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Tjokorde Walmiki Samadhi
Faculty of Industrial Technology, Institut Teknologi Bandung, Labtek X Building, Jalan Ganesa 10 Bandung 40132
Aerospace Engineering Automotive Engineering Chemical Engineering, Chemistry & Bioengineering Civil Engineering, Building, Construction & Architecture Electrical & Electronics Engineering

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Role of Deagglomeration in Particle Size and Antibiofilm Activity of ZnO Nanoparticles Synthesized with Averrhoa bilimbi Extract Vita Wonoputri; Tjokorde Walmiki Samadhi; Shafira Khairunnisa; Eka Rahayu
Journal of Engineering and Technological Sciences Vol. 56 No. 6 (2024)
Publisher : Directorate for Research and Innovation, Institut Teknologi Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.eng.technol.sci.2024.56.6.5

Abstract

Averrhoa bilimbi fruit extract was utilized as a reducing and capping agent in the biosynthesis of zinc oxide nanoparticles, with an emphasis on the effects of in-situ deagglomeration on physical properties and antibiofilm activity against Escherichia coli. The study explored various biosynthesis parameters, namely deagglomeration method (physical vs chemical), temperature (30, 60 ℃), and zinc precursor-to-extract volumetric ratio (0.5 and 2). High purity crystalline ZnO nanoparticles were obtained by calcining biosynthesis precipitates at 375  ℃. The resulting particles consisted of the wurtzite ZnO phase, with diameters ranging from 18 to 30 nm. The hydrodynamic mean particle diameters were 1.0 to 3.5 µm, suggesting the formation of soft agglomerates. Physical deagglomeration was more effective at higher temperatures, while chemical deagglomeration was more efficient at lower temperatures, owing to the interaction between the deagglomeration method and biosynthesis temperature. The biosynthesized ZnO nanoparticles exhibited good antibiofilm activity, achieving a 61% reduction in biofilm population at 50 ppm ZnO, which increased to 78% at a dose of 200 ppm. This activity was improved by lower biosynthesis temperature and precursor:extract ratio, likely due to the preservation of bioactive molecules. The results demonstrate the potential of biosynthesized ZnO nanoparticles as antibiofilm agent, offering enhanced effectiveness compared to commercial ZnO nanoparticles
Synthesis of Geopolymer from Ferronickel Aluminosilicate Waste Tjokorde Walmiki Samadhi; Winny Wulandari; Aya Anisa Dwinidasari; Arum Rahmasari
Journal of Engineering and Technological Sciences Vol. 57 No. 4 (2025): Vol. 57 No. 4 (2025): August
Publisher : Directorate for Research and Innovation, Institut Teknologi Bandung

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.5614/j.eng.technol.sci.2025.57.4.1

Abstract

The nickel industry in Indonesia generates massive volumes of ferronickel slag that may harm the environment. This research evaluates the feasibility of utilizing coal fly ash and slag from a ferronickel smelter in Obi Island in Indonesia to synthesize geopolymer, an environmentally friendly cementitious material. Compressive strength of geopolymer mortars was measured as a function of slag particle size (coarse and fine), fly ash mass fraction in the dry aluminosilicate binder precursor blends (0.4 and 0.8), and thermal curing period (24 and 48 hours). Mortar specimens were produced by mixing ash and slag with activator solution and sand. The activator solution contained Na2SiO3 and NaOH at a mass ratio of 2:1. Solid reactants to activator solution mass ratio was 3.33. After heat curing, specimens were held in ambient conditions to an age of 7 days. The compressive strength of the mortars was in the 2.1-24.8 MPa range. Geopolymer mortars were able to comply to Indonesian SNI 15-2049-2004 or US ASTM C1329-05 standards for Portland cement. FTIR and XRD characterizations confirmed the conversion of fly ash and slag into amorphous geopolymers at near ambient temperature. Finer slag particle size increased reactivity, ultimately producing higher compressive strength.
Co-Authors Arum Rahmasari Aya Anisa Dwinidasari Eka Rahayu Shafira Khairunnisa Vita Wonoputri Winny Wulandari