Antiscaling activity of aspartic acid extracted from sugar beet molasses by optimized microwave-assisted method

Scale deposition on heating surfaces in the sugar industry limits heat transfer. Using green scale inhibitors is a promising way to increase safety and reduce the environmental hazards of the prevalent ones. This study aimed to optimize the extraction of aspartic acid (as an antiscaling agent) from sugar beet molasses using the microwave-assisted extraction (MAE). The MAE was performed by variables of extraction time (5, 12.5, and 20 min), extraction temperature (50, 70, and 90° C), and solvent pH (3, 4.5, and 6) using the Box-Behnken design. Optimal conditions for aspartic acid extraction using the MAE included 13.62 min of extraction time, extraction temperature of 64.07 °C, and pH of 4.98 with the desirability value of 1. Aspartic acid extracted under optimal conditions with various concentrations (10, 25, and 50 mg/L) and temperatures (60, 90, and 120 °C) at pH 8 was applied to the evaporator tube scales of the sugar industry for 6 h. The highest antiscaling efficiency (81.12 ± 1.12%) was related to the treatment performed at 90 °C with a concentration of 50 mg/100 g. Field emission scanning electron microscopy and the Fourier transform infrared spectroscopy showed that by increasing temperature up to 90 °C and increasing concentration up to 50 mg/100 g, the scales change from crystalline and uniform state to porous with fine particles. The energy-dispersive spectroscopy showed that by increasing the temperature to 90 °C and increasing the concentration to 50 mg/100 g, the calcium and silica content in the scales decreases. Graphical abstract