Abstract-Starch fatty acid esters, a biodegradable and a renewable thermoplastics materials, are commonly synthesized in organic solvents that have high environmental impact. This manuscript describes an exploratory study on the synthesis of starch esters using various fatty acid methyl esters (FAME) such as methyl myristate, methyl laurate, methyl oleate and methyl palmitate in densified carbon dioxide as a green solvent. A series of experiments were conducted in order to investigate the influence of temperature (100 °C, 110 °C , 120 °C), pressure (100 bar, 120 bar, 150 bar) and type of methyl esters on reactivity and the characteristics of the products. Within the experimental range, the highest DS value (0.45) is achieved at pressure of 100 bar, temperature of 120 o C, with methyl palmitate as the reagent. In addition, the introduction of fatty acid chains into the starch backbone significantly altered thermal properties of the native sago starch.Index Terms-Transesterification, sago starch, fatty acid methyl ester, densified CO 2 .
Groundwater remediation is one of the solutions to restore the contaminated groundwater. This study was conducted to determine the effect of hydraulic conductivity and dynamic dispersivity on the groundwater remediation effectiveness. As a case study, in 2020, in an area located in Balikpapan, groundwater remediation will be carried out by injecting water containing NaOH through five wells and pumping it back through five wells to form a cycle. The method used is a numerical simulation consisting of groundwater flow simulation, mass transport, and sensitivity analysis. The results show that it takes 124 to 300 days for the injected NaOH to arrive at the pumping wells. The sensitivity analysis results show that when the hydraulic conductivity value is ten times greater, the time required is reduced to 84 to 172 days. Meanwhile, when the dynamic dispersivity is twice larger, the time required is reduced to 75 to 189 days. These results indicate that the groundwater remediation method will be effective for aquifers with high hydraulic conductivity and dynamic dispersivity values. For the study area, the groundwater remediation is suggested to be carried out by increasing the number of injection and pumping wells with a relatively close distance, i.e., around 10 meters, so that NaOH arrives at the pumping wells more quickly.Keywords: groundwater, remediation, hydraulic conductivity, dynamic dispersivity, numerical simulation
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