STUDY OF OBSIDIAN GEOPOLYMERIZATION UTILIZED FOR POTASSIUM SLOW RELEASE IN WATER

• Main Author: RIZQIADI (NIM : 12514043), ALFIN
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/25346
• Institution: Institut Teknologi Bandung

The rapidly-growing world population increases the food supply demand. As available area for agricultural uses are limited, fertilizer is utilized to increase food production. However, high fertilizers use in a long time badly impacts the environment. High solubility of fertilizer causes the fertilizer elements to be improperly absorbed by the fertilizer elements. One of the solutions for this problem is developing a material for slow releasing fertilizer elements. One of the material suitable for this purposeis geopolymer. In this research work, geopolymer is made from obsidian and waterglass mixture. Obsidian rock was obtained from the region of Garut, West Java. <br /> <br /> Series of tests at atmospheric pressure and room temperature have been carried out to study the effect of geopolymerization temperature, briquetting pressure, and geopolymer composition on the potassium dissolution percentage. The obsidian geopolymer is made in various pressure and temperature conditions. The amount of potassium hydrogenphosphate trihydrate placed on the middle of geopolymer was 0.5 gram. The effect of geopolymerization temperature was studied at various temperature of 100, 110, 120, and 130oC. The effect of briquetting pressure was studied at various pressure 0 (hand press), 10, 20, and 30 kg/cm2. Meanwhile, the effect of geopolymer composition was studied at various obsidian mass composition (gram) : waterglass 3.35 M volume (ml) 6:1, 7:1, and 8:1. The percentages of dissolved K as a function of time at various conditions were determined by analysis of Atomic Absorption spectrophotometry (AAS). <br /> <br /> The lowest percentages of dissolved potassium from geopolymerization temperature variation was obtained at 130oC. The lowest percentages of dissolved potassium from geopolymer briquetting pressure variation wass obtained at 30 kg/cm2. The lowest percentages of dissolved potassium from geopolymer composition variation was obtained at 6:1. In this research, the lowest percentages of dissolved potassium was obtained at combined condition of 130oC geopolymerization temperature, 30 kg/cm2 briquetting preassure and 6:1 geopolymer composition. The percentages of dissolved potassium obtained at that condition was 64,53%. FTIR and SEM were used for geopolymer structure analysis.