Judul: Literature Review on Composite Zeolites for the Adsorption of Heavy Metal Ions
Abstrak: Perairan merupakan sumber air yang sangat penting bagi kehidupan sehingga berbagai upaya dilakukan untuk membuat perairan terbebas dari ion-ion logam berat yang berbahaya, salah satunya ialah dengan metode adsorpsi. Zeolit merupakan salah satu adsorben yang umum digunakan pada saat ini untuk menghilangkan ion logam berat. Berkembangnya ilmu teknologi memungkinkan adsorben diperoleh melalui penggabungan dua material atau yang disebut komposit. Komposit dibentuk dengan tujuan meningkatkan kemampuan adsorben dalam menghilangkan ion logam berat. Ulasan ini akan memberikan informasi terkait komposit zeolit dengan kitosan, selulosa asetat dan karbon aktif pada beberapa logam berat. Penelitian dilakukan dengan mencari sumber informasi dalam beberapa pangkalan data ilmiah. Masing-masing komposit menunjukkan hasil adsorpsi yang bagus., Water bodies are crucial course of water for life, thus various efforts have been undertaken to rid these water sources of hazardous heavy metal ions, one of which involves adsorption methods. Zeolite is a commonly used adsorbent today to eliminate heavy metals ions. The advancement of science and technology has enabled the creation of composite materials, known as adsorbent for heavy metals ions, with the aim of enhancing their adsorption capacity. This review provides information on zeolite composites with chitosan, cellulose acetate, and activated carbon for several heavy metals. The research was conducted by sourcing information from various scientific databases. The obtained composites from these three materials indicate successful composite formation, as evidenced by the higher adsorption capacity values of the composites compared to their individual component materials.
Keyword: adsorption, activated carbon, chitosan, composite, zeolite

Judul: Literature Review Zeolites and their Applications as Gas Pollutant Adsorbents
Abstrak: SO2, CO2, H2S, dan volatile organic compounds (VOC) merupakan polutan gas yang membahayakan bagi lingkungan dan kesehatan manusia. Oleh karena itu, perlu dilakukan upaya untuk mengurangi kadar polutan gas tersebut dengan proses adsorpsi oleh material zeolit. Zeolit merupakan material yang memiliki bentuk kristal sangat teratur dengan rongga yang saling berhubungan ke segala arah dan menjadikan luas permukaan zeolit sangat besar sehingga sangat baik digunakan sebagai adsorben. Penelitian ini bertujuan meninjau berbagai tulisan mengenai zeolit dan aplikasinya sebagai adsorben polutan gas SO2, CO2, H2S, dan volatile organic compounds (VOC) sehingga didapatkan faktor-faktor yang memengaruhi zeolit dalam mengadsorpsi polutan gas tersebut. Metode peninjauan berupa studi literatur dengan cara mengumpulkan data yang berhubungan dengan topik yang dipilih. Hasil penelusuran memaparkan bahwa zeolit dengan nisbah Si/Al yang rendah (1−5) akan memiliki sifat hidrofilik dan afinitas tinggi terhadap senyawa polar (SO2, H2S), sedangkan jika nisbah Si/Al tinggi akan memiliki sifat hidrofobik dan dapat mengadsorpsi senyawa nonpolar (CO2, benzena). Faktor-faktor yang memengaruhi proses adsorpsi zeolit terhadap polutan gas adalah metode sintesis zeolit, ukuran pori zeolit, ukuran gas yang dijerap, lokasi kation di dalam saluran zeolit, keberadaan ion lain, struktur dari kerangka zeolit, dan kation yang dipertukarkan pada kerangka zeolit., SO2, CO2, H2S, and volatile organic compound (VOC) are gaseous pollutants that are harmful to the environment and human health. Therefore, it is necessary to reduce the gas pollutant levels by adsorption process by zeolite material. Zeolite is a material that has a very regular crystal shape with interconnected cavities in all directions and makes the surface area of the zeolite very large to be used as a potential adsorbent. This study aims to review various articles on zeolites and their applications as adsorbents of gaseous pollutants SO2, CO2, H2S, and volatile organic compounds (VOC) to obtain factors that influence zeolite in the adsorption of these gaseous pollutants. The review method is a literature study by collecting data related to the chosen topic. The study show that zeolites with low Si/Al ratios (1−5) will have hydrophilic properties and high affinity for polar compounds (SO2, H2S), but those with high Si/Al ratios will have hydrophobic properties and can adsorb nonpolar compounds (CO2, benzene). The factors that influence the zeolite adsorption process on gaseous pollutants are the zeolite synthesis method, the zeolite pore size, the adsorbed gas size, the location of the cations in the zeolite channel, the presence of other ions, the structure of the zeolite framework, and the cations exchanged in the zeolite framework.
Keyword: adsorption, adsorption capacity, gas pollutant, zeolite

Judul: Bifurkasi Hopf pada Model Siklus Bisnis Kaldor Kalecki tanpa dan dengan Waktu Tunda
Abstrak: Business cycle model is one of dynamical system models in economic. One of the business cycles model is Kaldor-Kalecki model. Kaldor-Kalecki business cycle model that is written in delayed defferential equations, is a business cycle model that involves gross product and capital stock of a company. In this paper Kaldor-Kalecki business cycle model is analyzed using both nondelay and delay in time of capital stock. By Taylor expansion for the time delayed model, an analysis of stability around the fixed points has been done. Furthermore, by using Hopf bifurcation theorem, it can be shown that there exists periodic orbits and limit cycle. In the nondelayed model, changing the parameter of goods market could lead to the occurrence of Hopf bifurcation and the existence of limit cycle. Similarly, for the delayed model, it has been shown that changing the time delay parameter may result in the occurrence of Hopf bifurcation and limit cycle.
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