Nature of Interactions at the Interface of Two Water-Saturated Commercial TiO2 Polymorphs

Two commercial TiO2 samples, a 100% anatase and a 100% rutile, were used for the fast field cycling NMR experiments. The results showed a different behavior between the different samples. In particular, water molecules were unbonded to the solid surface for the rutile sample, whereas they appeared to chemically interact with the surface through H-bond formation with the anatase sample. The above findings accord with the generally lower activity of rutile with respect to anatase reported in literature for photocatalytic oxidation reactions in water. The difficulty of water to interact with rutile surface, indeed, could hinder the formation of OH radicals, which are the most important oxidant…

EFFECT OF METALS ON THE DYNAMICS OF WATER AT THE BIOCHAR SOLID-LIQUID INTERFACE

Previous studies revealed that water molecules are hooked to biochar surfaces through unconventional hydrogen bonds (De Pasquale et al., 2012; Conte et al., 2013). Next question to answer is how metals can affect water mobility as they are adsorbed on biochar surface. To this aim, an orchard pruning char obtained by pyrolysis at 500°C was treated with solutions of Cu(II), Cr(VI) and Cu(II)+Cr(VI). Two different types of water can be recognized in BC. Namely, a fast relaxing water (T1 = 99 ms) is differentiated by a slow relaxing one (T 1= 233 ms). The former is made by molecules interacting with biochar surface through formation of the unconventional Hbonds previously identified (De Pasqual…

Fast field cycling NMR relaxometry characterization of biochars obtained from an industrial thermochemical process

Biochar has unique properties which make it a powerful tool to increase soil fertility and to contribute to the decrease of the amount of atmospheric carbon dioxide through the mechanisms of C sequestration in soils. Chemical and physical biochar characteristics depend upon the technique used for its production and the biomass nature. For this reason, biochar characterization is very important in order to address its use either for agricultural or environmental purposes. Three different biochars obtained from an industrial gasification process were selected in order to establish their chemical and physical peculiarities for a possible use in agronomical practices. They were obtained by char…

Structure alteration of a sandy-clay soil by biochar amendments

The aim of the present study was to investigate structure alterations of a sandy-clay soil upon addition of different amounts of biochar (f bc ). All the f bc samples were analyzed by high energy moisture characteristic (HEMC) technique and 1H nuclear magnetic resonance (NMR) relaxometry. HEMC was applied in order to evaluate aggregate stability of biochar-amended soil samples. 1H NMR relaxometry experiments were conducted for the evaluation of the pore distributions through the investigation of water dynamics of the same samples. The HEMC technique revealed improvement in aggregate stability through measurements of the amount of drainable pores and the stability ratio. The latter increased…

Nature of water-biochar interface interactions

A poplar biochar obtained by an industrial gasification process was saturated with water and analyzed using fast field cycling (FFC) NMR relaxometry in a temperature range between 299 and 353 K. Results revealed that the longitudinal relaxation rate increased with the increment of the temperature. This behavior was consistent with that already observed for paramagnetic inorganic porous media for which two different relaxation mechanisms can be accounted for: outer- and inner-sphere mechanisms. The former is due to water diffusing from the closest approach distance to infinity, whereas the second is due to water interacting by nonconventional H-bonds to the porous surface of the solid materi…

EFFECTS ON SEED GERMINATION OF DIFFERENT BIOCHARS FROM INDUSTRIAL THERMOCHEMICAL PROCESSES

Char or biochar is a type of charcoal obtained from gasification/pyrolysis of biomasses. Instead of burning standing biomass from cleared forest, the resource is charred. The result is a highly porous, carbon-rich solid residue, really similar in appearance to the coal produced by natural burning. First considered an industrial waste, in recent years, the interest in this material has grown enormously given its ability to improve physical, chemical, biological and mechanical properties of soils, when used as amendment. However, its effects are highly variable depending onits chemical-physical properties which in turn depend greatly on the starting feedstock. The present study reports about …

DINAMICA DELL’ACQUA SULLA SUPERFICIE DI UN BIOSSIDO DI TITANIO NANOSTRUTTURATO SINTETIZZATO IN LABORATORIO

Un campione biossido di titanio sintetizzato in laboratorio è stato ottenuto mediante idrolisi di TiCl4 in acqua deionizzata (rapporto in volume 1:10) a temperatura ambiente. Dopo 12 h di agitazione la soluzione trasparente è stata portata all’ebollizione per 0.5 h per ottenere la sospensione finale. La sospensione è stata quindi seccata alla temperatura di 50°C per ottenere il catalizzatore in polvere. Successivamente, la polvere così ottenuta è stata lavata e centrifugata diverse volte allo scopo di ridurre fino a valori trascurabili la concentrazione di ioni cloruro nell’acqua di lavaggio. Il catalizzatore così ottenuto è stato denominato HP0.5 (Home Prepared bollito per 0.5 h) [1]. Un g…

Regeneration of cellulose by water addition to phosphoric acid/cellulose mixture

In the last years, phosphoric acid has been increasingly considered as a simple and economic solvent for cellulose pretreatment before its degradation to glucose. Cellulose swells in 71–80% phosphoric acid solutions, whereas at higher H3PO4 concentrations dissolution appears to occur. In addition, it is reported that regenerated cellulose is more easily fermentable to bioethanol. The aim of the present study was to elucidate the mechanism for cellulose regeneration following treatment with phosphoric acid at room temperature. CPMAS 13C NMR spectra revealed a downfield shift of the 13C NMR signals from the regenerated cellulose as compared to the crystalline one. CPMAS 31P NMR spectroscopy s…

Mechanisms of Water Interaction with Pore Systems of Hydrochar and Pyrochar from Poplar Forestry Waste

The aim of this study was to understand the water-surface interactions of two chars obtained by gasification (pyrochar) and hydrothermal carbonization (hydrochar) of a poplar biomass. The two samples revealed different chemical compositions as evidenced by solid state (13)C NMR spectroscopy. In fact, hydrochar resulted in a lignin-like material still containing oxygenated functionalities. Pyrochar was a polyaromatic system in which no heteronuclei were detected. After saturation with water, hydrochar and pyrochar were analyzed by fast field cycling (FFC) NMR relaxometry. Results showed that water movement in hydrochar was mainly confined in very small pores. Conversely, water movement in py…

Assessing the influence of different biochar fractions on soil structure and soil water retention: laboratory investigation on a Sicilian soil

STUDY OF CHEMICAL-PHYSICAL PROPERTIES IN INDUSTRIAL BIOCHAR

BIOCHAR SURFACE PROPERTIES THROUGH APPLICATION OF AN INNOVATIVE NMR TECHNIQUE: FAST FIELD CYCLING RELAXOMETRY

Biochar is a carbonaceous material obtained by pyrolysis of biomass feedstocks. It is applied to soils in order to improve fertility and mitigate greenhouse-gases emissions. In fact, from the one hand, biochar changes physical-chemical soil properties, thereby affecting soil fertility. From the other hand, biochar is resistant to chemical and biochemical degradation. For this reason, its use allows carbon sequestration in soils and consequent reduction of carbon dioxide to the atmosphere. Here, dynamics of water at the liquid-solid interface of water saturated biochars is discussed. Results revealed that water dynamics is affected by the nature of biochar parent biomasses. Moreover, biochar…