Leachate from landfill of municipal solid waste: characterization and determination of thermodynamic properties

Landfill leachate is an aqueous matrix generated by the percolation of rainwater into the body of a landfill and must be considered as a waste due to its content of natural and xenobiotic organic matter and heavy metals. Dissolved organic matter (DOM), which originate from a series of biological and chemical processes, is an important component of leachate because can act against dissolved metals through complexation reactions1. The thermodynamic properties of the leachates are bound to the acid-base properties of the DOM and to the sequestering ability towards metals. The purpose of my research is to study the leachate of municipal solid waste landfills by the characterization of their chemical-physical and thermodynamic properties and evaluate their possible use, in the perspective of the circular economy, as a metal sequestering agent. For this purposed, 5 leachates/waters contaminated by leachate were collected, according to the guidelines of Legislative Decree 152/2006, from a landfill of municipal solid waste in two different periods of the year (November and June). In a first time, analyses were carried out for the determination of the chemical-physical parameters according to Table 2 groundwater of the of Legislative Decree 152/20062. The acid-base properties of the leachate were determined by potentiometric titrations in absence of ionic medium and in NaCl(aq), at I = 0.15 mol dm-3, and T = 298.15K, processing the experimental data with the use of the Poliprotic Like model3, already tested on many classes of high molecular weight polyelectrolytes. Information on the main composition of the leachates were obtained by means of ATR-IR and SEM EDX investigations on the dry residues obtained at T = 383.15K and at 923.15K after calcination. The complexes formation of leachates towards Cd2+, Zn2+ and Cu2+ has been studied in NaCl(aq) at I = 0.15 mol dm-3 and T = 298.15K, by using the ISE-[H+] potentiometry and voltammetry. The sequestering ability of leachates towards the metals ions was quantified at different pH values by means of the pL0.5 parameter4, proving that each leachate behave differently and still possesses the ability to complex metals. References [1] S. Cataldo, G. Lando, D. Milea, S. Orecchio, A. Pettignano and S. Sammartano, New J. Chem 2018, 42, 7640 - 7648. [2] Decreto Legislativo 3 aprile 2006 n. 152 e s.m. (Testo Unico Ambientale) G.U. n. 88 del 14.05.2006 (Supp. Ordinario n. 96). [3] F. Crea, C. De Stefano, G. Manfredi and S. Sammartano, J. Mol. Liq. 2010, 151, 138 - 14 [4] F. Crea, C. De Stefano, C. Foti, D. Milea and S. Sammartano, Curr. Med. Chem. 2014, 21, 3819 – 3836