Application of the differential neural network observer to the kinetic parameters identification of the anthracene degradation in contaminated model soil

Effect of the type of soil on dimethyl phthalate degradation by ozone

In the present study, ozone was applied for the removal of dimethyl phthalate (DMP) from soil. The effect of several experimental parameters was investigated considering, the initial DMP concentration, ozone flow, the type of soil (sand and agricultural soil) and the presence of α-FeOOH as a potential catalyst in the reaction system with sand. The elimination of DMP using ozone is significantly affected by the type of soil. In the case of sand, conventional ozonation was capable to degrade 74% of the initial DMP concentration (0.5 mg g^-1) after 8 h of the reaction, however, the mineralization degree was below 50%. Under the same experimental conditions, the complete elimination of DMP was achieved when calcined agricultural soil was present reaching a 70% of mineralization. The presence of metal oxides in calcined agricultural soil combined with ozone produced oxidants species which were responsible of incrementing the mineralization degree (around 20% in comparison with the sand). The toxicity tests on lettuce seed demonstrated lower toxicity of DMP byproducts after ozonation. The DMP high removal efficiencies and the lower toxicity of generated byproducts in soil prove the applicability of ozone treatment for soil remediation.

Phenanthrene degradation in soil by ozonation: Effect of morphological and physicochemical properties

The aim of this study was to characterize the ozone reaction with phenanthrene adsorbed in two types of soils (sand and agricultural). The effect of soil physicochemical properties (texture, bulk density, particle density, porosity, elemental composition, permeability, surface area and pore volume) on the phenanthrene decomposition was evaluated. Commercial sand has a uniform morphology (spherical) with a particle size range between 0.178 and 0.150 mm in diameter, regular elemental composition SiO₂, specific density of 1701.38 kg/m³, a true density of 2492.50 kg/m³, with an effective porosity of 31%. On the other hand, the agricultural soil had heterogeneous morphology, particle size between 0.1779 and 0.05 mm in diameter, elemental composition was montmorrillonite silicon oxide, apparent density of 999.52 kg/m³, a true density of 2673.55 kg/m³, surface area of 34.92 m²/g and porosity of 57%. The percentage of phenanthrene decomposition in the sand was 79% after 2 h of treatment. On the other hand, the phenanthrene degradation in the agricultural soil was 95% during the same reaction time. The pore volume of soil limited the crystal size of phenanthrene and increased the contact surface with ozone confirming the direct impact of physicochemical properties of soils on the decomposition kinetics of phenanthrene. In the case of agricultural soil, the effect of organic matter on phenanthrene decomposition efficiency was also investigated. A faster decomposition of initial contaminant and byproducts formed in ozonation was obtained in natural agricultural soil compared to the sand. The partial identification of intermediates and final accumulated products produced by phenanthrene decomposition in ozonation was developed. Among others, phenanthroquinone, hydroquinone, phenanthrol, catechol as well as phthalic, diphenic, maleic and oxalic acids were identified.

Anthracene decomposition in soils by conventional ozonation

Anthracene decomposition in solid phase by conventional ozonation was investigated employing model and real soil samples. Reaction in a two-phase system (soil-ozone) and a three-phase system (soil-water-ozone) was studied. The total anthracene decomposition in the two studied systems (sand-ozone and burned soil-ozone) was obtained at 15 and 30 min of treatment by ozone, respectively, and the efficiency of ozonation was depended on the water content in treated soil samples. The anthracene degradation in an agricultural soil (free water) was carried up slower (only 30% after 90 min of ozonation), because the real solid samples content organic matter that provokes the additionally ozone consuming. The pre-ozonation of free anthracene agricultural soil depicts the content of the organic matter fraction, which have the ozone reactivity orders as aromatic>aliphatic>polar. In all cases, the ozonation by-products were identified partiality; the majority of by-products formatted react with ozone. Actually some of them were decomposed totally, while others were accumulated. Some products identified in all systems such as anthrone, 9,10-anthraquinone and phthalic acid, are less toxic than the anthracene.

BTEX decomposition by ozone in gaseous phase

Environment management is turning its efforts to control the air pollution. Nowadays, gas phase contaminants coming from different sources are becoming into the main cause of serious human illness. Particularly, benzene, toluene, ethylbenzene and xylene (BTEX) are getting more and more attention from the scientific community due the high level of volatilization showed by these compounds and their toxicity. Decomposition of these compounds using different treatments is requiring lots of new strategies based on novel options. In the present work the use of ozone was proposed as possible alternative treatment in the gaseous phase of VOC's liberated from water by stripping. This study deals with the decomposition by ozone in gaseous phase of model mixtures of BTEX stripped from water. The experiments were realized in a tubular reactor with fixed length (1.5 m length and diameter of 2.5 cm). The experiments were conducted in two stages: in the first one, organics was ventilated by oxygen flow to liberate BTEX to the gaseous phase; second stage deals with the liberated BTEX decomposition by ozone in the tubular reactor. Ozonation efficiency was determined measuring the VOC's concentration at the output of the tubular reactor. This concentration was compared to the concentration obtained at the input of the reactor. The obtained results confirm the possibility to use of ozone for the VOC's decomposition in gaseous phase. Also, the dynamic relationship between degradation and liberation was studied and characterized.