Sustainable Zinc Borate Production Using Borax Plant Wastewater: Process and Impurity Analysis

Industrial zinc borate is commonly produced through a hydrothermal process using boric acid and zinc oxide as raw materials. In this study, zinc borate was synthesized by replacing boric acid with borax ore and fresh water with borax plant wastewater in order to improve resource efficiency and water sustainability within an industrial symbiosis framework. Due to side reactions originating from borax, the reaction medium exhibited high ionic strength, and the synthesis was completed at 90 °C in approximately 5 h, slightly longer than conventional industrial processes. An additional washing step was applied to reduce impurities, resulting in a final impurity level of 2966 mg/kg, comparable to that of commercial zinc borate. The use of borax plant wastewater significantly reduced fresh water consumption. However, the formation of a by-product stream containing approximately 16% Na2SO4 may limit direct industrial applicability. If this sodium sulfate stream is valorized within an industrial symbiosis framework, zinc borate production from borax and wastewater could represent a cost-effective and sustainable alternative to conventional processes.