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Three alkylpolyoxyethylene surfactants bearing the same hydrophobic chain and a different number of oxyethylene groups were investigated as suitable candidates for the soil washing treatment of contaminated soil samples containing bentazone. Comparable good recoveries of the pesticide were obtained working with these surfactants. The photocatalytic treatment of the collected washing wastes, performed in the presence of suspended TiO 2 particles under irradiation with simulated sunlight, leads to the effective degradation of bentazone residues after a time depending on the nature and concentration of the chosen amphiphile. Brij 35 was found to be the best surfactant candidate, giving the faster abatement of the pesticide in the collected wastes. The overall treatment time depends on the bentazone mineralization kinetics, markedly slow in the presence of surfactants. Useful information about the photocatalytic degradation route was obtained from the HPLC–MS analysis of transient intermediates formed in water.

Nitrobenzene thermal degradation was investigated using the Fenton reagent in different experimental conditions. Reaction products were analyzed by HPLC, GC–MS, LC–MS and IC. The products obtained at different nitrobenzene conversion degrees show that degradation mainly involves successive hydroxylation steps of the aromatic ring and its subsequent opening followed by oxidation of corresponding aliphatic compounds. Our results show as primary reaction products: 4-nitrophenol, 3-nitrophenol, 2-nitrophenol, phenol and 1,3-dinitrobenzene, indicating that both hydroxylation and nitration reactions are involved. The formation of phenolic products can be explained by postulating an initial step of HO addition to nitrobenzene ring. The mechanisms of primary reaction pathways are discussed and a detailed kinetic analysis to obtain the true primary yields of phenolic products is proposed. The relative yields observed for nitrophenol isomers do not follow the expected orientation according to deactivating characteristics of the nitro group but significantly depend on Fe+2, Fe+3, H2O2 and O2 concentrations. The understanding of the effect of reaction conditions on the relative product distribution benefits the application of Fenton and Fenton-like systems to waste water treatment.

The effect of ionic and non-ionic aliphatic surfactants on the photocatalytic degradation of Carbaryl (1-naphtyl-N-methylcarbamate) in aqueous solutions containing suspended TiO2 (anatase) particles, under irradiation with simulated AM1 solar light, was investigated. A neat inhibitory effect on the degradation rate was observed, depending on the nature of the surfactant and on the initial pH of the solution. The decay profiles of the primary process corresponded to the usual pseudo-first order kinetics for surfactant concentrations below the critical micellar concentration range, whereas a more complicate behaviour was observed in the presence of micellar aggregates. Mineralization of the pesticide to CO2, NO3− and NH4+ was evidenced also in the presence of added amphiphiles, suggesting the feasibility of photocatalytic treatment of surfactant-containing aqueous wastes.

The decomposition of naphthalene in the presence of TiO2 dispersions irradiated with simulated solar light has been investigated in water and in aqueous Brij 35 solutions, used to wash soil samples containing the adsorbed pollutant. The monitoring of the reaction system performed during the treatment showed the formation of various aromatic intermediates, in turn degraded, which were identified using suitable analytical techniques. Fast and complete mineralization of naphthalene to CO2 was achieved when working in the absence of additives, whereas a neat inhibition of the degradation was observed in the presence of amphiphiles and other organic components coming from soil. Experimental conditions under which surfactant-containing washes can be treated were investigated and defined.

The versatility and efficiency of the VUV photolysis of water as an “Advanced Oxidation Procedure” for the light-induced oxidative degradation of atrazine as a pollutant of surface and ground waters is evaluated. The oxidation of atrazine using TiO2 as a photocatalyst has been reported to produce almost stoichiometric amounts of cyanuric acid. Mineralization to CO2, water and inorganic nitrogen containing ions occurred to a very low extent implying that cyanuric acid is resistant to further degradation under the chosen experimental conditions. Our present results show that in oxygen saturated solutions 50% of the initial atrazine is converted to cyanuric acid, whereas only 10% of the initial atrazine is isolated as cyanuric acid in argon saturated solutions. The results indicate that mineralization is more efficient in not strictly oxidative reaction media.

The possible application of two environmental remediation technologies – soil washing and photocatalysis – to remove and decompose various aromatic pollutants present in excavated soils of a contaminated industrial site has been investigated. Aqueous solutions containing the non-ionic surfactant Brij 35 were used to extract the contaminants from the soil samples. The photocatalytic treatment of the obtained washing wastes, performed in the presence of TiO2 suspensions irradiated with simulated sunlight, showed a slow abatement of the toxic compounds due to the relevant concentrations of organics in the waste. A neat improvement of the process performances, obtained by operating in the presence of added potassium peroxydisulfate, suggests a feasible treatment route.