Judul: Sintesis Komposit Zeolit/TiO2 dan Aplikasinya sebagai Fotokatalis Pendegradasi Metyhlene Blue
Abstrak: Zeolit disintesis dari limbah kaleng dan foil aluminium sebagai sumber alumina serta kaca air (water glass) sebagai sumber silika yang dikompositkan dengan TiO2 menggunakan metode hidrotermal. Komposit zeolit/TiO2 dengan pemuatan massa TiO2 0%, 2.5%, 5%, 10%, dan 15% dievaluasi kinerjanya dalam fotodegradasi zat warna biru metilena di bawah sinar ultraviolet (UV). Persentase terbaik pemuatan massa TiO2 ke dalam zeolit ialah 2.5% dan 5%. Komposit diamati menggunakan difraksi sinar-X (XRD) dan mikroskop elektron payaran (SEM). Dari data XRD diperoleh pola difraksi yang mirip dengan zeolit tipe NaP1, zeolit tipe X, dan campuran fase TiO2 anatase dan rutil. Pemuatan massa TiO2 tertinggi sebesar 15% yang dikompositkan ke dalam zeolit membentuk zeolit tipe NaP1 yang lebih dominan. Berdasarkan literatur, morfologi TiO2 menyebar pada permukaan zeolit yang mengakibatkan peningkatan pada volume pori. Aktivitas fotodegradasi biru metilena diuji menggunakan spektrofotometer UV-Vis dengan panjang gelombang 665 nm. Hasil fotodegradasi komposit zeolit/TiO2 di bawah lampu UV pada konsentrasi biru metilena sebesar 20 mg/L memperlihatkan 99.43% degradasi.
Keyword: biru metilena, foil aluminium, V fotodegradasi, TiO2, zeolit

Judul: Sintesis Zeoli! X dan Nanokomposit ZeolitJTi02dari Kaolin serta Aplikasinya pada Adsorpsi Fotodegradasi Biru Metilena
Abstrak: Kaolin is rarely used as an adsorbent due to its low adsorption capacity. Therefore, kaolin was converted into zeolite and nanocomposite zeolitefri02. The products were then analyzed using x-ray diffraction and scanning electron microscope. The synthesized zeolite and nanocomposite were identified as zeolite A and zeolite X. The maximum adsorption capacity (Q) of zeolite and nanocomposite occured at the concentration of methylene blue at 300 mgIL with Q value of 17 mglg and 21 mg/g. The zeolite prepared using NaOH 2.5 I and aged at 24 hours had the highest Q value of 17 mg/g. The test results of their photodegradation properties indicate that the nanocomposite can degrade methylene blue at concentration 12.5 mg/L with percent degradation of 85.19%. The adsorption-photodegradation process of methylene blue was showed by the color of filtrate and precipitate the studied objects which were more pale than the color of control after UV irradiation at wavelength of 365 nm in 6 hours.
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Judul: Modelling National Area Harvested of Paddy Using GARCH Methods (Generalized Autoregressive Conditional Heteroscedastic) Model.
Abstrak: Time series data of national area harvested of paddy has high volatility and non homogeneous variance. A time series data with non homogeneous variance at time is called time series data with conditional heteroscedasticity. Time series analysis methods that can be used to overcome heteroskedasticity are GARCH models. However, the data of area harvested of paddy contained in the possibility of asymmetric volatility. To overcome the influence of asymmetry, some asymmetry GARCH models can be used, such as: exponential asymmetric GARCH model (EGARCH), quadratic asymmetric GARCH model (QGARCH), T-GARCH model, and non-linear asymmetry GARCH model (NAGARCH). This study aims to model the national area harvested of paddy by incorporating elements of varians heterogeneity and the influence of asymmetry on its data using five types of symmetry, asymmetry, and non-linear GARCH models, and find the best models of those five types of GARCH models. Model for national area harvested of paddy are ARIMA(2,0,0)(1,1,0)12 ‒ GARCH(1,2) and ARIMA(2,0,0)(1,1,0)12 ‒ QGARCH(1,2). Based on the mean absolute percentage error (MAPE) value to twenty two periods ahead, ARIMA(2,0,0)(1,1,0)12 ‒ QGARCH(1,2) better than ARIMA(2,0,0)(1,1,0)12 ‒ GARCH(1,2) but MAPE values for both models is quite high because there is some predicted value deviates quite far from the actual value. However, the value of MAPE to twelve periods ahead is low, 16.88% for ARIMA(2,0,0)(1,1,0)12 ‒ QGARCH(1,2). Furthermore, based on the value of mean absolute deviation (MAD) and mean square error (MSE), ARIMA(2,0,0)(1,1,0)12 ‒ QGARCH(1,2) also seems to be the better model than ARIMA(2,0,0)(1,1,0)12 ‒ GARCH(1,2). Thus, it can be concluded that the quadratic GARCH model is a fit model of national area harvested of paddy with a fairly good prediction results.
Keyword: time series data, area harvested, GARCH, asymmetric