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Alkali activation of fly ash can a promising alternative of the system to improve adsorption capability of fly ash. In finding the best chemical composition of the activator solution, geopolymer has been synthesized using molar ratios of Na2O/SiO2 0.16, 0.3, and 0.5 (Gr1, Gr3, Gr5). The results indicated that the geopolymer synthesized with a ratio molar of Na2O/SiO2 0.3 (Gr3) improved the adsorption properties of fly ash substantially. Gr3 was characterized by BET, XRD, and FTIR. The batch experiment was conducted at the different duration and initial concentrations. The equilibrium sorption data were fitted for the Langmuir and Freundlich equations. The maximum sorption capacities calculated from Langmuir isotherm was 54 mg g-1 and 47 mg g-1 for Cu (II) and Zn (II) respectively. The kinetic data reveal that the pseudo-second order model was appropriate for a description of the kinetic performance.

Abstract. Fly ash is a particulate material produced from coal combustion power plants with major components are silica, alumina, iron oxide, calcium oxide, magnesium oxide, and carbon which are ideal for metal adsorbents. The potential use of fly ash in the wastewater treatment process is obvious because it can be obtained cheaply in large quatities and it can be used as an adsorbent. However, fly ash still shows lower adsorption capacity unless it is activated. In this study, fly ash activated by NaOH 14 M and KOH 14 M solutions. The batch experiments were carried out to study the sorption of copper ions from aqueous on alkali activated fly ash. The influence of initial concentration and contact time were examined at constant pH and dose of adsorbent. The sorption capacity of copper ions increased with the initial concentration and contact time. The sorption capacities followed the order Na1>Ka1>FA. The adsorption isotherm model exhibited that the Langmuir model is very suitable with copper ions adsorption onto fly ash and alkali activated fly ash. Kinetic study shows that adsorption of copper ions onto FA, Na1, and Ka1 follows the pseudo second-order kinetics.

Peat is superficial deposit or soil with high organic content. The soil is highly compressible and acidic. The organic acidic water in swampy peat soil consists humic acid that is potentially corrosive to concrete and metal structures. Geopolymer is a material using waste from agro-industry such as fly ash (FA) and palm oil fuel ash (POFA) that is activated with alkaline solution. In this research, the acid resistance of geopolymer mortars from fly ash and palm oil fuel ash was measured by change in compressive strength and porosity. The samples were subjected to distilled water and acidic peat water. The OPC mortars showed a considerable decrease in compressive strength after subjected in peat water for up to 180 days. There was a fluctuated trend of geopolymer FA and a high decrease in compressive strength of geopolymer POFA after subjected to the peat water. The porosity of the geopolymer specimens was higher than the control mortars. However, it was observed that the geopolymer FA is more resistant to the acidic peat water than the geopolymer POFA due to stable aluminosilicate bonding.

Abstract. The ability of fly ash to adsorp Cu(II) ions from two different coal combustion systems was studied. Optimum removal was found at pH 5, contact time 30 minutes and 60 minutes for Fly Ash 1 and Fly Ash 2, respectively, and dosage 10 g/l. The difference in adsorption capacity between both fly ashes may be due to their carbon fraction and CaO content. The removal of Cu (II) ions was caused by both adsorption and/or precipitation. Precipitation is enhanced by lowering the carbon fraction and increasing the CaO content. The adsorption isotherm showed that the Langmuir model fitted well to the experimental data of both fly ashes. A thermodynamic study was conducted at three different temperatures: 25 °C, 45 °C, and 60 °C. The adsorption processes were spontaneous and endothermic and were more favorable at higher temperature.

Abu terbang sawit (POFA) merupakan salah satu limbah padat yang dihasilkan dari pembakaran cangkang dan sabut sawit sebagai pembangkit uap untuk konsumsi pabrik sawit. POFA memiliki kandungan silika yang tinggi dan berpotensi digunakan sebagai adsorben. Penghilangan logam pengotor dan pemisahan SiO2 dengan proses ekstraksi merupakan solusi untuk meningkatkan kinerja silika. Proses ektraksi dipengaruhi oleh beberapa faktor diantaranya adalah rasio padat/cair dan waktu pengadukan. Penelitian ini menggunakan rasio padat/cair 1:8, 1:10, 1:12 dan waktu pengadukan 120; 150; 180; dan 210 menit. Hasil penelitian menunjukkan massa endapan silika terbanyak pada rasio 1:12 dan waktu pengadukan 210 menit dengan massa sebanyak 18,35 gram atau 73,4% dari 25 gram POFA dengan kadar silika 47,97% dan luas permukaan silika sebesar 8,18 m2/g. Silika dari setiap variasi diujikan pada air gambut. Efisiensi penyisihan warna, zat organik, dan Fe tertinggi terdapat pada silika hasil ekstraksi dengan rasio padat/cair 1:12 dan waktu pengadukan 210 menit yaitu sebesar 80%, 46%, dan 37%.

Kebutuhan air irigasi secara keseluruhan perlu diketahui karena merupakan salah satu tahap penting yang diperlukan dalam perencanaan dan pengelolaan sistem irigasi. Berdasarkan hal tersebut, maksud penelitian ini adalah untuk menganalisis kebutuhan air irigasi dengan tujuan mendapatkan prediksi nilai kebutuhan air irigasi maksimum dan minimum pada daerah studi dalam hal ini Daerah Irigasi DAS Batang Arau Kota Padang Provinsi Sumatera Barat. Luas daerah irigasinya seluas 1.425 Ha. Sumber air irigasinya berasal dari Sungai Batang Arau. Faktor-faktor untuk menentukan kebutuhan air irigasi antara lain penyiapan lahan, penggunaan konsumtif, perkolasi dan rembesan, pergantian lapisan air dan curah hujan efektif. Perhitungan dilakukan dengan cara konsep KP-01 dimulai dari periode kedua November menggunakan pola tanam padi-padi-bera. Perhitungan manual (konsep KP-01) kebutuhan air maksimun didapat sebesar 2,14 m3/dt terjadi pada periode kedua Desember dan kebutuhan minimum didapat sebesar 0,59 m3/dt terjadi pada periode pertama bulan Maret.