Nickel: Properties, Reactions, Health and Environmental Impacts
Nickel: Properties, Reactions, Health, and Environmental Impacts
Chemical Properties of Nickel
Nickel (Ni), atomic number 28, is a hard, silvery-white, ductile, and malleable metal. Its atomic mass is 58.71. Nickel is primarily used in stainless steel and other corrosion-resistant alloys. It is also used in currencies as a silver substitute. Finely divided nickel serves as a catalyst for hydrogenation.
Chemical Reactions of Nickel
- Sodium Hydroxide (NaOH) Solutions: Forms a green nickel oxide precipitate, insoluble in excess reagent. This precipitate dissolves in ammonium hydroxide or ammonium salt solutions, forming blue-green solutions of ammonia complex ions.
- Ammonium Hydroxide Solution: Creates a green precipitate of a basic salt, soluble in excess reagent, forming complex nickel ammonium compounds.
- Ammonium Sulfide Solution: In neutral solutions, it forms a black precipitate of nickel sulfide, sparingly soluble in excess reagent, creating a colloidal solution that turns brown to dark brown when dried. Boiling or acidifying this solution with acetic acid causes clotting, allowing filtration.
- Hydrogen Sulfide: In neutral solutions, nickel partially and slowly precipitates as nickel sulfide. No precipitation occurs in acidic solutions with high concentrations of acetic acid.
- Potassium Cyanide Solution: A green precipitate of nickel cyanide is formed, readily soluble in excess reagent to form the potassium salt complex, nickelocyanide.
Nickel and Human Health
Nickel is a trace element found in the environment. It is widely used in various applications, most commonly as a component of steel and other metal products, including jewelry. Foods like chocolate and fats naturally contain small amounts of nickel. Nickel intake increases when consuming large quantities of vegetables from contaminated soils, as plants accumulate nickel. Smokers have higher nickel exposure through their lungs. Nickel is also present in detergents.
Humans are exposed to nickel through inhalation, ingestion, and skin contact. While small amounts of nickel are essential, excessive intake can be hazardous to human health.
Consequences of High Nickel Exposure
- Increased risk of lung, nose, larynx, and prostate cancers
- Dizziness and illness after exposure to nickel gas
- Pulmonary embolism
- Respiratory failure
- Birth defects
- Chronic bronchitis
- Asthma
- Allergic reactions, such as skin rashes, primarily from jewelry
- Heart disorders
Dermatological Effects of Nickel on Cellular Health
Some mobile phone users develop rashes on their face and ears due to allergic reactions to nickel in electronic devices. This phenomenon is common in individuals who spend long periods talking on their cell phones. Nickel is often found in the handset casing or keyboard. Individuals with nickel allergies from jewelry are at an increased risk of developing rashes from their phones. Nickel allergy is a common contact allergy, affecting approximately 30% of the population. Several case reports have linked unexplained rashes on the face and ears to mobile phone use.
Nickel and the Environment
Nickel is released into the air by power plants and incinerators, eventually depositing on the ground or falling with raindrops. It takes a long time for nickel to be removed from the air. Nickel also enters water bodies through wastewater. Most nickel compounds released into the atmosphere are absorbed by sediment or soil particles, becoming immobilized. In acidic soils, nickel becomes more mobile and can reach groundwater.
Effects of Nickel on Organisms
- High nickel concentrations in sandy soils can damage plants.
- High nickel concentrations in surface waters can reduce algal growth.
- Microorganisms may experience growth decline due to nickel, but they often develop resistance.
- For animals, nickel is essential in small quantities but can be dangerous in high amounts, potentially causing various cancers, especially in animals near refineries.
- Nickel accumulates in plants and animals, leading to biomagnification in the food chain.