Zeolit sebagai Mineral Serba Guna

Photo zeolite granular size 2-5 mm produk PT. Khatulistiwa Hijau Prima (Bojong, Sukabumi)

Zeolit (Zeinlithos) atau berarti juga batuan mendidih, di dalam riset-riset kimiawan telah lama menjadi pusat perhatian. Setiap tahunnya, berbagai jurnal penelitian di seluruh dunia, selalu memuat pemanfaatan zeolit untuk berbagai aplikasi, terutama yang diarahkan pada aspek peningkatan efektivitas dan efisiensi proses industri dan pencemaran lingkungan.

Zeolit umumnya didefinisikan sebagai kristal alumina silika yang berstruktur tiga dimensi, yang terbentuk dari tetrahedral alumina dan silika dengan rongga-rongga di dalam yang berisi ion-ion logam, biasanya alkali atau alkali tanah dan molekul air yang dapat bergerak bebas. Secara empiris, rumus molekul zeolit adalah M_x/n.(AlO₂)_x.(SiO₂)_y.xH₂O. Struktur zeolit sejauh ini diketahui bermacam-macam, tetapi secara garis besar strukturnya terbentuk dari unit bangun primer, berupa tetrahedral yang kemudian menjadi unit bangun sekunder polihedral dan membentuk polihendra dan akhirnya unit struktur zeolit.

Berikut adalah beberapa contoh jenis mineral zeolit beserta rumus kimianya :

Nama Mineral	Rumus Kimia Unit Sel
Analsim	Na16(Al16Si32O96). 16H2O
Kabasit	(Na2,Ca)6 (Al12Si24O72). 40H2O
Klipnoptolotit	(Na4K4)(Al8Si40O96). 24H2O
Erionit	(Na,Ca5K) (Al9Si27O72). 27H2O
Ferrierit	(Na2Mg2)(Al6Si30O72). 18H2O
Heulandit	Ca4(Al8Si28O72). 24H2O
Laumonit	Ca(Al8Si16O48). 16H2O
Mordenit	Na8(Al8Si40O96). 24H2O
Filipsit	(Na,K)10(Al10Si22O64). 20H2O
Natrolit	Na4(Al4Si6O20). 4H2O
Wairakit	Ca(Al2Si4O12). 12H2O

Di Indonesia, jumlah zeolit sangat melimpah dan tersebar di berbagai daerah baik di pulau Jawa, Sumatera, dan Sulawesi. Pemanfaatan zeolit Indonesia untuk penggunaan secara langsung belum dapat dilakukan, karena zeolit Indonesia banyak mengandung campuran (impurities) sehingga perlu dilakukan pengolahan terlebih dahulu untuk menghilangkan atau memisahkannya dari kotoran-kotoran.

Sifat Unik Zeolit

Karena sifat fisika dan kimia dari zeolit yang unik, sehingga dalam dasawarsa ini, zeolit oleh para peneliti dijadikan sebagai mineral serba guna. Sifat-sifat unik tersebut meliputi dehidrasi, adsorben dan penyaring molekul, katalisator dan penukar ion.

Zeolit mempunyai sifat dehidrasi (melepaskan molekul H₂0) apabila dipanaskan. Pada umumnya struktur kerangka zeolit akan menyusut. Tetapi kerangka dasarnya tidak mengalami perubahan secara nyata. Disini molekul H₂O seolah-olah mempunyai posisi yang spesifik dan dapat dikeluarkan secara reversibel. Sifat zeolit sebagai adsorben dan penyaring molekul, dimungkinkan karena struktur zeolit yang berongga, sehingga zeolit mampu menyerap sejumlah besar molekul yang berukuran lebih kecil atau sesuai dengan ukuran rongganya. Selain itu kristal zeolit yang telah terdehidrasi merupakan adsorben yang selektif dan mempunyai efektivitas adsorpsi yang tinggi.

Kemampuan zeolit sebagai katalis berkaitan dengan tersedianya pusat-pusat aktif dalam saluran antar zeolit. Pusat-pusat aktif tersebut terbentuk karena adanya gugus fungsi asam tipe Bronsted maupun Lewis. Perbandingan kedua jenis asam ini tergantung pada proses aktivasi zeolit dan kondisi reaksi. Pusat-pusat aktif yang bersifat asam ini selanjutnya dapat mengikat molekul-molekul basa secara kimiawi. Sedangkan sifat zeolit sebagai penukar ion karena adanya kation logam alkali dan alkali tanah. Kation tersebut dapat bergerak bebas didalam rongga dan dapat dipertukarkan dengan kation logam lain dengan jumlah yang sama. Akibat struktur zeolit berongga, anion atau molekul berukuran lebih kecil atau sama dengan rongga dapat masuk dan terjebak.

Aplikasi Zeolit

Seperti telah disinggung diatas, bahwasanya dalam dasawarsa ini, zeolt telah dimanfaatkan secara luas oleh masyarakat. Berikut adalah beberapa contoh aplikasinya :

Bidang/Sektor	Aplikasi
Pertanian	Penetral keasaman tanah, meningkatkan aerasi tanah, sumber mineral pendukung pada pupuk dan tanah, serta sebagai pengontrol yang efektif dalam pembebasan ion amonium, nitrogen, dan kalium pupuk.
Peternakan	Meningkatkan nilai efisiensi nitrogen, dapat mereduksi penyakit lembuhg pada hewan ruminensia, pengontrol kelembaban kotoran hewan dan kandungan amonia kotoran hewan.
Perikanan	Membersihkan air kolam ikan yang mempunyai sistem resikurlasi air, dapat mengurangi kadar nirogen pada kolam ikan.
Energi	Sebagai katalis pada proses pemecahan hidrokarbon minyak bumi, sebagai panel-panel pada pengembangan energi matahari, dan penyerap gas freon.
Industri	Pengisi (filler) pada industri kertas, semen, beton, kayu lapis, besi baja, dan besi tuang, adsorben dalam industri tekstil dan minyak sawit, bahan baku pembuatan keramik.

Daftar Pustaka

• Bambang Setiaji. 2000. Pemanfaatan Zeolit untuk Adsorpsi Benzopiren sebagai Senyawa Racun dalam Asap Cair. Majalah Iptek Vo. 11, No. 4, November 2000.
• Muhammad Rif’an. 2005. Zeolit, Kristal Ajaib dari Gunung Berapi. Majalah ACID Edisi III/Tahun V/Mei 2005. Bandar Lampung
• Najib I. 1994. Pengaruh Pengaktifan Zeolit Lampung dengan Asam Sulfat sebagai Adsorben Ion Amonium. Skripsi Kimia Univ. Lampung. Bandar Lampung
• Prayitno, KB. 1989. Zeolit sebgai Alternatif Industri Komoditi Mineral Indonesia. BPPT No. XXXV.
• Rudy Situmeang. 2006. Kimia Katalis. Diktat Kuliah. Bandar Lampung
• Sujarwadi. 1997. Sekilas tentang Zeolit. Pusat Pengembangan Teknologi Mineral. Bandung
• Susanto dan Suharso. 1999. Pemisahan Ion-ion Besi dalam Air dengan Zeolit Alam yang Diaktifasi. Jurnal Univ. Lampung. Bandar Lampung

Read More

These are the members of the Zeolite Group

• The Analcime Family:

• Analcime (Hydrated Sodium Aluminum Silicate)
• Pollucite (Hydrated Cesium Sodium Aluminum Silicate)
• Wairakite (Hydrated Calcium Sodium Aluminum Silicate)
  

• Bellbergite (Hydrated Potassium Barium Strontium Sodium Aluminum Silicate)
• Bikitaite (Hydrated Lithium Aluminum Silicate)
• Boggsite (Hydrated calcium Sodium Aluminum Silicate)
• Brewsterite (Hydrated Strontium Barium Sodium Calcium Aluminum Silicate)
• The Chabazite Family:

• o Chabazite (Hydrated Calcium Aluminum Silicate)
• o Willhendersonite (Hydrated Potassium Calcium Aluminum Silicate)

• Cowlesite (Hydrated Calcium Aluminum Silicate)
• Dachiardite (Hydrated calcium Sodium Potassium Aluminum Silicate)
• Edingtonite (Hydrated Barium Calcium Aluminum Silicate)
• Epistilbite (Hydrated Calcium Aluminum Silicate)
• Erionite (Hydrated Sodium Potassium Calcium Aluminum Silicate)
• Faujasite (Hydrated Sodium Calcium Magnesium Aluminum Silicate)
• Ferrierite (Hydrated Sodium Potassium Magnesium Calcium Aluminum Silicate)
• The Gismondine Family:

• o Amicite (Hydrated Potassium Sodium Aluminum Silicate)
• o Garronite (Hydrated Calcium Aluminum Silicate)
• o Gismondine (Hydrated Barium Calcium Aluminum Silicate)
• o Gobbinsite (Hydrated Sodium Potassium Calcium Aluminum Silicate)

• Gmelinite (Hydrated Sodium Calcium Aluminum Silicate)
• Gonnardite (Hydrated Sodium Calcium Aluminum Silicate)
• Goosecreekite (Hydrated Calcium Aluminum Silicate)
• The Harmotome Family:

• o Harmotome (Hydrated Barium Potassium Aluminum Silicate)
• o Phillipsite (Hydrated Potassium Sodium Calcium Aluminum Silicate)
• o Wellsite (Hydrated Barium Calcium Potassium Aluminum Silicate)

• The Heulandite Family:

• o Clinoptilolite (Hydrated Sodium Potassium Calcium Aluminum Silicate)
• o Heulandite (Hydrated Sodium Calcium Aluminum Silicate)

• Laumontite (Hydrated Calcium Aluminum Silicate)
• Levyne (Hydrated Calcium Sodium Potassium Aluminum Silicate)
• Mazzite (Hydrated Potassium Sodium Magnesium Calcium Aluminum Silicate)
• Merlinoite (Hydrated Potassium Sodium Calcium Barium Aluminum Silicate)
• Montesommaite (Hydrated Potassium Sodium Aluminum Silicate)
• Mordenite (Hydrated Sodium Potassium Calcium Aluminum Silicate)
• The Natrolite Family:

• o Mesolite (Hydrated Sodium Calcium Aluminum Silicate)
• o Natrolite (Hydrated Sodium Aluminum Silicate)
• o Scolecite (Hydrated Calcium Aluminum Silicate)

• Offretite (Hydrated Calcium Potassium Magnesium Aluminum Silicate)
• Paranatrolite (Hydrated Sodium Aluminum Silicate)
• Paulingite (Hydrated Potassium Calcium Sodium Barium Aluminum Silicate)
• Perlialite (Hydrated Potassium Sodium Calcium Strontium Aluminum Silicate)
• The Stilbite Family:

• o Barrerite (Hydrated Sodium Potassium Calcium Aluminum Silicate)
• o Stilbite (Hydrated Sodium Calcium Aluminum Silicate)
• o Stellerite (Hydrated Calcium Aluminum Silicate)

• Thomsonite (Hydrated Sodium Calcium Aluminum Silicate)
• Tschernichite (Hydrated Calcium Aluminum Silicate)
• Yugawaralite (Hydrated Calcium Aluminum Silicate)

Zeolites have many "cousins" or minerals that have similar cage-like framework structures or have similar properties and/or are associated with zeolites; but are not zeolites, at least as defined mineralogically. These include the phosphates: kehoeite, pahasapaite and tiptopite; and the silicates: hsianghualite, lovdarite, viseite, partheite, prehnite, roggianite, apophyllite, gyrolite, maricopaite, okenite, tacharanite and tobermorite. It is interesting to compare these minerals to the zeolites.

Read More

The Zeolite Group of Minerals

Photo zeolite rock in stock filed PT Khatulistiwa Hijau Prima (Bojong, Sukabumi)

The zeolites are a popular group of minerals for collectors and an important group of minerals for industrial and other purposes. They combine rarity, beauty, complexity and unique crystal habits. Typically forming in the cavities, or vesicles, of volcanic rocks, zeolites are the result of very low grade metamorphism. Some form from just subtle amounts of heat and pressure and can just barely be called metamorphic while others are found in obviously metamorphic regimes. Zeolite crystals have been grown on board the space shuttle and are undergoing extensive research into their formation and unique properties.

The zeolites are framework silicates consisting of interlocking tetrahedrons of SiO4 and AlO4. In order to be a zeolite the ratio (Si +Al)/O must equal 1/2. The alumino-silicate structure is negatively charged and attracts the positive cations that reside within. Unlike most other tectosilicates, zeolites have large vacant spaces or cages in their structures that allow space for large cations such as sodium, potassium, barium and calcium and even relatively large molecules and cation groups such as water, ammonia, carbonate ions and nitrate ions. In the more useful zeolites, the spaces are interconnected and form long wide channels of varying sizes depending on the mineral. These channels allow the easy movement of the resident ions and molecules into and out of the structure. Zeolites are characterized by their ability to lose and absorb water without damage to their crystal structures. The large channels explain the consistent low specific gravity of these minerals.

Zeolites have many useful purposes. They can perform ion exchange, filtering, odor removal, chemical sieve and gas absorption tasks. The most well known use for zeolites is in water softeners. Calcium in water can cause it to be "hard" and capable of forming scum and other problems. Zeolites charged with the much less damaging sodium ions can allow the hard water to pass through its structure and exchange the calcium for the sodium ions. This process is reversable. In a similar way zeolites can absorb ions and molecules and thus act as a filter for odor control, toxin removal and as a chemical sieve. Zeolites can have the water in their structures driven off by heat with the basic structure left intact. Then other solutions can be pushed through the structure. The zeolites can then act as a delivery system for the new fluid. This process has applications in medicine, livestock feeds and other types of research. Zeolites added to livestock feed have been shown to absorb toxins that are damaging and even fatal to the growth of the animals, while the basic structure of the zeolite is biologically neutral. Aquarium hobbyists are seeing more zeolite products in pet stores as zeolites make excellent removers of ammonia and other toxins. Most municipal water supplies are processed through zeolites before public consumption. These uses of zeolites are extremely important for industry, although synthetic zeolites are now doing the bulk of the work.

Zeolites have basically three different structural variations.

1. There are chain-like structures whose minerals form acicular or needle-like prismatic crystals, ie natrolite.
2. Sheet-like structures where the crystals are flattened platy or tabular with usually good basal cleavages, ie heulandite.
3. And framework structures where the crystals are more equant in dimensions, ie Chabazite

A zeolite can be thought of in terms of a house, where the structure of the house (the doors, windows, walls and roof) is really the zeolite while the furniture and people are the water, ammonia and other molecules and ions that can pass in and out of the structure. The chain-like structures can be thought of like towers or high wire pylons. The sheet-like structures can be thought of like large office buildings with the sheets analogous to the floors and very few walls between the floors. And the framework structures like houses with equally solid walls and floors. All these structures are still frameworks (like the true tectosilicates that zeolites are).

These variations make the zeolite group very diverse, crystal habit-wise. Otherwise zeolites are typically soft to moderately hard, light in density, transparent to translucent and have similar origins. There are about 45 natural minerals that are recognized members of the Zeolite Group. Industrially speaking, the term zeolite includes natural silicate zeolites, synthetic materials and phosphate minerals that have a zeolite like structure. The complexity of this combined group is extensive with over 120 structural variations and more are being discovered or made every year. Collecting zeolites can be very enjoyable and fulfilling.

Read More