Ecofriendly in-line process monitoring: a case study. Anthracene photodegradation in the presence of refuse-derived soluble bio-organics.

Photodegradation of anthracene has been studied in aqueous solutions containing soluble bio-organic substances isolated from urban refuse. To perform a preliminary rapid feasibility study of this process while reducing the amount of analytical effort and reagents, an experimental set-up was developed comprising a Teflon coil surrounding a UV-lamp and coupled with an in-line spectrofluorimeter. In this fashion only few millilitres of solution are needed to study the degradation process. Furthermore, the in-line spectroscopic approach enables monitoring of the process without consumption of reagents. Additional studies by liquid chromatography and use of toxicity tests clearly indicated that the apparent inhibition effect of bio-organic compounds on anthracene degradation is not relevant. The results imply that urban refuse may be used as an auxiliary in the recovery of polycyclic aromatic hydrocarbons from contaminated soil by washing, without deleterious effects on the photodegradation of anthracene and other aromatic pollutants.

Urban biowaste-derived sensitizing materials for caffeine photodegradation.

Caffeine-photosensitized degradation has been studied in the presence of bio-based materials derived from urban biowaste after aerobic aging. A peculiar fraction (namely bio-based substances (BBSs)), soluble in all the pH range, has been used as photosensitizing agent. Several caffeine photodegradation tests have been performed, and positive results have been obtained in the presence of BBSs and H2O2, without and with additional Fe(II) (photo-Fenton-like process). Moreover, hybrid magnetite-BBS nanoparticles have been synthesized and characterized, in order to improve the sensitizer recovery and reuse after the caffeine degradation. In the presence of such nanoparticles and H2O2 and Fe(II), the complete caffeine degradation has been attained in very short time. Both homogeneous and heterogeneous processes were run at pH = 5, milder condition compared to the classic photo-Fenton process.

Analytical monitoring of photocatalytic treatments. Degradation of 2,3,6-trichlorobenzoic acid in aqueous TiO(2) dispersions.

The photocatalytic degradation of 2,3,6-trichlorobenzoic acid (2,3,6-TBA) in aqueous TiO(2) dispersions irradiated with simulated solar light was investigated. Fast primary degradation of the herbicide, which obeys a pseudo-first order law, was observed. Complete mineralisation of the organic carbon to CO(2) was obtained after long term irradiation, with corresponding stoichiometric transformation of organic chlorine into chloride ion. Various aromatic intermediates, originating from 2,3,6-TBA, were detected during the treatment and identified using GC-MS. From the analytical data, a possible multi-step degradation scheme was proposed. The photocatalytic treatment of the pesticide was also performed in the presence of Brij 35 micellar solutions, although strong inhibition of the process was observed. When surfactant aggregates are present the photocatalytic destruction of 2,3,6-TBA is still possible at reasonable rates only after a proper dilution of the waste and by increasing significantly the semiconductor/pollutant ratio.

Continuous monitoring of photocatalytic treatments by flow injection. Degradation of dicamba in aqueous TiO2 dispersions.

The possible use of flow injection (FI) to monitor the photocatalytic mineralization of dicamba (3,6-dichloro-2-methoxybenzoic acid) present at the trace level in aqueous solutions containing TiO2 suspensions has been evaluated. Experiments were performed in a stirred photochemical reactor equipped with a simple FI manifold, integrating an online filtration unit able to perform the monitoring of the UV absorbance of the irradiated solution every 4 min. The light source used was a medium pressure mercury lamp (125 W). During the initial steps of the reaction the formation of UV absorbing intermediates, which completely disappear in less than 80 min, was evidenced. Additional HPLC, DOC and chloride ion measurements carried out on manually taken samples confirmed the complete mineralization of dicamba within about 90 min. The proposed on-line monitoring looks particularly suitable for the control of degradation treatments where primary degradation and mineralization steps take place after a comparable irradiation time.

Microwave-assisted extraction of polycyclic aromatic hydrocarbons from marine sediments using nonionic surfactant solutions.

Microwave-assisted micellar extraction (MAME) has been tested for the recovery of polycyclic aromatic hydrocarbons (PAHs) present in samples of marine sediments. An aqueous solution of the nonionic surfactant polyoxyethylene(23)dodecyl ether (Brij 35) was employed as the extracting medium. The proposed approach showed recovery efficiencies comparable to those afforded by the Soxhlet technique with organic solvents, but a neat reduction of the extraction times and a better reproducibility were observed. A MAME-based protocol was successfully applied for the analysis of a certified sample.

Analytical control of photocatalytic treatments: degradation of a sulfonated azo dye.

The degradation of Methyl Orange (C(14)H(14)N(3)SO(3)Na), chosen as a model sulfonated azo dye, was investigated in aqueous solutions containing suspended polycrystalline TiO(2) particles under irradiation with simulated sunlight. The dye disappearance and the formation of the mineralization end products were monitored; the formation of the main transient intermediates was also examined in detail. Particular attention was devoted to the identification and to the evolution of fragments retaining the chromophoric group. The comparison of data coming from various analytical techniques led to a possible reaction mechanism for the degradation process, giving insight into an aspect of the treatment which has not been considered in previous studies.