From speciation study to removal of Pb2+ from natural waters by a carnosine-based polyacrylamide/azlactone copolymer. (1st June 2023)

• Record Type: Journal Article
• Authors: Abate, Chiara; Scala, Angela; Giuffrè, Ottavia; Piperno, Anna; Pistone, Alessandro; Foti, Claudia
• Is Part Of: Journal of environmental management. Volume 335(2023)
• Publication Date: 2023-06-01
• Subjects: Carnosine -- Pb2+ -- Azlactone chemistry -- Speciation -- Removal; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2023.117572
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: A deep speciation study on L-carnosine (CAR) and Pb 2+ system was performed in aqueous solution with the aim to assess its potential use as a sequestering agent of metal cation. To determine the best conditions for Pb 2+ complexation, potentiometric measurements were carried out over a wide range of ionic strength (0.15 ≤ I/≤ 1 mol/L) and temperature (15 ≤ T/°C ≤ 37), and thermodynamic interaction parameters (logβ, Δ H, Δ G and T Δ S ) were determined. The speciation studies allowed us to simulate sequestration ability of CAR toward Pb 2+ under different conditions of pH, ionic strength and temperature and to establish a priori the conditions for the best removal performance, i.e., pH > 7 and I = 001 mol/L. This preliminary investigation was very useful in optimizing removal procedures and limiting subsequent experimental measurements for adsorption tests. Therefore, to exploit the binding ability of CAR for Pb 2+ removal from aqueous solutions, CAR was covalently grafted on an azlactone-activated beaded-polyacrylamide resin (AZ) using an efficient click coupling reaction (78.3% of coupling efficiency). The carnosine-based resin (AZCAR) was analyzed by ThermoGravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Differential Thermal Analysis (DTA). Morphology, surface area and pore size distribution were studied through a combination of Scanning Electron Microscope (SEM) and adsorption/desorption of N2 analyses according to the Brunauer-Emmett-Teller (BET) and Barret-Johner-Halenda (BJH) approaches. The adsorption capacity of AZCAR toward Pb 2+ was investigated under conditions simulating the ionic strength and pH of different natural waters. The time needed to reach equilibrium in the adsorption process was 24 h, and the best performance was obtained at pH > 7, typical of most natural waters, with removal efficiency ranging from 90.8% (at I = 0.7 mol/L) to 99.0 (at I = 0.001 mol/L). Graphical abstract: Image 1 Highligth: A predictive approach for adsorption study was proposed. Sequestering ability of carnosine was simulated on the basis of speciation study. Best condition for removal was predicted to reduce experimental adsorption tests. Carnosine was linked to poliacrylamide/azlactone copolymer for adsorption purposes. Removal efficiency of 99% was obtained for Pb 2+ removal from natural waters.