Dimitrios Kalderis

Soils contaminated with explosives: Environmental fate and evaluation of state-of- the-art remediation processes (IUPAC Technical Report)*

An explosion occurs when a large amount of energy is suddenly released. This energy may come from an over-pressurized steam boiler, from the products of a chemical reaction involving explosive materials, or from a nuclear reaction that is uncontrolled. In order for an explosion to occur, there must be a local accumulation of energy at the site of the explosion, which is suddenly released. This release of energy can be dissipated as blast waves, propulsion of debris, or by the emission of thermal and ionizing radiation. Modern explosives or energetic materials are nitrogen-containing organic compounds with the potential for self-oxidation to small gaseous molecules (N2, H2O, and CO2). Explosives are classified as primary or secondary based on their susceptibility of initiation. Primary explosives are highly susceptible to initiation and are often used to ignite secondary explosives, such as TNT (2,4,6-trinitrotoluene), RDX (1,3,5-trinitroperhydro-1,3,5-triazine), HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocane), and tetryl (N-methyl-N-2,4,6-tetranitro-aniline).

Ultrasound-assisted removal of Acid Red 17 using nanosized Fe3O4-loaded coffee waste hydrochar.

The Fe3O4-loaded coffee waste hydrochar (Fe3O4-CHC) was synthesized using a simple precipitation method. The as-prepared adsorbent was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and Fourier transform infrared spectroscopy (FT-IR). The EDX analysis indicated the presence of Fe in the structure of Fe3O4-CHC. The specific surface area of hydrochar increased from 17.2 to 34.7m2/g after loading of Fe3O4 nanoparticles onto it. The prepared Fe3O4-CHC was used for removal of Acid Red 17 (AR17) through ultrasound-assisted process. The decolorization efficiency decreased from 100 to 74% with the increase in initial dye concentration and from 100 to 91 and 85% in the presence of NaCl and Na2SO4, respectively. The synthesized Fe3O4-CHC exhibited good stability in the repeated adsorption-desorption cycles. The high correlation coefficient (R2=0.997) obtained from Langmuir model indicated that physical and monolayer adsorption of dye molecules occurred on the Fe3O4-CHC surface. Furthermore, the by-products generated through the degradation of AR17 was identified by gas chromatography-mass spectrometry analysis.

Sonocatalytic degradation of an anthraquinone dye using TiO2-biochar nanocomposite

TiO2-biochar (TiO2-BC) nanocomposite was synthesized by sol-gel method. The characteristics of the prepared nanocomposite were examined using X-ray fluorescence, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and N2 adsorption-desorption analysis. The performance of synthesized TiO2-BC nanocomposite as efficient sonocatalyst was studied for the degradation of Reactive Blue 69 (RB69). Sonocatalytic degradation of RB69 in the presence of TiO2-BC nanocomposite could be explained by the mechanisms of hot spots and sonoluminescence. The optimized values for main operational parameters were determined as pH of 7, TiO2-BC dosage of 1.5g/L, RB69 initial concentration of 20mg/L and ultrasonic power of 300W. Furthermore, the effect of OH, h+ and O2- scavengers on the RB69 degradation efficiency was studied. Gas chromatography-mass spectroscopy analysis was used to identify intermediate compounds formed during the RB69 degradation. The results of repeated applications of TiO2-BC in the sonocatalytic process verified its stability in long-term usage.

Sonocatalytic degradation of Reactive Yellow 39 using synthesized ZrO2 nanoparticles on biochar

ZrO2-biochar (ZrO2-BC) nanocomposite was prepared by a modified sonochemical/sol-gel method. The physicochemical properties of the prepared nanocomposite were evaluated using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray fluorescence, Fourier transform infrared spectroscopy and Brunauer-Emmett-Teller model. The sonocatalytic performance of ZrO2-BC was investigated in sonochemical degradation of Reactive Yellow 39 (RY39). The high observed sonocatalytic activity of the ZrO2-BC sample could be interpreted by the mechanisms of sonoluminescence and hot spots. Parameters including ZrO2-BC dosage, solution pH, initial RY39 concentration and ultrasonic power were selected as the main operational parameters and their influence on RY39 degradation efficiency was examined. A 96.8% degradation efficiency was achieved with a ZrO2-BC dosage of 1.5g/L, pH of 6, initial RY39 concentration of 20mg/L and ultrasonic power of 300W. In the presence of OH radical scavengers, RY39 degradation was significantly inhibited, providing evidence for the key role of hydroxyl radicals in the process. The sonodegradation intermediates were identified using gas chromatography-mass spectroscopy and the possible decomposition route was proposed.

Preparation of novel CeO2-biochar nanocomposite for sonocatalytic degradation of a textile dye

The sonocatalytic performance of CeO2 nanoparticles synthesized by a hydrothermal method (CeO2-H) and CeO2@biochar (CeO2-H@BC) nanocomposite, were evaluated for the degradation of Reactive Red 84 (RR84) under ultrasonic irradiation. For comparison purposes the corresponding performance of bare biochar (BC) and commercial CeO2 (CeO2-C) samples were also assessed. A complementary characterization study, involving scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), N2 adsorption at -196°C (Brunauer-Emmett-Teller (BET) method) and Fourier transform infrared spectroscopy (FT-IR) was undertaken to gain insight into the structure-performance relationships. The effect of various parameters such as initial RR84 concentration, solution pH, catalyst amount and ultrasonic power on the sonodegradation of RR84 was studied in detail. The results indicated that the CeO2-H@BC nanocomposite exhibited the best RR84 degradation efficiency, which is enhanced with the increase of CeO2-H@BC amount and ultrasonic power but diminished with the increment in RR84 concentration and pH value. A 98.5% degradation was obtained with a CeO2-H@BC amount of 1g/L, ultrasonic power of 450 W, pH of 6.5 and initial RR84 concentration of 10mg/L. The quenching effects of various scavengers proposed that OH radical plays the key role in the process. Analyses of intermediates by Gas chromatography-Mass spectroscopy (GC-MS) identified several by-products and accordingly the main pathway was proposed.

Synthesis of ZrO 2 nanoparticles on pumice and tuff for sonocatalytic degradation of rifampin

ZrO2-pumice and ZrO2-tuff nanocomposites were synthesized via a modified sol-gel method and used as efficient catalysts for sonocatalytic degradation of rifampin (RIF). The physico-chemical properties of the prepared catalysts were examined using XRF, SEM, EDX, FT-IR and BET analyses and compared to pure pumice and tuff samples. Subsequently, the efficacy of catalysts in degradation of RIF was assessed under various experimental conditions. Both ZrO2-pumice and ZrO2-tuff (1.5 g L-1) exhibited promising catalytic activity for sonocatalytic degradation of RIF at its initial concentration of 20 mg L-1, natural pH and under ultrasonic irradiation power of 300 W. In this condition, about 95% and 83% of RIF was removed through US/ZrO2-pumice and US/ZrO2-tuff processes, respectively. Furthermore, the influence of the addition of a number of scavengers, enhancers and gases on the degradation of RIF was studied. The pronounced degradation effectiveness of the catalysts under ultrasound irradiation could be assigned to their synergetic ability to produce reactive species and subsequent radical reactions. The intermediate products formed in the solution from degradation of RIF were also identified and a decomposition pathway was proposed using GC-MS, COD, TOC and IC analyses.