Key methods and innovations in purification of 4N8 grade high-purity quartz

4N8 grade high-purity quartz (HPQ, 99.998%) is an indispensable strategic raw material for cutting-edge industries such as semiconductors, optoelectronics, and photovoltaics. With growing demand for HPQ and increasing constraints on naturally high-quality quartz resources, the development of advanced purification technologies has become essential for the efficient utilization of available quartz resources. This review critically synthesizes recent technological advances toward the production of 4N8 HPQ, with particular emphasis on the removal of micro-inclusions and lattice impurities, which remain the principal bottlenecks to deep purification. Key methods, including emerging separation processes, intensified acid leaching, and advanced chlorination roasting, are systematically evaluated in terms of their removal mechanisms, advantages, and limitations. On this basis, the major challenges and research priorities that underpin future breakthroughs are clarified. This work is expected to offer practical scientific guidance for advancing purification technologies and for strengthening the resilience of this strategic material supply chain globally.