A study of liquid waste adsorption containing strontium was carried out using the adsorption method using silica xerogel adsorbent. Silica xerogel synthesized from coal fly ash using the sol-gel method, produces a specific surface area of 84.8884 m2/g. This study was intended to determine the appropriate kinetics law. Data were obtained by following changes in Sr concentration to the time of adsorption at temperature of 25 ºC and 35 ºC. The data obtained was matched with 5 kinetic models, namely zeroth order kinetics, first order, second order, pseudo first order, and pseudo second order. Based on data analysis by means of linear regression and the number of minimum sum squared of errors, the adsorption kinetics model that is suitable for the adsorption of strontium by silica xerogel is a pseudo second order. The reaction rate constant at 298 K and 308 K were 0.1023 g/mg/min and 0.0716 g/mg/min respectively. The value of the activation energy is negative so the higher the temperature, the lower the adsorption rate. It is indicate that the adsorption is reversible.

SINTESIS SILIKA XEROGEL DARI ABU DAUN BAMBU UNTUK ADSORPSI LIMBAH SIMULASI URANIUM. Telah dilakukan penelitian tentang sintesis silika xerogel dari abu daun bambu dengan metode sol gel menggunakan prekursor natrium silikat untuk adsorpsi limbah simulasi uranium. Abu daun bambu mangandung sekitar 58% silika yang bisa dimanfaatkan sebagai bahan baku pembuatan silika xerogel. Tujuan penelitian ini adalah untuk mengetahui pengaruh pH dan waktu aging serta mengetahui karakter silika xerogel, model isoterm adsorpsi dan termodinamika adsorpsi uranium oleh silika xerogel . Karakterisasi silika xerogel yang dilakukan adalah menentukan gugus fungsi, uji kristalinitas dan luas permukaan. Identifikasi gugus fungsi dan struktur kristal menggunakan FTIR dan XRD. Luas permukaan silika xerogel ditentukan dengan metode metilen biru. Hasil penelitian menunjukan bahwa sintesis silika xerogel terjadi pada pH optimum 7 dengan waktu aging optimum 3 jam. Hasil karakterisasi silika xerogel pada keadaan optimum menunjukkan luas permukaan sebesar 177,2858 m2/g . Spektra Infra Red silika xerogel hasil sintesis mengandung gugus silanol (Si-OH) dan siloksan (Si-OSi) serta data XRD memperlihatkan silika xerogel berstruktur amorf. Hasil percobaan menunjukkan bahwa adsorpsi uranium dengan silika xerogel mengikuti model isoterm Langmuir. Dari hasil evaluasi parameter termodinamika, adsorpsi uranium dengan silika xerogel merupakan adsorpsi kimia dan bersifat endoterm.

Smart hydrogels which can change their swelling behavior and other properties in response to environmental stimuli such as temperature, pH, solvent composition and electric fields, have attracted great interest as chemical sensor material and controlled release system. The pH stimulus responsive hydrogels were synthesized by gamma-irradiation graft copolymerization of chitosan-acrylamide. In this research the influence of deacetylation process on the hydrogels characterization were investigated by measuring grafting efficiency, gel fraction, swelling degree, and crosslink density. Evidence of grafting was confirmed by FTIR spectroscopy. X-ray diffraction showed reduction in the crystallinity of chitosan with different deacetylation process also after the graft copolymerization reaction. The results showed that decreasing acetyl group of chitosan increase the grafting efficiency, gel fraction and swelling degree. While crystallinity decreased. The hydrogels indicated pH-dependent swelling behaviour.

Molds can carry out amylase production, but the production of the enzyme is affected by a carbon catabolite repression system, thus reducing amylase production. This study aimed to increase amylase production in Aspergillus tamarii FNCC 6151 with irradiation by gamma rays. Spore suspensions were irradiated at 100, 200, 300, 400 and 500 Gy and the survival of the spores was determined. The spore suspension irradiated at 400 Gy was diluted and grown on medium plates containing starch as a carbon source and 2% glucose as a repressor. After staining with iodine, colonies showing clear zones around them were purified and grown in liquid media for four days and their alpha-amylase and glucoamylase activities were analyzed. The mutant Mut1 showed a clear zone. This mutant produced 1.127 U/mL of alpha-amylase and 0.011 U/mL of glucoamylase. Meanwhile, the parental strain produced 0.68 U/mL of alpha-amylase and 0.079 U/mL of glucoamylase. The random mutagenesis using gamma-ray into A. tamarii FNCC 6151 increased alpha-amylase and glucoamylase production by 1.8- and 1.4-fold respectively.

PEMBUATAN    KOMPOSIT    POLIMER     SUPERABSORBEN    DENGAN MESIN BERKAS ELEKTRON. Polimer superabsorben adalah suatu polimer yang dapat mengabsorpsi air dan mempunyai daya serap sampai beberapa kali lipat dibandingkan berat polimernya. Polimer superabsorben dapat dimanfaatkan dalam banyak bidang diantaranya pembungkus makanan, teknik konstruksi, industri kimia, pengolahan limbah dan bahan pembuat sensor. Bahan utama polimer superabsorben adalah poliakrilamida. Poliakrilamida mempunyai kekurangan dalam kekuatan fisik dan kestabilan terhadap suhu. Dalam penelitian ini telah dilakukan pembuatan komposit polimer superabsorben menggunakan monomer akrilamida dan zeolit alam. Komposit polimer superabsorben dibuat dengan proses polimerisasi dan grafting akrilamida dengan zeolit alam menggunakan iradiasi mesin berkas elektron. Variabel yang dipelajari adalah dosis radiasi 15; 25; 28; 35; 48 kGy dan perbandingan akrilamida terhadap zeolit 0,5 : 1; 1 : 1;   2:1. Bertambahnya dosis radiasi akan meningkatkan konversi komposit yang dihasilkan dan kapasitas absorpsi polimer superabsorben. Setelah tercapai ikatan polimer yang sempurna, penambahan dosis radiasi akan menurunkan kapasitas absorpsi. Semakin besar perbandingan akrilamida terhadap zeolit akan menaikkan konversi komposit yang dihasilkan dan kapasitas absorpsi.