Does paper have bleach
The Science of Papermaking and Paper Recycling: A Research Experience for Teachers
Contributed by SSEP Performing Inquiry based Exploration project.
Dr. Richard Venditti, Associate Professor, Department of Wood and Paper Science
North Carolina University, Raleigh NC 27695-8005
Email: [email protected]
Bleaching of Recycled Pulp:
Objective: Be able to perform bleaching of recycled fiber.
Background: Some contaminants defy removal by any physical type of separation process. For instance, contaminants that are absorbed or exist in the fiber wall may be very difficult to remove. Dyes in particular are one such contaminant. Another contaminant inherent in the fiber is lignin. To remove or destroy dyes or lignin one must resort to chemical attack. A bleaching agent is used to destroy the “chromophores” responsible for making fibers dark. Sodium hypochlorite is one such chemical. Another very common bleaching agent used is peroxide. In this laboratory, you will learn a simple method to bleach recycled pulp.
- Obtain an 8.5 by 11 inch piece of colored copy paper.
- Cut the paper in half. Set aside one-half of the sheet of paper as a control. Rip up the other half of the paper into approximately 2 inch squares and add to 1000 ml of hot water in a blender cup.
- Blend for 30 seconds .
- Filter the pulp through a Buchner Funnel. You may use either a piece of filter paper or some cheese cloth as the filtering material. Peel the filter paper (or cheese cloth) off of the pulp mat. Put the pulp mat into an approximately 250 ml glass bottle or jar.
- SAFETY: Always use caution when using bleach. It is a chemical that should be treated with respect. Avoid contact with skin. Avoid splashes. Use safety glasses when handling the bleach. The bleach will destroy clothing. Add enough common household sodium hypochlorite bleach to cover the pulp mat, approximately 50-100 ml. Use a stirring rod to mix the bleach and the pulp.
- Stir for about 10 seconds approximately every 3 minutes. Observe if there is any color change over a time period of about 10 minutes.
- After the bleaching, dilute the contents with 500 ml of water.
- Make a filter pad using the filtering apparatus, this time leaving the filter paper on the pad.
- SAFETY: Always use caution with a laundery iron. Do not leave a hot iron where it could be incidentally contacted or dropped off a table. Make sure the electric cord is not in a position to be snagged accidently. Make sure to turn off the iron when finished using. Put the filter paper and pad between two sheets of premium kitchen paper towel tissue. Dry the filter pad with a laundry iron until dry. Peel off the filter paper after dry.
- Qualitatively compare the original colored copy paper with the bleached sample. Make observations.
What might be the disadvantages of using too much bleach?
Do you think changing the consistency of the pulp would change the bleaching process?
How might time or temperature change the efficiency of the bleaching process?
What may have been needed in the bleaching process if some parts of the pulp are bleached and others are not?
Try the bleaching process on the following types of paper:
- Newsprint, unprinted edges.
- A corrugated box.
- The fluted inner medium of a corrugated box alone.
- The outer liner of a corrugated box alone .
- Different colors of copy paper.
- A high quality coated brochure.
*How does each of the above respond to the bleaching process?
*Try the bleaching process on moderately heavily printed toner paper. Make sure to pulp for 30 seconds or less. Does the bleaching process have any effect on the toners? Why or why not?
*For one of the types of wastepaper that does bleach (e.g. a colored copy paper or a corrugated box) try to determine how much bleaching agent is needed to effectively bleach the wastepaper pulp. This can be done by substituting tap water for a portion of the bleaching agent. For instance try the following volumetric ratios of bleach to water: 100/0, 75/0, 50/50, 25/75, 10/90, 5/95, 1/99.
*Peroxide is a common bleaching agent. Try to bleach any of the types of wastepaper that does bleach with hypochlorite with peroxide available from a grocery or drug store. What is your result? Why did or it did not work?Does paper have bleach The Science of Papermaking and Paper Recycling: A Research Experience for Teachers Contributed by SSEP Performing Inquiry based Exploration project. Dr. Richard
Does paper have bleach
The bleaching process used to whiten products, particularly paper, paper products, and tissue products, is another critical environmental factor to include in environmentally sustainable criteria. Chlorine used in manufacturing processes affects not only the environment but also human health as well.
Up until the late 1990s, chlorine was the chemical of choice for bleaching paper in the kraft pulping process, which produces almost all printing and office papers, as well as tissue products, along with some types of packaging. Not only does chlorine get paper fibers very white, it also pulls out and binds with lignins (the structural cells in the tree that cause paper to deteriorate).
However, when chlorine bonds chemically with carbon-based compounds (such as lignins), it produces dioxins and toxic pollutants. When released into water, they do not break down. Dioxin, even when released in miniscule amounts, bioaccumulates as it moves up the food chain, reaching its highest concentration in humans, where it is increasingly linked to cancers as well as endocrine, reproductive, nervous and immune system damage.
As early as 1985, the U.S. Environmental Protection Agency (EPA) labeled dioxin “the most potent carcinogen ever tested in laboratory animals.” EPA has been working for several years on an assessment of dioxin and its sources. Its report is currently available in draft form. But it has found that, while there are some natural causes of dioxins, such as forest fires and volcanoes, their production is very small compared to human-made sources. Paper mills figure significantly as one of these human-made sources.
In 1998, EPA released the “Cluster Rules,” which regulate the amount of hazardous pollutants paper mills are allowed to release, whether to water, air or land. The mills can develop their own methods for compliance. Many environmental and health advocates believe that the Cluster Rules do not go far enough, and disagreement continues over what method of dealing with dioxins and other chlorinated pollutants is best.
However, what is clear is that there are methods of bleaching paper pulp that totally eliminate the possibility of dioxins, replacing chlorine with oxygen, ozone and hydrogen peroxide instead. These methods are primarily used only in many of the deinking mills producing recycled pulp in North America and in European virgin and recycled pulp mills. North American virgin pulp mills have, instead, converted to “elemental chlorine free” (ECF) processes that use chlorine derivatives, primarily chlorine dioxide, instead of elemental chlorine gas. ECF does dramatically reduce the potential to form dioxins, but does not completely eliminate it. However, some paper manufacturers and sales representatives present their papers as “chlorine free” when they mean only that it was not bleached with chlorine gas, not that no form of chlorine was used.
The Worldwatch Institute (Paper Cuts, 1999) reports that a mill using standard chlorine bleaching will release about 35 tons of organochlorines (dioxins and chlorinated toxic pollutants) a day. An ECF mill will release 7-10 tons per day. A PCF/TCF mill will release none.
There are four bleaching terms that are important to understand. Two describe processes to avoid, and two describe processes to encourage.
Use Only If Better Alternatives Are Not Available
Uses a chlorine compound, most often chlorine dioxide, that significantly reduces dioxins but does not eliminate them. Paper companies using ECF often say that dioxin is “nondetectable” in their wastewater. This refers only to the sensitivity of prescribed tests, and does not necessarily mean there are no dioxins. State-of-the-art tests are often able to detect dioxins when prescribed tests find them nondetectable.
Some ECF mills go beyond simply bleaching with chlorine dioxide. If they have added “extended delignification” and do part of their processing with ozone or oxygen or other non-chlorine brighteners, they can further reduce their potential for producing dioxins.
FREQUENTLY ASKED QUESTIONS
Q: If a mill buys pulp to make their chlorine free paper, is it the bleaching system of the manufacturer or of the pulp supplier that has to be completely chlorine free?
A: “Chlorine free” is a description of the process used to make the paper. Therefore, the pulp supplier definitely must use completely chlorine free bleaching processes. If the manufacturer bleaches the pulp in its papermaking process, then it, too, must be chlorine free.
However, some mills buy chlorine free pulp and make paper without additional bleaching in their own facility. If the pulp is not contaminated with pulp in the mill that was bleached with chlorine or chlorine compounds, then it still can produce chlorine free paper.
In addition, a few recycled printing and office papers are made without any bleaching at all. The scrap paper is simply dumped into a pulping vat without either deinking or bleaching. This paper almost always is speckled from the ink particles that were not removed (considered a desirable graphic effect for many letterheads and brochures), and would also be considered to be unbleached, or processed chlorine free. (However, not all speckled papers are made in this way; many are bleached with chlorine or chlorine dioxide. Check with the mill.)
Q: Isn’t PCF paper contaminated by chlorine from the fibers’ original virgin paper production?
A: Because virtually all virgin printing and writing papers in North America are bleached with some form of chlorine compounds or derivatives, one can assume that the recycled fibers come from papers originally chlorine bleached. Some health advocates have been concerned that trace amounts of chlorine might remain in the fibers.
However, recycling is a very wash-intensive process. Before the fibers are made into new paper, they are washed, swirled, rubbed, screened, and rinsed many times. It is unlikely that chlorine will still be attached to the fibers.
Rather, what matters most is how the paper is made in its recycled version. If it is processed without any chlorine or chlorine derivatives, it qualifies as chlorine free paper.
Q: Still, isn’t it better to buy paper that is TCF so that there’s no chance any chlorine could have been introduced into the product?
A: It is important that manufacturers, including those making virgin paper, use chlorine free processes. Not only is this safer for the environment and human health, but most recycled papers have some virgin fiber and need reliably chlorine free sources for it. Still, it’s important to remember that the point of asking for truly chorine free paper is to develop enough market demand for it that mills will have incentives to switch to it.
At the same time, chlorine free, while very important, is not the only environmental characteristic to consider in choosing paper. Combining factors is far better. (See Which Is Better: TCF, Tree Free or Recycled?) Even when all our paper is produced in chlorine free processes, we will still need to recycle it. It is critical to keep the recycling system going now by choosing recycled content along with chlorine free bleaching. Some tree free pulps are also chlorine free.
Q: My paper salesperson assured me the paper I bought was chlorine free. Later, I learned that it was ECF. Did they lie to me?
A: Some people within the paper industry are playing with semantics. They tell customers that a paper is “chlorine free” when they actually mean it is “chlorine gas free” or free of “elemental chlorine.” They know most customers will assume that therefore there is no chlorine involved in the process. However, most North American mills are now using chlorine dioxide, a derivative of chlorine. While it dramatically reduces the potential for dioxins by more than 90%, it cannot completely eliminate them, despite industry literature to the contrary.
Because the terms are not yet being used consistently and reliably, you need to investigate the paper’s manufacturing process to be sure it’s TCF or PCF.
Q: How can I do that if I’m not a paper manufacturing expert? Besides, I don’t have time to investigate every paper I use.
A: Fortunately, you have help. The Chlorine Free Products Association certifies papers that meet their criteria for chlorine free, which includes several factors in addition to the bleaching method. It awards its PCF symbol to papers that contain a minimum of 30% postconsumer fiber, have not been rebleached with chlorine-containing compounds, are made in mills without outstanding environmental violations, and use TCF virgin pulp (when virgin fiber is included in the paper) that did not come from old growth forests. Its TCF symbol is awarded to virgin papers meeting the same criteria, without, of course, the recycled content requirement. CFPA’s process includes visits to the mills and extensive documentation.
Of course, not all chlorine free papers have gone through CFPA’s certification process, yet they are still manufactured in a chlorine free process. Conservatree identifies chlorine free papers on our paper listings that either have gotten CFPA or other chlorine free certifications, or that we have interviewed mill representatives enough about to be convinced that they, also, qualify as chlorine free. While an intensive investigation process, such as is conducted through certification, is the best assurance that the papers meet your expectations, there are many non-certified papers that are reliably chlorine free (TCF and PCF) as well.Does paper have bleach The bleaching process used to whiten products, particularly paper, paper products, and tissue products, is another critical environmental factor to include in ]]>