Judul: Equilibration-time effects on phosphate adsorption by nano and clay fractions extracted from volcanic tuff of Mount Salak, Bogor
Abstrak: Pemanfaatan material nano alami (nanoclay) sebagai flokulan dalam pengolahan air terkontaminasi P dilaporkan lebih efektif, murah dan ramah lingkungan daripada bahan kimia sintetik (Yuan dan Wu, 2007). Indonesia kaya tanah berbahan induk tuf volkan yang banyak mengandung material nano alami (diameter [Φ] <100 nm), yaitu alofan dan imogolit yang memiliki sifat muatan bergantung-pH (Sugiarti et al., 2010). Tuf volkan di Pulau Jawa dari arah timur ke barat berubah dari tipe basa (calc-alkaline basaltic ash) ke masam (andesitic-tuffaceous ash) (Tan, 1964; van Ranst et al., 2004), sehingga fraksi nanonya juga berubah ke dominan bermuatan positif. Dari 12 sampel tuf volkan di Pulau Jawa, fraksi nano bermuatan positif terbanyak dapat diekstraksi dari tuf volkan G. Salak, Bogor (Sherlie, 2010; Nursyirwan, 2010; Setiawan, 2010). Salah satu faktor penentu jerapan P adalah waktu ekuilibrasi. Dalam pengolahan air terkontaminasi P dipilih flokulan dengan waktu ekuilibrasi tercepat dan jerapan maksimum P tertinggi. Penelitian ini bertujuan menguji pengaruh waktu ekuilibrasi terhadap jerapan maksimum P pada fraksi nano dan liat yang diekstraksi dari tuf volkan G. Salak, Bogor. Penelitian ini dilakukan di Lab. Kimia dan Kesuburan Tanah, DITSL, IPB pada Februari-Juli 2011. Ekstraksi fraksi nano dan liat dilakukan dengan metode Henmi dan Wada (1976) sbb: dispersi tuf volkan (Φ <2 mm) dalam silinder 1-L pada pH-4.00 [HCl] dan diultrasonic [15 mnt], sedimentasi [20 jam], pemisahan 10 cm larutan teratas, flokulasi [NaCl], redispersi flokulat [aquadest], pemisahan dengan sentrifugasi 9 kali [3500 rpm; 15 mnt] fraksi nano (tidak mengendap, Φ <0.2 μm) dari liat (mengendap, Φ <2 μm), reflokulasi, pencucian kelebihan NaCl [membran dialisis], pelarutan [500 cc aquadest] dan uji gravimetrik penetapan kadar fraksi nano dan liat. Analisis jerapan isotermal P dilakukan dengan menambahkan 5 cc deret larutan 0, 5, 10, 20, 40, 80, 160 dan 240 mg P/L dalam 1 mM CaCl2 ke tabung reaksi berisi 10 cc suspensi dengan waktu ekuilibrasi 24, 72 dan 144 jam (setiap hari suspensi diagitasi 3x10 dtk menggunakan magnetic stirrer pada jam 08 dan 16). Kadar P-kesetimbangan diukur dengan metode Murphy dan Riley (1962) menggunakan UV-Vis spektrofotometer [λ 660 nm]. Dari setiap 1.00 g tuf volkan G. Salak dapat diekstraksi 2.71 mg fraksi nano dan 3.88 mg fraksi liat bermuatan positif. Jerapan P pada kedua fraksi tersebut meningkat dengan bertambahnya waktu ekuilibrasi. Nilai b (jerapan maksimum P) dengan waktu ekuilibrasi 24, 72 dan 144 jam pada fraksi nano [14.51, 25.13 dan 32.79 mg/g] lebih tinggi daripada fraksi liat [4.60, 20.37 dan 25.13 mg/g]. Nilai b fraksi nano G. Salak [32.79 mg/g; 144 jam] berturut-turut sekitar dua dan delapan kali lebih tinggi daripada nanoclay China [16.23 mg/g; 24 jam; Yuan dan Wu (2007)] dan imogolit New Zealand [3.75 mg/g;16 jam; Parfitt dan Henmi (1980)].
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Judul: Extraction of Nano Fraction from Volcanic Tuff of Mount Salak, West Java and Its Phosphate-adsorption Characterization
Abstrak: Nanoscience and nanotechnology is currently growing very rapidly. In 2003, Abidin (2003 in Sugiarti et al.,2010) discovered the chemical structure of nanoball allophane and nanotube imogolith so that these two clay minerals, previously considered to be amorphous, are now known as crystalline with nano dimension (<5 nm). Therefore, these pH-dependent charged allophane and imogolith pose high specific surface area and adsorption capacity of anions such as P and cations such as NH4. However, research publication on the potential use of allophane and imogolith from volcanic soils of Indonesia as natural nanomaterial in non-agricultural application is difficult to find. This study was aimed at to: (1) explore, select and extract nano fraction from volcanic tuff materials of Central Java and West Java, (2) know the phosphate adsorption characteristic of the selected nano fraction, and (3) study its usage prospects in phospahte contaminated (waste) water treatment process. Based on geology maps, exploration and sampling of the volcanic tuff material was carried out in 15 points that spread from Tawangmangu, Central Java to Bogor, West Java, in February 2010. The nano fraction sample preparation, extraction and phosphate-adsorption characterization were carried out in the Lab. Soil Chemistry and Soil Fertility, Dep. Soil Science and Land Resource, IPB in March-July 2010. Based on dispersion test, nano fraction containing volcanic tuffs were selected and extracted with the following steps: dispersion in a 1 L-cylinder at pH-4 or pH-10 placed in an ultrasonic apparatus [15 min], sedimentation [20 hours], separation of the top 10 cm solution [containing nano and clay fractions], flocculation with NaCl, redispersion, separation of the nano fraction (which did not settled, <0.2 μm) from the clay fraction (which settled, <2 μm) by mean of centrifugation [3500 rpm, 15 min], flocculation and washing the excess NaCl using dialysis membrane, dilution with distilled water [250 cc] and gravi-metrically determination of the amount of the nano and clay fractions. The Langmuir isothermal P-adsorption characterization was done by adding solutions containing 0, 0.5, 1, 2.5, 5, 10, 20, 30, 40 and 50 mg P/L. The P concentration at equilibrium was measured by UV-Vis spectrophotometer at λ 660 nm. From 1 g of volcanic tuff of M. Salak, Bogor, West Java, it could be extracted 0.71 mg positively charged nano fraction and 1.52 mg clay fraction only by applying the simple principle of dispersion at pH-4 and flocculation. The nano fraction was more effective than the clay one in adsorbing P with an average of 27-58% and 15-32%, respectively, of the initial P concentration with a range up to 15.63 mg P/L. The P adsorption effectiveness increased with the increasing ratio of fraction:solution or the weight of fraction used. The positively charged nano fraction extracted from volcanic tuff of M. Salak was found prospective to be used as a flocculant in P contaminated (waste) water treatment.
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Judul: Grup dan Homomorfisma Grup pada Rubik Revenge
Abstrak: Rubik cube is a kind of puzzle game. A player must arrange rubik sides, which have been disordered, back to the position where every side has the same colour. This paper does not focus on the settlement solution, but instead on proving the existence of a group homomorphism between rubik movement group and S96 symmetric permutation group in rubik revenge. Firstly, it has been proved that rubik movement set is a group. Then, it also has been proved that the M set, which contains numeric labels of 1 until 96 in cubinos sides, is S96 symmetric permutation group.
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