This study aims at the low settling efficiency of acid mine drainage(AMD)in an abandoned coal mine in Yichang City.Magnetic nanoparticles(MNPs)were successfully synthesized by solvothermal method,and the mechanism of the combination of MNPs and anionic polyacrylamide(APAM)flocculant on the enhancement of AMD sludge settling performance was systematically studied.The experimental results showed that under the optimal dosage of MNPs and APAM(0.2 g/L and 1 g/L respectively),the sedimentation time of sludge was significantly shortened by APAM,and the sedimentation rate was increased from 1.6 cm/min to 2.5 cm/min by 56.3％,which effectively improved the treatment efficiency.At the same time,the synergistic effect of MNPs further enhanced the sludge compression and dewatering ca-pacity,and the critical volume ratio(Vf/Vm)cp was reduced from 0.27 to 0.19,effectively reducing the treatment cost.Observations through an optical microscope show that,the distribution of MNPs in the flocs enhanced the interaction be-tween particles and promoted the efficient sedimentation and volume compression.The effluent quality after the combined treatment of MNPs and APAM was significantly improved,and all the indicators were close to or reached the relevant na-tional emission standards,reflecting the effectiveness of this technology in environmental remediation.In addition,the magnetic floc regeneration experiment showed that the recovery rate of MNPs was nearly 90％,and its sedimentation effi-ciency remained stable after multiple cycles,which verified the economy and sustainability of the technology.
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