Potash recovery from synthetic potassium rich wastewater and biomethanated distillery effluent using tartaric acid as a recyclable precipitant

Potassium is one to the essential elements for plant and animal life due to its vital nutritional roles. Globally, more than 95% of the potassium chemicals is utilized as fertilizer. Due to shortage of land and vulnerability to climatic conditions, potash production through conventional evaporation process seems difficult in long run. Hence, its recovery from the potassium rich industrial effluents such as biomethanated spent wash (BMSW), can be an attractive option. In the present study, tartaric acid (a recyclable precipitant) was used for potash recovery from potassium rich synthetic wastewater (PWW) and BMSW (potassium concentration = 19.5 g/L and 14.8 g/L, respectively). At an optimum solution pH of 3.5, more than 70% of the total potassium was precipitated out as potassium bitartrate (KHT) from PWW with the stoichiometric tartaric acid dose (1M). Subsequently, the tartaric acid was regenerated by converting KHT into potassium nitrate (KNO3). Around 77% potassium could be converted into KNO3 using Mg(OH)2 and HNO3 with 80% regeneration of tartaric acid. Under similar conditions, ∼70% potassium precipitation with 62% color removal could be achieved from the BMSW stream. Based on the results, it can be suggested that the selective extraction using tartaric acid has high potential for potash recovery from waste streams. A detailed study should focus on the optimization of conditions for recovery of potassium from real effluent and its purity in the residue should be verified. In addition, suitable conditions for regeneration of tartaric acid should also be obtained.