A series of nanoporous carbon was prepared with MOF-5 as a template and furfuryl alcohol as an additional carbon source by carbonation at temperatures of 550 °C and 900 °C, respectively, with and without activation using KOH. XRD patterns of the obtained carbons before and after the activation process showed characteristic peaks at the same 2θ values, which corresponded to the XRD pattern of a ZnO. The Surface morphology of the MOF-5 templated carbon with a carbonation temperature of 550 °C was in the form of a cube. In contrast, the one carbonated at 900 °C had a cubic and circular morphology. The N2 adsorption-desorption isothermal showed that MOF-5 templated carbon had a larger specific surface area, pore diameter, and pore volume than those of the original MOF-5. Activation of the MOF-5 templated carbon using KOH resulted in a decrease in surface area and pore volume. All the materials were measured for their hydrogen adsorption at room temperature and atmospheric pressure using a gravimetric method.
The aim of this work is to study the effect of polyethylene glycol (PEG) on the modification of microstructure formation correlated with the mechanical strength properties of perovskite-based membrane in form of a flat sheet. LSCF 7328 flat membrane was potentially promoted as an oxygen separator and catalyst for partial oxidation of methane reaction at high temperature. In this study, the phase-inversion followed by sintering process was used as the membrane fabrication method using varied PEG concentration of 0.55, 1.00, and 3.00 wt% with different molecular weight, i.e., PEG 300, 600, 1500, and 4000 Da for each PEG concentration. The result of morphology observation shows that almost every membrane hasthe asymmetric structure with finger-like pores and thin dense layer. Increasing PEG concentration as well as molecular weight increases pore size and affects on porosity, pore's volume, and physical properties of membrane. The largest pore size, pore volume and porosity of the membrane after sintering were found in the addition of 3.00% PEG 4000 (Da) additive with the value of 110.45 μm, 81.34 ml.g-1 and 120.6%, respectively. In addition, the mechanical properties of membrane were tested using the Vickers micro hardness method with the greatest value found in the addition of 3.00% PEG 1500 (Da) additive with the value of 13.58 Hv and the lowest is 3.00% PEG 4000 (Da) with the value of 1.2 Hv.
PENDAHULUANAir merupakan salah satu kebutuhan pokok bagi manusia. Pemenuhan kebutuhan air bersih sudah menjadi masalah yang sangat umum dan belum diatasi disebagian besar wilayah Negara Indonesia pada umumnya terutama di daerahdaerah pedesaan dan daerah terpencil. Sulitnya pemenuhan kebutuhan air bersih mengakibatkan masalah lain yang lebih kompleks. Salah satu penyebabnya adalah lingkungan ekosistem yang saat ini seringkali terdapat zat berbahaya. Zat berbahaya tersebut di antaranya adalah logam berat yang terdiri dari Pb, Zn, Cd, Ni dan Cu. Logam berat merupakan polutan yang berbahaya dan sangat toksik karena sifatnya yang sukar terurai. Sifat inilah yang menyebabkan logam berat dapat terakumulasi dalam jaringan tubuh makhluk hidup sehingga dapat menyebabkan keracunan secara akut (Darmodo, 1994).Mengingat besarnya dampak yang ditimbulkan oleh logam berat, masalah pencemaran lingkungan dan pengaruhnya terhadap kesehatan mendapat perhatian penting. Logam berat dapat dipisahkan dengan berbagai cara seperti pengendapan kimia, elektrodeposisi, ekstraksi pelarut, ultraflitrasi dan penukar ion (Effendi, 2003). Penggunaan karbon aktif dan resin penukar ion sebagai adsorben polutan telah umum digunakan. Namun kedua bahan tersebut tidak mudah didapatkan dan harganya juga relatif mahal, oleh karena itu para peneliti mulai mencari alternatif material yang dapat digunakan sebagai bahan penyerap yang ramah lingkungan, mudah didapatkan serta ekonomis, salah satunya adalah seperti biosorbent dari karbon aktif (R. Chen, 2015).Karbon aktif merupakan suatu padatan berpori yang mengandung 85-95% karbon, dihasilkan dari bahan-bahan yang mengandung karbon dengan pemanasan pada suhu tinggi. Ketika pemanasan berlangsung, diusahakan tidak terjadi kebocoran udara didalam ruangan pemanasan sehingga bahan yang mengandung karbon tersebut hanya terkarbonisasi dan tidak teroksidasi (T.A. Kurniawan, 2006). Banyak bahan yang digunakan sebagai karbon aktif, salah satunya adalah penggunaan adsorben dari eceng gondok.Menurut Wilbraham (1992), eceng gondok dapat digunakan sebagai adsorben material berbahaya pada lingkungan. Hal ini karena kandungan serat eceng gondok tinggi, yaitu 72,63% selulosa. Kandungan selulosa ini sangat berpotensi untuk digunakan sebagai penyerap bahan tertentu. Selulosa termasuk ke dalam polisakarida pembangun yang paling penting pada tumbuhan. Selulosa merupakan material padatan berpori yang memiliki kemampuan untuk menyerap bahan-bahan lain di sekelilingnya. Sehingga dapat dimanfaatkan sebagai material penyerap bahan berbahaya bagi lingkungan. Selain itu, eceng gondok juga merupakan tanaman yang sangat melimpah, pertumbuhannya sangat banyak di sungai-sungai sehingga dapat mempersempit sungai. Oleh karena itu perlu adanya pemanfaatan eceng gondok.
The LSCF 7328 (La0.7Sr0.3Co0.2Fe0.8O3-δ) asymmetric flat membranes were successfully prepared via a phase-inversion method followed by sintering at 1200 °C. In this study, a variety of poly(ethylene glycol) (PEGs) as the pore-forming agent, with 3 wt% composition and a wide ranges of molecular weight (Mw) (200 to 8000 Da) were used to tests its’ effect to the properties of LSCF membranes. The results show that the PEGs, as additives, were able to modify the pore morphology and mechanical properties of the LSCF 7328 membrane. The morphological evidence from SEM images showed that the LSCF membranes have an asymmetric configuration, comprised of sponge-like and finger-like pores which are integrated with a dense layer. The variation in average pore size is clearly seen, starting from 13.00 to 135.33 μm, following the increase in PEGs molecular weight. The LSCF membranes which were prepared using PEG additive have higher hardness (1.2 – 13.6 Hv) than the membrane with no PEG (0.2 Hv). In contrast, the porosity and pore volume of the membranes decrease with the increase of PEGs molecular weight. The decrease might be due to the formation of various closed macro-voids as the molecular weight of PEGs increases. Furthermore, the thermal expansion coefficient of the membrane with different PEGs molecular weight (ie. 400, 600, 4000 and 6000) Da posses no significant different, i.e. around 16 x 10-6 °C-1, although the membrane showed different morphology and mechanical properties.
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