Abstract: Vanadium-titanium magnetite tailings are characterized by high total phosphorus content but extremely low available
phosphorus content,which severely restricts their ecological remediation efficiency. To enhance the phosphorus bioavailability
in tailings,this study adopted a synergistic approach combining mechanical activation and lowmolecularweight organic
acids (LMWOAs). The tailings were mechanically activated for different durations (0~60 min) using a planetary ball
mill,followed by leaching activation tests with different concentrations (0. 1,0. 2 mol/ L) of oxalic,tartaric,citric,and malic
acids. A pot experiment with alfalfa was then conducted using two variables:the proportion of activated tailings (1∶9) and the
oxalic acid concentration (0. 1 mol/ L). The results showed that mechanical activation significantly altered the physicochemical
properties of the tailings. After 40 min of activation,the particle size was minimized,the specific surface area reached its maximum,
and the particle morphology transformed into a porous flocculent structure. Fouriertransform infrared spectroscopy revealed
the conversion of PO₄^3- and CO₃^2-groups and a decrease in crystallinity. The citratesoluble phosphorus content increased significantly with prolonged activation time,reaching 2. 88 g/ kg after 60 min,which was 4. 2 times that of the original tailings.
LMWOAs further promoted phosphorus activation,showing a synergistic effect with mechanical activation. Under the optimal
synergistic condition (40 min activation),0. 1 mol/ L oxalic acid exhibited the best activation effect,followed by 0. 2 mol/ L
tartaric,citric,and malic acids. The pot experiment confirmed that the combined treatment with proportioned tailings (1∶9) and
0. 1 mol/ L oxalic acid achieved the most significant enhancement in available phosphorus and its effective forms (Ca2-P and
Ca8-P). In conclusion,the coupling of mechanical activation and LMWOAs can significantly improve the phosphorus activity in
vanadium-titanium magnetite tailings,providing a theoretical basis and technical reference for tailings resource utilization and
phytoremediation.