Judul: Adsorption of foron yellow dyes using chitosan and chitosan–taro stem
Abstrak: Pencemaran air akibat limbah zat warna industri tekstil merupakan salah satu masalah besar yang dihadapi saat ini. Penelitian ini bertujuan mengukur pengaruh waktu adsorpsi, konsentrasi adsorbat, dan pH terhadap kapasitas dan efisiensi adsorpsi serta menentukan isoterm adsorpsi dari kedua adsorben. Adsorpsi dilakukan dengan ragam waktu, pH, dan konsentrasi adsorbat menggunakan metode response surface dengan central composite design (CCD). Kondisi yang menghasilkan adsorpsi terbaik adalah konsentrasi adsorbat 18 ppm, waktu 75 menit, dan pH 5. Kapasitas adsorpsi tertinggi pada pengujian larutan tunggal foron yellow untuk kitosan dan kitosan-batang talas berturut-turut sebesar 543 μg/g dan 669 μg/g dengan efisiensi adsorpsi berturut-turut sebesar 61% dan 74%. Aplikasi kitosan dan kitosan-batang talas terhadap limbah industri batik menunjukkan efisiensi adsorpsi berturut-turut sebesar 37% dan 38%. Adsorben kitosan dan kitosan-batang talas diduga mengikuti model isoterm adsorpsi Freundlich., Water pollution caused by dyes textile industry waste is one of the major problems faced today. This study aimed to evaluate the effect of adsorption time, adsorbate concentration, and pH on the adsorption capacity and efficiency as well as determining the adsorption isotherms of the two adsorbents. Adsorption was done at various time, pH, and adsorbate concentration using response surface method with central composite design (CCD). Conditions that produce the best adsorption was at 18 ppm concentration, 75 minut es, and pH of 5. The highest adsorption capacity in testing foron yellow single solution for chitosan and chitosan-taro stem were 543 μg/g and 669 μg/g with adsorption efficiency were 61% and 74%, respectively. Application of chitosan and chitosan-taro stem adsorbents toward batik industrial waste showed adsorption efficiency of 37% and 38%, respectively. Chitosan and chitosan-stem taro adsorbent is suspected to follow Freundlich adsorption isotherm models. Keywords: adsorption, chitosan, chitosan-taro stem, foron yellow, isotherm.
Keyword: adsorpsi, foron yellow, isoterm, kitosan, kitosan-batang talas

Judul: Adsorben Berbasis Limbah Padat Agar-Agar sebagai Penjerap Zat Warna Indigosol dan Zat Warna Limbah Industri Batik
Abstrak: This study aimed to compare adsorption capacityof solid waste of agar and its carbonization results for indygosol dyes and to compare coagulation-flocculation using adsorpstion process to reduce batik industry waste dyes. The waste after treatment by netralization and coagulation-flocculation using alum reduced chemical oxygen demand (COD) and dyes percent by 45 % and 57.78 % at 50 and 150 ppm alum. Solid waste of agar contained 69.68 % crude fiber which indicates high carbon content in the sample. Solid waste of agar after carbonization had adsorption capacity and efficiency of 6.2394 mg/g and 83.38% for indigosol dyes, and could reduce dyes and COD in the batik industrial waste decreased by 59.81% and 22.19%. Solid waste of agar without carbonization resulted adsorption capacity and efficiency of 3.0644 mg/g and 40.87% for indygosol dyes, and could reduced dyes and COD of the waste by 52.78% and 18.13%.
Keyword: solid waste of agar, indigoso, coagulation-flocculation, carbonization, adsorption

Judul: Analysis of Unequal Income Distribution with Cobb-Douglas Production Function
Abstrak: This paper studies the economic growth model by Moav (2002). Moav model shows the existence of unequal income distribution between low-income with high-income community. That kind of unequal income distribution is caused by uneven distribution of income. On this Moav model, there is one area called the threshold. Threshold becomes a benchmark to determining whether a society is categorized into low- or high- income community. The production function used in this paper is the Cobb-Douglas function. The dynamics of this model is described as difference equation of low-income, threshold, and high-income community. Simulation study on the model is carried out using Maple 13 and Mathematica 7.0 software. Overall, from the observed case, high-income community will reach a stable condition earlier, followed by the threshold, and then the low-income community.
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