Lixiviation or leaching is an ancient process alchemy still used today in making tea, extracting dyes and ores. Lixivium is a general term for the desired product. Lixiviation extracts soluble material using a solvent, often plain water. It happens in nature, labs and workshops.
Definition of Lixiviation (Leaching)
Derived from the Latin word lixivia , meaning lye, lixiviation is a method of extracting soluble components from a solid substance by washing it with a solvent. This technique has long been used for extracting valuable minerals and compounds from ores and plant materials.
Lixiviation influences disciplines from ancient agriculture to modern applications. This process removes nutrients and minerals from the earth due to water percolation of water. in geology percolation refers to filtration of water through soil and permeable rocks.
Above: Process of Percolation or downward movement of substance such as water
Percolation is the downward movement of water and/or contaminants in an unsaturated zone by force of gravity or hydraulics.
There are many types of leaching methods and conditions. They generally used three substances can be described as:
a carrier, substance A, which contains the solute
a solute, substance B, which dissolves in a solvent
and a solvent, substance C, which absorbs the solute
These terms might not always suit the process. For instance, in making infused oils, the carrier is the oil which receives the infusion. The oil leaches out qualities or essences from the plant parts soaking in it.
The general process in geology can be simplified into three steps:
Dissolution of surficial solute by solvent
Diffusion of inner-solute through the pores of the carrier to reach the solvent
Transfer of dissolved solute out of the system
Leaching is a naturally occurring phenomenon used for various purposes and by different methods. Specific extraction techniques are determined by the solubility traits in relation to the sorbent material, including factors such as concentration, distribution, nature, and size.
Natural leaching occurs in plant substances, soil, and organic matter. Controlled leaching processes can enhance water quality, eliminate contaminants and handle hazardous waste disposal. Understanding lixiviation is vital for managing and preparing for this process.
A Brief History
Lixiviation is used by ancients to extract minerals from ores and purify substances. Egyptians, for example, use lixiviation techniques to extract potash from wood ash. Potash is vital to making soap and fertilizer. Natural fertilization comes from the celebrated Nile floods.
Historically, leaching has a crucial role in mining. During the Middle Ages, miners use water to separate valuable metals from soluble ore. Not considered a scientific method at the time, leaching is a practical way to get essential resources, similar to modern mineral extraction.
Ancient Uses of Lixiviation
In antiquity, people recognize the benefits of lixiviation and apply leaching in various ways:
Salting Out
Members of ancient civilizations collect sea salt by allowing seawater to evaporate, leaving behind the salt crystals. This technique essentially utilized lixiviation to extract valuable minerals. In Neolithic salt processing centers like Solnitsata the briquetage method is used.
Fertilizers
Ancient farmers know leaching can enrich soil by adding soluble minerals. By washing out certain soils, they create more fertile land. Fertility of land for crops, humans and livestock or prey animals is paramount in the ancient world.
Fabric Dyeing
The extraction of dyes from plants such as madder and alkanet often involves lixiviation processes to create the vibrant colors found in ancient textiles.
Extracting valuable materials from wastewater or raw materials can be achieved through leaching. Acid leaching is a common method in mineralogy for extracting metals like vanadium, cobalt, nickel, manganese, and iron from raw or recycled materials.
There is a growing focus on metal leaching to recover precious metals from waste materials, such as extracting valuable metals from wastewater. What a shame they can't extract the toxins too.
Extracting valuable metals from waste is a way of surviving in some parts of the world, as the mining, processing or manufacturing companies destroy traditional livelihoods such as fishing. However once companies realize there's wealth in the waste, that too is gone.
Lixiviation in Sciences
Alchemists often employ leaching techniques to separate different substances or to extract impurities from materials. Lixiviation is a standardized technique today. Modern scientists use lixiviation to isolate specific compounds from mixtures.
This process can be seen in production of beer or during extraction of essential oils. In environmental chemistry, leaching is observed in soil and water interactions.
Lixiviation in Nature
Nature displays the process of lixiviation in various ecosystems. As rainwater seeps through the soil, it interacts with minerals and nutrients, causing a natural leaching effect. This process is vital for nutrient cycling in ecosystems.
Complex cycles of natural lixiviation processes sustain life on Earth. Rainfall serves as a natural solvent, leaching nutrients from the soil and transporting them to plants for growth.
The oceans act as vast lixiviation chambers. The sea dissolves minerals from rocks and releases them into the water, supporting marine ecosystems.
Leaching helps transport essential minerals to plants, while preventing the buildup of harmful substances in soil. For example, natural leaching of calcium carbonate from limestone in karst regions creates stunning geological formations such as caves, hills and sinkholes.
Types of Lixiviation
Lixiviation has practical applications in various industries like metallurgy, pharmaceuticals, and environmental remediation. Chemists isolate desired compounds, remove impurities, and facilitate chemical reactions.
Batch Leaching: Involves the continuous addition of fresh solvent to the material, where the extraction occurs over set intervals. An example can be seen in the production of coffee, where hot water extracts flavor compounds from coffee grounds.
Continuous Leaching: This process uses a consistent flow of solvent through the material, maximizing extraction efficiency. A typical example is the extraction of metal ores in hydrometallurgy, where various solutions continuously pass through ore piles to dissolve soluble metals.
Heap Leaching: This method is used in mining operations, where ores are piled in a heap, and leaching solutions are applied to extract metals like gold and copper from the ore.
Percolation Lixiviation : In this method, a solvent is passed through a permeable substance, gradually extracting soluble components.
In-situ Lixiviation : Applied in environmental remediation, this method involves injecting a solvent into the ground to extract contaminants from soil or groundwater.
Cyanide Leaching : Widely used in gold extraction, cyanide leaching involves treating gold ores with a cyanide solution to dissolve the gold for recovery.
Acidic Lixivium : Acid solutions can be employed to leach metals like copper and uranium from ores, creating solutions rich in these metals.
Lixivium: The Soluble Extract
Lixivium is the solution obtained from the lixiviation process, rich in dissolved substances. For instance, when leaching minerals from soil, the resultant lixivium may contain essential nutrients like potassium, magnesium, and calcium, making it valuable for agricultural purposes.
In the brewing industry, the liquid extracted after soaking grains (wort) is a type of lixivium rich in sugars and other compounds that later ferment into beer.
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