Francesco Venditti

Effects of sulfate ions and slightly acidic pH conditions on Cr(VI) adsorption onto silica gelatin composite

The feasibility of utilizing CTAB-silica gelatin composite (C-SGC) to remove hexavalent chromium from aqueous solutions under different conditions was investigated. Removal of chromate was assessed through evaluation of the adsorption kinetics of chromate ions on the composite under equilibrium conditions in the presence of sulfate ions and at a slightly acidic pH condition (pH 5.8). Adsorption competition tests in the presence of sulfate ions showed that Cr(VI) was still effectively adsorbed from aqueous solution regardless of the presence of the competing anions. In fact, the adsorption kinetics performed at different initial chromate concentrations were unaffected by the presence of 100 mg L(-1) sulfate ions (pH 7.5). The equilibrium adsorption data were fitted by Freundlich adsorption isotherms which confirmed that the adsorption efficiency of chromium on the CTAB-silica gelatin composite was unchanged in the presence of sulfate ions. Further, the adsorption process was shown to be pH dependent and more efficient at slightly acidic pH (5.8). These findings demonstrated a high specificity of the CTAB-silica gelatin composite for chromium, and highlight the possibility of using this matrix for efficient removal of chromium from industrial wastewater without the need to eliminate contaminant sulfate ions.

Visible light caffeic acid degradation by carbon-doped titanium dioxide

The removal of the phenolic compound, caffeic acid, by photodegradation has been investigated using carbon-doped titanium dioxide particles as a photocatalyst under visible light. UV-vis absorption spectroscopy and gas chromatography-ion trap mass spectrometry analyses revealed a substrate concentration dependence of the removal of caffeic acid from a water solution. The k2 and t(0.5) parameters of each reaction were calculated by fitting kinetics data to a second-order kinetic adsorption model. To evaluate the photodegradation event, the effect of the adsorption process on the whole degradation was also monitored in the absence of light. Adsorption isotherm studies supported by ζ potential and scanning electron microscopy data demonstrated the pivotal role of the absorption mechanism. It was found that the whole photodegradation process is governed by a synergic mechanism in which adsorption and photodegradation are involved. This study, centered on the removal of caffeic acid from aqueous solutions, highlights the potential application of this technology for the elimination of phenolic compounds from olive mill wastewater, a fundamental goal in both the agronomical and environmental fields.

Cleaning of olive mill wastewaters by visible light activated carbon doped titanium dioxide

Carbon doped titanium dioxide (CDT) was tested as catalyst for photodegradation of phenolic compounds of olive mill wastewater (OMW). The activation of the catalyst was triggered by exposure to visible light radiation. The cleaning effectiveness of this catalyst towards the polluted wastewater from olive oil industry was demonstrated by means of HPLC and UV-visible spectroscopy combined with phenol compound determination. The photodegradation activity was tested on systems having different initial concentration of phenols and in the presence of different amounts of CDT. By introducing a suitable parameter, namely the ratio between the amount of catalyst and the amount of total phenols Ti/TPh, it was demonstrated that the proposed degradation method could be scaled up without losing its effectiveness. The OMW decolorization occurring in the presence of CDT particles under visible light radiation is marked enough to be directly appreciated with the naked eye. The decolorization is strongly associated with the removal of phenols. In fact, while bleaching the solutions, CDT successfully removed 70% of the phenols in 24 hours. HPLC analysis demonstrates that CDT was effective in degrading the higher part of the phenols of OMW. An exception is represented by hydroxytyrosol that seemed to have high resistance in the first 24 hours of treatment.

Olive Mill Wastewater (OMW) Phenol Compounds Degradation by Means of a Visible Light Activated Titanium Dioxide-Based Photocatalyst

Abstract The use of titanium dioxide as heterogeneous photocatalyst is drawing considerable attention for water and air purification and remediation. Recently, TiO2 particles have been modified in order to make this material attractive for industrial and environmental remediation usage. In the present study, phenolic compounds of olive mill wastewater (OMW) were degraded in the presence of glucose-doped titanium particles (CDT) through a photocatalysis process activated by visible light. The photocatalyst effectiveness towards the polluted wastewater from olive oil industry was tested on systems having different initial concentrations of phenols and in the presence of different amounts of CDT. For kinetic analysis the role of Ti/TPh ratio (amount of catalyst/amount of total phenols) was investigated. The rate constant (k2) and the amounts of species adsorbed on adsorbent at equilibrium (qe) of each reaction were calculated by fitting kinetics data to a second-order kinetic adsorption model. The results collected at different Ti/TPh ratios showed that the amount of phenols that can be removed from the water solution linearly increases with the Ti/TPh ratio till a maximum value (optimal ratio) at which no further degradation of phenolic compounds was obtainable. Such kind of parameter allows to identify the optimal value of catalyst and the initial substrate concentration for a high level of degradation. The results showed in this study can have an important impact for an applicative point of view.

In-vitro digestion of curcumin loaded chitosan-coated liposomes

Liposomes are considered a major route for encapsulation of hydrophilic and hydrophobic molecules. Chitosan coated liposomes could represent an alternative way as a carrier for delivery of drugs in human body. In this study the preparation and applicability of chitosan-coated liposomes containing curcumin as well as curcumin loaded anionic liposomes were evaluated. The applicability of the carriers was tested by means of an in-vitro digestion procedure allowing for measurement of the bioaccessibility of ingested curcumin. Values of diameter, polydispersity index and surface charge for curcumin loaded anionic liposomes obtained through dynamic light scattering and ζ-potential measurements were 129nm, 0.095 and -49mV, respectively. After chitosan-coating, diameter and polydispersity index remain unvaried while the surface charge gets positive. Slightly higher curcumin concentrations were found after the mouth and the stomach digestion phases when curcumin was loaded in anionic liposomes. On the contrary, after the intestinal phase, a higher percentage of curcumin was found when chitosan-coated liposomes were used as carrier, both in the raw digesta and in the bile salt micellar phase. It was shown that the presence of a positively charged surface allows a better absorption of curcumin in the small intestine phase, which increases the overall curcumin bioavailability. The mechanism behind these results can be understood from the composition of the different environments generated by the digestive fluids that differently interact with anionic or cationic surfaces.