Subject: Science and Technology

Plastic from used personal protective equipment (PPE) can be transformed into renewable liquid fuels using chemical a process called pyrolysis, says a new study.

Try this PYQ:

Q.In the context of which one of the following are the terms ‘pyrolysis and plasma gasification’ mentioned? (CSP 2019)

(a) Extraction of rare earth elements

(b) Natural gas extraction technologies

(c) Hydrogen fuel-based automobiles

(d) Waste-to-energy technologies

What is Pyrolysis?

• Pyrolysis is the thermal decomposition of materials at elevated temperatures in an inert atmosphere.
• It involves a change in chemical composition. The word is coined from the Greek-derived elements pyro “fire” and lysis “separating”.
• It is most commonly used in the treatment of organic materials. It is one of the processes involved in charring wood.
• It is considered as the first step in the processes of gasification or combustion.

How does it work?

• In general, pyrolysis of organic substances produces volatile products and leaves a solid residue enriched in carbon, char.
• Extreme pyrolysis, which leaves mostly carbon as the residue, is called carbonization.
• The process is used heavily in the chemical industry, for example, to produce ethylene, many forms of carbon, and other chemicals from petroleum, coal, and even wood, to produce coke from coal.

Applications

• Aspirational applications of pyrolysis would convert biomass into syngas and biochar, waste plastics back into usable oil, or waste into safely disposable substances.

Limitations and Concerns

• The technology requires drying of soil prior to treatment.
• Limited performance data are available for systems treating hazardous wastes containing polychlorinated biphenyls (PCBs), dioxins, and other organics.
• There is concern that systems that destroy chlorinated organic molecules by heat have the potential to create products of incomplete combustion, including dioxins and furans.
• These compounds are extremely toxic in the parts per trillion range.
• The molten salt is usually recycled in the reactor chamber. However, depending on the waste treated (especially inorganics) and the amount of ash, spent molten salt may be hazardous and require special care in disposal.
• Pyrolysis is not effective in either destroying or physically separating inorganics from the contaminated medium.
• Volatile metals may be removed as a result of the higher temperatures associated with the process, but they are not destroyed.
• When the off-gases are cooled, liquids condense, producing an oil/tar residue and contaminated water.
• These oils and tars may be hazardous wastes, requiring proper treatment, storage, and disposal.

Ahead of the laying of the foundation stone for a temple, claims and denials have emerged about plans to put in a time capsule, or ‘Kaal Patra’.

Do you know?

A rubidium standard or rubidium atomic clock is the most inexpensive, compact, and widely produced atomic clock, used to control the frequency of television stations, cell phone base stations, in test equipment, and global navigation satellite systems like GPS.

What is a Time Capsule?

• It is a container of any size or shape, which accommodates documents, photos and artefacts typical of the current era and is buried underground, for future generations to unearth.
• The time capsule requires special engineering so that the contents don’t decay, even if pulled out after a century.
• Material such as aluminium and stainless steel are used for the encasing, and documents are often reproduced on acid-free paper.
• While the term “time capsule” was coined in the 20th century, among the earliest examples of one dates back to 1777, found by historians inside the statue of Jesus Christ in Spain during its restoration.

There’s a global society:

International Time Capsule Society

• The International Time Capsule Society (ITCS), based in the US and formed in 1990, is now defunct but continues estimating the number of time capsules in the world.
• As per its database, there are “10,000-15,000 times capsules worldwide”.

Are there any time capsules in India?

• There have been a number of prominent examples.
• One time capsule, outside the Red Fort and placed underground in 1972 by then PM Indira Gandhi, was dug out by the subsequent government.
• Other time capsules are at a school in Mumbai, IIT-Kanpur, LPU in Jalandhar, and Mahatma Mandir in Gandhinagar.
• The Red Fort time capsule was supposed to be dug out after 1,000 years.

Significance of time capsules

• Historians often criticize the idea of being motivated.
• This exercise is inevitably a subjective exercise, geared towards glorification not to construct the real picture.
• All historians look at this time capsule exercise with suspicion.
• It’s not a valid historical method — who decides what matter, what artefacts, written documents are going into it?

Ahead of the 75th anniversary of Hiroshima, a Japanese court has recognised 84 survivors of the post-nuclear explosion “black rain” as the atomic bomb survivors. This would enable them to avail free medical benefits.

Try this question from CSP 2011:

Q.Acid rain is caused by the pollution of the environment by:

(a) Carbon dioxide and nitrogen

(b) Carbon monoxide and carbon dioxide

(c) Ozone and carbon dioxide

(d) Nitrous oxide and Sulphur dioxide

What is Black Rain?

• An estimated 69 per cent of the buildings in Hiroshima were destroyed by the atomic bomb.
• The debris and soot from this, mixed with the radioactive fallout from the bomb, raised high into the atmosphere in the form of a mushroom cloud.
• This material combined with the vapour in the atmosphere and came down as dark drops of liquid that have been called black rain.
• Survivors of the black rain described it as consisting of large, greasy drops that are much heavier than normal raindrops.
• It is full of highly radioactive material, and studies have shown that exposure to it can result in serious illnesses.

What was its effect?

• A study conducted in the year 1945 itself showed that black rain had come down as far as 29 km away from ground zero.
• The rain contaminated everything it came in contact with, and dead fish were reported floating in water bodies and severely ill cattle were seen lying in the fields.
• It has caused acute radiation symptoms (ARS) in many who were exposed to it, with reports of people suffering from nausea and diarrhoea for weeks.
• Other ARS include fever, sore throat and loss of hair. Over time, many people who were exposed to black rain have developed cancer.