Bergamot Pastazzo as Suitable Platform for Cd2+ Removal and Sensing in Multicomponent Aqueous Solutions

In the last years, citrus waste was used as suitable platform for the design and development of multifunctional nanomaterials (MNMs), able to efficiently and selectively interact with organic (pesticides, dyes, drugs, POPs) and inorganic (metals, anions) contaminants in natural fluids, employing sorption mechanisms [1, 2]. This contribution is focused on the preliminary results obtained using new biobased materials for Cd2+ sequestration from multicomponent solutions simulating the experimental conditions of natural fluids (study scheme in figure). A sample of bergamot pastazzo (peels, pulp, seeds) from the Femminello and Fantastico cultivars, representative of the November 2021-January 2022 harvest season variability, was provided by the Capua 1880 company (Reggio Calabria, Italy). The supplied waste was mechanically ground and divided in two aliquots. A first fraction (P1, raw pastazzo) was dried at t = 60°C for 72 hours and pre-treated with various chemicals, such as NaOH, HNO3, H2O2, H2O, 2-propanol at different temperatures, to check for a possible enhancement of the pastazzo metal sorption capacity [3-5]. A second aliquot (P2) was lyophilized, thermally pre-treated in an autoclave at t = 180°C for 6 hours and purified in dialysis bags, to obtain carbon quantum dots (CQDs) [6]. P1 and P2 fractions were characterized by FT-IR ATR spectroscopy to evaluate surface functional groups. Potentiometric experiments were carried out at t = 25°C, I = 0.10 mol L-1 in NaNO3(aq) to investigate their acid-base properties and complexing ability towards Cd2+. The P1 pre-treated samples sorption capacity was studied by performing kinetics and batch experiments, in which the metal concentration in solution was determined by DP-ASV. The experimental data were analysed by various isotherm models [7]. The mentioned analytical technique is currently employed to investigate the metal desorption from pastazzo, to check for the material stability and reusability after Cd2+ recovery. The investigations on CQDs behaviour in aqueous solutions and the assessment of their metal sorption capacity, for possible applications as sensors for metal cations, are still ongoing by means of various analytical techniques. References [1] N. Mahato, K. Sharma, M. Sinha E. R. Baral, R. Koteswararao, A. Dhyani, M. H. Cho, S., Cho (2020) J. Adv. Res., 23. 61–82. [2] T. Chatzimitakos, A. Kasouni, L. Sygellou, A. Avgeropoulos, A. Troganis, C. Stalikas, Talanta, 175 (2017) 305–312. [3] U. Suryavanshi, S.R. Shukla (2010) Ind. Eng. Chem. Res. 49, 11682–11688. [4] S. Schiewer, S.B. Patil (2008) Bioresour. Technol., 99, 1896–1903. [5] M. Russo, A. Arigò, M.L. Calabrò, S. Farnetti, L. Mondello, P. Dugo (2016) J. Funct. Foods, 20, 10–19. [6] Z. Wang, Y. Xie, Z. Lei, Y. Lu, G. Wei, S. Liu, C. Xu, Z. Zhang, X. Wang, L. Rao, J. Chen (2019) Anal. Chem., 91, 15, 9690-9697. [7] S. Schiewer, S. B. Pati (2008) J. Hazard. Mat., 157, 8–17.