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Glossary of Technical Terms Used in Waste Management: deliquescent

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Deliquescence: A Silent Threat in Environmental and Water Treatment

In the realm of environmental and water treatment, understanding the properties of materials is crucial. Deliquescence, the ability of a dry solid to absorb moisture from the air and dissolve, plays a significant role in various processes and presents unique challenges.

What is Deliquescence?

Imagine leaving a block of salt out in humid weather. You might notice it becoming damp and eventually dissolving into a puddle of brine. This is deliquescence in action.

The Process:

  • Hygroscopic Nature: Deliquescent substances are highly hygroscopic, meaning they have a strong affinity for water molecules.
  • Vapor Pressure: The vapor pressure of a deliquescent substance is lower than the partial pressure of water vapor in the air. This difference in pressure drives the absorption of water from the atmosphere.
  • Dissolution: As water is absorbed, the substance softens and eventually dissolves, forming a concentrated solution.

Impact on Environmental and Water Treatment:

  • Corrosion: Deliquescent substances can corrode metal surfaces, impacting infrastructure and equipment used in water treatment facilities.
  • Chemical Reactions: The presence of dissolved deliquescent substances can alter the chemical composition of water, affecting treatment processes and the quality of the treated water.
  • Dust Control: Deliquescent salts are sometimes used for dust control in various industrial applications. They absorb moisture, creating a damp surface that reduces dust generation.
  • Waste Management: Deliquescent materials can pose challenges in waste management. They can absorb moisture, leading to increased volume and potential environmental hazards.

Examples of Deliquescent Substances:

  • Sodium chloride (NaCl) (Table salt)
  • Calcium chloride (CaCl2)
  • Potassium hydroxide (KOH)
  • Magnesium chloride (MgCl2)
  • Sodium hydroxide (NaOH)

Controlling Deliquescence:

  • Storage: Store deliquescent substances in airtight containers to minimize exposure to air moisture.
  • Environmental Control: Maintain a low humidity environment in storage areas and treatment facilities.
  • Additives: Using additives that inhibit moisture absorption can help mitigate deliquescence.

Conclusion:

Deliquescence is a phenomenon that plays a significant role in various environmental and water treatment processes. Understanding its properties and potential impacts is essential for ensuring the effective operation of treatment facilities and minimizing the risks associated with these substances. By implementing proper storage and control measures, we can mitigate the challenges posed by deliquescence and ensure the integrity of our water resources.

Test Your Knowledge

Deliquescence Quiz

Instructions: Choose the best answer for each question.

1. What is the primary characteristic of a deliquescent substance?

a) It readily reacts with acids. b) It absorbs moisture from the air and dissolves. c) It has a high melting point. d) It is flammable.

Answer

b) It absorbs moisture from the air and dissolves.

2. Which of the following is NOT a typical example of a deliquescent substance?

a) Sodium chloride (NaCl) b) Calcium chloride (CaCl2) c) Potassium hydroxide (KOH) d) Carbon dioxide (CO2)

Answer

d) Carbon dioxide (CO2)

3. How can deliquescence impact water treatment facilities?

a) It can enhance water filtration. b) It can corrode metal equipment. c) It can increase the effectiveness of disinfection. d) It can prevent the growth of algae in reservoirs.

Answer

b) It can corrode metal equipment.

4. Which of the following is a common method for controlling deliquescence?

a) Increasing the humidity in storage areas. b) Storing deliquescent substances in open containers. c) Using additives that inhibit moisture absorption. d) Exposing deliquescent materials to direct sunlight.

Answer

c) Using additives that inhibit moisture absorption.

5. Deliquescence is used in some industrial applications for what purpose?

a) Producing fertilizers. b) Cleaning metal surfaces. c) Dust control. d) Creating artificial rain.

Answer

c) Dust control.

Deliquescence Exercise

Scenario: You are working at a water treatment plant, and you notice that the metal pipes are showing signs of corrosion. You suspect that deliquescent substances stored nearby might be contributing to the problem.

Task:

  1. Identify: List at least three possible deliquescent substances that could be stored near the water treatment plant and contribute to the corrosion.
  2. Explain: Briefly explain how these deliquescent substances can cause corrosion of metal pipes.
  3. Solution: Suggest at least two practical solutions to mitigate the corrosion problem.

Exercise Correction

**1. Identify:** * **Calcium chloride (CaCl2):** Commonly used for de-icing and dust control. * **Sodium hydroxide (NaOH):** Used in water treatment for pH adjustment. * **Magnesium chloride (MgCl2):** Often used as a de-icing agent. **2. Explain:** Deliquescent substances absorb moisture from the air and dissolve, forming concentrated solutions. When these solutions come into contact with metal surfaces, they can cause corrosion due to several factors: * **Electrochemical Reactions:** The dissolved salts can act as electrolytes, accelerating electrochemical reactions that lead to metal oxidation. * **pH Changes:** The pH of the solutions can be acidic or alkaline, further contributing to metal degradation. * **Physical Damage:** The constant presence of moisture can weaken the metal structure and promote pitting. **3. Solution:** * **Relocate Storage:** Move the deliquescent substances to a location further away from the metal pipes and ensure proper ventilation in the storage area. * **Protective Coatings:** Apply protective coatings to the pipes, such as epoxy or zinc-based coatings, to prevent direct contact with the corrosive solutions.

Books

  • Chemistry: The Central Science by Theodore L. Brown, H. Eugine LeMay Jr., and Bruce E. Bursten. This comprehensive chemistry textbook covers deliquescence in the context of solutions and colligative properties.
  • Environmental Engineering: Fundamentals, Sustainability, Design by Davis, Cornwell, and Masten. This book covers the principles of environmental engineering and the impact of deliquescent substances on water treatment.
  • Water Treatment Plant Design by AWWA (American Water Works Association). This book explores different aspects of water treatment, including the effects of deliquescent materials on plant operations.

Articles

  • Deliquescence of Inorganic Salts: A Review by A.N. Campbell and E.W.R. Steacie, Transactions of the Faraday Society, Vol. 30, pp. 564-577, 1934. This classic paper provides a thorough examination of the deliquescence phenomenon.
  • The Role of Deliquescence in Dust Control by K.D. Kringle, J. Environ. Eng., Vol. 136, No. 11, pp. 1055-1060, 2010. This article explores the use of deliquescent materials in dust control applications.
  • Deliquescence and its Effects on Salt Leaching in Concrete by A.M. Neville, ACI Materials Journal, Vol. 95, No. 6, pp. 529-537, 1998. This article examines the impact of deliquescence on concrete durability.

Online Resources


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