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1. Introduction
to the extraction of metals What
methods can use in extracting metals from mineral ores?
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The Earth's crust contains many different
rocks. Rocks are a mixture of minerals and from some we
can make useful
substances.
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A mineral can be a solid metallic
or non-metallic element or a compound found naturally in the
Earth's crust.
-
A metal ore is a mineral or mixture of
minerals from which economically viable amounts of metal can be extracted, i.e. its got to have enough of the metal, or one of its
compounds, in it to be worth digging out!
Ores are often oxides, carbonates or sulphides. They are all
finite resources so we should use them wisely!
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 In order to extract a
metal, the ore or compound of the metal must undergo a process
called reduction to free the metal i.e. the positive metal ion gains
negative electrons to form the neutral metal atom, or the oxide loses oxygen, to form the free
metallic atoms.
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The chemical
that removes the oxygen from an oxide is called the reducing
agent i.e. carbon, carbon monoxide or sometimes
hydrogen.
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Detailed
REDOX notes on the metal reactivity page, and on this page
where appropriate.
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Generally speaking the
method of extraction depends on the metals position in the reactivity
series
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The reactivity series of
metals can be presented to include two non-metals, carbon and
hydrogen, to help
predict which method could be used to extract the metal.
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Metals above zinc and
carbon in the reactivity series cannot usually be extracted
with carbon or carbon monoxide. They are usually extracted by electrolysis
of the purified molten ore or other suitable compound
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e.g. aluminium
from molten aluminium oxide or sodium from molten sodium chloride.
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The ore or
compound must be molten or dissolved in a solution in an electrolysis cell to allow
free movement of ions (electrical current). Theory given in the
appropriate sections.
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Metals below carbon
can be extracted by heating the oxide with carbon or carbon monoxide. The non-metallic elements
carbon will displace
the less reactive metals in a smelter or blast furnace
e.g.
iron or zinc and metals lower in the series.
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Metals below
hydrogen will not displace hydrogen from acids. Their oxides
are easily reduced to the metal by heating in a stream of
hydrogen, though this is an extraction method rarely used in
industry. In fact most metal oxides below carbon can be reduced
when heated in hydrogen, even if the metal reacts with acid.
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Some metals are so
unreactive that they do not readily combine with oxygen in the air
or any other element
present in the Earth's crust, and so can be found as the metal
itself. For example gold (and sometimes copper and silver)
and no chemical separation or extraction is needed. In fact all the
metals below hydrogen can be found as the 'free' or 'native' element.
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Other methods are used in
special cases using the displacement rule.
A more reactive
metal can be used to displace and extract a less reactive metal but these are
costly processes since the more reactive metal also has to be produced
in the first place! See Titanium or see
at the end of the section on copper
extraction.
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Sometimes electrolysis
is used to purify less reactive metals which have previously been
extracted using carbon or hydrogen (e.g. copper and
Mextractd.htm).
Electrolysis is also used to plate one metal with another.
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The demand for raw
materials does have social, economic and environmental implications
e.g.
conservation of mineral resources by recycling metals, minimising
pollution etc.
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Historically as
technology and science have developed the methods of extraction
have improved to the point were all metals can be produced. The
reactivity is a measure of the ease of compound formation and
stability (i.e. more reactive, more readily formed stable compound, more
difficult to reduce to the metal).
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The least
reactive metals such as gold, silver and copper have been used for
the past 10000 years because the pure metal was found
naturally.
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Moderately reactive metals like iron and tin
have been extracted using carbon based smelting for the past 2000-3000
years.
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BUT it is only in the last 200 years that very reactive metals
like sodium or aluminium have been extracted by electrolysis.
|
(spanish) Doc Brown de
Química Extracción de Minerales y métodos de extracción de
los metales Introducción a la extracción de metales
Desplácese hacia abajo para las notas de revisión sobre los
procedimientos de extracción y la teoría Útiles para la
escuela / universidad asignaciones o proyectos sobre la
manera de extraer los metales de sus minerales Introducción
a la extracción de metales * 2. Extracción de hierro y acero
Extracción de aluminio y de sodio * 4. Extracción y
purificación del cobre La extracción de zinc, titanio y
cromo * 6. Economía y Asuntos de medio ambiente - la
extracción de metales * (portuguese) Doc Brown de Química A
exploração de minerais e Métodos de Extração de Metais
Introdução à extracção de metais Role para baixo para as
notas de revisão sobre os procedimentos de extração e teoria
Úteis para a escola atribuições faculdade / projectos sobre
as formas de extração de metais a partir de seus minérios (arabic)
مستدات براون الكيمياء تعدين المعادن وطرق استخراج المعادن
مقدمة لاستخراج المعادن انتقل لأسفل لتلاحظ على تنقيح إجراءات
استخراج ونظرية مفيدة للمدرسة مهام الكلية / / المشاريع
حول سبل استخراج المعادن من خاماتها مقدمة لاستخراج المعادن *
2. استخلاص الحديد والصلب صناعة استخراج الألمنيوم والصوديوم *
4. استخراج وتنقية النحاس استخراج الزنك ، والتيتانيوم والكروم
* 6.القضايا الاقتصادية والبيئية -- استخراج المعادن *
(chinese) 督布朗的化学 开采矿物和金属的提取方法 介绍金属提取 向下滚动修订的笔记和理论的提取程序
项目有用的学校/学院作业/对矿石中提取金属的方法从 介绍金属的提取 制作提取钢铁 提取铝和钠 提取和纯化铜
铬提取锌，钛及 * 。经济与环境问题-金属提取 * |
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