Dimitris Kalderis | University of Leeds (original) (raw)

Papers by Dimitris Kalderis

International Journal of Environmental Science and Technology, Dec 25, 2023

The objectives of this study were to evaluate sewage sludge's stabilization with untested until n... more The objectives of this study were to evaluate sewage sludge's stabilization with untested until now materials, such as selective clay minerals or biochar in comparison with liming, for enhancing sludge's fertilization capacity. Dewatered sewage sludge was mixed with bentonite, vermiculite, zeolite, biochar or lime at rates of 0, 15 and 30%, air-dried and analyzed for pathogens and chemical properties. Almost all fecal indicators of treated sludge with 15% bentonite, vermiculite or biochar were reduced by at least one-logarithmic unit (log 10) (indicative value of sludge's stabilization), whereas those of limed sludge were undetectable. Electrical conductivity of all treatments significantly increased, and the highest values were obtained for untreated (6.1 dS m −1) and limed sludge (above 7.0 dS m −1 for both addition rates). The untreated sludge had the significantly highest water-soluble ammonium-nitrogen (2817 mg kg −1) and phosphorus (263 mg kg −1) concentrations followed by sludge treated with bentonite, vermiculite or biochar, whereas limed sludge had the lowest content. Boron concentration of the untreated sludge was similar to the treated sludge. Total concentrations of heavy metals were far below the legislative permissible levels for sludge's agronomic use. Nutrients' total content of treated sludge ranged at levels of similar magnitude to the untreated sludge, except for certain cases where they were increased because of the materials' composition. Consequently, sewage sludge treated with 15% bentonite, vermiculite or biochar seems to be stabilized, retain bioavailable nitrogen and serve as a fertilizer of macro-and micronutrients. However, potential risks of agronomic use, i.e., soil salinization and boron phytotoxicity, should be considered.

Chemosphere, 2021

In a column set-up, Fe modified biochar produced from date palm leaves was used to remove As (1 m... more In a column set-up, Fe modified biochar produced from date palm leaves was used to remove As (1 mg L-1) from a laboratory-prepared wastewater. The wastewater treatment process was monitored in real-time by spectral induced polarization (SIP), over a wide range of frequencies (0.01-1000 Hz). Both 5 and 10% biochar-amended columns achieved As removal exceeding 98%. The SIP parameters appear to be sensitive on As removal processes, with the recorded trend following the conventional geochemical monitoring, while offering higher temporal resolution.

Journal of Environmental Management

A novel sulfur-rich adsorbent, poly(BA-ala-co-sulfur), was synthesized by reacting allyl function... more A novel sulfur-rich adsorbent, poly(BA-ala-co-sulfur), was synthesized by reacting allyl functional benzoxazine (BA-ala) and elemental sulfur. Simultaneous inverse vulcanization and ring-opening reactions of benzoxazine generated copolymers in several feed ratios. The adsorption behavior of these copolymers was investigated in aqueous solutions containing Hg 21 . A three level Box-Behnken design with four factors was applied in order to examine the interactive effect of Hg 21 concentration (ppm), S % in adsorbent, temperature, and pH. The optimum adsorption conditions were determined as: 10.33 ppm Hg 21 , 68% S content, 329 K, and pH 6.3. Common isotherm and kinetic models were applied to the experimental data, where the Langmuir isotherm provided the better fit (q max 5 79.36 mg g 21 ) and the pseudo-second order fit indicated chemisorption as the process-controlling step.

In this study, subcritical water has been used as a medium for degradation of 2,4-dinitrotoluene ... more In this study, subcritical water has been used as a medium for degradation of 2,4-dinitrotoluene (2,4-DNT), 4-nitrotoluene (4-NT) and 2-amino-4-nitrotoluene (2-A-4-NT). The effect of temperature, oxidant concentration and time were studied and the optimal combination of reaction parameters was established using response surface methodology in a Box-Behnken design. Of all the parameters examined, temperature showed the most positive effect on the degradation of the nitroaromatic compounds. Optimal reaction conditions were found to be a temperature of 240°C, 210°C and 236°C, time of 180, 178 and 172 min, oxidant concentration of 100, 99.64 and 99.61 mM for 2,4-DNT, 4-NT and 2-A-4-NT, respectively. Since high-temperature was applied, the possibility of formation of subcritical degradation products existed; therefore, total amounts of degraded nitroaromatic compounds and formed intermediate products were determined by gas chromatographic-mass spectrometric analysis.

А г р о ф и з и к а 2015 № 4 1 Физика, биофизика и экология почв УДК 57.033; 631.95 ВЛИЯНИЕ РАЗЛИ... more А г р о ф и з и к а 2015 № 4 1 Физика, биофизика и экология почв УДК 57.033; 631.95 ВЛИЯНИЕ РАЗЛИЧНЫХ ВИДОВ ГИДРОУГЛЯ НА ЭМИССИЮ УГЛЕКИСЛОГО ГАЗА, ЗАКИСИ АЗОТА И РОСТ РАСТЕНИЙ Поступила в редакцию 11 сентября 2015 г., принята к печати 08 декабря 2015 г.

TiO 2 -biochar (TiO 2 -BC) nanocomposite was synthesized by sol-gel method. The characteristics o... more TiO 2 -biochar (TiO 2 -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 N 2 adsorption-desorption analysis. The performance of synthesized TiO 2 -BC nanocomposite as efficient sonocatalyst was studied for the degradation of Reactive Blue 69 (RB69). Sonocatalytic degradation of RB69 in the presence of TiO 2 -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, TiO 2 -BC dosage of 1.5 g/L, RB69 initial concentration of 20 mg/L and ultrasonic power of 300 W. Furthermore, the effect of % OH, h + and O 2 %− 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 TiO 2 -BC in the sonocatalytic process verified its stability in long-term usage.

Journal of Agricultural and Food Chemistry, 2015

Biochar produced by pyrolysis of organic residues is increasingly used for soil amendment and man... more Biochar produced by pyrolysis of organic residues is increasingly used for soil amendment and many other applications. However, analytical methods for its physical and chemical characterization are yet far from being specifically adapted, optimized, and standardized. Therefore, the COST Action TD1107 conducted an inter-laboratory comparison, in which 22 laboratories from twelve countries analyzed three different types of biochar for 38 physical-chemical parameters (macro- and micro-elements, heavy metals, polycyclic aromatic hydrocarbons, pH, electrical conductivity, and specific surface area) with their preferential methods. The data was evaluated in detail using professional inter-laboratory testing software. Whereas intra-laboratory repeatability was generally good or at least acceptable, inter-laboratory reproducibility was mostly not (20% < mean reproducibility standard deviation < 460%). This paper contributes to better comparability of biochar data published already, and provides recommendations to improve and harmonize specific methods for biochar analysis in the future.

Journal of Agricultural and Food Chemistry, 2015

Biochar produced by pyrolysis of organic residues is increasingly used for soil amendment and man... more Biochar produced by pyrolysis of organic residues is increasingly used for soil amendment and many other applications. However, analytical methods for its physical and chemical characterization are yet far from being specifically adapted, optimized, and standardized. Therefore, the COST Action TD1107 conducted an inter-laboratory comparison, in which 22 laboratories from twelve countries analyzed three different types of biochar for 38 physical-chemical parameters (macro- and micro-elements, heavy metals, polycyclic aromatic hydrocarbons, pH, electrical conductivity, and specific surface area) with their preferential methods. The data was evaluated in detail using professional inter-laboratory testing software. Whereas intra-laboratory repeatability was generally good or at least acceptable, inter-laboratory reproducibility was mostly not (20% < mean reproducibility standard deviation < 460%). This paper contributes to better comparability of biochar data published already, and provides recommendations to improve and harmonize specific methods for biochar analysis in the future.

Currently, char substrates gain a lot of interest since soils amended with such substrates are be... more Currently, char substrates gain a lot of interest since soils amended with such substrates are being discussed to increase in fertility and productivity, water retention, and mit-igation of greenhouse gases. Char substrates can be produced by carbonization of organic matter. Among different process conditions, temperature is the main factor controlling the occurrence of organic and inorganic contaminants such as phenols and furfurals, which may affect target and non-target organisms. The hydrochar produced at 200 °C contained both furfural and phenol with concentrations of 282 and 324 mg kg −1 in contrast to the 300 °C hydrochar, which contained only phenol with a concentration of 666 mg kg −1. By washing with acetone and water, these concentrations were significantly reduced. In this study, the potential toxic effects of hydrochars on the free-living nematode Caenorhabditis elegans were investigated via gene transcription studies using the following four matrices: (i) raw rice husk, (ii) unwashed rice char, (iii) acetone/water washed rice char, and (iv) the wash water of the two rice chars produced at 200 and 300 °C via hydrothermal carbonization (HTC). Furthermore, genetically modified strains, where the green fluorescent protein (GFP) gene sequence is linked to a reporter gene central in specific anti-stress regulations, were also exposed to these matrices. Transgenic worms exposed to hydrochars showed very weak, if any, fluorescence, and expression of the associated RNAs related to stress response and biotransformation genes was surprisingly downregulated. Similar patterns were also found for the raw rice husk. It is hypothesized that an unidentified chemical trigger exists in the rice husk, which is not destroyed during the HTC process. Therefore, the use of GFP transgenic nematode strains cannot be recommended as a general rapid monitoring tool for farmers treating their fields with artificial char. However, it is hypothesized that the observed reduced transcriptional response with the subsequent lack of energy-consuming stress response is an energy-saving mechanism in the exposed nematodes. If this holds true in future studies, this finding opens the window to an innovative new field of stress ecology.

Biochar is the carbon-rich product obtained when biomass, such as wood, manure or leaves, is heat... more Biochar is the carbon-rich product obtained when biomass, such as wood, manure or leaves, is heated in a closed container with little or no available air. In more technical terms, biochar is produced by so-called thermal decomposition of organic material under limited supply of oxygen (O 2), and at relatively low temperatures (< 700 • C). Hy-drochar differentiates from biochar because it is produced in an aqueous environment, at lower temperatures and longer retention times. This work describes the production of hy-drochar from rice husks using a simple, safe and environmentally friendly experimental setup , previously used for degradation of various wastewaters. Hydrochars were obtained at 200 • C and 300 • C and at residence times ranging from 2 to 16 h. All samples were then characterized in terms of yield, surface area, pH, conductivity and elemental analysis , and two of them were selected for further testing with respect to heating values and heavy metal content. The surface area was low for all hydrochars, indicating that porous structure was not developed during treatment. The hydrochar obtained at 300 • C and 6 h residence times showed a predicted higher heating value of 17.8 MJ kg −1 , a fixed carbon content of 46.5 % and a fixed carbon recovery of 113 %, indicating a promising behaviour as a fuel.

An inactive asbestos mine in Northern Greece, known as MABE, had been operational for 18 years, s... more An inactive asbestos mine in Northern Greece, known as MABE, had been operational for 18 years, showing an annual chrysotile production of ∼100,000 tons. It is estimated that a total of 68 million tons of the mineral serpentine were excavated from the mine, of which 881,000 tons of chrysotile asbestos were produced. The mine deposits are located very near to the river Aliakmonas. The water of the river is extensively used as drinking water, as well as for irrigation. This study estimated the amount of asbestos currently present in the deposits, to at least 1.33 million tons. This is a 10-fold increase since the start of mine operation in 1982. Water samples obtained throughout the river had high chrysotile concentrations, in most cases far exceeding EPA's standard value (7 × 10 6 f/l). Therefore, the mine and the deposits urgently require remediation works, such as removal of large contaminated objects from the mine buildings and revegetation of the deposit areas, in order to reduce the asbestos levels in the river water.

Biochar produced by pyrolysis of organic residues is increasingly used for soil amendment and man... more Biochar produced by pyrolysis of organic residues is increasingly used for soil amendment and many other
applications. However, analytical methods for its physical and chemical characterization are yet far from being specifically
adapted, optimized, and standardized. Therefore, COST Action TD1107 conducted an interlaboratory comparison in which 22
laboratories from 12 countries analyzed three different types of biochar for 38 physical−chemical parameters (macro- and
microelements, heavy metals, polycyclic aromatic hydrocarbons, pH, electrical conductivity, and specific surface area) with their
preferential methods. The data were evaluated in detail using professional interlaboratory testing software. Whereas
intralaboratory repeatability was generally good or at least acceptable, interlaboratory reproducibility was mostly not (20% <
mean reproducibility standard deviation < 460%). This paper contributes to better comparability of biochar data published
already and provides recommendations to improve and harmonize specific methods for biochar analysis in the future.

The solid waste residues from olive oil mills constitute an environmental threat if disposed of i... more The solid waste residues from olive oil mills constitute an environmental threat if disposed of in the natural environment, as it is common practice in many areas. This review summarizes the efforts of the scientific and technical community to develop appropriate technologies for the valorization of these wastes. The majority of the research towards this purpose focuses on the recovery of high-added value compounds, the production of adsorbents, the production of compost or soil amendment products, and applications related to energy generation either through biotechnological processes or through advanced thermal processes.

An explosion occurs when a large amount of energy is suddenly released. This energy may come from... more 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.

Journal of Applied Electrochemistry, 2010

Electrochemical oxidation of an azo dye (Reactive Red 120) was studied in acidic media (1 M HClO ... more Electrochemical oxidation of an azo dye (Reactive Red 120) was studied in acidic media (1 M HClO 4 ) using DSA type (Ti/IrO 2 -RuO 2 ) and boron doped diamond (BDD) anodes. Ti/IrO 2 -RuO 2 exhibited low oxidation power with high selectivity to organic intermediates and low TOC removal (10% at 25°C and 40% at 80°C). On the other hand BDD was found to be suitable for total mineralization of the organic loading to CO 2 . In both cases, the decoloration of the solution was almost 100% achieved very quickly with BDD (2 Ah L -1 ) but only after long treatment with Ti/IrO 2 -RuO 2 (25 Ah L -1 ). The instantaneous current efficiency (ICE) was up to 0.13 in the case of Ti/IrO 2 -RuO 2 and up to 0.45 in the case of BDD.

This work investigated the production of Ca and Fe modified biochars in order to use them for the... more This work investigated the production of Ca and Fe modified biochars in order to use them for the removal of arsenic As(V) and chromium Cr(VI) from aqueous solutions. Rice husk was impregnated with CaO at an impregnation ratio 0.114, while both rice husk and the organic fraction of municipal solid wastes were impregnated with Fe 0 and Fe 3þ at impregnation ratios 0.114 and 0.23. The modified biochars exhibited high As(V) removal capacity (>95%), except for the case of rice husk impregnated with Fe 0 , whose removal capacity reached only 58%. All modified biochars exhibited much better As(V) removal capacity compared to the non-impregnated biochars. However, the Cr(VI) removal rates were not as high as the As(V) ones. The maximum Cr(VI) removal was observed in the case of rice husk biochar impregnated with 2.3% w/w Fe 3þ , whereas the majority of impregnation agents examined did not manage to enhance the biochars' Cr(VI) removal ability. The equilibrium study showed that the Freundlich model can adequately describe the sorption process for the majority of samples examined. Analysis of the amount of Fe present in the equilibrium solutions suggested that the main mechanisms of As(V) and Cr(VI) removal were possibly metal precipitation and electrostatic interactions between the modified biochars and the adsorbate.

Journal of Environmental Management, 2012

In this study, the adsorption of Cu(II) from aqueous solutions by agricultural by-products, such ... more In this study, the adsorption of Cu(II) from aqueous solutions by agricultural by-products, such as rice husks, olive pomace and orange waste, as well as compost, was evaluated. The aim was to obtain sorbent materials (biochars) through hydrothermal treatment (300 C) and pyrolysis (300 C and 600 C). The effect of adsorbent dose, pH, contact time and initial Cu(II) concentration in batch-mode experiments was investigated. The optimum Cu(II) adsorption conditions was found to occur at 5e12 g/L adsorbent dose, initial pH 5e6, and reaction time 2e4 h. Furthermore, the adsorption kinetics were best described by the pseudo-second order model for all the tested materials, while the adsorption equilibrium best fitted by the linear and Freundlich isotherms. Comparing rice husks and olive pomace, the higher adsorption capacity resulted after pyrolysis at 300 C. With respect to the orange waste and compost, the highest adsorption capacity was observed using biochars obtained after hydrothermal treatment and pyrolysis at 300 C.

Sewage sludge was pyrolyzed in order to assess the effect of pyrolysis temperature, residence tim... more Sewage sludge was pyrolyzed in order to assess the effect of pyrolysis temperature, residence time and biomass chemical impregnation on the yield of biochar production. The pyrolysis temperature was a key factor affecting biochar yield, while the highest yield was obtained at a temperature of 300 • C. Biochar surface area increased with increasing pyrolysis temperature and was maximized (90 m 2 /g) by impregnating biochar with K 2 CO 3 . Raw sewage sludge, as well as biochar samples, were subjected to leaching tests in order to investigate the potential release of heavy metals. Pyrolysis suppressed heavy metal release for the non-impregnated biochars, indicating that there is no environmental risk using sludgederived biochars as soil amendments. Although K 2 CO 3 and H 3 PO 4 impregnation enhanced the solubility of specific heavy metals, the concentrations in the leachates were low. Biochar impregnated with K 2 CO 3 released 85.7% of its potassium content, whereas orthophosphates were bound strongly in the biochar matrix impregnated with H 3 PO 4 . The non impregnated biochar was subjected to batch kinetic experiments in order to examine its ability to adsorb As(V) and Cr(III). Biochar removed approximately 70% of Cr(III) at equilibrium time, whereas only 30% of As(V) was adsorbed onto biochar surface, implying that biochar is more efficient in removing cations than anions from aqueous solutions. (E. Diamadopoulos).

International Journal of Environmental Science and Technology, Dec 25, 2023

The objectives of this study were to evaluate sewage sludge's stabilization with untested until n... more The objectives of this study were to evaluate sewage sludge's stabilization with untested until now materials, such as selective clay minerals or biochar in comparison with liming, for enhancing sludge's fertilization capacity. Dewatered sewage sludge was mixed with bentonite, vermiculite, zeolite, biochar or lime at rates of 0, 15 and 30%, air-dried and analyzed for pathogens and chemical properties. Almost all fecal indicators of treated sludge with 15% bentonite, vermiculite or biochar were reduced by at least one-logarithmic unit (log 10) (indicative value of sludge's stabilization), whereas those of limed sludge were undetectable. Electrical conductivity of all treatments significantly increased, and the highest values were obtained for untreated (6.1 dS m −1) and limed sludge (above 7.0 dS m −1 for both addition rates). The untreated sludge had the significantly highest water-soluble ammonium-nitrogen (2817 mg kg −1) and phosphorus (263 mg kg −1) concentrations followed by sludge treated with bentonite, vermiculite or biochar, whereas limed sludge had the lowest content. Boron concentration of the untreated sludge was similar to the treated sludge. Total concentrations of heavy metals were far below the legislative permissible levels for sludge's agronomic use. Nutrients' total content of treated sludge ranged at levels of similar magnitude to the untreated sludge, except for certain cases where they were increased because of the materials' composition. Consequently, sewage sludge treated with 15% bentonite, vermiculite or biochar seems to be stabilized, retain bioavailable nitrogen and serve as a fertilizer of macro-and micronutrients. However, potential risks of agronomic use, i.e., soil salinization and boron phytotoxicity, should be considered.

Chemosphere, 2021

In a column set-up, Fe modified biochar produced from date palm leaves was used to remove As (1 m... more In a column set-up, Fe modified biochar produced from date palm leaves was used to remove As (1 mg L-1) from a laboratory-prepared wastewater. The wastewater treatment process was monitored in real-time by spectral induced polarization (SIP), over a wide range of frequencies (0.01-1000 Hz). Both 5 and 10% biochar-amended columns achieved As removal exceeding 98%. The SIP parameters appear to be sensitive on As removal processes, with the recorded trend following the conventional geochemical monitoring, while offering higher temporal resolution.

Journal of Environmental Management

A novel sulfur-rich adsorbent, poly(BA-ala-co-sulfur), was synthesized by reacting allyl function... more A novel sulfur-rich adsorbent, poly(BA-ala-co-sulfur), was synthesized by reacting allyl functional benzoxazine (BA-ala) and elemental sulfur. Simultaneous inverse vulcanization and ring-opening reactions of benzoxazine generated copolymers in several feed ratios. The adsorption behavior of these copolymers was investigated in aqueous solutions containing Hg 21 . A three level Box-Behnken design with four factors was applied in order to examine the interactive effect of Hg 21 concentration (ppm), S % in adsorbent, temperature, and pH. The optimum adsorption conditions were determined as: 10.33 ppm Hg 21 , 68% S content, 329 K, and pH 6.3. Common isotherm and kinetic models were applied to the experimental data, where the Langmuir isotherm provided the better fit (q max 5 79.36 mg g 21 ) and the pseudo-second order fit indicated chemisorption as the process-controlling step.

In this study, subcritical water has been used as a medium for degradation of 2,4-dinitrotoluene ... more In this study, subcritical water has been used as a medium for degradation of 2,4-dinitrotoluene (2,4-DNT), 4-nitrotoluene (4-NT) and 2-amino-4-nitrotoluene (2-A-4-NT). The effect of temperature, oxidant concentration and time were studied and the optimal combination of reaction parameters was established using response surface methodology in a Box-Behnken design. Of all the parameters examined, temperature showed the most positive effect on the degradation of the nitroaromatic compounds. Optimal reaction conditions were found to be a temperature of 240°C, 210°C and 236°C, time of 180, 178 and 172 min, oxidant concentration of 100, 99.64 and 99.61 mM for 2,4-DNT, 4-NT and 2-A-4-NT, respectively. Since high-temperature was applied, the possibility of formation of subcritical degradation products existed; therefore, total amounts of degraded nitroaromatic compounds and formed intermediate products were determined by gas chromatographic-mass spectrometric analysis.

А г р о ф и з и к а 2015 № 4 1 Физика, биофизика и экология почв УДК 57.033; 631.95 ВЛИЯНИЕ РАЗЛИ... more А г р о ф и з и к а 2015 № 4 1 Физика, биофизика и экология почв УДК 57.033; 631.95 ВЛИЯНИЕ РАЗЛИЧНЫХ ВИДОВ ГИДРОУГЛЯ НА ЭМИССИЮ УГЛЕКИСЛОГО ГАЗА, ЗАКИСИ АЗОТА И РОСТ РАСТЕНИЙ Поступила в редакцию 11 сентября 2015 г., принята к печати 08 декабря 2015 г.

TiO 2 -biochar (TiO 2 -BC) nanocomposite was synthesized by sol-gel method. The characteristics o... more TiO 2 -biochar (TiO 2 -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 N 2 adsorption-desorption analysis. The performance of synthesized TiO 2 -BC nanocomposite as efficient sonocatalyst was studied for the degradation of Reactive Blue 69 (RB69). Sonocatalytic degradation of RB69 in the presence of TiO 2 -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, TiO 2 -BC dosage of 1.5 g/L, RB69 initial concentration of 20 mg/L and ultrasonic power of 300 W. Furthermore, the effect of % OH, h + and O 2 %− 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 TiO 2 -BC in the sonocatalytic process verified its stability in long-term usage.

Journal of Agricultural and Food Chemistry, 2015

Biochar produced by pyrolysis of organic residues is increasingly used for soil amendment and man... more Biochar produced by pyrolysis of organic residues is increasingly used for soil amendment and many other applications. However, analytical methods for its physical and chemical characterization are yet far from being specifically adapted, optimized, and standardized. Therefore, the COST Action TD1107 conducted an inter-laboratory comparison, in which 22 laboratories from twelve countries analyzed three different types of biochar for 38 physical-chemical parameters (macro- and micro-elements, heavy metals, polycyclic aromatic hydrocarbons, pH, electrical conductivity, and specific surface area) with their preferential methods. The data was evaluated in detail using professional inter-laboratory testing software. Whereas intra-laboratory repeatability was generally good or at least acceptable, inter-laboratory reproducibility was mostly not (20% &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; mean reproducibility standard deviation &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 460%). This paper contributes to better comparability of biochar data published already, and provides recommendations to improve and harmonize specific methods for biochar analysis in the future.

Journal of Agricultural and Food Chemistry, 2015

Biochar produced by pyrolysis of organic residues is increasingly used for soil amendment and man... more Biochar produced by pyrolysis of organic residues is increasingly used for soil amendment and many other applications. However, analytical methods for its physical and chemical characterization are yet far from being specifically adapted, optimized, and standardized. Therefore, the COST Action TD1107 conducted an inter-laboratory comparison, in which 22 laboratories from twelve countries analyzed three different types of biochar for 38 physical-chemical parameters (macro- and micro-elements, heavy metals, polycyclic aromatic hydrocarbons, pH, electrical conductivity, and specific surface area) with their preferential methods. The data was evaluated in detail using professional inter-laboratory testing software. Whereas intra-laboratory repeatability was generally good or at least acceptable, inter-laboratory reproducibility was mostly not (20% &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; mean reproducibility standard deviation &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 460%). This paper contributes to better comparability of biochar data published already, and provides recommendations to improve and harmonize specific methods for biochar analysis in the future.

Currently, char substrates gain a lot of interest since soils amended with such substrates are be... more Currently, char substrates gain a lot of interest since soils amended with such substrates are being discussed to increase in fertility and productivity, water retention, and mit-igation of greenhouse gases. Char substrates can be produced by carbonization of organic matter. Among different process conditions, temperature is the main factor controlling the occurrence of organic and inorganic contaminants such as phenols and furfurals, which may affect target and non-target organisms. The hydrochar produced at 200 °C contained both furfural and phenol with concentrations of 282 and 324 mg kg −1 in contrast to the 300 °C hydrochar, which contained only phenol with a concentration of 666 mg kg −1. By washing with acetone and water, these concentrations were significantly reduced. In this study, the potential toxic effects of hydrochars on the free-living nematode Caenorhabditis elegans were investigated via gene transcription studies using the following four matrices: (i) raw rice husk, (ii) unwashed rice char, (iii) acetone/water washed rice char, and (iv) the wash water of the two rice chars produced at 200 and 300 °C via hydrothermal carbonization (HTC). Furthermore, genetically modified strains, where the green fluorescent protein (GFP) gene sequence is linked to a reporter gene central in specific anti-stress regulations, were also exposed to these matrices. Transgenic worms exposed to hydrochars showed very weak, if any, fluorescence, and expression of the associated RNAs related to stress response and biotransformation genes was surprisingly downregulated. Similar patterns were also found for the raw rice husk. It is hypothesized that an unidentified chemical trigger exists in the rice husk, which is not destroyed during the HTC process. Therefore, the use of GFP transgenic nematode strains cannot be recommended as a general rapid monitoring tool for farmers treating their fields with artificial char. However, it is hypothesized that the observed reduced transcriptional response with the subsequent lack of energy-consuming stress response is an energy-saving mechanism in the exposed nematodes. If this holds true in future studies, this finding opens the window to an innovative new field of stress ecology.

Biochar is the carbon-rich product obtained when biomass, such as wood, manure or leaves, is heat... more Biochar is the carbon-rich product obtained when biomass, such as wood, manure or leaves, is heated in a closed container with little or no available air. In more technical terms, biochar is produced by so-called thermal decomposition of organic material under limited supply of oxygen (O 2), and at relatively low temperatures (< 700 • C). Hy-drochar differentiates from biochar because it is produced in an aqueous environment, at lower temperatures and longer retention times. This work describes the production of hy-drochar from rice husks using a simple, safe and environmentally friendly experimental setup , previously used for degradation of various wastewaters. Hydrochars were obtained at 200 • C and 300 • C and at residence times ranging from 2 to 16 h. All samples were then characterized in terms of yield, surface area, pH, conductivity and elemental analysis , and two of them were selected for further testing with respect to heating values and heavy metal content. The surface area was low for all hydrochars, indicating that porous structure was not developed during treatment. The hydrochar obtained at 300 • C and 6 h residence times showed a predicted higher heating value of 17.8 MJ kg −1 , a fixed carbon content of 46.5 % and a fixed carbon recovery of 113 %, indicating a promising behaviour as a fuel.

An inactive asbestos mine in Northern Greece, known as MABE, had been operational for 18 years, s... more An inactive asbestos mine in Northern Greece, known as MABE, had been operational for 18 years, showing an annual chrysotile production of ∼100,000 tons. It is estimated that a total of 68 million tons of the mineral serpentine were excavated from the mine, of which 881,000 tons of chrysotile asbestos were produced. The mine deposits are located very near to the river Aliakmonas. The water of the river is extensively used as drinking water, as well as for irrigation. This study estimated the amount of asbestos currently present in the deposits, to at least 1.33 million tons. This is a 10-fold increase since the start of mine operation in 1982. Water samples obtained throughout the river had high chrysotile concentrations, in most cases far exceeding EPA's standard value (7 × 10 6 f/l). Therefore, the mine and the deposits urgently require remediation works, such as removal of large contaminated objects from the mine buildings and revegetation of the deposit areas, in order to reduce the asbestos levels in the river water.

Biochar produced by pyrolysis of organic residues is increasingly used for soil amendment and man... more Biochar produced by pyrolysis of organic residues is increasingly used for soil amendment and many other
applications. However, analytical methods for its physical and chemical characterization are yet far from being specifically
adapted, optimized, and standardized. Therefore, COST Action TD1107 conducted an interlaboratory comparison in which 22
laboratories from 12 countries analyzed three different types of biochar for 38 physical−chemical parameters (macro- and
microelements, heavy metals, polycyclic aromatic hydrocarbons, pH, electrical conductivity, and specific surface area) with their
preferential methods. The data were evaluated in detail using professional interlaboratory testing software. Whereas
intralaboratory repeatability was generally good or at least acceptable, interlaboratory reproducibility was mostly not (20% <
mean reproducibility standard deviation < 460%). This paper contributes to better comparability of biochar data published
already and provides recommendations to improve and harmonize specific methods for biochar analysis in the future.

The solid waste residues from olive oil mills constitute an environmental threat if disposed of i... more The solid waste residues from olive oil mills constitute an environmental threat if disposed of in the natural environment, as it is common practice in many areas. This review summarizes the efforts of the scientific and technical community to develop appropriate technologies for the valorization of these wastes. The majority of the research towards this purpose focuses on the recovery of high-added value compounds, the production of adsorbents, the production of compost or soil amendment products, and applications related to energy generation either through biotechnological processes or through advanced thermal processes.

An explosion occurs when a large amount of energy is suddenly released. This energy may come from... more 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.

Journal of Applied Electrochemistry, 2010

Electrochemical oxidation of an azo dye (Reactive Red 120) was studied in acidic media (1 M HClO ... more Electrochemical oxidation of an azo dye (Reactive Red 120) was studied in acidic media (1 M HClO 4 ) using DSA type (Ti/IrO 2 -RuO 2 ) and boron doped diamond (BDD) anodes. Ti/IrO 2 -RuO 2 exhibited low oxidation power with high selectivity to organic intermediates and low TOC removal (10% at 25°C and 40% at 80°C). On the other hand BDD was found to be suitable for total mineralization of the organic loading to CO 2 . In both cases, the decoloration of the solution was almost 100% achieved very quickly with BDD (2 Ah L -1 ) but only after long treatment with Ti/IrO 2 -RuO 2 (25 Ah L -1 ). The instantaneous current efficiency (ICE) was up to 0.13 in the case of Ti/IrO 2 -RuO 2 and up to 0.45 in the case of BDD.

This work investigated the production of Ca and Fe modified biochars in order to use them for the... more This work investigated the production of Ca and Fe modified biochars in order to use them for the removal of arsenic As(V) and chromium Cr(VI) from aqueous solutions. Rice husk was impregnated with CaO at an impregnation ratio 0.114, while both rice husk and the organic fraction of municipal solid wastes were impregnated with Fe 0 and Fe 3þ at impregnation ratios 0.114 and 0.23. The modified biochars exhibited high As(V) removal capacity (>95%), except for the case of rice husk impregnated with Fe 0 , whose removal capacity reached only 58%. All modified biochars exhibited much better As(V) removal capacity compared to the non-impregnated biochars. However, the Cr(VI) removal rates were not as high as the As(V) ones. The maximum Cr(VI) removal was observed in the case of rice husk biochar impregnated with 2.3% w/w Fe 3þ , whereas the majority of impregnation agents examined did not manage to enhance the biochars' Cr(VI) removal ability. The equilibrium study showed that the Freundlich model can adequately describe the sorption process for the majority of samples examined. Analysis of the amount of Fe present in the equilibrium solutions suggested that the main mechanisms of As(V) and Cr(VI) removal were possibly metal precipitation and electrostatic interactions between the modified biochars and the adsorbate.

Journal of Environmental Management, 2012

In this study, the adsorption of Cu(II) from aqueous solutions by agricultural by-products, such ... more In this study, the adsorption of Cu(II) from aqueous solutions by agricultural by-products, such as rice husks, olive pomace and orange waste, as well as compost, was evaluated. The aim was to obtain sorbent materials (biochars) through hydrothermal treatment (300 C) and pyrolysis (300 C and 600 C). The effect of adsorbent dose, pH, contact time and initial Cu(II) concentration in batch-mode experiments was investigated. The optimum Cu(II) adsorption conditions was found to occur at 5e12 g/L adsorbent dose, initial pH 5e6, and reaction time 2e4 h. Furthermore, the adsorption kinetics were best described by the pseudo-second order model for all the tested materials, while the adsorption equilibrium best fitted by the linear and Freundlich isotherms. Comparing rice husks and olive pomace, the higher adsorption capacity resulted after pyrolysis at 300 C. With respect to the orange waste and compost, the highest adsorption capacity was observed using biochars obtained after hydrothermal treatment and pyrolysis at 300 C.

Sewage sludge was pyrolyzed in order to assess the effect of pyrolysis temperature, residence tim... more Sewage sludge was pyrolyzed in order to assess the effect of pyrolysis temperature, residence time and biomass chemical impregnation on the yield of biochar production. The pyrolysis temperature was a key factor affecting biochar yield, while the highest yield was obtained at a temperature of 300 • C. Biochar surface area increased with increasing pyrolysis temperature and was maximized (90 m 2 /g) by impregnating biochar with K 2 CO 3 . Raw sewage sludge, as well as biochar samples, were subjected to leaching tests in order to investigate the potential release of heavy metals. Pyrolysis suppressed heavy metal release for the non-impregnated biochars, indicating that there is no environmental risk using sludgederived biochars as soil amendments. Although K 2 CO 3 and H 3 PO 4 impregnation enhanced the solubility of specific heavy metals, the concentrations in the leachates were low. Biochar impregnated with K 2 CO 3 released 85.7% of its potassium content, whereas orthophosphates were bound strongly in the biochar matrix impregnated with H 3 PO 4 . The non impregnated biochar was subjected to batch kinetic experiments in order to examine its ability to adsorb As(V) and Cr(III). Biochar removed approximately 70% of Cr(III) at equilibrium time, whereas only 30% of As(V) was adsorbed onto biochar surface, implying that biochar is more efficient in removing cations than anions from aqueous solutions. (E. Diamadopoulos).