Evaluation of combined thermo-chemical processes for the treatment of landfill leachate using virgin and recovered FeCl3 coagulants

• Published in: Journal of environmental management 2023-12, Vol.347, p.118973-118973, Article 118973
• Main Authors: Pashaki, Saeed Ghanbari Azad, Khojastehpour, Mehdi, Ebrahimi-Nik, Mohammadali, Tedesco, Silvia
• Format: Article
• Language: English
• Subjects: Acid leaching; Coagulant recovery; Coagulation-flocculation; Iron chloride; Sludge from treated landfill leachate
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2023.118973

Sludge resulting from treatment of municipal waste landfill leachate contains suitable cationic substances such as Fe-based recovered coagulants which, if not recovered, can cause environmental problems. The present study aimed to maximise coagulant recoverability and investigate its potential reuse for the treatment of municipal waste landfill leachate. The study focused on establishing (i) the effect of mineral acids on leaching of Fe, (ii) the % of maximum recovery of Fe coagulant, (iii) the impact of ultrasound on recovery, and (iv) effectiveness of recovered coagulant when reused in coagulation-flocculation treatment of landfill leachate. Sulfuric acid outran hydrochloric acid in performance, with the acid leaching process leading to the recovery of 70.12% of Fe (acid concentration = 3.80 M, solid-to-liquid ratio = 8%, and heating time = 5 h). Subsequently, a developed acid leaching process was tested, which results showed that the highest rate of Fe recovery occurred without ultrasound treatment, meaning the use of it could reduce the recovery rate due to the increase in the iron (III) oxide-hydroxide [Fe(OH)3] sedimentation. Comparative experiments were undertaken with the recovered and virgin coagulants. These revealed that Fe-based recovered coagulant led to the 60.21% and 91.40% removal of COD and total suspended solid respectively, while the values of the COD and total suspended solid removal with the virgin FeCl3 were 7.66% and 6.42% lower than that of Fe under optimal conditions (dosage = 9.38 g/L, pH = 8.94, settling time = 52.9 min). The present study established that Fe recovered could be exploited as an eco-friendly coagulant to replace FeCl3 in the landfill leachate treatment. [Display omitted] •Recovered Fe is more effective than virgin FeCl3 in the treatment of leachate.•Sulfuric acid has a higher efficiency than hydrochloric acid in Fe recovery.•The acid leaching process results in a recovery of 70.12% Fe.•Ultrasound duration reduces the Fe recovery rate in acid leaching.•FESEM of leachate sludge had irregular and uneven surfaces (strongly accumulated).