Metaphosphate-quartz-assisted volatilization roasting: An innovative approach for streamlined production of high-purity MoO3 from low-grade molybdenite concentrates with enhanced molybdenum recovery

Existing methods for producing pure MoO 3 from low-grade molybdenite concentrates suffers from complex unit operations, suboptimal metal recovery, excessive reagent/energy consumption, and substantial wastewater generation. This work presents a novel metaphosphate-quartz-assisted volatilization roasting process for the direct preparation of pure MoO 3 from pelletized low-grade molybdenite concentrates. Single-factor experiments demonstrated that the addition of Al(PO 3 ) 3 and quartz significantly increased molybdenum recovery (by over 25 %) while maintaining pellet structural integrity during roasting. The optimal result—97.1 % molybdenum volatilization efficiency—was achieved under the following conditions: a mass ratio of ore: Al(PO 3 ) 3 : quartz = 1: 0.2: 0.2, and temperature-programmed oxidative roasting from 900 °C to 1050 °C for 65 min. Additionally, the crystallized MoO 3 volatile exhibited a high purity of 99.9 % and was further upgraded to 99.99 % purity through a simple water washing. The intensification of molybdenum separation was attributed to two primary mechanisms: (i) Al(PO 3 ) 3 triggered decomposition reactions of molybdates, releasing volatile MoO 3 ; (ii) quartz expansion and interconnected pyrophosphate/phosphate networks maintained a mechanically robust yet porous structure that enabled efficient MoO 3 transfer while reducing vapor contamination caused by dust. In general, the new approach can overcome the negative effects derived from impurities, and offers significant advantages, including much fewer procedures, lower reagent consumption, zero wastewater discharge, and high molybdenum recovery.