and get inspired. We are one of the top-20 largest content publishers on the Internet according to comScore, and reach more than 30% of the U.S. population monthly. Our brands collectively have won more than 20 industry awards in the last year alone, and recently Dotdash was named Publisher of the Year by Digiday, a leading industry publication.

https://www.thoughtco.com/how-does-activated-charcoal-work-604294

Sunday, July 8, 2018

ADSORPTION - Adsorption is defined as the adhesion of a chemical species onto the surface of particles. Adsorption is a surface phenomenon in which particles or molecules bind to the top layer of a material. Absorption, on the other hand, goes deeper, involving the entire volume of the absorbent. Absorption is the filling of pores or holes in a substance.

Activated carbon is a common material used for adsorption.
.

Adsorption

Adsorption Definition (Chemistry)

by Anne Marie Helmenstine, Ph.D.

Adsorption is defined as the adhesion of a chemical species onto the surface of particles.

German physicist Heinrich Kayser coined the term "adsorption" in 1881.

Adsorption is a different process from absorption, in which a substance diffuses into a liquid or solid to form a solution.

In adsorption, the gas or liquid particles bind to the solid or liquid surface that is termed the adsorbent. The particles form an atomic or molecular adsorbate film.

Isotherms are used to describe adsorption because temperature has a significant effect on the process.

The quantity of adsorbate bound to the adsorbent is expressed as a function of pressure of concentration at a constant temperature.

Several isotherm models have been developed to describe adsorption, including the linear, Freundlich, Langmuir, BET (after Brunauer, Emmett, and Teller), and Kisliuk theories.

IUPAC Definition of Adsorption

The IUPAC definition of adsorption is the "Increase in the concentration of a substance at the interface of a condensed and a liquid or gaseous layer owing to the operation of surface forces."

Examples of Adsorption

Examples of adsorbents include:

silica gel
alumina
activated carbon or charcoal
zeolites
adsorption chillers used with refrigerants
biomaterials that adsorb proteins

Adsorption is the first stage of a virus life cycle.

Some scientists consider the video game Tetris a model for the process of adsorption of shaped molecules onto flat surfaces.

Adsorption vs. Absorption

Adsorption is a surface phenomenon in which particles or molecules bind to the top layer of a material.

Absorption, on the other hand, goes deeper, involving the entire volume of the absorbent. Absorption is the filling of pores or holes in a substance.

Terms Related To Adsorption

Sorption: This encompasses both adsorption and absorption processes.

Desorption: The reverse process of sorption. The reverse of adsorption or absorption.

Characteristics of Adsorbents

Typically, adsorbents have small pore diameters so that there is a high surface area to facilitate adsorption. The pore size usually ranges between 0.25 and 5 mm.

Industrial adsorbents have high thermal stability and resistance to abrasion. Depending on the application, the surface may be hydrophobic or hydrophilic.

Both polar and nonpolar adsorbents exist.

The adsorbents come in many shapes, including rods, pellets, and molded shapes.

There are three major classes of industrial adsorbents:

carbon-based compounds (e.g., graphite, activated charcoal)
oxygen-based compounds (e.g., zeolites, silica)
polymer-base compound

How Adsorption Works

Adsorption depends on surface energy. Surface atoms of the adsorbent are partially exposed so they can attract the adsorbate molecules.

Adsorption may result from electrostatic attraction, chemisorption, or physisorption.

Uses of Adsorption

There are many applications of the adsorption process, including:

Adsorption is used to cool water for air conditioning units.
Activated charcoal is used for aquarium filtration and home water filtration.
Silica gel is used to prevent moisture from damaging electronics and clothing.
Adsorbents are used to increase the capacity of carbide-derived carbons.
Adsorbents are used to produce non-stick coatings on surfaces.
Adsorption may be used to extend the exposure time of specific drugs.
Zeolites are used to remove carbon dioxide from natural gas, remove carbon monoxide from reforming gas, for catalytic cracking, and other processes.
The process is used in chemistry labs for ion-exchange and chromatography.