摘要或動機

In order to recycle disposable diapers, we investigated the conditions where sodium sesquicarbonate (Chemical formula Na2CO3・ NaHCO3・ 2H2O hereinafter called sesqui) precipitates selectively from sodium carbonate and the conditions for high yield. For the selective precipitation of sesqui, we defined the time required for the reaction solution to pass through the sesqui precipitation area in the Na2CO3-NaHCO3-H2O phase diagram (45°C) as Δ t. As a result, we revealed that Δt is involved in the selective precipitation of sesqui, and that we can synthesize sesqui without the expensive addition of L-Arginine as used in a previous research. Also, we proposed the “Stay method”, in which the supply of CO2 is stopped for 30 minutes to the lengthen the Δ t, and found that we could synthesize sesqui selectively even under conditions in which sodium bicarbonate is likely to be precipitated as well. Regarding the high yield of sesqui, the yield was greatly improved by the common ion effect of Na by adding NaOH to the reaction solution, sesqui synthesis by repeated reactions with CO2, and sesqui recovery by adding the anti-solvent ethanol, reaching a sesqui conversion rate of 95%. This means 109 g of sesqui can be synthesized from 100 g of Na2CO3. Moreover, we confirmed that these synthesized samples have almost the same detergency as commercial sesqui. We did a test calculation to reveal the usefulness of this research. First, if diaper recycling technology is put into practical use and all used diaper waste in Saijo City can be recycled, a reduction of 534 t/year of used diaper waste can be expected. This corresponds to a 2.3% reduction in Saijo City's waste output. From the ash that would ultimately remain after being recycled, we expect up to 35.3 t/year of synthesized sesqui using our experimental method. In addition, a CO2 reduction of 8.2 t/year is possible in the process, which is about equivalent to the volume of one gymnasium.