Valorization of citrus waste for circular economy: A case study on bergamot pomace as sorbent for Cd2+ removal and source of added value compounds

The potential of bergamot pomace for the development of materials able to efficiently remove cadmium(II) from water and for the recovery of bioactive compounds has been explored. To this purpose, raw bergamot waste resulting after industrial essential oil and juice extraction was mechanically ground, desiccated, pretreated with various chemicals (e.g. NaOH, HNO3, H2O2, H2O, 2-propanol) and dried up to constant weight thus affording solid samples that were characterized by ATR FT-IR spectroscopy. The solutions recovered after the pomace pretreatments were investigated by means of HPLC in combination with PDA and MS detectors to assess the residual content of bioactive components, e.g., phenolic and oxygenated heterocyclic compounds (OHCs). Potentiometric studies were performed on suspensions at t = 25 °C, I = 0.10 mol dm−3 in NaNO3(aq) to investigate pomace acid-base properties and binding ability towards Cd2+ ions. Sorption efficiency was investigated by means of kinetic and isotherm batch experiments and resulted to be 92 ± 7 mg g−1. Once loaded, sorbent reusability was tested by performing metal stripping cycles using various desorbents (HCl, HNO3, L-GLDA, S,S-EDDS, EDTA) with an efficiency of ∼ 60% after one cycle. The equilibrium Cd2+ concentration in solution was determined by differential pulse voltammetry and ICP-OES

POSS–Tetraalkylammonium Salts: A New Class of Ionic Liquids

A series of new polyhedral oligomeric silsesquioxane ionic liquids (POSS-ILs) based on the trimethylpropylammonium dielectric constants, which, conversely, display slight differences originating from the nature of the anions. The long alkyl-chain substituents on the POSS core infer on this series of ILs an overall hydrophobic character and solution properties comparable to those of classic cationic surfactants, resulting in an effective extractant capability of polyanions from aqueous solutions. Their solution diffusion properties, as investigated by room-temperature dynamic light scattering, solution conductivity, density, and osmometric measurements, do not provide evidence for the occurrence of any hepta(isooctyl)octasilsesquioxane cation and a variety of anions have been synthesized and characterized. Their thermal behavior has been ascertained by thermogravimetric and differential thermal analyses and differential scanning calorimetry; room temperature conductivity, dielectric constants, and dynamic contact angles have been investigated as well. The obtained data show that the presence of the POSS moiety is responsible not only for their thermal properties, but also for their low room-temperature conductivity and significant self-assembling processes

Thermodynamic and spectroscopic study of the binding of dimethyltin(IV) by citrate at 25°C

Thermodynamic (potentiometric and calorimetric) and spectroscopic (1H NMR, 119Sn M¨ossbauer) studieswere performed in aqueous solution in order to characterize the interaction of dimethyltin(IV) cation with citrate ligand. Six species {(CH3)2Sn(cit)−; [(CH3)2Sn]2(cit)2 2−; (CH3 )2Sn(cit)H0; (CH3)2Sn(cit)OH2−; [(CH3)2Sn]2(cit)OH0; [(CH3)2Sn]2(cit)(OH)2 −} were found. All the species formed in this system are quite stable and formation percentages are fairly high. For example, at pH = 7.5 and C(CH3)2Sn = Ccit = 10 mmol l−1, % for [(CH3)2Sn]2(cit)(OH)2 − and (CH3)2Sn(cit)OH2− species reaches 65%. Overall thermodynamic parameters obtained show that the main contribution to stability is entropic in nature. Thermodynamic parameters were discussed in comparison with a simple tricarboxylate ligand (1,2,3-propanetricarboxylate). Two empirical relationships were derived from thermodynamic formation parameters. Spectroscopic results fully confirm the speciation model defined potentiometrically and showthe mononuclear species to have an eq-(CH3)2Tbp structurewith different arrangements around the metal, while for [(CH3)2Sn]2(cit)(OH)2 − there are two different Sn(IV) environments, namely trans-(CH3)2 octahedral and cis-(CH3)2 Tbp

Very fast CO2 response and hydrophobic properties of novel poly(ionic liquid)s

A series of polymerizable tetraalkylammonium ionic liquids based on [2-(methacryloyloxy)ethyl]dimethylheptyl ammonium cation and bis(trifluoromethylsulfonyl)imide, nonafluoro-1-butanesulfonate, dodecylbenzenesulfonate, heptadecafluorooctanesulfonate, 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadecafluoroundecanoate anions, as well as their corresponding homo- and copolymers, have been synthesized and characterized by means of 1H NMR, TG-DTA, DSC, MALDI-TOF, viscosimetry and XPS investigations. Hydrophobic and CO2 sensing properties of the poly(ionic liquid)s have been explored by dynamic contact angle and quartz crystal microbalance measurements. The CO2 sensing behavior of present polymers is very remarkable as they are featured by extremely rapid and completely reversible response without any memory-effect. Best results, in terms of sensitivity, have been obtained for [2- (methacryloyloxy)ethyl]dimethylheptyl ammonium nonafluoro-1-butanesulfonate-based homopolymer. Tensiometric data show good hydrophobic properties with qadv > 90 for all the polymers under study except the one involving 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11- heptadecafluoroundecanoate anion (qadv ¼ 78.3); receding contact angles, representative of the most hydrophilic portions of the polymers surface, lie in the range 22–54 and can be further improved by choosing the proper long-chained N-alkyl groups

Capacità sequestrante di leganti S-donatori nei confronti di CH3Hg+

L’interesse nei confronti della chimica di coordinazione del mercurio(II) deriva dalla sua tossicità intrinseca. Sebbene tutte le forme di mercurio siano tossiche, gli effetti sull’ambiente e sull’uomo sono in genere legati alle trasformazioni ambientali di Hg inorganico a metilmercurio. L’elevata tossicità del metilmercurio(II) per gli esseri umani deriva dall’affinità del mercurio(II) nei confronti di residui cisteinil solfuri. I tioli a basso peso molecolare costituiscono i vettori per il trasporto e la distribuzione di mercurio nell’organismo umano a causa del fenomeno del "mimetismo molecolare”. Uno studio della chimica in soluzione del metilmercurio(II) in presenza di tali leganti fornisce pertanto informazioni utili circa la natura e l'entità delle interazioni tra di essi. Tali informazioni possono essere utilizzate per valutare metodi di rimozione del metallo da sistemi biologici attraverso l’uso di agenti chelanti (chelation therapy). In questo lavoro viene riportato uno studio delle capacità complessanti di leganti zolfo donatori nei confronti di CH3Hg+. I leganti considerati sono: l’acido 2 mercaptopropanoico (o tiolattico, tla), l’acido 3-mercaptopropanoico (mpa), l’acido 2-mercaptosuccinico (o tiomalico, tma), la penicilammina (pen), la cisteina (cys) e il glutatione (gsh). Lo studio è stato eseguito mediante diverse tecniche strumentali: la potenziometria (ISE-H+) al fine di determinare le costanti di formazione dei complessi per i diversi sistemi CH3Hg+-legante; la calorimetria per determinare le relative entalpie di formazione; la spettroscopia 1H NMR e la spettrometria di massa-elettrospray (ESI-MS) per confermare i modelli di speciazione proposti e per ottenere informazioni strutturali. Gli studi sono stati condotti in NaNO3 a I = 0.1 mol L-1 e a t = 25 °C, in presenza di ioduro quale legante competitivo. Per i sistemi CH3Hg+ -tma, -pen e -gsh è stata inoltre studiata la dipendenza dei parametri termodinamici di formazione dei complessi dalla forza ionica nell’intervallo 0 ≤ I ≤ 1 mol L-1 (NaNO3). I dati sperimentali hanno messo in evidenza la formazione per tutti i sistemi della specie ML con una elevata stabilità (logβ = 16.06-17.94) e della specie MLH, oltre a MLH2 (per pen e gsh) e MLOH (per tla, mpa e tma). La capacità sequestrante è espressa mediante il parametro pL50 che definisce la quantità di legante necessaria per sequestrare il 50% di ione metallico presente in soluzione

Highly untangled multiwalled carbon nanotube@polyhedral oligomeric silsesquioxane ionic hybrids: Synthesis, characterization and nonlinear optical properties

Abstract Highly de-bundled multiwalled carbon nanotube (MWCNT) polymer nanohybrids were obtained via ionic assembling of a novel POSS-polyimidazolium-ionic liquid (POSS = polyhedral oligomeric silsesquioxanes) with oxidized MWCNTs. The synthesis, accomplished by a simple bilayer chloroform/water metathetical reaction process, was promoted by the high surfactant properties of POSS-imidazolium-polyionic liquid, which assisted the effective de-bundling, dispersion and purification of the as prepared POSS@MWCNT polymers in organic media, via a surface coating mechanism. The presence of remarkably intense radial breathing modes (RBMs) in Raman spectra, both in solution and as solid, corroborates the effectiveness of the de-bundling process induced by the amphiphilic POSS polymeric ionic liquid (polyIL). This was, further, substantiated by scanning and transmission electron microscopy images. The nonlinear optical (NLO) behavior of POSS@MWCNT was investigated by Z-scan technique, which revealed a remarkable susceptibility \u3c7(3) of 2.38\ub710-7 esu mainly due to a dispersive effect. A good optical limiting (OL) performance, under a 532 nm pulsed excitation, was observed as well

Risedronate complexes with Mg2+, Zn2+, Pb2+, and Cu2+: Species thermodynamics and sequestering ability in NaCl(aq) at different ionic strengths and at T = 298.15 K

In this paper, potentiometry and calorimetry were used to determine the thermodynamics of interaction between risedronate and four bivalent metal cations, namely: Mg2+, Zn2+, Pb2+, and Cu2+ in aqueous NaCl solutions at different ionic strengths and at T = 298.15 K. The data analysis allowed us to ascertain that the main species formed were the MLH2, MLH, ML and M2L; however scarcely soluble species precipitated at acidic pH values, between 4 and 7 depending on the metal cation involved, probably due to the formation of the neutral M2L(s) species. Comparison of the stability constants with other similar ligands suggests that metal complexation occurs through the phosphonate with an additional stabilizing contribution due to the pyridine moiety. The dissection of the free energy term revealed that the entropic change is the main contribution to the stability of the complexes for all equilibria, except those regarding the formation of the M2L species, and the main forces involved in these processes are entropic in nature, such as the desolvation of both the ligand and the metal cations. The sequestering ability was evaluated computing the pL0.5 parameter at different pH and ionic strength values; the highest ones were found for Cu2+ in acidic solutions and at low ionic strength, whereas pL0.5 values for both Pb2+ and Zn2+ were slightly lower. Results reported in this work may be helpful in the assessment of the use of risedronate as effective chelating agent and for understanding the mechanism of action of this molecule as a drug