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: Ekstraksi Fraksi Nano dari Tuf Volkan Gunung Lawu, Jawa Tengah dan Karakterisasi Jerapannya terhadap Amonium
Abstrak: In the process of purification of water contaminated with nutrients causing eutrophication (P and NH4), the use of natural nano materials as a flocculant was reported to be more effective, cheaper and environmentally friendly than synthetic chemicals (Yuan and Wu, 2007). Indonesia is rich in volcanic soil material that contains allophane and imogolith that pose pH-dependent charge properties, high chemical reactivity, specific surface area and adsorption capacity of anions such as phosphate and cations such as amonium. Both clay minerals that were previously considered to be amorphous aluminosilicate has now been proved by Abidin (2003 in Sugiarti et al., 2010) as crystalline with nano dimension (<5 nm). This study was aimed at to: (1) explore, select and extract nano fraction of volcanic tuff materials from Central Java and West Java, (2) know the NH4-adsorption characteristics of the selected nano fraction, and (3) study the prospects of the selected nano fraction to be used as a natural flocculant in NH4-contaminated (waste) water treatment processes. Based on geological maps, in February 2010, exploration and sampling of the volcanic tuff materials were carried out in 15 points that spread from Tawangmangu, Central Java to Bogor, West Java. The nano fraction sample preparation, extraction and amonium-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 gravimetrically determination of the amount of the nano and clay fractions. The Langmuir isothermal NH4-adsorption characterization was done by adding solutions containing 0, 2.5, 5, 10, 20, 30, 40 and 50 mg NH4/L. Concentrations of NH4 at equilibrium state was measured by UV-Vis spectrophotometer at λ 630 nm. From 1 g volcanic tuff material of M. Lawu, Central Java, it could be extracted 1.19 mg of negatively-charged nano fraction and 1.95 mg of clay fraction only by applying a simple principle of dispersion at pH-10 and flocculation. The nano fraction was more effective than the clay one in NH4-adsorption with an average of 41-68% and 12-20%, respectively, of the initial NH4 concentration with a range up to 16.67 mg NH4/L. The NH4-adsorption effectiveness increased with the increasing ratio of fraction: solution or the weight of fraction used. The negatively-charged nano fraction derived from volcanic tuff of M. Lawu was prospective to be used as a natural flocculant in the process of NH4-contaminated water treatment.
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Judul: Cycle Hamilton pada Graf Lengkap, Graf Regular, dan Graf 2-Connected 4-Regular Berorder Kurang dari Sepuluh.
Abstrak: Suatu graf disebut graf Hamilton apabila graf tersebut memuat cycle Hamilton, yaitu cycle yang melewati setiap vertex tepat satu kali. Menentukan keberadaan cycle Hamilton pada suatu graf dapat menggunakan syarat cukup yang berupa teorema-teorema yang telah diperkenalkan sejak tahun 1950-an. Beberapa syarat cukup yang dibahas dalam karya ilmiah ini adalah syarat cukup yang berhubungan dengan graf lengkap dan graf regular. ,,,
Keyword: graf Hamilton, graf regular, graf lengkap, graf 2-connected 4-regular.