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All Journal Reaktor Jurnal Presipitasi : Media Komunikasi dan Pengembangan Teknik Lingkungan
Wahyono, Yoyon
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Agriculture, Biological Sciences & Forestry Chemical Engineering, Chemistry & Bioengineering Control & Systems Engineering Earth & Planetary Sciences Energy Materials Science & Nanotechnology

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The Dynamics Impact of Urban Area on the River Health in Surakarta City Firdausi, Eyda; Matin, Hashfi Hawali Abdul; Budiyono, Budiyono; Wahyono, Yoyon; Othman, Nur Hidayati
Jurnal Presipitasi : Media Komunikasi dan Pengembangan Teknik Lingkungan Vol 22, No 1 (2025): March 2025
Publisher : Universitas Diponegoro

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/presipitasi.v22i1.209-220

Abstract

Surakarta City is traversed by the Bengawan Solo River Sub-Basin which includes Kali Pepe River, Gajah Putih River, Kali Anyar River, Jenes River, and Premulung River. This condition results in the main burden of river water pollution coming from anthropogenic activities, both domestic and industrial. This study aims to examine the influence of urban area dynamics on river health with a case study of Surakarta City. This study used qualitative descriptive method. Data collection was carried out through observation techniques, and depth interviews. The results showed that there are three factors that affect river health, namely population increase, industrial and domestic activities, and public perception and participation. Surakarta City is one of the areas that contributes to river pollution from moderate to severe levels. However, there have been many efforts to evaluate river health by the local government, namely by normalizing riverbanks, controlling waste pollution, and other river management programs. 
Incorporating silica synthesized from rice husk ash into a calcium oxide catalyst for biodiesel production Alhanif, Misbahudin; Mustafa, Mustafa; Kumoro, Andri Cahyo; Wahyono, Yoyon; Zaim, Hanif Fawwaz; Zahra, Nurul Afifah
Reaktor 2025: Just Accepted and Article in Press
Publisher : Department of Chemical Engineering, Faculty of Engineering, Universitas Diponegoro

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/reaktor.0.0.%p

Abstract

Biodiesel represents a promising renewable energy alternative to either substitute or be blended with conventional diesel, offering advantages such as a high cetane number, reduced sulfur (SOx) and CO₂ emissions, and greater environmental sustainability. The application of calcium oxide (CaO) as a basic catalyst in biodiesel production has been extensively reported. However, its catalytic performance is limited by its sensitivity to moisture, which can negatively affect the reaction rate. In addition, some of the Ca2+ ions in the catalyst can dissolve in the mixture of biodiesel and glycerol, causing product contamination. This study aims to combine a CaO catalyst from marble powder with sulfonated silica (SiO2) from rice husk ash (RHA) to enhance the distribution of catalyst particles, reduce crystallinity, and increase the surface area of the catalyst. This study was conducted through chemical and thermal activation of SiO2 from RHA, sulfonation of SiO2, thermal activation of CaO from marble powder waste, and impregnation of CaO/SiO2 catalyst with variations in CaO/SiO2 composition (25%:75%, 50%:50%, 75%:25%). The results showed that the purity of SiO2 and CaO obtained through chemical and thermal activation was 93.67% and 99.13%, respectively. The sulfonation process on SiO2 successfully added –SO3 groups at 36.5%, which supported the formation of acid sites on the catalyst. Characterization showed that the surface morphology was composed of particles measuring 2–8 µm with a dominant amorphous structure. The addition of SiO2 gave rise to new crystal peaks but decreased the crystal intensity, especially at the 50%:50% composition. The composition of CaO/SiO2 at 75%:25% showed the best physical properties with a surface area of 22.24 m²/g, a pore volume of 65.29 mm³/g, and a pore diameter of 11.74 nm, indicating high potential as a bifunctional catalyst for biodiesel esterification–transesterification.
Co-Authors Andri Cahyo Kumoro Budiyono Budiyono Firdausi, Eyda Matin, Hashfi Hawali Abdul Misbahudin Alhanif Mustafa Othman, Nur Hidayati Zahra, Nurul Afifah Zaim, Hanif Fawwaz