Removal and Adsorption Mechanisms of Phosphorus, Cd and Pb from Wastewater Conferred by Landfill Leachate Sludge-Derived Biochar

Abstract

There is a high treatment cost and secondary pollution to the environment due to the high organic content and complex composition in landfill leachate sludge in refuse incineration power plants. Landfill leachate sludge-derived biochar (LLSDB) was prepared via pyrolysis in order to realize its resource utilization and remove pollutants from wastewater. The study focused on the removal of nutrients phosphorus and heavy metals (Cd(II) and Pb(II)) from wastewater through the adsorption process using LLSDB. The investigation also looked into the kinetics and thermodynamics of the adsorption process. It was found that the Freundlich–Temkin–Langmuir model was the best model for describing the initial concentration of total phosphorus, (TP) 0–1.0, 1.0–20, and 20–120 mg/L, respectively, while the Freundlich–Langmuir model was the best model for Cd(II) 100–500 mg/L, Pb(II) 500–5000 mg/L, respectively. Additionally, while the exothermic entropy reduction process for TP (˂1.0 mg/L) was spontaneous, the endothermic entropy increment processes for TP (≥1.0 mg/L), Pb(II) and Cd(II) in wastewater increased with the adsorption temperature. It was inferred for the adsorption mechanism of LLSDB that the adsorption of low concentrations of TP, Cd(II) and Pb(II) from wastewater was mainly physical adsorption, following a linear distribution, while that of high concentrations was mainly chemical adsorption because of a series of chemical reactions; TP, Cd(II) and Pb(II) from wastewater were nicely adsorbed and removed by LLSDB600, which was an incredibly superior strategy for controlling waste with waste.