Judul: Optimisasi Adsorpsi Ion Pb(II) Menggunakan Zeolit Alam Termodifikasi Ditizon
Abstrak: Lead (Pb) is one of heavy metals pollutants in the environment. Adsorption appears to be the most widely used for removal of the heavy metals. The aim of this research is to improve the performance of zeolite by modification using chelating agent diphenyltiocarbazone (dithizone) to remove Pb(II) from aqueous solution. The effect of various variables, such as, pH, amount of adsorbent, concentration of Pb, and contact time was investigated using batch process. The best mass of adsorbent for modified zeolite was 0.2 g. The best conditions for modified zeolite was obtained at pH 6, concentration of Pb(II) 300 ppm, and contact time 60 minutes. Meanwhile, the best performance of the unmodified zeolite was at pH 4, concentration of Pb 250 ppm, and contact time 60 minutes. The modified zeolite showed higher adsorption capacity than that of the unmodified material. The results revealed that the adsorption behavior of Pb(II) on the both adsorbent fitted well with the Langmuir model. In addition, the mean adsorption energy from the Dubinin-Radushkevich isotherm indicated that the adsorption process was physisorption.
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Judul: Optimasi Zeolit Alam TermodifikasiFe(OH)3 sebagai Penukar Anion
Abstrak: Activation and modification with Fe(OH)3 can increase the ability of zeolite as anion exchanger. Activation were carried out with HCl concentration of 2, 4, 6, and 8 M with variation of agitation time of 60, 90, and 120 minutes. Optimum condition was determined from the highest anion exchange capacity (AEC), that was 4 M of HCl and contact time of 90 minutes with AEC value of 15.71 meq/100 g. Optimum condition of zeolite modification with Fe(OH)3 was 1.5 g of zeolite weight, 0.1 M of Fe(OH)3 concentration, 120 minutes of contact time, and 24 hours of aging time. The AEC and cation exchange capacity (CEC) obtained in this optimum condition were 21.82 and 100.80 meq/100 g, respectively. Adsorption of Fe(OH)3 into activated zeolite surface data was fitted to Langmuir adsorption isoterm. Phenol was used for batch adsorption studies of optimum Fe(OH)3modified zeolite. The sorption efficiency (%) and sorption capacity of this zeolite were increased linearly with phenol concentration. The amount were 3.69% and 2.01 mg/g, respectively at 80 ppm of phenol. Increment in AEC value as well as still high CEC value in Fe(OH)3-modified zeolite is potencial to be utilized as adsorbent or ion exchanger for waste with negative or positive charge or combination of both.
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Judul: Closed Knight’s Tour pada Papan Catur Berbentuk Persegi Panjang dengan Ukuran Maksimal 8 × 8
Abstrak: Closed Knight’s Tour merupakan langkah kuda yang mengunjungi setiap kotak pada papan catur tepat satu kali dengan langkah kuda berawal dan berakhir pada kotak yang sama. Graf yang terbentuk dari closed knight’s tour dinotasikan sebagai graf G(m,n), dengan m adalah banyaknya baris dan n adalah banyaknya kolom. Graf tersebut memuat Hamiltonian cycle. Sebuah graf terhubung G adalah graf bipartite jika dan hanya jika graf tersebut tidak memiliki cycle dengan panjang ganjil. Papan catur yang memenuhi syarat cukup untuk memiliki closed knight’s tour adalah papan catur berukuran 5 × 6, 5 × 8, 6 × 6, 6 × 7, 6 × 8, 7 × 8, dan 8 × 8.
Keyword: bipartite, closed knight’s tour, hamiltonian cycle, knight’s tour, teori graf