Drying of wet borax pentahydrate by microwave heating

In this study, drying of borax pentahydrate [Na2B4O7·5H2O] (BPH) by microwave energy is investigated. Using 100−700 W and 2450 MHz microwave energy, 5−10% moisture containing BPH placed on a Teflon-lined belt is dried at 60−100 °C selectively, without any loss of water of crystallization. In this process the microwave oven is first set to 70 °C and then wet BPH which is previously heated to 70 °C is placed in it. The sample first heats up to 80−100 °C by the effect of microwave energy, and then its temperature sharply drops, resulting in complete removal of moisture. This process gives way to no decomposition and disintegration of hydrated crystalline molecule and there are no contaminants involved. Therefore, dry borax pentahydrate dried this way retains its original purity and physical form. Since there is no need to heat the drying system and the air and to keep the relative humidity of the air constant, microwave drying is more economical than the conventional process. In addition, a sharp decrease of...