Integrated Utilization Strategies for Red Mud: Iron Extraction, Sintered Brick Production, and Non-Calcined Cementitious Binder Development for Environmental Sustainability

Red mud (RM), a highly alkaline waste from alumina production, poses severe environmental threats due to massive stockpiling (>350 million tons in China) and groundwater contamination. This study evaluates three scalable strategies to repurpose RM: iron recovery via magnetic separation, sintered brick production using RM–fly ash–granulated blast furnace slag (6:1:3 ratio), and non-calcined cementitious binders combining RM and phosphogypsum (PG). Industrial-scale iron extraction achieved 23.85% recovery of iron concentrate (58% Fe2O3 grade) and consumed 3.6 million tons/year of RM, generating CNY 31 million annual profit. Sintered bricks exhibited 10–15 MPa compressive strength, meeting ASTM C62-23 standard while reducing material costs by 30%. The RM–PG binder achieved 40 MPa compressive strength at 28 days without cement or calcination, leveraging RM’s alkalinity (21.95% Na2O) and PG’s sulfate activation. Collectively, these approaches reduced landfill reliance by 50% and CO2 emissions by 35%–40% compared to conventional practices. The results demonstrate RM’s potential as a secondary resource, offering economically viable and environmentally sustainable pathways for the alumina industry.